Anti-rot idea. Want opinions.

[109jb]

I asked this question in another post, but I think since it was 4 or 5 pages of posts, that many probably didn't see it. I really want to hear opinions, so decided to make a dedicated post.

After this boating season I am going to be replacing all of the wood in my 1988 Sea Ray Seville. I was first looking for something rot-proof, and there are products out there, but I can't justify the cost of these on a 20 year old boat that has definitely seen better days. So, since I'm going back in with wood I was thinking of ways to prevent rot. Along these lines I will be fiberglassing all sides of all wood going back in, and sealing holes as best I can. It also seems that one of the biggest contributors to rot is having water soaked foam right up against the wood. I don't want to go foamless, so I was thinking about ways to keep an airspace between the foam and wood while also keeping a channel for any water that does get it to get out.

I remembered a product I had seen on TV and thought it would work perfect. Now my idea. Once all of the below floor wood structure is replaced I would cut and fit this material against the wood and hold it in with a few dabs of adhesive. Same for the bottom side of the floor. Might have to cut the holes for foaming before actually putting the floor down. Once the floor was installed I would foam the cavities and this plastic stuff would keep the foam from expanding against the wood parts. It would leave a 1/2" air space next to the wood which would also act as a channel for water to get to the bilge. One thing that was misinterpreted in my previous post is what this material is made of. It is plastic, not metal. I repeat, it is plastic. Well, That's the idea. What do you think??

 

[gcboat]

Re: Anti-rot idea. Want opinions.

It certainly makes for an intriguing setup. I'm thinking that if you do a proper prep job on your deck lumber ( epoxy, poly ) that this would be an unnecessary step. Also, the newer flotation foams are made so that there will be no water rentention.

 

[tashasdaddy]

Re: Anti-rot idea. Want opinions.

if you have ever used expanding foam. it will probably flatten that. i have used it in building construction, it has bowed window and door opening. push plaster of walls. all kinds of unimaginable things.

 

[oops!]

Re: Anti-rot idea. Want opinions.

heh heh heh....td is again correct....expanding foam will crush that stuff like a beer can.....

....its a good idea tho......

in your 88 ray.....foam is not structural.....you might want to think of putting it under the cap....so if it gets swamped....the cap will hold up the boat....rather than the sole.

other than that.....im putting a dozen old life jackets tied togeather under the deck.......that way i will have flotation that can be changed each year and never fear of water getting trapped beside my stringers.

as far as your wood....there is a product called penskie board....@ $10 sq foot......that means a 4x8 sheet is just a little more than plywood....if id have found it soon enough...i would have used it.

cheers
oops

 

[Mark42]

Re: Anti-rot idea. Want opinions.

if you have ever used expanding foam. it will probably flatten that. i have used it in building construction, it has bowed window and door opening. push plaster of walls. all kinds of unimaginable things.

When I installed a fiberglass whirlpool tub in my bathroom, I was told to use expanding foam to bed down the bottom of the tub because it needed some support and it was rather rounded. The next day the tub was lifted about 1 inch off its parimeter support 2x4's. Good thing I had a layer of tar paper between the foam and the tub. I eventually bed down the tub in thinset mortar.

Anyway, if that stuff is rigid enough, and there is space for the foam to expand out and not build up pressure, then I think its worth a try.

The down side is you are losing the additional strength that foam gives when it expands and completely fills the void. It sticks to everything and helps make the hull rigid.

 

[GatorMike]

Re: Anti-rot idea. Want opinions.

I'm with tashasdaddy on this one, I used that stuff to pop out a dent in my truck tailgate. When that stuff expands you had better have plenty of volume for it to expand in or it will crush and blow apart things.

 

[Joe_the_boatman]

Re: Anti-rot idea. Want opinions.

Just an idea: foam sheets instead of liquid foam for flotation, and inspection ports in the deck (i.e. removable covers) to allow it to dry out when the boat's put up.

