TW28 Questions

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Jeff
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TW28 Questions

Post by Jeff »

This question arrived via email overnight: "Interested in TW 28 plans. I want the hull made of foam composite. Does your plans correct the frames t For foam buildings. I would not have to do any calculations to adjust plans for foam composite. I plan to build with hull over frame. I have never attempted to build a boat this large. I need the framing to go together easily. I don’t like plywood because I am not that Good of a carpenter. With foam , a wider gap makes a stronger seam and heavier." Jeff



fallguy1000
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Re: TW28 Questions

Post by fallguy1000 »

The tw28 would not be built the same way in foam as in plywood.

I am not the designer, but the way to build the tw28 in foam would probably be with a wooden female jig like I built the Skoota hulls.

The reason for this is quite simple. Foam has very limited strrength and stiffness. So, you cannot just put foam on a male station set and glass it and then flip it over because it WILL lose shape when you flip it for the guts. Station distances cannot be much more than 9-12" apart, etc.

Okay, so then you think, I will make the panels glassed first. Well, this is okay, but the boat will still lose her shape on flip. And even foamed, the panels have unknown torture capabilities.

So, the way this is done is to develop a female jig. Then you make a walkable base. Then you install the bottom table laminated to a certain spec that will tolerate walking on. Then each addition panel is laminated on the table and tortured before too much time passes and the panel is still elastic and then you use screws and wood washer pads and screw the panels through tabbing areas to glue them to the female jig.

This continues until all hull panels are complete, then you install the bulkheads after tabbing. It is tons of work to build this way.

Plywood is much faster because it is so stiff. It will not collapse between stations 18" apart like foam. It will hold the shape of the hull on flip woth jist a few spanners. It uses far less epoxy.

I will not speak for Jacques here, but if he advises to build in foam; you will need a large space for female jig. I kind of doubt he will want the headache.

The other way would be to build two half shells using infusion. This method would require you leave the part in the mould for at least a week so it won't deform.

Foam is really a complexity for the TW28. So easy in ply.
My boat build is here -------->

viewtopic.php?f=12&t=62495

jacquesmm
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Re: TW28 Questions

Post by jacquesmm »

It is possible and Fallguy describes the correct method: plank the foam on a male jig.
This does not require any changes to the lines drawing. My plans give the dimensions inside of the hull skin, it's very easy.
Please see my "Foam Sandwich 101" HowTo file in the tutorials section. It shows that method in details.
Be aware of the cost: foam cost more than plywood and that material requires about two times more fiberglass and resin. I estimate that this would double or triple the cost of materials.
I would have to give you specifications for the hull material but I can do that if and when you buy the plans.
Jacques Mertens - Designer
http://boatbuildercentral.com

fallguy1000
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Re: TW28 Questions

Post by fallguy1000 »

jacquesmm wrote: Thu Jul 28, 2022 10:31 am It is possible and Fallguy describes the correct method: plank the foam on a male jig.
This does not require any changes to the lines drawing. My plans give the dimensions inside of the hull skin, it's very easy.
Please see my "Foam Sandwich 101" HowTo file in the tutorials section. It shows that method in details.
Be aware of the cost: foam cost more than plywood and that material requires about two times more fiberglass and resin. I estimate that this would double or triple the cost of materials.
I would have to give you specifications for the hull material but I can do that if and when you buy the plans.
I actually would prefer a female jig for tw28 in foam. Not to argue; just preference..
My boat build is here -------->

viewtopic.php?f=12&t=62495

TomW1
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Re: TW28 Questions

Post by TomW1 »

Your cost will skyrocket from the upper-$20,000 to the mid-$50,000 or more for foam and that is just for the hull. You do not need to be a very good carpenter to build one of these boats especially if you buy the kits. While I am a fan of foam the cost here sort of takes me back. Until you get her fitted out with a diesel and everything else you're looking at lots more dollars that could be saved by not building in foam.

Don't let me discourage you, if you have the funds do it, just be sure you also have the laminating skills.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

Dougster
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Re: TW28 Questions

Post by Dougster »

Ditto on the carpentry thing regarding the hull. You don't really need the CNC kit either, the cuts aren't demanding and gaps are fine. I think you will develope carpenter skills fitting out the cabin and such and that won't be foam. Cutting you own panels and forgoing foam will sure save some $$ for other boat toys.

Dougster

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