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Good advice Bbb.

Just to reinforce the thought - I was hit by another boat, never thought it could happen to me but it did.

Redundancy is a key element for safety. Extra foam fits in that category.
I looked at the lowes site, and they have a lot of foam building products. Are you folks talking about the foam board, or the rolls? A link would be greatly appreciated.
I used pool noodles in two side compartments at the stern of my Bayrunner. The three bench seats all still have the original (1982) foam blocks, still in good condition.

The pool noodles were used in the side compartments to allow access when needed (just pull them out - then replace when done). However, because of the holes in the center and the geometry when packing them in, I calculated I only get 1/2 the floatation I would if the compartments were solid with expanding foam. My project list includes doing something more effective, floatation-wise. Plastic bagging the noodles would work, as would some sort of inflatable "bags." Haven't decided yet.

Interesting thing I found out about my boat and floatation. A few years back I saw the tow service bring in an identical Bayrunner, with all factory foam in place. The guy had been offshore (in the Pacific) when hit by a rogue wave and swamped. The way he (owner) described it, the boat immediately flipped (floatation low). Floated great, just upside down
I think you cab get spray-on foam. If you apply it to the undersides of the deck & gunnels, then it may float upright.
Along with total amount of foam needed for flotation, I just figured out how much Total Boat pour foam to use per rib on each side for when I pour it under my deck.

You can use a wedge volume calculation to determine it. If you know the height (I have a center beam), then the two lengths (top and bottom) as well as the width of the rib, it can be calculated. In my case 1/2 quart of the mix (1/4 quart of each part) will expand to approximately .5 cubic ft.

I determined that my "wedge" averaged .67 cubic feet but if I lock in 2 pieces of 2" thick x 4" h x 10" long pieces of foam, I can reduce the wedge to .49 cubic ft and in the process, assure the foam does not creep over the center drainage opening between the ribs.

Here are a couple of online calculators if you want to figure it out on your boat:

Calculate the volume of a wedge in cubic ft: https://keisan.casio.com/exec/system/1322717681
I get 1152 cubic inches

now convert cubic inches to cubic feet here: https://www.google.com/search?q=convert+cubic+inches+to+cubic+feet&rlz=1C1SQJL_enUS844US844&oq=COnvert+cubic+inch&aqs=chrome.0.0j69i57j0l4.5933j1j7&sourceid=chrome&ie=UTF-8

That cuts me down to .6

Now if you are adding board foam to your wedge, you can cut down on the initial base lengths to get your total cubic feet down to where you need it. The reason I am doing that is that 1, 2 gallon mix of Total foam equals 8 cubic feet of foam. 2 gallons is 8 quarts so 1 quart of mix = 1 cubic foot. 1/2 quart of mix should fill 1 rib / side so I can do a total of 4 ribs with a 2 gallon mix. You get 300lbs of floatation per gallon so I'll get 600 lbs of floatation not even counting the sheet foam.

I will do 4 ribs (2 in the very back and 1 each where each seat mounts) and use sheet foam on the others.
If you are using pool noodles, I suggest that you replace them with real marine grade substitute. Pool noodles break down fairly fast. Heat is the issue,especially in a dry environment. They were made to stay wet,and yes they don't hold much water. And seem to float with a heavy load. Pourable foam isn't cheap. But IF you can figure out how much you need, then the cost may not be as expensive.
does anyone bother with marine grade floatation solid foam?


this seems like the "almost 3m thinsulate" threads in the van conversion forums.

minuteman 62-64; EVERYONE.

As I'm about to start restoring the STARCRAFT HOLIDAY 18 & will replace the whole floor & the floatation under it. - What DOES worry me is how to figure out HOW MUCH sheet foam I need to ASSURE that we float "right side UP" if we should get swamped "out on the salt".
(TRUST ME, IF we are out chumming-up large/hungry sharks to measure/tag/release we do NOT want to "go for a swim", should the boat swamp & flip upside down.)
The late/famous boat designer, NELSON SILVIA formerly of Wilmington, NC, used to say that MOST "stock boats" are MORE stable when upside down than the boats ever were when right side up.

Also, my math skills are POOR too.- Thus, I'm hoping the someone will help me figure HOW MUCH pink/blue floatation sheets that we need to install in the sides & under the forward deck to stay right side up, in addition to replacing the water-logged foam that is under the old flooring, should we get swamped by a wave/collision/another hazard.
(I presume that filling up every space under the floors with pink/blue foam, "cut to fit" will BE SUITABLE to replace the "soggy wet stuff".)

yours, tex
Couple of things I found out the hard way that I haven't seen mentioned in these pages:

I had to put a new floor in my older 19 ft Glastron runabout some years ago and used pour-in 2 part Urethane foam for the job. Going by recommendations at the time, I just used to-go drink cups for mixing - 1 each 16 oz to measure the parts, (to an inch or so below the rim) and a 32 oz to mix and pour with.

I did the floor on a warm, sunny summer day and had pre-cut 4" holes in the plywood floor about 3 ft apart, between the longitudinals. Jacked the front of the trailer as high in the air as I could get it, so's the foam mix would run downhill quickly. Watching that stuff was amazing....like the return of the Blob. Pour the 2 - 16 oz cups into the 32 oz cup, (just pour and go - you won't have time to scrape the cups clean) stir it quickly - you'll see the color change and you'll also see it very quickly start to rise in the cup. You gotta work fast.

Pour it into the lowest hole, wait a few seconds and you'll see it coming back up like a living thing as it expands. Kinda spooky/comical. I did it this way since I'd been warned that it would put extreme pressure in a closed container - enuf to rip my floor loose. My 32 oz at a time turned out to be right at the limit.....I heard that floor creak a few times but it did hold. I'd kept the hole saw disks and screwed a cross piece to each ahead of time. As the foam reached each hole, I jammed a disk into that hole and screwed it to the deck to keep the foam contained. "It happens fast ! ! !"

The difference in that boat was amazing. Previously, it was very noisy going thru chop, with the stringers slapping the underside of the floor. Now, it was rock solid and rigid and very quiet. I loved it.

As a follow-up, several years later I built a Sam Devlin design duck boat (original Black Brant - excellent design) for a friend and used the same stuff in the bow floatation compartment and in the rear sponsons. I built that boat in the winter in the northwest and it were cold. When I mixed and poured the 1st batch of foam, it didn't do anything. Oh, it did swell up some, but no more than 2 or 3 times its' original volume....not much good for floatation....and that stuff is expensive.

Finally figured out that it was the temperature.....dohhh. For myself when working with the epoxy on the boat, I'd taken a module out of a Kitchen Aid dishwasher that heated the air for drying dishes. (this was in the early '90s) I put that in a window to pick up clean air and it delivered nice warm air. Attached a 20 ft length of portable oxygen hose to it to carry that warm air to my face mask. Next batch, I put that plastic hose down in the hull with warm air blowing thru it to pre-warm the compartment and set the Urethane containers on the baseboard heaters for an hour or so, till they were nice and warm. Then mixed and poured and they acted as the stuff I used in the runabout did.
Thanks. I owned and operated a commercial appliance service (restaurant equipment) at the time and lots of stuff was available to me....and I like to play and invent stuff.

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