Evolving Wooden Chainstay

[MrSteve]

Billy K's thread about testing the flex of his Quest frame is really interesting...
and he wants to see my wooden chainstay... so, Mr. K., this is the best I can do!

My bike has a lot of non-stock parts; I built two of the major pieces.
The seat was built first and that story is in another, older thread.

The chain stay I built was never documented, just mentioned.
I built it for better aerodynamics and, as it turned out, the high
bottom bracket was more comfortable for me and I made a lot more power
with my feet up above my hips.

The wood core is a chunk of left-over spruce that ties together the legs of the
chain stay.
It's a leftover from a kayak paddle I'd carved;
another length of that spruce made the spacer for my right pedal.

The legs are softwood, void-free plywood leftovers from my giant subwoofer
project.
I chose plywood because I can rapidly carve a pretty fair airfoil shape with
the plies guiding my progress.
I have a lot of practice, having carved all my paddles, kayaks and stuff, so,
no big deal.
No photos exist of the one-to-one mechanical drawing I used to assemble
the wood pieces, of the carving process or of much of anything useful to anyone else.
Sorry.

The epoxy resin was left over from a kayak project;
the fiberglass is from the same project.

The aluminum flashing was left over from some tree collars I'd made to
keep raccoons and squirrels out of the bird feeders.

 

[MrSteve]

Here is the best pic of the rough, tacked together and still square wooden chain stay.
It was spray-painted black to hide it's immense ugliness while I test-rode it.

The ends are aluminum plate epoxied to the wooden legs
and the hinge point on top, connecting the chain stay to the
bottom bracket uses the stock hardware and a length of copper pipe
epoxied to the wood.

It worked... and broke a few epoxied joints, which were massively reinforced.

 

[MrSteve]

This is what it looked like faired, glassed, faired, reinforced, glassed, faired
and faired and, finally, roughly finished and covered with enough primer
to protect the resin from the sun.

The trailing edge is squared off. Kamm is better when you have no
control over angle-of attack.
Airfoil is symmetrical.

This iteration was pretty stiff, much stiffer than it was in it's
blacked-out, rough proof-of-concept stage.

There was room for improvement though, so a few years later,
I added a cross-brace whittled out of a piece of douglass fir and,
since I could not afford carbon fiber, I laminated some aluminum
flashing to the legs.

Next photo....

 

[MrSteve]

Here's what it has looked like for a few years, while I
had fun hammering up hills, setting personal-best speed records
and just generally reveling in the pure fun of my own biking world.

This photo was snapped today.

The flashing-clad legs are the stiffest, strongest parts of the front-end.
I'm stripping the paint off, yet again, to prep this part for carbon fiber.

The trailing edge will be a little swoopier, so that I can get more material
around the points where the composite chainstay is attached to the aluminum
plates.

This should take me a year or so.

Yes, the aluminum will be isolated from contacting the carbon.

And, if you wish to duplicate anything you've seen on my bike,
remember that you do so at your own risk.
So there.