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Old 12-02-2019, 21:25   #1
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Fiberglassing over a composite trimaran

Hi All, I’m quite new here.
I’m looking to purchase my first 25ft Trimaran. It’s a composite build, but I was thinking of fiberglassing it all over to make it more durable.

I wanted to get some advice on doing this.
Is it worth doing?
Do i need to strip it back down the plywood before applying fiberglass?
Would carbon fiber work?
How much fiberglass & epoxy will I need?
Has anyone done this before?
Are there any books or articles you could point me to?

Thanks.
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Old 12-02-2019, 21:38   #2
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Re: Fiberglassing over a composite trimaran

This book would be useful:

https://www.westsystem.com/the-gouge...-construction/
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Old 12-02-2019, 21:50   #3
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Re: Fiberglassing over a composite trimaran

Thanks for the quick response John!
Will Check that out.
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Old 12-02-2019, 22:59   #4
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Re: Fiberglassing over a composite trimaran

Quote:
Originally Posted by JeffH001 View Post
Hi All, Iím quite new here.
Iím looking to purchase my first 25ft Trimaran. Itís a composite build, but I was thinking of fiberglassing it all over to make it more durable.

I wanted to get some advice on doing this.
Is it worth doing?
*Most likely not. If it's delaminating, the wood is probably wet.
Do i need to strip it back down the plywood before applying fiberglass?
*See last answer
Would carbon fiber work?
*There is absolutely no reason to waste money on carbon fiber for this project. It's not going to save weight with all the wood. It's also a bit more difficult to work with for a beginner.
How much fiberglass & epoxy will I need?
*We know nothing about the surface area of the boat. You need to measure.
Has anyone done this before?
*Not really. It was supposed to be done right the first time. If it's falling apart, you'd typically select a different boat.
Are there any books or articles you could point me to?

Thanks.
Definitely read the book linked above as well.
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Old 13-02-2019, 08:20   #5
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Re: Fiberglassing over a composite trimaran

So what is your reasoning? Why do you think this is necessary ? It could be, but you give us no reason why.
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Old 13-02-2019, 08:36   #6
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Re: Fiberglassing over a composite trimaran

If it's epoxy coated you just need to sand to get a clean epoxy base surface, otherwise you're in for a lot of hard work. Be aware that epoxy is not UV stable, so you'll need to varnish or paint the finished job.
Unless you need the strength of the fiberglass for repairs, you could skip that step and go straight to sanding and varnishing/painting.
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Old 13-02-2019, 10:09   #7
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Re: Fiberglassing over a composite trimaran

Be careful with the weight increase; fibreglass with resin is much more weighty than you might think; a 25' tri is likely to be very, very weight sensitive.
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Old 13-02-2019, 14:03   #8
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Re: Fiberglassing over a composite trimaran

I know I still have a lot to learn on this subject.
There is a composite trimaran I’m looking at. I should have asked:
What would be the difference between a composite vs. fiberglass trimaran?
And if fiberglass would give it longevity, would it be advisable to fiberglass the trimaran I’m looking to purchase or just look for one that is already fiberglass?
Also, what would be the rough cost of fiberglassing a 25ft Trimaran?
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Old 13-02-2019, 14:40   #9
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Re: Fiberglassing over a composite trimaran

Composite just means there's more than one material. Plywood/epoxy and fibreglass/resin could both be called composite.

Then there are cored composites. The core could be plywood, end grain balsa or foam, with fibreglass/resin skins. Balsa and foam will have glass inside and out, plywood might only be glassed on the outside, or on the joins or not at all on small boats like dinghies

With balsa and foam cores the fibreglass will usually be heavier, as the cores have limited structural properties.

While plywood is quite strong on it's own, even a lightweight cover of glass will greatly improve water resistance compared to just paint. If water gets into plywood it will eventually rot and need repair. Heavier glass can improve structural strength.
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Old 13-02-2019, 15:23   #10
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Re: Fiberglassing over a composite trimaran

Time to find out what the boat is made of. Please ask and let us know.
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Old 13-02-2019, 15:33   #11
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Re: Fiberglassing over a composite trimaran

I believe it is a plywood composite without fiberglass.
My biggest concern is the water resistance for extended periods in the water.
I really like trimarans for their stability, though currently it’s a choice between this 25ft Trimaran or a 25ft monohul. The monohul I’m looking at doesn’t need much work on it at all, and includes stove, sea toilet, etc. The trimaran is a blank slate on the interior which does appeal to me more, as I can put my stamp on it, though living space would be more cramped for extended stays of more than a few days.

