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F996A Brackets--how the heck did you all bend them???

B

BruceP

Well Known Member
After fabricating the F996A fuel tank attach brackets for my 9A (I assume they're the F796A's for the 7's) I attempted to bend in the 2.7 degree angle required to fit them. I could not do it myself even though I had them in a vise and literally jumped up and down on it trying to bend it. I took it to a metal shop in town where they used their considerably more appropriate machinery to make the bend. The only problem is the metal cracked on the outside radius ever so slightly, it didn't look too deep but I didn't like how it turned out. So, for the not so nominal cost of $80 they are fabricating two new ones for me using their CNC milling machine. Should be beautiful but probably overkill. They tell me the problem is the 6061 aluminum that thick isn't meant to bend without it cracking as it did and heating it would weaken it as well. They are making the brackets out of 5052 which they say will take a bend without cracking. I'm just wondering what the thousands of the rest of you did when bending these brackets???
 
Check the Plans

If you are talking about the brackets that attach to the leading edge of the tank, from memory on the 7, you are meant to bend the steel brackets that go onto the side of the fuse. The angle is 3/16 ... you will never bend that without heavy equipment and it will most likely crack.

Richard
 
Yes, those are the brackets I'm talking about. On the 9 it is made from AA6x187x2 x 2 1/2, not steel.
 
Ok, On a 7 it is a F-796A-L/R that bolts to the fuse and they are made of steel. The other end is a T-405 and that is riveted to the tank. So I guess that answers one of your questions - the rest of us did it pretty easily by bending the steel bracket.

You might have to ask a 9 builder how they did it. 2.7 degrees is not much - I might be tempted to wait until fitting the wings the first time and see what is required.

Good Luck
Richard
 
I just put mine in a vise and whacked on the end of it with a 3-pound sledge a few times (not too aggressively), checking the fit against the fuselage & tank each time until it was the appropriate angle. I did not see any cracks or other structural issues. I did this AFTER cutting the angle to the appropriate shape, and hammered on the radiused edge where the attach hole is located. The flat section where the angle attaches to the fuselage was held in the vise.

greg
 
BruceP said:
I'm just wondering what the thousands of the rest of you did when bending these brackets???
Click to expand...

Bent them in a big vice with a big hammer.

The angle change is no where near enough to cause a crack.
The shop that bent yours for you must have made a very tight concentrated bend. Every thickness of aluminum has a minimum bend radius. It is not a concern with these parts when using a vise because it is not possible to make a tight radius bend.
The shop must have used some tooling that made a very tight radius bend
 
Scott, you're probably correct about the tight bend. Greg, I did try to bend after cutting to the appropriate shape. I guess I just didn't have a big enough hammer and a stable enough vise!!!:D
 
I put it in a vise with wood blocks to not mar the aluminum and then beat it with a mallet. Worked well, but the strikes need to be towards the angle and not the bracket end so you don't generate a curve.
 
Angles

I clamped mine in a shop press, and eased the angle in rather effortlessly. If you have access to this setup, it works well. Check your local auto service shop, he might let you use his press and press plates real quick like....

Regards,
chris
 
Wood block

I cut a wood block and held it against the part in the vise so the energy from the hammer blows was concentrated near the angle...brute force and a hammer is the answer. Like others have said, I don't know how you cracked anything with a 2.7 degree angle...luckily, it's not an expensive part and you'll be more experienced the second time around, lol. good luck
 
Used the mechanical advantage of the vise jaws

I put the tank attach angle in a vise with one wing on each jaw and then closed the vise a bit at the time checking the fit to the tank after each tightening until the angle was "just" right. I had first tried to bang it with a hammer to no avail. The mechanical advantage of the vise slowly closed the angle with not visible cracking etc.
 
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