using CDX for boat floor

I am replacing the floor in my aluminum boat with 3/4" CDX plywood. Because the CDX will self-destruct when subjected to water, I need to seal the wood completely. The next step would be to apply marine carpet adhesive to certain areas (390 from AAT), and then marine grade carpet. Lastly, the carpeted floor panels are screwed to the aluminum supports in the boat.

The problem I have is what to seal the wood with. I need something completely water-proof, but it must not react with the water-based glue used to hold the CDX plywood together, and the 390 carpet adhesive must adhere to this sealant.

Any suggestions for a sealant? :?:

 

keeping in mind that the carpet adhesive will adhere to sealant on the cdx and not the actual plywood a complete bond betwwen sealant and cdx is extremly important. I would look into west system epoxy for compatibility. I have never heard of any reaction problems with common glues or sealers with glues used in plywoods. Good luck.

 

If you count the cost and labor of sealing cheap plywood, pressure treated may be cheaper.

 

Basic points...

Hi Guys,
Please don’t think of me as patronizing, as I am sure you are already aware of the following points.

1. Carpet in a marine environment will retain water and encourage mildew, rot, and material deterioration in almost every case. I would strongly advise having a removable option so the carpet can be dried and aired easily. Marine grade carpets are no exception.

2. When sealing a plywood esp. floor boards, attention should also be given to the fixing holes. These should not be drilled as an after thought but rather calculated, drilled and then sealant applied inside the hole. If this is not done then you will find that water will quickly access all the layers of ply via the fixing hole and the sealing exercise will have been in vain.

3. Using stainless steel fixing screws on a aluminum boat is not the ultimate solution. The different metals will have a electrolysis reaction with each other and cause the aluminum to corrode. Where this situation is unavoidable it is best to use an anti-corrosive sealant on the screws, such as Tef-gel or other specifically designed products.

Hope this is useful,

DanMarine

 

I Echo Dan's comments on the carpet.

A 1 1/2 gallon kit of epoxy should seal it up well. Remember about sealing any drilled holes. I would also spend a little more on some better wood.

We have several brand of epoxy:
http://www.boatbuildercentral.com/categories.php?id=2

Joel
Boatbuildercentral.com

 

Except for the floor boards used in the staging around the construction of a boat, CDX should stay far away from the craft. It's junk wood, built to very poor standards, has very few plys of questionable quality and construction.

Go down to the local LowesDepot and look at the edges and faces of CDX then compare that with the cabinet grade birch or oak that they sell. You'll see right away what I'm talking about. The oak and other cabinet grades they sell aren't rated for marine use, but the quality is there. Much better construction (no over lapping plys, less voids, etc.) These and other elements of the construction of plywood is why we pay so dearly for the good stuff.

Pressure treated (PT) can work, but you'll have to wait to use it as it'll be quite wet from the pressure treatment process and unsuitable for epoxy or gluing until dry. At least with PT you'll have Douglas fur or western larch, though the construction will still be poor, unless you get a good grade.

Carpet can work in trailered boats quite well, if kept covered, dry and clean. The ply will need be very well sealed with epoxy and cloth to avoid the difficulties in using carpet in a boat.

Sealing the ply will depend on the ply, the use and expected life. CDX with paint and carpet will be the shortest lived and cheapest. Cloth set in epoxy on a BS1088 grade ply will live the best and cost the most, but also last the longest. Personally I'd opt for MDO, edges well sealed with epoxy and carpeted. The fastener holes that will attach the panels to the boat should be drilled over size, filled with thickened epoxy, then drilled for the fastener. This will keep out the vast majority of moisture getting past the fasteners and into the wood.

 

I assume (please correct me if I'm wrong) that spicerboat is working on a small fishing boat platform/ floor? If so, cdx sealed , and glassed over and carpeted with all compatible materials ie, fabric, resin , adhesive, etc.I think he will get many years before a replacement (is necessary) If used and maintained as a recreational boat only.
I agree with gonzo about marine plywood. But any other type of boat , not a chance! Cdx plywood is for homebuilding

 

CDX has no strength

First of all PAR Must know what he is talking about and I concure, Having said that Plywood ratings mean everything. the fact about CDX is that it has no strength or durability it is simply designed to sheeth structures and hold up siding it requires other structural components to get any strength out of it, such as being nailed to the studs of a wall. this stuff can literaly be ripped apart by hand and maybe a pry bar. there is no material or engineering to make it take face loads or tension and compresion loads, BC on the other hand has cross grained construction strans of material quality materials in each layer wich would be the minimum wood to use. I THINK!

Let me know PAR.

My 22' sylvan off shore needs a floor next year and I'd like do it first class, I thought about using BC and glassing all six side sides. drilling the screw holes glassing them redrilling ect. Any help would be appreciated.

 

As far as using pressure treated ply in an aluminum boat, my understanding is that the new formula that has been in use for a few years will rapidly corrode aluminum. Sam

 

22' sylvan floor replacement

I am in the process of replacing the floor in my sylvan offshore and I was trhinking about using 3/4 inch Marine Deck plastic flooring material. I am also replacing all of the interior upholstery which has turned out to be quite an undertaking. I DO NOT want to ever have to replace the floor substrate again after this replacement. Any thoughts about Marine Deck??? I have also stripped the fabric deck covering off the aluminum and was going to spray it with Rhino Liner for a permanant decking solution.

 

Cdx

I Am curently restoring a '74 Century Ski Fury. i replaced some of the rotting floor with 3/8 treated and fiberglassed over it for "extra protection", 8 months later i find the treatment in the wood and the resin have reacted and the Stainless area washers used to secure to ribs have compleatly rusted to dust under the glass. So i am starting over and using a hard wood(oak, redwood) plywood instead. Treated didnt work for me..

 

Ruggerman, I did some reasearch on glass over plywood and some people suggested that is can trap moisture in the plywood leading to rot... I just got 3 4X8 sheets on one 3/4" thick Marine Panel (made in canada) polyethelene sheets which I am going to replace my boat floor with. The stuff is ballistic and I intend to install EVA foam tiles over it. The floor in my boat is particularly hard to replace and I don't want to ever have to do it again... The 74' Century sounds like fun- is it a V drive like a Resorter?. I just sold a 1968 Correct Craft Barracuda- great old school ski boat! Good luck with the boat floor

 

Marine Panel polyethelene, This is the cutting board stuff or am i lost as usual. After further inspection i have decided to either replace both stringers or splice and scab the bad spots since this repair will be hidden. i usually dont like doing a Half A** job, but i'm not in a shop where i can remove the engin and compleatly cut the stringers out like a Pro would. Bite the bullet and pay the pro, or go for broke? Mabye a Beam & Coke, yeah, i need a Drink!

 

Rurerman44, "Marine Panel Polyethylene has no structural value. It can not be glued, just welded with special plastic welding equipment and it does not hold screws well, so must be through bolted. It is good stuff on cutting boards, but not suitable for a boat deck or cockpit floor.

Exterior grades of Home Depot plywood will work, but will be not as good a quality as marine grade. This means it will rot faster, depending on wood species used inside, will have less number of veneers which is not as strong, it will have big gaps, voids and surface defects, plus other things that can lead to trouble down the pike.

If exterior grade plywood is used, it will need to be coated in epoxy and if it is Doug. fur, it will need a skin of cloth too so it does not split open in spots, which Doug fur is known to do. Hoodriver, if you are still here, you need to think about the floor you are about to install.