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Design => Stunt design => Topic started by: Tim Wescott on November 17, 2012, 02:05:07 PM
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This may belong in the 1/2 A forum. But I'll ask it here, anyway.
I just got a recommendation that a Pat Johnson Ringmaster 207 (with a 207 square inch wing) would work well with a McCoy or Cox Black Widow 049.
Yet, I have a plan from 1954 for a CL flying boat that calls out a K & B 19, and has a 250 square inch wing.
Why such a small difference? Is it just that the predicted weight of the RM 207 is around 10 oz, while the Aquabat looks like it'll be around 20oz all up? Or is a Black Widow all that more powerful size-for-size than the K & B?
Or what?
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I am beginning to think that weight, or, maybe more accurately, wing loading, is the important thing in determining power needed. It is not the only factor, of course. 10 oz for a 207 square inch wing CL airplane sounds fine for something like a TD 049. I think it would need to be a couple oz lighter for a Black Widow. As to the relative power to weight of a Black Widow vs a Torp 19, I couldn't say as I don't have appropriate engine reviews at hand. I've flown both engines CL and find them difficult to compare. The Torp 19 is a powerful engine (held the A CL speed record at one time). I think the one I had would have easily flown the stunt pattern on a large Flitestreak.
The Aquabat might need more power to get off the water. I think a 20 oz large Flitestreak with a Torp 19 would fly very well. but I would think the Aquabat more a sport model. Also, a 250 square wing is almost 25% larger than a 207 square wing.
Thinking about it, I'd probably take each airplane as an individual situation and do very little comparison with other airplanes.
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Hi Tim. Jim is right on about needing the power to get on step and off the water-in a half lap or less. If you look in the magazines of that era there was more emphasis on speed (since stunt capabilty was marginal I guess). Many airplanes seemed overpowered, said from a guy who puts a piped .61 in a .40 size airplane today! I have a Torp .09 on a OT FF Megow Ranger that does a job about like I think a Tee Dee .049 would. As a kid I had the Torp .23 in a junior Nobler that seemed like the perfect package. I always thought the Jr. Flew better than the full-size Nobler. (What did that have to do with anything?). Anyway, engine up for the water! Have fun with it!
Dave
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Hi Tim,
There is so much to consider like Jim and Dave say. The RM 207 was expressly designed with 1/2A power in mind. Drag (the different types I don't know much about), wing loading, and other factors I am less knowledgeable about, all must be considered when picking an engine for a model.
I do know that many times a smaller "modern" engine will fly a model designed for a larger one. And people will always work out ways to put larger engines into smaller models.
(personally, I feel that the McCoy/Testors .049 will be a touch small on the RM207)
BIG Bear
RNMM/AMM
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Come on you Glowheads! Let us know any ideas/formulae you have up there for making that 1 gallon can last over winter?
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This may belong in the 1/2 A forum. But I'll ask it here, anyway.
I just got a recommendation that a Pat Johnson Ringmaster 207 (with a 207 square inch wing) would work well with a McCoy or Cox Black Widow 049.
Yet, I have a plan from 1954 for a CL flying boat that calls out a K & B 19, and has a 250 square inch wing.
Why such a small difference? Is it just that the predicted weight of the RM 207 is around 10 oz, while the Aquabat looks like it'll be around 20oz all up? Or is a Black Widow all that more powerful size-for-size than the K & B?
Or what?
Or what, mostly. Pat's is a stunt plane, the flying boat may have been touted as a "stunter" but that might mean it can do a loop. 1/2A's at the time had incredibly feeble power compared to something like a Black Widow. All of the Cox engines were an amazing improvement over the Infant Torpedo and the like.
Brett
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Come on you Glowheads! Let us know any ideas/formulae you have up there for making that 1 gallon can last over winter?
Ah, I will take a stab at this and will try not to be too technical. To make a gallon of fuel last over the winter, live somewhere North where there is a lot of snow, is really windy and really cold. Another solution is to not fly very much in the winter.
Keith
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Ah, I will take a stab at this and will try not to be too technical. To make a gallon of fule last over the winter, live somewhere North where there is a lot of snow, is really windy and really cold. Another solution is to not fly very much in the winter.
Or switch to electric!
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Or switch to electric!
Tim
I was trying to not make my answer too technical like you just did. But technical is OK.
KT