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Old Dec 14, 2012, 06:50 AM
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Aeromodeller free flight plans

Hi.
In keeping with the festive season here is another Christmas edition of AEROMODELLER this time from 1943.

Another wonderfully nostalgic RUPERT MOORE cover painting was again featured.

The first free flight plan was for a diminutive HAWKER TYPHOON by R.COLEMAN.

This was just 12 inches in wingspan and had a fuselage made from brown paper. Plan is full size.

Next to the CHALLENGER a sort of scale looking glider. No construction article but all you need is on the plan which is reproduced half size. Its’ an intriguing looking vintage model

The designer was MICHAEL RUSSELL aged just 13. Giants walked the Earth in those days.

Another vintage rubber model was PETER by R.V.BENTLY with the plan being reproduced half size.

Structure is conventional and it would once again build up into an attractive model.

Back to gliders with the next plan being a scale AIRSPEED HORSA troop carrier by R.N. BASE.

Wing ribs and formers are full size.

As always there were many interesting articles to be read one of which I have scanned and posted here. It was by P.E. NORMAN later to become famous for his many scale free flight designs.

Peter explains how to make your own Air-Wheels from a bicycle inner tube.

Finally to AIRCRAFT DESCRIBED where two aircraft were covered. The first is the DE HAVILLAND 83 FOX MOTH by E.J.RIDING then the 4 CANNON MUSTANG is fully described by H.J. COOPER.

Cheers

Algy
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Old Dec 14, 2012, 09:23 AM
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I actually tried making the wheels that way from those very instructions while I was building my KK Falcon. It ll went well surprisingly except I couldn't find a glue that would hold the rubber and seal it well. I could only keep them inflated for a few seconds then some seam would leak or break loose. Some glues dried too hard and ripped of the rubber as it wouldn't flex while inflating.
Ian
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Old Dec 14, 2012, 09:41 AM
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This Mustang buff is very excited to see early scale views of Mustang made during the war years. AFAIK earliest published 3-view in 1940 Aero Digest and was copy of the actual rendering made by Edgar Schmued shown to British for initial sales agreement. Later drawings by William Wylam ,which appeared in June '44 Model airplane News appear to have made deliberately inaccurate (mis-information??).

1943 article has better (more accurate) 3-view and is overtly accurate in the narrative. Of note is mention of correct P-51 designation (no letter for sub-type) and that popular name "Apache" is correctly attributed to NAA factory origin and actually was never officialy applied to any USAAF Mustangs.

Thank you algy!
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Old Dec 14, 2012, 04:18 PM
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Quote:
Originally Posted by algy2 View Post

Next to the BALSA BUG by W.A. DEAN who designed this attractive little vintage rubber model to try out a triangular fuselage. Plan appears to be full size. Should look very nice in the air.

.
Printed out Balsa Bug. Airfoil on original hand drawn plans not super smooth- what airfoil would you experts recommend for a small model like this one?

thanks in advance-
'beat

(plan attached to quoted post)
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Old Dec 14, 2012, 07:12 PM
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looks almost Clark Y

That airfoil looks almost like the popular Clark Y, but with more of a flat bottom.

You can get lots of airfoils as data sets and X.Gif plots at Prof. Selig's database at the University of Illinois (Urbana-Champaign) web site.

http://www.ae.illinois.edu/m-selig/a...atabase.html#C

The real Clark Y has a 3% raised leading edge, when the back half of the bottom is lying flat. It was good enough for Charles Lindbergh.

There is also a "smoothed" version on the site with ID "Clarkysm"
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Old Dec 15, 2012, 07:43 AM
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Clark Y is almost universaly mis-applied to nearly any "flat bottomed airfoil" and is quite often assumed to have been the airfoil of the high winged Piper products. There is considerable difference between a clark Y and USA 35B of Pipers. Latter is slightly undercambered and has it thickest point noticably father forward than former.

That University of Illinoise airfoil site is one of my favorites. Pretty good source and its companion, "Incomplete Guide to airfoil Usage" (first link listed) is good too.

As an aside, i'd like to know when the aerodynamic academic community changed to a universal system where the ordinates for airfoil references changed. Excellent example is Chark Y which used to be referenced to its flat bottom as the Zero incidence line. However, as shown in the above diagram, it is now referenced to a medien line drawn thru the extreme LE and TE points and now appears to assume a slight negative incidence.
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Old Dec 15, 2012, 09:01 AM
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As I mention, you can still mount the Clark Y with the rear flat portion of the bottom parallel to the datum line of your plane, giving a positive 3 degrees incidence. The line from leading edge to trailing edge seems useful for consistent plotting, with all the different possible shapes.

Packardpursuit, I'm glad you find Prof. Selig's site useful too. It's packed with stuff.

Joe
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Old Dec 15, 2012, 12:25 PM
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Quote:
Originally Posted by DuPageJoe View Post
That airfoil looks almost like the popular Clark Y, but with more of a flat bottom.
Yeah- I'm familiar- great resources, thanks.

I did convert a small FF old timer to a Drela DLG foil. Having spent time with gliders, I think it should work extremely well. It'll be faster, but as I converted to electric and rc, it should make for a great little powered glider. The wing loading is about right for it.

cheers
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Old Dec 16, 2012, 11:38 AM
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DuPageJoe said:
"As I mention, you can still mount the Clark Y with the rear flat portion of the bottom parallel to the datum line of your plane, giving a positive 3 degrees incidence. The line from leading edge to trailing edge seems useful for consistent plotting, with all the different possible shapes."

