I need this explained simply: how does foam attached INSIDE the boat help flotation?

[bob johnson]

You may want to read this link below "styrofoam" is a very general term, the white expanded cell styrofoam sold at hd would be better at soaking up water then keeping it out..
https://www.boatdesign.net/threads/polyurethane-foam-water-absorption.35963/page-2

I cant control improper use of "terms"... and here say.....

but Ive seen and been around blue dock foam long enough to know it doesn't get heavier....

http://www.dockbuilders.com/dow-styrofoam-billets.htm

and its called STYROFOAM!


the article you posted to....says the two part sucks... and I agree...and its NOT called Styrofoam!...... and it even goes to say the best stuff is the blocks pre made....ie... dock Styrofoam!

 

[shaw520]

No Title

..as ive indicated above.
Heres an example of 3 types of "styrofoam" obtainable at hd,..the only one that will provide somewhat sustainable floatation is the one in the middle.

 

[shaw520]

the article you posted to....says the two part sucks... and I agree...and its NOT called Styrofoam!...... and it even goes to say the best stuff is the blocks pre made....ie... dock Styrofoam!

I agree with your statement above,..and i also agree that not all "styrofoam" or foam is good for floatation.

 

[shaw520]

..also,... block foam used under docks, although provides very good flotation,...it is a bad comparison to foam beneath the deck of a vessel. Dock foam, while floating on water, leaves a very small portion of the foam in contact with water,...while the remaining majority of the foam is in open air and exposed to very rapid evaporation rates,....a poor simulation to the conditions below deck,...where the foam may be completely submerged in water for very long periods of time with very slow, if any evaporation.

 

[garbageguy]

Interesting discussion. I think it was said early on, volume and weight - so, density is the key here. As long as your flotation material is less dense that water, always, it will exert an upward foce when submerged in water. As was also noted, flotation material within the hull, can't help float the boat till there's water IN the boat.

 

[ajgraz]

Think of it like a life jacket. Your life jacket doesn't help you float when you're standing on the deck, but it does after you've fallen in the water.

 

[Texasmark]

Used to be that ships were measured that way, by how many gallons of water the hull displaced from a known source....weighing the water...wt/gallon x gallons displaced.

An object in solution (water) will fully submerge and retain buoyancy......doesn't sink further, nor surface, if it's weight equals the weight of the water it displaces.

An object floats upon the water at a depth that is equal to the weight of the water the boat displaces and that depth depends upon the area of the water displaced. Heavy, small objects float deep, partially submerged whereas large area, light objects float on the water.

An object sinks at a rate that is proportional to the weight of the object vs the water it displaces where the object is heavier than equilibrium.

Flotation inside a boat does nothing but add weight to the hull when buoyant. When submerged (boat attempting to sink) it displaces more water per unit volume than the boat and it's amenities which makes the boat lighter and if correct, allows it, or at least part of it to float. Again, the height at which it floats is dependent upon the wt-volume submerged ratio.

That't the way I remember it. I didn't read any other's answers because I wanted to remember the way I learned it.

 

[bob johnson]

you( the foam) needs to displace the amount of water that would weigh as much as all the parts and contents of the boat....and then a little more to make sure when totally swamped or over turned... the boat does not sink to the bottom..leaving you swimming....I use my boat in the winter and colder weather...mostly hunting waterfowl..i have chest waders...it is possible for my boat to flounder and take on wave after wave until it is swamped...assuming the motor doesn't run and I can still stand in the boat and the water wont go over my waders...because I have installed enough flotation foam...and that may give me time to assure help is on the way.....if I was in the water swimming, even with a life vest....id probably die of exposure before help arrived........that is called LEVEL flotation....keeping the boat level at the waterline... at the very least a swamped boat is at least something to hang onto , and gives rescuers a larger target to look for!!

 

[shaw520]

And then for some added protection,...you could stick some of that flotation foam down yer waders! ;-)

 

[JASinIL2006]

Ive used the pink board in a couple build also and has proven to be quite water resistant,.. But even closed cell foam. once cut with a saw or knife will allow some extent of water penatration no?

No, it does not. The closed cell structure is throughout the material, not just on the edges.

