Wing tip shape?
12-11-2007 | 01:34 PM
#2
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RE: Wing tip shape?
Of the three, the red, nothing is faster than nothing there at all 
If the wing can be tapered to almost nothing and then flat on the end is even better. I fly Jets exclusively and all the fast ones taper down and are either rounded or squared off. But when you taper, you can afford to have aesthetically pleasing rounding of the wing tip.
Edit: in hindsight, because number two is heavily tapered or thinner than number three, it is faster. But I assumed we were talking shape, and not the actual wing.
If the wing can be tapered to almost nothing and then flat on the end is even better. I fly Jets exclusively and all the fast ones taper down and are either rounded or squared off. But when you taper, you can afford to have aesthetically pleasing rounding of the wing tip.
Edit: in hindsight, because number two is heavily tapered or thinner than number three, it is faster. But I assumed we were talking shape, and not the actual wing.
12-11-2007 | 01:39 PM
#3
Senior Member
RE: Wing tip shape?
Randy,
This may not be an option on your plane,
but take a close look at the wingtip of the F-14 Tomcat,
It's "raked" so that the wing's trailing edge is slightly
longer than the leading edge. The tip is a slightly arced
line from LE to TE. This shape results in the lowest drag
at subsonic speeds. I agree with Sean, "Of the three, the red"
should be the fastest.
Regards
JC
[link=http://www.topedge.com/panels/aircraft/sites/vf11/f-14size.gif]www.topedge.com[/link]
http://www.topedge.com/panels/aircra...1/f-14size.gif
This may not be an option on your plane,
but take a close look at the wingtip of the F-14 Tomcat,
It's "raked" so that the wing's trailing edge is slightly
longer than the leading edge. The tip is a slightly arced
line from LE to TE. This shape results in the lowest drag
at subsonic speeds. I agree with Sean, "Of the three, the red"
should be the fastest.
Regards
JC
[link=http://www.topedge.com/panels/aircraft/sites/vf11/f-14size.gif]www.topedge.com[/link]
http://www.topedge.com/panels/aircra...1/f-14size.gif
12-11-2007 | 09:01 PM
#7
My Feedback: (60)
RE: Wing tip shape?
Again, think of it in terms of what's "not there" is not drag. Look at all the fastest ships on the planet, what do their wing tips look like? High taper, no or little rounded tips. A good example of just a straight flat is this: http://www.aerospaceweb.org/aircraft/research/x15/
The smaller your wing area, the faster you are going to need to be going to create enough lift to stay in the air. I custom build a turbine F-20, and without it's wingrockets, it is a straight edged flat tip:
http://www.fas.org/man/dod-101/sys/ac/f-20_3view.gif
The smaller your wing area, the faster you are going to need to be going to create enough lift to stay in the air. I custom build a turbine F-20, and without it's wingrockets, it is a straight edged flat tip:
http://www.fas.org/man/dod-101/sys/ac/f-20_3view.gif
12-12-2007 | 08:35 AM
#8
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From: Mt. Pleasant,
OH
RE: Wing tip shape?
Waiiiiit a minute....is this another "Airplane on a Treadmill" question? "Fastest at 180 mph"? Aren't they all going the same speed at 180 mph?
Just being a wiseguy, lol
Just being a wiseguy, lol
12-12-2007 | 03:49 PM
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From: Bloomington, MN,
RE: Wing tip shape?
Randy,
At that speed, I'm assuming you would be on the straight, so induced drag is negligible. Under those conditions, you want a smooth, rounded tip, with no sharp edges and nothing squared off. There is no need to try to influence the tip vortex, you just want to avoid any sharp edges that could result in flow separation.
banktoturn
12-12-2007 | 05:38 PM
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From: Bloomington, MN,
RE: Wing tip shape?
js3,
Good point. I took Randy's question to refer to the straight, but the best overall choice for pylon racing might need to account for induced drag in turns. I don't have data on the effectiveness of different tip shapes for induced drag reduction, but I tend to be a little skeptical of some of the claims I have seen. Winglets, if they are allowed, would be promising, but I don't know about other shapes, such as Hoerner tips.
If you really want to reduce induced drag, the tip shape is not the place to look.
banktoturn
Good point. I took Randy's question to refer to the straight, but the best overall choice for pylon racing might need to account for induced drag in turns. I don't have data on the effectiveness of different tip shapes for induced drag reduction, but I tend to be a little skeptical of some of the claims I have seen. Winglets, if they are allowed, would be promising, but I don't know about other shapes, such as Hoerner tips.
