Fiberglass Clinic

7/25/2019 Fiberglass Clinic

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Contents

-Cosmetic Repairs 2

-Structural repairs Repairing a Delaminated Hull 6

Hinging & Cracking 10 Step-by-Step Crack Repairs 13 Crack Analysis 15 Delamination: Failures, Repairs & Prevention 16

Understanding Dry Delamination 20 Replacing Foam Flotation 21

-Deck Repairs Repairing Non-Skid 23

Replacing a Soggy Deck 26

-Transom Repairs 30

-Resin Repair Substitutes 32

-Hardware Installations Bedding Hardware in Cored Decks 33

Potting Techniques 34 Installations in Cored Laminates 35

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Fiberglass Cosmetic RepairsIts easy to repair cracks, gouges, nicks, small holes and non-skidyourself. Just follow these easy steps for professional results every tim

By Wayne Redditt and Jan Mundy

TOOLS

Dust masks andrespirator

Safety glassesLatex glovesDisposable mixing

containers (paperor plastic)

Mixing sheetsStir sticksMasking tapeGlue brushesSqueegeePreval sprayerRagsPutty knives (flexible)

Utility knifeSanding blocksWet/dry sandpaper,

320 to 600 gritRotary bit (carbide,

non-ferrous, non-plastic cutting bitwith big flutes)

HacksawMetal fileChiselPower buffer with

foam buff pad

Materials

Gelcoat resinPolyester pigmentsPolyester or vinylester

resin and hardenerChop-strand matFillersSolvent (acetone or

lacquer thinner)Buffing compoundMold release (PVA or

wax)

Cosmetic fiberglass repairs can be easilyaccomplished with a little know-how,inexpensive tools and supplies purchasedfrom chandleries or specialty fiberglasssuppliers.

Its important to note the distinctionbetween cosmetic and structural repairs.Cosmetic repairs, such as minor scratches,shallow nicks, star crazing, gouges, smalldrilled holes and non-skid, are done for the

sake of appearance. These generally do naffect the strength of the fiberglass laminatStructural repairs are spider cracks, punctubreaks and large holes that penetrate thelaminate, affecting the boats structuralintegrity. Such repairs are beyond the scoof this article.

Before attempting any of these repairsyou should be aware of the potential safeand health risks involved. Read allmanufacturers safety precautions outlinedthe labels. Many of the chemicals are hightoxic, so the work area should be well-ventilated. Always wear gloves whenhandling gelcoat or resin, safety glasses o

goggles when grinding, and a dust maskwhen grinding, sanding and buffing. Whespraying gelcoat or mold release, always a respirator with the proper filter.

When doing any of these repairs,carefully follow the manufacturers instructand the directions for mixing and applicaof gelcoat, resins and other repair materia

Surveying the DamageClean the surface with detergent and freshwater, then clean the repair area with solv

Inspect the repair to determine the extent othe damage. Where its accessible, checkunderside of the laminate. Ensure thatstructural damage has not occurred.

Spider cracking and corner cracks arealmost always related to a structural problcaused by flexing. The telltale webs on t

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surface (Figure 1) often extend into thelaminate. The extent of the damage onlybecomes clearly visible after grinding throughthe gelcoat. Whitish cracks or discolorationradiating outwards, as shown in Figure 2,indicate a damaged laminate. Repair involvesgrinding the laminate to remove alldelaminated glass, filling with putty andstiffening the structure to resist flexing. If thedamaged laminate is not repaired, cracking

will recur in the gelcoat.

Repairing Gouges &Holes

When a scratch or gouge is very shallow anddoesnt break through the gelcoat into thelaminate beneath, its best to simply wet sandwith 400- to 600-grit abrasive and buff with arubbing compound or polish. There may be aslight depression created (do not sandthrough into the laminate), but it will be lessnoticeable than a filled repair thats not

perfectly color-matched. A deeper scratch orgouge (Figure 3) that goes into thelaminate, but doesnt delaminate it, requires adifferent approach.

STEP 1

Bevel the edge of the repair using a drill with arotary or chamfering bit, or use a utility knife tocontour the edges. Remove all loose anddamaged gelcoat without enlarging the size ofthe repair area. Grind the gouge until youhave a uniform dark color in the underlyinglaminate.

Remove the dust out of the gouge, thenmask the area with a quality masking tape(3M is best). Tape close to the edge of the

repair but not inside the repair zone or youhave to refill. The thickness of the tape (abo.005) provides an accurate measuring gafor the finished height of the filler, allowingshrinkage, which is about 5%. Tip: Layer thmasking tape sequentially in a grid patternaround the repair. To remove it, you pull thbottom layer and it all comes off together.

Use a clean rag and clean the gouge solvent. Do not use solvents around the rep

until its masked off completely. Gelcoat habeen waxed and if you smear the wax intorepair area it will cause bonding problems

STEP 2

Place a quantity of the correct putty filler(different types for above or below waterlin

repairs) on a plastic sheet or impregnatedpaper (available on pads from auto bodysuppliers). Dont mix on cardboard as itabsorbs the material, especially the hardenAdd the creme hardener. To ensure the corresin-to-hardener ratio, a good rule is to mione golf-ball size amount of putty to 2.54c(1) of creme hardener, regardless of the sof the repair. Use a pre-mixed quality filler,such as 3M Marine Premium Filler or MariFiller which are very fine, gritless, modified

vinylester compounds. Hardener is a differecolor (in this case blue), so mix until the coare well-blended. You cant overmix.

STEP 3Tightly pack the filler into the repair area,spreading with a putty knife to remove the abubbles. Remove the excess, leveling thesurface with a putty knife large enough to sthe tape so the filler is flush with the tapededge. If you fill the gouge only to the level othe gelcoat, when it cures, it shrinks, creatinhollow that must be refilled. Immediately

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remove the masking tape. The filler hardens in

20 minutes or so, depending on the amountand type of hardener used and the workingtemperature.

STEP 4

Grate the repair with a Surform (remove thehandle) while the filler is still green (not fullycured) so its flush with the gelcoat. Gelcoat isextremely hard so you wont scratch it. Let thefiller cure overnight. If the repair has anyhollows, youll have to refill them.

STEP 5

Prepare enough gelcoat to coat the repair. Mixa small quantity of neutral gel with your colorpigment on the mixing paper or use a plasticcontainer (yogurt containers are impervious tochemicals) for larger quantities. Use apremixed pigment thats color-matched to thegelcoat, otherwise youll have to mix a custombatch (see Color Matching above). For a fewsmall repairs, gelcoat repair kits (from Seacareand others) are easy to work with and lessexpensive than purchasing jars of polyesterpigment.

STEP 6For small repairs, put a quantity of gelcoat the upturned bottom of a plastic container aadd catalyst at a ratio of 2%. Dontovercatalyze or youll have a cooked edgthat forms a luminous circle around the edgWhen mixing larger quantities, use a smalsyringe to measure the exact amount ofcatalyst (see Non-Skid, Step 2). Mix well.

COLOR-MATCHING

Color-matching gelcoat is one of the mostdifficult repair procedures. Color is added togelcoat in the form of polyester pigments. Ifyoure fortunate, your boats gelcoat will examatch a standard color in one of the off-the-shpackaged gelcoat repair kits. If the color comclose but not quite perfect, then get ready for

some work.Begin by finding a smooth, flat, near-

vertical surface somewhere close to the repaiClean and buff the surrounding area. (Dontattempt to match color to a badly oxidizedsurface.)

To test the color of pigment required, daa small quantity of uncatalyzed gelcoat resinonto the buffed surface. (Uncatalyzed resin wnot harden and will not harm the surface ofyour boat.) Start with a gelcoat that is similarcolor to the final color that you are attempting

to match. For example, its better to start with white gelcoat and tint to off-white, than topigment neutral gelcoat, which allows you tochange the resin to any color. Add enoughpigment but no more than 10% or youll haveover-pigmented resin, causing a loss of glossthat no buffing will restore. If you under-pigmeyour neutral gelcoat, the result is a translucenfinish.

Now, add a minute quantity of the pigmyou believe will shade the color to the desiredhue and mix thoroughly. Pigments are very

viscous and must be thoroughly mixed with thresin. Undermixing causes either a marble effor colored streaks in the gelcoat. If the colordoes not match, try to determine the methodrequired to make it right. Does it need black?White? Some yellow perhaps? There is noshortcut to doing this. Experimentation andpractice are the only way to master this skill.Keep a record of the amount of pigment addOnce youve mastered the color match in youtest area, youll need to duplicate it in a muchlarger quantity.

