HobbyKing.com New Products Flash Sale
Thread Tools
Old Apr 10, 2014, 02:45 PM
Sailplane Mafia
gquiring's Avatar
United States, SC, Summerville
Joined Jun 2001
2,020 Posts
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?
gquiring is offline Find More Posts by gquiring
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 10, 2014, 04:07 PM
Registered User
United States, CA, Altadena
Joined Sep 2013
87 Posts
Looks like a good conversion to me.

Pivot to either edge should be the same if they suggest symmetrical throws.
Pretext is online now Find More Posts by Pretext
Reply With Quote
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.
Petem is offline Find More Posts by Petem
Reply With Quote
Old Apr 10, 2014, 07:53 PM
derk's Avatar
USA, ID, Coeur D'Alene
Joined Dec 2003
5,406 Posts
i have a cheater app on my phone for doing triangles
derk is online now Find More Posts by derk
Reply With Quote
Old Apr 10, 2014, 11:32 PM
Thermal Junkie
Leadchucker's Avatar
Joined Sep 2008
3,214 Posts
Or you could just print this to the size you want.
Leadchucker is offline Find More Posts by Leadchucker
RCG Plus Member
Latest blog entry: Mini update on Kennedy Longhorn
Reply With Quote
Old Apr 11, 2014, 12:01 AM
Balsa + glue + bluesky= fun
leaktech's Avatar
Phoenix AZ USA
Joined Jan 2009
815 Posts
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.
leaktech is offline Find More Posts by leaktech
Last edited by leaktech; Apr 11, 2014 at 12:07 AM.
Reply With Quote
Old Apr 11, 2014, 06:21 AM
Registered User
Joined Apr 2012
2,208 Posts
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.
peterlngh is online now Find More Posts by peterlngh
Reply With Quote
Old Apr 11, 2014, 09:00 AM
Deniable plausibility
Shedofdread's Avatar
Derbyshire, UK
Joined Aug 2008
2,307 Posts
Some Old Hangers Can Almost Hold Ten Old Aeroplanes...
Shedofdread is offline Find More Posts by Shedofdread
Reply With Quote
Old Apr 11, 2014, 09:26 AM
Registered User
Joined Mar 2013
7 Posts
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.

Canno is online now Find More Posts by Canno
Reply With Quote
Old Apr 11, 2014, 10:32 AM
Since 1952
Canada, AB, Edmonton
Joined Oct 2004
1,191 Posts
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.
Harry D is offline Find More Posts by Harry D
Reply With Quote

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Good 7 or 8 Inch FPV Monitor - Help BalsaBob FPV Equipment 1 Nov 19, 2013 11:12 PM
Discussion Help with Westerner 85 inch free flight conversion to rc aircrew53 Vintage & Old-Timer Designs 22 Oct 28, 2013 05:00 PM
Discussion 90 degr angled pitot tube aeropics Flight Accessories 0 Jul 30, 2011 11:19 AM
For Sale 4#6 Complete 45 degr & 90 degree BELL rotor heads Main shaft NIP blades &training blueindian Aircraft - Electric - Helis (FS/W) 1 Feb 03, 2011 02:05 PM
Discussion 180 degre Towerpro SG90 mod newbieflyer Radios 2 Sep 13, 2009 02:50 PM