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Old Apr 10, 2014, 02:45 PM
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gquiring's Avatar
United States, SC, Summerville
Joined Jun 2001
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Degrees to inches help

I am building an Albatros from Top Model and the throws are in degrees. I don't have an incidence meter and never ran into a manual before with degrees. I read that I can take the degrees times the sin of the chord.

My aileron for example has a chord of 2.5" and the throw is 18 degrees. 2.5 x sin(18) = .77" Is that correct?

I am not sure how to measure the elevator. It's a full moving type. Would I measure the chord from the pivot point to the trailing edge?
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Old Apr 10, 2014, 04:07 PM
Registered User
United States, CA, Altadena
Joined Sep 2013
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Looks like a good conversion to me.

Pivot to either edge should be the same if they suggest symmetrical throws.
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Old Apr 10, 2014, 05:41 PM
If it flies - I want one!
Petem's Avatar
Werribee, Victoria, Australia
Joined Jul 2008
962 Posts
One in sixty

A good approximation used in pilot navigation is the 'one in sixty' rule:
One mile (inch, mm, whatever) deviation in 60 subtends near enough to one degree - so if chord is 180mm and you want the wing at two degrees, raise the LE by 6mm (180/60 times 2).
For your example: if surface chord is 60mm and angle of deflection 18 degrees, deflection would be around 18mm (~.72"). Your chord is a smidgen more, so your calculation looks about right.
Yes, you would use as chord the distance from hinge line or pivot to where the deflection is measured.
The 1:60 rule becomes less accurate as angles increase, but given that most design measurements are educated guesses anyway, it works well for most practical purposes.
Cheers,
PeteM
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Old Apr 10, 2014, 07:53 PM
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i have a cheater app on my phone for doing triangles
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Old Apr 10, 2014, 11:32 PM
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Joined Sep 2008
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Or you could just print this to the size you want.
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Old Apr 11, 2014, 12:01 AM
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Phoenix AZ USA
Joined Jan 2009
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This thing made all my degree problems easy. It has a zero button. You can set it to any orientation (straight, 90, 142.5, what ever) and hit zero then move it to what you want. So easy.
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Last edited by leaktech; Apr 11, 2014 at 12:07 AM.
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Old Apr 11, 2014, 06:21 AM
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One can pick up a protractor at any place that has school supplies for a buck or two or, as Leadchucker suggests, just print one. I found one that includes a locking swing arm that can be set wherever one wants and it makes a perfect gauge.
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Old Apr 11, 2014, 09:00 AM
Deniable plausibility
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Old Apr 11, 2014, 09:26 AM
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Here is a very cheap and simple device that makes measuring control throws in degrees easy. Since I got it, I go the other way and convert any suggested throws in inches/mm to degrees.

http://www.hobbyking.com/hobbyking/s...row_Gauge.html
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Old Apr 11, 2014, 10:32 AM
Since 1952
Canada, AB, Edmonton
Joined Oct 2004
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To continue this slight drifting off topic, here's another gadget. I bought it more or less on impulse, thinking it would possibly be one of those "solutions looking for a problem" things. But it's turned out to be really useful and very accurate, and I use it all the time for many different things including model airplane setups.
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