Sunday, June 7, 2009

Thieves In The Night

I did something dumb the other night and paid for it. I left my camera in my truck overnight and it was stolen. A Pentax DSLR body, 3 lenses, half a dozen filters, and several memory cards tragically full of pictures from the last several months. The camera can be replaced, but unfortunately the pictures are gone.

In other news, I am slowly moving towards shoeing the dory with 3/4" plascore. This will (I hope) give me a worry free bottom that will withstand the occasional rock hit without requiring an immediate repair.

When I built my boat, I didn't know any better and used 3/8" Okoume for the bottom. This would be fine if I was the type of person that only floated calm water or just didn't hit rocks. But I am neither of these and my boat has taken some hits requiring on-stream repairs. Not to keep the boat from sinking, but to prevent water penetration into the wood. Knowing what I know now, I would have used 1/2" fir or another longer grained wood rather than Okoume, or more likely I would have used plascore. It's light, and it's impervious to water damage. So even if you put a gash all the way through the bottom (unlikely) you can just put some gorilla tape over it and call it good until you get home, then take the time to make a permanent repair, instead of wasting time with rough repairs on the river which only have to been removed and replaced once you get back home.

This raises one of the issues I have with commercially built dories and drift boats. Everybody wants to be able to say they build an "indestructable" boat but we've all seen that no matter what material or process you use to build a boat, it is no match for the power of the river should the river decide to show you. I am much more interested in having a boat that is reasonably impervious to the occasionally rock hit, while being as easy as possible to fix in the event of something more significant. Which is why I like plywood, plascore, fiberglass and epoxy. And when the most suitable building materials are also the most attractive, why would you want anything else?

So Larry helped me join a couple pieces of 3/4" plascore to get the length I need, now I just need to order some biaxial glass and I will be ready to do the layup.

I thought about vacuum bags and other elaborate systems, but decided to go the simpler route, relying on the chemical bonding properties of the epoxy to do the work for me. Once epoxy cures fully, new epoxy added will not chemically bond to the old epoxy, making it necessary to scarify the surface to allow a physical bond. So for the new shoe, after the first layer of the layup, everything else will be done in one big push in order to chemically bond the subsequent layers.

I have sanded the bottom of the boat with 80 & 120 grit. Next I'll lay down a layer of biaxial glass fabric using a slow cure epoxy mix, allow it to begin to kick, then lay down the plascore sheet and evenly weight the sheet down with sandbags, bags of pottting soil, etc. (which I'm hoping will more evenly distribute the pressure than hard sided weights) and allow to set up for 24 hrs. Then pack the open cell edges of the plascore with thickened epoxy, and finish with another layer or 2 of biaxial glass over the top, overlapping several layers of biaxial tape at the chine.

1 comment:

kneu2@mac.com said...

Hey, This Plascore stuff is pretty interesting. What do think about a doing an entire boat out of this stuff? Which honeycomb did you decide to use?

This coming fall I'll be building the hull of a whitewater dory...very excited. Intended use is in the Grand Canyon. I've been getting ideas together for a couple years. Just wondering if you have some suggestions for me. Maybe something you'd like to modify on your next boat..ideas on hatch design...

Thanks for your spectacular blog! I'm checking it all out now :)
Kelly Neu