Under-deck foam

RCNelson

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Oct 23, 2016
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I just finished tearing up the deck in my boat resto project and the foam under the deck was soaked with water. The boat hasn't seen any moisture in a month. Why would a person use water absorbing foam under the deck? Why would you was the moisture to be retained like that?
 

ondarvr

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Normal, the boat is old, the foam is old, it doesn't last forever.

It starts out as closed cell foam, but over time it breaks down.
 

jbcurt00

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You misunderstand the water logged foam.

If the boat had been stored properly in its past, the foam wouldnt be water logged.

The foam isnt the problem, poor care and maintenance was.
 

GA_Boater

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Flotation foam isn't water absorbing unless it's been neglected. If water is retained in the hull, the first freeze crushes some closed cells. The now open cells fill with water at the next thaw, causing more and more crushed cells when it freezes again. It continues until the foam is water soaked or iced if it's cold enough.

That's why it's important to keep boats protected by covering and stored with the bow up and the plug out.
 

Baylinerchuck

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My chaparral is the second boat I've owned, and I'm at 100% with water in the foam. Both are open bow with a ski locker and the foam is filled beside each stringer. The problem in both my boats is once water gets in, it can't get out. I put drain passages in my first restore, (glassed), through the stringers with 3/4" pvc near the stern. That way if moisture does form, if I store with the bow high it will drain. I hope to be doing the same on the Chap. I know water should never get on the outsides of the stringers, but if it does, it needs a way out in my opinion.
 

RCNelson

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My chaparral is the second boat I've owned, and I'm at 100% with water in the foam. Both are open bow with a ski locker and the foam is filled beside each stringer. The problem in both my boats is once water gets in, it can't get out. I put drain passages in my first restore, (glassed), through the stringers with 3/4" pvc near the stern. That way if moisture does form, if I store with the bow high it will drain. I hope to be doing the same on the Chap. I know water should never get on the outsides of the stringers, but if it does, it needs a way out in my opinion.


I was thinking of splitting some 2" pvc pipe and peanut buttering it in on either side of the dagger stringer, all the way to the back, so it can drain the moisture out. Does anyone see any problems with this idea?
Without a drainage system, I don't see how moisture can get out of that area once it gets in. There is no air circulation through that area to evaporate the moisture.
 

tpenfield

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As the others have stated, it takes years of painfully executed neglect to water up the foam. Initially the foam rejects water, but over time, the water has no place to go and works its way in between the closed cells within the foam.

In terms of providing drainage . . . keep in mind that drainage works both ways. So, drainage along the keel could be a problem, drainage a bit higher in the hull may be fine. It is best to post a few pictures or sketches to help visualize what you are planning.
 

Scott Danforth

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since a boat has a design life of 15 years, and we are all working on boats pushing 30. even if you slapped it together, slapped on the tabbing and resin and sloppily poured the foam, then sloppily installed and tabbed the floor in place like the factory did, it would last another 30 years.

just do a good job on the restoration, keep the boat clean and dry when done and it would last nearly forever without over thinking it
 

gm280

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Oh yes, how to use foam and make drainage to keep water out. But like Scott stated, anyway you can install drainage is also a way for water to go in. I pondered this dilemma for many nights trying to come up with a way to drain water out but also seal the foam. And I haven't figured out anyway that solves both issues without allowing water to get in as well. Using a PCV pipe cut half way along the long length and even drilling drainage holes in the PVC for water to get out has its problems as well. When you mix and pour foam (the usual way boaters do it) the drilled holes also get sealed as the foam expands. I can't figure out any way to accomplish water drainage that doesn't allow water to get in as well. So I chose to seal everything and use mix and pour the foam. That is all I can do to solve the flotation and keep water out. Will that work, I have no real idea, but it is the best I could figure out. We will see. JMHO
 

JASinIL2006

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When I restored my boat, I eventually decided against adding drains in the closed sections. I figured the goal is to keep water out of those spaces. Careful glassing and proper storage seemed to be the best ways to insure water stays out of those compartments. Putting in drains would greatly increase the chances of water ingress because I'd be providing a clear path.

The last thing I wanted was to have some water in the bilge (from skiing/tubing, rain, whatever) sloshing back up the drains and into the foamed compartments.

For compartments that aren't/can't be sealed, it's different, but for under-deck sections that can be glassed in, drains just seemed like a bad idea.
 

Scott Danforth

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When I restored my boat, I eventually decided against adding drains in the closed sections. I figured the goal is to keep water out of those spaces. Careful glassing and proper storage seemed to be the best ways to insure water stays out of those compartments. Putting in drains would greatly increase the chances of water ingress because I'd be providing a clear path.

The last thing I wanted was to have some water in the bilge (from skiing/tubing, rain, whatever) sloshing back up the drains and into the foamed compartments.

For compartments that aren't/can't be sealed, it's different, but for under-deck sections that can be glassed in, drains just seemed like a bad idea.

'nuff said :thumb:
 

RCNelson

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Oct 23, 2016
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Thanks guys (and possibly gals), you have made me see the light. I will just do my best to totally seal all compartments under the deck, fill them with all with foam and keep the inside of the boat dry during storage.
 

KJM

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I have heard about people filling the spaces under the deck with pop bottles or other such things like sealed pcv pipes. the idea being that if the spaces are then left with open drains water can't get trapped in there but you still get floatation. I think it is impossible to keep water out of any space on a boat no matter how careful you are. I plan on doing this method in a year or two to my boat as I too have noticed wet foam down below. BTW if using pop bottle make sure they have plastic caps that can't rust off!
 

jbcurt00

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Bottles and pipes arent ideal either. Inefficient use of availabe space because their round and below decks in a boat isnt.

Pour in foam offers other benefits, not just flotation, and is a significantly better choice.
 

Woodonglass

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Yeah, Plastic Bottles are NOT a wise choice. You'd be better off using the Big Box Store SLAB Foam and cutting it to fit in the cavities. Much better and it will also allow water drainage if installed on edge as it should be.

Check this out...http://forums.iboats.com/forum/boat-...29#post7943729
Even though this shows and aluminum boat, it works the same in a glass boat. If you have weep holes in the stringers any water will be able to flow to them. The sheet foam IS 100% water resistant and will last a as long as the boat if proper care and maintenance is followed. Cost's are about the same as the pour in foam. You WON'T get the added structural benefit that the pour-in foam provides but flotation properties are about the same. If you glass the boat properly and then take care of it In-Season and Off-Season, the only reason water would ever get below deck would be if the hull were to be breached by some outside event. You SHOULD be aware of that in a very timely manner and be able to remedy the situation LONG before the foam or hull had any significant water penetration. Pour in foam is for sure the BEST method but the Sheet/Slab foam is a Good alternative.
 
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tpenfield

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Also keep in mind that the foam, in many cases, is part of the strength of the boat. If you don't use the 2-part pour-in type of foam, then you will not have as strong a hull structure.
 

RCNelson

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Oct 23, 2016
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I am convinced by all you knowledgeable members. Thanks for all the input.
I will go with two part foam and try to fill every nook and cranny below the deck with it. That is down the road a piece as I have to remove the cap and replace the transom first.
 
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