TO FOAM OR NOT TO FOAM????? That is the question

[jdvasher]

I am currently rebuilding a 1968 StarCraft Holiday and I am debating on foam or no foam. I ran some calculations on the volume and even if I filled the entire below deck cavity with closed cell foam it would not be enough to float the boat. This seems very odd to me because, whats the point? I know it would make for a quieter ride but it would also be a huge pain in the butt if I ever needed access under the deck. I am coming up with around 148 gallons or 19.8 cf of space. That would only displace a little over 1200 lbs not counting the weight of the foam itself. I haven't weighed the boat from what I have found it should come out around 1400-1600 lbs. I'm really surprised that this was not factored into the original design.

Am I missing something here?

Thanks
JD

 

[racerone]

Have you factored in the buoyance of the materials of the boat itself ?-----Aluminum is not as heavy submerged in water as it is out of the water.

 

[GA_Boater]

I'm really surprised that this was not factored into the original design.

Am I missing something here?

Thanks
JD

Are you sure it wasn't part of the design? Flotation was per CG regs in effect when the Holiday was built. Leaving flotation out of your Holiday means if you happen to hole the bottom, only a bilge pump might save you and the boat. It better be a big one if the hole is large!

What are you missing? The purpose of the flotation foam is to keep the boat awash long enough for you and passengers to be rescued, not to keep the boat from sinking.

You had styrofoam blocks under the deck, not expanding foam. Styro sucks because it gets saturated with even the smallest amount of water under the deck. Either pour-in foam or closed cell insulation cut to fit is better than styrofoam.

 

[jdvasher]

Are you sure it wasn't part of the design? Flotation was per CG regs in effect when the Holiday was built. Leaving flotation out of your Holiday means if you happen to hole the bottom, only a bilge pump might save you and the boat. It better be a big one if the hole is large!

What are you missing? The purpose of the flotation foam is to keep the boat awash long enough for you and passengers to be rescued, not to keep the boat from sinking.

You had styrofoam blocks under the deck, not expanding foam. Styro sucks because it gets saturated with even the smallest amount of water under the deck. Either pour-in foam or closed cell insulation cut to fit is better than styrofoam.

With that much of a weight difference, there is no way this boat will float, even for a little while. That was the point I was making.

 

[jdvasher]

Have you factored in the buoyance of the materials of the boat itself ?-----Aluminum is not as heavy submerged in water as it is out of the water.

I did not account for materials on the boat, Im sure there will be some buoyancy in the fiberglass, foam core flooring that I am going to install.

You bring up a good point and its probably where I went wrong. If I am looking at this right, I would need to calculate the weight and volume of the boat to come of with the density and then compare to water by itself... does this sound right?

 

[GA_Boater]

With that much of a weight difference, there is no way this boat will float, even for a little while. That was the point I was making.

Stop thinking and put foam under the deck, again either pour-in or closed foam insulation.

Read this Coast Guard Boat Builders Handbook if you need to understand how the Coast Guard determines flotation requirements.

 

[chevymaher]

I went through this on mine the calculations. Fiberglass just about float all by its self. wood does float so it is canceling alot of that. Iron the densest material used is only 85% of its weight under water. aluminum is less.

So once you figure that in. People float so their weight is a scratch. Just got to keep the boat up.

2 lb foam is 20-30 times the volume you buy once it expands. I got a ton of it left.

Biggest thing is the structural rigidity it adds and the muffling of noise. Do you want to ride in what sounds like a rattle trap Vega or a quiet Cadillac.

If you put back what you took out it will float. I added all over where I could. Sound deadening.

 

[harringtondav]

The foam will displace water if you get fully swamped. If you run your calcs again without the water volume the foam displaces, I suspect you won't sink.

 

[Ned L]

I did not account for materials on the boat, Im sure there will be some buoyancy in the fiberglass, foam core flooring that I am going to install.

