stunthanger.com
General control line discussion => Open Forum => Topic started by: keith varley on February 15, 2012, 12:04:54 PM
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It is generally believed, that wheel pants reduce drag on full scale planes, but I wonder just what effect they have at low Reynolds numbers such as are found in our stunters.I will readily concede that they add a lot to the appearance , at the expense of some weight, which would obviously change the verticle C.G. What makes me particularly curious is that Howard Rush (who knows more than most, about these things) was flying a notably beautiful , and well thought out model, for the last couple of years , and it did not have wheel pants , despite the naked look.Anybody have any input here?And Howard---Do you know something that we don't know? Perhaps it's because of flying off grass at Arlington? Keith
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About two weeks before the Nats for each of the last three years, I fiddled with wheel trousers. I never got the paint to stick. That's why I didn't use them. I didn't care about drag with the internal combustion engine. I did do a landing gear drag calculation, thinking it might matter for an electric airplane. In particular, I wanted to see if retracts would reduce battery weight enough to make them worthwhile. For an airplane flying at 15 degrees C at sea level at standard pressure flying 5.5 minutes on 70-foot lines at 5.3 seconds per lap, with total power system efficiency of .63, a pair of 2" wheels .7" wide would use about 1400 Joules of battery energy. For a five-cell LiPo, that's about 21 milliamp-hours. Wheel trousers might save you 15 milliamp-hours, but you'd use some more electricity in induced drag in loops. I think that looking cool is a better reason for wheel trousers than drag reduction, even on electrical airplanes.
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It is generally believed, that wheel pants reduce drag on full scale planes, but I wonder just what effect they have at low Reynolds numbers such as are found in our stunters.I will readily concede that they add a lot to the appearance , at the expense of some weight, which would obviously change the verticle C.G. What makes me particularly curious is that Howard Rush (who knows more than most, about these things) was flying a notably beautiful , and well thought out model, for the last couple of years , and it did not have wheel pants , despite the naked look.Anybody have any input here?And Howard---Do you know something that we don't know? Perhaps it's because of flying off grass at Arlington? Keith
Looks like Howard agrees with you. Wheel pants increase the "It has to be better" thought processes as the judges hand out scores. y1
When I flew CL Stunt, I never used Wheel Pants. As a pilot I found that anything not well aligned with the fuselage of the machine, thus not squared to the wing, would cause drag and trim problems. What few RC planes that I have owned that I used wheel pants on were nothing but maintenance problems from the get-go.
I have a fond memory of the old T-33 in which I went on a number of cross-country flights. We added a clothing-case under the belly and those things were very bent-up. The shackles were very loosely installed. The T-33 did not have any rudder trim, which was strange, as the P-51 proved that such was a very good thing. So those beat-up arrangements created a yawing thing in the T-33. Well we appied light rudder pressure, either way for until that leg was tired, then the other way and so on for an hour or two as we cruised along. A little yaw in one way would hold the case still, same for yawing the other way but YUCK!
So I don't think wheel pants are worth the possible problems they can create, especially if they create an inward yaw which can happen in any flight. OTOH, it's points that the stunt pilot is after so it's the ship's captain that makes those decisions. The SHIP's CAPTAIN is YOU! #^
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Thank you Howard for being so Candid. Keith
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I agree with Howard. It's all about the cool.
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I know nothing about the effects they would have on a plane. I just think they look cool. x:
As to not getting paint to stick to them.... why would that be? Are they carbon fiber, or fiber glass pants?
I did my first set of wheel pants made out of balsa, covered in silk. No paint issue at all.
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Anybody have any input here?
They do catch the grass on a rough field, and that tuning fork type twang you get from fuselage mounted wire under carriage just after lift off definitely hasn't got the 'cool' factor going for it!
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I asked Dave Fitzgerald about this exact topic after seeing his Yellow StarGazer IV which has fuse mounted undercarts which had NO pants attached.
Thinking there was some logical reason behind it, he said quite simply " I was lazy.. "
b1
If we look at the Top 5 at the most recent US NATS.
Dave F - ThunderGazer - Wing mounted fairings
Paul W - Impact XS - Tri mount fairings
Brett Buck - Infinity - Wing Mount Fairing
Derek Barry - Dreadnough - Fuse mounted with Pants
Richard Oliver - Maverick - Wing mounted Fairings.
You have to move down to Bob Hunt in 6th with Wing mounted Pants.
Of course Bruce Perry's Jester had Fuse mounted pants and his was Front row..
I question that : in todays climate of high calibre Judges - if wheel pants on or off are even a consideration to high scores.
I personally prefer them - however long grass is an issue - I usually make 2 sets of undercarts - one with large wheels and plenty of clearance, and ones for tarmac.
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Back in the day, every well dressed man wore "spats", and almost every memorable classic airplane design had them also. Why not now!
Type at you later,
Dan McEntee
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I know of one N30 plane that even has a pant on the tail wheel. Have not seen that on any other model.
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You should always use wheel pants or gear doors if building a semi-scale
that had them. The only exceptions would be an OTS, Classic or N30
model that did not originally have them. The model almost always flies
better with than without and looks a whole lot nicer! I'm just sayin'...RJ
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In fact.. thinking back..
Id find it difficult to remember a model Bob Whitely did without wheel pants..
Certainly the Lasers had them "back in the day".. and todays machine Turbo Raven certainly has an impressive stance with its white / black pants.
I think its becoming a lost art.....
I always strive to blend the leg farings into the pants spending alot of time to get it smooth - I thought I did a great job until I saw that damn Jester from Bruce Perry....... I have a critical eye and I could not detect any difference from Wheel pant to Undercart leg. It was almost like it was pulled from the one mold ( But I know it wasnt.. ) or the pant was recessed in to allow for the legs.
Certainly the best wheel pant job I've ever seen, and I think it went largely unoticed under the veil of the beautiful candy purple paint job.. If you get a chance to look at that section only - its eye opening. :o
That was one reason I voted for it.
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PJ wrote:
I always strive to blend the leg farings into the pants spending alot of time to get it smooth - I thought I did a great job until I saw that damn Jester from Bruce Perry....... I have a critical eye and I could not detect any difference from Wheel pant to Undercart leg. It was almost like it was pulled from the one mold ( But I know it wasnt.. ) or the pant was recessed in to allow for the legs.
Certainly the best wheel pant job I've ever seen, and I think it went largely unoticed under the veil of the beautiful candy purple paint job.. If you get a chance to look at that section only - its eye opening.
Wow!!! thanks for the KIND words PJ!! I appreciate it very much.
B
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Bruce : H^^
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..only if they are aerodynamically "fair" ;->
L.
"If I have not seen as far as others, it is because giants were standing on my shoulders." -Hal Abelson