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Erik Dahl
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 10:57

Hej Jørn,

Tusind tak!

Efter at have snakket med Stig, har jeg valgt at købe det Funcub tuningssæt som han havde til salg. Det er en Himax 3522 990kv motor der vejer 165 gram / 990kv. Det leveres med en 13x4 propel, og jeg regner med, at der istedet skal en 12x5 propel på (hvis jeg kan finde en?) eller en 12x6. Gerne en træpropel med kantede tipper :D
Jeg er klar over at der absolut er max power nok, så jeg må reducere kraften, enten med en propel med den rigtige stigning:
a) stor nok stigning, så jeg kan få en forskel i flyvefart mellem langsom/stall-ish og "fuld" fart.
b) lille nok stigning, så jeg kan begrænse det maksimale A-forbrug, og så jeg ikke får en vild maks fart
c) måske en 11x5-6-7 der skalamæssigt er lidt for lille, men måske bedre passer modelflyvemæssigt?

eller ved at reducere i senderen så jeg ikke bruger toppen af kraften.

Måske en kombination.

Uanset hvad, så regner jeg med at jeg kan få nok flyvetid med 3S 2700 mAh til at jeg kan prutte rundt i lang nok tid ved omkring 50%? Måske 3s 3-3500 mAh eller mere istedet for bly i næsen :D

Tusind tak for hjælpen allesammen. Jeg er nu endt med et motorvalg m.m. Det betyder, at når jeg modtager motoren, kan jeg tegne kroppens næsekonstruktion færdig med motorspant og batteri installation og RC-plads. Så skal der bygges, og så vender jeg tilbage med en evaluering af hvordan træk-virkeligheden blev, når jeg har bygget færdig :D
Erik Dahl Christensen / "The Bart Bird man" aka Dr. Dahl / Droneforening Fyn / bredt engageret modelflyver :D
Vi kan hvad vi vil - hvis vi vil! / Gør noget, og gør det sjovt!
 
OY4658
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 14:01

Jeg har ikke modtaget din adresse.
Stig
Mørkøv
Holbæk Modelflyveklub, Knabstrup
 
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Erik Dahl
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 14:10

Hej Stig,
Jeg har sendt dig en SMS med adresse. Den er åbenbart ikke gået igennem i går via besked??

Mvh
Erik
Erik Dahl Christensen / "The Bart Bird man" aka Dr. Dahl / Droneforening Fyn / bredt engageret modelflyver :D
Vi kan hvad vi vil - hvis vi vil! / Gør noget, og gør det sjovt!
 
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JornWildt
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 16:50

Så skal du da ikke snydes for MotoCalc beregningerne (jeg er selv nysgerrig).

MotOpinion - Volksplane VP-1
50m above Sea Level, 101,3kPa, 14,7°C

Max speed: 13.5 m/s, kan ikke flyve ved 65% throttle.

Motor: Himax HC3522 990; 990rpm/V; 2,2A no-load; 0,027 Ohms.
Battery: FlightPower 3700 (20C); 3 cells; 3700mAh @ 3,7V; 0,0037 Ohms/cell.
Speed Control: Dualsky XC-40-MR; 0,0042 Ohms; High rate.
Drive System: Volksplane VP-1; 12x5 (Pconst=1,31; Tconst=0,95) direct drive.
Airframe: Volksplane VP-1; 45dm²; 2685g; 59,7g/dm²; Cd=0,054; Cl=0,42; Clopt=0,66; Clmax=1,2.
Stats: 162 W/kg in; 129 W/kg out; 9,3m/s stall; 12,5m/s opt @ 95% (21:00, 44°C); 15,7m/s level; 1,02m/s @ 4,7°; -1,32m/s @ -6°.

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 (16,4A) is lower than the motor's maximum efficiency current (29,7A). A higher current level would improve system efficiency.
The static full-throttle current (41,6A) exceeds the capability of the specified speed control (40A), which will most likely damage it.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.
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.
Due to the conflicting suggestions to both increase and decrease the current, this particular combination of power system components is not ideal (but not necessarily unusable).

