Flotation - Again...

I did a search of the forums, but didn't find an good answer to my questions. Could have missed it, so pointers to other forum posts are certainly welcome.

Here's my situation: I am refurbing a 1988 Track Panfish 16. The old waterlogged foam under the floor has been removed, and the hull cleaned. The new floor is cut, epoxied, carpeted, and I'm ready to put in new foam before installing the new floor. I have pour foam I was planning to use. So far so good.

I wanted to make sure the drain channels in the bottom were clear to allow free drainage to the back where the bilge pump can pick up anything. So I though I'd put a barrier over the channels between the ribs and that would keep the foam from filling them in. I was using metal foil tape as it's waterproof. Then I got to realize that being sealed off, it won't let water into the drain channels either.

I could put dams on either side of the channels and make little compartments to pour the foam into. Or... I could use foam board from the hardware store like so many other have done. The problem I have with that is I don't know the flotation performance of that foam vs real pour flotation foam. I dont want to gamble with my boat, my gear, my life or that of my buddies.

So how have you guys solved this problem of new foam without blocking the drainage? The pink/blue foam board just seems a bit sketchy (althogh popular). Has anyone swamped their boat and seen it work first hand?

Thanks!

Ziggy

Welcome to TinBoats!

Disclaimer -- I have no idea if typical foam board has the same flotation characteristics as the two part foam you removed.

Seat of the pants -- could you put 1/2 foam board on top of spacers for drainage, then put the pour foam on top of that?

Keeping in mind my disclaimer, I personally, would use all styrofoam board in an enclosed spaces whenever I could. Except I would use two part foam if I thought it was needed for structural support and/or sound deadening.

Posting a pic of the interior might help folks give some recommendations.

Try a 2'x4' piece of foam board in a pool, will it support a 150# person ? If so then calculate how much you need. If you can install enough to support your boat weight, then your good to go...

A 2" thick 4' X 8' piece of Expanded Polystyrene foam board will provide about 310 pounds of flotation. That's the pink Owens Corning stuff you see in the home improvement store.

Here's the calculation on that:

Volume of the 2" X 48" X96" board: 9,216 cubic inches.

Convert the volume to gallons (9,216 / 231): 39.89 gallons

Weight of water is about 8 pounds per gallon. 39.89 gallons of water weighs about 319.1 pounds

The sheet of foam board weighs about 9 pounds.

319 pounds - 9 pounds = 310 pounds

If you use that foam, make sure you get the stuff that will not absorb water.

I kind of like the idea of thin foam board with pour foam on top. Then I can make sure I have as much foam under the deck as will fit.

But the data on the pink Owens Corning foam is interesting.
If that 9216 is converted to cubic feet, it's 5.3. And if it weighs 9 pounds, that's about 1.7 lb/cu ft.
The pour foam is supposed to be 2 lb/cu ft if expanded properly. The foam board is actually lower density.

So it would seem that the two compare favorably.
Actually, I just looked @HD site and the spec is 7.5 lb for 2"x4'x8' Foamular NGX - even more interesting. It's also rated for below grade service and is supposed to be 'highly moisture resistant'. Owens-Corning says: "Non-diluted gas can affect the Foamular". So that's the down side I guess. I dont expect to have undiluted gas in the bilge in any quantity. Something to watch out for I guess.

Thanks for the good feedback guys. It helps alot.

I use the expanded polystyrene in my 14' tinnie. Spilled fuel and fumes is not a concern for me as I do not have an integral fuel tank.

The foam board is also cost effective.

I thought the Tracker panfish was a mod-v jon boat. If so, I wouldn't think there was much space betweem hull and floor. Using the boards would be easier than pour in.

Yes, it's a modified V. And yes, there isn't a lot of space underneath. So with the information learned about the buoyancy, I feel better about using the foam board. My fuel tank is portable, so like Ray mentioned the fuel situation doesn't seem to be of too much concern. I'm using all new large wafer head screws on the new deck so I could pull it again to inspect if I feel the need. I'll fill in some more spaces in the side compartments and the front with the pour foam. On this model they aren't used for rod lockers or anything. Looking forward to finishing this up quickly before the season is over. Thanks again.

On your boat, the foam panels will span across the center and allow draining and a nice air gap between hull and foam. Or if plywood floor, may opt for air gap between foam and floor.

If those side panels have no storage and are full of foam, the floor is probably just insurance.

Do you have a build thread going?

I have never really understood why the manufacturers use a foam that can become so waterlogged. Maybe the pour foam they use is better suited to their manufacturing process, or perhaps the expanded polystyrene can only be produced in a closely controlled manufacturing process.

Ray Clark said:

I have never really understood why the manufacturers use a foam that can become so waterlogged. Maybe the pour foam they use is better suited to their manufacturing process, or perhaps the expanded polystyrene can only be produced in a closely controlled manufacturing process.

Click to expand...

I know the old white styrofoam sheets became a sponge in my '67 Starcraft. I made the mistake of re-using the dry sheets, and that became a sponge. It only got wet when it was moored and had a heavy rain, and was pumped out the next day. Otherwise, it was on an angled trailer with drain open and tarp cover. I hope the more modern blue / pink foam holds up much longer.

Be careful of those fumes when mixing the foam: OVERDOSE

FuzzyGrub said:

I know the old white styrofoam sheets became a sponge in my '67 Starcraft. I made the mistake of re-using the dry sheets, and that became a sponge. It only got wet when it was moored and had a heavy rain, and was pumped out the next day. Otherwise, it was on an angled trailer with drain open and tarp cover. I hope the more modern blue / pink foam holds up much longer.

Click to expand...

It will...used it around my foundation on my home. After 25 yrs still not holding any water.