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Questions from Builders and Prospective Builders
-- Construction Issues --

Actual questions from people who have bought my plans or are thinking of doing so.
The answers I provided for them are occasionally suplimented with some additional (ADD:) information.

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General Questions Design Modifications
Finishing Your Boat


General Questions

Easiest to Build?
"Which is the easier to build for a first timer, the Pro Tunnel or Pro Vee?"

I would say the Pro Vee would be somewhat easier. The Mini Vee is the simplest of all, a very good choice for a first time builder.

ADD: The EZ Tunnel is the simplest of the tunnelboats, specifically designed for the first-time builder.

Fastest Design?
"We race 25hp-35 hp mini boats here [New Zealand], what is your fastest hull out of your boat plans?"

Fastest boat is probably the Pro Tunnel with its 42" wide tunnel. The new EZ Tunnel is also fast, but with 40" tunnel probably not quite the potential, especially with 25hp.

Best Boat for Non-racing?
"I have boat building experience and I am confident I am up to building any of the plans you offer.... My question is what boat would you build if primarily used for pleasure?"

The v-bottoms can be a handfull to drive in rough water, and they are a pretty rough ride as well. Tunnels are very stable, and when riding high up on their sponsons, most of their bottom is held up above the waves.

I would build the Pro Tunnel.

Best Glue?
"What type of glue would you recommend to use on the boat as far as for assembling all the pieces together? Would you use a glue and screw combination or would the epoxy glue alone be strong enough to hold?"

Epoxy is the best overall choice. I've built boat using mostly Titebond 3, though there are always places I prefer to use epoxy. With either glue, screws are optional -- it certainly is ok to use both.

ADD: Epoxy is very forgiving, filling gaps in imperfect joints. Titebond 3, on the other hand, does not have good gap-filling qualities, so tight fitting joints are a must.

Using the Plans
"Are the plans large enough to trace or do I have to draw the panels?"

The plans are usually delivered by email then printed by the buyer on 8.5" x 11" paper. They must then be drawn full-size from these drawings, either right on the plywood or onto paper to make patterns if the builder prefers.

Metric Measurements?
"Just asking: Do you have by chance a Metric version of the plans?"

No, sorry. My CAD program doesn't offer the conversion.

Building Cost?
"What do you normally end up spending when building one of your boats minus the motor?"

Generally, between $800 and $1200. Depends on the pywood you use -- marine is expensive, exterior is cheap. Hardware can be purchased new, or you can save money with used stuff or by making some things yourself.

Drawing Curves
"Can you give me an idea of how hard it is to trace out the full sized pieces using your instructions. The part I am most worried about are the curves (eg. on the top of the bulkheads). How are these created from your drawings?"

After drawing all the straight lines, bend a batten through the five points (shown in red, below). If the batten does not land on the the middle point, don't worry about it, the other four are the critical ones. Your batten should be about 1/4" x 3/4", and at least 60 inches long. Also use the batten to draw the curves of the stem and coaming.

More on the general subject of drawing curves, found in the EZ Tunnel notes.

Ligntening Holes
"A question for you regarding the lightening holes; is their any rhyme or reason to the size and / or placement? Also, is there a better time to cut them? before assembly (ie after cutting the individual frames), or after getting set-up on the combings?"

Cut the holes in the coamings, stem and bulkheads before assembling anything, much easier that way. I just cut some pretty big holes, not big enough to compromise strength. I'm not under any illusions that much weight is going to be removed so I just cut out what seems sensible. I'm sure I could cut out more than I do without any problems. The other reason for the holes is air circulation through the hull to make sure it dries out.

ADD: An exercise in extreme lightening, see Sport C 2012.

Tunnel Sides Plywood Joint
"Wanted to ask you if the tunnel sides could be constructed out of two pieces due to the size of boards we can get, or if the [racing rules] require the tunnel sides be constructed from a single panel with no weak point? Also wanted to ask if able to split the tunnel sides, where you would recommend splitting them at so that it does not affect the integrity of the boat?"

The tunnel sides can certainly be made from two pieces, and pretty much have to be as you are unlikely to find plywood longer than 8 feet -- and even if you do, it would likely be two pieces joined together anyway.

The location of that joint is not particularly important except that you wouldn't want it to end up right where a bulkhead will attach -- that's just a matter of convenience, not structural integrity. By the time the sponson sides have glue blocks, stringers and other parts attached to them, there will be nothing weak about this joint.

Boat Weight?
"Me and my son are thinking about building a speedboat with the possibility of competing in the GT15/GT30 class racing. These classes race with a standard EPA-certified outboard in either 15 (10 to 16 YO) or 30 hp (14 and up)

"The boats are V-bottomed monohulls of minimum 3.5 X 1.3 meters (11.48' X 4.27') with a minimum weight of 210 kg (463 lbs) with a 15 hp and 250 kg (551 lbs) with a 30 hp outboard, full rig including driver.

"Would the Pro Vee be suitable for these classes? I have tried to calculate full weight but I really have a hard time estimating what the added weight to the bare hull will be. All my calculations tend to end up on the heavier side though"

I am currently racing a Mini Vee in our GT Pro class, which has a minimum weight of 650 lbs. Actual weight of my boat, after racing, is about 655 lbs. I carry 45 lbs. of ballast. We also use hydraulic trim in our class -- trim pump, cylinder and associated hardware weigh 20-25 lbs. The battery to run trim and electric start is 17 lbs. My motor weighs 120 lbs., and I weigh 175.

