View Full Version : Sacrificial bottoms

Tar Devil
02-01-2003, 03:09 PM
I've heard of this done several times, and I would line some input on how a sacrificial bottom on a ply boat should be applied without...

1) Compromising the integrity of the hull's epoxy/fiberglass encapsulation by screwing a sacrificial bottom to the structural bottom...
2) Entrapping moisture between the structural and sacrificial bottom, thus inviting rot.

Thanks for your input.



Pete Dorr
02-01-2003, 04:13 PM
Instead of a complete bottom how about a couple of wear strips in key places.

After sealing off the bottom with glass & epoxy. Epoxy a 3/4"x3" oak strip (on the flat side) onto the glass. When this wears down to 1/2" clean up the top edge with a plane or router and epoxy a 1/2" strip onto this. Repeat this adding of 1/2" as needed keeping the total height to about 3/4" to 1".

I'm going to do something similar to my fiberglass dingey as I'm trashing it.

[ 02-01-2003, 04:14 PM: Message edited by: Pete Dorr ]

Tar Devil
02-01-2003, 04:23 PM
Ordinarily that would work fine, Pete, but this particular boat was designed to launch in the surf, spun around in a film of water, then rowed out through the surf. A strip such as you suggested would dig into the sand and prevent the boat from sliding around on the sand as it should.

Thanks for the suggestion, though.



Bill Perkins
02-01-2003, 06:00 PM
Maybe a layer of xynole cloth could be the sacrificial bottom . It's said to be very abrasion resistant , and so could protect the glass.That's what I'm going to try .

[ 02-01-2003, 06:00 PM: Message edited by: Bill Perkins ]

02-01-2003, 07:50 PM
I believe that the article in Woodenboat about the oregon dories talked about how Learned had the the bottoms coated with a pretty thick ;ayer of gel coat--how to get that to work with epoxy, I don't know- maybe use a thick layer of epoxy and carbon as the wear layer?

02-01-2003, 07:52 PM
I'm inclined to agree (though I love ply) with the fabric covering, rather then the ply. The ply will want fasteners if there is any reasonable amount of twist in the bottom. I'd sure not want to rely on goo alone to hold it on, though it's been done and many swear by goo. The fabric will be lighter and stronger then ply (for abrasion resistance). Don't use just 'glass cloth, use a product like Xynole as it's much better at this job then 'glass.

[ 02-01-2003, 07:53 PM: Message edited by: SailBoatDude ]