More thoughts on foam in rebuilds.........

[Lou C]

I was looking at the great job on the Wellcraft posted recentely in this forum, and it got me to thinking about foam and construction. Many say the foam causes rot, and not to use it in rebuilds. Still others say that the foam is a necessary structural part of the boat. Looking at the Wellcraft, which had no foam, and my Four Winns, which had foam, I noticed that while the stringer design is about the same, the Wellcraft has many more crosswise bulkheads, my FW had only two, one at the front of the gas tank compartment and one at the rear. So if I did not replace the foam, my guess is the boat would have been less rigid than the designers intended. Wellcraft did not have to put in foam, being that the boat is more than 20', but the structure was beefed up with more bulkheads. I did replace the foam, but when I installed the floor, the compartments were sealed by using 3M 4200 to glue the floor to the stringers, and stainless steel screws were used as well. All holes were filled with 4200. Standing on the floor, it felt much more solid with the foam, than without the foam when I trial fitted the parts. Thoughts??

 

[Bondo]

Re: More thoughts on foam in rebuilds.........

Standing on the floor, it felt much more solid with the foam, than without the foam when I trial fitted the parts. Thoughts??

That was Also Before you Glued,+ Screw the floor down,......
That Alone would Stiffen the floor........

 

[DJ]

Re: More thoughts on foam in rebuilds.........

Foam is not so much a rigidity component as it is a safety one. All boats under 25' (I believe) manufactured today must maintain level flotation when swamped.

The issues I see with foam is that many designs do not allow the water to channel out. So, the water sits and causes rot. That is going to be true with any boat that uses wood, in the construction.

The few exceptions to foam being structural are injection foam boats such as Boston Whalers and Carolina Skiffs, among a few others.

On the boats that I have redone, I lay down PVC pipe that has numerous holes drilled in it. I then cover it with heavy plastic strips that I can pull out when the foam sets. I do not expect the foam to be structural.

Of course, you can avoid that by using foam blocks.

 

[hard-3]

Re: More thoughts on foam in rebuilds.........

Hi folks,
i don't know if you have looked in to it ,but the spray closed cell isocyanate insulation foam does not soak up water. I have it sprayed in my house attic. When it sets up, in about 1 min. it is very rigid. I have it sprayed over my porch ceiling,which is 12 inch aluminum soffit nailed every 2 ft to 1x4 lathe fastened to the truss bottom. this foam is 4 inchs thick , and is rigid enough to support my 230 lb. standing anywhere. I did not believe it when the installer told me it would do this until he jumped up and down in the middle. He was confident enough in the product to do this ,knowing if he ruined my ceiling he would be fixing it! I think the product would work very well as a stiffiner, as well as flotation. You might contact an insulation contractor and take it to them to have sprayed. Their set-up is a pain ,but if you took it to them on a trailer to where they were to do a house you could maybe get a deal. Just my 2cents
Jeff

 

[Bondo]

Re: More thoughts on foam in rebuilds.........

,but the spray closed cell isocyanate insulation foam does not soak up water.

Welcome Aboard Newbie,.........

Obviously,...... You haven't Stripped out very many Boats that were built with WaterProof, Closed-Cell Foam...............

I Have,........
I Can tell you,.......
Closed-Cell WaterProof Foam,........................................Isn't.........

 

[DJ]

Re: More thoughts on foam in rebuilds.........

Closed-Cell WaterProof Foam,........................................ISN'T.........

Yep, I can't disagree. It seems to be impervious to moisture, in the beginning, but seems to deteriorate over time.

 

[hard-3]

Re: More thoughts on foam in rebuilds.........

I see where you are coming from, I guess in the insulation application it would not be exposed to water , only to water vapor. I would suppose that if exposed to water it might even sponge some. I believe the key is to give the water some where to drain to so as not to be in contact with the foam all the time.

 

[Chris1956]

Re: More thoughts on foam in rebuilds.........

Lou, I believe the foam adds considerably to the structural strength of a boat. I think the manufacturers deliberately design the boat to take advantage of the foam's rigidity, and are able to leave out wooden supports because of the foam. I had a crack form in my SeaRay, between two stringers. I believe the crack formed because either the original foam was missing or defective in that area, or it deterioated over time. The fiberglass skin (or hull) was then able to flex which caused it to weaken over time.

 

[klos]

Re: More thoughts on foam in rebuilds.........

Lou, I believe the foam adds considerably to the structural strength of a boat. I think the manufacturers deliberately design the boat to take advantage of the foam's rigidity, and are able to leave out wooden supports because of the foam.

I second that!

 

[DJ]

Re: More thoughts on foam in rebuilds.........

Lou, I believe the foam adds considerably to the structural strength of a boat. I think the manufacturers deliberately design the boat to take advantage of the foam's rigidity, and are able to leave out wooden supports because of the foam.

I do not agree, with some exceptions, as previously stated.

"Sound deadening" and "feel" are not necessarily signs of structural integrity.

