Good alternative to plywood?

[Buster]

Some people do put used motor oil on lumber that will sit out in the rain, for example, something like a wood deck on a utility trailer. It's not something I would do on a boat. While I think it would soak up well on plywood, I think the oil will negatively affect the performance of whatever adhesive you use for the covering foam.

Edit to add: Old motor oil will never cure hard and will not adequately stop water penetration into the plywood.

I have a fair amount of plywood in use on my boat. All of it is sealed with fiberglass resin that was mixed and then painted on and allowed to cure before installation. I paid particular attention to coating the edges of the plywood very well. Once cured, the resin will accept adhesives on the surface. Scuffing of that surface is recommended.

I always assumed the used oil trick was more about stopping fungal and chomping pests than "waterproofing." The stuff is toxic to pests and toxic to you, bad for the lake, and probably illegal to use if you care about such things. A good exterior grade plywood and seal it with an epoxy like West Systems is the way to go. Use the lowest viscosity stuff and build up multiple thin coats. Thicker stuff doesn't penetrate as well. But it also needs to be covered with paint, carpet, EVA, or whatever because on its own you'll abrade right through it.

 

[thill]

I agree. It really depends on the environment. I live in the deep south and have seen boats covered in mildew from a waterproof tarp. I used a "waterproof" canvas tarp to cover my boat that allowed airflow. It was not perfectly waterproof, but allowed some airflow. Thankfully my boat is now stored in a garage. I would think a waterproof tarp would work well in northern less humid climates.

I agree with you on that. Canvas covers are even worse. We live in a very humid area, close to the water, and even my fiberglass boats become a mold pit if sealed too tightly or super-fast if it's a canvas cover.

In the pic I posted above, I had the back sealed tight, as I was putting a new floor in the boat, but normally, there is an outboard motor there, and very good airflow under the cover. I typically leave all the hatches open and no mold grows anywhere.

The idea of the above pic is that NO water gets in the boat, but that wasn't a good example for long-term storage.

 

[Henk van Gerwen]

I know right. If “Weight isn't an issue.” -And just like anything else, take good care if it. I still have mine on my 1992 aluminum.

Now if money is no object and you want to throw other criterias/considerations, I recommend those coosa boards. They are strong, lightweight, etc.. A buddy of mine rebuilt his entire transom. I used it as a platform between a set of outriggers I purchased for my canoe. I was tired of sitting, wanted to stand and stretch. (see images)

Some helpful links below. Good luck!

Replacing Deck by Nick:
https://www.boatoutfitters.com/replacing-a-rotten-wood-core-deck-with-coosa-learn-content

Comparisons:
https://coosacomposites.com/the-coosa-board-advantage/

Technical Data & Specs:
https://coosacomposites.com/technical-data/

Coosa FAQs:

https://coosacomposites.com/coosa-composites-faq-what-were-asked-most-about-our-panels/

https://coosacomposites.com/wp-content/uploads/2023/07/Frequently-Asked-Questions-6.30.21.pdf

Other:
https://www.cruisersforum.com/forums/f55/tips-for-working-with-coosa-board-264163.html

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I would say Coosa is the way to go, it's light weight, strong and doesn't rot!

 

[Buster]

I would say Coosa is the way to go, it's light weight, strong and doesn't rot!

To clarify earlier comments, I agree with this, but people have a real hard time with the up front cost of Coosa compared to exterior ply and epoxy. I'm using Coosa on my boat and other than the endless fiberglass slivers, I love it.

 

[boaterB12]

To clarify earlier comments, I agree with this, but people have a real hard time with the up front cost of Coosa compared to exterior ply and epoxy. I'm using Coosa on my boat and other than the endless fiberglass slivers, I love it.

Yup. -And to clarify as well…

Plywood + whatever…
“I know right. If “Weight isn't an issue.” -And just like anything else, take good care if it. I still have mine on my 1992 aluminum.”

Coosa board…
“Now if money is no object and you want to throw other criterias/considerations, I recommend those coosa boards. They are strong, lightweight, etc..” (see links original post above, if interested)

Good luck.

 

[thill]

Here are a couple of pictures of my permanent boat cover setup.

This is how it looks from the front quarter. Nice and tight, snow, rain and ice just slide right off. I rarely have to knock snow off, but we live in Virginia:


You may notice the cat trotting toward the boat. They are my biggest issue, and the next few pictures will show why...

Here is a picture from behind. Everything nice and tight, but lots of air space, so I get NO mold



Looking up from below, you can see how much clear ventilation I have, but not a leaf will go into it:


This space is why the cats are a pain and a blessing. With three of them, we have NO problem with mice anymore. The only mice we see are the dead ones the cats bring us. But that being said, during the winter, inside my boats is the cats favorite place to snooze. Soft carpet, sheltered from the elements, and it warms up in there nicely on warm days.

I can't blame them, but it is annoying to find cat hair in the carpet!

I have found ways to stop them from getting in, but the battle isn't worth it. I found the best remedy is to lay an old dog towel up on the rear deck. The cats almost always prefer to sleep there, saving me much aggravation.


I've been using this cover system for a number of years, and it's cheap and very effective. Better than any custom or generic cover I've ever used.

