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Clint Wasserman builds a Dillon Sport C Tunnelboat

Clint is building his Dillon Sport C in Australia with an eye on running in the Austrailia 25hp class at the 112km Bridge to Bridge race. The record time for the event is 75 mins.

Power will be a "stock Mercury / Tohatsu Seapro 25hp restriction plate removed with advanced timing same as 30hp. Mercury Racing chopper II 18p and Powertech through hub 14p. Running a jack plate, hot foot, cable drum steer and a small nose job for higher running."

Clint also posting his project on Boat Racing Facts. See it HERE.

"Approx 18hrs into the build, working with imperial measure has been slowing me down but I'm getting there with only weekends to work on it."

"I have changed the shape of the sponson outer decks and gunnel strip also flattened the bow ramp angle on the tunnel floor. The motor board will be set back further aft, allowing me to extend the rear cowling and move the cockpit further towards the bow."

Clint has also purchased Cockpit Plans for his boat.

"Constructing with 2 sheets of 3mm & 7 sheets of 6mm okoume AAA marine ply with radiator pine for all other lumber. 'West system' epoxy resin for the glue."

"Plumbed up a level chipboard base to true the hull on. This will also make a good movable work bench when I put a top, some legs and caster wheels on it."

"So far no permanent screws, staples or nails have been needed. Just epoxy and quick clamps. Used a lazer pointer to check truness and straight edges. Just need to check diagonals to see if it's all square before I go any further."

Clint decided to notch the battens into the beams, cutting half-notches in each element.

"I have flattened the tunnel floor and added extra halving joints to give a little more strength," Clint says.

I'm not sure how cutting notches in all these part strengthens anything, but it probably won't hurt.

"Finished all the tunnel battens with halving joints across all the beams. I therefore had to router out some [limbers] for the water to flow aft."

"I actually used 18mm (3/4") battens the entire length, so I will be using the router again to mill them down towards the bow to save some weight."

"Put the rear section of the floor [tunnel plank] on this morning with a 3" wide scarf joint."

"Also placed 2" spray rails on the inside of the sponsons."

"Put a plywood bench top on my work bench/ tote trolly/ timber rack as resin was dropping all over my stacked timber."

"Spray rail and you can see how I've flattened the floor in this pic, although hard to see, I have curved the tunnel floor slightly towards the bow starting from bulkhead two."

"Didn't seem like I got much done today but really I haven't stopped ! Can't wait to get stringers on and finish the bottom of the hull so I can flip it over"

"Starting on the sponsons now."

"I've let the cat out of the bag early showing how it's going to look finished :)"

Oh yeah, that looks like a real raceboat!

ADD: "Sad news. I can't run an enclosed cockpit in the AustralianPBA."

Then later: "Good news. Found out I can run a cockpit and enclosed rear cowling, I'm just not allowed to have a canopy fitted making the boat an enclosed cell, which needs to be certified, driver needs air and restraints."

"Therefore I can run in the bridge to bridge and the 25hp class. Better yet there is a 550 class which allows me to run up to 40hp stock motor. ([Sport C] in the USA.)"

"Almost finished the sponsons, I preferred to start the timbers at the transom leaving them unattached to the tips, which allows them to naturally take shape overnight and the next day before securing to the sponson tips."

"I also left them longer which gave much better leverage."

"I've got 1 month to have the boat finished and set up to enter this year's bridge to bridge. If not there's always next year"

"Planed all the sponson timbers today and manged to fit the bottom plank to one side. I cut a 2" scarf joint into the ply and joined them in the middle of bulkhead 3."

"Accidentally put the sponson tips on upside down. Hahaha. Oh well, guess I'll just have to cut them off and put them on properly."

"Work then beer. Not beer then work. Lol."

"Been flat out all Saturday again. Couldn't wait to turn it over and start some work on the top."

"Almost finished the sponsons."

"Time to flip it over and start some work right side up."

"Today, I routered a lot of the timbers, to reduce weight. I cut all the deck batons and finished one side of the transome. Will be starting on the cockpit very soon."