As an example; Boston Whaler boats are carefully engineered to use the foam as a structural component. That "engineering" takes into account the entire hull shape.

Boats designed with a skeleton, or stringers, were not designed as foam being a structural part of the hull-IMHO. If they were, why is the "skeleton" (or stingers)there?

In traditional boat design, foam is used to meet safety standards, at time of manufacture.

I won't deny that some makers used foam as a cheap replacement for hull support. That does not make foam a viable option, IMHO for making a hull better, by rebuilding it.

It's the rebuilders choice. How long do you want it to last? Replacing what is there gets you what was done originally. Going further, adds life.

 

[tmh]

Re: More thoughts on foam in rebuilds.........

I have to say that although I still plan to add some supports and use soda bottles I would say the BEST way to do it is probably to add a drainage system like the one mentioned here (picture) and then use the pourable foam for floatation and rigidity. I don't think the closed-cell foam soaks up much of the water IF the water has a path out. If the water sits there (like on most if not all these boats) then eventually the foam becomes water-logged.

My boat is worth $2-3k and I'll likely have it a fewmore years only. I am not looking for the added hassle pouring foam brings! (Yeah, I knoe, if you do it right..... WELL I usually DON'T do it right, unfortunately). I have been told that if I cap my 2-liter soda bottles during the winter they should not deflate much with changes in temp, and they won't break in the heat, just increase internal pressure. Also, if glued together and packed fairly tight they don't make a racket or anything. MAYBE tis is wrong, I don't know. I'll find out though.

 

[DJ]

Re: More thoughts on foam in rebuilds.........

tmh,

Use soda bottles if you want. I find that idea a bit lacking. (lot's of unused space).

I'd rather see you use closed cell foam blocks. Cheap and easily formable. They allow drainage and still fill the space with useable foam flotation.

 

[tmh]

Re: More thoughts on foam in rebuilds.........

Maybe I'll look into closed cell foam blocks/chunks or whatever is cheap. I've bought closed cell foam for seating and it's expensive (not the stuff one would use for floatation alone); any idea where i can get cheap closed cell for floatation?

Maybe a local foam co. might cell scraps, but there aren't many around that would have the right stuff I'd expect.

 

[Bondo]

Re: More thoughts on foam in rebuilds.........

While I can't argue that there's abit of Wasted Space when using the Soda Bottle Floation plan,.....

I Personally am striving to slow the boat from Sinking,.....
Not to keep it Afloat Indefinitely......

If the Worst Happens,...... A PFD will Save your Life,.......
Foam will Still just Rot your boat......
Waterlogged Foam Won't hardly Float it's own Weight,.....
How's it going to Float your Boat,..??....

If you think your Hull Isn't Strong enough to support itself Without the Foam,........
Add some More Stringers,+ Bulkheads........
The boat Will be Stronger,+ Won't Rot so Quickly as when Foam Filled.......

TmH,.... If by chance you need More Bottles,+ it's Not Winter time,.....
Throw'em into the Freezer for awhile,+ Cap'em There......

 

[Lou C]

Re: More thoughts on foam in rebuilds.........

As a side note, during the rebuild I e-mailed Four Winns, a company that has pretty good customer service, and they told me that the foam was for both structural reinforcement and floatation....and when I took it apart, and found one stringer rotted to the point where the front half and the rear half where not even connected...yet the boat seemed solid going over swells in LI Sound, I have to think it contributed more than a little to stiffness...
What I found when I removed the old foam is that it was far from waterlogged. I had to dig all the way down, to the last 1/8 in of foam to find water.
Since the company that built the boat said that in this case the foam was also structural, and looking at the difference in the constuction of a boat with foam and one without (the Wellcraft mentioned) I didn't want to second guess what they told me.
I feel that real cause of the rot was carpet covered floors, which hold moisture, and a thin skin coat of poly resin, which is not waterproof. From what I can see it rotted from the top down. This one will be finished off with epoxy and 'glass, and then with Durabak marine non skid, no more carpet.

 

[iwombat]

Re: More thoughts on foam in rebuilds.........

I'm with ya on the carpet. I just took one of those apart. Once the backing deteriorates on the carpet, it might as well be a leaky watertower sitting on your deck.

 

[sbklf]

Re: More thoughts on foam in rebuilds.........

Dense enough foam can keep the floor and hull from flexing. It can also keep thin fiberglass stringers vertical to the hull and sole where they are stongest. It does offer structural assistance and will keep you from sinking but it alone will not keep the boat from breaking in half.

Cut the skin off closed cell pour foam and the open (cut) cells on the surface will hold water but it will not absorb beyond them into the remaining closed cells, if it does it is not closed cell but a sponge and not flotation. (If you know of a pour foam that does absorb water let me know and I will stay away from it)

Unless the foam is all poured at one time moisture can also get trapped inbetween pour layers. Any moisture trapped between the sole and hull can condense on the bottom of the sole in the right conditions. Foam can hold moisture against wood soles and stringers and rot them out. I would stay away from using foam with wood unless it was designed to drain and dry should it get wet. If I had to use this combination I would seal the wood with epoxy.