For this reason, regardless of WHAT wood I use, even if it was untreated, my decks would last a very long time.

I hope this is helpful to someone.

 

[Bantou]

How badly does the wind grab it from the back? We get some crazy wind at times and I'm afraid that the tarp would get torn up pretty quickly.

 

[fwman1]

The panels I made for my Jon boat have held up great. One inch thick polystyrene foam with fiberglass reinforced plastic epoxied to both sides. Super strong with minimal support needed.

 

[Buster]

The panels I made for my Jon boat have held up great. One inch thick polystyrene foam with fiberglass reinforced plastic epoxied to both sides. Super strong with minimal support needed.

Can you give more detail on what your "fiberglass reinforced plastic" sheet is? I've considered similar layups but always ended up going with off the shelf materials instead.

 

[goggle-eye]

I have been looking to upgrade my travel trailer to a 5er. Several manufacturers boast about using ASDEL in the sidewalls. It is a composit of some type used as a replacement for Luan panels eliminating the potential for water damage. It cannot not be too thick of material but I was wondering if it will have potential for use in the marine industry. Just a thought.......

 

[lightflyer1]

Can you give more detail on what your "fiberglass reinforced plastic" sheet is? I've considered similar layups but always ended up going with off the shelf materials instead.

https://www.homedepot.com/p/Glaslin...rglass-Reinforced-Wall-Panel-665041/202085623

 

[thill]

How badly does the wind grab it from the back? We get some crazy wind at times and I'm afraid that the tarp would get torn up pretty quickly.

It doesn't really. We are having 40-50 MPH winds today, but it really doesn't move much at all. After the center one gets tightened down, I have the corners pulled tight with a black bungee cord and it's solid.

I've been using this system for some years now, and nothing hurts it besides sunlight. Eventually, even the good silver ones will get degraded by sunlight. Blue ones are the worst, brown or green ones are better, and the silver ones are the longest-lasting.

I get mine from Harbor Freight when they go on sale, but maybe some others will last as long or longer.

All I can say is that I'm extremely happy with this system. No more water or leaves or mold in my boats. It's as good as keeping it in a garage.

 

[thill]

I've seen guys use something like these. At $25 each, they look like a VERY good deal, if stiff enough to use as decking:

https://www.facebook.com/marketplace/item/1060060992532900

 

[fwman1]

Can you give more detail on what your "fiberglass reinforced plastic" sheet is? I've considered similar layups but always ended up going with off the shelf materials instead.

https://www.tinboats.net/threads/anyone-create-frp-board-and-polystyrene-sandwich-for-decking.49874/

 

[Buster]

https://www.homedepot.com/p/Glaslin...rglass-Reinforced-Wall-Panel-665041/202085623

Thought that might be it. But I wasn't sure if you were using OTS panel or made that yourself, too. Thanks.

 

[jlake1958]

To clarify earlier comments, I agree with this, but people have a real hard time with the up front cost of Coosa compared to exterior ply and epoxy. I'm using Coosa on my boat and other than the endless fiberglass slivers, I love it.

I went with Blue Water 26 Coosa

To clarify earlier comments, I agree with this, but people have a real hard time with the up front cost of Coosa compared to exterior ply and epoxy. I'm using Coosa on my boat and other than the endless fiberglass slivers, I love it.

I went with Blue Water 26 Coosa and then added Gluvit to the Coosa. One thing I noticed was that Coosa is brittle. My experience with Wood and sheet metal screws made me feel that regular quality plywood held screws a little stronger than the Coosa. Dont get me wrong, the advantages of Coosa far outweigh the "perceived" negatives but I did notice that...

 

[AlanT]

I agree. I used 5/8" Coosa Blue Water 26. I've had no problems with it screwed down, but would be concerned with screwing anything else to it that would apply torque on the Coosa board. I found Coosa easy to work with and allowed me to file the board around the edges to get a "reasonably" tight fit. I couldn't do that with plywood. It all depends on the application, longevity desired, boat storage options, and dollars available. I'm glad I bought it before prices sky rocketed.

 

[Buster]

I agree. I used 5/8" Coosa Blue Water 26. I've had no problems with it screwed down, but would be concerned with screwing anything else to it that would apply torque on the Coosa board. I found Coosa easy to work with and allowed me to file the board around the edges to get a "reasonably" tight fit. I couldn't do that with plywood. It all depends on the application, longevity desired, boat storage options, and dollars available. I'm glad I bought it before prices sky rocketed.

I have foam underneath most areas, so went with 1/2". Where I have open compartments, I glassed both sides of the 1/2" and kept the spans to about 14" and it's solid. I agree with jlake's comment about screws. Washers to spread the load help, and where I've planned for them I add a backer.

 

[thill]

I've used the 3/4" Coosa and am pleased with it. I think it was 26. Glassed over the top, and it holds screws well. Better than any of the honeycomb decks. In fact, a lot of builders use honeycomb with Coosa inserts for areas that will need to be thru-bolted or screwed.

I found Coosa easy to work with and allowed me to file the board around the edges to get a "reasonably" tight fit. I couldn't do that with plywood.

Put a 40-grit flap-disk on your angle grinder, and you can easily do whatever you want with plywood.

Tip for anyone who is having trouble fitting plywood closely to your hull.