Originally Posted by AscotRC

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.

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

Originally Posted by AscotRC

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.

Originally Posted by aeromaniac

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.

Originally Posted by scirocco

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.

Originally Posted by aeromaniac

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.

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.

Originally Posted by Watdazit

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.

Originally Posted by Watdazit

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?

Originally Posted by Watdazit

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!

Originally Posted by aeromaniac

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 ? : )

Originally Posted by AscotRC

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

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.

Originally Posted by peterreebok

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.

Originally Posted by scirocco

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.