Maynard Hill TAM 5 Aspect Ratio

Maynard Hill TAM 5 Aspect Ratio
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Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 1:21:13 AM

destructiveTester

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For those of you who have not read this, here is an excellent article by the great Maynard Hill about his background in modelling going through to his record breaking transatlantic flight in 2003.

http://www.modelaircraft.org/mag/mhill/hillindex.htm

I was interested to note that the Aspect Ratio of TAM 5 was about 4.7: (72.1 inch span 15.4 average chord.)

(http://www.modelaircraft.org/mag/mhill/photos/MAPREVIE.gif)

This is a low aspect ratio for a design which has been optimised for low drag (Maynard talks about how he experimented with varying body cross -sectional areas).

Question: Is the choice of aspect ratio related to strength to weight, i.e. by reducing structural weight per unit area, drag is therefore reduced.

Or is it to do with stability and control problems?

Or is it simply that induced drag reduction is not as important as having a strong structure - especially when you are on auto-pilot over the mid-Atlantic!

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 2:38:07 AM

dick Hanson

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Obviously the REAL setup had a high aspect ratio wing as wind tunnel tests prove that low aspect ratio stuff is no good for anything except foamies.
Or so I have been told.
OK that was nasty.
Honestly -in all of the small stuff I have tried - (meaning models) ,
which fly slowly, fare much better with low aspect ratios.
Better handling - better aerobatics -
Also - they are easier to build , than a high aspect ratio setup.
Today , we gave a thorough bashing around to a 3.3 aspect ratio setup (aerobatic)
I let a friiend also try all kinds of goofy stuff -such as very, very tight skidding turns.
Here is where a high aspect ratio will kill you.
The low aspect ratio setup just whips around - there is far less speed difference in the wing tips

< Message edited by dick Hanson -- 9/27/2004 2:40:15 AM >

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 3:09:08 AM

Tall Paul

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if you read Maynard's complete story you'll understand how a successful design evolves...
If it ain't broke, don't fix it!
.
Note:The weight change during the flight was close to 50%, and the flight trim automatically changed to suit.
You don't get that done without a lot of testing and analyzing what is really happening.
The smear about the "real" airplane is uncalled for!

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 3:44:38 AM

HighPlains

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I'm starting to feel that Richard was a bottle baby.

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 12:12:48 PM

destructiveTester

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Maynard Hill's TAM 5 landed with just 2 ounces of fuel left in the tank on arrival in Ireland.

He knew he needed as much efficiency as he could get - and I am also sure he totally knew what he was doing with his wing design.

(Dick - most of us are aware of your successes with low AR's in the kind of fliying you like where high manouverability is key. Maynard's TAM series of aircraft do not have to be that manouverable - they were designed for straight line flight, so the lower AR choice could not be for the reasons you cite - regardless of how good you've found low AR's to be.

Re: wind tunnel versus real world results, Maynard mentions that he didn't expect to get actual wind tunnel performance from his aircraft even though his CDo was less than .02 - he reckoned on about 50% of the projected performance - which in the end was about right!

The TAM 5 achievement was not just down to aerodynamics of course - but down to an extremely good understanding of tuning engine setups for duration, autonomous control, RC equipment, logistics, weather, construction/structural knowledge and general modelling and aeronautical experience. However this is an aerodynamics forum and I am interested in how much like a "normal" RC model's wing the TAM 5 wing was - save for the fact it seems to have just one aileron?

I would have assumed he would have started with a powered glider type plane with a good lift/drag ratio?

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 12:23:33 PM

DICKEYBIRD

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I 'spec the final wing design had a lot to do with the size of the fuel tank inside it.

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 1:36:19 PM

dick Hanson

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Smear?
Never!
just a gentle poke at those who don't have as much faith in hands on results --as they have in specialized , isolated tests.
Why?
Because they have little or no hands on experience.
Surely , you don't fit into that group of armchair "experts"---

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 2:28:56 PM

destructiveTester

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Please Dick Stop! Not another thread devoted to the same topic!!!

