Hi guys

Its been awhile in the making but I just made my first part for my CH-640 and welcome some critique

the part is the bottom of the rudder, its wavy and has a 1/4 inch bow

The relief hole has a cut in it where I over cut with the snips...

So...is this a practice part and I make a new one....or

put some crimps in it, file out the cut and move on

what would you do...do over or keeper?

youre not going to hurt my feelings...so tell me how you really feel

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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!

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.

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?

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.

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.


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. 

Make a new one. Nothing is to good for your plane.

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

The 640 is completely scratch buildable.

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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