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Author Topic:   Marine grade vs. Outdoor grade plywood

jbcarter posted 05-14-2003 01:28 PM ET (US)
Hello again. I've decided to build the console out of 3/4" ply for my father's Whaler. However I was wondering if I need to go with marine grade ply or if outdoor will suffice? I've been told the only difference is that marine grade is guaranteed to not have voids in the inner plys. Does anybody have experience or opinions to share.
Thanks again.Justin.
acassidy posted 05-14-2003 01:46 PM ET (US)
Marine grade is usually Douglas fir with very few, or no voids, A/A. You can buy AC exterior plywood Douglas fir A/C or A/B or B/C and it will have same wood and same glue. Do not use Pressure treated pine unless you really let it dry out, because resin will not stick to it and warps badly, good for BBQ decks though. Resin love Douglas fir, and fir is very light and strong. Good luck Archie
T Party posted 05-14-2003 01:47 PM ET (US)
I built a Payson Tortoise dinghy (see www.instantboats.com) from A/C exterior fir plywood (ACX), and it has held up quite well for three years now. According to Payson's book "Building the New Instant Boats" the glue used on exterior ply is the same as on marine grade ply, but the ACX is more likely to have voids. I didn't have a problem with voids, but I tried to choose the wood very carefully (minimum of "footballs" and voids). Avoid Lowe's/Home Depot type places (their plywood is absolute garbage, IMNSHO) and pay a bit extra for good stuff.
If I were building a console for a Whaler, however, I would use Okume (mahongany) marine plywood because it looks so much nicer finished bright. If you are going to paint the console, then maybe the fir ACX would be OK.
My $.02
NEVER SCARED posted 05-14-2003 03:15 PM ET (US)
I dont get it, how does the absence of "voids" prevent rot?
Montauk posted 05-14-2003 03:46 PM ET (US)
It takes the same time to build a console from either plywood, marine or fir exterior A/C. The fir plywood will need the edges filled where ever voids show to prevent water intrusion. The other problem with fir is it will weather check if left in the sun with just paint or varnish on it. My opinion is if you do not have access to marine ply, fir will work but will need extra care and work when finishing. Building a console is a labor intensive project, why not use the best materials and only do it once?
Chesapeake posted 05-14-2003 03:48 PM ET (US)
jb:
Are you building a new style console or an old style console? Are you planning to paint, glass or stain and clear finish the wood? Here's why...
1) 3/4 ply is VERY heavy. Whaler used to build the Nauset, etc from 1/2" ply and bolster the corners with thicker mahogany. Part of the reason, I was told, is to minimize weight.
When I rebuilt, I used 3/4" for the base of a Nauset console, but kept 1/2 for the upper.
2) If you are planning on painting, recognize that the grain of fir will telegraph right through the finish. It is not pretty. If you are going to stain and clearcoat, fir is not the nicest looking grain. For these reasons, if you are sold on using plywood, I would strongly encourage you to get mahogany veneered marine ply.
If you are going to glass it, the finish will look fine with regular mahogany. Then again, if you glass you really don't need the added support of 3/4" material.
3) Before you finish, would encourage you to apply 2 or 3 coats of West Epoxy on all surfaces, especially the endgrain material that touches the deck. This will a) waterproof your work; b) will harden the surface; and c) make the surface smoother in preparation for paint.
jbcarter posted 05-14-2003 05:50 PM ET (US)
Chesapeke- I am planning on making the console very similar to the Nauset console. From what I've learned in this post so far I've decided to go with the marine grade mahogony. Since I'm going with mahogony I'd really like the grain and color of the wood to shine through so I'll probably go with a stain and clearcoat. I hadn't thought much about the weigh issue, using 3/4 and 1/2 seems to make more sense. Thanks for the advice.
acassidy posted 05-14-2003 07:13 PM ET (US)
NEVER SCARED, the voids in non-marine grade do not have anything to do with preventing rot. Has to do with strength and what Montauk said about filling voids. Making a wooden boat or console will be very hard will voids in the wood. Could imagine pulling to pieces together to make a bow V and having voids in the end to be epoxied together. 綌 mahogany ply sounds good for the project. Archie
Chesapeake posted 05-15-2003 11:24 AM ET (US)
jb: You mentioned you were building a Nauset like console. Does that also mean you are planning on using the twin 12 gallon gas tanks stored underneath?
