Grumman Canoes

I’ve got an old Grumman canoe; 15’ long, pretty wide, very flat bottom, and it has what looks to be like Bulkheads at both the bow and stern. They are attached to the hull with evenly spaced pair sets of Phillips head screws. Is there a reason for these to be there?

They don’t seem to keep out and water as there is almost a 1/8” space between them and the hull (except where attached with screws), they take up space, and really large colonies of ants seem to enjoy taken up residence in them.

As far as I can tell, as long as I put back the screws so the holes don’t leak it should be fine. However, I am not a canoe designer and I was wondering if anyone out there knows more about this or has experience with doing this and could offer their advice on the matter.


Try contacting…
Marathon Boat Works. They are a small town manufacturer that kept the old Gruman Canoe factory alive in Marathon, NY.

Best of luck,


Usually there is foam floatation in
those bulkheads. If none is floating out when you wash it, then it may be tight and good. Sunlight destroys the old styrofoam in those canoes, maybe gasoline too. My philosophy about old aluminum canoes and the bulkheads is to leave them alone if the canoe floats high in the water and doesn’t appear to plough. Other than to check the possible floatation, why take them apart? Do they bother you? If its curiosity, do it, but be prepared to add new floatation.

Two things to do

– Last Updated: Sep-24-06 3:05 AM EST –

First, kill off those ants. If they are carpenter ants, they are tunneling in the styrofoam. If they are little brown ants, they are probably just living in the dirt that has accumulated between the aluminum and the styrofoam, but I wouldn't take chances that they might not be tunneling. Spray some insecticide along that gap you speak of, and that will gradually finish them off, since all the workers that go out to gather food will either get sick or die. There's no need to spray anything back in those tight spaces.

Yes there IS styrofoam in there, and that's why that gap is so big. The joint need not be watertight as these are not air tanks (as I think Mike pointed out).

As someone else pointed out, if no bits of styrofoam are coming out when you spray water in there, you should be fine. I had carpenter ants in the floatation of my fishing boat, and styrofoam "sawdust" was in abundance. If the floatation is shot, you can just buy a couple of 4x8 sheets (maybe three or four) of styrofoam, the thicker the better, and cut several pieces to fit in that space. Cut them so they stack horizontally, with each piece trimmed to exactly fit its location in the chamber. Once the chamber is packed full of stacked sheets, put the covers back on and the boat will be as good as new.

Oh yeah. Prop the boat up off the ground a little and that will discourage new ant colonies. It won't stop them from taking up residence there again though, so keep an eye on things, and wipe-out the ants next time before the colony gets big enough to do damage.

Gussets are reinforcement
for bow/stern stiffening- oilcanning prevention.

Paddled those babies several summers as a Boy Scout, noisy but less fragile than the wood and canvas antiques our Scout camp had- and a lot lighter, since the canvas jobs were water logged.

Suggest using nontoxic ant repellent after cleaning the space out.

If you are worried about floatation, try this: Glue large diameter pool noodles along the gunnels. They will act as sponsons, making it harder to roll over, and floatation in case you do swamp. Some models actually came from the factory that way.

Have fun, Kaps