DINGBAT: An 8-ft.

There's some flashy performance in your small outboard motor that will surprise you when running it on Dingbat.

You can build this most-fun-per-

horsepower waterscooter on Satur-

day and have it in the water for a

full day of boating thrills on Sunday

By WILLIAM D. JACKSON

Craft Print Project No. 323

WATER-SCOOTER rodeos, slalomraces, and obstacle courses—well, theold pond just won't be the same again

when you and your friends show your skill atthese and other water sports with a fleet ofDingbat scooters.

48

With motors up to 10 hp and semi-mono-coque hulls that are built with space-age tech-niques but use ordinary lumberyard materi-als, you can have your share of safe boatingfun without putting a strain on the budget ormissing another day of the boating season.

Bottom Plank is layed out by first drawinga centerline lengthwise on a 4 x 8-ft. sheet ofA-C fir exterior plywood (Fig. 4C). Thendraw in the 21-1/8-in. bow radius, the taperingsides, and the gore that is cut to form theplank. Use a piece of 1 x 4 lumber as aStraightedge and a flexible 1/2 x 3/4-in. woodenbatten to draw the curves. Bend the battenagainst finishing nails partially driven at thelayout points for the gore.

Cut the gore away and, beginning at theaft corners, start sawing the plank to shape.When you reach a point 8 in. from the gore,make a cut in from the edge of the panel. Theremaining extensions will be used while form-

BOAT BUILDER

Water-Going Motorscooter

ing the plank and are cut away later. Beforefurther assembly, rip the stock you will needfor the keelson and stringers as in Fig. 6H.Also cut the transom (Fig. 3B) from 2 x 4stock and then, making a full-size paper pat-tern, shape its ends on a bandsaw.

Frame # 1. Make up the stock for the frame(Fig. 3A) by joining 41-in. lengths of 1 x 4and 1 x 12 with a plywood batten, using glueand #7 x l-in. jh (flathead) screws to securethe batten. Then lay out the centerline andlocate the sides of the frame 20-1/2-in. on eachside of it. Next draw the arc for the deck andlocate the tops of the side-plank flats wherethis arc connects the sides of the frame. Alsodraw in the clearance hole for the steeringdrum and the 2-5/8in. curve for the bottomof the frame. The frame is now ready to bebandsawed to shape.

SPRING, 1960

Next rip the four pieces for the tunnelframe from 2 x 4 stock and trace their outlineson frame #1 (Fig. 5A). Then glue these partsin place and drive #8 x 1-1/2-in. jh screws intothem through #1 frame. When finished, drilla 1/4-in. hole through the lower framepiece totake the 1/22 x 4-in. steering post mounting bolt.

When the transom and #1 frame are com-plete and notched as in Fig. 5, position themon the bottom plank as in Fig. 6A and tracetheir outlines on the plywood. Then removethem and drill 5/32-in. holes to locate # 7 wood-screws at 3-in. intervals in the center of eachoutline. Coat the mating surfaces with glueand secure the parts with # 7 x 1-in. jh screws.Drive enough screws to hold the parts inplace and then turn the assembly over todrive the rest.

Cut the bilge stringers (Fig. 6A) to length49

and slide them through the notches in theframe so their ends are flush at the aft edgeof the transom. Then locate screw holes andattach the stringers with glue and #7 screwsas you did the transom and frame.

When this is complete, you are ready tobegin shaping the bottom plank, borrowing afew tricks from aviation metalsmiths. Firstwrap several turns of light rope around theextensions and tighten them with a smoothbar (Fig. 7). As the gore closes, you will findspots that need trimming to allow the ply-wood to join tightly. This trimming is doneby inserting a handsaw in the slit to removeequal amounts of material from each side.

When the slit is joined so no gaps of over1/16 in. remain, slide the keelson through thetransom until it meets the curve of the stem.Shape the keelson (Fig. 6K) to fit this curveand then install the keelson, using glue anda double row of # 7 x 1-in. screws where itmeets the slit joint.

