

United States, FL, Tampa
Joined May 2012
13 Posts

Help!
Converting degrees to mm or inches
Anyone know a conversion on degrees to mm or inches. Trying to setup throws on a couple of my planes and don't have a protractor handy. Have my great planes throw meter but t only reads in inches and millimeters.Usually just use a builders protractor but mine seems to be lost. By the way, the plane is a 3DHS 72 Extra. I know you need the surface measurement (ie...aileron,elevator for an accurate measurement) but looking for a formula





SOH CAH TOA
The most relevant one here would be angle = sin^1(throw/chord) The windows calculator does the inverse sin function. 



Metric converter
I like this one. It's free and will do more than just leanths.
http://www.worldwidemetric.com/measurements.html 



Try doing it this way
Degrees are increments of a circle or arc. To simplify the exercise treat your control surface as something that will make full 360 degree motion. Using the following formula: Diameter x Pi, (3.14159), divided by 360 for 1 degree. The diameter of the circle in our case will be the width of your control surface x2. Then multiply the degrees travel with the above result to get travel in mm. Eg: Let us say that we need a elevator deflection of 40 degrees for the example width of elevator=50mm (that is the radius of your travel circle) multiply that by 2 to get your diameter. result is 100mm. multiply 100 by 3.14= 314 divide 314 by 360 = 0.8722mm multiply 0.8722 x 40 degrees 34.88 is your travel distance in mm hope this helps mike 



Quote:
40 degrees is not a small angle , so you should have said ~35 degrees. (Makes no sense to do 4 digits when the answer is out by ~8%) True answer for 40 degrees is 50*sin(40) = 32.14 Close enough I suspect, but since everyone has a calculator on the PC, why not just do the sin? Personally I usually just eyeball it anyway Pat MacKenzie 




I am LMAO!
You fellas just went so far over my little brain that I did'nt even see you go over! Well said by all and I think I will just use the eyeball technique! Max out the control surfface and only use what you need by the input of the gimble is what I do. 



Quote:
Soapbox speech: In all my years (and I have had nearly 200 models over the years check my blog, they're all listed there), I have never once measured my control throws. First of all, we really should be measuring angles, not inches (or mm's), as control surfaces don't always have a constant chord. Second of all, why should I accept someone else's values, when my personal preferences may be different? Thirdly, control sensitivity is a function of airspeed, so what may work at cruise speed may not be enough on approach, or in a thermal at minimum sink speed. Flight testing is still the best way to determine control throws, and eyeballing the throws in preparation for the first flight has always worked out just fine for me. 




Mik, you are absolutley right.
I will share this, the only RC plane that I have needed to actualy measure deflection of a control surfface on was a Tocanno .60 by World Models. I had used the ole eyeball technique as discribed above and almost lost the plane on landing. The Tocanno is very pitch sensitive and requires very little elevator to move it up or or down. Once I got it back on the ground I adjusted to the recommended throws with a Great Planes throw meter, and she flew fast and straight! The GP throw meter has inches and MM on it so it can be used for bothe SAE and Metric. 


United States, IL, Chgo
Joined Jul 2004
217 Posts

Hey guys, just coming across this thread.. Helpful, thanks to Mike and Pmack..
Question.. I've noticed my iPhone calc offers a sin function. Using the 50mm example, I'm assuming I cannot simply input 50*sin= Doing so gives me 38.30 etc .. but figuring the calculator would need to understand the 40 degree variable somehow..? If anyone can help me understand how to use the sin function would be helpful.. Raz 



I don't have an iPhone, but if you wanted to calculate x * Sin(y) on most calculators the order would be:
enter y { the angle} hit Sin hit * enter x { the length} So for the example above of 40 degrees deflection of a 50mm elevator enter 40 hit Sin display should read 0.6427.... enter * enter 50 hit = and it should display 32.139 
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