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Did I just ruin this?

S

ShortSnorter

Well Known Member
Yet another did I ruin this:

About 3/4 of the way through dimpling the flanges of the 915 stiffeners for the rudder I noticed that the female die was making an ever so slight impression in the crease of the bend on the stiffener. The pictures of the internal surface of the flange exaggerate (due to light reflection) the "impression" made by the side of the female die. On the reverse side you can see and feel (albeit ever so slight) the protrusion. I do have reduced diameter dies but did not think to use them or check the clearance before I started whacking away on the C-Frame. What is the consensus?

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I think structurally, no. The stress region of the stiffener is on the edge at the beginning of your arrows. Stiffeners are cheap, so you could replace them with the next order pretty easy, if it bothers you.

It happens. :eek:

Oh - remember that one of the high probability occurrences in back riveting the stiffeners is to rivet OFF the backing plate, just a reminder.
 
BillL said:
I think structurally, no. The stress region of the stiffener is on the edge at the beginning of your arrows. Stiffeners are cheap, so you could replace them with the next order pretty easy, if it bothers you.

Thanks Bill!

It happens. :eek:

Oh - remember that one of the high probability occurrences in back riveting the stiffeners is to rivet OFF the backing plate, just a reminder.
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Hahah I've been down that road already. Hopefully I got all of that out on the practice projects.

Mel said:
Build--on!
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Thanks Mel!
 
If it was in the skin I would redo since small dents are highly amplified visually when painted. In stiffener I would just move on.
 
I ground part of the die face outside of the dimple area away so this would be less likely to happen.
 
You should use a small diameter female die for this application. Many places you will need one during the build. Get a #40 and a # 30.
 
Dies

All my female dies have a flat side for that reason. When dimpling with the squeezer I always tape the flat side to the head of the yoke so it can't rotate.
 
If there's a protrusion on the skin side of the stiffener and it's not very high, it'll be within the coat of Pro-Seal that some of us paint on the stiffener before riveting. If you're not doing that - if you're planning on riveting it bare, then any protrusion could affect the contour or flatness of the skin.

(The Pro-Seal is to hopefully avoid any skin cracking, although I think that's more prevalent with the .016 skins on the older airplanes like my RV-3B. It might not be worth doing on yours. And even on the older aircraft, it's only done, usually, for surfaces in the slipstream. I think.)

The only other thing to check for is whether there's any zero-radius bending, which aluminum doesn't like. Those are crack-initiation points, although as BillL pointed out, this isn't the most highly-stressed area of the stiffener.

If it were mine, and if either of these were the case, I'd replace them. Heck, I've replaced so many parts that a stiffener more or less wouldn't be noticed.

Dave
RV-3B, now building the second pair of fuel tanks, sigh....
 
Ron B. said:
You should use a small diameter female die for this application. Many places you will need one during the build. Get a #40 and a # 30.
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Correct
There are numerous instances that the manual will specify to use a reduced diam. female die. It is listed in the recommended tools list.
 
Grind an edge of the nose or make a flat...

You can get by fine by knocking off an edge from the nose of the die and nesting it against the tight spot... by the end of the build I had one die that ended up with a flat side that would fit any tight spot.
 
Not directly related to your question, but the edges need to be deburred and polished. You may have planned that for later but don't forget it.
 
rvbuilder2002 said:
Correct
There are numerous instances that the manual will specify to use a reduced diam. female die. It is listed in the recommended tools list.
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I do have reduced diameter dies and did end up using them to finish up. I just don't recall seeing the plans call for it in this particular step. Lesson leaned, I'll definitely size up the job before whacking away.

Here's a question: What's the purpose of "regular" size dies if you can use the reduced diameter dies? In other words, are they interchangeable or are the larger dies better to use in certain scenarios?
 
sprucemoose said:
Not directly related to your question, but the edges need to be deburred and polished. You may have planned that for later but don't forget it.
Click to expand...

Are you referring to the pictures? The ones in the pictures have already been polished and scuffed for painting. At the stage the pictures were taken I had planned on dimpling, cleaning with acetone and then priming. Do you see something unsatisfactory in the pictures that I may have missed (just got finished priming)?
 
ShortSnorter said:
Here's a question: What's the purpose of "regular" size dies if you can use the reduced diameter dies? In other words, are they interchangeable or are the larger dies better to use in certain scenarios?
Click to expand...

The larger dies are easier to square to the work and more forgiving if your squeezer is not aligned well.
 
ShortSnorter said:
Are you referring to the pictures? The ones in the pictures have already been polished and scuffed for painting. At the stage the pictures were taken I had planned on dimpling, cleaning with acetone and then priming. Do you see something unsatisfactory in the pictures that I may have missed (just got finished priming)?
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Looks good from here to me....
 
Dimpling is two stage. First the dimple forms. Then then die perimeter reflattens the piece. Larger dies flatten better (if they're good).
 
ShortSnorter said:
Are you referring to the pictures? The ones in the pictures have already been polished and scuffed for painting. At the stage the pictures were taken I had planned on dimpling, cleaning with acetone and then priming. Do you see something unsatisfactory in the pictures that I may have missed (just got finished priming)?
Click to expand...
I'm referring to the edges of the material (where it was cut) which appear very rough in the pictures. Pictures can be deceiving but that's that they look like to me. The edges should be smooth with all the tool marks removed. The edge of the stiffener web (top edge in the bottom photo) is in a highly stressed area of the part, where a crack is likely to start.

A cracked stiffener will probably not bring down the plane, but the tail kit is the place to develop good construction habits and practices.
 
I think they are sanded smooth, I think it's just the picture. I always smooth the part first thing , much easier and safer to handle. Also it's the most boring job, so get it out of the way.
 
airguy said:
Ditto this - you'll need to do it eventually anyway for dimpling nutplates.
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Not if you have one of THESE as recommended in the RV-14 construction manual.
This is small enough to dimple K-1100-08 nutplates.

I avoid modifying dimple dies if at all possible (though I do have some that have been).
For the crispest dimples, particularly on thicker material or when the dimple is large (like for #8 screws), having the full flat area of the die is better.
 
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