Bill_H
Well Known Member
I've been dreading the longerons but could put them off no longer.
Luckily I have a friend a few miles away who has built RVs before - but not a 12.
The first step is opening the 95.4 degree angle. Like so many things it is simple with the right tool, which my friend had. The right tool is not a hammer. It is not a vise. It is a press. Like this one that sells for $90.
http://www.harborfreight.com/6-ton-shop-press-4711.html
Find someone with one of these or something similar. Get a 2 inch long piece of 3/4 inch pipe. My friend had some 3/4 inch aluminum bar stock - he cut off a piece and ground a flat on one side so it would not roll around.
Practice first with a piece of scrap, like the piece that you just cut off to cut the longerons to length. Put the pipe on the stand, and the longeron on top, pointy side up. Cover that with a small piece of bent scrap aluminum just to protect the longeron. (Don't use a scrap piece of the longeron because of the fillet on the inside corner).
Jack the press down and squeeze. Have your finger touching the longereon edge and the piece of pipe so you can feel it move. The 95 degree angle opens very easily and that edge will move very little relative to the piece of pipe - but you will feel it. Practice with the scrap and you will soon get a feel for it.
Working from the end, I would squeeze, then remove and check the angle each time. Then I would move the centerline of the squeeze point about 5/8 inch and repeat. Given the learning curve and scrap practice, doing this part of both longerons took an hour. Sometimes I squeezed a bit too much. It is easy to remedy that in the vise later.
As you get near the end of this task, keep checking the "stop bending here" line to be 90 degrees and note how far away from the squeeze point that the longeron remains unbent. You will be able to stop squeezing about 1.25 inches from the "stop bending here" line and achieve that smooth transition.
The right tool makes this job easy. If you start out frustrating yourself by beating angle with a hammer you will be in a bad mood for the entire job!
If you enlarge the angle too much, it will make a small "hump" relative to the correct angle adjacent to it. You can squeeze it back a bit with the vise. Don''t put it horizontal in a long vise so you are squeezing 6 inches of it though! Put it in the vise at a vertical angle and squeeze less of it. You can also hit it with a hammer on a flat piece of metal to flatten out a hump. A piece of metal like those black pieces on the bottom of the press in the picture above is ideal, because the cutouts leave a place for it to go when you hit it with the hammer.
The longeron bending then proceeded per Van's instructions. Place the longeron in the vise. We used c-clamps and clamped the guide piece onto the top of the longeron during the bending process rather than going back and forth. One of us would do the preload bend, the other would THWACK the longeron right at the vise, with a hammer hitting a small hardwood block. (Be careful to not hit the guide piece.) In pulling the preload, I could see where the end of the bending portion of the longeron was relative to the clamped on guide. I would bend about 1/4 inch beyond that, then THWACK. As you pull for the bend, keep the longeron level with the clamped-on guide and also twist it a bit clockwise. This helps keep it flat.
Generally we would bend and THWACK 3 or 4 times, and it would be aligned. We would move it by one rivet hole and repeat.
The resulting longeron was not flat but was close. Lay it upside down (flat) on a table to see where to adjust. Follow Van's instructions about putting it back in the vise at a 90 degree angle and bending back. We were able to get it flat without messing up or redoing any of the curve.
The 4 degree bend at the aft end was easy. Have that short end sticking out of the vise. Prebend it with a big crescent wrench on the end. About 8 THWACKS and you will be there. There will be a little hump on the top, take it off later at your belt sander.
Having the longerons behind me feels great and was not nearly as bad as I expected. I was sure glad to have the experienced help. Maybe this description will help you if you don't have such help available.
Bill H. N412BR Kit #412
Luckily I have a friend a few miles away who has built RVs before - but not a 12.
The first step is opening the 95.4 degree angle. Like so many things it is simple with the right tool, which my friend had. The right tool is not a hammer. It is not a vise. It is a press. Like this one that sells for $90.
http://www.harborfreight.com/6-ton-shop-press-4711.html
Find someone with one of these or something similar. Get a 2 inch long piece of 3/4 inch pipe. My friend had some 3/4 inch aluminum bar stock - he cut off a piece and ground a flat on one side so it would not roll around.
Practice first with a piece of scrap, like the piece that you just cut off to cut the longerons to length. Put the pipe on the stand, and the longeron on top, pointy side up. Cover that with a small piece of bent scrap aluminum just to protect the longeron. (Don't use a scrap piece of the longeron because of the fillet on the inside corner).
Jack the press down and squeeze. Have your finger touching the longereon edge and the piece of pipe so you can feel it move. The 95 degree angle opens very easily and that edge will move very little relative to the piece of pipe - but you will feel it. Practice with the scrap and you will soon get a feel for it.
Working from the end, I would squeeze, then remove and check the angle each time. Then I would move the centerline of the squeeze point about 5/8 inch and repeat. Given the learning curve and scrap practice, doing this part of both longerons took an hour. Sometimes I squeezed a bit too much. It is easy to remedy that in the vise later.
As you get near the end of this task, keep checking the "stop bending here" line to be 90 degrees and note how far away from the squeeze point that the longeron remains unbent. You will be able to stop squeezing about 1.25 inches from the "stop bending here" line and achieve that smooth transition.
The right tool makes this job easy. If you start out frustrating yourself by beating angle with a hammer you will be in a bad mood for the entire job!
If you enlarge the angle too much, it will make a small "hump" relative to the correct angle adjacent to it. You can squeeze it back a bit with the vise. Don''t put it horizontal in a long vise so you are squeezing 6 inches of it though! Put it in the vise at a vertical angle and squeeze less of it. You can also hit it with a hammer on a flat piece of metal to flatten out a hump. A piece of metal like those black pieces on the bottom of the press in the picture above is ideal, because the cutouts leave a place for it to go when you hit it with the hammer.
The longeron bending then proceeded per Van's instructions. Place the longeron in the vise. We used c-clamps and clamped the guide piece onto the top of the longeron during the bending process rather than going back and forth. One of us would do the preload bend, the other would THWACK the longeron right at the vise, with a hammer hitting a small hardwood block. (Be careful to not hit the guide piece.) In pulling the preload, I could see where the end of the bending portion of the longeron was relative to the clamped on guide. I would bend about 1/4 inch beyond that, then THWACK. As you pull for the bend, keep the longeron level with the clamped-on guide and also twist it a bit clockwise. This helps keep it flat.
Generally we would bend and THWACK 3 or 4 times, and it would be aligned. We would move it by one rivet hole and repeat.
The resulting longeron was not flat but was close. Lay it upside down (flat) on a table to see where to adjust. Follow Van's instructions about putting it back in the vise at a 90 degree angle and bending back. We were able to get it flat without messing up or redoing any of the curve.
The 4 degree bend at the aft end was easy. Have that short end sticking out of the vise. Prebend it with a big crescent wrench on the end. About 8 THWACKS and you will be there. There will be a little hump on the top, take it off later at your belt sander.
Having the longerons behind me feels great and was not nearly as bad as I expected. I was sure glad to have the experienced help. Maybe this description will help you if you don't have such help available.
Bill H. N412BR Kit #412
