Glass reinforced plastic as decking material?

[WTL]

Hello yall.

I think we all are always looking for better decking materials given the expense of aluminum and drawbacks of plywood.

I have a full plywood deck that I like, but it already is trying to weather and its heavy.

I saw in Home Depot recently something that really has my attention - 4'x8' sheets of glass reinforced plastic for about 30 something a sheet. I was wondering if anyone has considered this as a decking material when combined with a lot of extra support.

What I am thinking is the finish is very similar to the finished look on many bay boats, it looks like it would be easy to clean, and if one could figure a procedure for backing it to give it more rigidity, I think it might last.

My ideas are either to use ultra thin plywood and coat it with resin, then attatch the glass reinforced plastic to that with 3M 5200 or take my existing plywood deck, drill it with 2" holes all throughout it to gut the weight, then 3m to that. Anything to give it rigidity, though...

But nagging me is the thought that I havent heard of anyone else do this. So what are yalls thoughts? What am I missing that can go wrong, before I start tearing into my deck?

 

[huntinfool]

I wouldn't use 5200 to try and attach this to a piece of plywood. I have done something like this in the past and the 5200 just will not spread out and will leave it lumpy. However if your really wanting to do this your on the right track. Just sand the back of the FRP and then use polyester resin and mat and glass it to the plywood.

I would offer a suggestion, if you drill holes through the wood the FRP will likely want to crack around the holes over time and from being walked upon. Now using a 1/4 to 3/8 sheet of ply and adding the FRP might work, but by the time you bond the FRP to the ply it will be heavy.

 

[huntinfool]

Also if you bond two FRP pieces together with mat and resin it is very strong. That laid over a 1/4" ply would have almost the same weight, but would be very strong. If it was braced about every 8-10" Perhaps even as much as 12-14" I believe that it would be fairly strong. But the ply is still the weak link, unless coated with resin or epoxy. (You could use epoxy to bond FRP and then coat the wood and that would work too)

 

[Rat]

Why not just use the plywood with fiberglass on top. It would probably weight less and there are not several materials to form a bond. I used 1/2 ply with 12 oz Biax and it is plenty strong, no deflection at all. When you coat the ply with epoxy it will never weather, the fiberglass on top will give you the "look" you want, it will be lighter and quicker than trying to laminate FRP, mat and ply. Most FRP isn't UV resistant either.

 

[huntinfool]

Ply wood coated with mat and resin is still heavy. And you still have plywood. Even if you take very good care and make sure every part of the wood is protected and that every screw is sealed there is always a chance that the wood will get wet and rot. I've seen it too many times.

I think that there are several other choices for a floor that would weigh less and would last just as long.

 

[Rat]

The only reason I could see to using FRP over ply would be to have a nice fair surface easily, and not a bad idea now that I think about it; but you still gotta paint it for UV protection. But again, you still have the ply, and you need to pot every screw hole to keep water out.

What would you use for decking huntinfool? Honeycomb, foam core composite? I used honeycomb on a livewell build once and it worked great, but I got it free. Honeycomb is expensive, Nidacore runs $110 a sheet! And you still gotta glass it and everything...

 

[huntinfool]

If he is talking about using what I think he is, he is talking about a shower stall material. They already have a gelcoat on them and they are textured. They shouldn't need any UV protection. But again it is just an opinion.

I am looking at several different options.

The first for me would be Coroplast. They make it in several different mil. thicknesses. I don't know what thickness you would need to stand on, but it would be forever...I think. (not sure about UV breakdown)

I had another product lined out, but once I found the price I had to back down.

You could get a piece of 1/4 ply and glass both sides and it would be very strong, especially if used for a floor with foam underneath and across ribs.

I think that there is a plastic product out there that would last and would be plenty strong and UV resistant...I just need to find it.

 

[RBuffordTJ]

I think that there is a plastic product out there that would last and would be plenty strong and UV resistant...I just need to find it.

Ever heard of Durabak? I have a gallon here about to coat my plywood decking and inside of my boat walls.

Bufford in Orlando

 

[Rat]

I have some of the Coroplast products, You can see it in my build thread in the first pictures; I used it to build my templates for the decks/frames/transom. I have the 3/16" sheet, Plastiboard I think it is, good for templates but I wouldn't use it for anything structural. Do they make heavier weights of it, maybe one designed for load bearing?

We used FRP in John Wayne showers overseas, it didn't last very long before it started to turn yellow and then it would chip if bent pretty good and leave the little fibers sticking out. It just didn't perform like we had hoped. We were trying to make a quick set up/tear down shower that could be hauled in 2.5 tons without the aid of a forklift. We ended up using canvas from old tents...

I have seen boats build from HDPE sheets (not rotomold) and PET. The PET one was pretty cool. The one made from HDPE looked like a freak show on the water. Both ended up heavier than a wood core composite boat by the same designer. Both can be made with UV stabilizers in them, although HDPE less so, that's proly where I would be looking. But as you already know, to get the same structural specs from either one would be heavier than 1088 marine ply/glass and not have the elastic characteristics (that's what the guy that built them said anyway). I actually rode in the HDPE boat, you could almost see through the bottom, but it was a clunker.

