What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Question about cracks in #8 Dimples and LE pillowing

S

skyyking56

Well Known Member
Please help!!!!

I ran into a couple of cracked #8 dimples in my W-423 joint plate. (I was able to slightly enlarge the ID of the dimple to eliminate the crack). I did a search here and found all kinds of problems with that. The cure seems to be "go to a larger pilot hole".?????? My die fit into the #19 hole without any problem (was NOT tight)
Also in my search on this subject I found problems with pillowing of the LE fuel tank skin so that the LE skin and tank skin are not in surface alignment.
Here is my question: The instructions say to use a C-Frame tool to dimple these holes because "it looks nicer". Does using the squeezer or DRDT-2 causing this pillowing affect????? Is this what they are talking about "looks nicer" (no pillowing problem) ?????
Have any of you out there used a DRDT-2 or pneumatic squeezer and not had this pillowing problem?
Should I borrow a C-frame or buy one just to do these holes so I wont have pillowing in my skins? It seems like an uneccessary process to shim up the LE skin to align with the tank skin if you are following the direction from Vans.
I would appreciate any and many theories on these subjects...

Please help!!!!!!!!!!!!!!:confused:
Thanks again
Jim (7A wings)
 
skyyking56 said:
Please help!!!!

Also in my search on this subject I found problems with pillowing of the LE fuel tank skin so that the LE skin and tank skin are not in surface alignment.
Here is my question: The instructions say to use a C-Frame tool to dimple these holes because "it looks nicer". Does using the squeezer or DRDT-2 causing this pillowing affect????? Is this what they are talking about "looks nicer" (no pillowing problem) ?????
Click to expand...
no. i used a c-frame and have some.. some have shimmed it out. i dont want to dis assembled the completed wing to do it. already did that one time to arch the nutplates....wasted effort. the drdt will likely do it well, i dont think a squeezer will however.
 
If you don't have everything in proper alignment, meaning all the skins down tight when you drill the holes you will run the risk of pillowing. Also make sure that when you drill the holes that the drill bit is 90 degrees to the surface. If the holes don't line up perfectly it will cause the pillowing as the screws tighten up it will pull the skin one way or another.
 
Cracks in #8 seem common. Don't think there is much you can do about it. There is only so much technique you can use to dimple a hole so I don't think it has so much to do with technique as it does luck. I think if people who say they don't have cracks look hard enough, they might find a few.

Pillowing is also common. I did some with the Cframe and some with the DRDT2 and some with the squeezer. One all of them, some pillow some don't so here again it does not seem to have so much to do with the device you use.
 
skyyking56 said:
.....Also in my search on this subject I found problems with pillowing of the LE fuel tank skin so that the LE skin and tank skin are not in surface alignment.......
I would appreciate any and many theories on these subjects...

Please help!!!!!!!!!!!!!!:confused:
Thanks again
Jim (7A wings)
Click to expand...
Jim,

The pillowing problem is very common. I experienced it on both leading edge/fuel tank skins in the identical location. I have long held the personal *opinion* that the pillowing has more to do with too great a design screw spacing in the area aggravated by a significant curve and bend in the sheet metal forming the leading edge. The mismatch always results in the fuel tank skin being "pillowed" or slightly higher than the leading edge skin and not the other way around. To support my theory, I ask you to measure the rivet spacing on the leading edge skin adjacent the fuel tank skin and compare that value to the 2" screw spacing on the fuel tanks. As you will observe, there is a dramatic difference in fastener spacing. I believe the pillowing could be eliminated if the screw spacing were narrowed but with pre-punched skins that is not a realistic option. Nevertheless, here is a link with pics that describes a very easy fix for the mismatch.

http://www.vansairforce.com/community/showthread.php?p=114861&highlight=Pillowing#post114861
 
Last edited:
Curves and shims...

Jim P said:
Had the same thought on screw spacing. My solution was to double up the top screws, bottom are fine as is.

http://adap.com/rv7/images/PB030051.JPG
Click to expand...

Jim... neat picture, but you can still see some pillowing. Reducing the spacing just pulls down the high spot of the "pillow" and distributes it over a smaller lengths...

