autoreply
Well-Known Member
All those airfoils are very old and, sensitive to microturbulence. Modern laminar airfoils are much better, especially in a real-life environment.
NLF 0414(f) on a lancair
- Thread starter gschuld
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Mac790
Well-Known Member
Check out also cm for those foils, really high, might work good for sailplanes with long tails (I don't need to explain why), you might try to reduce camber, but like Jarno said try more modern one, ideally with lower camber.
Seb
Seb
topspeed100
Banned
What is wrong with GAW-1 and GAW-2 ?
GAW2 has leading edge radius more than NFL0414 and less camber than many. http://www.worldofkrauss.com/foils/1546
How about GA40A415 ( root ) and GA40A412 ( tip ) ? Looks good.
Then these two;
GAW2 has leading edge radius more than NFL0414 and less camber than many. http://www.worldofkrauss.com/foils/1546
How about GA40A415 ( root ) and GA40A412 ( tip ) ? Looks good.
Then these two;
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autoreply
Well-Known Member
I don't know anything about it, except it being designed for high speed (M=0.7). It does look "modern", but whether it's suitable; not the slightest clue. I can't find a plane that has flown it. For me that forces caution, since there's much more on a profile than Clmax and low drag alone.
topspeed100
Banned
I looked it up in profili 2 and only KC-135 foil had 60% similarity...fast for sure.
Mac790
Well-Known Member
If you really think about NLF airfoils probably the best idea would be NLF414F, this airfoil was used successfully on a couple of planes, so I would hazard to say it's proven airfoil, the only problem about it is rather high cm, decambering might be a solution, give a call to Harry.
Just a few papers about NLF family.
http://www.n91cz.com/Interesting_Technical_Reports/NASA-81-tp1865.pdf
http://hondajet.honda.com/pdf/tech_papers/Journal_of_Aircraft_Vol40_No4_P609_P615_SHM_1_NLF.pdf
here papers about mentioned by you 213
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900003224_1990003224.pdf
http://repository.lib.ncsu.edu/ir/bitstream/1840.16/1805/1/etd.pdf
links for more different papers
NASA Technical Paper 1865 – Design and testing of the NLF(1)-215F air foil used on the Lancair 360
this sounds also interesting
It's a pity that Harry didn't put coordinates for modified NLF series in his book.Craig Catto said:
By ours Orion Airfoil Selectiontopspeed100 said:
and here
http://www.homebuiltairplanes.com/forums/aircraft-design-aerodynamics-new-technology/2391-pusher-prop-mini-imp.html#post14364
Seb
edit, on the page 125 in GA Airfoils, there is a Harry's response to the NLF 0115, it's called GA42E, I'll put tomorrow coordinates into XFLR and take a "closer" look at it.
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Mac790
Well-Known Member
Two more
DU84-132V3 (ASH-25) and HQ-17/14.38 (both measured), it might be necessary to invert coordinates should be from 1-0, and from 0-1.
Seb
DU84-132V3 (ASH-25) and HQ-17/14.38 (both measured), it might be necessary to invert coordinates should be from 1-0, and from 0-1.
Seb
topspeed100
Banned
Thanks Seb for the links.
Molton did not have a GAW but it makes no difference.
Orion seems to be the MAN in this wing foil area and I thank him for that input.
I recall a pilot complained his bede 5B cannot go faster since the GAW-1 runs outa properties beyond 300 mph ( he had a huge engine on that Bede 5 ). I also think the GAW-2 in PIK-26 ( 35 hp ) is an overkill..more laid back foil could have worked out better.
Looks like the Cessna 525/526 Citation Jet uses a modified version of it. I have no idea what the mod was. The Bear Jet was supposed to use it. I can't find any info on it though in fact I'm not even sure there is a prototype yet. John McGinnis on the EAA365 forums likes it, he says he's flown a 1/4 scale model which "flew as predicted" and plans to use it on the full scale of whatever it is he's building. But you're correct in that this foil has not been used extensively. What attracted me to it was it's high L/D at my target Cl and low moment coefficient.
orion
Well-Known Member
Interesting - i just checked Dave Lednicer's site on airfoil usage and it list the Mini-Imp having a GA(PC)-1. The reason I recall the plane having the GAW-1 was because it was defined as such on one of the fabrication drawings that I saw at Molt's shop. I brought up the choice at one point during one of my visits and I made an unguarded comment about a possibly better section. It was the only argument Molt and I had (I've been told that's rare - most folks seemed to have many more).