Wayne Redditt

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STEP 7

Mask the edge of the repair. Be sure not to

overlap the tape inside the repair or thegelcoat wont fully cover and youll have toreapply. Clean the repair area with solvent.Apply the gelcoat liberally with a putty knife,overlapping the tape. Remove the maskingtape.

STEP 8

Using 320-grit paper on a rubber sandingblock, wet sand the repair area. Place asqueegee over the repair and check for level. Itshould be perfectly flat. Any low spots requiremore gelcoat. Finish sanding with 400- then600-grit wet paper. Use lots of water. Resist

the temptation to sand with your fingers oryoull have ripples in the finished surface.

STEP 9

Finish the repair by buffing with a fine rubbcompound. Use a foam pad mounted on apower buffer and begin by putting compouon the surface, then manually swirl the buffaround to work the compound into the padYou can also buff with an angle sander bulow speed or youll burn the gelcoat.

STEP 10

Repairing drilled holes is similar, the onlydifference is you need to fill the hole. Beginbeveling the edge, using a drill with a cuttibit. Remove the dust and clean with solven

STEP 11

If accessible, cover the back of the repair w

masking tape. When its not, stuff a wad ofmasking tape into the hole (left) or insert a spiece of doweling (right) anything to prefiller from running out the hole and into theinterior. Continue, following Steps 2 and 3 page 12.

STEP 12Using a power drill with a rotary bit, grind the filler to about .020 below surface levethe thickness of the applied gelcoat. Fill witcolor-matched gelcoat following instructionSteps 5 and 6 on page 13, then proceedthrough to Step 9.

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Story and Photos by Paul and

Sheryl Shard

We watched with trepidation as the haul-outcrew positioned the slings under our home-built Classic 37 sailboat, Two-Step. Lifting theboat with a crane always made us nervous,but we were worried about the condition ofour fiberglass hull following a 20,000-nautical-mile voyage to countries around theAtlantic Ocean. Three years in warm tropicalseas can take their toll.

Fiberglass hulls are renowned for theirhigh strength and durability; however,fiberglass is susceptible to osmosis blisteringand, if left unchecked, can cause structuraldamage and hull delamination. To preventosmosis from happening to our boat, we hadcoated the bottom with six protective layers ofInterprotect 2000, an epoxy barrier coating.

Now back in our home port of PortCredit, Ont., the foreman gave the handsignal and Two-Stepbegan to rise out of thewater. We had hauled out briefly in Gibraltarthe previous year to redo the bottom paintafter our transatlantic passage to Europe and had been pleased with the condition of

the hull at that time.When we decided to build a boat in

1985, we both agreed to start from a barhull rather than build the hull ourselves. W

knew the limitations of our skills (andenthusiasm) and felt it prudent to trust this to a professional. We found a smallindependent builder with the molds for theSparkman & Stevens designed Classic 37and, with good references, had him and hcrew set to work. We took delivery of the

in the summer of 1986.It was the only part of the

boat we did not build ourselveWe did everything else thoug

right from smelting the lead fothe internal keel to doing theinterior and exterior woodwoelectricity and plumbing, riggand countless other jobs requin building a boat. When wefinished, we had accumulatedmore than 6,000 hours of labbetween the two of us during three-year process.

As Two-Stepwas lifte

out of the water we saw, withrelief, only a few barnaclesclinging to the prop and a fewbare spots on the bottom of thkeel where the 1.8m (6) drafhad found unmark-ed shoals.Otherwise, the boat was in grcondition or so we firstthought.

Mistaken Identity

Then something very strange happened.

During the next few days, as we cleaned aunloaded the boat in the yard, we noticedfew deep blisters in the gelcoat, about thesize of a quarter, so we marked them anddrilled them out to dry. But as the days weby, more blisters began to appear. Theblisters actually seemed to be growing anspreading!

We continued to mark and drill out neblisters daily. They were all the same size discharged a sour-smelling ooze about the

consistency of honey. Within a week, ourbeloved boat had a serious case of the p

Repairing a Delaminated HullFaulty construction causes the fiberglass laminate to

separate and peel off the hull in sheets.

The outer layer of fiberglass peeled off the hull in huge sheets like peeling a banana!

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Mystified, we sadly left the boat to dry outover the winter.

In the spring, things got worse. We wereback at the boatyard and Paul was preparing

to fill Two-Steps blisters while I did somerefinishing in the galley. I could hear himtapping at the hull as I worked. Then I hearda noise that I will never forget. A sound likefingernails on a blackboard. A scraping,withering rrrrrrrrrrrip of fiberglass. I raceddown the ladder and found Paul leaningagainst the cradle with a piece of our hull inhis hand.

Our boats falling apart, he said.He had dug the edge of a chisel into a

large blister and discovered that the outerlayer of fiberglass would peel right off. Wewere stumped. Our problem did not have thesymptoms of a typical osmosis ordelamination problem. We needed expertadvice.

We called our friend Wally Dzuryk,former project manager of CS Yachts. Hetook one look at our peeling hull, checked thesubstrate and tapped the hull all over. Heknew immediately what the problem was.

Your hull isnt delaminating, he said. It

was never correctly laminated in the firstplace.Wally explained that it is common

practice for builders to prepare hull molds forthe next boat by coating them with gelcoat,then spraying on a thin layer of choppedfiberglass strands mixed with resin. Althoughthis saves time for the builder, when the hull isleft for more than two or three days thesurface must be cleaned and ground toremove the wax that was added to the resinto promote curing, or subsequent layers ofglass will not bond properly to the outer layer.

Boats with blisters under the gelcoat blisters caused by voids deeper in thelaminate are easily repaired by grinding blisters out and filling them with an epoxycoating. Where blisters are caused byinferior laminating techniques, however,repairing the visible blisters still leaves vobetween the outer layer and the hull, caunew blisters to appear every year. As thelayers were never correctly bonded, we

suspect it was the Interprotect coating thablocked the water from getting into the vosooner.

After a thorough survey, Wally assurus that the underlying hull was strong andsound. There were only a few voids in thetopsides and we could inject those with epto re-bond. We were relieved; we knew thwe had to strip and relaminate the topsidewe could never fair them to our satisfactio

Under Wallys direction, we strippedaway the fiberglass laminate from thewaterline down to the keel and laid in founew layers of fiberglass mat and roving. Nwe faired the bottom and reappliedInterprotect epoxy barrier coat andantifouling.

Make-Ready

The first job was to build a shelter around boat to keep the hull dry. We made a simstructure of 2x2s covered with a clear plastarp. For added protection, we ran a rain

gutter made of folded electrical tape arouthe hull above the waterline to prevent anywater running down the topsides fromtraveling down the exposed hull below thewaterline. We supported the boat with 4xwood beams bolted to the toe rail and vaother props at the stern and bow, so the ebottom would be accessible without havinthe cradle pads in the way.

Then we began stripping away the ollaminate. This was much easier than we

After pressure washing the hull with fresh water,blister cavities were filled with a mixture of

microballoons, Cabosil and polyester resin.

Mat and roving were precut and labeled so tcould be applied without stopping.

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thought it would be, which demonstrated howpoorly this layer was originally laminated.With a sanding disk on a grinder, Paulcarefully ground to the depth of the outerlayer of laminate all around the waterline.Then we peeled away the outer layer offiberglass down to the keel. Sometimes it tore

away in 1.8m-long (6) strips. The hull wassurprisingly smooth underneath. The Airexclosed-cell foam core, visible through the nextfew layers of fiberglass, was well sealed.Airex is impermeable to water and addsstrength, stiffness, impact strength and soundand thermal insulation that preventscondensation in the boats interior and kept uscool in the tropics.

Dark gooey patches showed where

moisture had collected in the voids, mixed

with resin and left glycol, a by-product ofpolyester resins that, unlike water, does not

evaporate. We pressure washed with clean

water before attempting to sand and fair the

hull and left it to dry.To prepare the exposed hull for

reglassing, we used a small grinder and 36-grit disks to smooth the hull and create atooth for the new laminate. A light touch isimportant here to avoid cutting crescents inthe glass. Then we washed with acetone andclean rags to remove any last traces of wax.Finally, we filled any dips and crevices with a

putty of resin, microballoons anjust enough Cabosil to thicken thmixture too much Cabosil anwould be too hard and impossito sand. When we were satisfiewith the fairing job, we measurethe hull into sections the width opiece of fiberglass mat and labeand marked each with awaterproof marker. Then we

premeasured and cut the mat anroving into lengths.

Six-Layer Wrapper

On Wallys recommendation whad decided to use polyester reinstead of epoxy. Its less toxic thandle, much cheaper than epoand forms a reasonable mechanbond to the existing fiberglass.

Epoxy would have provided astronger bond but would haveadded more than $1,000 to theOf course, we would still apply epoxy barrier coat over the newfiberglass.