Make a cardboard template of the curve

along the slit joint from the tip of the keelsonto the stem and use this to lay out the loweredge of the bottom stem piece (Fig. 60G). Sawthis piece to shape on a bandsaw and thensaw it again lengthwise to provide two piecesof the same shape and size.

Lay Out Upper Stem (Fig. 1) to extendfrom frame #1 to the fore end of the lowerstem, and cut a slot in this for the 1/4-in. stemknee (Fig. 6G). The top and bottom edgesof this assembly are faired with a wood raspand block plane and, when the lower edgefits, coat the contacting surfaces with glueand attach the stem to the plank with #7 x1-in. fh screws. Space these 2 in. apart on eachside of the slit joint.

Next cut the side planks to shape as in Fig.6L and set them in position on the ends of thetransom and frame. Use a bevel gage to de-termine the shape of the lower edges wherethey meet the bottom plank, or simply trialfit them to the plywood Then coat the matingsurfaces with glue and fasten the planks to

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SPRING. 1960 51

the transom and framewi th #8 x l-1/2-in.screws. Fasten the ply-w o o d t o t h e s i d eplanks with # 7 x 1-in.s c r ews spaced 3 in .apart, and then roughout the bevel for thedeck as in Fig. 6L.

Fore Deck. Make acardboard pattern todetermine the shape ofthe panel from whichthe fore deck will beformed. Draw a cen-terline on t h e ca rd -board and line this upwith the centerline ofthe hull, holding it inplace on the f r amewith thumbtacks. Usea heavy shears to grad-ually cut away the pat-tern along the center-line (Fig. 7) so it canfollow the curve of thestem to join the bottomplank. Trim the bevelson the side plank andstem as you form thispattern.

When it fits smooth-ly, remove the patternand trace it on 1/4-in.plywood, including theextensions (Fig. 4A)and a generous marginfor trimming. Now cutthis out and temporar-ily fas ten i t to t h eframe wi th wood-screws spaced about 6in. apart. Use the ropewindlass (Fig. 7) todraw the panel intoshape, fitting it as youdid the bottom plank,using a handsaw in theslit to make a smoothjoint.

While the deck isstill in place for fitting,r each t h r o u g h theframe and trace theoutline of the upperstem piece and sideplanks on the plywood.Then remove the deckand drill holes for #7screws, spacing themabout 3-in. apart in thecenter of the outlines.If there is a gap of over1/16 in. forward of theside plank (Fig. 2),

52 BOAT BUILDER

SPRING, 1960 53

glue a filler block at this point before the deckis fastened.

Now give the interior of the hull and theunderside of the deck two coats of sandingsealer and let it dry. Apply glue to the matingsurfaces of the side plank, frame, and stem andthen attach the deck with #7 x 1-in. screws,using a double row along the slit joint.

Join the deck and bottom plank by insert-ing a wood rasp between them and cutting aflat about 1/4 to 3/8 in. wide where the piecesjoin (Fig. 6B). Use a putty knife to place abead of glue, that has been mixed with justenough sawdust filler to prevent it from run-

ning into the joint. Usea flour sifter to getfine, clean sawdust andmix this in a glue suchas Weldwood that willremain somewhat flex-ible after it has cured.

Now have a helperb r a c e the p lywoodwith a piece of 2 x 4while you drive 1-in.wire nails, 2 in. apart,1/2-in. from the edge ofthe deck and bottomplank (Fig 6B). Turnthe hull over to clincht h e n a i l s a n d t h e ndress the edges of theplywood with a woodrasp to provide a crosssection as in Fig 6B.

Transom Knees.Next lay out and cut

the transom knees (Fig. 6) and a pair of3/8-in. plywood facings for the center knee.Before installing these make the motorboard(Fig. 5), gluing up whatever widths of 3/4-in.-thick lumber are available for the core. As-semble the core and facing with glue and 1-in.ringed nails and then trim the core to fit theplywood. Bevel this assembly as in Fig. 5D.

