Tuesday, May 10, 2011

Tech Tip Tuesday

That's square 1 up there and we're back there again.

Last Thursday evening, my friend and I who are building SOF kayaks were steam bending some Mahogany for coamings and hatches on her kayak. Unfortunately, we were working with a variety of Mahogany (probably Phillippine...) that wasn't suitable for the task. The wood was selected because it was a) nearly free... and b) light weight.

The wood was well cut in terms of grain direction, the wood was wetted down before we steamed it and the wood was heated to an appropriate temperature for a good length of time. A piece of cherry that was put in the steam box to act as a spacer bent like a pretzel.

We knew we had a grain flaw near one end of the strips that would break and wasn't going to be an issue, so we started the bend at the opposite end of the strips.


Whoops. Let's try another one.


Hmm. Maybe a third?


Ok. We've got kindling, not steam bending strips.

We did manage to steam bend some strips of "true" Mahogany for coamings on one of my student's canoes with no issues. With this information in hand, the only choice we had was to simply go back to square one and start over. So, my friend went and bought a piece of African Mahogany to use for the next strips we'll steam bend. The irony of the whole thing was that the piece of stock probably cost nearly a third of the cost of the rest of the kayak to date!

As I've said before, and I'll say again, determination is necessary to built a boat.


Anonymous said...

I went through a bit of "mahogany" bending one time trying to get outwales for an AA Grade OT with high ends. "Philipine", likely Meranti: forgetaboutit. African: Maybe on a good day with a project not needing much of a bend. Honduran: Light years better than the rest of the "mahoganies", especially with a backer strip and some care.


Canoez said...

Yeah, when I took Jerry Stelmok's class, we bent some pretty thick pieces of Mahogany that we'd ripped and pre-rabbetted to sit over the planking. I don't know what species they had in the stock rack at WoodenBoat, but it was probably a South/Central American or African variety.

We tied a rope to them and threw them in the pond overnight to soak. We then steamed the ends for nearly an hour before bending them over forms with a pre-formed backer for support. The backer was a metal strap with side supports to hold the gunwales rabbet outwards. Bend nicely, really.

Our stock was just, uh, junk in this case.

Canoez said...
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