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Longeron bend and twist. (used Buller Enterprises Dies)

Ken Martin

Well Known Member
Well I decided I didn't like the idea of beating the longerons into submission as described in the plans when a set of precision longeron dies could be had for a few bucks. I am SO glad I invested in these. I have no connection to Buller Enterprises and have never even spoken with them but as I write this I feel it necessary to give them their credit due.

I ordered the longeron dies and center section spacers and they were shipped immediately. I wasn't really looking forward to this as I've had to redo a few items that weren't up to my standards. (sometimes I hate having an Engineer's mindset) So I read through the directions and did exactly as they described.

1. Mark the curve start/stop point and place a mark every 1 inch for the bend process.
2. Place black electrical tape along the vertical flange of the angle to avoid marring.
3. Apply grease to the horizontal section to allow the die to slide easily.
4. Place the angle and die in a vice and slowly squeeze the vice along each 1 inch mark. Don't overcrank.

Well that seems easy enough. I did exactly as directed giving 90 to 130 ish degrees of vice handle rotation along each 1 inch marking. It took me 15 minutes to set up as I was being very careful to follow the directions and only 5 minutes to get the curve within Van's 1/16th in tolerance. I had to double and triple check myself to see what I must have done wrong considering it was that easy. I give credit to the dies. It was right on!

I then constructed a "T" out of wood to bend the angle down 2.75 inches and the twist 17 deg. This went very smoothly as well. After bending downward I placed a large crescent wrench on the horizontal flange and twisted approximately 270 - 300 deg to get the material to retain a 17 deg twist. I check everything with a protractor and digital level. I also placed the now formed longeron onto the plans template and placed the Aft Canopy deck (F-721B) on it to double check. Everything lined up great. It may need some slight tweaking once it gets assembled permanently; but that's no problem. Below are a few photos I took of the process.

Thanks again to Buller Enterprises for a fast shipment and great product.





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What are the center section spacers? Just curious.
I also bought the longeron dies. That's a few weeks away for me. Nice to know they work.
+1 for the Buller Enterprises dies.

They made the job of forming the curve in the longerons quite easy and without the need to beat them into submission ... only minor tweaking was necessary after the bending process.
What are the center section spacers? Just curious.
I also bought the longeron dies. That's a few weeks away for me. Nice to know they work.

Buller Enterprises machines precision spacers for your center section so you don't have to try and make them out of wood yourself. Check out their Vendor ad in the advertisor's index. It's labeled "Longeron Dies / Canopy Guides".
George Orndorff's method for bending longerons worked well for me. His method for curling the lower aft corners of the forward side skins, not so much.