Now we had to wait for good weathewe needed two consecutive dry days. Wetaped the waterline to give a clean edge. new laminate would stand proud by 15m(1/16), but would be masked by the boostripe.

The first day, we applied a layer of 1oz chopped strand mat as a base. It took of us to do the job two to position and the mat, one to hold the mat against the hone to mix the resin and another to wet-outhe glass with rollers. We had to work quibefore the resin hardened, keeping less tha gallon in the paint tray while being carenot to mix more than we could use in 15minutes or less. We used a paint-mixerattachment on a drill to stir the mixture. Sowe worked out an assembly line system of

pre-wetting the hull, positioning the mat,wetting the mat, mixing more resin, and oand on.

The next day, we hand-sanded the boand washed it with acetone. Then we appanother 1.5-oz mat followed by 18-oz rovand a final 1.5-oz mat. Adding one layer the entire hull took about one and a halfhours. We waited nearly another hour foreach layer to partially cure before applyinthe next layer. Applying consecutive layer

green on green forms one chemical bonbetween the layers that is much stronger th

The hull was divided into sections and labeled with awaterproof marker in preparation for applying the newlaminate. The lighter area below the waterline is the

Airex core which remained intact.

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four individual layers.When the final layer had fully

cured, we sanded high spots andbegan fairing using a similar mix ofmicroballoons, Cabosil and resin,and an old saw blade as a puttyknife, to follow the contours of thehull. We enlisted Wallys helpagain with the final fairing aroundthe waterline and his professionaleye gave us an arrow-straight bootstripe. Finally, we washed thebottom with acetone one more timeand applied the Interprotect 1000and 2000 epoxy barrier coating asper the instructions, followed byantifouling. With the help of friendsand family, it had taken 11 days tocomplete the job.

The hull repair was a massivejob but, as all do-it-yourselfers

know, the satisfaction and feeling ofcontrol you get from tackling a bigproblem can make even such alarge job well worth the effort. Nowwe know our own hull and feelmore confident than ever as Two-Stepcuts through the waves. Shehas been back to the Bahamastwice since we made this repairand remains blister-free.

Paul and Sheryl Shard spent three

years sailing to 23 countries around theAtlantic Ocean in a Classic 37 sailboat

DIY REPAIR BILL

The following is the approximate cost for repairing a 1(37) sailboat from the waterline down to the keel. Pricevary depending on the products used and amount of palabor. Its a good idea to enlist someone with professioboatbuilding experience as supervisor of your team. If y

havent done much fiberglass work, check with aprofessional yard for an estimate. We got rough estimaaround $10,000. This works out to almost $300 per fo(LOA). Estimates for DIYers run from $50 to $100 per fdepending on how much help you enlist.

Temporary shelter (lumber, plastic, staples) $104x4 legs to support hull $5Acetone $5Cabosil, microballoons $5Polyester resin (20 gallons) $36

Fiberglass mat and roving $38Interprotect 1000 and 2000 (6 coats) $42Antifouling paint (2 coats) $40Rollers, sandpaper, grinding

discs, brushes, solvent$ 10

TOTAL: $191

Laminating the four layers was arduous overhead work and it took five crew to d

the job.

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Pages 2 to 5 reviewed the steps and techniquesto do professional fiberglass cosmetic repairs. Inthis special section, DIY details structural defects hinging, cracking and delaminating in fiber-reinforced plastic hulls and decks: how to identifycritical failures; execute repairs to damaged hullsand decks, and provide key preventive remedies.

Whether you are making it a do-it-yourself repairor hiring a professional, this knowledge will helpyou make informed decisions that can add years tothe life of your boat and dollars to its trade-invalue. JM

By Nick Bailey

Some years ago, our clubs mark boat, anew 6.4m (21') center console runaboutwith a foam-filled double bottom, almost

sank before the frantic operator was able to

beach it. Just below the waterline forward, thebottom had split open athwartship and waterpressure had torn the hull neatly along thecenter strake. This left a large panel offiberglass flapping loose and exposed thefoam-filled hull. The boat was a write-off.Apparently the builder, by then defunct, in aclassic case of under-engineering, had skimpedon the outer skin laminates and used flotationfoam of inadequate density and strength. Theusual pounding a powerboat hull receivesgradually crushed the foam. This allowed the

too thin fiberglass skin to flex until it cracked,the lip snagged the high-speed water flowingpast the hull and suddenly ripped open. Thissort of dramatic failure is rare in fiber-reinforced plastic (FRP) boats, but unfortunatelycracked and leaking hulls are not, especially inpowerboats with high-hours or older sailboats.

Flex-Related Hinging

In flex-related powerboat hull failures, initialstress cracks usually appear at or adjacent towhere panel flex is restrained or limited by

eitherinternal structural members (i.e. bulkheads ostringers) and chines, running strakes or othexternal sharp corners (Figure 1). Thisconcentration of flexing stress at a hard poior corner radius may subsequently lead tofailure. This is called hinging, since the

motion of the flexing panel rotates around tpoint of restraint where the crack appears.Running strakes, chines, steps, transom

edges and all other sharp corners concentrathe bending stresses from wave pounding abouncing along on the trailer. Such areas athe most demanding of careful workmanshiFiberglass is reluctant to lay neatly into sharcorners in the mold: fibers get thinned out athey are pushed in with a lay-up tool, airbubbles remain and resin pools without muglass content. In a poorly designed and

constructed hull, premature cracking and fawill begin at these locations; an experiencehull surveyor will look here first for signs of

Hinging & Cracking

Despite the fact that fiberglass boats appear to last forever,

poor construction and reckless use result in flexing of many

hulls and decks. Initially, telltale cracking appears on the

surface, and as it progresses, major structural failure can

occur. In extreme cases, flex-related damage can sink a

boat. Find out why your boat is flexing, how to survey thedamage, then effectively repair it to prevent recurrence.

Flex-related hinging in a powerboat

Figure 1

Floor

Strake(hinge

Stringer

Panel

Hinging in a sailboat.

Figure 2

Ballast

Keelbolt

Floortimber

Hingepoint

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failure to come.Hinging problems are also common in sailboa

Flex-related stress cracks often occur above thewaterline in the relatively flat forward sections of thehull, usually along the line of a bulkhead or vee-bertop. Relatively flat hull panels tend to oil-can or poin and out as the boat beats to weather. Due to asailboats lower speeds and correspondingly crackare usually confined to the gelcoat layer and represfor the short term anyway, cosmetic rather thanstructural problems. A surveyor will usually recommrather than require repairs to be done in the fullnetime to these topside stress cracks.

A more serious problem sometimes occurs whean external fin keel is bolted to a hull extension or kstub (Figure 2). The heavy side loads created whethe boat is heeled can cause hinging to occur at theradius where the glass keel stub meets the hull. If thinterior stringers, grid structure or floor timberssupporting the keel are properly engineered and

constructed and subsequently remain undamaged,there are rarely any problems. If, however, the intestructure is damaged or the tabbing securing thestructure to the hull is delaminated (typically bygrounding), the keel stub can bend and flex freely. concentrates stress at the stub-to-hull radius. The smathe radius at this location the greater the stress

Do not ignore these cracks: (1) Commonstress cracks caused by minor hinging offlat panel at a bulkhead or vee-berth; (2)Hull deflection due to bad cradling; (3)Long random cracks wide enough toinsert a penny; (4) A tight group ofparallel cracks on runabout at bowindicates trailer damage; (5) Stress cracksat stanchion bases, (6) deck hardwareand (7) corners at cabin-deck joint; (8)

Concen-tric circular cracks on cored deckmay indicate wet core.

DAVIDAIKEN

1

2

3

4

5

6

7

8

Structural Flex Cracks

Telltale

signs ofvast

structuraldamage after

grounding a fin-keeled sailboat: the

hulls forward motion thrusts thekeels leading edge back and the trailing

edge gets rammed up into the hull togenerate highly visible hinging cracks and

failure at the hull-keel joint.

DAVIDAIKEN

Figure 3

HARSH REALITY

A word of warning about cosmetic deck strescracks around hardware and fittings. These astressed and flexed during normal use and evif a perfect crack repair is done, the crack wilikely return because the pattern of use andloading hasnt changed. Do cosmetic repairslike this just before you put the boat up for sal

TIPS

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concentration which can lead to seriouscracking and delamination (Figure 3). [Ed:For how to diagnose and repair delaminatedhulls and decks, refer to failures, Repairs andPrevention on page 16.]

