What plywood to use under "marydeck" vinyl

[rolmops]

It's time to spruce up the Starcraft Islander a bit and after having found some rot in the floor boards I decided to pull the floor, replace the plywood and glue on Marideck vinyl.
In an effort to lighten up the boat a bit I want to go from glassed in 3/4 inch plywood -which rotted out in between the plies- to 1/2 inch plywood covered with the afore mentioned vinyl deck cover. The plywood will lay on foam and in the middle I will add 2 aluminum cross supports above the fuel tank. Yes, I will go on a diet as well.
This boat is trailered and covered when out of the water.
Now I have to choose what sort of plywood to use. I'm in need of suggestions on whether to use marine fir plywood, a high grade exterior plywood or "ultraplyxl" which is way cheaper than the marine stuff and used the same glue as marine fir plywood.
Also, do I to snug the floor all the way up to the transom or do I leave some drainage space which will make the water drip down onto my wooden transom?
Any suggestions and sharing of experience will be highly appreciated.
Thank you, cornelis.

 

[CrazyFinn]

I would use exterior grade plywood, glass it in (top and bottom - or at least seal the bottom with resin), and then put the vinyl on top to protect it. Without the resin/glass to seal it, it will rot faster than the original - maybe not from the top but from the moisture that will inevitably get under the floor.

 

[jbcurt00]

Rol: Fiberglass and epoxy failed and allowed the former deck to get soft? Polyester resin and glass?

Any idea what happened?

Unsealed penetrations/screw holes?

Edges werent well sealed too?

What was the deck (floor) covering that allowed some rot?

Use the best plywood you can. If that means marine, great. Exterior fir, MDO, Auraco and exterior ACX are all good substitutes that trade upfront expense for shorter expected useful life. Eventually all will succumb if left unsealed before installation or if neglected long term.

Same w sealers. Some are better then others, and some cost more.then others. Any are better then what SC used originally: None.

Crazy, not a glass boat, best practices are different for an aluminum boat. And RESIN isnt descriptive enough of a particular product. Specify epoxy resin or polyester resin when discussing resins, otherwise mistakes and misunderstandings can occur. Polyester resin alone (w out fiberglass) is worthless for any application on a boat, epoxy can be used w out fiberglass, in some cases.

 

[rolmops]

What happened?
That is a very good question. The answer is:I did not know what the heck I was doing, and acted with ignorance and gut feelings instead of trying to learn first and then act.
When I made the current flooring about three years ago, I was woefully ignorant of the different types of plywood that are available,but I did know that marine grade was outside of my budget. Instead I{ bought some regular 3/4 inch plywood and covered it with a layer of fiber resin with hardener in it and then on the top side a second layer of the same stuff ,but this time with a white coloring added. I let it dry up and installed it with rivets. After 3 years cracks started appearing in the resin covered top and the smell of rotting wood came out.But only near the back around the dog house.
I realize now that not all plywood is equal. I should at least have used exterior plywood, all the different plies had separated. In addition, I should not have used hardener because it made the resin dry up much faster and instead of penetrating into the wood,it formed a hard layer on top and it cracked allowing water in.
This time I intend to think and learn before making the next floor.

 

[jbcurt00]

, I should not have used hardener because it made the resin dry up much faster and instead of penetrating into the wood,it formed a hard layer on top and it cracked allowing water in.

What kind of resin?

Best of my knowledge, there is no product that is supposed to have hardener in it, that when used w/out hardener, is going to be of any benefit.

 

[rolmops]

The stuff you use with fiberglass.

 

[jbcurt00]

The stuff you use with fiberglass.

Polyester resin or epoxy resin. You can use glass w both, its just not required in all cases when you use epoxy.

Lets try this, pick A or B:
A: Did you use 1-2% MEKP to resin? POLYESTER

B: Did you mix the resin w a ratio of 1 to 1, 2 to 1 or 3 to 1 Resin to Hardener? EPOXY

 

[rolmops]

I remember that it was a small can of hardener. That makes me think that it was polyester

 

[jbcurt00]

And you only used what seemed like a very little bit of it per volume of resin. Plus it smelled HORRIBLE and leave a strong after odor? Then yep, Polyester.

No benefit to using it w out hardener or w out glass

Several sealing methods can be used below vinyl. Discussed at length, many many times. It can be found in most of the topics found here
http://forums.iboats.com/forum/owner...tarcraft-boats

 

[rolmops]

Thank you , I will scour those posts and hopefully I'll do it right this time.
Cornelis.

 

[ezmobee]

I personally find 1/2" decks to be too springy. Perhaps it would improve if you glassed it. I wonder if the first time you ended up with some interior grade plywood and that's why it failed so fast.

 

[Woodonglass]

If the 1/2" plywood is totally supported by flotation foam then I suspect it would be plenty firm and stable. If you decide to use the Poly resin again you MUST use Chopped strand mat with it or it will harden and CRACK allowing water to penetrate to the underlying wood layers. The CSM acts basically the same as wire mesh in concrete. It holds the hardened material together and makes cracking a lot less likely. As stated previously, Epoxy can be applied with or without Mat or Fabric and it will perform very well.

 

[rolmops]

The plywood was probably an interior because I wanted the nicely sanded sides. Another probable reason for its failure is the fact that after having glassed the plywood in ,I let it dry to be really hard and then put tension on it by bending while screwing it. That may have helped the development of the cracks.

 

[Woodonglass]

As stated All polyester resin will harden and crack if CSM is not used. It IS required. No If's, And's, or Butts!!!!

 

[rolmops]

Winter came back to town and between that and a heart attack it caused a one month delay in my project. Yesterday I bought three sheets of ACX 3/4 inch plywood and I removed the old floor.
I want to do it right this time starting with the proper sizing of the wood and with the proper curving so it sits properly along the hull. Does anybody have any advice as to how to cut the plywood ? Is the curve important or will straight lines do? The foam that I poured in 3 years ago is totally dry so that is good news. I did find out where the water that did the damage to the floor came from. It is rain water that drips into the storage areas that are on both sides. Did anybody find a solution for that problem? I'm thinking that maybe I can just glue the vinyl onto the hull so all the dripping water will stay on top of the vinyl floor and cannot get underneath the floor boards. Any other practical hints are highly appreciated. Thanks.

 

[Slager]

I'll try and answer some of your questions. How to cut plywood - use a jig saw, sometimes a circular saw will work if the curve isn't too sharp. If you don't have a good template to use, you can make one out of cardboard, foam, newspaper, really anything you have on hand that is easy to manipulate. A couple photos would help immensely for a good anser, but I suspect your deck rests on a lip and you need the plywood to go over that lip enough to rivit down.

"I did find out where the water that did the damage to the floor came from. It is rain water that drips into the storage areas that are on both sides. Did anybody find a solution for that problem?" - I'm not sure exactly what your talking about here, a photo or two may help.

 

[rolmops]

Let me clarify myself. Rain water that falls on the railing tends to drip down into the storage that is right under the railing. From there it dribbles down behind the side boards down to the floor. There it has a hard time draining away and it ends up getting into the side of the floor boards.

 

[Slager]

I would start with sealing what ever the water is getting through to get into the storage compartments. If you know where it's leaking, you can use some 3M 5200. If it is the railing, remove it and seal all screw holes when you put it back.