"You can see the shape of the top deck, and sides of sponsons taking shape.Can't wait to get stuck into again tomorrow. Actually I'll be building tonight while I sleep. Lol."

"I decided to use 12mm plywood ripped into 1/2" wide strips that was left over from a sheet of exterior grade plywood used to make the cockpit bulkheads. Cockpit will be 20" wide in the interior."

Getting a rough fit to the hull.

"Covered the cockpit mold in corecell foam via counter sunk screws. Applied first layer of double cross bias fiberglass with epoxy resin."

"Got the second layer of fiberglass on the cockpit. Marked the floor line along the bottom and the cut outs for the beams."

"Shaped the aft bulk head tapering in to match my... cowling."

"Picked up a new motor for the boat. A tohatsu m50d. Just need a prop and repair the engine hood."

"I will be changing class to the 800cc outboard open hull."

"Unfortunately the cockpit didn't turn out as good as I was hoping. Only myself to blame. So I've got to try and pull into shape with ply bulkheads and sand fill the hell out of it, or build a cockpit in plywood and cut my loses."

"...I decided to not go any further with the fiberglass cockpit and have made up a plywood version instead."

"So it will look the same, just not the strength of a conposite construction."

"Drilled the air holes in the tunnel bulkheads and started on the steering column assembly and foot throttle position."

"My little Co-pilot."

"Turned over the boat today, planked the front section of the sponson I hadn't completed. Then taking the advice from Dillon Racing plans of doubling up the pads, I started over with a second layer of 6mm ply to strengthen the sponsons. At 12mm thick sponson pads this boat should be able to run races with A little more throttle in choppy conditions."

"Worked on finishing the left sponson today and faired the right side. Going to make some torture boards to true the hull before I lay down any resin coats."

Torture boards?? Should we alert the UN High Commissioner?

"Lol sorry, a sanding board. Two long piece's of timber approx 2m in length with a straight edge with one fastened on top of the other like a T shape to keep straight. Stick 50 or 60 grit sandpaper along the horizontal surface. Use the vertical as a handle. It helps to have 2 people to use the 'torture board' one on either end to sand the longer surfaces. Probly just a silly name my foreman made up when I was building furniture that's stuck with me."

"Sanded the bottom as flat as I could then applied 3 coats of epoxy resin, 2 with a roller, one with a brush. Definitely recommend roller only, brush does not apply even enough. Will need a few little pin holes touched up, air bubbles sanded out and another fine sand before applying another 2 Coats of Resin. Sides will be painted, thought I'd just get them sealed at the same time."

"Working around the bow beam, I had always likes the arrow head point rather than the straight beam across the front of the boat. So I placed the plywood tunnel plank extension on and started forming a piece of timber glued to the leading edge. The carlins will need to be extended and re-curved to suit."

"I glued the transom pieces on this morning and started to shape the top deck for one side. Next step is to do any last bracing with wood then sand and resin the inside sponson ready for the top deck to be fitted and then repeat for the other side. Once the decks are on I'm sure I'll fly through the last bits till finished:
Transom Bracing.
Cockpit dash and seat
Cockpit nose cowling with access hatch
Sponson and fuselage nose cones"

"You can see... how I have decided to use two transom pieces either side of the beam for extra strength. Large holes will allow air flow and water to exit the rear."

January 2015: "The bridge to bridge that I wish to race in is in May. So I have until then to have it finished, tested and set up ready to race."

"Layed down a nice thick coat of resin inside one of the sponsons."

"I also made an upper mount for the steer shaft, cut two pieces of lumber that will run down the sides from the top of the transom to the floor beam, [and] made a foot rest...."

"...and rechecked driver position with the wheel fitted."

"Also picked up a cheap trailer and began to modify it to suit the tunnel hull."

"I have made a strong point for the 2.5cm tow eye hook Under the bow."

"Also you can see how I have made a strong area for the steering shaft to attach to."

"Upper steering shaft mount complete, and revised into a lower-angled position for more comfort and easier control."

