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Q-40 Racing Discuss AMA 422 and any other variants of Quarter 40 racing

Q-40 Airfoil selection

Old 11-12-2009, 07:39 PM
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Default Q-40 Airfoil selection

Hey guys, what are the popular airfoils in the modern world of Q40? I am looking into a new design, but I have no idea of what airfoils are the hot ticket. I would like to know what the Dago Red, Vendetta, Polecat, Sweet-V and others use if anyone knows.

I have looked at the MH, Eppler and Selig airfoils, but really need some help with selection. I am looking at a mid-wing format, with a fair amount of taper. Of course the weight, span and area are pretty much spelled out in the rules, so that portion is already decided for me.

If anyone has any information, I am all ears!!

Thanks for the help...
Old 11-12-2009, 08:00 PM
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Default RE: Q-40 Airfoil selection

Yea Scott, I have a great idea for your Q-40 wing......

Get a wing from one of the competitors. Trace it out on a nice strong piece of 3/4 inch plywood.. Then do some sanding and finishing..Then paint with Krylon....

Cut out the ailerons as you like...Use huge servos...!! Then bolt it to your fuselage with 2 inch lag bolts.

It might not be fast, but it will be sturdy and long lasting....

Phil
Old 11-13-2009, 08:03 AM
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Default RE: Q-40 Airfoil selection

Ha Ha Phil, that would be like you to use 3/4" plywood (since the minimum legal thickness is 7/8" ) !! This is not like designing a quickie, the approval process is a little tougher and I can't be modifying the airfoils after it is approved. So, I want to get it right the first time.

I have been applying the CL numbers from the design data, so I know what parameters I need for lift for the entire flight envelope. I just want to see what others use and what works. I am leaning toward a style of airfoil that you would use in a traditional mid-wing design, but I am curious how others approached this. I am not asking for any trade secrets!! Some of the newer MH airfoil numbers look pretty interesting...
Old 11-13-2009, 05:25 PM
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Default RE: Q-40 Airfoil selection

Scott,
The approval process isn't quite that tight. They don't approve the airfoils and you can make changes to them later. What you can't do without re-approval is change the outline or other items they check (fuse cross section, canopy radius, ect).
Old 11-13-2009, 06:12 PM
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Default RE: Q-40 Airfoil selection

Thanks for that Gary, I will keep that in mind. I was concerned that if I modified the airfoil, it would change the cross sectional shape of the fuselage where it fillets to the wing, therefor changing the fuselage cross section in the wing mounting area. Am I being too narrow minded in my approach? I know the change would be minimal, but I don't want to break the rules with a new design! I am assuming by changing the fuselage cross section, you mean the sectional "hoop" you send in for approval? I have spoken to Jim Allen and sent in some preliminary information, and he sent me the approval process documents and such. I am almost ready to send in my final design for review, I guess I am just being too cautious!

You don't know of any of the airfoil types being used currently, do you?

Thanks again,
Old 11-13-2009, 10:21 PM
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Default RE: Q-40 Airfoil selection

As far as the cross section (yes, the hoop), the fillets don't count for the area, so any slight changes to them to fit a different airfoil won't effect the approval. As far as airfoils, I think the the Polecat and Loki use an MH24, but not 100% sure. Lyle's planes use various NACA based airfoils. Not sure what the Sweet V or 2 Sweet use.
Old 11-15-2009, 08:48 PM
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Default RE: Q-40 Airfoil selection

As far as I know:

Miss Ashley II .- SD6060
LOKI, POLECAT, GR-7.- MH24
Larson Vendetta.- NACA66012 (One of the various versions of Larsons Vendetta)


Hope this helps.
Old 11-16-2009, 03:18 PM
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Default RE: Q-40 Airfoil selection

Thanks guys for all the help, this will assist me a bunch in evaluating my options!

Thanks again to all...
Old 11-16-2009, 05:12 PM
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Default RE: Q-40 Airfoil selection

Loki and Polecat are acctually MH25, MH24 would need about a 12" chord to get the wing thickness. Gr7 is totally different again .
If you know your wing layout including your root chord pick an aerofoil which has sufficient % of chord thickness to suit
Terry
Old 11-17-2009, 01:12 AM
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Default RE: Q-40 Airfoil selection

Actually Terry, I think the loki/polecat is mh26-mh23
Old 11-17-2009, 06:43 AM
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Default RE: Q-40 Airfoil selection

Could be right Karl
I stand corrected
Old 01-16-2010, 10:08 PM
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Default RE: Q-40 Airfoil selection

Thanks for the help guys, and to those of you I corresponded with by email too; I appreciate the assistance. I have narrowed my choices down to 2 airfoils after a lot of theoretical testing, and I am in process for an initial design approval from the NMPRA board. Once we get the OK from NMPRA, I may leak out some teasers as it is under construction. I have an airfoil picked out that suits it very well, but I have an alternative if that one proves a little too radical.

I have constantly been impressed with the caliber of talent and the willingness of the big dogs of racing to help out when asked. Thanks to all of you who have helped me, and I will remember you if you ever approach me for an airplane or need some help that I can offer. You guys are the best

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