Which Expanding Foam?

[18rabbit]

I need to replace foam that was removed when the fuel tank was replaced. The foam filled the void in the keel (under the fuel tank) up to a pass-thru hole in a bulkhead. Any water that makes its way under the fuel tank would flow over this foam and into the machine room where the bilge pump is.<br /><br />What foam do I need? Closed-cell polyurethane? Density? After foaming-in the keel, should I glass over it? Pros/cons of this idea? Thanks!!! - joe

 

[crab bait]

Re: Which Expanding Foam?

can't really follow your problem ..but yes a close-cell poly foam if you need alot..<br /><br />any boat center carries a two part mix.. just make sure it's mixed exactly,, an i mean EXACTLY.. if not ,,, you just made a big sponge... <br /><br />if you only need alittle ... as say aerosol cans,,, get the latex kind... it's a whole lot better...<br /><br />as far as 'glassin' it in... why..?? i see no need...<br /><br />as far as 'foam in the tank'... that's the worse thing you can do... the tank must have air flow around all three sides.. an underneath if you can swing it.. if not,,, it'll be a big 'ole 'condensation farm'...<br /><br />as far as 'if any water rises over ' an then goes to the bilge.... i'd think long an hard to have any water freely going/running to the bilge...<br /><br />by-the-way... WELCOME... COME BACK OFTEN..

 

[JasonJ]

Re: Which Expanding Foam?

If you want to foam under the tank but also want water to be able to drain from the forward bilge, you can take a piece of PVC pipe, cut it lengthwise, and epoxy it to the bottom to form a drain. You can then foam the void under the tank. This will allow the water to flow from the bilge area in front of the tank. Is the tank aluminum or polythylene? Aluminum should not be completely foamed around, it develops condensation issues. I think you can foam a polythylene tank in, but I still wouldn't allow it to be completely foamed. Air circulation around the tank is a good thing.<br /><br />You do not have to glass over foam, but if you use a good 2 part foam you can coat the exposed surfaces of the foam with resin and it will be alright. Other foams can degrade rapidly if resin is applied, so be carefull. 2 lb density will get the job done, but could possibly absorb water after ahwile, but we are talkin' years of continued exposure. The higher density foams are more resistant to water absorbtion, mainly due to the fact that the higher the density, the smaller each cell is.

 

[18rabbit]

Re: Which Expanding Foam?

Under the fuel tank compartment is the keel. Inside the keel, the pass-thru to the bilge is about 6-inches up the bulkhead. Originally, there was 6-inches of foam in the bottom of the keel so any water that got into there would flow right into the bilge. The aluminum fuel tank sits 10 or 12-inch above this. It was originally foamed in – mil spec.<br /><br />I have read 2-lb foam, and I have read 3 ½-lb foam is recommended. I have not found a comprehensive web site that explains the different foams and their pros/cons. I have read everything I could find on this website/forum. Great stuff!<br /><br />FWIW: foaming in a fuel tank is useful where a vessel may experience a roll over.<br /><br />I have pix but I do not know how to post them in the message. –joe

 

[CCrew]

Re: Which Expanding Foam?

Personally, I'd stay away from 2lb foam. It's designed for flotation. I'd go with something heavier, more toward a 4 or 8lb structural foam. <br /><br /> US Composites would be a good place to get some more info..

 

[crab bait]

Re: Which Expanding Foam?

thats the beauty of ownin' your own boat.. you can do what ya want...<br /><br />but don't foam in a fuel tank ,, epsec. a alum. tank... <br /><br />as far as 'vessel roll over',,, an upside down tank would be the last thing to worry about in that event...!!<br /><br />use good 'cargo' nylon straps to keep i there..<br /><br />chisle out afew 2x4x18 inch slots in the foam... epoxy in some 2x4x18 pt wood.. use for/to anchor down the nylon straps..

 

[18rabbit]

Re: Which Expanding Foam?

From reading the descriptions of the foams at uscomposites.com, I think the tank was foamed in with either the 8-lb or 16-lb stuff. You could walk on it without give, a hammer would dent it, but that’s all. Saws-all was used to cut it out. I will fill the void in the keel with the 8-lb foam...no glassing. Thanks to everyone for the help!!! Now on to electrical ...