To foam or not to foam????

[Wildman78]

As most of you know I am in the process of putting in a new floor in my skimate. I am almost to the point of laying the nw floor in and was wondering if i should put new foam back in under the floor like it was? Do I really need it or should i leave it out for drainage?

 

[wickedrister]

IN OR OUT

I left the foam out on my boat. Keep in mind it will sink like a stone with no foam if it ever takes on water. The water passing under the floor as you are running along is also kind of loud with no foam . I just wanted to get rid of all the water traps. Good luck and keep up the hard work !!

 

[Mark]

I left mine out as well, but built it in such a way there are 3 airtight compartments. This way it still has flotation but no foam to trap water. It is a little louder, not as though anyone has ever noticed. If I did it again I would at least look into refoaming.

 

[Blizz]

Foam

Most of the better quality foams nowadays are closed cell so they will not absorb water like the old open cell foams.

 

[ButchF20]

Hi Guys,


This is my first post on this board, but have been lurking for some time. I am about 75% done a stringer / floor / bulkhead replacement on a 20 ft Formula, sorry it’s not a Checkmate !!

In this process I have removed 48 lawn and leaf bags of wet foam, which I estimate to be close to 1000 pounds. I had all intentions of not replacing the foam, but what I found out is on many of these boats the foam provides quite a bit of structural value. This wet foam is what caused all the rot problems and is very common in Grady White boats which also use the foam for structural purposes.

I am only replacing two thirds of the foam on the outside of the main stringers and have devised kind of a French drain system, PVC pipe with holes drilled in it, in the bottom of the compartment where that foam will be. I covered the holes with regular masking tape which should just fall apart if it should get wet. The pipe empties into the main part of the bilge where the pump is. This way hopefully if water should get in there, at least it will have a way out, unlike the original design. Under the tank I made some cross members to run between the stringers and glassed them in, which will give the bottom some additional support, since there will be no foam in that area.

I have seen a lot of boats with this p poor design, I guess they never put a lot of thought into having a drain in there compartments, a couple of limber holes would have prevented a great deal of problems later.

Thanks

 

[cooperider]

Nice first post. That was some good info.

 

[speedisgood]

foam DONOT COMPARMISE SAFTEY FOR ANYTHING!!!!!! there are many creative ways to install foam and keep water out one way is a french drain system. what I have done in the past is to bond closed cell foam to the under side of the deck before I glassed it in. it takes some time to fit the deck and ensure about half to one inch of air gap between the bottom and the foam but if amything ever happens, ie cracked hull, boating accident, at least you will still have something to flaot the boat. I have had the former happen to my hydrostream and I was glad that I did replace the foam. The water was a chilly 42 degrees f my girl freind and I would have died from hypothermia quickly if the boat had gone down. Saftey should never be sacrificed........EVER.

 

[jrumon]

Foam alternate...

You could always leave a light-weight vinal innertube inflated up under the bow in case it sinks... that way it at least can be retreved "BOW-UP"...
>>>Use a BIGGER one and it can be a "LIFE-RAFT"...

OK, in all seriousness, it really depends on what you do with the boat and where you boat at. For max performance on inland water, no foam because you should be wearing a PFD anyway! If I was using it as a family boat and/or on big waters, I would probably reinstall the foam just for safety sake.

At least the foam they make today is far superior to water resistance!!!

 

[ButchF20]

What got me to investigate the foam structual benefit, was a shakedown cruise on a Grady White, which the guy had removed all of the foam to replace the stringers, floor etc. We ran for about an hour in the river which was for the most part calm with the exceptions of a few wakes we hit, nothing great. When he placed it back on the trailer we noticed water seeping out of the keel area.

The center of the hull cracked from flexing caused by not having the foam there for support, it convinced me if not the foam something should be there for support. We later ran into a guy who has a small boatyard south of Annapolis who specializes in fiberglass work, mainly on replacing rotton strigers and floors in Grady Whites. At any one time he will have 3 -5 in there for the exact same thing.

Water gets into these SEALED compartments with no way out, and eventually even the closed cell foam will absorb water. This wet foam lays against the wooden stringers amd bulkheads and it does not take long from there. I added additional ventalation and access hatches to at least keep an eye on whats going on down there. Otherwise, its like having a basement in your house with no door to access it.

Like I said before, just a pi$$ pour way to design a boat, but most boats 25 ft and under use this method of construction, much cheaper than adding extra supports and stringers.

Thanks,
Butch

 

[jrumon]

Hmmmm... Foam as structure or a sponge???

My brother-in-laws little 13' Boston Whaler weights about 3000lbs...

Since the hull and deck are litterly "bonded together" with expanding foam, he's screwed!!!

I wonder if anyone has tried to use a liquid solvent to get rid of the foam???

 

[ButchF20]

This is very common problem with the Boston Whaler, a friend of mine replaced the we foam in a boston whaler and it sat 6" higher in the water when he was done.

Looks like its time to start sawing the floor up, I have used acetone along the edge of some gas tanks that were giving me a problem, but I don't think I would use it for an entire boat.

