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RM Aerobat

David Boddington's 1984 Mantlepiece

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Piers Bowlan14/04/2018 07:55:26
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1250 forum posts
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I wouldn't get too hung up on the finish of the formers Mark, as when they are glued in place and everything sanded and covered/painted, no one will know (except you)! There are some great craftsmen on this forum but I am not one of them. It doesn't matter, as long as you enjoy the process and build something.

You can always order in the wood you need (SLEC or The Balsa Cabin) for the hard grade wood or thin ply required.

 

Edited By Piers Bowlan on 14/04/2018 07:56:12

Mark Pidduck14/04/2018 14:44:05
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29 forum posts
7 photos

kc - Many thanks for the additional information. Interesting to consider the variation of power output with variations in prop diameter and pitch. Ah, the Moronic, that brings back some happy memories!

PatMc - Thank you very much for the recommendation. I shall have to invest in a set of circular saw blades.

Piers - This is true, except for the fact that I've taken pictures and shown you all! I have an order placed with a non-local supplier of wood, who offered me the choice of hardness of the sheet material. Not quite the same as being able to compare sheets in person. I work not too far from Avicraft, although unfortunately a detour there after work sees me arrive back home so late I end up in the dog house...

Nigel R14/04/2018 23:53:34
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1296 forum posts
287 photos

Mark if I were building this I would aim for 400w. Roughly a good .25 2 stroke.

if you're not invested in batteries yet I would go for a 3s 3000. They are the best value for money. Then pick the prop you want to use and I'm sure there will be a kind soul who couldfigure the right motor and esc for you.

in happy with the setup I have in the trainer but the 4s 2200 battery was used mainly because I already had a comparable setup in another model.

AndyD15/04/2018 19:13:32
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689 forum posts
503 photos

couldn't resist I cut the aerobat sides,dont know when I shall get round to doing any more though.dscf1517.jpg

PatMc15/04/2018 19:53:38
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3715 forum posts
476 photos
Posted by Nigel R on 14/04/2018 23:53:34:

Mark if I were building this I would aim for 400w. Roughly a good .25 2 stroke.

if you're not invested in batteries yet I would go for a 3s 3000. They are the best value for money. Then pick the prop you want to use and I'm sure there will be a kind soul who couldfigure the right motor and esc for you.

in happy with the setup I have in the trainer but the 4s 2200 battery was used mainly because I already had a comparable setup in another model.

For 400w power I'd go for 4s 2200 rather than 3s 3000. With a 4s battery you can either use a lower rated ESC or the same ESC but under less stress.

Nigel R16/04/2018 14:44:58
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1296 forum posts
287 photos

Pat, a valid point, a smaller 40A ESC can be used with 4S at this sort of power level.

Mark, if it helps:

I ahve measured a 3536/1050kv motor, running on the same 4S 2200 packs I used on the RMT. On a 9x6 prop, It showed (on the wattmeter) approx 450W, with a fresh charge, current was around 30A. That would drop by end of flight to (a guess) around 400W. This should give about 7 minutes or so in the air. Depends on flying style, model weight, wind, etc.

That power level is roughly equivalent (I believe) to a .30 at fresh and a .25 at end of flight. I would personally use one of the Turnigy Plush ESCs.

YMMV of course.

Mark Pidduck16/04/2018 20:46:04
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29 forum posts
7 photos

Nigel & Pat, many thanks indeed for further suggestions regarding the motor, LiPo battery and ESC. Food for thought. I will have to make a decision before I arrive at a final plan for the front end.

Andy - Wonderful! Don't worry about taking your time - I'll try not to let you beat me to the finished model, but you wouldn't have to try hard to beat me to it, I don't think!

Mark Pidduck17/04/2018 20:58:26
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29 forum posts
7 photos

Thanks to everyone for the ongoing support and advice. It really is appreciated.

I am aware that LiPo batteries get hot, and that allowing airflow not only over the motor but also the ESC and battery is important, and I have been considering how best to do this. Leaving a hole in the bulkhead, as with those in IC models allowing fuel tubes to pass through, would be one way to do it, letting air escape further down the fuselage through inevitable gaps between wing & fuselage, where control rods leave by the tailplane etc, but is this likely to provide sufficient airflow?

Please forgive the basic level of questions here - I am a beginner when it comes to electric motor installations, and I couldn't find any other relevant information elsewhere on the forum. Thanks in advance for any advice!

Nigel R17/04/2018 21:38:52
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1296 forum posts
287 photos
Mark

Two suggestions

First. an outlet hole on fuselage underside rear of wing about 1in square.

If you're doing a cowl then the inlets only need to be small - about a quarter of the area of the outlet hole.

Bulkhead holes, size somewhere in between.

Make sure the esc gets plenty of breeze.

This is the route I took on the rm trainer.


Second. Another way to do it is to do a three quarter cowl - as if you have an ic to fit, and mount the esc where the cylinder head would poke out. This sort of arrangement would also give good airflow over the motor. There's a photo in my misc album of a 20 size biplane done this way.
Nigel R28/04/2018 15:35:39
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1296 forum posts
287 photos
Right. Wood is on order, I'm building one too!
Mark Pidduck29/04/2018 14:33:59
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29 forum posts
7 photos

Great to hear, Nigel!

Sorry I've been maintaining radio silence. Work has overwhelmed me somewhat. On the bright side, I now have most of the wood I'll need to get finished when things ease up.

AndyD - any progress? smiley

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