Sundeck rebuild questions

[brian4321]

Hi all. I'm in the process of rebuilding the sundeck/ engine cover on my boat , and I need advice on where to buy marine grade plywood... I checked at my local building center and they don't carry it...also the guy doing the upholstery says I should seal the new plywood with a sealer of some kind...do you guys have any suggestions on the plywood and what sealer I should use? Thanks in advance

 

[DeepBlue2010]

If you are in US, you can get marine ply from Dunn Lumber. Also your local lumper yards, as opposed to home Depot ir lowes, can also source for you.

Some folks here suggesting exterior grade ply as an alternative to marine grade. I always used marine grade however, and I think it is the way to go unless cutting cost is absolutely necessary.

The sealer will be the fibergalssing process itself. If you are going for polyester resin, give the wood a coat of resin only with no glass and pay special attention to the edges. This coat is not meant to be a sealer. It rather meant to saturate the wood with resin so that when you start glassing, the dry wood doesnt "steel" the resin out of your glass and leave you with resin starved - a.k.a weak - laminate.

Again, dont think of you coat the wood with resin only (polyester) it will be protected. Poly resin by itself is next to useless, it will dry and chip off leaving your wood exposed.

On the bottom of the deck, apply 2 layers of csm with the seems overlapping each other.

On top of the deck, apply at least one layer of 1708.

What was the thicness of the old deck, 1/2, 5/8 or 3/4?

 

[Woodonglass]

I agree Marine Grade IS the Best but...I'm one of those that don't think it's necessary to use MG plywood in all cases and this is one of them. You can spend the extra $50 - 60 bucks if you want but Not sure I would. You still have to seal it too. This isn't Structural, It won't be exposed to the elements and if sealed properly and maintained the ext. Grade Plywood will last for decades. I've been recommending the Old Timers Recipe for sealing Plywood here on the forum for a long time and Lots of members have used it with Great Results. If I'm understanding you correctly this is an Upholstered/Padded Sundeck that also serves as the engine cover Correct??? If so there's no need to do any fiberglassing. I do a lot of upholstery work and this is what I use on ALL my plywood backer boards. (See Below) Never had any issues. If you follow the instructions to a "T" (Especially the part about finishing up with a final coat or Two of full strength Poly) and then make sure to pre-drill and use 5-minute epoxy or 3M4200 sealant to fill any screw holes that you put into the wood and the upholsterer uses SS Staples You won't have any issues with the wood.

As to the Plywood itself, If you can find Aruaco Brand Ext. Grade It's got more plys than most and very few voids. Lowe's and Home Depot in Some areas carry it. Go with the same thickness that was there. Prolly 1/2 or 5/8" Could even be 3/4" How big is it???

Got any Pics??

 

[lckstckn2smknbrls]

If you have a Menards in your area they carry marine plywood.

 

[brian4321]

Thanks for the replies.. I think I'll go with marine grade plywood, the local lumber yard can get it for me...then I'll use WOG's sealer formula...the old deck is 3/4" ...yes it is a padded, upholstered sundeck that doubles as a motor cover.. The reason it rotted is every time someone gets out of the water and walks across it, they dripped water on it and it and it got in a few bad seams..I didn't realize how bad it was till we had the foam off

 

[brian4321]

 

[Woodonglass]

Make SURE the upholsterer Covers the Foam in Plastic prior to covering it with the vinyl!!! This accomplishes 2 things. 1,) It really increases life of the foam because the vinyl has a tendency to Chafe the foam and eventually over time erode it. And 2.) I will Waterproof it and if any of the seams leak water won't get to the foam and then to the wood. Another tip Once you get it Back from the upholster. Dab some of the Oldtimers Recipe over all the Staple lines on the back to help seal all those staple holes. Also Get some 3M WaterProofing Spray like the snow Skiers use on their clothing and spray it on the seams. It will help waterproof the thread and seal the seams. Wipe em down afterwards!!!

 

[harleyman1975]

Some may not be aware of the difference in plywood. Marine grade and exterior grade use the same glue. Difference in marine grade is 1) usually 7 or more layers (3/4 ply) vs 5 in AC or CDX and 2) there are NO voids in marine plywood so it is stronger...It has not been treated with anything to make it waterproof...You need to do this yourself and WOG has as good a waterproofer as anything...poly, vinyl or epoxy. all will work only difference is cost.

 

[brian4321]

Thanks guys , this is why I love iboats forums...lots of great friendly advice.. Good to know the difference in the plywood harleyman and WOG I'll be sure to do that , thanks again guys

 

[brian4321]

One more question... Woodonglass , how exactly do you recommend predrilling the screw holes and sealing them? After the poly seal is applied? Also I have a quart of minimax helmsman urethane, so can I use that full strength for the last two coats or should I get polyurethane ?

 

[brian4321]

Sorry that was two questions

 

[Woodonglass]

What ever the screw size is i drill into the wood using a drill bit just a little smaller than the screw shank. I then use 5 min epoxy and a toothpick to coat the holes and the screws before driving them home. The Helmsman urethane will work just fine.

 

[brian4321]

OK thanks so much