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-   -   enough power? (http://www.Wattflyer.com/forums/showthread.php?t=72865)

wheelholder 12-27-2013 03:03 AM

enough power?
 
Built a delta out of coroplast. It is 21 inches long, and 18 inches wide. CG is approx 7" from nose box. I have a park 300 motor for it. Weight is at the top end of the recommended weight according to the rim fire paperwork for a sport flyer.

Have not tried to fly yet as wind has been blowing and time has not been on my side.

Before I destroy the plane, am wondering if the motor has enough power. It has an eflite 3s 1500 mah battery.

Any suggestions or thoughts would be appreciated.

fhhuber 12-27-2013 03:31 AM

Sounds like it should have enough power to fly... but not to fly well. Its rarely fun to have a plane with marginal power.

Then comes the question of just how heavy you really are vs the wing area. If you combine marginal power:weight with high wing loading and you have a real challenge.

CHELLIE 12-27-2013 06:06 AM

How much does the delta weigh ? coroplast is heavy stuff, a 400 to 450 motor IMHO would be better to use. use a 7x6 prop with the 400 motor below if your AUW is between 12 to 32 oz if its heavier use a 450 motor.

http://www.headsuphobby.com/Firepowe...otor-C-656.htm


http://www.headsuphobby.com/Power-Up...otor-F-745.htm

CHELLIE 12-27-2013 06:16 AM

with Rimfire motors, only use a GP esc with them, Rimfire motors dont tend to like other MFG ESC, so its best to keep the rimfire motor and esc matched with the same MFG.

fhhuber 12-27-2013 06:24 AM

I have never had issues with Rimfire motors using Castle ESCs.

CHELLIE 12-27-2013 07:06 AM

Quote:

Originally Posted by fhhuber (Post 935337)
I have never had issues with Rimfire motors using Castle ESCs.

some people have had issues with rimfire motors and cc esc, you need to use the lowest timing on the cc esc, something to do with the feedback pulse from the motor to the ESC,

kyleservicetech 12-27-2013 07:03 PM

Quote:

Originally Posted by wheelholder (Post 935322)
Built a delta out of coroplast. It is 21 inches long, and 18 inches wide. CG is approx 7" from nose box. I have a park 300 motor for it. Weight is at the top end of the recommended weight according to the rim fire paperwork for a sport flyer.

Have not tried to fly yet as wind has been blowing and time has not been on my side.

Before I destroy the plane, am wondering if the motor has enough power. It has an eflite 3s 1500 mah battery.

Any suggestions or thoughts would be appreciated.

As a very rough estimate, you'd want to run about 150 watts per pound of airplane for good flying performance. So, if your model weighs two pounds, that would require some 300 watts up front.

There are a lot of variables here. Among them is the type of airfoil. Is it symetrical? flat bottom, no airfoil (Flat sheet)?

If you're flying a Piper Cub type of floater, often just 75 to 100 watts of power per pound of airplane will work, assuming proper motor and propeller size.

As an example, the Cub would require a larger diameter, low pitch, slow turning prop. That, in comparison to a very fast model that would require a smaller diameter, higher pitch, and high RPM on the prop. And, both could be running the same watts into the motor.

With your 1500 Mah 3S battery, perhaps a maximum current of 20 amps would be appropriate. So, at 3.5 Volts per cell, your power would be 20 Amps times 3.5 Volts per cell times 3 cells, or 210 watts. At full power for the entire flight, that would give about 4 minutes flying time on a fully charged battery. Reducing power to about 75% can easily double your flying time.

There are a number of good computer programs for this type of issue. Castle Creations has a free one on their website. www.motocalc.com is another good one. It's free for 30 days, then $39.00

Hope this helps.

wheelholder 12-28-2013 12:24 AM

2 Attachment(s)
Thanks for the replies. I guess it would have helped if I had included the weight and area of the wing.

Overall weight including battery is 395 gr or 14 5/8 oz. I calculated wing area and is 278 sq in. It is also a flat wing. No airfoil.

On the website for the rimfire, it says sport flying realm is 395 gr. And constant output for the motor is 100 watts. With the specs for the motor, it appears to me it will not be a hot rod, but should fly. Just wanted to run it by people with more experience than me.

Attached are a couple of pics.

Thanks again for the help

Attachment 172610

Attachment 172611

gramps2161 12-28-2013 12:40 AM

That little Delta should fly fine with that setup. It has no profile not going to be much drag at all. I bet you will find it scoots right along with your setup. :)
Have fun with it nice looking delta.

By the way here is a great thread on power system's.

http://www.wattflyer.com/forums/showthread.php?t=18521

kyleservicetech 12-28-2013 12:45 AM

2 Attachment(s)
Quote:

Originally Posted by wheelholder (Post 935382)
Thanks for the replies. I guess it would have helped if I had included the weight and area of the wing.

Overall weight including battery is 395 gr or 14 5/8 oz. I calculated wing area and is 278 sq in. It is also a flat wing. No airfoil.

