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Old Jan 15, 2012, 01:58 PM
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I was kidding about the hours. However it would easily take 1 min or more to climb to where I wanted. Which puts a huge strain on that motor. I can now easily climb almost out of sight in less than 10 seconds now.
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Old Jan 15, 2012, 03:17 PM
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Chilliwack, BC Canada
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Quote:
Originally Posted by Tomy. View Post
...............

Now I put blue locktite on those screws (same that I use on helis) so I suppose this will not be a problem any more.

...............
Locktite attacks plastics. I made the same mistake when I replaced my motor. I took it apart again, cleaned the Locktite from the plastic and used glue instead of Locktite when I put it back together. Think I used canopy glue, can't really recall. It was something that I figured would stick but not become brittle.

Gord
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Old Jan 15, 2012, 04:19 PM
Good Better Best quest.
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Australia, VIC, Cranbourne East
Joined Apr 2004
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Quote:
Originally Posted by FlyWW1 View Post
I was kidding about the hours. However it would easily take 1 min or more to climb to where I wanted. Which puts a huge strain on that motor. I can now easily climb almost out of sight in less than 10 seconds now.
Im quite happy to wait a minute to get to 400' did you post your trim details? cg ect, what do you think of elevator responce when gliding?
they thermal well but watch out for the boomers they can suck you up faster than you can dive ,thankfully only caught mild one yesterday but a good 20min flight.
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Old Jan 15, 2012, 04:31 PM
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Originally Posted by Tomy. View Post
Starting with a confession --> I'm a heli guy, so I am a bit on unknown territories with airplane power system sizing.

I read through (most of) this extremely long thread, but I still need to ask. Which one of these would work better?
This one 850 KV 380W bell style and I will add a bigger prop (something around 12 or 13 size), or this one 250W 1550kv bell style and going down with the prop size (to an 8 probably). I'd also consider this one 180W 1000KV but it's out of stock at HK.

Which one would be a better solution and why? Anyone tried or is using any of these motors?
For ESC I am planning to go with the 30A HobbyKing BlueSeries (unless someone starts to scream about the quality now, the reviews are good).

Ah and another question. Right now I've stuck a full range AR6210 on it with satellite, this bird can fly high and far but I will need that Rx back. Will an Orange 6ch with Orange satellite from HK also suffise for her?

This is actually my son's glider. He has a few fixed wings, (he also flies helis ) so I got him the arttech MiniMoa from nitroplanes for christmas. I have already put a smaller 10x6 ATC props on, and the handful of flights so far showed no motor or ESC overheating problems even in nasty winds today (solid 10-15 with 15-20 gusts!) close to 100% throttle throught half the flights. But better safe then sorry...

This is him on the 31st before the maiden flight of the plane.

Thanks!
Your following posts seem to show that you are getting along well with the original motor, but if that 180w motor ever does show up in stock again, it is a good choice. See this post > http://www.rcgroups.com/forums/showp...&postcount=602

The 350w motor you mentioned will not fit. It is 41 mm in diameter and that motor recess in the nose is only about 33 mm wide.

The 250w motor will likely pull way too much current with the 11 inch prop, if that is what you have, and will probably still overheat with the 9 inch prop on a 3S battery unless you limit your throttle as VTDIY has suggested. It certainly would require an ESC replacement. Might be interesting on a 2S battery though.

As Wizard has said, drilling new holes in the mounting base to match the holes in the plastic can mean just elongating some holes. Dremel time. And you may need to either put another hole through the nose to access the set screws or drill and tap a new setscrew hole in the base to match the hole in the nose of the Minimoa. Not a big deal, but be warned.

Or, if it isn't broke, don't fix it!

Gord
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Old Jan 15, 2012, 05:22 PM
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olmod,

400' is not quite high enough for me most of the time I run all my surfaces on 120% deflection and 30% expo. My elevator response is nice at any speed. My CG is set on the main wing spar I think it's 55mm from leading edge. I mixed in 45% down elevator on full throttle and that keeps my pitching down when climbing. I also have 45% aileron mixed with rudder. I'm getting some sweet carving turns with that mix. It also gives it a nice tight roll rate in dives. Tomorrow I'm going to mix in some flaperons to try and make it float like my Radian when it's close to the ground. I don't think it's going to work but it can't hurt to try.
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Old Jan 15, 2012, 07:47 PM
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vtdiy's Avatar
Southern Vermont
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I think the flaperons worked rather well.

Olmod, good to know about the elevator authority in a boomer.
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Old Jan 15, 2012, 10:51 PM
I am a Helicolic! Citizen#207
Tomy.'s Avatar
Redmond, WA
Joined Aug 2010
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Quote:
Originally Posted by Gordks View Post
Locktite attacks plastics. I made the same mistake when I replaced my motor. I took it apart again, cleaned the Locktite from the plastic and used glue instead of Locktite when I put it back together. Think I used canopy glue, can't really recall. It was something that I figured would stick but not become brittle.