"Made the dash and added some lumber to the top of the cockpit sides to strengthen them."

"Big thanks to Bob from Dillon Racing... that has helped me along the build. Great advice and true gentleman. Without Bob's feedback and support I'd be in deep water alone."

"Another wet day, left the boat in the garage and finished the foot throttle mounting plate and the foot rest."

"Being mounted down low should also help with a lower cg."

"Shown with my daughter aboard, you can see there is just enough room for the steer shaft and the foot throttle."

"Using some 3mm ply strips made cut from scraps, every last bit can be of use. The front bulkhead was cut to help gain access after I installed the cockpit with the strips of ply. The middle section will have a removable hatch for access to the foot throttle and the cable steer drum."

"Trimmed up and gave it a rough 1st sand. I'm very happy with the shape."

"Fabricated the middle nose cowling that is removable, first made a frame with a ply bulkhead at either end, then more strips of 3mm ply to cover it."

"I ended up purchasing inexpensive pool noodles for flotation, 6 per side it should be more than enough to keep her afloat. I also purchased some floor sponge mats that will be used in the cockpit."

Reply from another BRF member: "Hey the Top Fuel Drag Hydros use the noodles. I can't see any problem."

"I decided to have a rest from the wood working and build the jackplate today. I used Dillon Racing's jackplate plans idea, of using right angle aluminum. Quick easy and cost effective."

"Motor sits nice and when I hang of it bouncing there is no flex, no cracking or creaking noises. Solid as rock."

"Routered out the dash to fit my apexi 5" tachometer with temp, pressure and memory recall. Going to pull it apart to 'marinise' it with some circuit board lacquer."

"Layed some carbon fiber on the dash for the race look and also added strength. Tachometer was not able to be read once the wheel went on so I had to make another piece to drop down the tach and cover the old hole. Fitted a push button start with kill switch in the dash also."

"On the outside I cut out a hole for a battery isolation kill switch."

"Glued on the right front sponson deck. Joined with a 60mm scarf joint, and held down with staples untill the epoxy resin drys. The inner tunnel deck front will need a piece of timber running across the butt joint to insure a good seal."

"At last the decks are on. Started to shape the nose cone for the fuselage... "

"...and cut off the tips of the sponson ends rounding them to 35mm."

"1st coat of resin on top."

"Layed down some 410 West Systems sanding filler to both sides, wetting out with resin first. Unfortunately you can't wash out the foam rollers however it applies so much easier and uses a lot less resin for coverage."

"Applied the second coat of 410 filler with more resin so that I could use some cheap throw away small paint rollers for the application. Sand, seal , sand again and then I'm painting it. Just want to get it rigged and in the water now."

"Flipped the boat back over to sand smooth and finish coat the underside of the hull. Don't want to pull the motor off and do it later so I'll be trying to get it as smooth and flat as possible on the sponson pads."

"Sponson pads finished with 2 coats of epoxy resin. Came out fairly smooth. I'm happy with it and if i wanted any smoother, I think you would need to spray finish."

Sides and tunnel plank done.

"After much thought, I'm going to paint the bottom of the boat. The West Systems 105 epoxy resin is not a finishing product. Nor has it any UV protection ( even though undernieth UV will affect the epoxy over time). So to keep it clear I need to purchase West Systems 107 UV protective clear coat And coat several times. I'm not going to do this. Single stage clear varnish wouldnt be any good for the boat left on wet trailer rails. 2k clear is expensive, and so is the 2k paint."

"So after some research, and remembering a tunnel hull I built 17 yrs ago, the paint I used on that lasted for ever. Australian Comapany Norglass Weatherfast make a product called pri-coat undercoat primer will be applied with a spray gun and rubbed back smooth. Then spray on some coats of Weatherfast enamel paint. Much cheaper and I can do this myself At home."

"Sprayed on the undercoat, let it dry then started to wet sand smooth. Turning out well, its good practice for the top deck."

