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Here is my vision, I would like to make a bow hatch cover for my 15' custom. I will use mahogany plywood of course but instead of just finishing it with the usual spar varnish I would like to make it have the anti slip like the existing gelcoat one that's on there now. Because i want the same build up of anti slip as the existing one, I plan on masking off an area where I want the grip area to be.I will put several coats of epoxy down in that area first, then some sand blast media or glass bead, whichever I find works best with prior testing. After I epoxy the rest of the hatch I will finish it with spar varnish for the uv protection.

Questions:
1. What is the definition of marine plywood? I understand that it is the same as regular plywood it just don't have any voids under the veneer.

2. Is there such a thing as marine grade mahogany plywood? Availability, sources?

3. I plan on using West Systems epoxy. What is the maximum time I can go between coats before the product doesn't want to bind into previous coats causing visible seams?

Your question for me is why do you want to replace a perfectly good highly sought after hatch cover? Hey, I like the look of the mahogany and enjoy working on my whaler:).

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I can get (and have) Marine Grade Mahogany 3/4" (11/16") Plywood. It has the two outside veneers with five more layers of wood within. The wood layers are less than a 1/16th inch thick, the glue layers are greater than 1/16th thick. So you are looking at 11 layers from the grain side. The full sheet cost me over $120, maybe a lot more, the receipt has long gone left me. It is a very high end exterior glued (epoxied?) piece of wood. Very tight grain on the exterior. I am holding a piece right now. How much do you need? I have a couple of squares hanging around. I stored my pieces in my basement with a dirt floor and even though I kept it off the ground, a magnet for mold/mildew. I have to spray it with a chlorine solution and let it dry in the sun before I work with it. Was recommended by the local boat carpenters as the correct way to go if using plywood but I never asked the big difference between it and regular exterior plywood. I do know from structural concrete forming, the more veneers in the plywood sheet, the stronger and higher quality the material.
Garris

edit, I looked closer at the other layer within the wood (that I referred to as glue) and it appears to be a different variety/species of wood than the other layer. Not epoxy/glue filler.

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I contacted the lumber company where I purchased my marine mahogany. To answer Huck's questions. Yes, the telling feature in marine plywood is absolutely no voids inside the plywood. Any void would trap moisture and ultimately delaminate the wood. All the layers are select. Mahogany, being a hardwood, makes it more expensive. Each layer is cross grained (one goes left to right, the next up and down) as it is fabricated leaving it more stable by preventing splitting at the grain. Exterior glue similar to standard exterior glues for plywood.

Hope this helps.

Garris

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I recall folks using rock salt or a similar material to make a clear no-skid surface, by applying it to wet epoxy or varnish. Allow the epoxy to kick, and remove the salt.
http://forum.woodenboat.com/showthread.php?2098-Sugar-For-Non-Skid
An interseting idea...
Pete

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From Wikopedia :

Marine plywood

Marine plywood is manufactured from durable face and core veneers, with few defects so it performs longer in both humid and wet conditions and resists delaminating and fungal attack. Its construction is such that it can be used in environments where it is exposed to moisture for long periods. More recently, tropical producers have become dominant in the marine plywood market. Okoumé from Gabon is now the accepted standard for marine plywood, even though the wood is not very resistant to rot and decay. Each wood veneer will be from tropical hardwoods, have negligible core gap, limiting the chance of trapping water in the plywood and hence providing a solid and stable glue bond. It uses an exterior Water and Boil Proof (WBP) glue similar to most exterior plywoods.

Marine plywood can be graded as being compliant with BS 1088, which is a British Standard for marine plywood. There are few international standards for grading marine plywood and most of the standards are voluntary. Some marine plywood has a Lloyd's of London stamp that certifies it to be BS 1088 compliant. Some plywood is also labeled based on the wood used to manufacture it. Examples of this are Okoumé or Meranti.

Marine plywood is frequently used in the construction of docks and boats. It is much more expensive than standard plywood: the cost for a typical 4-foot by 8-foot 1/2-inch thick board is roughly $75 to $100 U.S. or around $2.50 per square foot, which is about three times as expensive as standard plywood.

Timber Trades Definition :

http://www.ttf.co.uk/article/marine-p...s-137.aspx

Everything you ever wanted to know about plywood :

http://www2.wisd.net/it/PLYWOOD.htmLYWOOD.htm

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Real BS-1088 marine plywood in 18mm (3/4") is 11 plies thick. It's probably more expensive than solid African Mahogany.

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The 18 mm thick (3/4"") measures just shy of a full 3/4" thick. Actual measurement is closer to 11/16 ". However, is referred to as 3/4" when ordering. You also need to specify mahogany. Come in different faced veneers.
Garris

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sorry to derail this post, but I didn't want to start a new thread about the same topic...

gcuba- I'm having a hard time locating a small piece of marine ply in my area. Any chance you'd be willing to sell one of those extra pieces you have laying around??

I'm not sure of the measurements off hand but you can see the spot that I need to replace in the pic below... 14x12 would be more then enough for me.

Thanks

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Huckelberry, I have a small piece of 3/8 Okoume BS1088 plywood I could send to you so you can see what it would look like with your finish of choice. Email me your address and I'll get out to you. My email add. is in my profile. You can see what it looks like with a couple coats of epoxy and the first coat of Interlux Schooner varnish on my personal website, the small boat "Amy June"

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The price for a full sheet of 3/4 Marine Mahogany is $210 after tax. Let's get the measurements to get a square footage count.
Garris

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Huck have you considered making a hatch cover that is similar in design to the Montaukhttp://www.whalercentral.com/images/p...%20016.jpg? It doesn't have anti-skid but the design may lend its self to being relatively "non-skid".

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I would second the above recommendation, and here is where I would make the purchase:

http://www.blackduckgallery.com/WOODP...PARTS.html

Even if you want a plain mahogany plywood cover, I'm sure you could have it done by Walter.

Buying from a fabricator like this avoids having to source large sheets of marine plywood yourself, and in the end is probably no more expensive.

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Huck, what's the overall concept? Just the locker or other stuff too?

Check with local shipwrights in your area, everyone near me had major stock in mahogany. The older the wood the prettier it seemed. One of these days we got to get together, the rub rail on my boat looks faux. They even have their stashes of the really nice peices if you ask. I think my wood used on the rub rails was twenty years old, stashed up in the rafters of his shop.

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I originally contacted Black Duck Gallery. A very nice fellow, his gallery of product is beatiful. His shop was down from the hurricane and I wanted rod holders. $150 for a set of four rod holders (with teak block). $50 less than the sheet I purchased (minus teak). Decided to fabricate my pieces myself. I had more uses of the mahogany plywood (rod holders, cabinet door, reinforcement for cuddy's cabinet which is holding auto pilot/hydraulics for jack plate, steps, splash board). I burned up two sheets and keeping an extra dimensional length for splash board replacement. If varnished correctly (something I neglected, now have none to spare) great material to have around.

Garris