Engine Mount Bracket to Longeron Fit
 

As many build logs as I've been through, I'm surprised I never noticed this before.:o I trial fit my firewall last night, and noticed that the fit of the engine mount bracket "fingers" fit well at the forward end, but because of the twist in the longeron, the fit at the aft end isn't so good:



My question is, do I need to manually twist the fingers to match the longerons, or just clamp them like crazy?

I would give the longerons some more twist to match the weldment fingers.
The fit of the forward top skin is very tight, so having a bit more twist will help.

Thanks for the heads-up on the forward skin, Bruce. Do you mean that the forward 6 inches of the longeron will be more or less straight and the fingers will remain flat?

Are your fingers welded together ? You definitely do not want to try and twist the steel fingers ... Twisting the longeron is the way to go ... you may also have to carefully round the edge of the steel fingers so they nest nicely into the longeron radius ..

In the 6 manual it does say to NOT force this assembly together .. but to make sure that the longeron has the right 'twist' so that it matches the steel bracket (fingers) .. before you clamp and drill - Drill small and enlarge to final size. Make sure it is well clamped when you drill - it is easy to 'enlarge' the hole in the longeron when you drill from Softer into Harder material ...

I just got done with my forward section too. I had to keep twisting the longerons until they fit.
I wouldn't try to twist just the finger section though. I took the clecos out of the skins and clamped the longerons down on the sawhorse with a solid metal clamp. Then using a crescent wrench i kept adding a little more twist until the firewall bracket lined up. It looks like you don't have much to go.

Jan,

On my RV-7 engine mount brackets, only the forward inch or so of the "fingers" are welded. The rest of the length from there aft is bridged with powdercoat, but isn't welded.

What I'm hearing from the others is to twist the longeron until they fit at the aft end, and to NOT twist the bracket fingers. If that is the case the longeron needs to be straight (not twisted) along the bracket. Sounds like the original 11-degree twist should be made with the wrench about 6 inches aft of the forward end of the longeron.

The instructions for the lower longer on note that the twist should begin at the point that coincides with the aft end of the bracket, and I am assuming the same goes for the upper mounts and longeron, meaning hold and twist the longeron at that point so that the section against the bracket is not twisted any further, so i think you are on the right track.

Mine also required a lot more twist than what was called for.

yep, you need to twist it more (the longeron)

Miles
Im sure it was just a typo, but the original twist is 17 degrees. Drawing 18 A-A.
Be one with the metal. Clamp the longeron at the 28 1/4 location and twist the end to get the desired 17 degree number. A note on the plans indicates the 28 1/4 point is the end of the twist. Don't twist just the last 6 inches. Twist the whole kit and caboodle.