If so and if you do use 3/4" for the lower console sides, recognize that you will have to make your console hold down cleats each about 1/4" narrower front to back. Why? You really have to preserve the space in between the cleats to have enough room for the tanks and still have access to the tunnel.
I made mine only 1/8" narrower and it has been a problem. I am thinking of having a local machine shop make me a set from aluminum or high density phenol.
carlz posted 05-15-2003 05:29 PM ET (US)
I agree with 3/4" for the base for strength; the base takes all the stress, especially with the front seat.
I suspect that BW's choice of materials hinged more on the economies than the qualities of the materials. Half inch on the base was clearly a poor choice, witness all the bowlegged bases that have had to be rebuilt or replaced.
If I were to do mine over I would use more solid wood in the top section. The solid wood looks much, much better and the top is what shows the most.
Chesapeake posted 05-16-2003 10:53 AM ET (US)
carlz: Remember sending along the plans, but never got a chance to see the final product. Would love to see any pics of your new console.
Also agree that building from solid mahogany might be better looking, but two things would concern me. Solid wood is less dimensionally stable and I would be concerned about joints opening up and disrupting the finish. Also would imagine that pound for pound, the ply probably provides more strength.
Having said that, my brother built a new 71 Outrage console of solid mahogany (has the teak and holly look) and you are right. It is much prettier than ply.
Cicada posted 05-16-2003 10:11 PM ET (US)
I found out that there are two different types of Marine Mahogany Plywood (in the Detroit area anyway). One is called Okume (Okoume) and the other is Sapele. Okume is a flat sawn veneer and Sapele is a quarter sawn veneer. Okume should probably be stained to match solid mahogany where the Sapele has the grain and color that matches the solid wood. Prices here for half sheets are 75 for the Okume and 90 for the Sapele. The finished Sapele seems to have alot more depth than the Okume. I agree that if you're going to spend the time on the project get the best materials that you can. You'll be happier with the finished product. Good Luck.
Paul

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Author	Topic: Marine grade vs. Outdoor grade plywood
jbcarter	posted 05-14-2003 01:28 PM ET (US) Hello again. I've decided to build the console out of 3/4" ply for my father's Whaler. However I was wondering if I need to go with marine grade ply or if outdoor will suffice? I've been told the only difference is that marine grade is guaranteed to not have voids in the inner plys. Does anybody have experience or opinions to share. Thanks again.Justin.
acassidy	posted 05-14-2003 01:46 PM ET (US) Marine grade is usually Douglas fir with very few, or no voids, A/A. You can buy AC exterior plywood Douglas fir A/C or A/B or B/C and it will have same wood and same glue. Do not use Pressure treated pine unless you really let it dry out, because resin will not stick to it and warps badly, good for BBQ decks though. Resin love Douglas fir, and fir is very light and strong. Good luck Archie
T Party	posted 05-14-2003 01:47 PM ET (US) I built a Payson Tortoise dinghy (see www.instantboats.com) from A/C exterior fir plywood (ACX), and it has held up quite well for three years now. According to Payson's book "Building the New Instant Boats" the glue used on exterior ply is the same as on marine grade ply, but the ACX is more likely to have voids. I didn't have a problem with voids, but I tried to choose the wood very carefully (minimum of "footballs" and voids). Avoid Lowe's/Home Depot type places (their plywood is absolute garbage, IMNSHO) and pay a bit extra for good stuff. If I were building a console for a Whaler, however, I would use Okume (mahongany) marine plywood because it looks so much nicer finished bright. If you are going to paint the console, then maybe the fir ACX would be OK. My $.02
NEVER SCARED	posted 05-14-2003 03:15 PM ET (US) I dont get it, how does the absence of "voids" prevent rot?
Montauk	posted 05-14-2003 03:46 PM ET (US) It takes the same time to build a console from either plywood, marine or fir exterior A/C. The fir plywood will need the edges filled where ever voids show to prevent water intrusion. The other problem with fir is it will weather check if left in the sun with just paint or varnish on it. My opinion is if you do not have access to marine ply, fir will work but will need extra care and work when finishing. Building a console is a labor intensive project, why not use the best materials and only do it once?
