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Old Nov 07, 2012, 05:10 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,846 Posts
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Originally Posted by AscotRC View Post
So the boomer doesn't need metal gears or higher torque?
Thanks Aero
Lol no but it needs reliable servos and you can always move them to the next model and at that price why not a little over kill.
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Old Nov 07, 2012, 05:13 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,846 Posts
I just received the stick 1500 and am putting the metal gear on elevator and the standard ones on the ailerons, 4.3kg is not high torque just a standard servo power. Lol
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Old Nov 07, 2012, 06:45 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,846 Posts
Quote:
Originally Posted by AscotRC View Post
So the boomer doesn't need metal gears or higher torque?
Thanks Aero
Yes your right, but being a fitter and turner/ toolmaker, I tend to over engineer my stuff if possible. Works for me because I have fewer failures.
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Old Nov 07, 2012, 09:52 PM
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Australia, ACT, Kambah
Joined Feb 2001
3,283 Posts
Quote:
Originally Posted by aeromaniac View Post
There has being a lot of useful information posted in this thread, the old 70watts for a trainer etc, is a guide, that might be 70watts out not in, i believe 100watts in gives ok performance, not outstanding. Always nice to have some reserve power lol.
We have throttle to control the motor power output, remembering diameter is thrust and pitch is speed, and once you model hits pitch speed your amps will drop because your motor is running at minimal load.
I used a 13x4 on a high wing trainer with a 32 sized motor before.
The rules of thumb have always been based on input power, as it is the only power value directly measurable, ie with a wattmeter. Here is the original 1987 article, with "input power" extensively bolded: http://www.theampeer.org/shaw/SCALE.PDF

See this post for an example of how some watts per lb aren't as equal as others: http://www.rcgroups.com/forums/showp...5&postcount=29

So watts/lb is a good start, but also important is knowing prop rpm and how different power systems convert electrical power into thrust.

And of course, performance is subjective, so if it will fit and work and not cost too much, and not produce adverse effects such as weight and balance, why not add extra power.
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Old Nov 07, 2012, 10:00 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,846 Posts
Quote:
Originally Posted by scirocco View Post
The rules of thumb have always been based on input power, as it is the only power value directly measurable, ie with a wattmeter. Here is the original 1987 article, with "input power" extensively bolded: http://www.theampeer.org/shaw/SCALE.PDF

See this post for an example of how some watts per lb aren't as equal as others: http://www.rcgroups.com/forums/showp...5&postcount=29

So watts/lb is a good start, but also important is knowing prop rpm and how different power systems convert electrical power into thrust.

And of course, performance is subjective, so if it will fit and work and not cost too much, and not produce adverse effects such as weight and balance, why not add extra power.
Thanks for this info, very much appreciated, I have OBL40 with just under 100 watts per lb and it was ok, it only had a 15-20% climb ratio, so I replaced the motor and then replaced it to a turnigy G46 which gave it good performance.
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Old Nov 08, 2012, 12:09 AM
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Australia, ACT, Kambah
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Quote:
Originally Posted by aeromaniac View Post
Thanks for this info, very much appreciated, I have OBL40 with just under 100 watts per lb and it was ok, it only had a 15-20% climb ratio, so I replaced the motor and then replaced it to a turnigy G46 which gave it good performance.
My Kadet LT-25 currently has about 105W/lb, takeoff half throttle, go to full throttle, pull to vertical for about 200 feet before it slows down much. Big loops, cubans etc only take 2/3 to 3/4 throttle. It's on a 13x8 and I know the motor efficiency is well over 80% as I get actual rpm and current almost spot on the predicted rpm and current.

150W/lb into a 16x12, also at high efficiency, makes my Wind S just keep accelerating vertically. Serious fun! Not that I have any clue how, but apparently that's enough power for all the required pattern sequences.
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Old Nov 11, 2012, 02:06 AM
A geriatric flier
Watdazit's Avatar
Australia, NSW, Braidwood
Joined Nov 2008
967 Posts
After a lot of messing around I have eventually settled on a electric system for my Boomerang.

Motor is an Eflite Power 46
Batteries 4S at present I am using Zippy Compacts 25/35C 4000 mAh
Prop is an APC 13 x 8 E
On the watt meter it is returning 38 amps and 571 watts.
I am flying 7 mins at present and showing 45% to 50% left in the battery.

I am a novice so I am not pushing it but as I get more confident undoubtably my flying time will stay the same but I will be using more mAh.

The motor is working way under its potential of 800watts. The closest I have got to using this power is with a 5S setup and 13 x 6.5 prop or a 12 x 8 prop. The flying times were greatly reduced so that's why I decided to go 4S.

I still have not got a handle on all this motor vs prop vs battery thing but I'm flying comfortably at present and have a system I think can grow with me.
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Old Nov 11, 2012, 02:23 AM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,846 Posts
Quote:
Originally Posted by Watdazit View Post
After a lot of messing around I have eventually settled on a electric system for my Boomerang.