Thanks again for all the info. I have a lot more reading to do before deciding.
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Old 13-02-2019, 16:05   #12
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Re: Fiberglassing over a composite trimaran

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Originally Posted by JeffH001 View Post
I believe it is a plywood composite without fiberglass.
My biggest concern is the water resistance for extended periods in the water.
I really like trimarans for their stability, though currently itís a choice between this 25ft Trimaran or a 25ft monohul. The monohul Iím looking at doesnít need much work on it at all, and includes stove, sea toilet, etc. The trimaran is a blank slate on the interior which does appeal to me more, as I can put my stamp on it, though living space would be more cramped for extended stays of more than a few days.

Thanks again for all the info. I have a lot more reading to do before deciding.

Plywood "composite" without fiberglass is probably just plywood. Painted with epoxy. Or in a worse situation, plywood painted with polyester.

Please find out for sure because we can't help you if we don't know what the boat is made out of.

If it's a plywood tri painted (sealed) with epoxy, the fiberglass isn't necessary. A very thin veil of fiberglass is sometimes put on plywood boats just to increase the resistance to abrasion if you say, plan to put it on a beach a lot or let it hit bottom at low tide.

Otherwise,all the "strength" is in the marine plywood and the epoxy is just there to seal up the wood so it doesn't get wet and rot.

You definitely don't need to add fiberglass to this type of epoxy sealed plywood boat.

But find out what it's really made of from someone.
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Old 13-02-2019, 16:28   #13
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Re: Fiberglassing over a composite trimaran

PICTURES! We demand pictures.

Everyone starts somewhere but we wonít get anywhere going at this rate.
Pictures will go a long way.

Something close up. Also if that are any areas where material have been scratched, scrapped or torn then we could use some close up shots as that would give some good clues as the the design material.
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Old 13-02-2019, 16:33   #14
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Re: Fiberglassing over a composite trimaran

Plywood non glassed is a starting point. Not sure about glass/epoxy on it. ..that is not a great solution either. Some monos were built "one off" with plywood, then glassed. They didn't last forever and were very hard to sell due to reputation. It's difficult to get the glass to adhere entirely to the plywood long term. So you get separation, condensation between and then rot. many asian boats had ply cabins and decks on glass hulls and they were problematic also, but asian plywood so hard to say..... if it's well done and you keep it well protected with paint that may be the best thing really without glass.. Dont pay too much for a ply boat though.
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Old 13-02-2019, 17:08   #15
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Re: Fiberglassing over a composite trimaran

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Plywood non glassed is a starting point. Not sure about glass/epoxy on it. ..that is not a great solution either. Some monos were built "one off" with plywood, then glassed. They didn't last forever and were very hard to sell due to reputation. It's difficult to get the glass to adhere entirely to the plywood long term. So you get separation, condensation between and then rot.
Fiberglass with polyester resin doesn't stick well to wood. Allan Vaitses (the "Guru of 'glass") suggested using fasteners along with the resin to ensure things stuck together. Epoxy resin is much "stickier", and adheres well to wood. Many wood strip/epoxy boats are holding up very well, though it's hard to tell because they've been painted to protect the epoxy from UV degradation - the hulls aren't "bright finished" the way they were when they were new - thirty years ago.

As Cheechako suggests, fiberglass over ply CAN have problems. If the hull is a plywood composite, it has to be plywood and something else. The "something else" makes a big difference. Then you have to look at how well the work was done - both on the plywood and the composite - along wth all the other issues that any boat will have. If it's a tri, you have three hulls to check out, along with all the rigging and whatever other systems there may be. Enough to keep you busy for about a week, if you're into it. Then, if you decide to get the boat, you can start working on it.
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