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Old Dec 02, 2012, 12:59 PM
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Trainer foamie help

Hi, I have ventured into your wonderful world of RC planes from Helis and am struggling with the power setup. I have built the plane below from plans however the author did not provide any suggested prop/motor/esc/battery suggestion and after 2 attempts at different setups I have only just managed to get a short flight (which was quite challenging as was obviously constantly on the verge of stalling!).
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So far the most success has been had with a 6x3 prop, 10A flyfun ESC, 2800 Kva polymer outrunner and a 645Mah 2S

The plane has a 30" wing span and has been made in 1/4" foam (depron) so quite light.

Any suggestions for a setup that will work (i'm happy to play with prop pitches etc. once I can get it to fly!)?

Here is the designer flying the plane on youtube
Easy pusher trainer foamy (2 min 24 sec)


Craig
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Old Dec 02, 2012, 01:01 PM
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read the forum

I have read the sticky on power systems but just looking for a suggested (tried & tested) setup for a lightweight trainer.

Craig
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Old Dec 02, 2012, 02:17 PM
Hot glue held together by foam
United States, WA, Vancouver
Joined Aug 2010
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Originally Posted by craigdiver View Post
Hi, I have ventured into your wonderful world of RC planes from Helis and am struggling with the power setup. I have built the plane below from plans however the author did not provide any suggested prop/motor/esc/battery suggestion and after 2 attempts at different setups I have only just managed to get a short flight (which was quite challenging as was obviously constantly on the verge of stalling!).
Attachment 5344660

So far the most success has been had with a 6x3 prop, 10A flyfun ESC, 2800 Kva polymer outrunner and a 645Mah 2S

The plane has a 30" wing span and has been made in 1/4" foam (depron) so quite light.

Any suggestions for a setup that will work (i'm happy to play with prop pitches etc. once I can get it to fly!)?

Here is the designer flying the plane on youtubehttp://youtu.be/7kFK0YvNVQs

Craig
When your plane was " constantly on the verge of stalling " do you think it was from being underpowered , or from being tail heavy ?

If you think it was tail heavy , try moving your battery forward and/or getting a bigger ( heavier ) battery .

If you think it was underpowered , check the specs for the motor to see if it will run on a 3s battery and what prop for 3s . If it can , get a 3s battery - that will increase the RPM's and give you more power . But you'll have to use a smaller prop ( what they recommend for 3s ) so you don't toast the motor/ESC .

If you think you need to get a more powerful motor , check the specs on your current motor to see what the watt rating is , and then get another motor with a 50% higher watt rating and roughly the same kv . Always use the recommended ESC/prop/battery .
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Old Dec 02, 2012, 03:55 PM
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Originally Posted by balsa or carbon View Post
When your plane was " constantly on the verge of stalling " do you think it was from being underpowered , or from being tail heavy ?

If you think it was underpowered , check the specs for the motor to see if it will run on a 3s battery and what prop for 3s . If it can , get a 3s battery - that will increase the RPM's and give you more power . But you'll have to use a smaller prop ( what they recommend for 3s ) so you don't toast the motor/ESC .

If you think you need to get a more powerful motor , check the specs on your current motor to see what the watt rating is , and then get another motor with a 50% higher watt rating and roughly the same kv . Always use the recommended ESC/prop/battery .
I'm pretty sure it was underpowered, I paid quite a bit of time ensuring the COG was around 40% of the chord and plane when flying appeared quite slow (compared to one on youtube video)

My motor is a very cheap hobbyking polymer motor which although very light would fry on 3s, please can you recommend a decent motor kv to drive a 6x3 prop on 3s (and what size of battery should I be looking at for a 10min flying time on a lightweight trainer)?

Thanks in advance.......
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Old Dec 02, 2012, 04:44 PM
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Originally Posted by craigdiver View Post
I'm pretty sure it was underpowered, I paid quite a bit of time ensuring the COG was around 40% of the chord and plane when flying appeared quite slow (compared to one on youtube video)

My motor is a very cheap hobbyking polymer motor which although very light would fry on 3s, please can you recommend a decent motor kv to drive a 6x3 prop on 3s (and what size of battery should I be looking at for a 10min flying time on a lightweight trainer)?

Thanks in advance.......
Craig,
It always helps to provide links to parts like your motor and the plane. That way we have the specs for the part(s) to reference. Going to a 3S battery will not fry your motor. At least not from the additional voltage. From the picture I think it will do nicely on a 3S battery but I would need to see the specs to be certain. The motor specs should also recommend a prop and battery.

That plane is a bit unconventional for a trainer. Being a low wing it is going to be less stable than a high wing design. 40% of the cord is a bit far back for a correct CG. Is that what the design calls for?