Chesapeake	posted 05-14-2003 03:48 PM ET (US) jb: Are you building a new style console or an old style console? Are you planning to paint, glass or stain and clear finish the wood? Here's why... 1) 3/4 ply is VERY heavy. Whaler used to build the Nauset, etc from 1/2" ply and bolster the corners with thicker mahogany. Part of the reason, I was told, is to minimize weight. When I rebuilt, I used 3/4" for the base of a Nauset console, but kept 1/2 for the upper. 2) If you are planning on painting, recognize that the grain of fir will telegraph right through the finish. It is not pretty. If you are going to stain and clearcoat, fir is not the nicest looking grain. For these reasons, if you are sold on using plywood, I would strongly encourage you to get mahogany veneered marine ply. If you are going to glass it, the finish will look fine with regular mahogany. Then again, if you glass you really don't need the added support of 3/4" material. 3) Before you finish, would encourage you to apply 2 or 3 coats of West Epoxy on all surfaces, especially the endgrain material that touches the deck. This will a) waterproof your work; b) will harden the surface; and c) make the surface smoother in preparation for paint.
jbcarter	posted 05-14-2003 05:50 PM ET (US) Chesapeke- I am planning on making the console very similar to the Nauset console. From what I've learned in this post so far I've decided to go with the marine grade mahogony. Since I'm going with mahogony I'd really like the grain and color of the wood to shine through so I'll probably go with a stain and clearcoat. I hadn't thought much about the weigh issue, using 3/4 and 1/2 seems to make more sense. Thanks for the advice.
acassidy	posted 05-14-2003 07:13 PM ET (US) NEVER SCARED, the voids in non-marine grade do not have anything to do with preventing rot. Has to do with strength and what Montauk said about filling voids. Making a wooden boat or console will be very hard will voids in the wood. Could imagine pulling to pieces together to make a bow V and having voids in the end to be epoxied together. 綌 mahogany ply sounds good for the project. Archie
Chesapeake	posted 05-15-2003 11:24 AM ET (US) jb: You mentioned you were building a Nauset like console. Does that also mean you are planning on using the twin 12 gallon gas tanks stored underneath? If so and if you do use 3/4" for the lower console sides, recognize that you will have to make your console hold down cleats each about 1/4" narrower front to back. Why? You really have to preserve the space in between the cleats to have enough room for the tanks and still have access to the tunnel. I made mine only 1/8" narrower and it has been a problem. I am thinking of having a local machine shop make me a set from aluminum or high density phenol.
carlz	posted 05-15-2003 05:29 PM ET (US) I agree with 3/4" for the base for strength; the base takes all the stress, especially with the front seat. I suspect that BW's choice of materials hinged more on the economies than the qualities of the materials. Half inch on the base was clearly a poor choice, witness all the bowlegged bases that have had to be rebuilt or replaced. If I were to do mine over I would use more solid wood in the top section. The solid wood looks much, much better and the top is what shows the most.
Chesapeake	posted 05-16-2003 10:53 AM ET (US) carlz: Remember sending along the plans, but never got a chance to see the final product. Would love to see any pics of your new console. Also agree that building from solid mahogany might be better looking, but two things would concern me. Solid wood is less dimensionally stable and I would be concerned about joints opening up and disrupting the finish. Also would imagine that pound for pound, the ply probably provides more strength. Having said that, my brother built a new 71 Outrage console of solid mahogany (has the teak and holly look) and you are right. It is much prettier than ply.
Cicada	posted 05-16-2003 10:11 PM ET (US) I found out that there are two different types of Marine Mahogany Plywood (in the Detroit area anyway). One is called Okume (Okoume) and the other is Sapele. Okume is a flat sawn veneer and Sapele is a quarter sawn veneer. Okume should probably be stained to match solid mahogany where the Sapele has the grain and color that matches the solid wood. Prices here for half sheets are 75 for the Okume and 90 for the Sapele. The finished Sapele seems to have alot more depth than the Okume. I agree that if you're going to spend the time on the project get the best materials that you can. You'll be happier with the finished product. Good Luck. Paul