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Wake up call! - 9/27/2004 3:26:21 PM

Johng

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Hello, there is no doubt that a higher AR wing would have done better here. In fact, this same mission was accomplished by a UAV company called Insitu Group some years ago using a set of modified sailplane wings, from RnR I believe. Even among the RC sailplane set, the differences in AR are well known. 2M sailplanes cannot compete with 3m open class ships. I've spent a few afternoons with what is considered a very good performing 2m sailplane watching in envy as the 3m guys sailed easily from thermal to thermal. If you want to compete in 2m, get a 2m. If you want to have fun soaring get a 3m or larger plane. Back to the subject-

The interesting thing about Maynard's record is that it is an FAI record. I can't believe no one brought this up yet. What that means is that it was done within FAI limitations. That means less than 5 kg total weight, less than 10 cc motor and LESS THAN 2m WINGSPAN. That is the major reason for the lower than optimum aspect ratio. That wing is exactly what one would expect for an optimized wing under a wingspan limit - with maybe the exception of winglets.

Without those limits I could probably modify a 4-5 m sailplane to do the same thing. But Maynard is the one who did it, so hats off to him!

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 5:27:28 PM

dick Hanson

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I did forget about the FAI rule.
I have done many FAI designs -for aerobatic models
The last one was my EMC2 -still competitive .
.

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RE: Wake up call! - 9/27/2004 5:31:52 PM

destructiveTester

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JohnG - thanks - that explains a lot!

Amazing. I was not aware of the FAI limitations on the record.

"Without those limits I could probably modify a 4-5 m sailplane to do the same " - are you the guy I should get in touch with for some GPS programming, engine tuning and modifying and RC gear tweaking? Maybe a bit of satellite telemetry too ?

The thing that gets me is not so much the airframe design but everything else about the project.

BTW as far as I know DickyBird, the fuel was not in the wing - Maynard enlarged the body instead because his in-wing fuel tank system wasn't sufficiently reliable.

RE: 2m, 3m sailplanes - your lift drag and sink rate will improve significantly with both increases in Reynolds Number and AR. Sink rate will degrade with increased wing loading, but lift/drag may well improve with increased wing loading. Are the 3m sail planes the same or less wing loading? and are they higher AR or just bigger aircraft all round?

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RE: Wake up call! - 9/27/2004 5:38:24 PM

Johng

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quote:

ORIGINAL: destructiveTester

"Without those limits I could probably modify a 4-5 m sailplane to do the same " - are you the guy I should get in touch with for some GPS programming, engine tuning and modifying and RC gear tweaking? Maybe a bit of satellite telemetry too ?

I'm no expert on that stuff, but I have sifficient knowledge to take the commercially available stuff out there and integrate it into a working system for something like this. It's not that hard to find all the stuff you need. I think for a small donation you can become part of Maynard's group and get access to all the details of the aircraft systems they used.

quote:

RE: 2m, 3m sailplanes - your lift drag and sink rate will improve significantly with both increases in Reynolds Number and AR. Sink rate will degrade with increased wing loading, but lift/drag may well improve with increased wing loading. Are the 3m sail planes the same or less wing loading? and are they higher AR or just bigger aircraft all round?

Higher aspect ratio and lower wing loadings are the norm. THe recent supra/aegea designs from Mark Drela are light enough that some pilots add balast for normal light-wind flying, just to have the effects of the extra weight.

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 5:43:53 PM

dick Hanson

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build it and fly it .
It is an excellent method of finding out what actually happens - which may/may not be expected.
One thing to watch out for--
It is easier to build a stronger wing at lower aspect ratios.
So - If the total weight is of any consequence- and it usually is a huge factor, the "ideal wing planform " may not be the practical/usuable setup.

< Message edited by dick Hanson -- 9/27/2004 7:23:16 PM >

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/27/2004 11:36:33 PM

HighPlains

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If your only tool is a hammer, may all your problems be nails.

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RE: Maynard Hill TAM 5 Aspect Ratio - 9/28/2004 12:27:51 AM