If you really want to reduce induced drag, the tip shape is not the place to look.
banktoturn
12-12-2007 | 05:54 PM
#12
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From: Shakopee,
MN
RE: Wing tip shape?
In a Q-500 pylon race the wing is at 90 degrees in turn one and 45 degrees the rest of the time. Only time straight is on take off. Race has 30 turns and 20 straight of 600 feet. Ten laps is 2 1/2 miles, record time is around 60 seconds.
12-12-2007 | 06:58 PM
#13
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RE: Wing tip shape?
If you really want to reduce induced drag, the tip shape is not the place to look.
In a Q-500 pylon race the wing is at 90 degrees in turn one and 45 degrees the rest of the time. Only time straight is on take off. Race has 30 turns and 20 straight of 600 feet. Ten laps is 2 1/2 miles
The so called "straight flight" which ties together the turns at both ends is also a turn (at a 45 degree bank) where the airplane would be doing roughly 1.4g to hold altitude. Since a 45 degree bank results in a turn with a radius of about 1950 at 170 mph. Depending on turn radius at pylon 1, the "straights" distance is only about 530 feet. However the bank of 45 degrees results in too short of distance by about 50 feet. So the bank needs to be slightly less (assuming calm conditions), about 42 degrees. On windy days (wind from pylon one) the bank from turn three to one is even less, while from one to two is greater due to variations in ground speed.
OK, nobody can fly that course perfectly and the difference in bank of a few degrees is very minor. But the reason you want to fly a course with 39 turns is that you can lower the amount of time spent in the high g turns at Pylon 1 and Pylons 2/3 by about 8%, which results in faster overall times.
12-12-2007 | 11:58 PM
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From: Bloomington, MN,
RE: Wing tip shape?
Randy,
I can't make out all the details of the three wingtips very well. My answer is that the tip with the fewest sharp lines & sharp radii. It looks to me like #1 fits that bill.
banktoturn
12-13-2007 | 12:18 AM
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From: Bloomington, MN,
RE: Wing tip shape?
Why do you want the maximum span at the trailing edge? Does this reduce induced drag?
By "straight", I mean the portions of the flight when the plane is not in a tight turn. Only during a tight turn is the coefficient of lift high enough to make induced drag a concern.
banktoturn
ORIGINAL: HighPlains
I have to disagree. You want the maximum span of the wing at the trailing edge.
I just not going to agree with any of this either. All the tight turns (making the turn at 2/3 as one turn) approach 90 degrees if one maintains altitude through the turn.
The so called "straight flight" which ties together the turns at both ends is also a turn (at a 45 degree bank) where the airplane would be doing roughly 1.4g to hold altitude. Since a 45 degree bank results in a turn with a radius of about 1950 at 170 mph. Depending on turn radius at pylon 1, the "straights" distance is only about 530 feet. However the bank of 45 degrees results in too short of distance by about 50 feet. So the bank needs to be slightly less (assuming calm conditions), about 42 degrees. On windy days (wind from pylon one) the bank from turn three to one is even less, while from one to two is greater due to variations in ground speed.
OK, nobody can fly that course perfectly and the difference in bank of a few degrees is very minor. But the reason you want to fly a course with 39 turns is that you can lower the amount of time spent in the high g turns at Pylon 1 and Pylons 2/3 by about 8%, which results in faster overall times.
If you really want to reduce induced drag, the tip shape is not the place to look.
In a Q-500 pylon race the wing is at 90 degrees in turn one and 45 degrees the rest of the time. Only time straight is on take off. Race has 30 turns and 20 straight of 600 feet. Ten laps is 2 1/2 miles
The so called "straight flight" which ties together the turns at both ends is also a turn (at a 45 degree bank) where the airplane would be doing roughly 1.4g to hold altitude. Since a 45 degree bank results in a turn with a radius of about 1950 at 170 mph. Depending on turn radius at pylon 1, the "straights" distance is only about 530 feet. However the bank of 45 degrees results in too short of distance by about 50 feet. So the bank needs to be slightly less (assuming calm conditions), about 42 degrees. On windy days (wind from pylon one) the bank from turn three to one is even less, while from one to two is greater due to variations in ground speed.
OK, nobody can fly that course perfectly and the difference in bank of a few degrees is very minor. But the reason you want to fly a course with 39 turns is that you can lower the amount of time spent in the high g turns at Pylon 1 and Pylons 2/3 by about 8%, which results in faster overall times.
