|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

11-21-2013, 11:04 PM
|
 |
|
|
Join Date: Jul 2013
Location: Phoenix
Posts: 75
|
|
Fatherson... I have no idea what made you think that I was questioning strength.
The question is: Do you use the same dimple die for the top and bottom skin?
If yes... where did you learn that was okay? I'm curious.
From what I have researched, using the same dimple die (100º be it spring back or normal) for both sheets being riveted is wrong. I'm looking for evidence to the contrary.
Last edited by Roarks : 11-21-2013 at 11:17 PM.
|

11-21-2013, 11:45 PM
|
|
|
|
Join Date: Oct 2009
Location: Albuquerque, NM
Posts: 427
|
|
Quote:
Originally Posted by Roarks
Fatherson... I have no idea what made you think that I was questioning strength.
|
Well, you're right. That's why I asked you to clarify what you meant. I did make a subjective leap that you might be concerned about strength of the joint, even though you literally were only questioning if the two skins would nest properly.
In my understanding of my readings on the nesting issue, the concern is that if the two skins don't tightly nest, then that reduces the sheer strength of the dimple, and thus increases the sheer load on the rivet, with an overall reduction in the strength of that joint.
If you are not concerned about the relative strength of nested, dimpled skins, then what is your concern?
Quote:
The question is: Do you use the same dimple die for the top and bottom skin?
If yes... where did you learn that was okay? I'm curious.
From what I have researched, using the same dimple die (100º be it spring back or normal) for both sheets being riveted is wrong. I'm looking for evidence to the contrary.
|
It's not the springback portion of the dies that causes the skins to nest properly, but rather the relative sizes of the diameters of the male and female dies (as measured at the widest part of the impression, basically the "top" of the manufactured head of the rivet). See the NACA doc if my summary is unclear.
As for me, I use separately milled substructure dies for the bottom dimple, and standard milled dies for the top skin, but that's more because I like tools, like and trust Cleaveland's dies, and enjoy being an anal-retentive engineer, and not because I believe there will be any significant difference in the strengths of my joints.
Plenty of perfectly sound RVs are flying that were dimpled with one set of dies (well, you know what I mean: one set for each rivet shank diameter).
Your mileage may vary (but I seriously doubt it'll be by any noticeable amount). The fun of experimental aviation is you can build to whatever standard you're most comfortable. The docs I've seen, the trust I have in Van and his company's engineers, and almost 9,000 flying examples are sufficient proof for me.
--
Stephen
__________________
Stephen & Tyson Humphrey
father-son team building new lives and an RV-9
VAF Donors: 2008 to 2014 * Friends of the RV-1
|

11-22-2013, 12:45 AM
|
|
|
|
Join Date: Dec 2010
Location: Alpharetta, GA
Posts: 88
|
|
This old WWII-era instructional video from Disney / Lockheed implies that it used to be accepted commercial practice that the top and bottom sheet dimples are formed with different tools. After discovering that, I decided to get a set of substructure dies from Cleaveland Tools.
- John
(Card Carrying Perfectionist)
|

11-22-2013, 02:04 AM
|
|
|
|
Join Date: Oct 2009
Location: Albuquerque, NM
Posts: 427
|
|
Quote:
Originally Posted by John R. Graham
|
Awesome. Thanks for finding that, John. I recall seeing the Disney video early-on in my "aluminum apprenticeship." Perhaps that's what led me to buy the Cleaveland substructure dies, like you did. (I don't recall why I did, exactly.)
It's interesting to note though that the Disney / Lockhead method of improving nesting requires a different angle for the substructure dies. As far as I can tell, all the Cleaveland dies are 100* (except the 120* pop-rivet ones, which aren't related to this discussion).
So Cleaveland seems to be using the narrower-female-die-diameter method (like the NACA doc recommends) and then a wider-substructure-die-diameter to improve nesting (same angle, deeper dimple), instead of the shallower-substructure-angle method (like the Lockhead doc recommends). Perhaps I'm wrong about that. Mike Lauritsen frequents this forum, so maybe he'll weigh in. Does any vendor make 110* dies?
So to Roark's question, is there a definitive standard somewhere that says one of these methods is actually "wrong", or is this just a matter of different-strokes-for-different-folks?
(Not that I believe either answer is likely to make much of a difference. Even the NACA doc admits the angle of the dimple changes once the rivet is driven, deforming the dimples somewhat as it clamps them together.)
--
Stephen
__________________
Stephen & Tyson Humphrey
father-son team building new lives and an RV-9
VAF Donors: 2008 to 2014 * Friends of the RV-1
Last edited by fatherson : 11-22-2013 at 02:21 AM.
Reason: Clarity
|