Now assemble the knees and motorboardwith glue and carriage bolts as in Figs. 5Band 6C, locating the shorter knee on the cen-terline and the others flush with each edge.Check the fit of this assembly over the tran-som and then attach it, gluing the knees tothe transom and bottom plank, and coatingthe contacting surfaces of the motorboard andtransom with butyl sealer. When in place,drill 1/4-in. blot holes as in Fig. 5E and runcarriage bolts through the motorboard andtransom.

The step-deck stringers (Fig. 6 are carriedin 3/4-in.-thick lumber facings cut as in Figs.5A and 5C. When the facings are installed,cut the stringers to fit between the transomand frame, and attach these with glue and#8 x 2-in. screws.

Cut another piece of stringer stock to fitbetween the side planks 27 in. forward of thetransom (Fig. 6A). Then attach the endblocks (Fig. 6C) and rip a piece of lumber tofill the space between this crossmember andthe keelson (Fig. 5B). Also cut and installthree pairs of 1/4-in. plywood struts, trimmingtheir upper edges after assembly.

Cut the 1/4-in. plywood tunnel sides as inFig. 4A, making a cardboard pattern wherenecessary to determine its shape. Then attachthe 3/4 x l-1/8-in. seat risers and the compart-ment rails to the plywood (Fig. 11). Notchthe forward ends of the risers into the tunnelframe and attach the sides to the inboarddeck stringers, tunnel frame, and transom

54 BOAT BUILDER

Semi-monocoque hull, featuring techniques used in aircraft production, providesstrength and an efficient underwater design for Dingbat without resorting to

heavy, time-consuming framework and planking.

knees, using glue and 1-in. ringed nails.Before attaching the seat, weld a 22-in.

length of 1/2-in. pipe to a bicycle handlebarclamp, cutting the clamp so its cross sectionmost nearly matches that of the pipe. Insertthis steering assembly in the pulley (Fig. 1)and drill and tap the pipe for a 1/4-in. machinebolt. Then drill the upper tunnel framepieceto line up with the mounting bolt and assem-ble the steering post, collar, and pulley (Fig.5A).

Next cut the spray shield and knee (Fig. 1)to shape. Saw off the forward corner of theknee and cut this into two pieces to be used

as side brackets formountng the shield.Then drill a 3/8-in. holethrough the upper stemand deck to mount theknee with a 3/8-in. lagsc rew . F a s t e n t h eshield to the knee withg lue and #7 x 1-in.s c r e w s , and t h r o u g hthe end brackets with#8 x 1-1/2-in. screws.

N o w i n s t a l l t h es t e e r i n g cab le andc l amps , looping thecable around the steer-ing pulley twice beforeleading it aft aroundthe m o t o r b o a r d tokeep it taut until readyfor use.

Then coat the under-side of the seat andstep decks with sand-ing sealer and, whendry, attach them with#7 x 1-in. s c r e w sspaced 4 in. apart. Usebu ty l s e a l e r a t t h es tep-deck jo in t s , butleave those at the seatdry and p lace flatw a s h e r s u n d e r t h ehead of each screw toallow the seat to be re-moved when installingor w o r k i n g on t h esteering cable.

Before Painting theHull, apply 3-in. widthsof fiber-glass tape tothe seam between thebottom plank and deck(Fig. 6) and at all ex-posed plywood edges.Follow the manufac-turer's i n s t r u c t i o n swhen a p p l y i n g th i sand, when it has cured,give the entire hull onecoat of porch-and-deck

enamel. Trim Dingbat in a contrasting colorto make it highly visible and waterproof itwith a coat of spar varnish.

When the motor is in place, run the cableends through the tiller bar of the motors. Se-cure these with cable clamps.

SPRING, 1960