The radius dimension at the top of the keelstub is an important variable in determiningwhether or not flex will eventually create aproblem. Many well-built small- to medium-sized sailboats have very simple and shallow

keel stub structures with a large stub-to-hullradius. In lieu of floor timbers or a grid structurethey may have heavy solid, unidirectional glassreinforcement at the keel bolts. These boatshave shown a surprising ability to bounce offrocks with only minor damage. Larger, equallywell built boats (some from the samemanufacturer), built to maximize performanceoften have a deep rigid keel stub with interiorstructural reinforcement and a relatively rigidcored hull. These stronger, more rigid and

more complex structures fare less well whengrounded, exceeding the loads they werecarefully engineered for. Damage may not beobvious to the untrained eye and the boatcontinues sailing for several seasons, enduringbroken tabbing, delamination, loose stringersand the resulting excessive flex, until it starts tosink. Haul out reveals a big crack thatoriginated some time ago from a subtle stresscrack barely visible through the antifouling.Repairing such severe damage is strictly therealm of the professional yard and often

requires the input of a naval architect orengineer.

Repair Strategies

Its often not enough to repair the boat bysimply rebuilding and relaminating the origstructures using the original laminate schedHull stiffness, particularly in an aging boat one that was used for a long time with brok

and loose interior structures, may have beeaffected throughout without showing anydelamination or obvious problems. Repairinthe boat by duplicating the original design not solve the problem and reconstruction mrequire additional support structures orreinforcement to successfully return the boaservice.

Often the symptom is repaired withoutcuring the disease. I have seen examples owhere delaminated tabbing at a bulkhead o

stringer is repaired but fails again soonafterwards. The bond was subjected to grestress than it was designed for and until theoverall flexing or bending was reduced, it wimpossible to bond the tabbing permanentlywithout first doing some re-engineering andstructural upgrades. (Most insurance compaand appraisers understand this necessityparticularly if a yard is reluctant to warrantethe job without the input and direction fromengineer or naval architect as to therecommended course of repair.)

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Suppose your hull has a significant crack that isgetting larger or has started to leak. Promptaction is now required. If the hull is cored, thecore is probably wet by now and the area ofwet core will have to be cut out and replaced,a much more complicated procedure.Assuming a non-cored hull, the magnitude ofthe repair depends on the depth of the crack. Ifthe crack is leaking water into the boat, itobviously extends through the laminate. Verysubtle hairline cracks, however, are a cosmeticissue and can be left alone as they likely dontneed any structural repair (see CrackAnalysis on page 15). [Ed: For proper repairprocedures, refer to Fiberglass Cosmetic

Repairs on page 2--.] I dont recommendamateur repair of structural hull problems andneither will your insurance company. Here arethe steps a professional repair would follow.

Step 1

Prep Grinding

Use a feathering sander with a 40-grit disc tolightly remove gelcoat in the repair area toreveal the laminate. This is often the only way,without taking a core sample, to make an

accurate assessment of the extent of damage. Ifthe crack continues into the laminate and ifthere is bruised opaque milky white laminatenearby (indicating delamination) then a grinderis used to remove the cracked and delaminatedfiberglass. This continues until only solid greenor bluish translucent looking laminate is left.Edges of the repair area are featheredsmoothly with a grinder to

an appropriate distance (approximately hathe size of the patch) to ensure good bondiof the new glass laminates that follow.

A crack that travels through the laminathe other side requires extensive grinding arelamination on both sides. This could be achallenge where access is restricted. Somet

it is necessary to remove interior panels whadds to the repair cost.

STEP 2

Glass ClothPreparation

A patch is created byrebuilding the laminates. Tis usually done by applyinmultiple overlapping layermat and roving, oralternatively, a stitchmat (iFabmat) that combines mawith roving in one easy tohandle cloth. Like all glasscloth, stitchmat comes indifferent weights (i.e. 181which combines an 18ozwoven roving with a 1oz and either a plus or minus

Step-by-Step Crack Repair

(Left top) Spider

cracks not causedby stress; (right &

middle) Singlecracks caused by

voids or bubbles;

(bottom) Hairline cracks at deckhardware.

Non-StructuralCosmetic Cracks

Whitish cracks radioutwardsindicate damagedlaminate. Grind thelaminate to removedelaminated glass areinforce laminate.

Laminate patches replace original

structure. Use additional patches on inside to

stiffen repair where

necessary.

PROFESSIONALBOATBUIDERMAGAZINE

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or 0/90 bias which defines the angle theroving is cut on the roll. Either 1810 or 1808stitchmat is ideal for most repair work.

A 3mm (1/8") repair depth needs aboutthree or four layers of mat and roving or two orthree layers of stitchmat; a 6mm (1/4") depthrequires twice that and so on. A fair amount oftime is devoted to cutting and preparing eachlayer ahead of time, carefully cut and sized tothe repair. Each layer is cut to overlap theprevious layer by an inch or two, depending onhow far the feathered edge extends.STEP 3 Lay-up

Glass cloth is usually prewetted with catalyzpolyester (sometimes vinylester or epoxy) rethats carefully applied to the patch area wbrush and roller with additional layers appas required. Trapped air bubbles and exceresin are worked out with a special bubble-buster metal roller.

Im not a fan of using epoxy resins in

repairs to polyester laminates, preferringpolyester or vinylester. No resin will chemicbond once a resin has finished polymerizat(full cure), but rather are mechanical orsecondary bonds. Though epoxy is the mosadhesive of the commonly used resins, thedifferent flex characteristics of the more rigiepoxy patch may cause delamination problater. This is a much-debated issue and somrepairers may argue otherwise. [Ed: Foranother opinion, see Resin Repair Substitu

on page 42.]

STEP 4 Finishing

Quality cosmetic finishing demands a high of artistry. When the laminate patch hascompletely cured, use a feathering sander tremove any rough edges and any portions the patch that sit proud of the surface, andrough up the surface for application of thefinish. For above-waterline repairs, fill low s

with a neutral-colored gelcoat (a pigmentedpolyester resin) thickened with colloidal silica consistency somewhere between peanutbutter and mayonnaise. This filler is carefullapplied with a large putty knife or drywalltrowel to fill repair roughness and pinholevoids. When cured, block sand the filler smwith 80-grit paper. Fill again if needed. A fgelcoat is carefully color-matched and spraypainted over the repair area. Sprayed gelconaturally has a fairly heavy orange peel fin

so it must be laboriously block sanded with paper from 400- to 800-grit (or higher), themachine buffed with a polishing compoundhigh gloss. Below the waterline, whenrecoating with antifouling paint, its sufficiensimply renew the hull coatings in the repairarea.

About the author: Marine specialist Nick Bais service manager of Bristol Marine inMississauga, Ont., an avid Thunderbird-claracer, and a regular contributor to DIY.

FRP FLEXINGCHARACTERISTICS

One of the mechanical properties of FRPcomposites is that they become moreflexible as the years go by. Microscopicdamage to laminates accumulates witheach wave a boat hits. Quality of design

and original construction as well as usage,determines how gracefully a boat ages.(Water absorption and osmosis problemsare other factors that affect the longevityand rigidity of the hull.)

Bending a fiberglass laminate alsostretches the resin and glass. Polyester resinand standard E glass have very differentelongation percentages (a measure ofbrittleness) before breaking. Resin breaks atabout 2% elongation, where glass stretchesalmost 5% before breaking. This is why

gelcoat, which is straight resin, developscracks long before any problems show inthe underlying laminate. Micro-crackingbegins to occur in typical laminates atabout 20% of the ultimate tensile breakingstrength; gelcoat crazing (develops anetwork of fine cracks) at about 50%.

Different resins and gelcoats too havedifferent stretch characteristics. Tough,flexible resins allow the laminate to reachfull tensile strength but may actually flexmore at lower loads. Resins, which aremore stiff and more brittle, actually preventfibers from carrying their full load. Hardbrittle gelcoats are also sometimespreferred by builders because they hold apolish and resist weathering best, but theyare much more subject to stress cracking;less brittle gelcoats are softer and dontweather or hold a shine as well.

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Crack Analysis

There are many different causes for cracks in gelcoat. So when is a gelcoatcrack something to worry about?

1 Classic stress cracks come in all sizes, from minor cosmetic blemishes to grim telltales of immine

structural failure. Typically found in tight corners in the cockpit and on deck, around highly loaded fittings likemooring cleats or blocks (on sailboats) but of more concern below waterline on powerboats,especially on running strakes, etc.

Above the waterline and sometimes below, an individual hairline crack is usually only cosmeticunless its wide enough to insert something into it.

A tight group of parallel cracks indicates a previous big flexing event and blunt trauma (i.e.collision), or trailer damage especially near the bow of the boat where the trailer rollers or buninitially take the weight during retrieval.