Regarding the BD-5B, I think the sections on both wings used the 64-xxx section. On the original "A" wings it used a 64-212 at the root and a 64-218 at the tip. Since they had to match the other structure and tooling, the longer "B" wings used the same I thought. A friend of mine flies the BD-5J (used to fly in Pepsi colors, now flies for the Navy pretending to be a cruise missile) and I seem to recall his wings are the 64-xxx series (I helped him rebuild and reinstall them).
BTW, a BD-5 at 300 mph? Scary.
Both "A" and "B" wings actually used the the same ribs, just spaced further apart on the "B". The jets had their own 17ft "G" wing, a GA(W)-1 airfoil IIRC.
Correction - The jet did use the same ribs with the 17ft wing. Got confused with the "D" model that was to use the GA(W)-2
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in my opinion the nlf 0414f is a good replacement. its way better than the nlf 0215f. so is the 747a315. some people would suggest just to use clark y or usa 35b then clean up the rest of the plane. might as well use a box section with a rounded nose and a fairing at the trailing edge. the sc(2) supercritical sections are almost like that and they are not as demanding to make and has lower pitching moment than the ls and ms supercriticals.
the nlf 0414 is a different animal from the other nlf's and naca laminars. its not as sensitive to dirt, has lower pitching moment and has a wider drag bucket. and the drag is lower even when in turbulent flow like what happens when its not made precisely enough or dirty.
the cruise flap was designed so the drag bucket can be moved up or down the cl range. is it better to fix it at a certain angle, than design the wing to have that specific pressure gradient at the trailing edge? who can do that? at least you got one well studied airfoil with a drag bucket that can be tailored easily.
orion
Well-Known Member
Designing a wing for competition is of course different than for normal, everyday use. First, you must identify what sort of competition you're looking to partake in. If you're looking to compete on a closed course such as in pylon racing, that would pose a different set of design requirements than a straight, cross country application. In a pylon race you're typically spending a substantial percentage of the flight in a turn so there you're optimizing for a higher G load than when optimizing for level cruise. As such, let's look at some guidelines:
1) In any competition it's the little things that will add up to penalties. One of these is the wing's moment coefficient and thus the plane's trim drag. In picking the section you really want to minimize the moment - remember that the sections such as those of the NLF family were designed for much higher wing loading that what we see in GA so the accompanying moment they represent would not be good for application here. Realistically you'd like to keep the moment coefficient somewhere in the -.05 range, with some variation accounting for differences in the camber line. The aft loaded sections such as the NLF(1)-0215 will be characterized by fairly high moment coefficients, which in my opinion would take them out of the running fairly early on in the selection process. For instance, the -0215 section is characterized by a cm.ac of -.15 in the range of cruise lift coefficient values. It is interesting that the higher camber variant of the same family (-0415) for the same conditions has a lower moment coefficient - about -.11.
2) The NLF(1)-0215 section does have data for a reflexed flap condition however the moment is still fairly high - in the range of -.06 to -.08. The problem though is that when you reflex the flap you shift the lift cure slope but the drag stays fairly consistent. Translated, this means that at cruise (flap reflexed up) the section's l/d actually slightly decreases, but the trim drag goes down too. As such, whether the section is a good candidate would have to be analyzed much more closely than we can do here. The data for these sections can be found in NASA Technical papers #1861 and #1865.
3) For pylon racing you'd need to consider the higher loading and select a section with more camber - the aforementioned 747A315 or the 747A415 might be good candidates, as would several of the NACA laminar sections with similar camber lines, or possibly the similar shaped Riblett foils. All those are characterized by lower moment coefficients: -.02 for the 747A315 and -.03 for the 747A415. The more commonly used 65-415 has a cm.ac of -.055 and the Riblett 37A415 has a coefficient of -.065. Any of these would probably be better than the NLF series.
4) For high speed cruise you really need less camber however the moment coefficient discussion still applies. But here the choice needs to be coupled with an examination of low cl l/d characteristics. Picking a lift coefficient of .1 (arbitrary for this discussion), the NLF sections don't fare all that well with typical values ranging from about 13.5:1 for the -0215 to 15.8:1 for the -0416. The 64-415 is about 19.2:1; the Riblett GA37-315 is 18.2. (Sorry, don't have all the section information readily at hand to get the low camber values)
In short, yes you can make some quick evaluations but for the actual design process, a much closer look is required.
