Re-decking...fiberglass help?

Dream to fish

Deck Swaby
Jul 25, 2009
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Phil
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20' Beachcraft Cuddy
This seems like a very common subject and I've read up on a few different projects here. My boat is going to need a new deck soon so I'm doing the research and planning.

I've come to the conclusion that glassed 3/4" marine ply and epoxy resin is the way to go. What type and how many layers of glass cloth/mat should I use? I was thinking 1708, one layer on the bottom and two on the top side but is the CSM in the 1708 even needed when laminating glass over wood using epoxy instead of polyester resin?

I've read that the CSM sucks up a lot of resin but makes for a better bond to wood when using polyester resin. Since I'm going with epoxy the CSM seems irrelevant? Should I use like 10oz cloth on the top side as the final layer or maybe just forget about the 1708 and use several layers of 10oz cloth all around? Planning on finishing the top with Totalboat total tread non-skid deck paint. I'm pretty sure that most of those glass options would work, I'll be honest.....I've never done this and I don't know what I'm doing...but I am capable and I have built a lot of stuff o er the years. If you have any advice, I'm all ears! Thanks
 
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dwaynesda

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"I've come to the conclusion that glassed 3/4" marine ply and epoxy resin is the way to go."

Yes, that is the way to go. A layer on the underneath side a 2 layers of 10oz on top should be fine. If you will be finishing the deck with non skid paint, you won't even have to fill and sand the weave on the topside.

Be sure to wear gloves and have plenty of them. Be careful on how much resin you mix at a time. The warmer the resin is to start with or the more you mix, the faster it will go off and when it goes off, it does it in a hurry. Only mix up what you can spread in 5 minutes at the beginning if you have never done this before. Get a plastic spreader to spread the resin and go as fast as you can. As you get experience and confidence, you can mix up more to spread.

There are plenty of videos on youtube to watch before you start. It is relatively easy to do.

When you are done, be sure to seal EVERY screw and bolt with deck sealant as you screw them in. Water intrusion is where the rotting starts.

Good luck!
 
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Dream to fish

Deck Swaby
Jul 25, 2009
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Why epoxy ? Use vinylester.
I've read that vinylester has an extremely short shelf life and there was some other negative? Maybe it was really toxic fumes? I can't remember. I've done small projects with epoxy before so I'm not going in completely blind. Just never messed with fiberglass. US composites sells epoxy resin at a price I'm OK with so why not?
 
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acefuture

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Apr 3, 2019
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Are you glassing it into the boat, or is it a deck piece that gets bolted in? 1708 is great but is a thirsty bitch. I just did my 4x10 whaler deck with 2 layers of 1708 and it took 2.5 gallons of epoxy. Not honestly sure why I went with 1708, but I had enough for one layer laying around so opted to go for it. If I were you and didn’t need finishing, I wouldn’t use 1708. Poly, epoxy, vinylester is all fine. People will have their opinions on what’s best but as long as you get a good lamination you’ll be fine with any of them. I personally like epoxy because I don’t need to coat it to get it to fire off. But it’s significantly more expensive than epoxy
 
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Russo

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If that's what you want to call it
I don't really know how short of a shelf life "short" is? Polyester will live in the can 6 months or so no problem in my experience. The cost of epoxy is defiantly higher than the polyester. The polyester defiantly smells stronger when mixing/ applying than the epoxy.
Polyester will mix with MEKP at different ratios so you are able to control how quickly it starts to go off based on the temp of the area you are working in / direct sunlight etc. where as to the best of my knowledge epoxy mixes at a very specific ratio and you adjust the cure speed with the hardener you use.
Epoxy will bond to the polyester but polyester will not bond to epoxy so repairs in the future and finishing will need to take this into account.
As for good info West Systems has excellent tech support and if you are in So Cal any where in the vicinity of Ontario I highly recommend Sherfab (909) 923-2200.
They sell both Polyester and epoxy system products at great prices and are very informative.
I believe the actual reinforcing material you use- I:E: fiberglass chopped strand mating etc. are or can be different when used with epoxy based on the releasing agent they are coated with. You definitely want to be sure the reinforcing material is compatible with the product you use be it resin or epoxy.
 
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Dream to fish

Deck Swaby
Jul 25, 2009
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Phil
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20' Beachcraft Cuddy
From my understanding it isn't polyester with the extremely short shelf life it's vinylester. I could be wrong. I'm not sure if I want to glass the deck into the sides of the hull or just caulk it in with 5200. I'm not completely against using polyester either? I've read that it doesn't bond well to wood. With polyester your probably looking at gel coat to finish right? With the traction additive, I don't think the price is much different than epoxy with urethane paint to finish?
 
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Russo

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If that's what you want to call it
That could be. I have not used vinylester for anything so I can't speak from experience on that one. As for bonding to wood epoxy definitely has a leg up on polyester when referring to repairs made on wet or damp wood. Since you are talking about new clean dry plywood I don't believe you would ever know the difference. There very well maybe be some lab data that would prove the epoxy is stronger, but in a practical sense if done correctly both methods are going to last many years with no issues.

I have laminated new plywood to a repair area with resin and chopped stand matting and I will say with confidence that the wood will fail (wood will be pulled off with the resin) before the bond does from mechanical strength perspective.
you just liberally slop the resin onto the wood and it absorb a decent amount, then coat again while still wet and begin laying up your material. I presume this portion is basically the same as would be done with epoxy.

