When setting the control throws is it best to measure from the widest part of the contol surface or the shortest?

I am using a Great Planes throw meter and get different readings when I measure from either end.


Thanks for any help guys

Charts

When the plans or instructions give a throw measurement, most give the added information about where to measure it. And almost always it's the widest part.

BTW, don't get too intent on getting the throw exact. Close will do. Their amounts are chosen to be safe for their CG location which is usually also a very safe one.

You and the airplane will sort out what the CG really should be as well as the throws from flying.

They don't usually tell you where to connect the pushrods to the servo arm and horns. That's actually worth mentioning. It's often just luck of the draw for a lot of beginners. The one thing you want to be sure of, is to have the connection at the servo shorter than the connection at the horn. That insures the servo will have good leverage to begin with and you'll have a good start with those connection adjustments. Lots of builders simply hook the pushrod into the servo arm at the inner hole and then see if any of the holes in the horn work to give the throw needed. That insures the levers at each end are favorable to the servo. But there is a 2nd step to that that does even more.

If the connection at the horn doesn't wind up in the outermost hole, it's worth doing a second round of adjustment. If there is an open hole farther out the horn, and one farther out the servo arm, then move both connections out one hole. Try the throw and if it works......... you've kept the leverage in favor of the servo. Always a good thing. And you've reduced the play in the system's ability to affect flutter.

That's great Rock, thanks .


Charts

BTW, even if you have a computer radio, the servo's will work with more power and use less power if you rig the airplane with a couple of things in mind.

Set the radio's end points or throws to be 100%, no more, no less. The radio to servo information is best sent at that setting and that works best with the servo's design.
Now do any changing of throws in the airplane in the rigging. That way, you can control the lever-arms at the servo and at the horn. You can insure the servo has a mechanical advantage or at least has the most favorable disadvantage (3D setups for example).

The computer radios really are kewl and their endpoints and such are very worthwhile, but best saved for fine tuning. The guys who wind up with setting like 140% in the radio aren't getting 140% movement at the surfaces and have dulled the radio's accuracy and reduced the servo's power and resolution and increased the servo's demands on the battery. Sound crazy? It is. And it's true. Nothing of value from doing it and everything less value. So do everything in the airplane that you can.

On the same lines, if you plan to setup dual rates, it's easy. And computer radios are excellent at it.

You've already rigged the airplane's throws as above so the airplane is giving the best of what it's got to give. As described above. So........

Set the high rates at 100%. Airplane and dual rate switch good to go for high rates.
Set the low rates at whatever you want, like 70%.

You got dual rates and at the best settings for the battery in the airplane and all the servos that're going to be called on for those dual rates. Especially when set to high rates.

Same reasons as above.

And later on, if the high rates don't seem high enough.... what to do????? Simple. Work on the rigging in the airplane to give you more throw. Same reasons as above.