how long are your lead out wires? 


W.

It depends, as usual. How large a plane are you building? I'm doing a Veco P-51 - based F-82, with about 13" between fuselage centers. That's a very large span to have a single control horn on one side of the elevator, so there will be a bellcrank in each fuselage with a pushrod to each side of the elevator. Also, this thing will have throttle control, so I need separate linkages to the engines, too.

Ralph

Well, Will, that would certainly simplify throttle linkages, too. I'll give that a try first!

Ralph

I have seen several semiscale P-38's that were built with a single bellcrank/pushrod to the elevator.  The elevator flexed considerable to the point that performance was being compromised.  A double pushrod system eliminates any potential for any performance limitation relative to elevator flexing.

Keith

I love twin boomers, I love twin engines, but placement of the bellcrank can be a hassle.

On the Twin Flightstreak I used to campaign in Classic, I used one bellcrank. It was mounted so the pushrod went along side the outboard fuselage. I stiffened the elevatorwith a spruce spar, and if there was any flexing, it was negligable.

I designed a smaller twin boomer, called "The Raven", that had the bellcrank positioned so the pushrod routed through the inboard boom. Same type of stiffening at the elevator. This was a disaster, as the weight of the bellcrank, and pushrod, inboard of the centerline, required excessive tip weight to overcome.

My best recommendation today would be, never mount the Bellcrank, and run the pushrod down the inboard fuselage, or boom.

With modern materials available today, a single set of pushrods should be stiff enough, and much easier to set up. The threat of flexing is real and if not compensated for, can cause problems, if the plane is anything other than a sport plane. So if you don't want to use moden materials, like CF, the preferred method would be bellcrank in the center, dual horns and pushrods down each boom or fuselage.