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A boat plug

Posted by Sandy 
A boat plug
November 01, 2017 06:41PM
This is an almost finished boat plug, for a big boat. 18' foot gunwale. 66" inch wide bottom. Almost but not quite flat in the middle. Stronger rocker out at the ends.

I've talked about this for a long time. Health issues kept it from happening for almost two years. Now it seems to be happening.

This will be a decked big water dory.

Fiberglass bottom (3/4" Plascore) and 6" inches up the side. Then a transition from fiberglass to 3/8" Meranti Hydrotech sides. 1/2" inch Meranti Hydrotech deck. There will be no gunwale. The deck will run flat across from side to side, somewhat like the little blue Dayak I've shown in other posts.


Not resolved parts of the design include the seating. I'll never have more that two passengers but some Briggs boats have 4--two up front and two in the rear.

I'd like to make a boat that COULD take 4 passengers even though I never will. Putting the weight out at the ends Briggs style (most Briggs boats have two seats at each end, far apart from the rower) makes the boat side-to-side unstable and very hard to turn.

Payload weight should be crammed as close to the middle of the boat as possible, as two rows of two seats right in front of the rower. The turning axis (a line between the oarlocks) should be right on top of the boat's center of gravity. Trouble is the center of gravity changes with differing payloads. Seats need to be movable.

All that passenger weight should shift a bit forward and back depending on how many passengers there are. How to make the rower and two rows of two seats shift forward and back as needed on a decked boat is........unresolved. I'm working on it. I have some ideas.

I'm a month or two away from that stage yet.

Re: A boat plug
November 01, 2017 06:44PM
I used scrap particle board rectangles as bracing/stiffening between rib formers on this plug. I've never done this before but this is a big boat and and an experimental technique so I wanted it a stout plug. So I can bash on it without worrying about knocking anything out of wack during trial-and-error construction steps.

I'll drape visqueen over the mold and glass on a bottom, chine and (6" inches) up the sides. Then shim out the remaining part of the sides form and add 3/8" plywood sides, bolted and caulked to the fiberglass bottom. This bottom will be a full foot and a half wider that the Briggs.

I've mentioned this idea a dozen times in the past. More than one nay-sayer has explained in great detail why this idea is no good and why it won't work.

We'll see. I have great confidence I can make this work :=))

Re: A boat plug
November 01, 2017 10:53PM
Panels are made.....assembly comes soon

Re: A boat plug
November 02, 2017 03:08PM
Are you going to lap joint the plywood sides onto the plascore?
Re: A boat plug
November 02, 2017 03:30PM
At strategic points (every $x inches apart) I'll fill the Plascore cells with resin putty in a half dollar sized circle, so the 3/8" Meranti Hydrotech sides can bolt down hard onto the Plascore without collapsing it. All along that edge I'll use a sticky, stretchable, expandable marine caulk that has little to no bonding power.

I want every piece of this boat to be screwed or bolted together, over caulk, so any and every part can be taken off and replaced as needed.

That's my caulk and I'm sticking to it.

Re: A boat plug
November 02, 2017 08:08PM
Will the plywood sit on the inside of the plascore or on the outside? Could you use two pieces of 3/4 " plascore for the side, cut a rabbit into it along the top edge, drop in a gasket material and then drop the plywood into it and bolt it? Just a thought.
Re: A boat plug
November 02, 2017 10:04PM
The plywood will sit on the outside. I thought about carving a notch into the plascore so it would be flush, but then I'd have to fill a large amount of open honeycomb core cells, so the two could seal up with caulk.

I'll just let the plywood overlap on the outside. This will be a decked boat so interior partitions will extend from the bottom of the deck down to the floor of the boat (also caulked not glued....it will all come apart like an erector set). And those interior partitions will help fix everything together.

Marine caulk does have some bonding power, somewhat like silicone seal. Enough bonding to hold things together but it can still be removed. Parts that are glued together are hard to get apart without damage.
Re: A boat plug
November 06, 2017 02:20PM
I can't wait to see it. I like the idea of experimental boats.
Re: A boat plug
November 06, 2017 03:06PM
I too look forward to the travails and tribulations of your efforts. You have always been ahead of your time in the construction and design of wood drift boats.

Rick N
Re: A boat plug
November 10, 2017 02:00AM
Sandy how is the new project coming along?
Re: A boat plug
November 10, 2017 06:20PM
I'm in Texas working on bird photos. Back in Montana right before Turkey day.

I'm almost ready to glass up the bottom panel.....I'm in Texas with only a phone.....

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