Straight crack on hull at bulkhead line usually indicates oil canning flex of nearby panel. Keep eye on it if the crack deepens or can be felt with a light touch, action is required.

2 Isolated spider cracks are cosmetic only. Somebody thumped the hull or deck with a rubber mallet to get it to release from the mold.

Although present from day one, they get uglier as the years go by, sometimes weathering to thepoint where the gelcoat spalls off but still an isolated cosmetic problem.

3 Random long wandering cracks Below waterline only, they indicate moisture absorption into the laminate and swelling or a too

thick gelcoat layer. On a powerboat transom it can indicate a wet transom core.

4 Concentric circular cracks. If on deck around a fitting, they may indicate wet core and possibly even frost heave. On rudder, definitely frost heave from moisture. Small isolated spots on hull or deck may indicate a void or bubble in the lay-up.

At cradle pad areas, indicate improper cradling. If non-cored hull, it may be only cosmetic. If coflex indicates delamination so structural repair needed.

5 At keel hull joint and underwater fittings, fairing filler always cracks when applied over metalfittings, so is cosmetic only.

If a gap shows, retorque keel bolts. Small cracks at faired thru-hulls, shaft struts or rudder heel castings are usally cosmetic only.

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By Nick Bailey

Fiberglassboats arebuilt from a

compositeconsisting ofmultiple layersof high strengthfibers, usuallyglass fiber

woven intocloth, mat orroving, butsometimes Kevlar or carbon fiber wheremaximum strength is required. Fibers are thensaturated and bonded together with ahardened plastic resin, usually polyester, butsometimes epoxy or vinylester.

The strength and stiffness of the resultinglaminate, regardless of the resin and fiberchoice, will depend on thickness, the correctratio of resin to fiber and the effective use of thevarious cloths. Lightweight core materials (i.e.balsa) are often used, particularly in deckconstruction, to obtain the stiffness of a muchthicker solid laminate without the addedweight. Regardless of the construction details,laminates are made up of layers of materialthat can separate. This is delamination.

What is Delamination?

Delamination is one of the two common stressfailure modes that can occur in a fiberglass

laminate; the other being cracking as discussedbeginning on page 40. Cracks result from alaminate flexing and bending and may or maynot be any deeper than the cosmetic gelcoatlayer. [Ed: Refer to DIY 1998-#1 for completestep-by-step fiberglass cosmetic repairprocedures.] A deep crack in the laminate cutsthrough the bundles of fibers which make upthe laminate layers. Delamination is a break inthe bond between the layers. This can occurwithin a solid fiberglass laminate or between acore material and the inner or outer glass skins.Its also a common problem at secondary

bonds attaching interior structures to the huand deck.

Delamination results from either shearstresses where opposing horizontal forcescause the layers to separate and movehorizontally in relation to one another or pestresses where one layer is torn away from others by forces acting vertically on thelaminate.

A delaminated hull may not be inimmediate danger of sinking but the first effof a delaminated condition is a drasticreduction in stiffness. The stiffness or resistato bending of a solid laminate varies with thcube of its thickness: a laminate twice as thwill be eight times as stiff. When a glass laydelaminates, you suddenly have a situationwhere one or more layers is no longer attacto its neighbor and can move independentlyshear as the panel flexes. If the internal bre

in the middle of the laminate stack this wouhalf the effective thickness and cause a drostiffness to 1/8 of the previous value. If twomore layers are delaminated things will getvery soft and spongy. Glass layers now mahave much of their original tensile strength bno longer support each other to give stiffnesOnce excessive flex is allowed the other faimode, cracking and breaking of the glasslayers, will surely follow. Whether or not aglass laminate delaminates depends on twoconditions: the strength and quality of theoriginal construction; and what sort of wea

Delamination: Failures, Repairs andPreventionDelamination can occur in a solid fiberglass laminate or cored

hull, between the inner or outer glass skins, in bulkhead tabbin

fastening interior structures, in deck cores and in rudders. If yo

own an older fiberglassboat or are looking to buy one, heres h

to diagnose the condition and some methods to cure and prev

Rotted core from water ingress.

Delaminatithe bond

between th

balsa core amat layer

Good bond betweencore and mat

Resin-starved layup resultsin poor bonding of mat

Dry areas in laminateresult in unbonded mat

Water-

damaged

Anatomy of a Cored HullDry areas in laminateresult in unbonded m

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tear and abuse it has been subjected to sincethat time.

Pitfalls of Solid Laminates

Many details affect the quality of the bondbetween different layers in a laminate.Laminates least prone to trouble are the primarylaminates applied in the mold wet on wet: thenext layer is applied before the one below has

fully cured allowing the new resin layer to fullycross-link molecules with the previous layer.Traditional iso or ortho polyester resins arerelatively forgiving as they are air inhibitedfrom a full cure at the surface exposed to theair and will remain ready to receive a newlayer of cloth and resin for a long time after thelayers underneath have fully cured. The finallayer will usually include some air-dry wax toisolate the resin from the air and bring it to afull cure. Once any resin is fully cured, it will benecessary to prep grind the surface to promote

a primarily mechanical secondary bond if anyadditional laminates are applied. Wet-on-drysecondary bonds are relied upon to tabbulkheads, stringers, floor grids, etc. in place,and often to bond core materials into the lay-up.

A good wet-on-dry secondary bond shouldbe nearly the same strength as a primary wet-on-wet bond but relies heavily onworkmanship. Inadequate prep grinding orcontamination of the bond surface with wax,moisture or solvents can cause premature

failure. So too can lay-up faults that reducecontact between layers such as inadequate wetout with resin, too many trapped bubbles orbridging where the next layer of cloth or corerises above a bump below.

Use and Abuse Failures

The most obvious causes of delaminationproblems are from impacts or collisions. Whena laminate is struck and bends, the outer layerscome under compression and the innerlaminates stretch under tension (Figure 1).

Opposing forces create shear forces betwethe laminate layers and break them apart. Isevere, the laminate will also crack or tear the point of impact. Delamination around thimpact can be quite extensive, involving the

area of the hull which bent but did notobviously break. Stress cracks are also usuain evidence in the delaminated area. A plapowerboat hull can delaminate over wideareas on the bottom without any obvious sigof distress until cracks appear. Thedelamination in this case is due to the conststress and flex from slamming waves.

Although sailboat hulls can also be

damaged over time by wave pounding, oththan the obvious damage from accidentalgrounding, improper cradling is the mostcommon cause of sailboat hull delaminationMost sailboat manufacturers specify that atleast 60% of the boats weight rests on the with the cradle pads taking the remaining loIf the cradle base frame is not rigid enoughand sags under the keel when transported, can grossly overload the cradle pads, dimpthe hull at the pad locations. A solid glass laup hull may be flexible enough to tolerate

dimpling without permanent damage; if theis cored, then maybe not (see below).

A dubious yard practice, which alsocontributes to sailboat hull problems, is storwith the mast up. Ever notice how a boat wheel 15 or more under bare poles in a stowhen tied to the dock? A 50-knot galeshuddering and shaking a dry-stored boat wmast in will slam load the leeward cradle pwith many extra pounds per square foot. Imnot going to attempt to calculate the loads, judging from the damage I have seen, the

typical four- or six-pad storage cradle was

Typical fiber-reinforced plastic lay-up

for a 25-footer.

ALISON

HOOD

Roving

Inner resin coat

Gelcoat

Mat

Mat

Impact Forces on

Laminates

DAV

IDAIKEN

Figure 1

BEFORE

DURING

AFTER

Outerlaminate undercompression

CracksCracks

Bond between laminatesbreaks

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never designed to safely distribute suchoverloads, nor was the hull designed with this

sort of abuse in mind.

Wet Delamination

In extreme cases of water absorption into asolid laminate very large osmosis blisters canform between the laminate layers. These canbe pie-plate size and bigger, and the osmotic

pressure forces apart the laminates. Suchdelamination problem is rare where boats hauland dry during the off-season, but is morecommon where boats remain in the water year-round, particularly the tropics.

Core Problems:

Manufacturing

Cored laminates employ either balsa or PVCfoam cores in a sandwich construction tomaximize stiffness without adding weight.

When laying up a hull or deck its often difficultto get a perfect bond between the core and theinner and outer laminates. New techniquessuch as vacuum bagging, the application ofcore bonding putties, improvements in the corematerials themselves, and the use of variousresin-infusion processes all contribute to betterbonds between the core and inner and outerskins than was possible using the traditionalhand lay-up technique. Despite the fact that aperfect bond between core and skins wasdifficult to achieve in the past, thousands of

production-line boats with cored hulls exist andnearly all have cored decks.

