Do I need to add foam or other flotation?

[aeviaanah]

It really is very easy to figure out:
1 cubic foot of water weighs 62 pounds
1 cubic foot of 2 part closed cell foam weighs 2 pounds
So, 1 cubic foot of foam gives 60 pounds of buoyancy
1000 pounds (full boat) / 60 pounds of buoyancy = 16 cubic feet of foam required
That is roughly a 4 gallon kit of two part foam; 960 pounds of buoyancy... Each 2 gallon kit is 8 cubic feet of cured foam.

The requirement for "upright and level floatation" mandated by the USCG is intended to keep the vessel, when completely swamped, right side up. Depending on the weight/ballast distribution of the hull this could mean as much as 30% of the buoyancy foam above the lateral center of gravity (COG). IOW you may need to add foam higher than just below the sole. The best places to take the foam above the lateral COG are at the four (or three) corners; port and starboard at the transom and either port and starboard at the bow or just a nice big area at bow (if you have a 'pointy' bow). Be careful when using foam that is not USCG approved. Not all foams are created equal; some will break down in contact with fuels/oil, some will absorb water faster etc... USCG approved foams have been tested for these conditions and are known to work.

Foam could save your life and may be required in some states and on some bodies of water regardless; but you should also consider the next owner. If you sell the vessel and loss of life, limb or property results from the modifications you have made it will open you up to liability; both criminal (less likely) and civil (more likely).

I'm not a lawyer, but I play one on the internet!

I bought a 2" x 4' x 8' sheet of polysterene. Do you happen to know how much buoyancy that gives at 1 cubic ft? Thanks for the great post, much easier to understand... now I feel confident to provide ample amounts of foam for my vessel.

 

[plt3145]

All who posted responses and rebuttals..thankx! =D> Real good question with a lot of valuable feedback and actual first hand insight! Haven't started my remod yet but I am mooching ideas and intel from you all! :idea: Thanks again, phil from Aulander!

 

[richg99]

Interesting discussion. Made me wonder if a modified/combined solution would be best.

Make up packs of air-tight Soda bottles. Glue them together with foam. Best of both worlds. Bottles take up most of the space; foam fills in the crevices. Since foam can, over time, absorb water...this system lessens the potential for future water-soaked foam issues.

Never tried it and probably never will....but...what do you guys think?

You could make up the "packs" to any size or dimension that you wanted...by selecting the right sized plastic bottles and laying them flat like a sheet...or taller as needed. No matter what system you use, the foam/bottles/foam&bottles have to be secured to the storage space so nothing floats away.

regards, R

 

[earl60446]

It really is very easy to figure out:
1 cubic foot of water weighs 62 pounds
1 cubic foot of 2 part closed cell foam weighs 2 pounds
So, 1 cubic foot of foam gives 60 pounds of buoyancy
1000 pounds (full boat) / 60 pounds of buoyancy = 16 cubic feet of foam required
That is roughly a 4 gallon kit of two part foam; 960 pounds of buoyancy... Each 2 gallon kit is 8 cubic feet of cured foam.

The requirement for "upright and level floatation" mandated by the USCG is intended to keep the vessel, when completely swamped, right side up. Depending on the weight/ballast distribution of the hull this could mean as much as 30% of the buoyancy foam above the lateral center of gravity (COG). IOW you may need to add foam higher than just below the sole. The best places to take the foam above the lateral COG are at the four (or three) corners; port and starboard at the transom and either port and starboard at the bow or just a nice big area at bow (if you have a 'pointy' bow). Be careful when using foam that is not USCG approved. Not all foams are created equal; some will break down in contact with fuels/oil, some will absorb water faster etc... USCG approved foams have been tested for these conditions and are known to work.

Foam could save your life and may be required in some states and on some bodies of water regardless; but you should also consider the next owner. If you sell the vessel and loss of life, limb or property results from the modifications you have made it will open you up to liability; both criminal (less likely) and civil (more likely).

I'm not a lawyer, but I play one on the internet!

I bought a 2" x 4' x 8' sheet of polysterene. Do you happen to know how much buoyancy that gives at 1 cubic ft? Thanks for the great post, much easier to understand... now I feel confident to provide ample amounts of foam for my vessel.

I believe that would be 5.33 cubic feet of flotation 2 / 12 * ( 4 + 8 ) = 5.33333333...
so according to the other poster, multiply that by 60 and you get 320 lbs of flotation.
Don't seem like enough, does it? But maybe it would be with the water buoyancy factor.
Tim

 

[aeviaanah]

First I figured sq inches of under seats. I left half of the back seat open for storage.
The first equation represents the rectangular portion of the seat, the second is the slanted area on edges of seat near side of boat. Each side is roughly half of a rectangular box. This helped get a better estimate of total sq inches.

Front seat -
10 x 9.5 x 34= 3230 sq in
7.5 x 4 x 9.5 = 285 sq in

Middle seat
10 x 9.5 x 42 = 3990 sq in
9.5 x 6 x 9.5 = 541 sq in

Half of back seat
9.5 x 9.5 x 20.5 = 1850 sq in
(9 x 6 x 9.5)/2 = 256 sq in

After adding all together I come up with 10, 152 sq inches. I divide by 1728 to convert to sq ft. I come up with 5.87 sq ft. Since the foam is not a perfect fit I will go down to 5.5 cubic ft of foam.
__

Now on to the total weight of boat. I have a 12' aluminum mod V. Similar models were between 140 and 160 lbs.

Boat weight empty
160lbs x (alum. factor .63) = 100 lbs.

Weight of motor 115lbs
Swamped = 105lbs

Weight of battery 45lbs
Submerged = 25lbs

Gear etc 100lbs

*I didnt figure weight of 6.6gal gas tank as they say gasoline is lighter than water so it will float.

Add all this up we get a total of 330lbs. Now i factored in the wood on boat.

I have 50 lbs of plywood.
50 (factor -.81)= -40lbs

330 - 40 = 290lbs.

To figure amount of flotation in cubic ft I took 290 and divided by 60.3. I come up with 4.80 cubic ft of foam required for boat weight.
I didnt figure in weight of persons as I just dont have enough room for foam...anyone who I take will need to be good at swimming and we do have life jackets. What do you guys think did I figure this properly?

5.5 cubic ft of foam in boat.
4.8 cubic ft of required to float boat.