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Larry Ruble
13 Posts |
 Posted - 12/03/2003 : 2:12:05 PM
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What are to pros and cons between the MH32 and Aegea airfoils? I was told the MH32 would range very well, but sacrifice some thermalling ability. I would appreciate some feedback from those who have flight time on the 3 meter mantis.
Larry |
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Anker
83 Posts |
Posted - 12/03/2003 : 6:33:03 PM
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I do not have a direct airfoil comparison because the Aegea wing is longer and gains some efficiency from that. I very much prefer my Aegea Manti to my MH32 Mantis. The Aegea penetrates much better and ranges much further.
Anker |
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Jack Hyde
8 Posts |
Posted - 12/03/2003 : 8:03:25 PM
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I was working on the MH32 Mantis vs Aegea comparison today. I have one of each and fly them one after the other to see which seems better to me. Today the Aegea won . A week ago I was about convinced the MH32 Mantis was a better all around plane. I have been flying the Mantis for a few years and the Aegea a few months. I like them both and could be happy with either.
I ordered some 1/2" AL tubing to make a pair of 10 deg wing rods to try a little more dihedral in the Aegea wing.
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Fritz
19 Posts |
Posted - 01/15/2004 : 5:03:26 PM
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I've been flying both for the last season and a half. Unfortunately, its comparing apples to oranges, as the Aegea is 130", giving it a better glide and somewhat less maneuverablility. Since its -2° outside, and I can't fly in 40 knot winds with -40° wind-chill, I decided to do an apples to apples comparison on Xfoil. The first figure is the comparison of the 2 airfoils when the AG40-2 has the flap set back to zero and DEROtated in GDES.
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Note that the 2 airfoils are quite similar except that the AG-40 (red) is thinner.
We then compare the polars for the two, assuming a 1060 square inch wing on a plane weighing 68 oz.
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The polars are very similar, indicating that the they have about the same camber, and the glide ratio for the AG40 should be slightly better, because it is a thinner airfoil. What is noticable, though, is that the lift-to-angle slope is steeper. This gives it a crisper feel in the air, that I have been noticing.
Both airfoils can be reflexed. The MH-32 Mantis has a flap line at 80% and the AG40 has it at 75%. I ran the negative 2 flap setting which is shown in the next figure.
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Both airfoils lose a little lift and gain speed. Pretty comparable airfoils, depending on how well they are made.
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Edited by - Fritz on 01/15/2004 9:23:01 PM |
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drela@mit.edu
12 Posts |
Posted - 01/16/2004 : 7:48:17 PM
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The Aegea's center AG40d airfoil is very similar to the MH32 as Fritz pointed out. Bigger differences appear as you go outboard. The AG41d,42d,43d are geared for the progressively smaller Reynolds number and perform reasonably well, while the MH32 rapidly falls apart. Try comparing the AG42d with the MH32 at 65K, and you'll see what I mean.
Mark Drela |
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Fritz
19 Posts |
Posted - 01/19/2004 : 12:35:04 PM
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Mark is of course right. I also made the Reynolds number 95000 based on the mean chord (area/span) whereas the reall Reynolds number correspond to each section.
Here are the comparisons of the entire series of airfoils Mark designed into the Aegea wing:
What I don't know how to handle, in using Re(sqrtCL) is to account for wing twist and effective angle of attack -Mark?
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The root Reynolds number based on CL=1 is 116,694 using the 1976 US Standard atmosphere at sea level. For you engineers, your exercise is to correct for humidity, pressure, and altitude.
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The AG-41 is at the first break, and has a 9" chord.
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Here is how the AG-42 compares with the MH-32, at the 7" chord. I did not correct the RE(sqrtCL) for the wing-twist. Note that the wingtwist makes the airfoil fly faster before the CL is needed to support the airplane. In other words, the center is doing more of the heavy lifting.
Finally, for completeness,
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The tip goes along for the ride, too.
Now is to play with the fact that I pivoted the flap at the top surface for the AG42 and AG43, copying how Phil built the wing. I want to pivot from the bottom and see if there is any noticeable effect. Then I want to explore all the different flap settings... I wish the weather would warm up so I could get more than 45 minutes of flying in!
-Fritz
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Edited by - Fritz on 01/20/2004 08:25:38 AM |
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jon stone
12 Posts |
Posted - 01/19/2004 : 5:57:59 PM
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Fritz,
Some of your charts show 0 degrees reflex, some show -2. Others are unlabeled .dat files. I am not sure, from the charts, which airfoils are being compared.
Should not reflexed AG's should be compared with reflex MH32's, etc.
Jon
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Fritz
19 Posts |
Posted - 01/19/2004 : 6:45:26 PM
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Hi Jon,
Thanks for catching that. All of the AG series airfoils were set to 0 degrees flap and derotated to line up the trailing edges. The curves are right, I forgot to change the labelling when took each batch and converted the postscript into .GIF format.
-Fritz |
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jwjsailplane
22 Posts |
Posted - 01/20/2004 : 8:36:00 PM
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| Ok. I think I see where the AG 43 has advantage but don't we fly at alphas at 2-3 and CL around 0.5 -0.6? If you lokk at the curves around those values it seems like the dust, dings, errors in mfgr. or paint might make more difference than the original airfoil. Furthermore and the human pilot discern 2-5% difference? I guess that's why I'm a sportsman at heart. |
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drela@mit.edu
12 Posts |
Posted - 01/21/2004 : 10:13:34 PM
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quote:
Originally posted by jwjenks
Ok. I think I see where the AG 43 has advantage but don't we fly at alphas at 2-3 and CL around 0.5 -0.6?
Here are the numbers for an 8 oz/ft^2 loading:
CL mph
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0.8 15.6 (min sink)
0.6 18.0
0.2 30.0
At CL=0.6 you're almost standing still into a 15 mph breeze. I think impatient upwind runs are done at around 30 mph, or CL=0.2 or so.
One of the design goals of the AG series was very low CD at such low CL's. That's what gives you good upwind legs.
Mark Drela |
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Aegea vs MH32 airfoil
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