Dec 06, 2012, 06:51 PM Registered User Joined Nov 2012 3 Posts Help! Aerodynamic forces on swing-wing Question I'm designing and building a Large swing-wing 1/5 scale aircraft and I'm trying to figure out what size actuators or servos to use. The question I have is...what type of forces are affecting the movement of the wing....meaning if I had a 30lb actuator pushing the wing forward while the aircraft is moving at 120mph will this be enough to move the wing? Or will there be additional force on the wing which would translate into more weight for the actuator to push? If I'm not being clear please let me know.
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 Dec 06, 2012, 08:10 PM Apophenia Joined Jan 2007 3,806 Posts That is going to require some analysis. The wing forces are usually resolved into lift (perpendicular to the free stream), drag (parallel to the free stream), and a torque about the wing Mean Aerodynamic Centre (MAC). Depending on the exact situation the wing is usually has an aft force from the drag, but can actually be pulling forward under some circumstances. The force required to sweep the wing will depend on the wing planform, flight attitude, speed, AoA, the mechanical ratios of the MAC to pivot and actuator to pivot distances, and the friction of the pivot under the flight loads. There is no simple way to determine if 30 lbs. is enough. Is that a quoted figure, or the actual dynamic force that is available to move something? There can be a big difference between what the manufacturer's quote, which is usually a holding force or torque, and the dynamic force available to actually move something. If you provide some more details on the wing planform, and how the actuator will be moving the wing, perhaps we could figure out some of the basic forces. I would recommend actually testing the actuator to see how much mass it can lift, to see how much force it actually has. Kevin
 Dec 06, 2012, 08:20 PM Ascended Master Palmdale, CA Joined Oct 2000 13,621 Posts The bending loads on the wing all go through the hinge. That must be a sturdy fixture so it doesn't bind under load.
 Dec 06, 2012, 08:32 PM Registered User Joined Nov 2012 3 Posts The 30lbs is not a quote figure. Obviously I have bitten off a little more than I can chew here. I will obtain an actuator and a servo to see what works best. I have a NASA research center a mile down the road from me...I have been tempted to ask what would it take to use their wind tunnel. This would give me a lot of answers with this design. Thanks for your response.. I will take some pictures once I get the actuator.
Dec 06, 2012, 09:00 PM
Registered User
United States, KS, Andover
Joined Oct 2005
546 Posts
Quote:
 Originally Posted by CFBird I'm designing and building a Large swing-wing 1/5 scale aircraft and I'm trying to figure out what size actuators or servos to use. The question I have is...what type of forces are affecting the movement of the wing....meaning if I had a 30lb actuator pushing the wing forward while the aircraft is moving at 120mph will this be enough to move the wing? Or will there be additional force on the wing which would translate into more weight for the actuator to push? If I'm not being clear please let me know.
Thrust = drag, so you should be able to get some rough idea what proportion of the drag is due to the wing. How much thrust do you get from your propulsion system. From there, approximate the center of drag for each wing and calculate the moment you need to counter with your actuator. These are all approximations. Or, you could go the other way. Given the span of your wing, what would be the drag required to reach the limit of your actuator. Does this drag make sense?

Mark
 Dec 07, 2012, 06:08 AM Registered User United States, UT, Salt Lake City Joined Oct 2007 8,352 Posts I would use a screw type device - motor loads very low . the wing would also hold any position desired The swing wings were really lousy concepts but playing with one could be a lot of fun- the weight of the things was the big stumbling block.
 Dec 07, 2012, 12:34 PM An itch?. Scratch build. South Wales U.K. Joined Mar 2003 14,802 Posts 1/5th scale ? If that's a F-14 Tomcat, that make it around 150+" span, (over 12ft), and doing 120mph. Turbine power ?.
 Dec 07, 2012, 05:38 PM Registered User Joined Oct 2004 3,129 Posts There are roles where a swing wing makes a lot of sense, particularly for low level high speed bombers and fighter-bombers. The list is pretty long here: B-1B Lancer, Tu 22 M, Tu 160, Panavia Tornado, Mig 27, Su-17/-20/-22, Su-24, F111. It's not ideal for pure fighters (F 14 and Mig 23 are the only representatives here, the Tornado ADV was just forced into the role) but it can be advantageous in interceptors operating beyond the visual range. Otherwise, none of these really makes a good dogfighter, but entering a maneuvered fight nowadays means that you already made several mistakes. An 1/5th scale Tornado or Su-17 should be large, but feasible An 1/5th scale Tu 160 would be amazing. And could be fitted with a cockpit. Last edited by Brandano; Dec 07, 2012 at 05:44 PM.
Dec 09, 2012, 08:52 AM
Registered User
United States, CA, San Diego
Joined Jul 2009
386 Posts
Quote:
 Originally Posted by richard hanson The swing wings were really lousy concepts
I must have been wasting my time then.
Dec 09, 2012, 09:07 AM
Registered User
Germany, BW, Stuttgart
Joined Mar 2012
1,050 Posts
Quote:
 Originally Posted by onewire I must have been wasting my time then.
Yep, that about captures it.
Dec 09, 2012, 09:11 AM
Registered User
United States, UT, Salt Lake City
Joined Oct 2007
8,352 Posts
Quote:
 Originally Posted by onewire I must have been wasting my time then.
The planes were not a breakthru - just a attempt to do the job -If they had been a true improvement -the concept would have continued.
There were lots of lousy fighters over the years - typically the result of not having enough power for the job.
so the developers tried to reduce airframe drag to get the speed desired
Unfortunately we still have some lousy planes - grossly overpriced and unreliable - but what do you expect when the the goal is to drive technology (and profit) with an open checkbook.
I don't see any end to it .
 Dec 10, 2012, 01:29 AM Registered User United States, CA, San Diego Joined Jul 2009 386 Posts No one said it was a breakthrough. All airframes are compromises. The Tomcat was built solely as a platform for the Phoenix missile. The sweep (unswept) wings were to reduce air speed for carrier landings (as was the F-111 which McNamara wanted to force on all branches). Anything after was gravy. And the gravy was pretty good. She could definitely reach out and touch someone. Or 6 someones. Last edited by onewire; Dec 10, 2012 at 01:42 AM.

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