Core lay-ups are traditionally applied byprewetting the core with catalyzed resin andbedding it down to a resin-rich layer of mat.When the core is layered after resin has gelled,this causes bonding problems and futuredelamination.

Core designed to lay into a curved surface,such as a deck, is contour cut into small blocksand held together with a light scrim of backingmaterial. When not enough resin soaks into thegaps between the core blocks, the bond is too

dry and weak and delaminates. When toomuch resin soaks in, particularly when thinnwith more styrene monomer than ideal, styrvapor lingers in the core, the resin never fucures and it delaminates. The problem ofexcess styrene vapor is surprisingly commocan register as a wet area on a moisture malbeit its usually nowhere near any hardwathat could provide ingress for water. A coresample reveals dry core, tacky resin and the

characteristically pungent odor of styrene smells like maraschino cherries and vinega

Core Problems: Maintenan

Even when a cored laminate is wellconstructed, its subject to water penetrationfrom leaking thru-hulls and deck hardware.theory, well-bonded core should not allowwater to migrate from a leaking fitting. Inpractice, the partly open slots of the contoucore blocks provide passageways for wateinfiltrate. This occurs more rapidly below th

waterline in the curved hull panels and morslowly in the flat deck areas. For example, tquickest way I know to condemn a cored hto a premature death is to install a knotmetedepthsounder thru-hull into a cored areawithout removing the core at the thru-hulllocation. Because of this risk mostmanufacturers of boats with cored hulls willprovide a special location where the core hbeen deleted suitable for thru-hull installatioThe affect is further exag gerated in northerclimates, where the soggy core is subject to

freezing and the resulting frost heave furthedelaminates the lay-up. The same leak-freezdelaminate cycle is also responsible for macored decks on older boats facing radicalsurgery.

Cradling Cored HullsThe same cradling concerns mentioned abohold true for cored hulls. Although a coredlaminate is more rigid and will resist cradledimpling, it has structural limits. Any significdepression or dimple at the cradle pad usu

indicates that the delamination damage isalready done. Sometimes the delamination cradle pad results from an internal fracture the core itself as opposed to a loss of bond the inner or outer skins.

Detection

Detecting delamination is surprisinglystraightforward. A surveyor will refer to thetechnique as percussive sounding, whichsimply involves light tapping usually with ahammer. Healthy laminate gives off a nice

sharp rap or knock; spongy or delaminated18

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Used in decks and other curved surfaces, BalteksContourkore is end-grain balsa core panels cut

into small squares and glued to a fiberglass scrim.

BALT

EKCORP.

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areas a softer thud or muffled thump. Thetechnique is not infallible: areas of fairing fillercan sound cheesy but may not be of any realconcern and thick laminates with a deepinternal delamination may sound quite solid. Adry delaminated deck when walked on maycrack underfoot. Should delamination besuspect, a moisture meter reading and possiblya core sample analysis will determine how bestto proceed.

Repairing Solid Lay-up

Repairing delaminated solid lay-ups requiresaddressing the bad area aggressively with agrinder and 36-grit paper to remove thedamaged laminates. Its usually possible toleave the very last laminate in place to providea backing for the new layers of glass. Therepair proceeds like any other glass repair,except that you may have to reinforce andstiffen the hull if excessive flex led to theproblem. If the solid laminate is also very wet

and delamination is the result of very largeinterlaminate blisters, the boat will needextensive drying, peeling and other workassociated with a major osmosis repair.

Core Repairs

Deteriorated cores are the most commondelamination repair. If the core is dry, it maybe possible to rebond the skin to the core byresin injection and infusion. This is usually doneby drilling a variety of holes in the outer skinand persuading unthickened catalyzed epoxyresin by gravity or vacuum into the holes todiffuse throughout the damaged area. After theresin cures, the area should be rebonded. If thecore is wet, you have no option but to cut awaythe outer skin to expose and dry out or replacethe wet core.

Wide soggy areas require major surgeryand reconstruction but localized areas near aleaky fitting or thru-hull can sometimes beaddressed without large-scale removal of theouter skin. A good example is wet deck corearound a deck fill plate or ventilator mount.These fittings already require a large hole in

the deck that allows access to the damagedcore. A variety of improvised tools can be uto dig out the hole perimeter [Ed: See DIY1998-#2], wet balsa core which is soft, rotand easy to remove. Leave the hole exposea dry or covered location long enough to dthe adjacent core that may be merely dampopposed to wet. When dry, the cavity is fillwith resin and chopped glass fiber mix orthickened epoxy resin and the fitting reinsta

To gain access to a localized bad area, cuopening, then later install (after the repair isdone) a new deck prism, hatch, ventilator owhatever. This approach neatly sidesteps thissue of how to refinish the repair area,particularly if its patterned nonskid and modifficult to duplicate. Tip: Its often easier tosand off the nonskid in the repair area andfinish the gelcoat as a smooth glossy finish.this to the matching area on the other side ayour deck appears factory-original despite localized repair.

Prevention and Maintenanc

The single most important maintenance itemall cored hulls or decks is to seal all fittingsfastened into or through the core (Page 5)This is rarely done; most cored decks sufferyears of neglect simply because core leaksinitially do not drip water inside the boat. Bthe time you see the brown-colored ooze onheadliner, its too late a sure sign ofterminally rotted balsa core.

The solution to the problem of fasteners

allowing leaks into the core is to remove thecore adjacent to the fastener and replace itwith solid, impermeable material (thickenedepoxy resin or polyester and chopped fiberprocess known as potting (page 35). Ifmanufacturers had done this beforehand, bmay have been more expensive butdelamination failures would be less of aconcern today. To lessen core problems, Irecommend a moisture survey at least everyfive years and a complete rebed of deck

hardware every 10 years or as needed,whichever comes first.

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By Ken Hendry

A 1990 Regal 32 Commodore was slated fora routine blister repair job so the hull wassandblasted below the waterline to open voidsand create texture for subsequent coats ofepoxy resin and Interlux Interprotect barriercoating. Blasting exposed the typical small

osmotic voids extending to the laminate, butalso many nickel-sized areas with a shallow,flat bottom and obvious dry laminate. Suchcondition prompted a call to a surveyor toexamine the results and devise a repairstrategy.

Close inspection found a resin-starvedouter laminate under the gelcoat. Rope-likefiber laid along the chine and strake edgesfrom bow to stern to provide a sharper edgewas also badly resin starved. Completeremoval of the gelcoat was recommended bythe surveyor.

I didnt relish doing what must be one ofthe least pleasant jobs on a boat, namelysanding and grinding, especially grindinggelcoat off the multi strakes of a large cruiserthat results in many hours refilling gouges.Instead, I opted to have the hull peeled; aremoval technique that involves using a hand-held power razor to strip coatings on flat orcurved surfaces to a specified measured depth.[Ed: For a synopsis on peeling, refer to

Removing Coatings in DIY 2000-#2].In three hours the peeler machine hadremoved all gelcoat, including on the chinesand strakes, leaving a smooth outer laminatethat was sanded to obtain good tooth beforerecoating. Peeling had exposed deep voids,probably from air bubbles in the resin, inseveral areas. It also chipped the fiberreinforcing on chines and strakes, mostly due tothe lack of resin bonding the fibers. Anothercall to the surveyor resulted in an increasedrepair requirement of laying a thin mat (veil

mat) reinforcement with epoxy resin over theexisting outer laminate to provide extra resin

thickness and surface strengthening. Pieces mat, about 2m (6'6") long and the widthbetween the strakes were laid on dry thenwetted out with epoxy resin, first brushed othen rolled out and squeegeed. Mat is easieapply than fiberglass cloth as the weavedoesnt skew (twist) when rolled out. About hours were spent laying down the mat,applying another coat of epoxy resin andreconstructing the chine and strake edges. Athe surface was sanded and faired with

thickened epoxy, I applied Interprotect barrcoat followed by antifouling. It took 73 hoto complete the job and repair costs notincluding taxes totalled $6,631 in Canadiafunds: $500 for sandblasting; $900 forpeeling; $150 for the survey; $1,416 for pand materials; and $3,665 for labor.

Though this was my first occurrence widry delamination, its apparently becomingmore prevalent, especially with older boats[Ed: Paul and Sheryl Shard recorded the drdelamination of their sailboats entire outer

laminate and step-by-step repair in DIY 199#2.] No manufacturer is infallible - lemonswell documented in the automotive market -and I suspect this cruiser was just the bad oin a lot and not representative of the builde(The boatbuilder did compensate the ownewho was not the original owner, for a portiof the repair costs.)

About the author: Ken Hendry operatesHendrys Trent Talbot Marina in Beaverton,Ont., and is an experienced fiberglass andosmosis repairer.

