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Old Feb 22, 2002, 02:09 PM
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Steve Fehr's Avatar
Chesapeake, VA
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Scratch-built slow flyer P-51?

I've been craving a good scale warbird for the longest time, and a slowflyer too... Right now the problem is, I really can't afford it. Then, I realized I think I can kinda afford if I scratch-build, heh.

I drew up plans fly a 1/12 scale-as-possible P-51, loosely based on a FF P-51 I built a few months ago. I built one wing for a prototype, but it's a little heavier with more flex than I'd like but I see some improvements (0.7oz). I figure at this rate, the airframe should come in about 3-4oz and a geared SP280 & 8x270 pack w/servos&RX bringing AUW up to about 10-11oz.
Wingspan 37", loading will be about 8oz/ft, thrust roughly 14oz. Was thinking about using a SB7032 airfoil. Would a geared SP100 be powerful enough? it would certainly reduce weight & speed a great deal...

I really want this plane to fly in the park beside my house. It's about 200x75', surrounded by trees and overhung with high tension lines. BUT it's like right outside my house Wind is always blowing about 10-15mph; wind at ground level is much reduced, and the turbulance doesn't really affect my other planes when I bring them out for glide tests, but they're a lot bigger... This is my first slow-flyer. Are my expectations realistic? Will this plane be capable of relaxed flying in such a small field, or should I head back to the drawing board? Would scale ailerons be enough, or should I go full-wing?

[Edit] - Changed 27" wingspan type to 37"... bonehead mistake,
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Old Feb 22, 2002, 03:23 PM
pushing both extremes
Zoom's Avatar
San Jose, California, United States
Joined Oct 2001
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I was thinking about doing something similar a while back. I ended up scratch building a plane which has some features of a p-51 (low wing, landing gear in wing, etc) but my focus was not to be scale. Rather it was to build something that would fly really well in a small park, and learn a little about what would work and what would not. I have submitted the plans and instructions here to ezone for them to publish as a construction article. I dont know how long it will take for them to review it and post it, but I would be happy to discuss my experience with you.

A couple of quick points.

I think you could build it lighter than 10-11 oz. My plane came in at 8.5 oz. I have seen other similar sized plane even lighter.

I dont think you'll get 14 oz of thrust, maybe about half that. The m100 touts their 7 oz. thrust.

I think it will be hard to fly in 10-15 mph winds in that small an area. The problem, as you probably know, is that as you lower the wing loading (to fly slow) you increase it's susceptibility to being blown around by the wind.

Still you could try it at a bigger site and once you get used to it, try it at the small park with a little more wind on each attempt to see when the fun goes away.

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Old Feb 22, 2002, 05:04 PM
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Chesapeake, VA
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Well, winds in this little park aren't 10-15- it's blocked by trees for the most part, it's just fairly turbulent; wind direction is highly variable, etc. I've hand-launched and flown my 2m glider in circles here before on windy days, so I'm hoping this'll be alright... I definately will learn to fly it on a perfectly calm day in a big field, lol...

Pcalc estimates 14/5oz thrust (static/in-flight), on 5:1 SP280 (w/8x270) 11x11 prop for 6oz weight, with a flight time of 5:01.

Can I get 7oz from the m100? dang, that's plenty! I'd definately be able to get down to 8oz with that... not like I need vert performance with power lines 50' overhead
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Old Feb 22, 2002, 05:13 PM
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Dallas,TX
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re: 200x75'
Yes, I think you could fly it in that area. However I agree with starting in a larger area till you get the bugs worked out. My theory, is when test flighting, get as much room as possible and always start off into a mild wind and climb as much as the wires will allow before trying the first turn. I've had scratch builts slip on the first turn and even 50 feet isn't alot of buffer.
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Old Feb 22, 2002, 05:46 PM
pushing both extremes
Zoom's Avatar
San Jose, California, United States
Joined Oct 2001
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Oh, Matt joining the discussion reminded me... I should state that my little park flyer is a balsa built up with SoLite covering. You could also go the foam route. Much faster build time I'm sure, but I haven't tried a foam scratch build yet myself. Some day...
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Old Feb 22, 2002, 07:00 PM
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Ralph A. D'Amelio's Avatar
United States, MA, Chelmsford
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Steve, something likes...m100 will tool this around quite nicely

Foam/balsa AUW of 3.6 oz...ailerons/elevator
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Old Feb 22, 2002, 07:01 PM
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2nd image
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Old Feb 22, 2002, 09:02 PM
pushing both extremes
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San Jose, California, United States
Joined Oct 2001
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That's a nice looking plane Ralph. Can you give a little more info on it, like wing span, area, flying weight, what prop is that on the m100, what batteries you are using, and some idea of it's performance and duration? Thanks. Very cool.

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Old Feb 22, 2002, 11:28 PM
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Zoom

F-51 WS 26in dry wt 3.6 A 110 sq in 8/6 prop 300nimh. Use this setup it on my me 109 at about 10 oz which flew very well. Haven't flown the mustang yet..waiting for better spring-like weather.
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Old Feb 23, 2002, 01:07 AM
pushing both extremes
Zoom's Avatar
San Jose, California, United States
Joined Oct 2001
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Oh, you're building up a little squadron of those things. Looks good. I'm working on a Crazy Max now so I can practice some aerobatics, but after that I'm going to do another scratch built. I like the m100, so maybe something along these lines. Just yesterday my next project was going to be an overpowered biplane with a fully symetrical airfoil, but low wing loading, so it can slow way down. Yikes, I have "can't have enough planes" disease. Ok, who gave it to me?

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Old Feb 23, 2002, 07:57 AM
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Steve Fehr's Avatar
Chesapeake, VA
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Doh! I said 27" wingspan when I meant 37" . Wing loading, weight, etc, was all for a 37" plane... that change anyone's opinions of whether an m100 will work? & thanks for the info, Ralph!
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Old Feb 23, 2002, 11:23 AM
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steve, I fly alot in my backyard which has about 100 x 150 clear areawith bushes, big pine and other misc trees surrounding the perimeter. GWS TM, my Pober Pixie, Evans VP with DXA motors fly ok here. My me109 with the m100 flies a little to fast and I keep on getting shot down with ack-ack (aka tree branches) trying to get to combat altitude. sure a lot of fun and get good experience at re-building. Its hard to say the plane your designing will fly comfortably in that area. A larger area is better suited as mattk17 mentioned to work out the bugs. Easy for me to say...but I don't always follow my own advice. Good luck.
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