Glen
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Old Dec 02, 2012, 07:26 PM
Hot glue held together by foam
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Originally Posted by craigdiver View Post
I'm pretty sure it was underpowered, I paid quite a bit of time ensuring the COG was around 40% of the chord and plane when flying appeared quite slow (compared to one on youtube video)

My motor is a very cheap hobbyking polymer motor which although very light would fry on 3s, please can you recommend a decent motor kv to drive a 6x3 prop on 3s (and what size of battery should I be looking at for a 10min flying time on a lightweight trainer)?

Thanks in advance.......
40% of chord CG sounds too far back , I would start with the CG at about 25%-30% . Planes will usually fly OK with a slightly forward CG , but are usually difficult to fly if the CG is too far back .

I use these combos ( motor with matching ESC ) from HobbyPartz a lot , here's a couple that might work for you with a 6x3 prop :

Lot's of power http://www.hobbypartz.com/98p-mars-b...20a-combo.html

Even MORE power http://www.hobbypartz.com/98p-mars-b...30a-combo.html I use this one on my Dollar Tree foam jets with a 6x4 prop .
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Old Dec 04, 2012, 05:01 AM
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yes, 40% chord is way too far back. as balsa or carbon recommended 25-30% is the norm.
also you may want to add some up wash on the motor, (a washer under the bottom 2 motor mounts would surfice) as this would provide some directed thrust, as your motor is nearly pointing level,
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Old Dec 04, 2012, 11:52 AM
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Originally Posted by insomaniac45 View Post
yes, 40% chord is way too far back. as balsa or carbon recommended 25-30% is the norm.
also you may want to add some up wash on the motor, (a washer under the bottom 2 motor mounts would surfice) as this would provide some directed thrust, as your motor is nearly pointing level,
I'm inclined to agree. Check out the thrust angle in the video.
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Old Dec 04, 2012, 12:41 PM
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Getting there......

What can I say guys but a huge thank you,

I am going to buy the following (i'm in Scotland, UK), any comments before I proceed.....
Motor http://www.ebay.co.uk/itm/110853350559
Battery Turnigy 3S 1000mAh
Recommends 20A ESC which I already have
a 5x5 prop was recommended but seems scarce in the UK so going to use a 6x4 (i'm sure I read they are a direct swap).

Thanks again,

Craig
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Old Dec 04, 2012, 12:49 PM
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What can I say guys but a huge thank you,

I am going to buy the following (i'm in Scotland, UK), any comments before I proceed.....
Motor http://www.ebay.co.uk/itm/110853350559
Battery Turnigy 3S 1000mAh
Recommends 20A ESC which I already have
a 5x5 prop was recommended but seems scarce in the UK so going to use a 6x4 (i'm sure I read they are a direct swap).

Thanks again,

Craig
Several have mentioned CG but you did not state you would be adjusting. Start at 30% of chord and it should fly well. After that you can adjust SLIGHTLY towards rear to obtain flight characteristics you like. I would never reccomend anything more than 33% unless you are highly skilled and need more for extremely snappy 3D.
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Old Dec 04, 2012, 01:36 PM
Hot glue held together by foam
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Originally Posted by craigdiver View Post
What can I say guys but a huge thank you,

I am going to buy the following (i'm in Scotland, UK), any comments before I proceed.....
Motor http://www.ebay.co.uk/itm/110853350559
Battery Turnigy 3S 1000mAh
Recommends 20A ESC which I already have
a 5x5 prop was recommended but seems scarce in the UK so going to use a 6x4 (i'm sure I read they are a direct swap).

Thanks again,

Craig
That motor should give you plenty of power .
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Old Dec 04, 2012, 01:44 PM
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Originally Posted by Daytonarc View Post
Several have mentioned CG but you did not state you would be adjusting. Start at 30% of chord and it should fly well. After that you can adjust SLIGHTLY towards rear to obtain flight characteristics you like. I would never reccomend anything more than 33% unless you are highly skilled and need more for extremely snappy 3D.
Yes, I will definitely move the CG to 25-30% of the chord (I presume 0% is at the front of the wing, leading edge and 100% at the rear, trailing edge)? I certainly do not want any snappy handling on my first flights!

I will also as recommended put a couple of washers under the bottom motor mounts to angle the motor up slightly.

Thanks

Craig
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Old Dec 04, 2012, 01:45 PM
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That motor should give you plenty of power .
Is 6x4 correct prop choice?
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Old Dec 04, 2012, 01:50 PM
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Yes, (I presume 0% is at the front of the wing, leading edge and 100% at the rear, trailing edge)? CORRECT TAKE MEASUREMENT AT WING FUESALAGE JOINTCraig
I would try with the CG adjusted with your new power before I added any up thrust.
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Old Dec 04, 2012, 03:09 PM
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Originally Posted by craigdiver View Post
Is 6x4 correct prop choice?
Yes , if you look at the specs for that motor they recommend a 6x5 , so a 6x4 will be fine . You can always under prop ( from the recommended ) , you don't want to ever over prop .
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