I helped a friend apply the Marine Durabak to his 18' Triton, that's good stuff. We used about 2.5 gallons for 2 coats. We weighed the cans before we applied it and I think they were right at 10.5 pounds per 1 gallon can, so maybe 8-9 pounds per applied gallon.(?) Pretty heavy for a top coat, but it has lasted three seasons so far with not a sign of deteriorating. It was definitely cheaper than removing the factory paint/non skid and re-priming and painting. It is Blue on a White hull and we left white water channels, looks sharp. Better than the all white from the factory. If weight isn't a concern I would use it without hesitation again. I fished out of it in the Gulf last Summer, very comfy to stand on and not slick at all.

 

[huntinfool]

Yes they make the coroplast in different thicknesses. I have seen 1/4 all the way up to 1/2. I just haven't actually seen it in my hands to know about the strentgh issue. Wood with glass over is fine. But after being in this business for as many years as I have you just can't get past the part where the wood will eventually rot. It might be ten years or more...but it will get wet somehow and rot. As far as price it is by far the cheapest and that is why most boat manufactures us it, because it is so cheap.

 

[WTL]

I appreciate the thoughts and comments. Several minds are always better than one for this sort of thing.

I didn't consider the idea that the FRP would wear around the holes if I turned my deck into swiss cheese and used it as support. I guess that idea is out.

The only reason I could see to using FRP over ply would be to have a nice fair surface easily

Thats one of the main ideas. Perhaps I should go into a little detail about what I have first.

Its a 14' v hull with a high deck comprising the front 65% of the boat and a center console. The deck is made from 1/2" ply, coated in glass but its ugly looking and water has gotten underneath and warped it around the hatch lids. Its all supported by 2"x4"s and I have a stringer made from an old sign post that needs to go. I basically think I used to big of materials in every phase of the deck and supporting structure and want to go lighter without aluminum. (I kinda like the cloroplast idea, but I'm not sure how strong that would be either)

The boat is just too heavy when its got two people. Plus I have rethought how and where and what type of hatches I would want.

I still kinda like the idea of the FRP, only with 1/4 ply backing it with lots of resin thrown in to sorta laminate the two together. (it would be nice if they made a heavier grade of FRP) Instead of using the 5200 to glue the thing down, I will resin it down...but the 5200 could be used to fill gaps and transitions as 1 piece of FRP isn't large enough - sorta use the 5200 like a high grade caulk.

So, after think out loud - thats now my idea, guys, tell me why you think it might not work or what I should do differently.

 

[huntinfool]

The product I'm talking about comes in a 4x8 sheet. That should be enough to do your deck. If your planning on glassing it to ply then you shouldn't need the 5200. Just fill any gaps with resin and that will seal it. You can even sand it smooth afterwards. Just remember to sand the FRP so the resin will stick. I would glass the entire ply board and make sure that there are not any openings. Remember that resin alone has no strength. You need to have the glass to have strength and the more resin you use the weaker it is. I'd seriously consider using some sort of aluminum bracing. I've seen several on here who have done that and they don't seem to have any issues. Very light weight.

Good luck!

 

[Rat]

That sounds like a good plan. Lay down a nice mat of glass and while it is still tacky set the FRP. I would put down resin (coat the wood), layup mat and saturate with resin, add a weave fill layer of thickened epoxy and set the FRP right on that. That would give you a nice fair surface pretty quick. You will need glass like huntinfool said for the strength.

You can also use quick fair instead of the last step of FRP. After you put down the weave fill layer of resin add a round of quick fair and smooth it all out. I'm not trying to talk you out of the FRP, but if it were me I wouldn't add another lamination when glass and fairing compound would do the same thing. It is more sanding tho without the FRP.

I am going to build a portable livewell and I think I will try using FRP to see how it works. I saw it used one time in a Dory in a livewell/cooler, but on the inside.

I still think you may need some non-skid or something on the FRP; it may be slick when it gets wet.

 

[huntinfool]

I built an insulated fish box in a 26' wellcraft. The customer wanted to be able to put a bunch of ice in it and have it last a bit, along with some big fish that he would spear off shore.

I took two 4x8 sheets of the FRP and sanded one side on each one. Then I layed a layer of mat and resin and layed the other one on top. Then I used a 4x8 plywood on top with old batteries to hold it down until the resin set up. After that was set I cut the pieces to make the fishbox, in this case they were 6.5'x15x15. I used one layer of the doubled FRP for a base then layed insulating foam (2 layers of 1/2") and then another layer of the FRP. I continued this all the way around until the box was complete. I glecoated the inside white and added a drain and plug.
Now mind you this was all underneath his floor. Luckily I was redoing his stringers and had the room. But I don't think I would try it again if I didn't have the access. So far he said it works like a champ.

 

[fish fishman]

THERE IS THIS PRODUCT CALLED GATORBOARD TWO PIECES OF PLASTIC WITH PRESSED FOAM BETWEEN THEM LOOKS REALLY STURDY I HAVEN'T TRIED IT YET IF ANY BODY TRIES IT PLEASE POST THE RESULTS