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Longeron Bending - 4 degrees of difference

bhassel

bhassel

Well Known Member
Ok to start with I have the longeron dies and they are great!

My question is about the back 6 inches where the inboard 4 degree bend goes. I've been looking ahead (or trying to) and notice that's in the area where the tailcone comes in. So does the 4 degree bend start at the bend and its 4 degrees all the way out to the end or is it a gradual bend which ends up at 4 degrees (much like the bend in the middle)?

IMG_0306.JPG
 
I worried about that bend for a long time - until I finally attached the tail cone. Obviously if you make an error, it will either poke out or suck in the tail cone when you rivet it to the longeron. Mine came out perfect to my relief.
 
I tried beating on that end and haven't made a dent. This is one item I'd love to buy pre-made...grrrr....

I'm sure I understand how I can get a 4 degree bend; compressing one side by quite a bit and expanding the other...

Bob
 
You said you had the dies, why are you beating on it?

bhassel said:
I tried beating on that end and haven't made a dent. This is one item I'd love to buy pre-made...grrrr....

I'm sure I understand how I can get a 4 degree bend; compressing one side by quite a bit and expanding the other...

Bob
Click to expand...
 
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Bob ? Don?t remember it being that hard to bend the aft end of longeron ? however I had to fuss with it quite a bit to get it to my satisfaction once it began to bend.

Prior to bending I did make the optional weight saving cuts with a band saw to remove the extra material as suggested in the plans ? the bends were completed while the longeron was clamped in a vice and beating it into submission with a soft faced dead blow mallet. The cuts may have made it easier to make the bends.

Happy building,
 
I do have the dies, but they put a gradual bend in the longeron. Exactly what I needed for the template portion in (sort of) the middle. This requires a sharp bend at 4 degrees.

My father-in-law had a smart idea of turning the longeron over 90 degrees in the vice, so that I was beating down on it. That worked and went pretty quickly. Just have a little twisting left on the left one, then its on to the right one.

Thanks!

Bob
 
I remember taking a sliding t-bevel and setting it up with a 4 degree bend and chucking the end of the longeron in a vice and easily bending it by hand using the t-bevel as a guide.
 
I did exactly what Dave12 did. Worked fine and took about 30 sec. No need to use the sledge-hammer technique or dies.
 
I used the dies and well greased them per the instructions and it worked fine for all the angles if I recall correctly. I think the angle you are referring to is the one that goes into the tail cone at the back. Either way, everything is a pretty tight fit on this airplane and you want to be sure all the angles and measurements on the longs are pretty close to perfect or you will have problems elsewhere.
 
I also used the dies for all bends, and it came out perfectly for me as well.

cactuspilot said:
I used the dies and well greased them per the instructions and it worked fine for all the angles if I recall correctly. I think the angle you are referring to is the one that goes into the tail cone at the back. Either way, everything is a pretty tight fit on this airplane and you want to be sure all the angles and measurements on the longs are pretty close to perfect or you will have problems elsewhere.
Click to expand...
 
cactuspilot said:
I used the dies and well greased them per the instructions and it worked fine for all the angles if I recall correctly. I think the angle you are referring to is the one that goes into the tail cone at the back. Either way, everything is a pretty tight fit on this airplane and you want to be sure all the angles and measurements on the longs are pretty close to perfect or you will have problems elsewhere.
Click to expand...

Yes that's the one. I was able to get a 4 degree bend at the bend line. I didn't think using the die's would work here as it would have been a gradual bend...but then I didn't sleep in a Holiday Inn last night...

Bob
 
I should also say, that if I need to redo the longeron because of that bend, now's the time to reorder.

Bending and beating just seems so anti RV-12...

Bob
 
bhassel said:
I tried beating on that end and haven't made a dent. This is one item I'd love to buy pre-made...grrrr....

I'm sure I understand how I can get a 4 degree bend; compressing one side by quite a bit and expanding the other...

Bob
Click to expand...

Bob... It was much easier for me to make the 4 degree bend before I cut the longeron to length using the extra material for leverage. Also Vans can send you new longeron material at very reasonable shipping.

Jeff
 
bhassel said:
Yes that's the one. I was able to get a 4 degree bend at the bend line. I didn't think using the die's would work here as it would have been a gradual bend...but then I didn't sleep in a Holiday Inn last night...