Possible Aerodynamic Problems:

The static pitch speed (18,5m/s) is much less than 2,5 times the stall speed (9,3m/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.
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 (13m/s) is less than one and a half times the stall speed (9,3m/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 (12,0in) to pitch (5,0in) 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 (1963g) to weight (2685g) ratio is 0,73:1, which will result in very short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and steep climb-outs.
At the best lift-to-drag ratio airspeed, the excess-thrust (284g) to weight (2685g) ratio is 0,11:1, which will give slow climbs and low acceleration. Some piloting experience would be beneficial.

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.
Har crashet både det ene og det andet, men er efterhånden gode venner med de fleste af mine fly.
Medlem af EFK87.
 
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JornWildt
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 16:52

MotOpinion - Volksplane VP-1
50m above Sea Level, 101,3kPa, 14,7°C

Max speed: 17.5 m/s. Kan flyve ca. 33 min. ved 65% throttle (11 m/s - meget tæt på stall)

Motor: Himax HC3522 990; 990rpm/V; 2,2A no-load; 0,027 Ohms.
Battery: FlightPower 3700 (20C); 3 cells; 3700mAh @ 3,7V; 0,0037 Ohms/cell.
Speed Control: Dualsky XC6018BA; 0,0022 Ohms; High rate.
Drive System: Volksplane VP-1; 12x6 (Pconst=1,31; Tconst=0,95) direct drive.
Airframe: Volksplane VP-1; 45dm²; 2720g; 60,4g/dm²; Cd=0,054; Cl=0,42; Clopt=0,66; Clmax=1,2.
Stats: 176 W/kg in; 135 W/kg out; 9,3m/s stall; 12,6m/s opt @ 72% (24:51, 39°C); 15,8m/s level @ 88% (17:49, 45°C); 4,29m/s @ 19,9°; -1,32m/s @ -6°.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (37,1A) falls approximately between the motor's maximum efficiency current (29,4A) and its current at theoretical maximum output (197,5A), thus making effective use of the motor.

Possible Aerodynamic Problems:

The static pitch speed (21,3m/s) is less than 2,5 times the stall speed (9,3m/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.

Aerodynamic Notes:

With a wing loading of 60,4g/dm², a model of this size will have trainer-like flying characteristics. It would make an ideal trainer, for use in calm to light wind conditions.
The static thrust (1995g) to weight (2720g) ratio is 0,73:1, which will result in very short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and steep climb-outs.
At the best lift-to-drag ratio airspeed, the excess-thrust (913g) to weight (2720g) ratio is 0,34:1, which will give strong climbs and rapid acceleration. This model will most likely readily loop from level flight, and have sufficient in-flight thrust for many aerobatic maneuvers.

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.
Har crashet både det ene og det andet, men er efterhånden gode venner med de fleste af mine fly.
Medlem af EFK87.
 
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JornWildt
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 16:59

Med en 13x4 propel mener MotoCalc at den slet ikke kan flyve :-) Så det skal nok tages med et stort gran salt. Omvendt, så vejer en FunCub kun 1100g, så motoren er ikke nødvendigvis fantastisk til 2500g med samme propel.
Har crashet både det ene og det andet, men er efterhånden gode venner med de fleste af mine fly.
Medlem af EFK87.
 
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Arvid
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 18:35

Himax
himax.JPG

himax.JPG
Vedhæftede filer
himax1.JPG
Mvh.
Arvid
 
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Erik Dahl
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Re: Volksplane VP-1 skala ca 1:4,5 -> elmotor til skalaflyvning?

08 nov 2017 18:38

Hej Jørn,
Tusind tak! !
Jeg (tror) jeg kan læse følgende:
a) Det går nok med en 12x6 propel. Evt. lidt mindre diameter og 7" i stigning?
b) Der er nok flyvetid med 3700mAh. Det må blive behovet for at afbalancere flyet? der skal afgøre kapaciteten.
c) Det vil hjælpe at bygge let. Der vil/bør være forskel på en model der vejer 1600, 1800, 2000, 2500 eller 2750 gram. Vægten kan få indflydelse på propelvalget. Det er ikke sandsynligt at vægten kan ses som skala- flyvehastighed, men vægten har indflydelse på mindste-farten.
Erik Dahl Christensen / "The Bart Bird man" aka Dr. Dahl / Droneforening Fyn / bredt engageret modelflyver :D
Vi kan hvad vi vil - hvis vi vil! / Gør noget, og gør det sjovt!