Marine Plywood
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=10889
Printed Date: November-17-2024 at 12:59am
Topic: Marine Plywood
Posted By: robman
Subject: Marine Plywood
Date Posted: June-17-2008 at 7:51pm
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I have repaired the stringers in my 86 ski nautique. I plan to use handi foam and then use Marine Plywood. My question is how do I seal the marine plywood after I attach it to the repaired stringers. Thanks in advance.
-rob |
Replies:
Posted By: Tim D
Date Posted: June-17-2008 at 8:09pm
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I would use treated plywood. Marine plywood is too high of quality to use in a floor. I put 9 coats of polyurethane on the top and edges of mine and sealed all the joints with 30 year silicone. ------------- Tim D |
Posted By: 8122pbrainard
Date Posted: June-17-2008 at 8:30pm
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Sorry Tim but I have to firmly disagree on the treated. Several other have made comments on not using it as well. The chemicals screw up the epoxy bond (even worse with polyester resin)
Rob, Regular exterior ply is made with the same waterproof glues as marine ply is. The difference is, marine because it is commonly used for demanding structural applications has a very high standard for voids in the center plys. Go with exterior. Seal all sides with CPES after making all cuts. Bed the ply down to the tops of the stringers with a thickened epoxy. Use weights to hold it down or screws temporarily. Remove the temporary screws and seal the holes with epoxy. Give the ply another coat of regular epoxy or even better, a layer of glass cloth. Hopefully you have been using epoxy resin. Who's brand? The only caulking needed would be on through hulls like the cooling water suction strainer. Stick with 3M 5200. It's a marine adhesive sealant with superior adhesion and sealing over any silicones. http://www.jamestowndistributors.com/userportal/show_product.do?pid=1268&familyName=Smiths+Warm+CPES+Epoxy - CPES ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: robman
Date Posted: June-17-2008 at 8:51pm
| Thanks for the response... I have been using elmers brand (from lowes) expoxy resin and cloth for all fiber glass reqairs. I have put 3 coats on all repairs. |
Posted By: 8122pbrainard
Date Posted: June-17-2008 at 10:26pm
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Rob, What do they have for a filler (thickening)? Have you been using any - say for filleting? ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: eric lavine
Date Posted: June-17-2008 at 11:40pm
| the treated wood needs to breath and the reaction is called popping, just like thinner pop, it is the chemicals trying to get out of a sealed area, and this also causes things not to stick to it. a guy did his floors with treated then coated with resin and the dried resin was rolling right off of the wood. it did not adhere to the treated wood. marine ply is twice the price of normal and is not needed for floors or structural, make sure you scuff the surface of all woods for adhesion promotion |
Posted By: Tim D
Date Posted: June-18-2008 at 1:43am
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Pete, the plywood I used was salt treated. It's now 10 years old and I haven't had any problems with it. I'm pretty sure resin would stick to it with no problem. Before I did it, I talked to an old guy that has worked with boats his whole life. He told me if you were to use untreated wood coated with resin, all it would take is one crack to form to let water in the wood and hold it in, thus rotting the floor. So I went with the treated and coated it with poly. ------------- Tim D |
Posted By: 8122pbrainard
Date Posted: June-18-2008 at 7:49am
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Tim, I'm glad that so far the treated hasn't given you any problems. Well, I'm a old guy too that has worked on boats all my life and primarily wood! The cracking in the ply is checking when it dries below the moisture content of when the plywood was made. Fir ply is especially prone to check and treated will do it too. My understanding of the development of the CPES is the checking was one of the primary purposes of it's development. The checking has been a problem since Higgins started making ply boats. (and of coarse CC after Higgins)
Structural cracking is a whole different problem. Typically, it may be from lack of support in a area or flexing of the hull when there isn't enough glass/hull thickness. The more brittle polyester resins are more likely to crack as well. It's the reason we see spider cracking in gel coats. When this happens next to wood, the CPES is a good solution to that problem too. With the CPES and then epoxy, a bending or flexing will tear wood before the bond breaks. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: BuffaloBFN
Date Posted: June-18-2008 at 8:52am
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I'll throw in my .02 on the CPES. It's a pleasure to work with except for a strong odor. It applies easily and has good working time. I put 1 coat on a few scrap pieces and cut them open the next day. The 'soak-in' factor was excellent...it seems to plasticize the outer part of the wood.
