Spray foam for flotation?

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daschmetterling

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We haven't made much progress on our project- still in the planning and material aquisition phase (and hunting season). We will be running conduit under our floor and filling the rest of the space with foam, either the blue or pink sheets. I was wondering if there was another option of a spray foam to get the maximum amount of flotation. Any thoughts? Thanks in advance!

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Spray in? Not that I know of, that's any good anyway ...

Pour in? See https://www.uscomposites.com/foam.html , just be aware that if/when you pour too much into an otherwise enclosed cavity that the expanding force can POP that area or bulkheads .... or in a tin boat ... the hull!

Awesome stuff though, have used it in many frp boats.
 
DaleH- This is great information, thank you. I have heard of the pour in, but I didn't know what people were talking about. Any ideas on which type- 2lb - 16lb density, according to your link? Thanks again!

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The pour in foam is good stuff and the 2lb is all that is needed. The best price I have found is here.
https://www.mertons.com/Floatation/index.html

It can and will fill a cavity completely so depending on how you do it you will want to leave a way for any bilge water to drain back.
 
bonz_d said:
It can and will fill a cavity completely so depending on how you do it you will want to leave a way for any bilge water to drain back.
A length of PVC ripped in half is one way to ensure limber holes and drainage is in place ...
 
^^^^ Exactly. Be sure to plan on drainage for the decking if it's backed by poured foam. I didn't plan for enough of this in my build & now I have to go back in & figure out how to get rainwater to the bilge in the rear efficiently.

My current drains take too long and are prone to clogging. I ran vinyl hosing under the support ribs but was limited to 3/8" hosing & this has not been enough volume to drain the deck area between the benches. I'm still looking into options, but the more I think about it the more I don't want to think about how much I'm going to have to tear apart to fix it.

After looking into PVC drains built into fiberglass boats I'm seeing manufacturers using no smaller than 1.5" pipe - likely due to avoid debris clogging the pipe.
 
There are certainly many different ways to accomplish a drain raceway. The problem when it comes to expanding foam is that it tends to find it's way into the tube and blocks it's ability to move the water..
 
onthewater102 said:
After looking into PVC drains built into fiberglass boats I'm seeing manufacturers using no smaller than 1.5" pipe - likely due to avoid debris clogging the pipe.
Yes, I always glassed in 2" PVC halfs to ensure proper drainage. Never had a clog or issue.

On frp 'offshore' boat transoms, I'd also drill out the small 1" drains and glass in 2" PVC scuppers/drains. They allow 4X the amount of water to exit ... look at the performance increase below, as measured in gallons per minute per scupper tube, or as pounds of water) (crucial for offshore boats :shock: ) by the bigger diameter.

This is based upon the scientific principle involving the 'drag' of water, as pictured ...
 

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bonz_d said:
The pour in foam is good stuff and the 2lb is all that is needed. The best price I have found is here.
https://www.mertons.com/Floatation/index.html

It can and will fill a cavity completely so depending on how you do it you will want to leave a way for any bilge water to drain back.
Fantastic- thank you, bonz_d!

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onthewater102 said:
^^^^ Exactly. Be sure to plan on drainage for the decking if it's backed by poured foam. I didn't plan for enough of this in my build & now I have to go back in & figure out how to get rainwater to the bilge in the rear efficiently.

My current drains take too long and are prone to clogging. I ran vinyl hosing under the support ribs but was limited to 3/8" hosing & this has not been enough volume to drain the deck area between the benches. I'm still looking into options, but the more I think about it the more I don't want to think about how much I'm going to have to tear apart to fix it.

After looking into PVC drains built into fiberglass boats I'm seeing manufacturers using no smaller than 1.5" pipe - likely due to avoid debris clogging the pipe.
Great information, thank you!


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Thanks guys for posting this info. It's perfect for my build.

Sent from the dust in front of you!
 
Not trying to rain on anybody's parade, but be sure the spray in or pour in foam doesn't become water saturated. I've seen the pour in foam and the spray in foam, over a period of time exposed to water, will eventually become water saturated and become very heavy. And it really sucks digging this stuff out after a few years.... Especially water soaked... Ask me how I know.... A buddy of mine couldn't figure out why his boat kept losing speed. Come to find out the foam had become water saturated and was adding ALOT of weight to his boat.

1Aquaholic
 
That is why the drainage is so important. You should never leave water standing in your boat - that's a surefire way to give it time to permeate the foam.
 
This is for Onthewater (and anyone else with his problem).

I don't know if this will work, but don't see any good reason why it won't either.

Back when I messed around with foam model airplanes, I built a device to cut wings out of blocks of foam. It was really nothing more than a thin wire, stretched over an old-fashioned bow saw. It was attached to a battery charger. For the airplane job, we made up two pieces of plywood template matching the airfoil. We then simply ran the wire over the plywood templates to cut the shape out of the foam.

Given that, I don't see why a half circle of wire, backed by a frame of plywood, and slowly slid along the aluminum deck wouldn't cut a channel for your water flow. Add a battery or a battery charger to heat the wire, and my bet is you could cut the channel with minimal physical work.

What do you all think??? richg99
 
1Aquaholic said:
... but be sure the spray in or pour in foam doesn't become water saturated.c
Installed properly, USCG/marine quality 2-part urethane closed-cell foam will skin over and not absorb water. In worse cases, same marine quality foam would only absorb 10% of its own (foam) weight in water through 'perimeter permeation', says US Composites ... and it takes decades to do that.

That said, I have no doubt that 'cheap' foam could absorb almost its full volume of water ... in years.
 
1Aquaholic said:
Not trying to rain on anybody's parade, but be sure the spray in or pour in foam doesn't become water saturated. I've seen the pour in foam and the spray in foam, over a period of time exposed to water, will eventually become water saturated and become very heavy. And it really sucks digging this stuff out after a few years.... Especially water soaked... Ask me how I know.... A buddy of mine couldn't figure out why his boat kept losing speed. Come to find out the foam had become water saturated and was adding ALOT of weight to his boat.

1Aquaholic

Find it hard to argue with any of your statement other than it's not just the pour in foam that will become compromised if left in direct contact with water. The sheet foam will also as will any wood. Only advantage is that the sheet foam is easier to remove.

Also remember that floatation foam was actually meant to be "level floatation" in that if a vessel becomes swamped the floatation is supposed to keep the hull level and not capsize or have either the bow or stern under water. So that in the event that a tragedy happens the occupants can stay safely inside and with the vessel until help arrives.

With this in mind it is also why now you see more and more boats built with the floatation boxes running the length of the sides and as high as possible.
 

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