The Mpx TwinStar II has arrived! - Page 65 - RC Groups
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Dec 02, 2005, 05:12 PM
Does it come in Flouro??
Numb Thumbs's Avatar

I am using two small outrunners on mine, mounted behind the firewall. All I had to do was shave off some plastic where it rubbed on the rotating motor.

Mine are: 2 x Himark Outrunner C2808-1360 (1360kv) with 2 x CC25 ESC
2 x Graupner Cam Prop 7x6
Total Thrust 1000gm
RPM 8400
Total Amps - 2 motors, static 19.5
Pitch Speed km/h 75.6
Pitch Speed m/h 47.25
All Up Flying Weight 1080gms

I think Multiplex's weight is based on some seriously heavy NiCad.NiMh batteries! The battery compartment is so huge you can balance just about anything!

Check out the videos on my web site:

I just used spray can water based paint on mine and it doesn't look like flexing off. It has stayed on well all my Elapor planes.


Numb Thumbs
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Dec 02, 2005, 05:59 PM
Registered User
Bill Glover's Avatar
Originally Posted by flieslikeabeagl
Do you have a feel for why the TS1 with the cheapy outrunners didn't perform as you expected?
Not really, I assume they're just not very efficient (magnets etc.). It was on 8x5 (?) props, the motors were really noisy. He'd cut the front off each nacelle and fitted a ply bulkhead. We have half a dozen or more UK vendors selling an identical cheap "bell" outrunner plus ESC combo, I believe the source is this company in China:

But ... they are brushless after all, and the price is very good (less than my geared S400s with brushed controller!). So worth a try IMO.
Dec 02, 2005, 07:37 PM
Does it come in Flouro??
Numb Thumbs's Avatar

I chose 7x6 props so I clear the grass!


Numb Thumbs
Dec 02, 2005, 11:59 PM
Got shenpa?
flieslikeabeagle's Avatar
Rutat - that aluminum paint is very impressive. I've used Plasticote "Bumper Chrome" paint on stuff in the past, it comes out looking like freshly cast aluminum - silver, but with some surface roughness. I've never seen paint come close to looking like the finish on that model.

That said, I would think chrome would be a hard "color" to see on a model, as it will pick up and reflect whatever color is in the environment around it - I think it will do a good job of trying to disappear, like a mirror does.

Numb Thumbs, thanks for the info. The outrunners I plan to use are Esskay 400 XT motors (variously sold as Aurora, MM, and who knows what else). Here's a link:

If all goes according to plan, my Twinstar will weigh about the same as yours, and the motors I plan to use will pull about the same current as yours, and have about the same pitch speed. So I expect performance should be close (except for slight differences in motor efficiency, propeller efficiency, etc).

I bought a pair of the GWS 8x6 props to use, but if they don't clear the ground, I will use APC 7x6 Slow Flyer props, which have also been measured at around the 10 A mark on these motors (on a 3S lipo pack ).

I would love to find a pair of counter-rotating props for this model that load the motor to 10 A on a 3S lipo. Even better would be a pair of counter-rotating, three-blade props, just because they look so much nicer. Unfortunately the only ones I know of are the Master Airscrew ones, and the smallest pusher/puller 3-blade prop pair they have is a 9x7. Those will be too much for this motor on 3S voltage.

Bill, I believe the "Esskay" motor is not from Himodel, but rather made by a company called Skatty Products, also from China. I had a link to the manufacturers website at one time, but can't seem to find it. The 400XT was tested by BEC, Dr Kiwi, and a few other folks: the general consensus was that an Axi was definitely better, especially at higher power levels on a 3S pack, but the 400 XT wasn't half bad. Factor in the price, and it starts looking very good indeed.

Hobby Lobby sold these same motors for $19 each on Thanksgiving sale...I missed that as I was visiting a friend in Tucson, otherwise I might have bought a couple more.

The 400 XT also has a big brother, the 450 XT. I believe that is an honest 15 A motor, so about 150 W on a 3S lipo pack. Unfortunately those sell for about $50 each, some 67% more than the $30 400 XT's.

I visited Tony at Tony and Adie's Hobby Lobby today (in Burbank, CA). For those who don't know the man, he is somewhat of a living legend in the electric flight hobby around this part of the world - he's been flying electric planes for a long, long time, and has forgotten more than most of us know. He tells me he uses regular spray can enamels on Elapor all the time, making sure to dust on thin coats from a little distance, so I plan to try that suggestion out.

I also stopped by Robins Hobby in Burbank to pick up some thick foam-safe CA and kicker. That part of the Twinstar build is a little scary: I've never used CA and kicker before, least of all on two very large, very expensive pieces of foam that will become instant junk if I don't get it right the first time...

I still need a couple more HS-81's, other than that I think I have just about everything I need to get started building the Twinstar. Maybe I'll find some time to work on it tomorrow. (rubs hands in anticipation)

Dec 03, 2005, 12:47 AM
Does it come in Flouro??
Numb Thumbs's Avatar

I believe Graupner makes a few of its CAM props in counter rotating pairs. I think there is one size in 7". The local agent was supposed to get back to me on that but didn't! Mine are not counter rotating, but is not a problem at all. It would just look nice, especially 3 or 4 bladed...

Definitely paint Elapor by spraying light coats from around 20cm away. The coats of Flouro I use dry in a few minutes so it is easy to apply lots of coats very quickly.

Put a strip of tape along the belly as this is the bit which takes a beating on landing.

Are you planning on using two ESC's like I do? Plan your wiring BEFORE you build, not like I did and change it after construction...


Numb Thumbs
Dec 03, 2005, 04:10 AM
Registered User
Bill Glover's Avatar
FWIW on my TS1 the 11" props are clear of the ground, wings level, without the trike u/c.