Good stuff. ------------- http://correctcraftfan.com/diaries/details.asp?ID=2331&sort=&pagenum=12&yrstart=1986&yrend=1990" rel="nofollow - 1988 BFN-sold "It's a Livin' Thing...What a Terrible Thing to Lose" ELO |
Posted By: 8122pbrainard
Date Posted: June-18-2008 at 11:46am
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Rob, Do you know if the Elmer's epoxy is new? I have never run across it and because I do like their products did a search. I couldn't find anything on it at the Elmer's glue site or at the Lowes site. Any help with getting me information? I'm still interested if they have any fillers to go in it. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: lewy2001
Date Posted: June-18-2008 at 12:35pm
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Thanks for clearing up what CPES was. It was a question I was going to ask you fibreglass guys.
The removable rear floor piece in my 89 is trash. I was going to replace it with what we call formply here in Aus it is 16mm thick with a plastic like coating on both sides. This coating would make it fairly water resistant would coat edges with a CPES equivalent.  
Pics of formply used to replace floor in older Aus ski boat. It is a 26" span in the 89 ski. Do you think 16mm (approx 5/8") is thick enough?  ------------- If you're going through hell, keep going http://www.correctcraftfan.com/diaries/details.asp?ID=2999" rel="nofollow - 89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
Posted By: BuffaloBFN
Date Posted: June-18-2008 at 12:44pm
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Lewy, is it white melamine on both sides with partical board in between? ------------- http://correctcraftfan.com/diaries/details.asp?ID=2331&sort=&pagenum=12&yrstart=1986&yrend=1990" rel="nofollow - 1988 BFN-sold "It's a Livin' Thing...What a Terrible Thing to Lose" ELO |
Posted By: robman
Date Posted: June-18-2008 at 12:48pm
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Pete, here is the link on the Elmer's fiberglass I have been using. Let me know what you think.
http://www.elmers.com/products/product/product_page.asp?pCode=E770 Let me try to recap everyones advice; 1.)Marine plywood (MP) is good? 2.)Attach MP to repaired stingers with a good thick batch of resin. 3.)Put a layer of glass over the entire floor. Does this sound like a plan??? |
Posted By: lewy2001
Date Posted: June-18-2008 at 1:03pm
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Buffalo
It is a plywood not Kitchen cupboard shelving. They actually use it as formwork in concrete pours. It can be used numerous times. I have only seen it in 16mm. Just dug my old piece out of trash. It is 20mm thick looks like they cut the inspection hole out with someone's falsh teeth.  ------------- If you're going through hell, keep going http://www.correctcraftfan.com/diaries/details.asp?ID=2999" rel="nofollow - 89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
Posted By: 8122pbrainard
Date Posted: June-18-2008 at 1:11pm
Rob, 1. MP is not needed. go with exterior as stated. 2. yes, use a filler/thickener for high build areas such as fillets or where there may be some gaps like bedding/glueing down the ply to the stringers. 3. A layer of glass over the floor is preffered. Now, the Elmer's is polyester resin and not epoxy (the reason I couldn't find it!). I would not recommend it. Go with a epoxy such as Mas or West. You can do a search. Greg I'm sure can chime in with a link to U.S. Composites. They will also have the fillers to add to the base resin. West is available at marine supplies. Polyester isn't as strong but the biggest reason I don't recommend it is it is hygroscopic. Not really a good thing around water!!! Boat hulls are made with it because it is less expensive. Lewy, Interesting project. Keep the pictures coming. I too (like Greg) am skeptical about the board/sheet goods you are describing. If you are going to coat the edges which may not bond to whatever is on the surface creating a potential leak, just go with plywood completely coated. Also, to make the post narrower and easier to read, go back in and edit your post. By using the "enter/return key between your pictures, it will stack them from top to bottom instead of side to side. Thanks ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
robman wrote:Posted By: Hollywood
Date Posted: June-18-2008 at 1:21pm
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I believe our removable floor section is just treated 3/4" plywood. It gets soaked every time out, and still holding up just fine. Not sure if it's original, but it works. We also have redone the floor on the pontoon boat with treated plywood both times, and as long as it can breath and dry out it will last many years. ------------- |