I built this boat with 5mm exterior grade plywood, which weighs about 21 lbs per sheet. 5mm okoume marine plywood is probably slightly lighter. Also, I use a high, double-thick coaming, for minimal driver protection. Lower, single layer coamings could be used if you prefer. Some weight savings could also be realized by using 3mm plywood for the deck.

The Pro Vee is likely to be slightly heavier than the Mini Vee. The Pro is longer and the bottom planking is laminated with two layers of 3mm, which is naturally heavier than a single layer of 5mm. Performance is similar for the Pro Vee and Mini Vee. The Mini Vee is simpler to build.

I have not tried very hard to keep the weight down when building my v-bottoms, because I know they will always be plenty light for our classes. Eliminating ballast, trim, and battery from my boat should reduce overall weight to about 575 lbs. Reducing all possible weight during the building process should be good for another 10 lbs. That's getting pretty close to your 551 limit.

ADD: The latest Mini Vee that I built... weighs 140 lbs. That's a true bare hull, with no finish other than the inaccessable spaces under the deck, and no flotation poured yet.

Steering Systems?
" Is there a rule in racing that requires the cable/drum steering? I feel more comfortable with "modern" cable/sleeve systems."

You ARE allowed to use "ride-guide" steering. What I don't like about them is you have to turn the wheel an awful lot -- maybe 3/4 turn or more -- to get through a turn, as apposed to about 1/4 turn with the steering I build for my boats. It is difficult or impossible to keep a thumb on the trim buttons with ride-guide. It's your choice, but I highly recommend the steering I describe in the building notes.



Design Modifications

Design Modifications

Making the Pro Vee Longer -- or the Mini Vee
"I would like to make it 13 ft. What would I need to do to compensate for the difference?"

If you want to stretch the Pro Vee to 13 ft, you will have to proportionally increase the distances between most of the bulkheads -- and then re-draw the coaming and the stem. This is because the deck-line describes a constant curve from bow to stern.

The Mini Vee would be much easier to stretch. On the Mini Vee, from the transom to approx. amidships, the shape of the hull does not change. Putting more distance between two bulkheads in this part of the boat, and re-drawing the coaming, is all you'd need to do.

Building for a Larger Motor
"Could I strengthen the mini vee to handle a larger motor if I was to make it longer."

The Mini Vee construction notes suggest doubling the thickness of the coaming near the motorboard. See: HERE. I would suggest doubling it all the way to bulkhead #4. And then add 3/4x2 reinforcements as suggested for the Pro Vee -- HERE. I don't believe you would need thicker plywood on the bottom, but be sure it's got good solid structure backing it up.

You might have to move the seat and dashboard farther forward (as measured from the transom). The positions of these features on the Critchfield should give you some guidance. I know when Critchfield or Lee Craft boats have been raced in our GT classes (25hp-35hp), the seat and dash have to be moved aft 12"-18".

Building a Lighter Pro Tunnel
"Is there any negative effects if I build the boat even more lightweight?"

Light weight is fine as long as you don't compromise the structure of the boat. Remember, the sponson pads, from the transom forward about 4 feet (~1.5 meters?), take the most pounding. Maintain strength there.

Two Seater?
"Your Pro Tunnel looks like exactly what I need.... Do you think it could be built to fit two riders one behind the other? They would be kids around 100- 120 lbs."

I think you could make a two-seater out of the Pro Tunnel. There is a bulkhead right behind the normal seat position, which extends all the way to the top of the coaming. If you eliminate the part between the coamings and move the dash forward somewhat, you could fit in two seats, placing them fore and aft of the regular seat position.



Finishing Your Boat

Finishing Your Boat

Epoxy Finish
"Are you putting epoxy resin on the hull with no fiberglass?"

I epoxy the bottom. The rest just gets paint, but our boats don't sit in the water long. If you expect to leave your boat in the water very long then epoxy all over might be a good idea. If leaving in the water a day or two or more at a time then 'glass as well, at least the bottom, transom and aft part of deck.

Epoxy Sources?
"The finish in your construction notes, is that an epoxy that you can pick up at most hardware / home depots? I cant seem to find too many answers locally."

I doubt you'll find epoxy locally [in US, and possibly in Canada, where the questioner lives]. In recent years I've been buying from US Composites, their 635 Thin Epoxy with medium 3:1 hardener. I've also used System Three and West System. All good. I finished my own Pro Vee with epoxy on the pad, where is rested on a central bunk on the trailer, and spar varnish on the rest. Varnish will not stand up to prolonged exposure to wet trailer bunks (or long periods in the water).

Fiberglass?
"Would fiberglassing this boat (Pro Vee) add too much wieght, or give it more options for a heavier motor in your opinion?"

Fiberglass would certainly add weight, but I don't know how much. It won't make it any stronger, only more waterproof. If you intend to leave the boat in the water for extended periods, then it would make sense to 'glass the bottom and transom, maybe even the aftermost part of the deck, which is apt to be awash much of the time. If you really feel you need more strength in the bottom, you'd probably be better off adding a third layer of 3mm plywood. Pound for pound, plywood is stronger than fiberglass.

ADD: Fiberglass (set in epoxy) is probably best thought of as part of your boat's finish, not part of its structure.

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