Gord
Gord, yo uare absolutely right, it might be a problem but only if you let loctite come in touch with the plastic. You just need to know how to apply threadlock in these cases. I have been using threadlock on helis for years on metal-metal contacts even through plastic (similar to the minimoa's mount) without problems. You do not put the locktite on the bolt before pushing it through the plastic part. You drive the bolt partly into the threaded piece, then apply the locktite form the opposite side (further from the plastic) of the threaded piece and let it sync in before tightening the bolt (it will not be able to get in touch with the plastic because the screw already seals the hole of the threaded piece from the plastic's side).

Quote:
Originally Posted by Gordks View Post
Your following posts seem to show that you are getting along well with the original motor, but if that 180w motor ever does show up in stock again, it is a good choice. See this post > http://www.rcgroups.com/forums/showp...&postcount=602

The 350w motor you mentioned will not fit. It is 41 mm in diameter and that motor recess in the nose is only about 33 mm wide.

The 250w motor will likely pull way too much current with the 11 inch prop, if that is what you have, and will probably still overheat with the 9 inch prop on a 3S battery unless you limit your throttle as VTDIY has suggested. It certainly would require an ESC replacement. Might be interesting on a 2S battery though.

As Wizard has said, drilling new holes in the mounting base to match the holes in the plastic can mean just elongating some holes. Dremel time. And you may need to either put another hole through the nose to access the set screws or drill and tap a new setscrew hole in the base to match the hole in the nose of the Minimoa. Not a big deal, but be warned.

Or, if it isn't broke, don't fix it!

Gord
I'm not "fixing it" because it's broke. I want to have more pop. The stock system significantly under powers this plane (a.k.a. it sucks).
For the 250W motor: yeah I know I'm too thinking i made a purchase for no reason . Anyways, that motor might just stay put until the next project!
It seems you hit it right on the head. The 250W 1650KV motor would need to run at 28-30A even with an 8x6 or 9x6 to be just decent, that would be somewhere around 60% efficiency, lots of waste electrons and heat.

After playing with the numbers in motorcalc, it's clear that putting more than the 1000KV as an upgrade makes no sence with these size motors. Either the effciency goes down to under 70% and max amp goes way above 20A, or the static thrust is too low, or if all else looks good, your battery life would suck. Actually the 850KV 380W looks pretty good, with a 10x6 or 11x6 could easily outperform the stock. It'd pull 13-18A and have about 85% efficiency compared to the ~70% efficiency of the stock 1200KV, not to mention 30-50% longer battery time. Even if for the wider 41mm can I need to make a new mount.

Here're the numbers. I know there's more to it than prop size and KV, but those 2 gave a good baseline comparision to find where to dig in more. Compare the 850KV with 11x6 or 12x6 to the 1000KV with 10x6 or the 1200KV with 10x6. Look at amps, efficiency and static thrust -- and max flight time


If anyone has a force meter, I'd be interested in what the 1200KV pulls with 100% thrust on 3 cells with the 10x6 prop, the calculations show around 1000g but I'm a bit doubtful just by feeling it by hand.
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Old Jan 16, 2012, 10:49 AM
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vtdiy's Avatar
Southern Vermont
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There is no question that for this plane there could have been a more perfect motor for 3 cell Lipos.

I suppose the same could be said for any RTF. Re-powering would likely improve some aspect or other. Nothing manufactured for the masses is perfect. Everything is a compromise. Nobody is satisfied with the same things.

Mine will reasonably quickly get up to altitude for gliding on 2 Lipo cells with the 11 inch prop. That's what I bought mine for, whether that kind of performance "sucks" in anyone else's opinion, or not.

I fly with guys using towline gliders in competition. I can easily match their tow altitude in a minute or two. They do it in a few seconds, but have tremendous reinforcement of wing structure to handle the launch stress, extremes of construction, and if truly competitive, using gliders costing thousands of dollars. Mine cost about a hundred.

I have no problem with motor changes and modifications, after all I generally build my planes rather than buy them. Maybe I will some day as well. What's the big deal about modifying an ARF with a new motor if you design and build planes? But I'm happy enough with the stock Minimoa at present to appreciate the modest climb to height power performance I figured it would have in the first place.

When flying, I do bring along homemade warbirds with better than 1 to 1 thrust ratios when I feel like tearing up the sky. They make the Minimoa look slow and un-maneuverable by comparison.

