power for fokker triplane 20" span
12-19-2002, 01:15 PM
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power for fokker triplane 20" span
I'm trying to figure out what batteries I need and motor for a fokker triplane 20" wingspan.
I know it's a tiny plane...it was designed for rubber or CL but I want to make it radio.
I just don't know what voltage/mah for the batteries and the type of motor I need.
I know it's a tiny plane...it was designed for rubber or CL but I want to make it radio.
I just don't know what voltage/mah for the batteries and the type of motor I need.
12-19-2002, 03:49 PM
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power for fokker triplane 20" span
I have only converted one plane so far, but here is what I did.
Mine was a model of an ultralight so I knew it needed to have a light wing loading to fly realistically. I started off with a desired WL of 5 oz / sq ft. Using the wing area (it will be harder with a tri as you loose some of the effective WA) I came up with a target RTF weight of 7 oz.
Figuring that it would need at least 1/2 it's weight in thrust, I was able to get away with a gear-driven GWS IPS. After adding up the weight of all the components I found that it would only be able to carry a 6 cell 110 Nicad or a 7 cell 300 NiMh.
My numbers were right as it flies well.
One suggestion is to end up with a lighter RTF plane than you think you need and subtract 10 to 20 % off the performance numbers for the motor.
On a full charge, with a warm NiMh battery my plane takes off with authority, flies on 5/8 throttle and stays in the air for 15 minutes. With a cold battery it will take off, but only has enough power to stay up for 1 minute. The motor still runs for 15 minutes, but it just doesn?t have the thrust to keep the plane airborne.
Good luck
Mine was a model of an ultralight so I knew it needed to have a light wing loading to fly realistically. I started off with a desired WL of 5 oz / sq ft. Using the wing area (it will be harder with a tri as you loose some of the effective WA) I came up with a target RTF weight of 7 oz.
Figuring that it would need at least 1/2 it's weight in thrust, I was able to get away with a gear-driven GWS IPS. After adding up the weight of all the components I found that it would only be able to carry a 6 cell 110 Nicad or a 7 cell 300 NiMh.
My numbers were right as it flies well.
One suggestion is to end up with a lighter RTF plane than you think you need and subtract 10 to 20 % off the performance numbers for the motor.
On a full charge, with a warm NiMh battery my plane takes off with authority, flies on 5/8 throttle and stays in the air for 15 minutes. With a cold battery it will take off, but only has enough power to stay up for 1 minute. The motor still runs for 15 minutes, but it just doesn?t have the thrust to keep the plane airborne.
Good luck
12-19-2002, 05:50 PM
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power for fokker triplane 20" span
That's great....how do I find out the wing loading, and target RTF weight?...also the amount of power the motor needs to produce the right amount of thrust... That's the critical information i'm really needing to know I guess.
It says on the box 137 sq inch of wing area....that sounds pretty low for 3 separate wings.
Thanks anyway
It says on the box 137 sq inch of wing area....that sounds pretty low for 3 separate wings.
Thanks anyway
12-19-2002, 07:55 PM
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power for fokker triplane 20" span
how do I find out the wing loading, and target RTF weight?...also the amount of power the motor needs to produce the right amount of thrust... That's the critical information i'm really needing to know I guess.
It says on the box 137 sq inch of wing area....that sounds pretty low for 3 separate wings.
I know just enough about this to get myself into real trouble.
Starting with the WA. On a (straight winged) monoplane you multiply the chord X the span (minus the width of the fuselage). On a multiplane you would add up the total of the three wings. I would then multiply the total WA X .75% as multiplanes are less efficient then Mono's.
On the Astro Flight site, Bob says you need 40 - 50 Watts per lb of plane for normal flight. I have read that this doesn't apply directly to Parkfliers, but it is still a good place to start.
As an example, An IPS can produce 14 Watts of power. That would mean that your planes' RTF weight could only be 6.5 oz. I know this isn't totally true because my Desert Duster, with 200 si WA weighs 7 oz and flies great on an IPS-2.
I'm afraid that your plane might need the real light radio gear that
http://www.mentornet.org/Sky.htm
sells.
I hope one of the E-geeks (said with great respect) will join in as they have the experience that will help you get that little bird in the air.
Keep us posted.
It says on the box 137 sq inch of wing area....that sounds pretty low for 3 separate wings.
I know just enough about this to get myself into real trouble.
Starting with the WA. On a (straight winged) monoplane you multiply the chord X the span (minus the width of the fuselage). On a multiplane you would add up the total of the three wings. I would then multiply the total WA X .75% as multiplanes are less efficient then Mono's.
On the Astro Flight site, Bob says you need 40 - 50 Watts per lb of plane for normal flight. I have read that this doesn't apply directly to Parkfliers, but it is still a good place to start.
As an example, An IPS can produce 14 Watts of power. That would mean that your planes' RTF weight could only be 6.5 oz. I know this isn't totally true because my Desert Duster, with 200 si WA weighs 7 oz and flies great on an IPS-2.
I'm afraid that your plane might need the real light radio gear that
http://www.mentornet.org/Sky.htm
sells.
I hope one of the E-geeks (said with great respect) will join in as they have the experience that will help you get that little bird in the air.
Keep us posted.
12-19-2002, 10:12 PM
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E- Geek
The way to get information on setting up power systems for electric flight is to get one of two programs that are made for this. I use "Electricalc"( $39) but "Motocalc" is just as good and you can download and use it for 30 days free. Just type in Motocalc on your search. I have spend 100's of hours playing with this program figuring out "what if I did this" I fly only electrics now and love it. I have trouble flying small planes so I keep mine over 50 inch wingspans up to 9 1/2 lbs. 20 inch span is tiny even for electric. I imagine you will end up with a geared speed 280 and 8 nimh cells and a" gws" receiver. Do not try to fly a plane this small in ANY wind at all! If you do not have anyone to help ou figure all this out you have a lot of homework to do to get it right. Electrics are simple once set up but setting one up is very complex. Much more so than fueled acft. Hobby lobby is a good source for electric stuff. If you were to fly your plane free flight you might try a co2 engine. They come VERY small and light. Good luck.
12-20-2002, 02:59 PM
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power for fokker triplane 20" span
