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Vertical stabilizer spar bend.

T

thoma015

Well Known Member
When I dimpled the front and rear spar it went developed a bend. Has anyone else had this problem and if so what do I do to fix it? I was bending it back and it started to buckle, lucky I didn't put to much pressure on it and was able to save it.

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Bend

It is possible to bend them back but as you have already discovered, they can fail.
You have to work them extremely slow. I bent my flap spar that way. A little impatient and overly eager. I don't recall mine bending.
Maybe one of the VAF experts can offer a solution.
 
Over squeezed?

Did you use the pneumatic squeezer I see in the picture? I would say that the skin stretched, either through mis-adjustment, wrong size holes or incorrect dimple dies. Of course, you know the usual way to get rid of a curve is by fluting. But I've never seen it on a spar like this.

I want to see what others think of this one. Good luck.
 
arffguy said:
Did you use the pneumatic squeezer I see in the picture? I would say that the skin stretched, either through mis-adjustment, wrong size holes or incorrect dimple dies. Of course, you know the usual way to get rid of a curve is by fluting. But I've never seen it on a spar like this.

I want to see what others think of this one. Good luck.
Click to expand...

I did use that squeezer. I was under the impression that it doesn't matter how hard the dimple dies squeeze, and I used 3/32 on the spar.
 
This is a rather important part. You might check with Vans tomorrow about it's use. Ribs get fluted, but this a serious structural part, and any ability of that flange to carry tensile load is lost with flutes. Maybe it is ok because the skin will carry it, but Vans should be the final answer.

I would replace it. It will keep your tail out of trouble.
 
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Rather strange. I used my squeezer to dimple that part when i built my VS last year. My results were just fine with no adverse effects. I don't think you can actually get that into a drdt2 so not sure how else you would do it. Must of been a fluke. Call vans but with it being such a cheap part, i would just be calling to order a new one. I wouldn't bother messing with something inexpensive. my 2 cents
 
I did the exact same thing to the same part. I used too much pressure on a pneumatic squeezer and probably had the dies set too tight as well. It bowed the snot out of the rib and I had to replace it. Valuable lesson learned, as the squeezer essentially stretched the flange and made the rib bow. Now, I set the dies to where they just barely touch on the squeezer.

You may be able to flute and salvage the part if it's the inside rib. If it's the main spar at the rear, it can't be fluted or the rudder might scrape it as it swings left and right.
 
I just dimpled this same part today without an issue. I dimpled before priming though. Don't know if that would have anything to do with it. I see your squeezer is different than the one I got from cleaveland tools. I used 90 psi at the squeezer, then adjusted the dies by activating the squeezer and turning the adjustable set holder until the dies butted together tightly.
 
That looks to me like a case of over dimpling. I'd be ordering a replacement part if it were my build.
 
It's been well over 3 years since I built my VS, so without going back to my logs I don't remember if I had this problem, or if I did, what I might have done to resolve it. I'm really surprised that no one so far has suggested asking Vans tech support. If you aren't comfortable with the part, wait a couple days and ask the experts.

Having said that... Did you use the female dimple die with one side ground flat to avoid distorting the inside radius of the bend?
 
When I used my pneumatic squeezer, I also used an adjustable set holder so I could precisely adjust the closure and prevent over squeezing. Adjusting the set holder to just close the dimple dies when fully extending the squeezer seemed to work well for dimpling most metal thicknesses. Typically, anything over 0.030" should be counter sunk and not dimpled. Using washers to adjust the set holder is very inaccurate.

Also, make sure the hole is drilled out to the final diamter and deburred before dimpling. Dimpling undersize holes will stretch the metal causing it to curve.

Roberta
 
Bend

All, thanks for the replies. The pictures make it look way worse than it really is, but is still a problem non the less. I went ahead and built up the structure of the VS and there is just barely a bend after everything is together. I will call vans and get their input but I think it will be ok.

Here is a picture of my helper with it assembled

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And in the future I will make sure not to over squeeze
 
Like some others, I ended up with curved flap spars which are similar to that. Maybe it's too much squeeze, I don't know. I did use a female die with the corner ground off th avoid denting the inside of the spar bend. I managed to fold one trying to straighten it, so like many before me ordered another one. I did get them back to perfectly straight by slowly and gently working them on the edge of the work bench. Instead of trying to take all the bend out at once, I just took a little at a time and gradually worked out the curve.

I'd suggest getting it as straight as you can before assembling. You don't want to have to force things into alignment or have built in stress. Just work it out gradually and gently and don't get impatient.
 
Female die

longranger said:
It's been well over 3 years since I built my VS, so without going back to my logs I don't remember if I had this problem, or if I did, what I might have done to resolve it. I'm really surprised that no one so far has suggested asking Vans tech support. If you aren't comfortable with the part, wait a couple days and ask the experts.

Having said that... Did you use the female dimple die with one side ground flat to avoid distorting the inside radius of the bend?
Click to expand...

Good advise.
I can't tell in the photo if your female die is ground flat on one side to clear the web but this is good advise for the future. All mine have a flat side. I use a narrow piece of gorilla tape around the die and yoke so it stays in the correct position and can't scratch parts.
 
RE: Bend???

If it were me I would buy a new spar. The last thing I want to think about at ten thousand feet is .... I wonder how the slightly bent spar is????? I made up my mind early in my 7a build if it made me wonder I would just redo the part for peace of mind. I only had this happen a very few times and Vans (Ken) always bore out my assumption which was to redo with new components.

Good luck and have a fun safe exacting build .......
 
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