On the website for the rimfire, it says sport flying realm is 395 gr. And constant output for the motor is 100 watts. With the specs for the motor, it appears to me it will not be a hot rod, but should fly. Just wanted to run it by people with more experience than me.
Attached are a couple of pics.

Thanks again for the help

Just ran the numbers through www.motocalc.com. Running the Park 300 motor, this motor would only provide a climb rate of 300 feet per minute. OK, but is something rather unspectacular.

Motocalc suggests this model should fly OK with a Rimfire motor shown in the attached printouts. Rate of climb is good at 1000 Feet Per Minute using the Rimfire motor listed. Rimfires don't have a good reputation for reliability in this website. Hacker motors are quite a bit more expensive, and they will work. A Hacker A20-20L is in the same ballpark as the Rimfire motor listed.

https://www.aero-model.com/8_64/Brus...20-Series.html (Yup, they are expensive, but only $5.00 more than the Rimfire)

Interesting, these Park motors, and Hackers are within a few $$$$ of each other.
http://www.horizonhobby.com/webapp/w...pe=productgrid

Then there are some really low cost China import motors also available.


Take a look at the screen dumps from www.motocalc.com.

wheelholder 12-28-2013 01:31 AM

I guess I gave incorrect info on the motor. it is a rimfire , not park 300. Not sure if that makes any difference. Looked at the screen dump attachment. Looked at my motor and it shows 28-22-1380 on the can. I would guess it produces a bit more thrust than the one you ran through moto-calc. not sure though.

Gramps, ( I am one also) thanks for the compliment. I figured coroplast would be stronger than foam board just in case it hits the ground harder than it should. ( Like that has never happened to me before)

Thanks again for the help. The weather ever clears up and wind dies down, I am going to throw it in the air and see what happens.

kyleservicetech 12-28-2013 01:37 AM

Quote:

Originally Posted by wheelholder (Post 935388)
I guess I gave incorrect info on the motor. it is a rimfire , not park 300. Not sure if that makes any difference. Looked at the screen dump attachment. Looked at my motor and it shows 28-22-1380 on the can. I would guess it produces a bit more thrust than the one you ran through moto-calc. not sure though.

Gramps, ( I am one also) thanks for the compliment. I figured coroplast would be stronger than foam board just in case it hits the ground harder than it should. ( Like that has never happened to me before)

Thanks again for the help. The weather ever clears up and wind dies down, I am going to throw it in the air and see what happens.

Yup
Just ran the numbers through motocalc on the 28-22-1380 motor. Motocalc suggests a 7X4 electric prop. Results are about 10K RPM, Rate of climb at 380 feet per minute, which should be OK for a little model.

cyclops2 01-26-2014 06:50 PM

Hold everything !!
 
What happened to when we could fly a plane on 40 to 60 watts per pound ? with brushed motors.

150 watts is straight up with todays high efficiency stuff. :D

hayofstacks 01-26-2014 10:52 PM

slow stick with nicad weighed in at 18oz and had a whole 80 watts.

kyleservicetech 01-27-2014 01:47 AM

Quote:

Originally Posted by cyclops2 (Post 938165)
What happened to when we could fly a plane on 40 to 60 watts per pound ? with brushed motors.

150 watts is straight up with todays high efficiency stuff. :D

Yup
Nowdays, most guys that fly electric models want a model that has the same power and performance as a glow powered model airplane. That power value also happens to be around 100-150 watts per glow powered model airplane.

wheelholder 03-04-2014 03:00 AM

Finally flew the wing. It is slightly unstable when hand launching, but after building up a bit of speed, it flies pretty well.

It rolls better to the right than the left. I think I am going to reduce the size of the stabilizers. Hope that helps the flight out some.

With the rimfire 300 on it, just seems to need a bit more power. It flies rather sedately.

Just a short update on the wing.

To answer my own question, YES it has enough power.

sidybee 03-04-2014 03:24 AM

not to cut in on this ,, but how do you glue and what type of glue do you glue that pasticy stuff with id like to try and build one of them fancy smacy flying thingy me bobs
one day...just for kicks

wheelholder 03-04-2014 04:19 AM

On this wing, I used hot glue for the coroplast. I used epoxy to glue the motor mount that i made out of lite plywood.

Just be careful if you use coroplast. As others have said, it is a bit heavy and will affect the flying characteristics.

solentlife 03-04-2014 08:00 AM

Strange ... most models roll better to LEFT because of motor / prop torque aids to the left but opposes rotation to right.

Nigel

nuteman 03-05-2014 12:17 PM

Quote:

Originally Posted by wheelholder (Post 941438)
I think I am going to reduce the size of the stabilizers.

Yeah, they look about double the size they need to be. So you'll reduce weight by cutting those down, which will improve wing loading, which will lower stall speed.

wheelholder 03-06-2014 01:09 AM

Yeah, I just guessed at to what size to make the whole wing. After I cut them down and see how it flies, will post an update. Maybe this weekend I can get back to the field.


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