I am installing a set of du-bro heavy duty control horns (see picture).
I do not have the instructions anymore, and I was wondering how far behind the hinge line I should drill the hole for the screw.
Thanks

the pin hinge should be directly over the hinge line.

what he said

That is what I thought. Thank you. Much easier than installing standard nylon horns.

this one is from Dubro. it shows it better

Originally Posted by FGNewbie

the pin hinge should be directly over the hinge line.

Yep, you will be happy with it there. I use these on most of my gas planes and have not had one fail yet!

I install these just far enough back on the control surface so they are secure and on solid wood. I then shorten the long black plastic piece and redrill a hole for the clevis pin so it is perpendicular to the hinge line. If you leave these unaltered and install them too far back on the control surface, the surface movement won't be linear to the servo movement because of the arcing movement of the attach point.

That particular servo horn is configured for a flat surface. There's several styles, that are made to conform to whatever you're installing it on.

I'm hoping you're putting on a flat stab, or flat surface. If that's going on a tapered surface, it will all dig in, and actually look pretty bad, at least from most angles.

f you're putting it on a tapered surface, this is the one you need...

https://www.dubro.com/collections/co...e-control-horn

The only reason I mention that is nearly every plane on the market these days has tapered everything. If yours is flat though use what you have.

Say it's an aileron, with a taper, there's a kit that has convex/concave washers that form as you tighten the post, and make a perfectly true seat for that post.

As Truckracer said, you're not bound necessarily by the length of that that flag-arm either.... I've trimmed that arm to the length needed, so I don't have to put the post so far away from the hinge line, yet still get the pin (that connects everything)centered smack on the hinge line. Those flag arms are rather long, and can be trimmed a bit... so don't be afraid to experiment and study it all before you drill.

So what type of surface is this going on?

Flat surfaces of a ultimate bipe ( rudder and elevator). Thanks for the explanation

Originally Posted by ululi1970

Flat surfaces of a ultimate bipe ( rudder and elevator). Thanks for the explanation

Great. You'll do just fine.

I've been impressed with the Dubro hardware for the last 5yrs or so as there's many styles and types, for seemingly every application. from micros to giants now.

They've really stepped up with quality too. One of the best surviving RC suppliers around these days.