WMAC Group build - Impressivo

With regards to push rods why not use some 2mm helicopter ball link's with 2mm threaded rod sleeved with some carbon rod and lock nuts?

can buy one carbon rod split the cost and I would of thought there would be enough for several models?
same with the threaded rod I guess!!!

DavidTappin wrote: As a matter if interest, did all three have their elevon horns on top like Jon's? I was a bit concerned about how weak the push rods seem and worried about them flexing in compression and allowing flutter. Mine are underneath like Mike's which has been reported as the fastest and, presumably, flutter free, but I'll be sleeving them with carbon tube to make sure they keep straight.

The top horn point could well be valid, you are losing some mechanical advantage for sure. It is impossible to be sure if flutter caused the hinge to fail, or the other way round. When I rebuild mine, I am going to change to a bottom horn, with robart hinges and still seal the hinge line with film. Also the rods will be changed or stiffened with carbon tube. If it happens again after all that, it's going in the bin

I will be changing my linkages to 2 or 2.5 mm. I don't see why top or bottom makes any difference to strength (can somebody explain this?) Seems to me that if one linkage buckles while pushing in compression in a high speed manoeuvre, then, when the controls return to neutral, one of the surfaces goes too far the other way pulled by the bent rod, hence a rapid flip over and spin down. In Simon's case, spin not apparent due to low altitude. Clearly a design fault.

Phil-C wrote: I don't see why top or bottom makes any difference to strength (can somebody explain this?)

Phil, it's about mechanical advantage, with the horn on top the distance of the drive position from the hinge point is the length of the horn, when on the underside, it is the horn length plus the depth of the aileron, probably an additional 10mm. Does that make sense?

Just checked my photos, Simon's linkages appear to be on the underside, mine and Dave's on top. I didn't hear any flutter from Simon's, it just rolled in, so that might have been a different cause??

Jon, understand now, thanks. Doesn't apply to my top mounted horns because the Kavan hinges are on the neutral axis of the wing.

Still going to thicken the links. Also try to remove the prop driver eccentricity