to me privately. The bottom of the mail has my questions to the
factory on flush riveting and dimpling techniques. The response
is very useful for folks considering flush riveting the leading
edge as well as dimpling and countersinking in general:
------
Hi Eric,
I will give you the way I see all this countersinking/dimpling confusion.
The Rebel series of aircraft were never intended to be flush riveted. For
some unknown reason customers started to ask whether they could do this to
their leading edges on the Rebel, so the Elite and SR were given thicker
leading edges, also helping with their Gross weight increase. .032 is JUST
thick enough to c/s if you are very careful, and have experience with a
microstop. If done properly, the holes will be fine.
Dimpling causes several problems. You are deforming the skin, and in the
certified world heated dimpling tools are used to help prevent cracking.
Also the hole has to end up enlarged...you are stretching it. So that's why
you should drill to final size after dimpling. In the small areas indicated
in our manuals, the swell of the avex rivet takes care of the enlarged hole.
Next, you have to dimple right through the underlying structures. Dimpling
and then c/s the underlying structures is not, to my mind acceptable...the
layers will just not lie down properly.
So, to sum up: c/s is preferable to dimpling on large structural areas,
unless you have access to a million bucks of heated dimpler.
C/sing MUST be done with the correct angle bit for the rivet head, and must
be done to the correct depth, and ensuring no chattering takes place.
Personally, I just cannot understand why anybody would want to do either on
our lovely, safe, slow flying series of STOL aircraft, except where we tell
you, for door fit, fairings etc.
I actually like the "built like a bridge" look of our aircraft with the dome
head rivets.
And ever tried drilling out a series of c/s rivets compared to dome? Just
compare the holes afterwards!
Regards,
Brian
Brian Godden
Murphy Aircraft Mfg. Ltd.
bgodden@murphyair.com
----- Original Message -----
From: "Eric Fogelin" <ericfo@whidbey.com>
To: <murtech@murphyair.com>
Sent: Wednesday, June 07, 2000 7:37 AM
Subject: Flush riveting
*-----------------------------------------------------------------------------------*I am at the point where I need to decide whether to flush rivet
the leading edge of my Elite wings. I ordered the flush rivet
option, but there were no instructions on how to proceed.
I have asked other builders of Super Rebels and Elites, most
aren't flush riveting, those that do use various techniques:
1) Some dimple skins, ribs and stringers
2) Some dimple skins, ribs and countersink stringers
3) When I was at the factory last year, it looked like the demo
SR leading edge skin was being entirely countersunk, no dimpling
What technique does the factory recommend?
I have a micro-stop countersink, and have experimented. Using
care, it seems that countersinking the skin and no dimpling
can be done...and this is very quick. But, won't this be a
weaker attachment than dimpling? Dimpling is a very slow
process with the dimple tool.
I understand that there will be little to no speed increase;
this is just for aesthetics.
Also, a question on dimpling. The manual always says to final
drill to #30 and then dimple (for areas that require dimpling).
Metal working references say to dimple first using an undersize
hole, then final drill. Should the manuals be changed or is it
okay to dimple after final drilling?
What did the factory do on the demo Elite and SR? What do you
recommend?
I'd like to post your response to the Rebel Builder's List. Lacking
current guidance, builders are having to solve this on their
own, some better than others.
Eric Fogelin
Elite #645
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*-----------------------------------------------------------------------------------*
-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------
