Replies to This Discussion

Permalink Reply by Aaron May on June 12, 2018 at 8:26pm

Crimp it, file out the hole and keep on building. The more you do, the more you’ll get the hang of it. Congrats on getting started!

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Permalink Reply by Dave Alldredge on June 12, 2018 at 9:20pm

I would remake this piece. you will get better with practice and in time you will decide for yourself that you can do it better, This piece carries all of the loads between the rudder and the control horn. Pick a different piece and keep moving forward. you're doing a good job. Maybe even build a rudder kit if they are available for the 640.

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Permalink Reply by Michael T. on June 12, 2018 at 10:24pm

This part is about 3 feet long... should it come out of the form block flat?..so maybe my technique is wrong in the flange hammering process?... how many passes do you guys usually make with the mallet?

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Permalink Reply by Bryan Ekholm on June 13, 2018 at 8:09am

Maybe the problem is with the form block. Make sure your radius isn't too tight and that it's nice and even also. Make several passes (at least three) as you bend the metal over and then don't be afraid to really go after it with a dead blow mallet with the blocks held tightly in your vice on your final pass. Also move the part in your vice as you make your way down the metal so that the part you are  mashing is held tightly is the vice jaws. That way the piece won't bow out as much. It should lay a bit flatter than that when your done on a straight piece. I would say try again with a new piece of metal. It's a learning process for sure. If you have access to a bending break for the straight parts that would help too.

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Permalink Reply by Dan Hill on June 13, 2018 at 8:45am

Here is a video of how I form ribs, This is a nose rib for a 701, but the process is the same for the rear ribs except the bigger ribs are easier. Maybe you will find something useful.

https://www.youtube.com/watch?v=ezO8oEfE944

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Permalink Reply by Robert Lemke on June 13, 2018 at 11:31am

The waviness isn't so bad... the crack coming from your relief hole needs to go... I would chock it up as a learning experience. Don't throw the whole thing away. Trim the sides off and use them as "L" angles. 

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Permalink Reply by Scott Raynal on June 16, 2018 at 11:15am

Yes congrats on getting the project going!   But I was not aware that they sold plans to scratch build a CH-640.

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Permalink Reply by Michael T. on June 16, 2018 at 11:55am

The 640 is completely scratch buildable.

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Permalink Reply by Brian Thomas on June 16, 2018 at 5:18pm

I would call this a do-over.

I have a collection of six (I think) copies of the upper tail rib for my Cruzer.  It took me that many tries to learn how to form the compound bend on the nose correctly, and learn how to avoid other mistakes.  Once I learned on that one part, though, I've been able to build similar parts without needing a do-over.  In fairness, though, I've had to rebuild other parts here and there.

Scratch-building is sort of a momentum thing.  I spent about two years learning, slowly gathering tools and materials, fabbing parts, and not feeling like I've made much progress.  Then BOOM - the last three months have been great.  I finally have something that looks like it belongs on an airplane.

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