"We have been struck by a destructive cyclone. 135klm winds, 15m seas, trees blocked roads, cut power, no communication, no shops or petrol available. Mass flooding, constant heavy Rain. 1/4 million homes went off power for at least two days. Still recovering. But today the sun came back out so out came my boat"

"Second coat of undercoat applied to restore a uniform base white color so that the red paint will not have blotches."

"Paint on. A couple of runs but I'm not so worried being underneath the boat . No leaves or flies blew onto the wet paint so I'm pretty happy with it."

"Flipped the boat back over..."

"...and finished the front sponson tips in 6mm ply. These will be used to make a mold that I can make some more out of foam, fibreglass or other materials. Once the mold is made , these can also be used on the boat."

"Woohoo ! Paint is on ! Didn't get the best paint job done but it will do for now. A couple of runs, bugs, debris. Only one coat of red, so I can always rub back and spray a cleaner second coat later on. Sitting in the garage with the heater on to help bake the enamel paint and bring out the gloss. Should be ready to walk on the decks and drop in the water in about 4 to 5 days Once the paint has gone hard."

"Finished off the motorboard by laminated plywood with a 12mm thick plastic chopping board to help against crush into the wood, also reduce vibration. Fitted the jackplate, lifted on the motor and bolted it all up."

"Well I couldn't wait any longer. Today I slipped it in the drink to see how it would float and idle and turn. It floated really good, gave it a little throttle and felt it climbing onto the plane with ease. So I touched the throttle and she sat up onto the plane and begun to lift the sponsons out of the water. Motor is set too low for this initial test run, I wasn't going to go flat out just wanted to see how she sat in the water, balance, leaks, vision etc."

"Boat feels solid, no cracking and movement noises, vibration was not too bad considering a cleaver and wooden hull. Trim switches and steering works great."

"Still need to do some editing of the footage from my friend's video's, here's a quick... screen shot...."

"Still have to shape and sand down one side yet but it's getting there."

"APBA (Australian Powerboat Association) Saftey officer said I had to cut off the hoop top and can't run a rear cowl, just leave it fully open. So I've cut it off and I think it looks awesome like this, too!"

"After my motor blew up the mechanic took 3 yrs to rebuild it, ending with a ported high compression race engine! The 40 now a 50, plus porting and jetting to suit. Should get my boat going now at approx 65hp!"

"I've joined a local powerboat club, the UHPBC, and about to sign up for a full race licence with the APBA. One club meet before an event in May: a 30klm river race!"

"So excited to (finally!) go racing. I will report back with my progress soon."

I just hit 100kph...! I'm glad I took away a bit of the aero lift and lengthened the hull, it sure is shakey at 100kph in a very slight chop and wind but extremely stable. With the power trim I can feed a lot of bow lift into the hull and it does not feel like it wants to suddenly lift up and flip. Although obviously i was at a more neutral trim at high speeds.

60mph is only 3.5 kph slower than 100kph so really theres not much difference although at top end speeds a couple of times i felt the hydro lift take over and it was really flying liturely. felt like the whole boat lifted up flat ( not bow lift ) and started to gain rpm and speed.... So its going great so far mate, theres more to be had with motor tune prop tune and hull set up yet, ie motor height ! it could easy see the 70mph I think....

So over all i think its working out.

My mod DRP Sport C tunnel Boat is reaching speeds close to 70mph now. 67mph or 108kph to be exact with a mod Merc TE clever. Very stable, feels safe. With a merc chopperII 10.38x 18Pitch with some tip cup, for circuit racing is revving to 7300rpm! and screams, mate, ready to win some races ;)

Missed out on the club day the other day as I fell a bit sick the day before. However, the Double Dash, a 32klm long river race on the 5th of May is now going to be my first race. Cheers Bob, your boat is generating a lot of interest in the race scene...

"Raced the boat on the weekend!!"

YouTube video HERE. You can see Clint at 3:45 minutes and 4:32 minutes.