 

[JASinIL2006]

..also,... block foam used under docks, although provides very good flotation,...it is a bad comparison to foam beneath the deck of a vessel. Dock foam, while floating on water, leaves a very small portion of the foam in contact with water,...while the remaining majority of the foam is in open air and exposed to very rapid evaporation rates,....a poor simulation to the conditions below deck,...where the foam may be completely submerged in water for very long periods of time with very slow, if any evaporation.

Nonsense. My deck has foam supporting a pretty substantial wooden structure. As such, at least 75% of the foam is in constant contact with the water and it does not saturate.

 

[shaw520]

What I say is nonsense ??,...Yet you provide zero details to your claim,... help me understand,...first off, when you say "your deck" are you referring to a floating dock or the deck of a vessel,..big difference.

 

[shaw520]

I think the discussion that we are having here, (well at least the discussion that im having) is weather closed cell foam can become water saturated,...and I have pulled enough saturated 'closed cell' foam from many different boats that I can say with certainty that indeed it does become water saturated,...read the link Ive provided above, it may shed some light.

 

[bob johnson]

And then for some added protection,...you could stick some of that flotation foam down yer waders! ;-)

no it goes on your neck...ie... SOS life vest

 

[redneck joe]

should we re title this thread to

"my foam is better than your foam'

op2:

 

[bob johnson]

each one of those "sections" is about 1 cubic ft of foam... when I cut one out as best I could intact, it weighed about 16 lbs..instead of the 2 lbs the foam normally is supposed to weigh..... this foam was blown in as 2 part expanding foam by LOWE BOATS after they have the floor in place..... it took only about 7 years to get like this.....the whole 'rig' had gained 600 lbs..... my tires were bulging at 50 psi!!....I surmised it was water in the boat.......sure enough I was dead on....

closed cell, open cell... ridged, expanding..yada yada yada....I know that blue dow corning dock foam absorbs NO water, and neither does the boards I bought at home depot.....ive cut up both and fitted them into my boat rebuilds as packed as I could get them........everyplace I could find to put it as well..

 

[JASinIL2006]

I think the discussion that we are having here, (well at least the discussion that im having) is weather closed cell foam can become water saturated,...and I have pulled enough saturated 'closed cell' foam from many different boats that I can say with certainty that indeed it does become water saturated,...read the link Ive provided above, it may shed some light.

Sorry... dock, not deck. Closed cell foam of the type blue- or pink-board insulation generally doesn't take on water, nor does the pour-in type, unless the cell structure is compromised. Common way for that to happen is for it to get wet, be exposed to freeze-and-thaw cycles where the foam structure is compromised, and then water keeps working in as more and more the closed cells rupture. Just putting that stuff in water will not cause it to saturate.

 

[shaw520]

. Common way for that to happen is for it to get wet, be exposed to freeze-and-thaw cycles where the foam structure is compromised, and then water keeps working in as more and more the closed cells rupture..

Well there go,..youve just described the enviroment in a typical sub-deck of a vessel. Now ad the constant flexing and beating the typical sub-deck is subject to and theres really no wonder why any type of foam can become water saturated.

 

[bob johnson]

Well there go,..youve just described the enviroment in a typical sub-deck of a vessel. Now ad the constant flexing and beating the typical sub-deck is subject to and theres really no wonder why any type of foam can become water saturated.

ok...there you go....its junk....use the blue dock foam or the hard board insulation and you don't have to worry about flexing or freezing

 

[shaw520]

No, it does not. The closed cell structure is throughout the material, not just on the edges.

ok...there you go....its junk....use the blue dock foam or the hard board insulation and you don't have to worry about flexing or freezing

Look,...some boat manufacturers to a better job of diverting water out and away from the stringer/hull/sub-deck cavity than others,..but it is my belief that eventually all sub decks will infiltrate water, 10, 20 even 30yrs, (in trawlers and larger vessels 30 yr old boats are plentiful),...of course wood decks much sooner than glass decks,..but eventually they will all at some point get water in them. When someone can show me a 20 yr old berth/deck torn up, that shows obvious signs of water intrusion and the pink/blue or whatever foam is dry????.....then I will believe what you are trying to get everyone here to believe.