Motor is an Eflite Power 46
Batteries 4S at present I am using Zippy Compacts 25/35C 4000 mAh
Prop is an APC 13 x 8 E
On the watt meter it is returning 38 amps and 571 watts.
I am flying 7 mins at present and showing 45% to 50% left in the battery.

I am a novice so I am not pushing it but as I get more confident undoubtably my flying time will stay the same but I will be using more mAh.

The motor is working way under its potential of 800watts. The closest I have got to using this power is with a 5S setup and 13 x 6.5 prop or a 12 x 8 prop. The flying times were greatly reduced so that's why I decided to go 4S.

I still have not got a handle on all this motor vs prop vs battery thing but I'm flying comfortably at present and have a system I think can grow with me.
WTG mate, I have the G46 in the stick 1500 on 4s, maidened today and it flys great, wind was awful so that took some of the enjoyment away, plus the flies lol.
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Last edited by aeromaniac; Nov 11, 2012 at 03:49 AM. Reason: adding pics
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Old Nov 11, 2012, 04:35 AM
Registered User
Australia, VIC, Ferntree Gully
Joined Nov 2010
180 Posts
Quote:
Originally Posted by Watdazit View Post
After a lot of messing around I have eventually settled on a electric system for my Boomerang.

Motor is an Eflite Power 46
Batteries 4S at present I am using Zippy Compacts 25/35C 4000 mAh
Prop is an APC 13 x 8 E
On the watt meter it is returning 38 amps and 571 watts.
I am flying 7 mins at present and showing 45% to 50% left in the battery.

.
I am curious, how does the 13 x 8 prop go re clearance? Did you have to put bigger wheels on it?
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Old Nov 11, 2012, 04:58 AM
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Australia, ACT, Kambah
Joined Feb 2001
3,283 Posts
Quote:
Originally Posted by Watdazit View Post
After a lot of messing around I have eventually settled on a electric system for my Boomerang.

Motor is an Eflite Power 46
Batteries 4S at present I am using Zippy Compacts 25/35C 4000 mAh
Prop is an APC 13 x 8 E
On the watt meter it is returning 38 amps and 571 watts.
I am flying 7 mins at present and showing 45% to 50% left in the battery.

I am a novice so I am not pushing it but as I get more confident undoubtably my flying time will stay the same but I will be using more mAh.

The motor is working way under its potential of 800watts. The closest I have got to using this power is with a 5S setup and 13 x 6.5 prop or a 12 x 8 prop. The flying times were greatly reduced so that's why I decided to go 4S.

I still have not got a handle on all this motor vs prop vs battery thing but I'm flying comfortably at present and have a system I think can grow with me.
Great to hear it's working out well for you!
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Old Nov 11, 2012, 06:26 AM
Dave
Australia, QLD, Brisbane
Joined Apr 2012
136 Posts
Quote:
Originally Posted by aeromaniac View Post
WTG mate, I have the G46 in the stick 1500 on 4s, maidened today and it flys great, wind was awful so that took some of the enjoyment away, plus the flies lol.
Good to hear Aero, maybe a video next flight ? : )
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Old Nov 11, 2012, 06:36 AM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,846 Posts
Quote:
Originally Posted by AscotRC View Post
Good to hear Aero, maybe a video next flight ? : )
I got some video on my mobile but when I put on my pc it doesn't work
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Old Nov 11, 2012, 08:50 AM
Geez That's A Big Fly
Banjofrog's Avatar
Australia, WA, Parkerville
Joined Sep 2011
1,428 Posts
Yeah the bloody flies are bad here too. I am going to use the same set up in the HK Spacewalker as I used in my Boomerang conversation.

Shaun.
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Old Nov 11, 2012, 04:00 PM
A geriatric flier
Watdazit's Avatar
Australia, NSW, Braidwood
Joined Nov 2008
967 Posts
Quote:
Originally Posted by peterreebok View Post
I am curious, how does the 13 x 8 prop go re clearance? Did you have to put bigger wheels on it?
Good question. Yes I have had a problem and broken one prop with a heavy landing. I have not changed the wheels although I have thought about changing the front one only. However at this stage I have left the rear wheels spread a little (from my heavy landings,) which has the effect of lifting the nose. I also put a lot of effort into making perfect landings!

An alternative is to go to a 300mm 3 blade prop. I have looked at posts on sizing these and need to get my grey brain around the maths to work out an equivalent size.
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Old Nov 11, 2012, 04:10 PM
A geriatric flier
Watdazit's Avatar
Australia, NSW, Braidwood
Joined Nov 2008
967 Posts
Quote:
Originally Posted by scirocco View Post
Great to hear it's working out well for you!
Thanks, it was good enough to do my Bronze wings yesterday. My instructor had me do a 2 loops at the end, (celebration??) and the Boomer handled it well. I have done loops, flips and rolls with 800mm wing span HK crash dummy planes so I can do them but doing it with a balsa/ply 1500 ":real" plane was a little bit nerve racking.

Are you going to the Viagra Glider day at Namadgi on Friday? I will be taking my Bixler and Radian Pro. I like gliding but am not very good at it.
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