Bob
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You thought correctly.
The bend at the described location needs to be a 4 deg bend at that point.
Not a 4 deg. bend. distributed about a generous radius, across that point.
 
Good shot, thanks Joe. I was wondering what I was looking at before! LOL!

I notice that you have your holes already drilled in, I guess there were a lot of little things different in the first builds.

Thanks!

Bob
 
Over Thinking

Bob
I did not follow the plans
The skin is not bent at 4° that is why I drilled the holes first.
And Note: The countersink for flush Rivets
I like over thinking things.




bhassel said:
Good shot, thanks Joe. I was wondering what I was looking at before! LOL!

I notice that you have your holes already drilled in, I guess there were a lot of little things different in the first builds.

Thanks!

Bob
Click to expand...
 
rvbuilder2002 said:
You thought correctly.
The bend at the described location needs to be a 4 deg bend at that point.
Not a 4 deg. bend. distributed about a generous radius, across that point.
Click to expand...

Has anyone done this 4 degree bend with the dies successfully? I just got an email from Van's tech support today that said that this doesn't have to be a sharp angle and that a curve will be just fine??? We used the dies and if we have to redo, I would rather do it now than discover a problem later.

Steve
 
Cut later!

I don't remember having any trouble with that bend. Into the bench vice and a 4# sledgehammer hitting a block of hardwood. Nice easy/short bend with no stress puckers, etc, from the longeron.

I do recommend that you cut the the longeron to length after you complete the bend. Makes it far easier to complete the bend but most importantly, you won't end up short on the longeron. I darned near cut mine too short! It's easy to cut after completing the bends and as far as I can see, if the longerons are a little longer, it doesn't hurt anything.
 
I'd recommend making the lightening cut from the top of the angle, then put the end into a vice and give the long end a good solid pull. Check angle and repeat as required. No need to overthink this one, it's really easy.

Worked for me.
DaveH 120485
 
We already did the bend to 4 degrees. But we utilized the longeron dies and it created a bit more of a curved versus straight 4 degree bend. So I am just wondering if anyone else did it with the does instead of the hammer. If the does creating more of a curved bend will be an issue I would rather know now than later where it could potentially be a much bigger problem. In some weird way it was actually kind of fun to make the first sets of longerons.

Thx
Steve
 
Once you fit the longerons, that bend is at the baggage bulkhead. The longeron then goes into the tailcone, which has straight sides. To my way of thinking, the bend should happen quickly, you don't want a gentle curve. It follows the underlying structure which does not curve.
I found the longerons one of the most satisfying steps up to that point in the plans. How well they fit determines how almost everything else fits. I've said it before, it's not that hard, but it takes patience.
Hope this makes some sense.
Love the canopy lock!
Regards, DaveH
120485
 
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daveyator said:
Once you fit the longerons, that bend is at the baggage bulkhead. The longeron then goes into the tailcone, which has straight sides. To my way of thinking, the bend should happen quickly, you don't want a gentle curve. It follows the underlying structure which does not curve.
I found the longerons one of the most satisfying steps up to that point in the plans. How well they fit determines how almost everything else fits. I've said it before, it's not that hard, but it takes patience.
Hope this makes some sense.
Love the canopy lock!
Regards, DaveH
120485
Click to expand...

That's kind of what I thought. The initial set turned out really nicely except that the aft end has a gentle curve in it. I'll save this first set of longerons and make another and see how they come out. I actually found it satisfying too!

Glad you like the canopy lock. It's proven to be a popular item so far. Working with the rv community has been great. Those of you who know me know how much I love prototyping new things!
 
Aircraft Specialty said:
We already did the bend to 4 degrees. But we utilized the longeron dies and it created a bit more of a curved versus straight 4 degree bend. So I am just wondering if anyone else did it with the does instead of the hammer. If the does creating more of a curved bend will be an issue I would rather know now than later where it could potentially be a much bigger problem. In some weird way it was actually kind of fun to make the first sets of longerons.

Thx
Steve
Click to expand...

If the longeron dies make a bend that matches the (large) radius of the fuselage side, it will not be anywhere near the sharpness of bend that is intended in the KAI instructions.
 
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