I don't think about doubling my P-38's or Corsair's wingspan to ride a thermal, though glide performance could certainly be improved with longer wings. I wouldn't say they suck strictly for that reason. I drive my planes to the field with a 4 cylinder pickup truck, which I haven't re-powered, either. though I'm sure I could get better performance if I did. No argument with someone else who drives a BMW to the field. All are welcome.
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Old Jan 16, 2012, 12:58 PM
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Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
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Vermont. I am with you. I love my Minimoa with the 28-30 950 kv motor and the original folding prop on a metal spinner. I replaced the plastic motor mount with a metal washer epoxied and fiberglassed into place. I also fly high performance warbird and aerobatic planes. Never have I wished for more power on the Minimoa, a good climb rate is all I want. I am interested in this bird as a soaring airplane and have 80 hours in full-size gliders as background. I have done some limited ridge soaring so far, but have yet to have any thermal-producing conditions. You can be assured I will be out this Spring and Summer with my head (and the Minimoa) "in the clouds". In the meanwhile I can still get my jollies by using the current motor/prop configuration (about 200 watts) to climb then shut the motor down, drop the nose and go whistling by. Even if there is no wind, my favorite place to fly is a little ridge close to my house that has a parking lot on top of it and a beautiful view of the mountains. I enjoy watching the Minimoa float along with the mountains behind very much. It is relaxing and puts me in touch with the natural world, as if I am a bird, which the Minimoa is clearly designed to resemble. Also, I think that executing a perfectly coordinated turn on a glider requires some serious flying skills, as in the case in a full-size glider. Having a powerful motor on the front of an airframe means that you get get away with all kinds of crappy flying and still look good to the uninformed. Flying my Yak 54 through a complex series of conventional and 3D maneuvers is great fun, but it is not relaxing!

My two cents from Colorado,

Jackson
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Old Jan 16, 2012, 01:25 PM
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Yep gliding well does require more skill imho too, that is something I have been trying to get my mates to apreciate who only seem to want to fly warbirds or jets or heli or 3d planes and think that I am boring because I fly the glider mostly, truth is I get bored flying with motorised planes no mater how fast they go, it's just too easy and not rewarding in the same way as hunting and finding a thermal with a glider is but although one has a glider and flies it about once a month in the summer I think he has only ever caught 1 thermal and gone up and his glider stays up for 35 mins upwards without thermal so most of the time he comes down early and just does get the challenge--just a bad neck lol.
I fly my warbirds from time to time and 3d ocationally but within 5 mins wish I had brought the glider lol.
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Old Jan 16, 2012, 02:19 PM
I am a Helicolic! Citizen#207
Tomy.'s Avatar
Redmond, WA
Joined Aug 2010
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Quote:
Originally Posted by Jackson Stone View Post
Having a powerful motor on the front of an airframe means that you get get away with all kinds of crappy flying and still look good to the uninformed.
Wrong. It helps my 12 year old son pull the plane (that he got for Christmas and loves alot) up if badly needed. He will have those "glider skills" that you are talking about by the time he's 13. (Unless he spends most of his time with helis, in that case he'll probably have amazing 3D heli skills in a few years.)
I too found flying this glider relaxing. But would not trade 30 minutes soaring for 5 minutes hard helicopter 3D. This is my son's plane and when you are comparing your skills (especially if you had a bunch of hours in a real plane) with his skills, well that's pathetic.

Seriously guys, I'm loving how you are in agreement but really, that's it? I have thought that those airplane skills and experience of yours will help me put more power into this plane, but instead I just got a bunch of uninformed skill assessment .

So c'mon, be constructive and let me hear more about those modded power systems!!!
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Old Jan 16, 2012, 02:23 PM
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Guys I think you misunderstood what I was saying. I use this plane for gliding and soaring. I do not use this for sport flying although I could. I just like to get high fast and float around for 1/2hr or so. I had a Power10 laying around so I decided to give a whirl. I wasn't trying to cover up my crappy flying skills or say mine is bigger than yours. I was just putting the information out there. To each their own I guess.
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Old Jan 16, 2012, 02:42 PM
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Tomy,
Do you need something that will fit the stock motor mount? If not are you comfortable making a mount out of wood or metal?
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Old Jan 16, 2012, 03:56 PM
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Southern Vermont
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Uh, Tomy there is plenty of information in the 100 pages of this thread on changing motors, and will certainly continue to be. This thread isn't anti-mod.

This particular glider is fairly demanding in several ways that are not novice friendly, including doing motor mods. The area in which a motor can fit is restricted,and the mounting system can't take a lot of heat. There aren't a lot of motors that can be easily swapped into the mount.

No one is lecturing you on your or your son's skills. It does not sound like this was a good choice as a trainer, or even a glider trainer. One option would be selling it and getting something designed more for the kind of flying you and you son would like to do. All flying is good, but there are definitely many different styles and requirements for a huge range of airframes and power types.

Another option is to experiment with a new power train, as you are considering. Just be aware that experimentation means the possibility of further problems or even failure. On the other hand it can be enjoyable and rewarding, interesting, and educational. All depends on attitude.

A problem can represent either frustration, or fun.
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Old Jan 16, 2012, 04:14 PM
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Also Tomy, to answer what you were suggesting technically, yes a kv well under 1000 would be best for a 3 cell lipo setup and a prop of 11" or even 12".

Is your present unsatisfactory rig using an 11x7 prop?

Also, it has been pointed out that the 850 kV motor you reference won't fit. I happen to have a DT-750 in a box which I believe is the same motor with a different winding. I also have one in a spitfire. It's a fine motor, but you can't put it in the Minimoa unless seriously chopped its cowl and appearance. Also affecting frontal area and gliding performance. The Minimoa's big attraction is that it is supposed to be a scale looking plane, despite the powering.

There are other 750-850 kV motors available which are smaller.
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