11-22-2013, 07:11 AM
|
 |
|
|
Join Date: Jul 2009
Location: England
Posts: 470
|
|
One thing I have noticed when using the "substructure" dimple die on the second hole - the hole dia is right at the top end of the hole tolerance. The hole is drilled with a #41 - any burrs are removed carefully.. before dimpling.... Just an observation..
__________________
Jan
Slooow RV6, no hole, builder in UK
Paid up for 2015 ...
|

11-22-2013, 07:59 AM
|
|
|
|
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
|
|
There should be no angle difference in properly formed skin & structure dimples; simple geometry. If the dimple isn't fully formed on one of the pieces, that's a different issue, & different dies won't help that.
The only issue is whether the inside surface of the skin actually touches the flange of the structure. IIRC, there are even a couple of places in Van's instructions where the top layer is fairly thick, where he says to remove extra material in the bottom countersunk layer to allow full nesting.
Perhaps it's time for the reminder that this isn't rocket surgery. :-)
Charlie
|

11-22-2013, 08:07 AM
|
|
|
|
Join Date: Dec 2010
Location: Alpharetta, GA
Posts: 88
|
|
Jan, by "second hole", do you just mean the hole in the bottom (inside) piece?
- John
|

11-22-2013, 08:39 AM
|
 |
|
|
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
|
|
Adding a bunch of complexity to the dimpling thought process does nothing for demystifying dimpling, but I guess there is also nothing wrong with it if someone wants to invest the extra effort and $. In my opinion in most instances it does nothing for strength or longevity, but if it makes you feel better... go for it.
RV's have now been built for decades using equal size dimple dies for all material layers (what to do when there is more than two???).
A little know fact... when Van built the first RV-3, he did all of the dimpling during the riveting process. One hole at a time, he first drove the rivet against a drilled and countersunk bucking bar to reform the material, and then shifted the bar to drive the rivet. Pretty primitive even he admits, and it didn't look nearly as good as what has now been done for many years, but it worked.
The bottom line is that technique in both forming the dimples, and doing the riveting is 99% of the equation regarding strength and how good it looks.
Vs whether you used different sized dimple dies on different layers. In fact I would bet that it is undetectable by eye or strength measurement, if the same level of workmanship was used on either process.
Learn (I mean really learn) how to properly form dimple countersinks (my guess is, to some degree, probably 50% of builders don't). Then use your best riveting techniques to get it assembled. You will be flying that much sooner and the finish can be as good as anyone else has done.
BTW Section 5 of the construction manual has been updated recently. One of the changes was adding more info regarding dimpling and evaluating the finish quality. It is currently published on the web site HERE
There has been a lot of other stuff added also (electrical noise troubleshooting guide, etc)... Take a look.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
|

11-22-2013, 10:55 AM
|
 |
|
|
Join Date: Jul 2009
Location: England
Posts: 470
|
|
Hi John R
Yes ..second hole, the hole below the top visible hole .... This was using the Cleveland 'sub structure' dies for the second hole ... another interesting bit of useless info ;-) .. I also have dies from Avery .. and I found a good 'nesting' of the two dimpled holes .. using the normal Cleveland dies for the first hole .. and dies from Avery for the second hole !! I guess that is why I am still building ... after lots and lots of years ...
rvbuilder2002 are spot on .... it all works .... and after all .. I am doing this because I enjoy it ... :-) ...
__________________
Jan
Slooow RV6, no hole, builder in UK
Paid up for 2015 ...
|

11-22-2013, 11:23 AM
|
 |
|
|
Join Date: Jun 2006
Location: Delaware, OH (KDLZ)
Posts: 4,196
|
|
Quote:
Originally Posted by rvbuilder2002
BTW Section 5 of the construction manual has been updated recently. One of the changes was adding more info regarding dimpling and evaluating the finish quality. It is currently published on the web site HERE
There has been a lot of other stuff added also (electrical noise troubleshooting guide, etc)... Take a look.
|
Scott,
You guys get my kudos on a much improved document. I wish I had this version seven years ago when I started.
bob
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 06:50 AM.
|