12-13-2007 | 08:39 AM
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From: Oakville,
ON, CANADA
RE: Wing tip shape?
Hi Randy,
I say #3, on the right.
-it is the shineyest of the three !
-the slight diahedral effect is more stable in high G turns.
-the shape promotes even tip vortexes, rather than the extra drag of trying to fight the vortexes.
Just my humble opinion.
Take care,
Have fun,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
I say #3, on the right.
-it is the shineyest of the three !
-the slight diahedral effect is more stable in high G turns.
-the shape promotes even tip vortexes, rather than the extra drag of trying to fight the vortexes.
Just my humble opinion.
Take care,
Have fun,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
12-13-2007 | 11:50 AM
#18
RE: Wing tip shape?
I've been thinking about this a lot lately, and have done some looking around in the Reno racers (unlimited ) pics...
I like the tips on Dago Red...they have an up-turned sort of a mini winglet style.
http://www.pbase.com/wjpearce/dago03
Another view of the same type of tip.
http://www.pbase.com/wjpearce/image/26124640
#3 looks like it'd be the lowest drag?
I like the tips on Dago Red...they have an up-turned sort of a mini winglet style.
http://www.pbase.com/wjpearce/dago03
Another view of the same type of tip.
http://www.pbase.com/wjpearce/image/26124640
#3 looks like it'd be the lowest drag?
12-13-2007 | 01:18 PM
#19
My Feedback: (1)
RE: Wing tip shape?
Maximum span reduces the induced drag in the high g turns. When a wingtip curves back in towards the fuselage, it makes the wing appear to have the reduced span of where the wingtip meets the trailing edge.
But hey, with so many thinking wingtip shape has no effect, do as you please. It's all in the engine anyway.
For myself, I rather like parabolic functions.
But hey, with so many thinking wingtip shape has no effect, do as you please. It's all in the engine anyway.
For myself, I rather like parabolic functions.
12-14-2007 | 12:46 AM
#20
RE: Wing tip shape?
I would think that the second one would have the least about of drag at 180mph. Although I wonder about the winglet type of shape might be a more interesting route to pursue in the long run for high speed or drag reduction. One of the guys in the high speed forum has built a high speed airplane with winglets that looks very interesting. I wonder if you were to go with a very thin tapered airfoil if that might work.
12-15-2007 | 12:53 AM
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From: Waseca,
MN
RE: Wing tip shape?
He can not taper or go thinner with the airfoil.
The rules are pretty clear.
48" constand chord, minimum 1 3/16" thick at the high point.
Maximum wing length 52", minimum 500 square inches.
To me, I've always thought that the optimum tip would be 52" at the trailing edge and 48 " at the LE and whatever chord width it takes to give you 500 squares. Then taper the tip as sharp as possible outside of the 48".
The rules are pretty clear.
48" constand chord, minimum 1 3/16" thick at the high point.
Maximum wing length 52", minimum 500 square inches.
To me, I've always thought that the optimum tip would be 52" at the trailing edge and 48 " at the LE and whatever chord width it takes to give you 500 squares. Then taper the tip as sharp as possible outside of the 48".
12-15-2007 | 06:25 AM
#23
Senior Member
RE: Wing tip shape?
ORIGINAL: HighPlains
I've always wondered why people don't read the rules every once in an while. Dave???
I've always wondered why people don't read the rules every once in an while. Dave???
The teams that win races often read the rules every day or so...........
12-15-2007 | 03:03 PM
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RE: Wing tip shape?
Going w/ a sharp edge along the tip is best for low drag. Your second tip looks to be sharp on the "leading edge" part of the tip. The term "leading edge" here means that part that sees the onset flow. That part should not be sharp. The sharp part should only be the "trailing edge" where the flow is leaving the wing, i.e. the part of the tip where the flow is rolling up into the tip vortex. The sharp "trailing edge" will reduced induced drag when pulling high g's. It does not hurt when flying straight. (The book by Hoerner shows the benefits of a sharp trailing edge.)
Michael
Michael
12-15-2007 | 08:18 PM
#25
RE: Wing tip shape?
Michael,
Thanks for taking the time to post on this question.
If I understand this right what you are saying is that the old "raindrop" concept is still the best overall model for reduced drag.
Thanks for taking the time to post on this question.
If I understand this right what you are saying is that the old "raindrop" concept is still the best overall model for reduced drag.
