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Too aggressive deburring HS-908 attach bracket

Michael Burbidge

Michael Burbidge

Well Known Member
Well in the first week or so of building I've certainly made my share of mistakes. I'm already on my second set of HS attach brackets.

It's become clear to me that I've been too aggressive in deburring some of the first parts that I've matched drilled. The one that I'm most concerned about is the HS-908 horizontal stabalizer attach bracket. Some of the holes have about a 1/32 " bevel on them from deburring. Should I be concerned? I could easily build two new brackets. But I've already matched drilled them to the spar/spar doubler assembly. Match drilling new brackets to the existing holes in the spar/spar doubler would be a little tricky.

I certainly don't want to have HS attach brackets that have compromised strength.
 
I've been playing with my deburring technique (and different tools) quite a bit lately, had a few turn out like yours and wanted to get my mistakes out of the way early. While it's a bit of a pain (literally), I find my best results from a 1/4" drill bit with some masking tape wrapped around the shank. I can spin this in my fingers easily with mild pressure, just enough until it no longer "catches" on any rough spots in the hole usually about 2-3 full turns. Examination with a 10-power jewelers loupe tells me that I've gotten rid of the burrs without countersinking more than a couple thousandths on the edge of the hole.
 
deburring

[email protected] said:
Well in the first week or so of building I've certainly made my share of mistakes. I'm already on my second set of HS attach brackets.

It's become clear to me that I've been too aggressive in deburring some of the first parts that I've matched drilled. The one that I'm most concerned about is the HS-908 horizontal stabalizer attach bracket. Some of the holes have about a 1/32 " bevel on them from deburring. Should I be concerned? I could easily build two new brackets. But I've already matched drilled them to the spar/spar doubler assembly. Match drilling new brackets to the existing holes in the spar/spar doubler would be a little tricky.

I certainly don't want to have HS attach brackets that have compromised strength.
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I'm no expert but I believe the deburring that you've done to your HS attach brackets will not compromise the strength of the brackets. I, too, built a second set of AB's. The angles on my first pair looked as though i was drunk when I cut them. Learned a lot with the first pair and the second pair came out great.

When in doubt - contact Van's Aircraft. I'd be willing to bet a quick phone call will get a "build on" response.
 
I can't see how a slight over-deburring could matter as far as your attach angles go. There are times where "double-countersink" rivets are used in the project. I'd ask Vans to make certain any time you feel uneasy about something. If you reorder some angle material, you might try getting a length twice as long as needed in case you mess up again - you want have to reorder yet again and wait for it.

The most useful deburring tools I have is the 4" Hex Deburring Tool from Cleaveland. Another builder told me about it a couple (three) years ago. It can be use by hand or in my battery-powered drill. It has only one blade, so removing too much material from the hole is not a problem. Also, you can use it in a drill to countersink rivet holes is tight places, or just when you are doing a few and don't want to set up the microstop countersink.

Oh, yeh, I built two sets of those HS brackets too. Had perfect ones made and drilled them with "my toes pointed inward" instead of outward. Made new ones and got them right the second time. :)

http://www.aclog.com/rv-9a/index.php?c=1#279

http://www.aclog.com/rv-9a/index.php?c=1#282

Good building!

Mike
 
I've been helping a friend on his -9 tail kit so I know how easy it is to screw up the attach angles. For some reason that part of the plans seemed really confusing the day we were working it. The friend (new builder), myself (a fairly new homebuilder) and a very experienced builder and tech counselor spent 20 minutes discussing and looking at plans before we reached a unanimous decision about which way is up, left etc. None of us are stupid but we were sure dense that day.

A little bit of overly enthusiastic deburring probably won't hurt anything. Given the overall thickness of the angle the extra material you have removed is very small. Rememeber there's nine #4 rivets holding each of those angles on, in shear. It would take a LOT of force to cause a failure. And even if the rivets are very poorly done I'll bet that it won't be the rivets that let go first. But, again, when in doubt call Van's (I have one of those calls to make today myself). They have a lot of patience for questions on the tail kit. By the time you are finishing the fuselage the answers sometimes have a hint of "don't you know that by now?" in them. :rolleyes:

I use a bent-screwdriver looking deburring tool w/ good results but I am very careful; light pressure and just a couple twists until it turns smoothly. The drill bit suggestion is a good one. It's hard to turn the bit with your fingers if you are applying very much pressure.
 
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