Don't know how well foam sheets would work in your application though.

 

[109jb]

Re: Anti-rot idea. Want opinions.

I highly doubt that the expanding foam could crush that stuff. Although I don't know the specs for that particular material, I found some similar material that is used on the outside of basement walls in the same way and it has a compressive strength of 5,200 psf. Knowing that, now what do you all think?

 

[salty87]

Re: Anti-rot idea. Want opinions.

if you lay the deck down first, i'd put my money on the foam flattening those. another possible problem is if you don't seal the sheets of that product together, the foam will get under it when you pour it in.

 

[109jb]

Re: Anti-rot idea. Want opinions.

First of all, at the 5,200 psf that similar materials can take, you would blow the stringers , the deck or the hull apart. Since many people have installed foam in cavaties like this with holes cut for excess foam to escape, I'll guarantee that its not exerting 5200 psf. But lets just assume it won't crush the material because I would run a test to check it before I did it anyway. I know that the edges would have to be sealed, but that's easy.

The real question is not if this stuff will crush, but are there any drawbacks to maintaining an airspace between the wood parts and the foam?

 

[BillP]

Re: Anti-rot idea. Want opinions.

The way not to have rot is to use pressure treated wood. If you want foam to stay dry, get sheets of the stuff, cut to size and seal surfaces with generous coatings of epoxy before installing.

bp

 

[boatboy999]

Re: Anti-rot idea. Want opinions.

I've recently completed a re-build of a 1991 Sea Ray 170; a complete back to bare glass hull re-build including the transom. I used marine ply throughout and saturated every piece of ply with epoxy before it was joined to any part of an assembly (avoids dry joints and seals the wood from water), it should not be necessary to fiberglass everything except in wear areas such as fuel tank, bilge and the floor). All underfloor has been foam filled and I learned a few trick in doing that!. You don't want voids for water to move, you really want the water never to get there in the first place. Allow for drainage of any areas that will get wet and seal anything that is wooden properly. I used resin from Clarke Craft in NY (it retains some flexibility and is not brittle like some and is non-blushing) and used their general guidelines on the ply preparation and epoxy use. Got to say that I put a lot of money into the project, but rot is one thing it will never do. It is better built now than when Sea Ray built it... and I really mean that!!!
Any aspect of the re-build (which started as a couple of soft spots in the floor and some upholstery that needed a bit of attention), let me know. It may be an old boat, but if its got a good engine and outdrive and you like it, done properly, you'll never want to part with it.
Let me know if I can help

 

[109jb]

Re: Anti-rot idea. Want opinions.

The real question is not if this stuff will crush, but are there any drawbacks to maintaining an airspace between the wood parts and the foam?

The above question says it all. I don't mean to be rude, but NOBODY has answered this question. I guess that could mean that nobody has any drawbacks. If so, great.

Please don't answer telling how your idea is the best. Again, not to be rude, but I know about the different ways to put it back together, completely glassing everything, using treated plywood, yada, yada, yada. There is plenty of info on that kind of thing. Please just answer the above question if you can.

 

[proshadetree]

Re: Anti-rot idea. Want opinions.

There is no drawback to an airspace.I have a 75 Sidewinder that has no foam only 2 stingers and a 455 with a jet drive never had a crack and have been rough on this old dog.the foam is there to slow down water if you pop a hole in the hull.Not for bracing its just a valve.Look at the boat design forum and ask around.

 

[109jb]

Re: Anti-rot idea. Want opinions.

Thanks. That's the kind of answer I am looking for. I had not though about the foam slowing down a leak as you had mentioned. My first thought was to creat an airspace only between the foam and the stringer's/deck. I had then though about creating airspace between the hull and foam too, but I'll re-think that now.

As far as the foam not being structural, I was under the impression that some boats out there did need the foam to provide hull support. It was mentioned earlier that the Sea Ray I have is not in this category, but is there a way I can find out for sure??