Why Foam?

[jiminmontana]

I see that some folks pour expanding foam under the decks and others do not. Is this ONLY to make the boat not sink if it swamps out? What are the chances of that even happening? When water gets under the decking, won't the foam hinder that water from escaping to the drain hole and cause mildew/stink?

 

[Spinnaker]

Re: Why Foam?

I see that some folks pour expanding foam under the decks and others do not. Is this ONLY to make the boat not sink if it swamps out? What are the chances of that even happening? When water gets under the decking, won't the foam hinder that water from escaping to the drain hole and cause mildew/stink?

It is usually a sealed compartment the foam is in so yes, it is supposed to help keep your boat above water and also has sound deadening qualities. If any water does get into these places it is trapped and adds a ton of weight when wet. There should not be limber holes draining from these compartments (outside of stringers). Even though you might remove the foam it is still supposed to be a sealed compartment to keep from sinking your boat if you ever happen to punch a hole in your hull. Personally I have removed all foam from my boat.

 

[Robert4Winns]

Re: Why Foam?

In some boats the foam adds to the structure, making the hull and deck more rigid. But in most cases it is just there for safety. Boat manufacturers add it so the boat will have positive boyancy if swamped which is required for boats under a certain size. Many people who rebuild their boats leave it out so water that gets under the deck can drain to the bilge.

 

[MTribe08]

Re: Why Foam?

I see that some folks pour expanding foam under the decks and others do not. Is this ONLY to make the boat not sink if it swamps out? What are the chances of that even happening? When water gets under the decking, won't the foam hinder that water from escaping to the drain hole and cause mildew/stink?

It does a couple things:
1) provides floatation in the unlikely event of a sinkage.
2) provides support for your deck in between side supports
3) offers a bit of sound deadening

** I believe it is mandatory to have it in a vessel under 21ft

As to your concerns, many people feel the same way you do. If water gets down there with no place to go, the foam will eventually soak it up.

I used my original dry foam and trimmed it up a bit, leaving a nice big channel at the base of my stringers for water to drain.
Hope that helps.

 

[MTribe08]

Re: Why Foam?

There should not be limber holes draining from these compartments (outside of stringers). Even though you might remove the foam it is still supposed to be a sealed compartment to keep from sinking your boat if you ever happen to punch a hole in your hull. Personally I have removed all foam from my boat.

This is true, but I think water would still find it's way in there, just more slowly. I guess you have to decide what you want; knowing that if water gets under your deck outside of the middle, it will have a way out effectively saving your stringers from rot or knowing if you put a hole in your hull water will get to the foam quicker.

I say make sure you have a good PFD and insurance. You'll need em both either way

 

[Bondo]

Re: Why Foam?

Is this ONLY to make the boat not sink if it swamps out?
When water gets under the decking, won't the foam hinder that water from escaping to the drain hole and cause mildew/stink?

Ayuh,... That's It,...
Also,... Always provide a way for water to drain back to the pumpable bilge...
Limber holes,+ drainage channels are Very Important...
As most of Us know,... There's No such thing as a WaterProof compartment in a boat...

 

[bananaboater]

Re: Why Foam?

It does a couple things:
1) provides floatation in the unlikely event of a sinkage.
2) provides support for your deck in between side supports
3) offers a bit of sound deadening

** I believe it is mandatory to have it in a vessel under 21ft

As to your concerns, many people feel the same way you do. If water gets down there with no place to go, the foam will eventually soak it up.

I used my original dry foam and trimmed it up a bit, leaving a nice big channel at the base of my stringers for water to drain.
Hope that helps.

Exactly! Discard any water soaked foam and use closed cell. Avoid spray foam.

And if your boat swamps it should float enough to give you an island till help arrives.

 

[Spinnaker]

Re: Why Foam?

Ayuh,... . There's No such thing as a WaterProof compartment in a boat...

Not waterproof but sealed. Also, if you punch a hole in your hull in a sealed compartment that someone put a limber hole in the stringer for it to drain you run the chance of your boat going completely under. If the hole is big enough there isn't a bilge pump made that will save you. If you have done the build properly you should never get water in those area's.

 

[jspano]

Re: Why Foam?

i believe there are 2 different uses of foam for different boats.

alum boats usually will get more water under the deck and should always have a way for water to ran back to get pumped out. so loose closed cell foam is the way to go.

fiberglass boats seem to be a tighter deck and most water runs over the deck to the bilge area and expandable foam seems to offer some stiffness to the deck

but for boats under 21 ft i believe you would want positive floation

 

[Lone Duck]

Re: Why Foam?

HUMMMM! I guess I keep thinking wrong. To my way of thinking I would want the flotation foam up near the gunnels .Then if you punch a hole in her, the foam stops it from turning turtle. With the foam in the bottom it will definitely roll over putting you in the water. Then try and climb out of the water and on to your hull.

 

[tallcanadian]

Re: Why Foam?

It's better to have foam and not sink, than not have foam and sink. You never know when an accident can happen. It may not be your fault, but. It's like a car with airbags. You know they are there if you need them, but you may never ever need them....hopefully.

 

[dorelse]

Re: Why Foam?