Kinda my point. Original published NACA data for Clark Y had the 0 deg. as the flat portion of the lower aft. Now it's considered +3 deg. when resting on the flat portion. When did the change in reference visualization occur? it would seem that at some point there was chnge in how airfoils got referenced. Could be a commonality of cataloging and understanding of airfoils. In any event ,according to the UI airfoil site, upright reference are no longer automatically measured up/down a line perp to the Zero deg reference. Namely, all non-symetrical airfoils.

I know this not a huge change or issue, but I just find it strange after doing it "the otherway" for so long.
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Old Dec 16, 2012, 11:54 AM
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DuPageJoe said:
"As I mention, you can still mount the Clark Y with the rear flat portion of the bottom parallel to the datum line of your plane, giving a positive 3 degrees incidence. The line from leading edge to trailing edge seems useful for consistent plotting, with all the different possible shapes."

Kinda my point. Original published NACA data for Clark Y had the 0 deg. as the flat portion of the lower aft. Now, it's considered +3 deg. when resting on the flat portion. When did the change in reference/theoretical visualization occur? Could be a commonality of cataloging and understanding of airfoils. In any event ,according to the UI airfoil site, upright references are no longer automatically measured up/down a line perp to the Zero deg reference. Namely, all non-symetrical airfoils.

I know this not a huge change or issue, but I just find it strange after doing it "the otherway" for so long.

There is also the nagging problem with the airfoil as presented in the new format has no historical reference as to how it was configured in a particular aircraft. So now ,do we go back and correct all the listed incidence references for famous aircaft (including models) ? Or perhaps we need a huge asterix somewhere/everywhere?
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Old Dec 16, 2012, 02:08 PM
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The Aeronca C-2, and C-3, used the Clark "Y". Reference the Paul Matt drawings, and you will find that the C-3 had a 3 deg positive incidence.

[QUOTE


There is also the nagging problem with the airfoil as presented in the new format has no historical reference as to how it was configured in a particular aircraft. So now ,do we go back and correct all the listed incidence references for famous aircaft (including models) ? Or perhaps we need a huge asterix somewhere/everywhere?[/QUOTE]
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Old Dec 16, 2012, 04:48 PM
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Quote:
Originally Posted by wingbeat View Post
Printed out Balsa Bug. Airfoil on original hand drawn plans not super smooth- what airfoil would you experts recommend for a small model like this one?

thanks in advance-
'beat

(plan attached to quoted post)
Wingbeat, I'm not quite clear what the span of this model is? Appears to be around 20-22" with a 2" chord? If so then that Clark-Y-alike airfoil is going to be way too thick. The Reynolds number will be roughly 15-20,000, ie really small.

The best thing for this size would be a very thin airfoil with modest camber, say 4%, actually a curved plate is close to ideal but since you have a built up wing it's impractical unless you do something in the No-Cal style.

The AG airfoils are good at low Re but they are optimized for a wide speed range. Good for DLG but not really needed on a FF rubber model that for best duration should cruise around at thermalling speeds, ie as slowly as is reasonable. More camber is needed to fly long durations on low power at low speed. Have a look at Benedek and Brian Eggleston airfoils that are used on Wakefields and Nordic Gliders. I used a BE50 on my latest Bostonian (not flown it yet!) the problem is building such thin wings stiff enough. Have a look at this site: http://www.airplanesandrockets.com/r...l-plotting.htm for a few ideas (although the Re numbers for these are higher, the rubber powered options will be too thick but the Nordic airfoils are more like it.)

You will really need to keep the wingloading down, this really is the secret to good duration at such low Reynolds numbers.


Jon
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Old Dec 16, 2012, 05:52 PM
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challenger_i
Your statement got me looking for my copies of Paul Matt Aeronca C-2, C-3('s) and K drawings. For a moment there I thought I was mistaken. but now see that Matt infact listed the Clark Y at 0 deg. incidence (referenced to flat portion of lower camber line) and not 3 deg. positive, as would seem to be indicated by UI airfoil website. The way Matt illustrated his Clark Y's is exactly how the incidence is shown in Aeronca factory wing drwings, for my 1938 Aeronca KCA, which I owned and operated for a few years.

This reference for O deg incidence of a Clark Y is same for Monocoupe and Ryan monoplanes (incl. Spirit of St Louis). The UI method of reference is different from original ref system used by NACA . the point I'm trying (failing?) to make is in the past, the airfoi would be considered at O deg insidence in these examples. Today, while nothing changed on the aircraft the airfoil would be viewed as having approx 3 deg. positive. The only thing that has changed is how we percieve the airfoil.
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Old Dec 18, 2012, 12:58 PM
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Goldberg Advanced Tractor

Here are plans for a 150 sq inch indoor microfilm covered tractor by the great Carl Goldberg published in a Chicago Park District handbook from 1938. I got it as a reprint by Charlie Bauer of 4Pi, Inc.The airfoil has about 6.7% camber (3/8 inch per 5.5 inch chord) and is TLAR, matching a French curve I have. These days a 4-6% camber Simplex (logarithmic spiral) airfoil would probably be used, since it is easier to trim to the elliptical plan.

In those days, when a computer had 2 legs and a pencil behind his/her ear, French curves were much in use. An article on wing design by Avrum Zier on wing design in Flying Aces November 1934 called for a No.13 French curve to make airfoils, with high point at 30% of chord.

I've found a good Excel sheet to calculate the Simplex airfoil, if anyone cares for the advanced version.

Just thought I'd get back to the theme of this thread.

Joe
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Old Dec 18, 2012, 02:05 PM
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Alternate wing for Balsa Bug

Found a nice looking old timey wing for the Balsa Bug at the Plans Page. Its flat bottomed and much thinner than the original. Its on the MiniHobbies, a cut down plane from an original in a British magazine.

http://www.theplanpage.com/things/mi...iniHobbies.pdf
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