"Was crazy fun. Boat performed well, the thicker sponsons with alot more freeboard (than all the thin sponson scaled down F1 design 12ft tunnels) helped cross bow wake at speed. It slides a bit and cornering is something I have to still get used too, its a very very fine line between not enough turn in and too much as it sometimes grabs and rails around the corner. Motor height must be slot on as I don't want anymore crab walking.... Sudden gusts grabbed the boat up but it was no problem to control it. Glad I ran in the 60mph class and not 70mph though, 70mph would be alot of constant neg trim that's for sure. Wouldn't want to run 70mph unless it was glass conditions really, otherwise the 37min river run would be more about endurance in these little boats. The big boat 21ft 225hp that came 3rd, they can make a cup of tea racing while I'm in a 'milkshake machine '."

"Sitting nice at 56mph. Back into the wind you can see it lifted a few times but this is what I mean it feels sorta safe there and needs a lot more to blow over. Was so much fun. Lost my front cowl on the way down river due to not securing it properly. Have to make a new one. Whoops ! So much fun mate. Love this sport."

"A quick update on racing the Dillon hull. My 1st club day , i raced around the APBA circuit last Sunday with 700m straights. I reached speeds of 65mph (106kph) down the straights. The hull felt great and ran through any small waves with ease. Cornering also felt very stable while the G's were going up the more and more i progressed my cornering skills."

"I was way in front of the 550 class and yamato boats and a few people commented on how well the boat was performing on the course."


"I found a 2 cylinder M40C tohatsu for my boat. Going down to the 550 class as there was no other boats for an 800cc modified motor class."

Here's the 40C in its original form....

... And here's the somewhat modified version. I see a nosecone with low water pickup, and a new clamp bracket.

"Ran 3rd place in a APBA [Australian Power Boat Association] race today, was so much fun. Boat was literally flying ! off some of the bow wake, as there were 8 other boats in the race. 3 laps total."

"Boat was going really well, I just have to learn to corner better. Tachometer was showing 7,000rpm and the M40X was screaming. So happy with the boat. Still no signs of any stress fractures, the hull is holding up to a beating really well. Very solid construction, thanks to your plans."

"Here is a good picture of the boat, less positive trim . I was putting on a show for the camera/crowd before [prev pic], the boat does not normally fly this high, but in the choppy water at speeds over 90kph [~55mph], it was dancing off the sponsons, similar to an F1 at high speeds. The aero lift is amazing in this boat, and extremely stable from blowing over.

Twice now the boat has lifted off near vertical, totally my fault, not the boats design, thought I was going over backwards, however it just flew like a kite for I'm guessing 20m then came back down again. Dont want to push my luck for a 3rd time, but at least with APBA club days, they have a safety boat and diver at the ready if you do go for a swim."

"The weather blew up a little on race day last weekend, all the smaller lighter weight V hulls had to back off due to cracking fibreglass, bouncing around like a milkshake or lifting off near vertical off the bigger waves / choppy water conditions."

"With the Sports C at 3.5m, and approx 80kg unrigged, I was able to hold the throttle on wide open and just hang on for the ride. I was starting to position myself closer to the steering wheel, attempting to gain more weight forward to assist with the the boat from taking flight over the waves. With full negative trim and sitting on the front of the seat, the boat flew level and skipped across the top of the waves."

"With this i managed a 1st place and a 2nd place out of 3 races. I had also changed to a faster prop, the mercury racing chopper 10 3/8×18. The natural bow lift and over the hub exhaust seems to work well with my boat in these ruff conditions.

"The boat after only 3 race meets in APBA 550cc super sports class is starting to look like it's going to be an extremely competitive boat, already leaving many seasonal racers behind in its 1st outings, its an extremely fast boat the Sports C hull with the Tohastu M40C 492cc outboard."

"RTAC club event day. I was placed away from the main body of V hull boats and put up agaisnt the yamato tunnels, but I absolutely flogged the pants off them, winning 3 out 3 races with half a lap in front. They normally place 3rd in the class. I'm going to take pole 1 next! Watch me."

"Hi Bob, great news, I came 1st for the race season.
All the best mate, hope your doing well.
Kind regards,

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