It's better to have foam and not sink, than not have foam and sink. You never know when an accident can happen. It may not be your fault, but. It's like a car with airbags. You know they are there if you need them, but you may never ever need them....hopefully.

Yeah, I put the foam back in for 3 reasons...1) liability protection (ie...boat sinks, I've removed the foam...30 gals of gas leaks out...DNR sues my ***** off for neglience for removing the foam.) 2) Safety...Mom & Dad are injured in an accident...kids have that floating island to stick with 3) Sound deadening & firming up the floor...its supported fine without it, but, its more solid with it in.

Its well ventilated, and I've sealed everything wood really well. Do I want water in there? Of course not...but I've built it to last my lifetime, so I'm not concerned beyond that!

 

[Bondo]

Re: Why Foam?

Not waterproof but sealed. Also, if you punch a hole in your hull in a sealed compartment that someone put a limber hole in the stringer for it to drain you run the chance of your boat going completely under. If the hole is big enough there isn't a bilge pump made that will save you. If you have done the build properly you should never get water in those area's.

Ayuh,... With that thinking, you're setting yourself up for a Rotten boat...
A Sealed compartment WILL get water in it, from condensation if nothing else...
With Nowhere for it to go, it Rots the wood...
If it's a Drained compartment, it'll drain,+ dry out....

As for Punching a Hole through the hull,..??..?? Lets get serious here,...
This is a discussion about the Facts of Life, not spinning some political point...
Just how many Holed hulls have you seen,..??..?? Danm Few, if Any....
To Hole a regular glass hull, you need to hit something with such force, that the operator is already deceased...

If you Insist on using Foam,.... Drain it....
Otherwise you're rebuilding your hull to the same, or lower standards than Bilgeliner built it to in the 1st place,..
Which is WHY it Rotted out in the 1st place...

** I believe it is mandatory to have it in a vessel under 21ft

Only if you are an OEM Manufacturer....

 

[Spinnaker]

Re: Why Foam?

I guess boats are built differently here than in N.Y. The only boats I've had limber holes drain from beyond the stringers to the bilge are from the yachts I've built. Never have I seen a small pleasure craft with a drain from outside the stringers to the bilge area. Larger boats with larger diesel engines and direct drive can pull water from the bilge for cooling in an emergency. But I guess my status is "Cadet" with 29 posts so what do I know? Ayuh!

 

[Bondo]

Re: Why Foam?

The only boats I've had limber holes drain from beyond the stringers to the bilge are from the yachts I've built. Never have I seen a small pleasure craft with a drain from outside the stringers to the bilge area.

Ayuh,... Which is Why most of Us here are rebuilding our barges...

As somebody's signature here at iboats states,...
"Just because you found it that way, Don't mean is Should be that way"...

I donno about You,...
But, I advocate rebuilding your barge to Better standards that most commercial boat builders use...
And,..
That would include limber holing the Entire Hull...

 

[Spinnaker]

Re: Why Foam?

Ayuh,... Which is Why most of Us here are rebuilding our barges...

As somebody's signature here at iboats states,...
"Just because you found it that way, Don't mean is Should be that way"...

I donno about You,...
But, I advocate rebuilding your barge to Better standards that most commercial boat builders use...
And,..
That would include limber holing the Entire Hull...

OK Bondo, after your last statement I'll agree. I certainly don't want to get into a pissing match. Also need to get this thread back on topic.

 

[noworries79]

Re: Why Foam?

Never have I seen a small pleasure craft with a drain from outside the stringers to the bilge area.

This is the same line of thinking that my boat's manufacturer had, when I cut out the deck there was 3 inches of water trapped under the water-logged foam and 2 inches of water outside the stingers with no way to reach the bilge!!! I estimate that I had an extra 100+ lbs. riding around with me for years, not-to-mention all the rotten wood I am replacing.

I am thinking of starting a new boat building company and hiring all these guys. If you know of any investors give me a shout!

 

[bankfisher]

Re: Why Foam?

I am thinking of starting a new boat building company and hiring all these guys. If you know of any investors give me a shout!

But what happens when boats don't rot? No one needs a new one!!!
And we run out of projects!!!

 

[um0RION]

Re: Why Foam?

I had an idea a couple weeks ago... For floatation in a boat, most boats have the flotation foam. This foam for the most part is in the sealed compartments under the deck.

Why not use something like ping-pong balls?

Fill an area with ping pong balls, then seal them up under the deck. If the area ever got wet, the ping pong balls would hold their integrity, and allow water to fully drain, while maintaining good floatation (Hey, mythbusters raised a boat doing it).

You would also save a lot of weight I imagine, ping pong balls dont weigh much at all.

Pricewise it might be hard to justify ($100 for 1,440 ping pong balls (ebay)) but wouldnt it be easier than foam?

Am I nuts?

edit: 15 ping pong balls per lb. Haha noooot too practical.

 

[noworries79]

Re: Why Foam?

But what happens when boats don't rot? No one needs a new one!!!
And we run out of projects!!!

We go FISHING!!!!!



um0RION,
Not at all, it's a good concept. I, as well as a few others, have considered using pool noodles as our floatation. I plan to cut a PVC to keep the noodles above the drain channels.