(Occasionally) Great Stuff – Cheating with expanding foam

10 Jan

One of the projects we got to while my family was down in New Orleans helping me out was installing a holding tank and second water tank. To make our lives a little easier we set the tanks in place with regular old hardware-store expanding foam. The water tank went into a mostly dead space behind where the engine will go, when we find one (Have a used 10-15hp marine diesel to sell?-Get in touch). We just hooked up the hoses, shoved it back into the stern until it kind of stuck and then sprayed some foam around to hold it in place. Should be fine for years, right?

Only kidding! If we left it like this the tank would break free the moment we filled it. Our next step will be building some plywood bracing and tabbing it in with heavy fiberglass cloth but the expanding foam helps both to hold it in place while we build the bracing and to help keep things from moving around if the bracing isn’t a perfect fit.

 Unfortunately, with the holding tank we really underestimated this “Great Stuff.” Being smaller, in a more compact space, and not likely to ever get used when the boat is bouncing around we decided to put the holding tank in with just the foam and no other bracing. For a little insurance factor we used lots of foam. LOTS of foam. When we came back the next day to check we saw this.


That’s a chunk of foam which for some crazy reason has climbed up the front of the tank, gone out and around the fill fitting and then pushed its way inside and started filling the tank! Even after cutting as much from the front as we could this left us with a piece inside the tank:

It took some serious fiddling and a touch of bloodshed but eventually we got it all out with a vacuum and a kitchen knife.

That pile is just the stuff that was inside the tank. 
Also note the two PVC limber pipes which allow bilge water to flow under the foam.
I guess the lesson learned is to never underestimate “Great Stuff”? Or maybe don’t cut corners in the first place? I’m not really sure but I do know this stuff has been the butt of a longstanding joke at the bicycle shop where I work ever since we took in a bike that someone had actually tried to repair with it! And I found this thread talking about filling full-size cruising boats with enough expandable foam to make them ‘unsinkable.’ Anyone else have a ‘Great Stuff’ story to share?

This article was syndicated from Safe At Harbour But Meant For The Sea: DIY Sailing with Paul Calder


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