The real error is that the outer skin and it's associated plate nut strip is a shorter curve than the curve of the tank (perhaps due to the proseal in the tank rib/skin joint?).

Shims (between the rib and the plate nut strip) will lift the outer skin into the same curve as the tank.

Please note, I'm not knocking your fix... it is a vast improvement... just that shimming might be easier....:)

gil A
 
Rick and Jim--

Isn't there a difference in the thickness of the 2 skins to begin with as well (man my memory is getting short).

I had to shim.

Joe
 
Not really applicable

jferraro16 said:
Rick and Jim--

Isn't there a difference in the thickness of the 2 skins to begin with as well (man my memory is getting short).

I had to shim.

Joe
Click to expand...

Yes... but that should not be applicable to the shim discussion since you want both skins to sit as flat as possible on the nutplate strip.

An uniform 0.007 inch height difference would look OK visually (0.025 outer skin and 0.032 on the tank - for the RV-6s) if you could even see it...

gil A
 
Jim,

I reduced the pillowing affect almost to ZERO. I used a brown rolling tool and did all the rolling before I dimpled the holes. Did not do it on the first tank and I will take the other tank off and roll the edge and put it back on. Did not think it would make a difference but it does. The spacing is fine on the screws.
The only thing I did not roll on the tanks were the inboard edges.

Hope this helps and I think I have picks on my web site. (Somewhere)
 
Thanks

Thanks to all.
I really apprecaite the help.
It makes going into an unknown problem area easier.
Have a nice weekend all!!!
Jim (STILL on 7A wings)
 
Hey guys,

I have the same problem. I already tried shimming but there is still pillowing in a few spots. Anyone see any structural issues with just adding more #8 screw in the spaces? I would like to put in new #8 screw between each original screw on both top and bottom tank skin to keep it cosmetically looking good. Should I be worried about changing anything structural by doing this?

Dan
 
skyyking56 said:
Hmmmm...... I've never heard about any problems with cracked dimples:confused:
Click to expand...

Well here is Ken Scott's reply to my question about this on 8/6/07:

"This can happen on larger dimples and we've never seen it cause a
problem. Sometimes we'll drill out the finished hole a few
thousandths after dimpling, if the cracks are very short."

So as of 8/6/07, they had definately heard about it and they had also experienced it themselves.


 
maybe I don't understand

I had similar pillowing on my fuel tank skins. My simple minded approach was to gently form (bend) the tank skins in until they lined up. looks okay and took ten minutes. Am I missing something?
 
Agreed

Bruce said:
Jim,

I reduced the pillowing affect almost to ZERO. I used a brown rolling tool and did all the rolling before I dimpled the holes. Did not do it on the first tank and I will take the other tank off and roll the edge and put it back on. Did not think it would make a difference but it does. The spacing is fine on the screws.
The only thing I did not roll on the tanks were the inboard edges.
Click to expand...

I did the exact same thing, but with the Cleaveland Vise Grip edge seaming tool and have zero pillowing. I dimpled my #8 holes after edge seaming with the squeezer. I've seen dimples from c-frame, DRDT2, and squeezer. The c-frame and squeezer seem to make crisper dimples and thus look nicer IMHO.

I believe the most likely reason for cracking of #8 dimples may be an insufficient chamfer (debur) on the bottom or top of the hole.
 
Last edited:
Bruce said:
Jim,

I reduced the pillowing affect almost to ZERO. I used a brown rolling tool and did all the rolling before I dimpled the holes.

Hope this helps and I think I have picks on my web site. (Somewhere)
Click to expand...

I came across this thread by searching for "pillowing" and wonder if someone can translate the quote above. I looked at Bruce's builders log and could not find any references.
 
Marc Bourget said:
Will somebody favor me by posting a picture of a "pillow effect"?
Click to expand...

There are seems to be two types of minor skin riveting defects referred as pillowing, not sure what the consensus. One is prominent when skins are overlapped, mitigated by tool referenced by previous poster.
Pillowing

The other type seems to refer to cases where skin is pushed by rivet toward underlining structure. Looks like victim of hail storm or a ball hammer.
Also Pillowing
 
You must log in or register to reply here.
Back
Top