rtn9105

My Feedback: (35)

I'm setting up the control surfaces on a new plane and the manual gives all of the throws in deg. rather than inches. Can anyone tell me how to make a throw meter that reads in deg.?

technoheli

You didn't specify what size of control surfaces you are measuring and what type of aircraft this is on, so here is a relatively general response. Hope it helps!
You have a good question. The answer is both yes and no.... YES if all of the control surfaces you are measuring have the same chord (distance from hinges to trailing edge) of all of your control surfaces you are trying to measure. And the measuring device (such as a protractor) is always consistently equidistant from the control surface hinges. And NO because the accuracy of the degrees gets proportionally offset the further away the measuring tool, such as if you are measuring a very long chorded 3D style rudder.

This is the reason nobody commercially produces a universal throw meter measured in degrees. It just can't be done with any kind of accuracy. If you are measuring really big control surfaces, for example, with a chord greater than 3.5 inches, you'd need a really big protractor; THEN if you took that same throw meter with the really big protractor and tried to measure a control surface that has a chord of 3/4 inch, you wouldn't be able to be very accurate.
Another reason that manuf. go with throw metering in a std. measurement is because this is taken into account as the aircraft has been designed...in other words, the aircraft can only take so much throw, and can even go so far as to induce a parasitic drag stall of the wing. The throw in inches, is relative to the angle of attack of the wing, which makes measuring significantly easier.

RTN9105 - You can make one of these, however it will only be feasible if you are measuring the throws of relatively small throws of small chorded control surfaces. The easiest way is to buy the commercial throw gauge, and then replace the clear ruler with the metered end of a highschool protractor, then to use it, you'd have to cut off the straight edge of the protractor, and it is on that plane/vector where the hinge of your control surface would have to be square to. So if you are measureing control surfaces with less than 1 inch of chord, go for it!

Newc

One way to accomplish your goal easily is to start with the wing level and the control surfaces at "0" using an incidence meter. Then use a protractor such as http://www.sears.com/sr/javasr/produ...seBVCookie=Yes to set your throws. You may have to do a bit of addition and subtraction depending on the neutral reading of the control surface, but it is easy to do this way.

Clint H

My Feedback: (1)

I have used a method before for converting degrees into inches. The formula is rather simple, but be warned -- it involves algebra and trigonometry (yikes)! In this equation, angle is the degrees of movement recommended by the manufacturer, the hypotenuse is the chord of the control surface, and the opposite is the unknown for inches of movement. Please note if you try this, the inches in movement measurement must be taken at the same point you took the measurement for the chord of the control surface.
The equation is:
sine(angle)=opposite/hypotenuse
sine(angle) x hypotenuse = opposite/hypotenuse x hypotenuse
sine(angle x hypotenuse = opposite

I don't know if this helped or just confused you more, but I'd be happy to explain it if you have any questions.

-Clint

rcfury

My Feedback: (5)

Clint H... Amen my brother, i was about to mention using what we all learned in school. Some basic trig.
When you deflect a surface it creates an angle, when you draw an invisible line from the TE of the surface to the point where its neutral. YOu can created a right triagle.
Then fire up your brain and follow what Clint described.

Tall Paul

Protractor copied and pasted on foam board.
Foam board pasted on clothes pin.
Pointer adjustable for zero.
Bubble level on the reference surface.

rtn9105

My Feedback: (35)

After talking with one of the guys for the local club, he let me use his guage. Pretty much the same idea as your Tall Paul.

Thanks to everyone for the help

Newc

The use of the angle finder that you pictured above - basically the same as I gave the link to - will be more accurate than the set up that is shown by Tall Paul simply because the angle finder/protractor can be set on the horizontal stab and the plane leveled to zero degrees, while the bubble level can be off a couple of degrees without it being obvious. This is for a flat surface as shown on Tall Paul's photo, but to do the same thing for an airfoil - such as for the wing/aileron - you will need to use an incidence meter to ensure that the wing is level. Same thing for a horizontal stab that has an airfoil.

Tall Paul

Obviously the reference must be zeroed... however that is achieved!

muzzlemaggot

My Feedback: (7)

For what it's worth, I believe the Hangar 9 incidence meter (digital read-out kind) will measure the surface throws in degrees. I'm going off memory here.

scratchonly

Double the width of the control surface; eg 2" surface = 4"; multiply x 3.14 =12.56. Divide by 360 =.035. this is your inches per degree. 20 degree throw=..035x 20 = about .7 inch or between 5/8 and 3/4 inch. This will certainly be close enough.
This is all based on the circumferance of a circle which is 3.14xdiameter. Be sure to double the width of the surface.

Good luck.

rtn9105

My Feedback: (35)

scratchonly, thanks for the info. That's a nice simple way to convert the throws.
I actually had to have my 16 year old daughter help me with the algebra and trigonometry on the other conversion system [X(][X(]

rtn9105

My Feedback: (35)

One more thing, what measurement do you use if your control surface is tapered? eg my ailerons are wider at the root than at the tip.

scratchonly

It doesn't matter; use the largest chord (root). This makes it easier to measure. Be sure to double the measurement before starting calculation.