Can the TX18 be built with PVC foam Core?

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Vundu
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Can the TX18 be built with PVC foam Core?

Post by Vundu »

I am currently building a TX18, and a friend is interested in building one too, is it possible to do this with PVC foam core instead of plywood? Where we live it would actually be cheaper to buy the foam core than marine ply. Specifically Gurit PVC Lite 80kg/m3.

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Re: Can the TX18 be built with PVC foam Core?

Post by Fuzz »

I believe all or almost all of the plans can be built with foam core.
The downside in most cases is cost but I can see from where you are how foam could be cheaper. You will need to get a different glass schedule from JM. It will take more glass to achieve puncture resistance than if built with plywood.

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Re: Can the TX18 be built with PVC foam Core?

Post by Vundu »

Hi Fuzz, thanks for the response. His fear is based on wood rot, and resale value in the future. From my reading online it will be more costly in glass and might even be heavier. Hopefully JM will pick up this thread and pass on his advice.

fallguy1000
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Re: Can the TX18 be built with PVC foam Core?

Post by fallguy1000 »

It is an interesting request. It would not be as easy as tortured ply and you would for sure need to use a jig and perhaps build the panels on a table first...or not. Foam is pretty flimsy without any glass. It does not hold its shape well and bends from standing a panel on edge. The pvc lite does more than corecell a or m.

JM might entertain it simply to make a lighter craft, but the build is much more difficult; so he might not like that part.

These boats resale is not going to be vastly different in foam. Fishing boats are largely available used; so there is always downwards pressure on reselling anything fishing craft sized.
Where guys do well is initial cost vs new and customization. You get what you want.

But the boat in foam might draft even less and you’d almost certainly need a jackplate.

If you laminated one side of each panel; you’d need about a 20’ flat table as well.

It is more complicated than your friend might be assuming as well. If there were station frames then perhaps, but the designs say jig. Unlaminated Pvc lite over a jig would not work as it would sag too much.

Hope this offers some insight.
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Vundu
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Re: Can the TX18 be built with PVC foam Core?

Post by Vundu »

Thanks for the great input Fallguy.
As I have been delaying so long glassing my TX18, the initial thought was to use my hull on its jig as an internal mold and lay the foam over it. Alot of time has passed, and I have added rub rails to my hull, so that idea is out the window.
The next idea would be to keep the jig complete, and make another internal mold with cheap ply over the jig, lay the foam and fibre the outside then flip and do the inside.
My mate is not worried about how much work it is.... as it looks like I am going to be doing the brunt of it, with him giving a running commentary :lol: that way if it fails he can always say 'I told you so!!' hehehe
I also see some education re vacuuming being required! So not an easy project, but as I have a bit of time at the moment it may be very interesting. But not something I am willing to do without significant advice. Hopefully JM will point me in the right direction if it tweaks his interest.

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Re: Can the TX18 be built with PVC foam Core?

Post by TomW1 »

Jacques has no problem with exchanging foam core for the standard plywood core and will give you the specifications needed to layup the foam. He is on vacation right now so it may be a couple of weeks until he can get back to you on this. Jeff the manager at Bateau should see this and respond also. You may also find that purchasing foam and supplies through Bateau is cheaper than locally. Be careful on the epoxy you use that it is compatible with boat building and the foam and fiberglass. They recommend System 3 Silvertip epoxy here.

Good luck on your endeavour.

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

fallguy1000
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Re: Can the TX18 be built with PVC foam Core?

Post by fallguy1000 »

You don’t have to vac bag, but to reduce the resin content and make a stronger laminate; you can.

The best idea is to make the jig into a mould. Don’t forget to plastic it!

Core also needs thermoforming if you have any reverse curves or any curves. You thermoform the curves and run flat sections over a mould and then glass as a single unit. Not sure if pvc lite is used this way.

The only reason for a flat table or vac forming is to lighten and strengthen the boat and avoid needing a full set of stations. The jigs/stations on my build are 90 mm spacings-the panels are all preglassed on a table. If they were not; the boat would end up wavier, heavier, and weaker. But my boat is a 32 footer and being built on female jig. The general concepts are similar. The pvc won’t span 90mm without sagging greatly.
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Re: Can the TX18 be built with PVC foam Core?

Post by topwater »

Jacques has also said that you would not save much weight on a hull under 24 '. Plus the fact of how much more
expensive it would be because of the upgraded epoxy and quantity of epoxy . Core and fiberglass costs also.
You could probably use the same jig if you but a layer 6 oz glass on one side of the foam sheet before cutting
the hull patterns . But then more epoxy and more glass adds to weight and cost.
Novi 23 finally launched !

Vundu
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Re: Can the TX18 be built with PVC foam Core?

Post by Vundu »

Thanks topwater, because of where we are based and the questionable quality of any wood / ply, as well as the costs and logistics, we would ideally like to go the foam core route. I did think the weights might be heavier than the ply version, but this is not a concern at this time. Hopefully when Jacques is back from vacation he can give is a few pointers in terms of core thickness and reinforcement.

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Re: Can the TX18 be built with PVC foam Core?

Post by Reid »

Vundu wrote: Sat Apr 07, 2018 7:18 am Hi Fuzz, thanks for the response. His fear is based on wood rot, and resale value in the future. From my reading online it will be more costly in glass and might even be heavier. Hopefully JM will pick up this thread and pass on his advice.
Vundu,

Like Tom stated earlier, Jacques is on vacation for a few weeks and often does not have WiFi access. Every so often we get requests from builders to switch from Marine Ply to Foam Core. There will be some weight savings but not as much as one would think. Foam Core will soak up more Epoxy than Marine Ply.
In response to your comment above, often people are fearful of building a boat from Marine Plywood. However, if quality Marine Ply is used (not Home Depot boards) and the builder follows the lamination schedule and ensures that the Marine Ply is completely sealed in Epoxy, these boats will outlast any production boat out there, my opinion. Wood rot comes from poor lamination and water intrusion. The same could happen to Foam Core if it is exposed and not sealed properly. Any water intrusion, whether wood or foam, will result in repairs.
Don't get me wrong, Foam Core has its benefits and applications but like others have said, the costs will certainly go up. TomW1 is correct in his recommendation of using Silver Tip Epoxy by System Three. I can tell you that this would be Jacques recommendation as well. This is going to increase the cost significantly.
I certainly don't mean to discourage your friend but just wanted to give you some food for thought.
Best of Luck!
-Reid
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