1) In any competition it's the little things that will add up to penalties. One of these is the wing's moment coefficient and thus the plane's trim drag. In picking the section you really want to minimize the moment - remember that the sections such as those of the NLF family were designed for much higher wing loading that what we see in GA so the accompanying moment they represent would not be good for application here. Realistically you'd like to keep the moment coefficient somewhere in the -.05 range, with some variation accounting for differences in the camber line. The aft loaded sections such as the NLF(1)-0215 will be characterized by fairly high moment coefficients, which in my opinion would take them out of the running fairly early on in the selection process. For instance, the -0215 section is characterized by a cm.ac of -.15 in the range of cruise lift coefficient values. It is interesting that the higher camber variant of the same family (-0415) for the same conditions has a lower moment coefficient - about -.11.
2) The NLF(1)-0215 section does have data for a reflexed flap condition however the moment is still fairly high - in the range of -.06 to -.08. The problem though is that when you reflex the flap you shift the lift cure slope but the drag stays fairly consistent. Translated, this means that at cruise (flap reflexed up) the section's l/d actually slightly decreases, but the trim drag goes down too. As such, whether the section is a good candidate would have to be analyzed much more closely than we can do here. The data for these sections can be found in NASA Technical papers #1861 and #1865.
3) For pylon racing you'd need to consider the higher loading and select a section with more camber - the aforementioned 747A315 or the 747A415 might be good candidates, as would several of the NACA laminar sections with similar camber lines, or possibly the similar shaped Riblett foils. All those are characterized by lower moment coefficients: -.02 for the 747A315 and -.03 for the 747A415. The more commonly used 65-415 has a cm.ac of -.055 and the Riblett 37A415 has a coefficient of -.065. Any of these would probably be better than the NLF series.
4) For high speed cruise you really need less camber however the moment coefficient discussion still applies. But here the choice needs to be coupled with an examination of low cl l/d characteristics. Picking a lift coefficient of .1 (arbitrary for this discussion), the NLF sections don't fare all that well with typical values ranging from about 13.5:1 for the -0215 to 15.8:1 for the -0416. The 64-415 is about 19.2:1; the Riblett GA37-315 is 18.2. (Sorry, don't have all the section information readily at hand to get the low camber values)
In short, yes you can make some quick evaluations but for the actual design process, a much closer look is required.
gschuld
Well-Known Member
It's great that this thread has started up again. I started it with the intention of getting people talking about higher speed airfoils for fairly lightweight planes(under 1400lbs gross).
To be fair, the premise of this particular thread(picking a new airfoil for a Lancair 200) was completely hypothetical. I fully realize that altering an airfoil choice is not to be taken lightly, and must be tailored specifically to each plane and its specific needs. That being said, I am really enjoying the opportunity to learn from the skilled individuals around here, especially Orion!
FWIW, airfoils more suited for high speed cross country type flying (such as for Sport Air Racing League cross country style races, the Fuelventure race, etc.) interest me far more than Reno style pylon racing.
George
To be fair, the premise of this particular thread(picking a new airfoil for a Lancair 200) was completely hypothetical. I fully realize that altering an airfoil choice is not to be taken lightly, and must be tailored specifically to each plane and its specific needs. That being said, I am really enjoying the opportunity to learn from the skilled individuals around here, especially Orion!
FWIW, airfoils more suited for high speed cross country type flying (such as for Sport Air Racing League cross country style races, the Fuelventure race, etc.) interest me far more than Reno style pylon racing.
George
IIRC the GAW airfoils were designed for mach .2 or mach .3...
i think these high cm airfoils were meant to be used with some twist.
N91CZ
Member
Here is report showing the impact of reflexing the NLF-0215 on total aircraft drag. http://n91cz.com/Performance/Cruise_Flap_Report.pdf
gschuld
Well-Known Member
Chris, nice to have your input. I am well aware of your n91cz.com site (read all of it) and your great efforts regarding the efficiency improvements you have researched and performed on your Lancair. I'd like to thank you personally for being so open with your efforts and sharing the results with the world. Some day I hope to meet you in person and be able to show you the results of my efforts. After all, your work and the work of people like you are an inspiration to me. -George
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