Modernizing the Aquila Grande airfoil? - RC Groups
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Jul 28, 2005, 11:25 PM
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Modernizing the Aquila Grande airfoil?

I've wondered if it is possible to take an existing Aquila Grande rib set and modify them to be close to a modern flatbottom airfoil like the AG-3X series. Has anyone thought about this? Tried it?

When I print the Aquila airfoil (not Grande) and the AG-35 on paper and hold them up to a light bulb the differences are that the leading edge needs lifting and the mid chord needs to be a little thinner. With the only tools I have on hand it looks like the next step is to scale the printout to a rib in my kit and eyeball that.

Does anyone have the Aquila Grande coordinates?

I'll also look at the HT21 airfoil for the tail. When I get around to building the kit I might as well try some improvements. I've already gathered some tips from other threads.
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Jul 29, 2005, 12:09 AM
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OK, here is the old fashioned way of comparing airfoils.

This is the AG-34 and the Aquila Grande root rib. The lower lead in is identical! The leading edge is too pointy. There is about 1mm missing from the first 5% on top. Then the top from 20% on back needs thinning.

Does anyone have the Aquila Grande ribs in file format they would be willing to share? I could throw in the airfoils I want and send it to a laser cutting shop.
Jul 29, 2005, 10:48 AM
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Thanks, Ollie. Profili I know about and is nice. I didn't know about PCSoar and it looks quite interesting. I'll have to give it a try soon.
Aug 02, 2005, 11:24 AM
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Originally Posted by Keith Watson
Thanks, Ollie. Profili I know about and is nice. I didn't know about PCSoar and it looks quite interesting. I'll have to give it a try soon.
Hi Keith,
Please keep me posted about this project, having an AG and an AXL (which I'd love to experiment a little with more modern airfoils for it) I'm interested in seeing what you come up with.
Aug 02, 2005, 02:30 PM
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Hi Fernando,

I started looking into this project 3 years ago. But it was your recent Aquila threads which rekindled my interest. My time this week is diverted to finishing the build of my own design DLG. Then I will start on the analysis of the AG wing.

Coordinates and polars (computed and wind tunnel) are available for the Aquila airfoil. It is my understanding that the A and AXL use the same airfoil. I have been unable to find coordinates or polars for the AG. I'll get coordinates off my rib set and plug those into Profili (XFoil) to get some polars. Then there is some measuring to do on the plans to get enough data to feed to PCSoar.

I'll post progress and results as I go along.

Aug 02, 2005, 02:45 PM
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Both coordinates and polars.
Aug 02, 2005, 07:52 PM
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I just KNEW someone was going to interpret it that way. I was using Fernando's nomenclature of Aquila (A), Aquila Grande (AG), and Aquila XL (AXL).

Great link though. I have used it before for a DLG I'm about to finish. Once my Profili license arrives I will be importing the AG-3X series coordinates from there. And since neither Profili nor UIUC Airfoil Data Site have the Aquila Grande airfoil I'll measure those coordinates myself.

This is going to be fun!
Aug 06, 2005, 12:40 PM
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Lots of measuring, lots and lots of transferring numbers by hand (aren't computers great), and I have some info.

Polars were generated with Profili/XFoil. PC-Soar was used to generate the airframe comparisons. The Aquila Grande airframe was used in each case, the only difference was using the airfoils from the Aquila (A), Aquila Grande (AG), and AG-34 (AG34).

L/D numbers were the same up to 22mph flight speed.

At 24mph the L/D improves 10% changing from A to AG, and 2% more changing to AG34.

At 28mph the L/D improves 18% changing from A to AG, and 7% more changing to AG34.

At 34mph the L/D improves 23% changing from A to AG, and 22% more changing to AG34.

So the Aquila Grande airfoil is pretty good. But when it comes to penetration the AG-34 is even better.
Aug 06, 2005, 01:51 PM
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great info Keith!!!
This is quite motivating to start another set of wings for my AG and AXL!!!
Aug 06, 2005, 06:43 PM
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Fernando, here are some graphs from Profili. They give more info than PC-Soar. I still need to learn the details of reading polars.

PC-Soar reports that for this airframe a Reynolds number of 100,000 is 15mph and 200,000 is 30mph.
Aug 07, 2005, 01:42 AM
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Polars are way up too far for me to even know what they are...
I've been fiddling around with pc soar, profili and compufoil to decide which one I want to pay for, but still waiting to learn more about planes before I make my conmitment, so far everything is like advanced chinese to me.
Some day..... May be....
Aug 07, 2005, 05:28 AM
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Begin with the concept of polars. Study them if want to use the ideas. If you have questions, we will help you over the hard parts.
Aug 07, 2005, 11:10 AM
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Fernando, here is what I have found so far from using PC-Soar and Profili. PC-Soar appears to calculate Reynolds numbers based on the size of the airplane and uses polars for comparison, that's it. Ollie's link is describes this output. Profili of course generates polars. I have not yet used the rib templates or wing layout features in Profili. When I looked at the Compufoil website there is a long list of paid options to pick and choose what features you want.
Aug 07, 2005, 02:37 PM
Great work so far. I'll be watching this thread closely.

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