·:[ Darryl's Coot Building Journal ]:·
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The vertical fin ribs require three sizes of lightening holes. And the holes must be flanged. I built these three flanging dies out of 2024-T3 aluminum bar stock.

A bolt goes through the center hole and a nut is tightened to crush the halfs together.

I have an el cheep-o sheet metal brake designed for doing duct work. It doesn’t allow for an adequate bend radius for doing aluminum in aircraft. I modified it a bit so that I can move the clamp back and put in a radius die. Several problems remain; like this brake, mine has tension adjusters. Unfortunately, the surfaces are warped in the wrong direction—the tension adjustment makes the warp worse! (Clearly, I need to pre-stress the metal in the opposite direction, but that is a pain). The other two problems are (1) it is not a finger brake, and (2) it is only 48″ wide.

What Coot builders need is a brake that allows bends from ~2″ wide to 62″ wide for the vertical fin spars. But, with a few exceptions, the sheet aluminum parts are pretty thin. For instance, most of the vertical fin parts require 0.02″ 2024 T3 aluminum. Ideally, we would all own light duty, extraordinarily wide finger brakes (or 2 brakes: an extra wide brake and a smaller finger brake), that allow changes in the bend radius. Good luck with that one–you are talking $1000 worth of equipment.

Commercial brakes tend to be way, way too heavy duty (and expensive) for Coot builders. So, here is my proposed solution: a ~$25 brake made of two 4×4s and 2×4s. Two 72″ 4×4s are connected together with 2 heavy duty hinges. I routed out the end of the 4×4s to the depth of the hinges:

I turned some scrap 1.06 OD pipe down to 1.0″ on the lathe just because I had a 1″ forstner drill bit for putting handle holes in the moving surface. The final surfaces were hand-shaved with a draw knife to remove slight height differences along the length of the 4×4s.

The whole thing is fastened to a bench using angle brackets. A 2×4 or 4×4 acts as the top surface, and is plained to a greater than 90 degree angle in a jointer, and hand-shaped for the proper bend radius. The tricky part is to clamp a 62″ wide piece of 2×4 to keep the bend radius uniform along its entire length. The solution is pretty simple, though. I have two “jobber” work benchs in which I can drill holes. (They are made out of retired concrete forms that were later turned into a 2′ high drum stage by adding 4×4 legs. Eventually, they were retired and donated to me. I stacked ‘em two high and bolted them together). A few pieces of all-thread and scrap wood makes clamping easy and flexible.

Here is a test run of the brake. I used some scrap 0.062″ 2024-t3 and cut a trapezoidal-shapped “rib” (i.e. wider on one end than the other, as many tail pieces are), drilled some corner holes and cut out the corners:

Now it is clamped in place:

Here is the result of the first bend:

And the second bend is in process:

Here is how the end pieces are done. First clamp for a 90 degree bend:

…bend to 90 degrees, and then add a wedge to exceed 90 degrees:

And here is the finished piece:

Not bad! This brake should allow me to make light aluminum parts for the tail and other assemblies. It’ll not be able to bent parts for the engine pylon, which uses 0.125″ 2024 T3. That is probably a job for a real brake.

Update: Oops…after writing this, I realized that the main spar for the vertical fin is actually 0.04″ 2024 T3—thicker than the test piece. I guess I’ll be testing the capacity of the brake with an expensive sheet of long and thick aluminum soon….

Today was a clean-up and organization day. In preparation for building a tail jig in the basement shop, I sealed up and placed the two wingtank outside. If anyone is interested in wing tanks, they are free to the first person to haul them away.

These tanks were pulled from a set of wings that flew. The tanks appear to be in very good shape.

I spent the day with Russ Milham dragging his station wagon and a trailer down to Fran Neeley’s house in Cathlamet, WA, and coming home with many Coot parts and Coot-building molds. Fran, who I believe has owned a number of completed Coots has decided to get out of the Coot-building business.

The short wooden hull can be seen loaded on the trailer here.

Kathy and I did more cleaning of the garage, including installing new shelving. This will eventually contribute to my ability to work in the garage.

I bought some lumber to construct a tail boom stand (for constructing the tail feathers).

This evening, I did an assessment of some of the systems that need to be installed.

I inspected my Franklin 165 engine. It seems I have all of the accessories (starter, generator, magnetos, and carburator). I have an oil pump, but I am not sure it is correct for the engine. I may not have a voltage regulator for the generator.

I must look into lightweight accessories for the engine.

I have a crude carb heat box that might well be salvagable.

I do not have any exhaust system. Clearly I will have to build something.

I appear to have all necessary parts for the landing gears and legs, including the Earhart brakes and calipers.

Finally, I was interested in what goes into designing and building baffles. I read some chapters in Tony Bingelis on Engines.

I spent about 8 hours today cleaning the two garage/workshop spaces in which the Coot resides. The first shop is the upstairs garage. I share that two-car space with Kathy, who wants about one-half of the space for her car, garden tools, gardening implements, etc. Fair enough. The Coot hull has been buried in fiberglass for an attic insulation project. Furthermore, a couple of years of neglect have left everything in disarray. I made much organizing things today, including storing many hull and canopy pieces in the rafters of the garage..

The second workspace is the downstairs garage. During September of 2001, I constructed a 120 square foot “tool shed” that abuts the open garage door to, in effect, form an extension to the existing workshop space. This space is heated and includes a pretty nice wood-working shop and a nice amateur metal working shop. Right now, I have two sets of wings stored in this shop. Today I focused on organizing a very messy shop. Maybe tomorrow I will break-down the second wing.

There is some water damage from a leaky roof in the “tool shed.” I need to re-roof the relatively flat roof to make it water-tight. Then, I will replace the insulation and dry-wall on the ceiling.

On 2 October 1999, I called Richard Steeves and ordered a set of plans to build a Coot A amphibian. Since then I have put about 360 hours into the planning and construction of my Coot. Alas, my last log entry was in July 2002. My profession as a faculty member at the University of Washington required that I moth ball the project for several years.

Now, in August of 2005, I have decided to de-moth ball my project and resume my Coot building activities. This Blog will act as something of a public journal of my building activities. I have no idea why I am making this blog public, except that I hope it will lead to some discussion with other homebuilders. Additionally, a stale blog is a bad thing—I will be under some pressure to keep writing, which means that I must keep building, as well.

For anyone out there reading this blog, feel free to comment.