Replies to This Discussion

Permalink Reply by Matt Pope on July 28, 2023 at 12:28am

My interpretation of CS #602 on page 38 (Scratches, Cracked or Damaged Parts) is that if the depth (d') of the nick (or hole in this case) into the edge of the part is less than three times the thickness (t) of the metal then yes, you can round it out, making the length of the round-out at least four times as long as its depth, but if the damage encroaches a distance that is more than three times the thickness of the metal then you need to replace those parts (or you might be able to add an angle doubler to strengthen that area - see CS #605 on page 41).

For example, if the L-angle is made from 0.060" aluminum then you can still use the parts if the nick/divot/hole is less than 0.180" deep, measuring in to the deepest part of the damage from where the edge of the part should be. You just have to be careful not to make the round-outs deeper than three times the thickness when you file them out.

I can't tell from the picture if any of the depths are more than three times the thickness of the metal - it doesn't look like it, but that could be a matter of perspective.

If these parts are just brackets for holding something light and non-critical then I'd probably use them either way, but if they're parts that your life depends on (e.g. longerons) then I'd definitely follow the rule.

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Permalink Reply by Mark McNicol on July 28, 2023 at 6:01am

Hi Matt,

Thanks for your reply and answer. That definitely helps me clarify things. Much appreciated. 

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Permalink Reply by Matt Pope on July 28, 2023 at 11:51am

You're welcome!

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Permalink Reply by Jon LaValley on August 1, 2023 at 8:38am

Hi Mark,

I have only completed the tail section of my SD kit so far (wings coming this week!), but I found these notches are deliberate from the factory. The ones I have seen are included in the 3D models, and I use them to verify alignment, but may be worth double checking depending on what you are working on.

Personally, I do round out the edges slightly to add a radius just to prevent a stress riser, but I do doubt it's required.

-Jon

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Permalink Reply by Mark McNicol on August 1, 2023 at 3:52pm

Awesome Jon.
This is all new to me so I want to be sure. Those notches just don’t seem right to me. Additionally, written on one of them says… “needs to be rounded out” which it wasn’t prior to shipping. Hoping to hear from Roger or someone at Zenith to confirm. If I hear anything worth passing on to you, I will.

Thanks for the reply.

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