Understanding Dry Delamination

Peeling a 32-footer took three hours, removed

about 90% of the gelcoat and required minimalsanding to ready the hull for recoating.

Examples of Dry Delamination: (top)

Sandblasting of hull reveals resin-starved pockin outer laminate; (bottom) Peeling of outer

laminateexposes dry areas on chine anddeeper air hole on hull side.

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By Wayne Redditt

When most people think of flotation in smallboats they immediately think "foam" andinvariably have a story to tell about watersaturation. So what can you do about flotationand foams in particular? Let us first examinethe underlying reasons why foam is the mostpopular form of flotation material.

Federal regulations require flotation inboats under 6m (20'), except canoes, kayaks,sailboats and some other craft. American Boatand Yacht Council (ABYC) defines three typesof flotation: basic prevents a swamped

inboard, stern drive or sailboat from sinkingwhen its passengers are in the water clingingto it; level flotation keeps a swampedoutboard-powered boat over 2hp floating in alevel position; and modified basic flotationdelivers the same buoyancy as basic but alsofloats manually-propelled boats and outboardboats with less than 2hp in a level attitude.ABYC also specifies building practices thatcover buoyancy in the event of swamping. Inbrief, the recommendations cover three types

of installed flotation: non-integral air chambers;pre-shaped plastic foam; and liquid mix plasticfoam poured or sprayed in place.

Non-integral air chambers are separatefrom the hull structure. These include airbladders which are commonly placed in

canoes and kayaks. Testing procedures formanufactured boats require that integral aichambers be flooded. This eliminates anyconstruction flaws. Few manufacturers use

type of flotation in small boats.Rigid urethane foam blocks and other

shapes are cut to size to fit hull cavities. Rigfoam is expensive and requires more time tinstall than the blow- or pour-in liquid foamwhich partially explains the widespread usthe latter.

Besides ease of use, there are a numbeother reasons that manufacturers use theblown-in urethane foam. It expands to fill incavities completely and bonds to surfaces.

creates a very rigid-feeling structure. Theadhesive properties can also be utilized tosecure structures and accessories, such as fwater and holding tanks. A boat that hasplenty of blown-in foam seems solid and wbuilt.

Replacing Foam FlotationBoat manufacturers add foam flotation for safety. When

foam absorbs water it increases the boat's designed

weight which affects performance, handling and flotation

capacity. Replacing the foam is possible, but not easy.

Placement of Level Flotation Foam for Typical Runabout

Fb=flotation material needed to support the swamped boat.Fp=flotation material needed to support the engine.

Fc=flotation material to support the live load.

ABYC

Level flotation foam keeps an outboard-powerrunabout afloat when swamped.

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Over time, repetitive hull slamming, freeze-thaw cycles and water lying in the bilge causesan unpredictable deterioration in the water-saturated, closed-cell foam. This results in theboat becoming excessively heavy, whichaffects performance and handling, and createsa loss of flotation capacity. This loss of flotationmay be sufficient to sink a boat whenswamped. Fortunately, many manufacturersexceed the recommended standards forflotation and should the foam degrade, theirboats still float.

What can you do if you suspect that theflotation foam in your boat is saturated? Simplyweighing the boat will tell you whether or notthe foam has become heavy with water.Alternatively, have a marine surveyor performa moisture check with a meter to distinguishwet structures from dry ones. You may evenhave access into flotation compartmentsthrough inspection ports.

Once diagnosed, the decision to replacethe foam may require careful consideration.Most manufacturers do not intend the foam to

be removed and it's not an easy task. The stuffbonds strongly to the hull, stringers, deckstructures and whatever else it contacts. In mostcases, removing the foam requires removal ofthe floor and bulkheads. Removal is entirelymechanical and manual. Chisels, pry-bars,scrapers, grinders and the like are the toolsneeded for the job. There are no solvents thatyou can pour onto the cavities to simplydissolve the foam.

The time may come when you decide torefoam the hull to achieve the buoyancynecessary for safety. Over the years, every

possible option for replacing flotation has btried Ping-Pong balls, white or blue

Styrofoam, even Styrofoam peanuts. BecauStyrofoam doesn't resist gasoline or styrenecarrying products like uncured polyester reyou cannot use it in the bilge or as a "glasin" component. Some boaters may opt to wStyrofoam in polyethylene plastic and heatsealing the film or perhaps use zip-lockingfreezer bags to prevent fluids from contactiand degrading the foam. Personally, I wouopt for closed-cell urethane foam blocks cufit into the hull cavities. One benefit of thisapproach is that you can insure the drain h

in the bilge remain open and free to transpwater to the pumps.

Using pour-in-place urethane foam thaexpands to fill the compartments may beattempted by the do-it-yourselfer, but becareful. The foam has enormous capacity todistort structures as it expands. By notcalculating the volume properly, I once bula cockpit sole about 2.5cm (1") in the centon a small cathedral hull runabout. It alsomakes keeping the bilge drain holes open

extremely difficult. And you don't want toperpetuate the problem of water collecting saturating the foam all over again.

The benefits of positive flotation havesaved many lives. If you wish to calculate tflotation required for your boat, ABYCpublishes a detailed formula in its manual.Interested readers should contact DIY's editfor copies.

About the author: Wayne Redditt teachesboatbuilding, repair and restoration atGeorgian College's Marine Technology-Recreation course in Orillia, Ont.

Level flotation foam keeps an outboard-poweredrunabout afloat when swamped.

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Damage to non-skid decks is usually caused bydropping heavy objects, such as the anchor ora hammer, or stowing small outboards,bicycles, a dinghy or other bulky geartopsides. Repairing premixed painted non-skidis easy, just reapply. It becomes more difficultwith a molded non-skid. The procedures

outlined below use a three-step repair method:First a pattern or mold is made of the non-skid,a replacement patch is laminated from themold, which is then glued onto the deck afterremoving the damaged deck surface. This isnot an easy repair and usually takes somecareful analysis of deck camber, total area ofrepair and pattern alignment.

STEP 1

To make the mold, first select a flat portion ofthe non-skid deck that is in good condition.Wash the surface and let it dry. Mask off anarea twice as large as the repair area. Usepaper or plastic sheeting to prevent overspraygetting on the deck. Clean the work area withacetone. Using a disposable Preval sprayer(available at autobody supply shops), spraythe masked area with a thin, even coating ofpolyvinyl alcohol (PVA). Wear a respirator this is toxic stuff! You can use mold-releasewax instead but it fills up the pores, giving anuneven coating. If the work area is notcompletely covered with PVA, the mold willstick to the deck and youll be doing anotherrepair. Allow the PVA film to dry for about 20minutes.

STEP 2Use a syringe to measure the exact amounts ofcolor-matched gelcoat and catalyst. (A metricone is preferred as its easier to calibrate inmillilitres than ounces.) Measure the gelcoat

then load it into the Preval spray bottle. Adcatalyst at a ratio of 2%. An easy method tmeasure it is to calculate the number of droper millilitre. In our demonstration, five droequaled 1ml. Dont overcatalyze. Stir well.Working time is about 20 minutes.

STEP 3

Spray a thick coating of gelcoat over the PVfilm. Do not brush on the gelcoat. If you disthe PVA with the brush the mold will stick todeck. Note the dam formed by masking taalong the edges of the work area in the phThis is so the sprayed gelcoat doesnt creahard edge. Let the gelcoat cure completely(one to two hours).

Repairing Non-Skid

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STEP 4

Build your mold by laying up three or fourlayers of chop-strand mat soaked in generalpurpose polyester or vinylester resin mixedwith hardener according to directions. Pour asmall quantity of resin in the center of the cloth,then spread with a squeegee.

STEP 5

When all the layers are wetted out, use a

ribbed metal roller, working toward the edges,to remove air bubbles. If youre in a hurry, youcan overcatalyze resin by up to 5% whenmaking your mold and replacement patch.Your finished mold should be about 4.7mm(3/16) thick. Let cure overnight, then pop itoff the deck. Wash both the mold and decksurface with water to remove the PVA.

STEP 6

To make a replacement patch, take your mand repeat the entire laminating process. Fwax the mold (use PVA or mold-release wathen spray or brush on a thin coating of comatched gelcoat. Dont make this too thickgrid pattern in the mold should be just almofilled.

STEP 7

Once the gelcoat has cured, laminate twolayers of chop-strand mat onto the gelcoat.cure overnight. Remove the part from the mThis should perfectly match the pattern andcolor of your decks non-skid. If the bottom your replacement piece isnt uniform, sanduntil flat.

STEP 8

Outline the repair area on deck with a felt so it forms a square or rectangle. This is theeasiest to cut, although you can radius thecorners. If your non-skid has a geometric

pattern, count the number of diamonds, forexample, so that all sides are equal and yobe cutting in the groove.

