Mad River Slipper flotation chamber

I recently bought a 1984 MR Kevlar Slipper knowing full well that there was inwale dry rot. About 6 to 8 inches on each side on both ends. Outwale is good.

I removed the gunwale and found the possible problem. The flotation chamber was filled with “yellow foam”. It seems that the orginal chamber was not a complete composite chamber and the top of the chamber was the inwale and deck plate???

Has anyone else found this situation and if so what was your remedy please.



That sounds like the way it was made
The MRs had open-topped end chambers with a yellow foam inside.

You don’t necessarily have to replace the inwales if the rot is just at the ends, especially if you’re not too concerned about looks. Or if you are, you could have Marc Ornenstein make you some carbon covers.

Pictures would help.

Mad River Slipper flotaton chamber
Ok thanks Clarion, I won’t worry about closing the chamber.

For the dry rot I am thinking about CPES, Git-Rot or similiar product with Min Wax wood hardner. The wood is all there but spongy. Any thoughts or suggestions about those products?




– Last Updated: May-27-11 12:53 PM EST –

I bought a Malecite some years ago that had rot on the inwales at the end. Sounds a lot like yours.

I took the gunnels off and then cut all the rot out of the inside surface of the inwales. Then I carved new wood to to replace the wood that was rotted where the screws go. Otherwise, the screws holding the inwale and outwale together would have nothing to grab hold of.

Then I put it back together and filled in the formerly rotted areas on the outside with Elmers Wood Epoxy.

This has worked great and lasted for about 8 years without issue. I store it indoors though.

Definitely use the CPES
That product has worked wonders and now is standard procedure for all my boat wood work; rails,thwarts, deck, gunwales and the like. Light years better than the Minwax hardener. The rot and spongy problem will be solved, however you will still need to do the repair to the inwale. You can also finish over the stuff if you desire a nicer look. I found that Jamestown Distributors typically has the best price on the CPES.

Good luck.

Yup. I saw a Slipper about a year
ago on the floor at Moor&Mountain in the midst of a re-rail that was constructed exactly as you describe.

Are you going to replace the foam? Won’t replacing/rehabing the existing structure pretty much garantee another premature failure?

Openboater should pipe in on this one.

Slipper dry rot
Ok thanks CPES it will probably be.

Probably wouldn’t hurt to close the floatation chamber but the problem seemed to be that with the solid inwale and deck there was no where for the water to get out if stored correctly upside down. I was thinking of putting curved 1/2 moon holes (Bell Style)(RIP) in the deck plate to make sure the water was not trapped and the wood had air to dry our.

Thanks for the info.


My '73 MR Compatriot was similar
except that there was a gap between the exposed foam at the top of the chamber, and the FG deck plate. The boat has spruce gunwales. No rot under the deck plates, but there was dry rot in other areas.

West’s product for rotted wood may deserve a look as an alternative to CPES.

Rail Rot in Stems
Mad River was the best designed/laminated/trimmed boat available in the 70’s and 80’s but it Achilles Heel was the end decks and the open foam floats.

Foam floats are better than air, would that the USCG would require same, but as they don’t, and air is lighter, everyone uses air tanks to present a lighter hull. Back in the day, Mad River glassed in the enclosures and dumped in a two part foam, the open top allowing for the dump in and relieving pressure if the mix was a little over large. It also allowed H2O into the tanks.

Mar River Canoe out with wood rails the same year OT discontinued same and Mad River’s decks were beautiful, so a marketing miracle was occasioned, but with a problem.

Mostly we store and transport canoes upside down. The shear’s curve directs any water including condensation to run to the stems where it drips on the deck’s underside. The open tanks repeated the favor, so an area where we tend not to Watco properly gets regular baths. Eventually rot sets in in the joints between deck a d rails.

At Bell we scuppered our decks to imptove drainage and used closed air tsnks: somewhat better, but those stem seams are still where rot occurs.

At Placid we put a drain at the very end and used an inert, Dymondwood, deck. Better yet, but those hulls have only been out for a decade. Even on a Pb the hull shpould be turned over and the joints between deck/ rails etc saturated with something penetrating and water proof annually.