You bring up a good point and its probably where I went wrong. If I am looking at this right, I would need to calculate the weight and volume of the boat to come of with the density and then compare to water by itself... does this sound right?

yes, you are on the right path there. You do not need to displace a volume of water equal to the weight of the boat and gear on land. What you need to do is to add enough foam in order to bring the specific gravity of the total volume (boat, gear, outboard and foam) to less than one. Then it will stay afloat.

 

[Scott Danforth]

remember, starcraft had to prove it floated to be able to manufacture. so if you put back what was taken out...... your golden

 

[Teamster]

You do whatever you want,...

I've never drowned, So I can't say for sure, But I'm guessing it isn't fun.

If you do go down and someone dies hope you are among the dead, How would
you live with it if you survived???

 

[Chris1956]

Gee, I agree with the others. Foam it. You can put some foam under the gunwales as well as any open spaces.

My speedboat sunk in a storm. The bow floated due to a chunk of foam, engine was on the bottom. I was able to re float it and rehabilitate it.

 

[jdvasher]

I have decided to foam it, I will go with foam sheets laminated together instead of expanding foam though. Throughout the entire restoration, one main goal has been on my mind and has played a major part in my decisions. This is an old boat, with rivets, There is a good chance that it will need repairs at some point. I have laid out the floor for removable panels for this reason so I just cannot see filling will expanding foam. I am not sure how to add this info to my signature yet but if anyone is interested, here is a link to the resto.. https://forums.iboats.com/forum/boat...ay-restoration

 

[Scott Danforth]

you loose the structural element and the sound deadening element of foam by not going 2-part expanding.

 

[The Force power]

you loose the structural element and the sound deadening element of foam by not going 2-part expanding.

True on the structural part but the only expansion foam that I know; soak up water

 

[Scott Danforth]

all foam will break down if in contact with water and freeze/thaw cycles and soak up water.

 

[jbcurt00]

True on the structural part but the only expansion foam that I know; soak up water

That takes time, exposure to the elements and neglect. Not a forgone conclusion.....

 

[The Force power]

Another lesson learnt

 

[kcassells]

all foam will break down if in contact with water and freeze/thaw cycles and soak up water.

So to understand freeze/thaw breaks the closed cells of 2 part foam.
Is that correct?
Freeze meaning water is under the deck in the freeze months with no drainage and pools up and destroys the whole concept of poured foam.
Is that correct?
Closed cell foam is not viable in a freeze thaw scenario whereas the best method of protection is of course to keep your boat in a heated space.
Is that correct?

 

[Scott Danforth]

So to understand freeze/thaw breaks the closed cells of 2 part foam.
Is that correct?
Freeze meaning water is under the deck in the freeze months with no drainage and pools up and destroys the whole concept of poured foam.
Is that correct?
Closed cell foam is not viable in a freeze thaw scenario whereas the best method of protection is of course to keep your boat in a heated space.
Is that correct?

the foam is no different than an engine block. put water in a motor, subject it to freezing temperatures and the block cracks.

foam and water in an enclosed space, once it freezes, the water expands and some of the closed cell walls rupture and its no longer closed cell foam, so the space available for water to sit gets larger. over time, much of the foam is damaged and it becomes mostly open cell foam. this is known as a sponge.

eventually the amount of water in the cavity gets large enough that freezing actually ruptures what ever the foam/water was in.

the same thing happens to transoms and stringers on fiberglass boats.

in nearly all cases, neglect to pull the plug or neglect to seal a compartment or neglect to fix a hull breach are what leads to wet foam.

the key is to encapsulate the foam to prevent is exposure to foam, or to keep water out to begin with.

since nearly every boat I restored had wet foam, usually from either someone drilling a hole where it shouldnt be and not sealing it, or someone leaving the plug in and filling the whole boat up with water repeatedly. i dont blame the foam. I blame the lack of proper maintenance/operation

the 50's tinny fishing boat I have with foam under the seats is the original foam. pull the plug when your done fishing and water cant get to the foam. its been there for nearly 70 years and it will be there to float the boat should I ever have an incident where water does get high enough within the confines of the gunwales to need it to float the boat.

BTW........PFD's also break down when exposed to UV, water and freezing temperatures.