STEP 9Using a router with a 1/2 straight, single-carbide cutting bit, carefully remove the desurface. (Dont use spiral or double flute bitwhich tend to break away.) Step the depththe cuts so you just cut into the laminate bethe gelcoat. Make the first cut no more than1.5mm (1/16). Keep lowering the router

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until the cutting depth matches the thickness ofyour replacement piece. Cut carefully. Toodeep and youll go through the deck. Dont dothis with an expensive router as fiberglass dustwill destroy it.

STEP 10Square the corners with a chisel, cutting intothe repair zone. If you attempt to chisel into thegood non-skid, it will crack the gelcoat andyoull have an ever-growing repair zone.Transfer the shape of your deck cutout to your

replacement patch, aligning the pattern so itmatches perfectly. Place it in a vice, then cut tosize with a hacksaw. A hacksaw gives aperfectly clean cut without the edges breakingaway. Dry-fit your patch and file, if necessary,with a metal file to fit the deck cutout.

STEP 11To make an invisible repair, mix some color-matched gelcoat with catalyst and apply to theedge of the deck cutout. (We used a lightergelcoat for demonstration purposes.) When the

patch is positioned, it will squeeze out thegelcoat, eliminating the join line.

STEP 12

Mix a small quantity of laminating resin wicatalyst and drop some in the center of thecutout. This acts as a glue. Be careful not to

touch the gelcoat. Place a few strands of mcut to short lengths with scissors, in the bottto help bond the repair.

STEP 13

Place the replacement part in the cutout.Immediately remove any excess gelcoat wian acetone-soaked rag. The color-matchedgelcoat gives a virtually invisible repair.(Contrasting gelcoat was used and is visiblthe photo.) Weigh down the patch with aheavy object.

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TOOLS ANDMATERIALS

HammerChisels7-1/4 circular saw

with saw blade andMultidisc

Tape measureDrill and bitsHolesaw set

JigsawBelt sanderLow-rpm (2,500)

orbital sanderScrewdriversWrenchesTaps and tap handleScissorsKnifePencilMarkers

Fairing boardEpoxy and polyester

resinLaminating supplies

including: rollers,squeegees, tonguedepressors

Rubber glovesDust mask

By Don Campbell

After many years of dinghysailing, Don and Phoebe Campbelldecided to look for a larger boat thatcould be cruised and raced on theGreat Lakes. They narrowed theirchoice to a 30-footer or larger with afull keel and a budget below $25,000,then went boat shopping. Of theavailable boats they discovered twoclasses: those that were structurally

unsound and those that were abovetheir budget. They found a 1973

Alberg 30 in Niagara-on-the-Lake, Ont. Thewas sound but the deck and cockpit floor wemushy. Water weeped out of the stanchiowhich were movable through as much as 35and a moisture meter read higher than 60%half of the deck.

A survey revealed no surprises. Watersaturation had decayed a large portion of thbalsa-cored deck. Preliminary estimates fromboat repair yards started at CDN$6,000 forknown conditions and more if things were w

once the deck was opened up. Knowing all otheir options, they purchased the boat at agiveaway price, trucked the boat home and it into an unheated equipment shed to do therepairs themselves.

Don had built two Mirror dinghies fromand so had some experience with epoxy anpolyester resins. He had a considerable amoof other building experience making equipmfor his vegetable farm processing lines, but hnever undertaken a project such as this. Herhow Don replacedWhite Opals totally

saturated cored deck.

he first step of the repair was to visit alocal boat repair yard for someprofessional advice. Generally, mostrepairers are willing to give advice a

help if asked. Even if there is a cost, it will both time and money on the job.

I was advised to fully scaffold the entirhull. It was expensive to do but saved much

Replacing a Soggy DeckA water-saturated, cored deck poses a safety concern a

reduces a boats resale value. If your boat is in such

condition, dont despair. Heres a solution that is not too

costly, provided you have the time and patience to learn

and do the repairs yourself.

T

Strips of the outer deck laminate showing the rotted co

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time and wear and tear on the hull fromladders, and my knees from climbing, andsimplifies working with power tools andchemicals. The pros also recommended usingdiamond-cutting tools to remove the outer skinof fiberglass, leaving some of the original topsurface for bonding the final layers. (Glassfibers quickly dull carbide and steel cuttingblades.)

Repairing a delaminated deck involves

stripping the outer skin, excavating the wet,mushy core and replacing it, then rebuildingthe laminate. On some boats it may benecessary to brace the deck with verticalsupports placed in the cabin before removingthe outer skin to prevent sagging and tomaintain the original deck shape.

Preparation

Before starting the repair, photographs of thedeck were taken in series so that the whole

deck could be reassembled in one composite.Next, all fasteners and hardware wereremoved and labeled, then stored in markedboxes. The outer skin of the entire deck andcockpit floor was cut into about 30.4cm (1)sections through to the core using a Multidisc(it has diamond chips in the blades) in a 7-1/4 circular saw. A 5cm- (2-) wide stripwas left on the outside edges along thecabin, cockpit and toe rail. (One cutting discdid the entire deck, about 34m (114).) Thedeck was then peeled off where it was weak

and chiseled away where necessary.

1

Side deck prepped for balsa core after

coating the inner skin with polyester

then epoxy resins. Note the bevelededges.

THE RIGHT TOOLS FOR

THE JOB

As the laminate was left intact around thedges for matching and bonding surfaceremoving the core between the outer aninner skins was a big problem. After tryiseveral tool shops without success, I inititried a circular saw blade on a variablespeed drill. This was too unsafe and haron the wrists and it tended to make holethe inner skin. After two days of drawingand an hour with the cutting torch, Itransformed a piece of 6.3cm (2-1/2)heavy angle iron into a horizontal chise(Figure A) with a flat top for hitting withhammer. I then made a mirror image, rathan use my left hand on the hammer, athat was effective for most of the removasaw blade was fitted with a handle (FigB) and that worked well to gouge out themushy core. A fairing board was made hickory, cut thin enough to flex and yetstrong enough to be useful. A broken sh

handle was sectioned for the handles.

A

B

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Removal of the balsa core, 6mm (1/4) in thedeck and 9mm (3/8) in the cockpit floor,was done with a 5cm (2) chisel. A wider,homemade chisel made of a truck springwould have been quicker. The hardest jobwas to remove the core between the skinlayers left on the edges and for that I madethe necessary tools (see The Right Tools forthe Job). The edges of the outer skin werethen beveled to give as wide a scarf joint as

possible.

Lay up

After thoroughly vacuuming the deck twice, alayer of polyester resin was brushed on theinner skin and while still green (uncured),overcoated with West epoxy applied with anotched squeegee. While the yardrecommended using polyester resin, I chooseepoxy instead so this step was necessary toinsure good adhesion.) A layer of 2-oz woven

cloth was laid in and wetted out with epoxyfollowed by a layer of 6-oz cloth (Figure 1).The 6mm (1/4) balsa core was then fittedand epoxied to the laminate. A coat of epoxywas then rolled over the top surface to seal thecore. All thru-hulls were marked and at least2.54cm (1) of the core surrounding the fittingswas removed and the cavity filled with athickened epoxy mixture so thecore would be sealed when thethru-hull was fitted. I then appliedtwo layers of 6-oz cloth and thesurface was faired with epoxymixed with microspheres. A final 6-oz layer of cloth was applied andwhen fully cured, the surface fairedwith epoxy and microspheres. Twocoats of epoxy were then rolled onto seal the fairing compound andlightly sanded and prepped forpainting.

A similar procedure wascarried out for the cockpit floor

with two extra layers of fiberglasstape feathered onto the verticalsides. (Cores in most decks arenormally used only for thehorizontal surfaces.) Because of thedecks long narrow shape, we cutthe cloth into 45cm (18) strips orsmaller and butt joined the ends.One large piece was used for theforedeck. These were all cut andset in place. If two layers wereapplied green on green (while

still tacky), the second layer was

set close to the work area before mixing thresin. Care was taken to taper and staggejoins of each layer. Resin was mixed in smbatches that were usable before they heateFillers included cabosil, microfibres andmicroballoons used to thicken the epoxy,increase bonding strength, facilitate sandindecrease sagging, depending upon the neSmooth squeegees and rollers were used toapply epoxy to cloth and notched squeege

were used with a lot of pressure to applyfairing compounds. Ridges were intentionaleft in fairing layers to reduce sanding timeand once fair, a layer of epoxy was appliewith rollers or smooth squeegees or both toin the low spots. As many of the resin andcloth layers as practical were applied greto avoid t

Fiberglass Clinic

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