Thanks,
Butch

 

[jrumon]

Acetone...

I'm thinking the "BEACHED WHALE" is more ready for charcoal lighter fluid and a match!

HERES A THOUGHT...
Wouldn't a better location for boat builders to "foam it" be on the bottom of the deck around the entire boat where it stays high and dry??? It would also tend to float more level in the event it takes on water... As the floor foam becomes saturated, it looses it bouyency anyway, in fact it will act like a sponge to some point... so is it really doing any good after a few years???

A solidly built "cored" hull doesn't need "no stinkin' foam" if it's built right! There's not a Checkmate out there that "needs" the foam for strength...

I think most builders do it for the BIA level floatation certification and to cover there a$$'s in the event a boat sinks and the occupents weren't smart enought to bring along PFD's.

Of all the custom west-coast boats (Eliminator, Howard, Sleekcraft, Centurian, Etc.)... I've either owned or worked on, you rarely ever had foam other than maybe the tip of the bow (so it floats tip up for recovery)??? Whats up with that... good, bad, or are they just waiting to slide into the ocean...

And finally the falisy to foam... larger boats don't use it and don't need it??? My 26' Cat deck boat, has NONE!!! The bigger cruisers and such, none... So it's "sound deading" or "added strength" kinda sounds like a bunch of HOO-HAA.
OK... now that I got everyone rolling their eyes... Lets talk about it!

 

[Wildman78]

Thanx guies. Alot of good info here. I am going to refoam it anyways...just incase cause u never know what can happen and i have it sealed up pretty good so there shouldnt be any water getting in what so ever anymore! Pluse it seems that the foam supports the deck on both sides of the stringer so it cant hurt! it'll still weigh less then it did cause it isnt dripping wet.

 

[ButchF20]

jrumon,

You are correct,after the foam gets wet it has absolutely no bouancy value whatsoever. The stuff that I pulled out of my boat sank the minute i put it in water, just to proove a point. Personally i think there is no place for foam at all, but I didn't design these things just end up fixing a lot of them, like I said before, It's a pi$$ pour design but they all use it.

The coast Guard requires only boats under 20 ft to have foam ??? The manufacturers have discovered its a cheaper way to make a boat, at least the smaller ones and all the manufacturers use it.

If you think its not used for strength, call any of the manufacturers, Checkmate, Sea Ray, Formula, Chris craft ar anyone else who makes a 20ft and less boat.

You also mentioned Howard, boy that brings back memories, I had a 19 ft Howard Flat Bottom with a 502 BB Chevy , Tunnel Ram, Magneto, Dry Exhaust, V-Drive w/12% overdrive etc, back in the late 70's. It would run 105 MPH, but other than that a completley useless boat, but boy what a ride !!!!! After a couple of close calls and achieving some common sense, I finnaly sold it, but often wish I had it, at least for a weekend.

Thanks,
Butch

 

[wickedrister]

That soungs like it could get nasty

One late comment on "liquid solvert to remove foam". I wonder if anyone has tried liquid solvent to remove foam and lived to tell about it LOL LOL. I hop I don't run into stress related problems by not re-foaming under my floor.

 

[Blizz]

Foam

If your boat is cored properly as jmuron said earlier foam is not required. And builders of small boats mostly only use it because thier hulls have to pass a bouancy test not for structural issues. And yes sooner or later anything in a boat will absorb water. Mek will dissolve most foams but i wouldn't recommend it..

 

[TRsCheckmate]

On my 1974 TRV there was only foam in the bow and where the rear floor met the bow step. I decided against replacing the foam for all of the previous reasons listed in this thread. The foam was however the only structural support for the floor in the bow. I have cut roughly 10 or so stringers to support the bow floor in order to compensate for this issue and about 20 to support the rear floor.

I don't think the foam in the older boats like mine was for hull structural strength. Floor structure maybe, but if it was for hull strength then a lot more of the older mates would have foam running the whole length of the boat.

Just my $0.02

 

[Blizz]

Foam that's used for flotation puposes usually is not dense enough to be structural.

 

[t town]

I just completed putting a new floor in my sportfire. The old floor wasn't too bad it just had one little soft spot in front of the back seat. I decided since I was installing a complete new interior I would fix it right the first time. When I pulled up the floor the last three feet of foam near the stern was soaked. I kinda expected that...but what I didn't expect was the stringer "yes only one stringer" was made of a four inch strip of plywood. This strip of wood was not glassed in at any point on the hull. It was held in by a strip of bondo on the underside of the wood and the foam which was surrounding it. The stringer that was there was falling apart in my hands and had no structural value. The foam was the primary source of structure in the construction of this boat. I don't think it could have been made any cheaper than Checkmate did at that time. All the foam and stringer crumbs were removed. I glassed in a new main stringer "made with real lumber" and two additional stringers, one along either side of the main. I left the foam out because I don't believe it is necessary with the extra stringers. I still have the foam in the foam boxes in the front and rear for floatation. If that fails I am fully insured.

 

[Boston Predictor]

wow that sucks, I hope my sportfire isnt the same way....
Glad to hear you fixed it though, do you have any photos t town?