Unless structural assistance from foam is necessary I like the bottle idea, light and cheap. I would tie the bottles together somehow and pour foam to fill the voids (this would keep them quiet). I had a friend that purchased vinegar bottles for this purpose (?maybe they are rigid and have a better sealing cap?)

 

[Mark42]

Re: More thoughts on foam in rebuilds.........

Regarding the soda bottle idea for floatation, just do this simple test. Take an empty soda bottle with the cap on tight. Then submerse it in water. You will notice that it starts to collapse almost imediatelly at about 1 foot under water. By the time it reaches 2 to 3 feet, the depth of the floor in a swamped boat, they are no longer providing the boyancy you may have expected because they displace less and less water the deeper they go.

To work properly, the bottles need to be pressurized, and then you have to worry about pressure leaks.

Bottles is just a bad idea.

If you want water to drain around your flotation, then pour the foam in large plastic bags and let it expand that way so it doesn't stick to the hull or stringers. Just like is done with packing heavy objects. I once received an 8 hp small engine packed like this from the manufacturer. Slick. Just pour the foam in a bag, stuff the bag in the area to be filled, then watch the bag expand.


EDIT:

BTW, this is from US Composits regarding the use of its closed cell polyurathane pourable foam:

Is it water proof? Yes, but with the following caveat. The foams that we sell are considered closed-cell, which means that each cell that makes up the foam structure is completely closed off from surrounding cells which prevents it from acting like a sponge. It is completely safe for this foam to be in contact with water for hours/days/weeks and even months with no adverse effects. However, it should never be submerged in contact with water permanently. Over a period of years the water contact can begin to soften the foam and cause it to lose its closed-cell status. This foam is designed primarily to be used as an insurance policy in case of damage/holes that could cause a vessel to lose buoyancy. Pinhole sized openings would essentially have no effect on the foam since the amount of exposure is so minimal but you should always make repairs as soon as possible to keep the foam effectiveness as good as possible. This will be the case will all after market closed-cell polyurethane foams and even manufacturer installed foams.

 

[JasonJ]

Re: More thoughts on foam in rebuilds.........

I've always been a pro foam person. Foam can add structure depending on density and the way it was poured. Foam, even closed cell waterproof foam, can evenually start to take on water. Usually the boats that have waterlogged foam are also decades old, and have not been well cared for. Sealing screws that go through the floor, covering the boat in the winter and when not in use to keep water out, things of this nature dramatically increase both the life of the foam and the entire boat in general.

I myself place the life of the people on my boat as well as my own life far ahead of how long a boat lasts, so foam will always be in my boats. I just do what it takes to prevent the almost inevitable water intrusion.

 

[Tail_Gunner]

Re: More thoughts on foam in rebuilds.........

I've always been a pro foam person. Foam can add structure depending on density and the way it was poured. Foam, even closed cell waterproof foam, can evenually start to take on water. Usually the boats that have waterlogged foam are also decades old, and have not been well cared for. Sealing screws that go through the floor, covering the boat in the winter and when not in use to keep water out, things of this nature dramatically increase both the life of the foam and the entire boat in general.

I myself place the life of the people on my boat as well as my own life far ahead of how long a boat lasts, so foam will always be in my boats. I just do what it takes to prevent the almost inevitable water intrusion.

I agree with you strongly on this point Jason, Using the proper amount of foam in a boat (small) could very well be life saving, one can only hope no one would ever have to second guess themselves in a precarious moment on the water. What's that old saying "There are no Atheist's in a fox hole"

As to structure, there is no one size fit's all theroy here. Does 2lb provide structure no, does 4lb probably not, now 8lb yes it does as well as 16lb.

You can take that even futher, if you properly measure out the cavity between the floor and the hull (sq ft) and drill vent's or holes for foam expansion, fit your floor in place and then pour the foam in allowing it to expand until it flow's out from your vents, you will not only gain strenght from the foam (4lb and up) but you will also glue the entire floor to the hull. Foam bond's extremely well to both wood and glue it will become almost one unit.

Here's some old pic's, the floor was laid down, holes were pre drilled and the edge's were 1/4 short of the wall's. I just kept pouring until the foam expanded first from the oval vents to the outside edge's ensureing a tightly compacted expansion. The guide you see against the wall held the floor down to keep it level and futher compacting the foam.

As you can see the foam came up the middle and out the side's, i doubt very much if there are any void's, it expand's with quite a bit of force, but it also glued that entire floor to the hull and vice versa.

Now she's sealed and glassed in, you'd have to jump on it to feel how rigid it is, just like concrete but i did use 8lb.
Now rot is always a concern so i did fully encapsulate the stringer's in glass, and shot the entire hull-stringer with a bed liner type of material. Will it rot........ yes someday but not in the next ten years or so and if i take on a few big swell's and thing's dont go well, i will stay with the boat. Strictly a opinion here Your milage may vary........8)