Hull Flotation Foam Question

I have a 1973 Century ski boat OMC IO powered. I have been told sometime in the past that the foam installed between the hull and the floor of the boat on these older boats tends to act like a sponge and soaks up a lot of water over time and adds much weight to the boat. I am not sure if I have this problem or not. Can anyone give some input on this subject? My boat is 19 foot and the hull design is something between a plaining and deep V hull.Top speed is 45 - 51 MPH :?:

 

Well, yes, sometimes that happens. In fact I am currently working on a research project for the Coast Guard to find out why because it ain't supposed to happen!

There are several ways to find out. One is to find out what your boat is supposed to weigh (the manufacturers listed weight) then go weigh the boat at a truck scale. You can get the boats listed weight from sources like BUCs Used boat guides, Blue book or NAPA used boat guides. If it weighs a lot more than it should then you might have a problem. Water weighs about 8 pounds per gallon, so if you have 20 gallons then that's 160 lbs. To do this right you need to take all the misc stuff off the boat. Skis, coolers, etc. Take the boat to a scale and weigh it. Take it to the lake and put it in the water. Drive back to the scale and weigh the trailer. Subtract the trailer weight. If you know how much gas is in the tank muliply the gallons by six lbs per gallon and subtract it from the boat weight. Or do it when the tank is near empty. Hopefully it should be near the listed weight. The other way is to gain access to the foam and take some of it out. You will be able to see if it is soaked or not.

That said, this problem did not occur much on boats built before 1995. In 1995 the EPA changed the rules for how foam is made, and the Coast Guard started see a lot of water soaked foam. Prior to that it onlly seemed to happen if the manufacturer didn't mix the foam correctly.

One other thing, on inboard boats built back then most of the foam was in the bow. Some might be under the floor and if any is water soaked then the foam under the floor would be the culprit. The stuff in the bow is probably ok. If you decide to replace it, it means taking up the floor, getting all the old foam out and replacing it. Another option is to try to dry it out. This usually means letting it sit on the trailer for months with the bow tilted up and the drain plug out (if you have one) or pumping collected water out. If there are no limber holes in the frames that run transversely in the bottom under the floor, this won't work. But it's worth a try during the winter when you're not using the boat. Just a word of caution, if you do this make sure the fuel tank is nearly empty, otherwise you'll have gas running out the fill and screwing up the gelcoat. What we used to do with boats that had this problem was stand them on their transom, but that's not very practical with a large ski boat.

 

Thanks Ike, I'll give it a shot.

Just thought you'd like to know, I previously purchased 3 or 4 used older boats for sterndrive parts etc. After I removed the parts I wanted, I cut the hulls up into small pieces with a sawsall and took it to the dump. I was supprised to find the foam from these boats to be very heavy (water logged) These boats were late 60's - early 70's .

 

Why does that not surpise me. Actually up until 2000 the law only require the boat to comply for 5 years after manufacturer, so any boat older than that didn't have have good foam. After 2000 the law was changed to 10 years. Now we have a problem because the stuff just doesn't last that long.

 

You'd think by now someone would have figured out how to make a waterproof closed-cell foam. It IS the 21st century after all....
The expanded urethane foam in my boat has held up very well for five years, still looks like new... then again, this boat lives on a trailer and I never let her carry more than a half-inch of water in the bilge, well, except for that one storm....

 

Well the answer to your comment is, they have. It's called block foam, that is foam that is machine made by the foam manufacturer and bought in blocks. Boats that use block foam do not have this problem. However, boat manufacturers prefer to use "pour foam". Two part foam that is made on the spot by mixing two chemicals and pouring it into the compartment, where hopefully it foams up and forms two pound density closed cell foam. It is easier to design compartments into the boat for pour foam, easier to install it, and results in less waste. Plus I'm sure the foam guys like to push it because then they can sell all the equipment needed to dispense the stuff as well as the chemicals.

This is where the problems start. The parameters for making two part foam are rather narrow. Most of this stuff is made with a foam gun, kinda like a spray paint gun. The gun has to be clean, and it has to be calibrated to get the right amounts of chemicals. This has to be done every day. In fact the better builders do it twice a day. Next problem, temperature and humidty. The foam manufacturers specify a temperature and humidity range. This can be a big problem in a boat plant in Wisconsin in January. The chemicals a often stored in unheated rooms. So first they need to be brought out and allowed to warm up to the plant temp. In the south the humidty can often be out of sight, and most boat plants are not air conditioned.

Now once you've shot it into the boat and it starts foaming, again you have a temperature problem. This is an exothermic reaction. It gives off heat which speeds up the reaction. Too much heat and it breaks the cells. So you don't get closed sell foam, you get something that looks more like broken glass. If you don't get enough heat in the reaction you get something that has the consistency of bread dough and looks a lot like a cow pie.

