Wing loading, thrust?
08-18-2003, 02:53 AM
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Wing loading, thrust?
I am not sure how to figure out wing loading or engine thrust. Even if I did I wouldn't know what the numbers meant. I am hoping somebody can help me out.
Wing loading for WM 80" extra300s? Dry weight 14.5 lbs Wing area 1175 sq inches.
Thrust? Moki 210 turning a Mejlick 20x9 at 7500 rpm.
To anybody that can figure the numbers out. How do they sound? Does the plane need a diet? Bigger engine? Thanks
Wing loading for WM 80" extra300s? Dry weight 14.5 lbs Wing area 1175 sq inches.
Thrust? Moki 210 turning a Mejlick 20x9 at 7500 rpm.
To anybody that can figure the numbers out. How do they sound? Does the plane need a diet? Bigger engine? Thanks
08-18-2003, 11:58 AM
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Wing loading, thrust?
loading = weight / area
For models, the units are normally ounces per square foot.
(14.5 lb * 16 oz/lb) / (1175 in^2 * 1/144 ft^2/in^2 =
= 28.4 oz / sqft
... which is typical for a model airplane
Each square foot of the wing is carrying 28 oz of the model's weight. If you take two models that are identical, but one is hevier (higher wing loading), you'll find that the heavier one has to fly faster, and has a higher stall speed.
There is no simple calculation for thrust. Some empirical formulas were published by AMA magazine back in the 80's and these are used in the freely available "ThrustHP" program. I've entered your numbers and it tells me that a 20x9 (APC, not Mejlick) prop at 7500 generates 27 lb of static thrust.
ThrustHP is somewhat optimistic, the consensus seems to be to take about 70% of the number it generates... so 19 lb may be closer to reality.
It sounds fine to me, but I have no experience with models of that size...
For models, the units are normally ounces per square foot.
(14.5 lb * 16 oz/lb) / (1175 in^2 * 1/144 ft^2/in^2 =
= 28.4 oz / sqft
... which is typical for a model airplane
Each square foot of the wing is carrying 28 oz of the model's weight. If you take two models that are identical, but one is hevier (higher wing loading), you'll find that the heavier one has to fly faster, and has a higher stall speed.
There is no simple calculation for thrust. Some empirical formulas were published by AMA magazine back in the 80's and these are used in the freely available "ThrustHP" program. I've entered your numbers and it tells me that a 20x9 (APC, not Mejlick) prop at 7500 generates 27 lb of static thrust.
ThrustHP is somewhat optimistic, the consensus seems to be to take about 70% of the number it generates... so 19 lb may be closer to reality.
It sounds fine to me, but I have no experience with models of that size...
