cepeda pascal a écrit :
Il faudrait aussi une envergure et une surface alaire.
Loel Beau
bonsoir ,
Voilà les carectèristiques de l'aile :
Corde empl : 560mm
Corde Saum: 235mm
Longueur d'une demi aile avec saumon 2165mm
Fléche : 120mm
Surface alaire sans fuso : 172.12 dm²
C'est un moto planeur avec décollage du sol depuis son train .
a+ pascal
Voici un premier essai, j'ai supposé une masse à vide de 13.5 kg, un
profil eppler 205 et une batterie de 10 lipos 3700 2S car j'ai pas les
caractéristiques électriques des G ions .
Tel que, cela vole mais on n'est pas optimal en performances, une fois
les g ions dans le système je te referais les calculs.
Bonne soirée
MotOpinion - Untitled
99,9m above Sea Level, 101,3kPa, 14,5°C
Motor: A60 20 S; 245rpm/V; 1,7A no-load; 0,027 Ohms.
Battery: FlightPower 3700 (20C); 10 series x 2 parallel cells; 3700mAh @
3,7V; 0,0037 Ohms/cell.
Speed Control: Castle Creations Phoenix 110HV; 0,001 Ohms; High rate.
Drive System: 20x8 (Pconst=1,06; Tconst=0,995) direct drive.
Airframe: motoplaneur 8.5kg; 172dm²; 16141g; 93,8g/dm²; Cd=0,04;
Cl=0,42; Clopt=0,7; Clmax=1,13.
Stats: 169 W/kg in; 146 W/kg out; 12m/s stall; 15,2m/s opt @ 88% (37:07,
43°C); 19,7m/s level; 2,66m/s @ 10°; -1,13m/s @ -4,3°.
Warning:
MotoCalc was unable to determine a throttle setting for hands-off cruise
airspeed, so the best lift-to-drag ratio airspeed and throttle setting
will be used instead.
Inability to determine a throttle setting for an airspeed usually means
the model is not capable of reaching the required speed with the given
power system, or the airfoil information has not been specified correctly.
Possible Power System Problems:
The full-throttle motor current at the best lift-to-drag ratio airspeed
(36,7A) is lower than the motor's maximum efficiency current (47,8A). A
higher current level would improve system efficiency.
Current can be increased by using more cells, a larger diameter or
higher pitched propeller, a lower gear ratio, or some combination of
these methods.
Power System Notes:
The voltage (35,5V) exceeds 12V. Be sure the speed control is rated for
at least the number of cells specified above.
Possible Aerodynamic Problems:
The static pitch speed (26m/s) is less than 2,5 times the stall speed
(12m/s), which may result in reduced performance at typical flying
speeds and a low maximum speed. This situation is usually acceptable for
an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller
diameter propeller, a higher cell count, or some combination of these
methods.
The model's maximum level flight speed (17,5m/s) is less than one and a
half times the stall speed (12m/s). With such a narrow range of flying
speeds, the model will require careful piloting in order not to stall.
Maximum speed can be increased by using a higher pitched and/or smaller
diameter propeller, a higher cell count, or some combination of these
methods.
Stall speed can be reduced by reducing weight, increasing the wing area,
or using a thicker and/or more cambered airfoil.
The diameter (20,0in) to pitch (8,0in) ratio is greater than 2:1, which
will result in reduced propeller efficiency at flying speeds. An
appropriate smaller diameter, higher pitched propeller would improve this.
Aerodynamic Notes:
Due to some of the potential problems listed above, this model may
require an experienced pilot.
The static thrust (10885g) to weight (16141g) ratio is 0,67:1, which
will result in short take-off runs, and no difficulty taking off from
grass surfaces (assuming sufficiently large wheels).
At the best lift-to-drag ratio airspeed, the excess-thrust (2783g) to
weight (16141g) ratio is 0,17:1, which will give good climbs and
acceleration. This is a good in-flight thrust to weight ratio for a
basic trainer.
General Notes:
This analysis is based on calculations that take motor heating effects
into account.
These calculations are based on mathematical models that may not account
for all limitations of the components used. Always consult the power
system component manufacturers to ensure that no limits (current, rpm,
etc.) are being exceeded.
--
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