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05-10-2016, 10:07 AM
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Join Date: Oct 2005
Location: South Hamilton, MA
Posts: 521
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Other hole
Hey Eric,
That other #19 hole looks a little irregular as well.
One other question, is the mottled appearance due to an application of primer? Is that bare aluminum showing through the primer?
__________________
Antony
RV-7A
Empenage complete, wings complete, tip-up canopy complete, starting wiring ...
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05-10-2016, 10:26 AM
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Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,189
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Why?
A previous posts suggest, I would fabricate a doubler and build on.
I would question why the dimple cracked though. There must be a reason and discovering it now, in a non critical area, would be better than later, in a more critical area. What tool did you use to make the dimple? Was is a C frame that you struck to form the dimple or was it a squeezer? Was the squeezer set properly? Was the piece flat with the dies?
Just thoughts...trying to analyze the issue to be certain it is not an execution issue will prevent additional incidents in the future...
Ask me how I know...I have a whole BOX full of messed up tubing flares. I finally figured out that it was improper technique that caused the flares to be unsat...
__________________
Bob
Aerospace Engineer '88
RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...
Dues+ Paid 2019,...Thanks DR+
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05-10-2016, 10:29 AM
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Join Date: Apr 2014
Location: Underwood, WA
Posts: 413
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Hi Antony,
You're right. It was. In fact, they all were. Next time, I will be using a reamer instead of a drill bit.
Fortunately, the other three dimpled just fine. I looked closely and no cracks. They will be backed up by the existing interior doubler and the new exterior doubler so all should be good.
I still have no idea why that one hole pretty much exploded. I struck the rivet set with some force so maybe that was the cause. I used a pneumatic squeezer on that last hole and it worked out just fine. The other two holes also dimpled just fine and I used the same amount of force behind the hammer.
Yes, the mottled appearance is Napa 7220 primer.
__________________
Eric Rushing
RV-10
90% done, 90% to go.
Looks like an airplane!
Molalla, OR
Last edited by ERushing : 05-10-2016 at 11:00 AM.
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05-10-2016, 10:43 AM
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Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,966
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That top hole in the photo looks like its not round also. You may want to get rid of that drill bit.
__________________
David C.
Howell, MI
RV-10: #41686 Under Construction
RV-9A: #90949 Under Construction
RV-10: #40637 Completed/Sold 2016
Cozy MKIV:#656 Completed/Sold 2007
"Donor Exempt" but donated through Dec. 2020
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05-10-2016, 10:59 AM
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Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,189
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Second that!
I would agree with that, try a new bit. I change mine out often and haven't had any dimples crack like that. Haven't used a reamer yet so can't speak about that.
__________________
Bob
Aerospace Engineer '88
RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...
Dues+ Paid 2019,...Thanks DR+
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05-11-2016, 10:14 AM
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Join Date: Feb 2015
Location: Oklahoma City
Posts: 913
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Eric- Sorry for the setback, hate when that happens but all part of the fun I suppose. On dimpling if I'm able to use the squeezer I always use it. In fact on the Gretz #8 holes on the skin was the first time to use the C-Frame to dimple anything other than a #30 or #40. I was a bit nervous about it and did a two tiny taps to get it to sit and then wacked it fairly square. Luckily it all worked out.
I use reamer bits quite a bit and love them. There seems to be less risk of enlarging a hole with them and will use them when I'm just final drilling vs match drilling.
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05-11-2016, 10:45 AM
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Join Date: Aug 2010
Location: Eugene OR
Posts: 20
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I have an extra pitot mast but I am not sure what brand it is. If you send me the dimensions I will check. If it will work you can have it for the postage.
Joe
Eugene OR
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05-11-2016, 11:21 AM
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Join Date: Apr 2014
Location: Underwood, WA
Posts: 413
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Hi Justin,
I'm almost done with the doubler just need to prime it now.
Unfortunately, this appears to be a case of human error and a lapse in judgement. I've heard it said that if you're trying something new, don't try it on your airplane first. I hadn't used the C-Frame dimpler other than in the EAA sheet metal class 18 months ago. Since I couldn't reach two holes with the squeezer and I didn't want to take the time to set up my dimpling setup and DRDT, I just pulled out the C-Frame. It worked just fine for the first two holes.
When it came to the third hole, I thought I had it positioned correctly. Lowered the female die over top of the hole, grabbed the hammer and gave it a whack. Sometime between inserting the female die into the C-Frame and bending to pick up the hammer, the material must have shifted. I punched a hole through the aluminum skin instead of dimpling the hole as intended. The pics below (upper left hole) spell it out pretty clearly! I've got the new doubler positioned under the skin to highlight the mistake.
To finish this, I'll squeeze the offending dimple flat, gently re-dimple for the appropriate hole and then move on to assembly. Note that the part on the left is the exterior doubler. The one on the right is the internal doubler that came with the Gretz Pitot mast.
Embarrassed but glad I know what I did wrong and that there was a reasonable fix.
__________________
Eric Rushing
RV-10
90% done, 90% to go.
Looks like an airplane!
Molalla, OR
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05-11-2016, 11:24 AM
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Join Date: Aug 2011
Location: Monterrey, Mexico
Posts: 121
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Quote:
Originally Posted by Low Pass
A little curious why the metal simply fell away.
Regardless, as other say, make a doubler plate - inside or out - and move on. It'll be stronger in the long run, which you want with a pitot mast.
If you're not sure, check this out for guidance.
https://www.faa.gov/regulations_poli...a/ama_Ch04.pdf
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this is gold
__________________
Miguel Vidal
EAA #1133587
RV-8 SB Wings in Monterrey, Mexico
N511MV Registered
MyKitLog
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05-21-2016, 03:39 PM
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Join Date: Aug 2015
Location: Hurricane Utah
Posts: 156
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wait and see...
With a stainless doubler already behind the skin I really question the need and value of the external doubler. The latter can be added anytime down the road, if ever needed. You could think about using #8 countersink SS washers as well to distribute the load from the screw, perhaps fill with some epoxy resin too. Since there is good access to this area down the road if needed, really the same as doing original installation, it makes this kind of wait, inspect, and see reasonable and safe. Like many have said I can only add one more vote, we all have those nights.....SB or FB...it happens.
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