Then if you get beyond that and did everything right you have a boat with closed cell, two pound density polyurethane foam in it. So then we have to look at environmental factors. What is the envrionment in the boat that might cause foam to fail? First is shock and vibration. Boats pound and engines vibrate. All this is transmitted to the foam. Then there is heat and cold cycles, and in northern states, freeze and thaw cycles. If there is water in the compartment with the foam, the freeze/thaw cycles are even worse. Plus that the foam gets exposed to bilge water which can have gasoline, oils, cleaners, beer and who knows what else in it, especially salt water. And most people are not as careful about keeping their boats dry on the trailer as you are. They let them fill with water, snow, freeze solid, and collect leaves and other debris. In the south they sit out in the hot sun and the temperature in the boat soars to well over 100 degrees.

Aside from all that there is one more problem and this may be the most significant one. In 1995 The EPA changed the rules for foam manufacture. Two part foam shot through a gun uses a blowing agent, something that forces it out and helps it to foam. Prior to 1995 these were all HCFC's just like in aerosol cans. After much lobbying by yours truly, we, the Coast Guard, got the EPA to back off and allow the foam makers to still use HCFCs for flotation foam. But since this is a spit in the corner of the foam market the foam makers went ahead and converted to the new non-hcfc blowing agents anyway. The commonest one is just plain old water. However, this changed the way the chemical reaction worked, and that is when the trouble started.

As I said before, this is not an issue with block foam because the manufacturers make this stuff in big machines in temperature and humidty controlled plants. So, our research project is trying to determine which factor it is that is result in the failures. But if boat builders would simply use block foam, the problem would go away.

 

Good points, Peter. I'll make sure to track down the good stuff for my next project..... looking forward to the results of your research

 

well guys depending on the way the hull is constructed can contribute on the life expectancy of the foam under the floor most production fibreglass boats have poor laminations around the transom. the foam as much as they say it does it just simply dosnt like salt water this and because you have bad laminations at the transom water leaks in it may only be a trickle but it will do much damage to your foam before u get the tail tell signs of rotton transom.

as marshmat said they should have invented a colsed cell foam you think they should stop using **** like potassium cyanide to make it

 

Flotation Foam Approved For Usl Code And Abp Use In Australia

Available in Australia are three USL approved sheet foams.

See Links to National Martine Safety Committee web site below.

Recent rulings have stopped the use of pour foams in all Survey Vessels in Australia.

As part of our Alloy Kit Boat operation we now supply the foam as part of the base kit as STD.

SPECMAR AUS www.specmar.com.au




Thermotec Australia Pty Ltd
http://www.nmsc.gov.au/marine_regis...w_all_records=81&MID=95&COMID=16&CID=0&ID=193

Thermoplastic Foam Industries P/L
Microlen Marine Buoyancy Foam
http://www.nmsc.gov.au/marine_regis...w_all_records=81&MID=95&COMID=16&CID=0&ID=157


FOAM DESIGN
Boat Buoyancy Foam

http://www.nmsc.gov.au/marine_regis...w_all_records=81&MID=95&COMID=16&CID=0&ID=258

 

I have used these for many years and have over 30 years under a dock I built. Never absorb water, compatable with epoxy almost indestructable. I can buy them in all sizes as my vendor will cut it out for me
MUST BE PROTECTED FROM THE SUN....................................................
http://www.dockbuilders.com/styrofoambillets.htm

 

Hull Flotation Foam Question Update USL ABP Requirements

Hi Rasorinc,

I have viewed the material you mentioned in the past, We I have been trying to source a Value for Money Flotation material for the last few years.

The attached pdf is a short extract from the USL Guidelines for the testing of compliant Flotation material.

Would be nice if you could contact your supplier and have them do some testing I am sure we all would like access to high quality Flotation materials globally.

Cheers Rodney Dredge

 

Im in the process of removing the gas tank and replacing the stringer's and floor for this reason on a Century .

 

Stryofoam will not absorb water I've tested it for over 30 years. HOWEVER, IT MUST BE PROTECTED FROM THE SUN--SEE MY POST ABOVE. i USE IT UNDER THE SOLE AND IN THE SIDES BEHIND THIN PLYWOOD On the soles I glue down round wood rods to allow drainage under it to the transom drains.
Supports 55 lbs, per cubic foot.

 

what about the product they use to make these?

Made of polyethylene

Kids can play with those for months, years and it doesn't soak water. Yet it floats.

 

pool noodles have been used for flotation in boats. In fact I know of one mass volume manufacturer who used them in a recall to add flotation to their boats. They work fine if placed in the right places on th boat.