In all honesty I think this all comes down to cost and familiarity with the products you work with. Resin guys say use resin and epoxy guys say use epoxy. I just used resin because it was lower cost and I knew guys who were very familiar with it so I had quick access to help if I needed it. Any way you go there is going to be a learning curve. AVOID WORKING IN DIRECT SUNLIGHT if at all possible. Setup an easy up, position the boat in the shade if possible etc. It makes a huge difference in how quickly the product starts to go off. Its hard enough without having to race to get it all done while not make a big mess.

As for the non skid/gel coat/ paint question-
Gelcoat is the norm with fiberglass and polyester no doubt about that. You can add non skid directly into the gelcoat if you wanted to.
They make additives that can be used in gelcoat that will allow for is to air cure basically like paint as well. That being said you could also just polyester primer the fiberglass and then topcoat paint if you prefer.

These hatches that I made give you some examples of polyester/ glass directly to wood with sprayed on finishing gelcoat and then with the antiskid added to gelcoat in a final process.

63305620459--3868E236-C788-4041-A1CD-8AB81C5B8D7C.jpg


IMG-7112.jpg


IMG-7217.jpg


IMG-7333.jpg


IMG-7335.jpg
 
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Dream to fish

Deck Swaby
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Wow, that work looks top notch! How long ago did you do it? Has it held up?
 
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Russo

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If that's what you want to call it
It’s fresh. I just completed them in the off season. The key no matter what for longevity will be keeping water out of the wood. Seal all of your screws and through penetrations with 4200 or the flavor of your liking.
 
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Dream to fish

Deck Swaby
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Stuff like this is why I question polyester resin on wood. Sure, the guy that originally built it may not even be alive anymore but.....

1508762-75978bcd9de93adafa71bd8de457164c.jpg
 
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Russo

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If that's what you want to call it
For sure a valid concern. Many factors that could lead up to that result though really. It looks to me like the de-lamination occurred where the wood had become wet. Obviously I can’t say if that came before or after but it
Looks like the bond is still good where the wood is dry. Really hard to say what went into the installation initially as well. That’s a pretty thin lay up by the look of it. Maybe one layer of biaxial mating? That definitely won’t help with longevity.
 
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sickcat

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IMHO you marine ply has little benefit over quality #1 douglas fir ply unless your bending it. Both use the same glue. Only real difference is in the amount of voids allowed. I did some hatches and decks on skiffs with #1 ply from Roseburg. In 4 X 8 sheet there was under inches of void total showing, If your anal about it like me I just pump some thickened epoxy into the void showing on the cut piece.
 
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starbright55

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If you're new, use epoxy for the longer working time - 30-45 minutes with standard hardener. You can get slow hardener and extend that even more.

I do use poly sometimes but with a 5-10 minute working time, you have to have everything ready and choreographed so you can move quick.
 
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plj46

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I've read that vinylester has an extremely short shelf life and there was some other negative? Maybe it was really toxic fumes? I can't remember. I've done small projects with epoxy before so I'm not going in completely blind. Just never messed with fiberglass. US composites sells epoxy resin at a price I'm OK with so why not?
Vinylester doesn't have a short shelf life if properly stored.I just did a repair for a friend and the can was over a year old.Temperature is the biggest factor in working time.If it's a hundred degrees both vinylester and epoxy will cure faster.Don't be too concerned about using it on wood.Proper prep of the wood by applying a saturation coat helps.Mix a hot batch of resin and acetone,about 50/50 mix and catalyze it hot.It soaks in and seals the wood and makes the laminations stick better.And FWIW i've never once seen a boat repair guy use epoxy on anything built with polyester/vinylester resins.It's just not necessary.Even with epoxy wet wood will become a problem.
 
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Kinaiahi61

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If you look at my post, At it again:( on the Hawaiian bloody deck section, you'll see what I did to my boat. 6 years later and solid. I used Iso resin, a tooling resin, better than marine resin, supposedly and 1708 and mat. Good luck, prep is key, chase bubbles, and be meticulous. It'll come out great.
 
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Island20

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Look up Boatworks today on youtube. Andy is a master at working all kinds of fiberglass. He also has a patreon page. I replaced the deck in my boat last year and could not have done it without his personal communication and advise. Also has discounts for patron members at on Total Boat products.
 
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Dream to fish

Deck Swaby
Jul 25, 2009
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Look up Boatworks today on youtube. Andy is a master at working all kinds of fiberglass. He also has a patreon page. I replaced the deck in my boat last year and could not have done it without his personal communication and advise. Also has discounts for patron members at on Total Boat products.
Yeah, I've watched a lot of his videos. Good stuff. Guy's gotta make a living, I get it.....but I don't think $20 a month is worth it to me. This isn't rocket science....
 
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Island20

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Yeah, I've watched a lot of his videos. Good stuff. Guy's gotta make a living, I get it.....but I don't think $20 a month is worth it to me. This isn't rocket science....
$20 is cheap considering how many thousands it would cost to have it done.
And it is very complicated if you don't know what materials and techniques.
It was well worth it to me. Just trying to help. Good luck with your project.
 
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Fearlessfiasco

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These forums might be useful to you. The whole thing is fairly dedicated to plywood epoxy sandwich boat building.

Most of the boats that people are building there just use 12oz biaxial cloth over the plywood. No mat involved.

No polyester involved at all either. All epoxy. Their stance being that poly doesn't bind with wood nearly as well as epoxy.

They also sell a decent boat building epoxy. Last time I bought some it was around $70 a gallon after shipping. It may have gone up since then.
 
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