I really wouldn't bother about counter-rotating props. Even with brushless power the TS is a relatively big plane and torque simply won't be an issue.

2 blade props are the most efficient, but if you simply must have 3 or 4 then I would go with Vario Props. They even do reverse rotation blades in some sizes, and of course the pitch is fully adjustable so there's no problem matching the amp draw. But I tested my TS1 with 2 and 3 blade Varios when it was still direct drive, and although the 3 bladers looked cool the 2 bladers flew it better. Both were set up to draw the same current, with 6" blades on the 2 blade hub and 5.6" blades on the 3 blade hub the pitch ended up being almost identical too - about 3.5".
Dec 03, 2005, 05:17 AM
Got shenpa?
flieslikeabeagle's Avatar
Numb Thumbs, I have a pair of 10 A Cool Running brushless ESC's, also a pair of Chinese made off-brand brushless controls (they might be EP Brushless branded), so my first thought is to use one ESC per motor.

If it is safe to do so the wiring might be simpler with a single big ESC mounted in the fuselage - I notice with interest that the power sockets on the little PCB that Multiplex provides actually have three pins, though only two are wired up in the stock configuration. The PCB tracks short the outer two pins together, but with a little careful work with an Exacto knife I might be able to separate which case I can have three motor wires going from the board to the actual motors, with the two motors electrically in parallel.

Is it better to run long power leads to the ESC and short leads to the motor, or the other way around?

Bill, good to know the big props will clear with no problem.

I know very little about propeller theory, but I have heard from two authoritative sources (including one guy who IIRC wrote his M.S. thesis on propeller systems) that multi blade propellers are actually more efficient at the same diameter and power level than props with fewer blades. The reason has to do with the tip vortices from the blades affecting each other in a way that reduces total tip losses. It seems this gain in efficiency can be masked when people use a smaller diameter multiblade prop to replace a larger two-blade prop: in that situation, the increased power loading (watts/disc area of prop) can make the small prop less efficient.

I also remember reading about one case where a smaller multiblade (4 blade) prop was more efficient than a larger 2-blade prop it replaced (I think this was on a model of a P-51 Mustang). In this case, the increased pitch/diameter ratio of the small 4-blade prop, along with the benefits of multiple blades, caused an efficiency gain that outweighed the loss in efficiency from the smaller disc area.

As I said, I don't know enough about it to speak with any authority of my own, but it does sound as if the conventional wisdom may be only half right.

Thanks for the prop suggestions. I may look into those options at a later date when my wallet has recovered a bit. As of now, the plan is to go with two GWS 8x6 props. Once I get it flying, I will also try out the GWS 9x5 HD props, to find out whether I like the slower but thrustier setup or the faster but less thrusty setup better.

Dec 03, 2005, 05:51 PM
Registered User
I ordered a TWIN STAR ll with 4 HITEC 81MGS servos and a JETI JES 030 esc. The JETI is compatable with li-po batteries between 2 and 4 cells and is rated for 30-35 amps. I was going to get an APOGEE 2480 mah. 10.5c 3s1p 11.1V li-po to run the two stock motors and thought I would run it by you guys to see what you think. The battery is rated at 10.5c/26amps continuous discharge and 5-10 sec. burst of 14c/35a. I could also change the motors to 7.2 amps if needed. Any help or comments on this set-up would really be a big help. THE WALRUS
Dec 03, 2005, 06:16 PM
Sooty100's Avatar

It is generally better to keep the battery leads short, lengthening them can possibly lead to ESC damage due to voltage spikes. Having said that I know of a few guys who have done it without problems, mounting the ESCs in the wings near to the motors. Numb Thumbs is one I believe.
Dec 03, 2005, 07:06 PM
Does it come in Flouro??
Numb Thumbs's Avatar

I use two ESC's, one in each engine nacelle. Works fine for me! The ESC's get nicely cooled too!

The plug in the fuz is setup like that so you can plug it in either way around and it still works properly. Just make sure you get all three pins connected...

My wiring diagram is below.


Numb Thumbs
Dec 03, 2005, 11:19 PM
Got shenpa?
flieslikeabeagle's Avatar
Originally Posted by Numb Thumbs
The plug in the fuz is setup like that so you can plug it in either way around and it still works properly.
Those crafty Multiplex engineers! That is a pretty clever design. The reason for it never occurred to me, I was wondering why Multiplex seemed to think there would be twice as much curent in the positive lead as the negative!

Numb Thumbs, your Twinstar is certainly easy to see. . I would not dare to have that similar a paint scheme on the top and bottom of a makes it a bit harder to tell when it's upside down, and consequently when I should push rather than pull on the elevator stick!

Thanks for the circuit diagram, Numb Thumbs. It is close to what I had in mind. Though I wonder whether I should either modify the Multiplex connector board to separate the left and right three-pin sockets, and cut the end pins free of each other. If I do that, I can wire the two motors independently, and still have the ESC's in the fuse.

I find myself a little stuck on the ESC decision. Jurgen pointed out that twin ESC's can cause problems if one hits the LVC cutoff before the other. That gets me thinking about using a single large ESC (Phoenix 35 or similar); others point out that running two brushless motors on one ESC is an uncertain proposition, working well for some motors and ESC's and very badly on others. And then there's the question of using long power leads and putting the ESC in the nacelles where they will be well cooled, or short leads and having the ESC's in the cabin with little airflow...

And finally, I saw the pictures of Bill Glover's landing gear setup, and a couple of LED setups, and now I'm thinking about incorporating those too...

I did get two more HS-81 servos and a couple of 12" servo extensions, today, so there is no good reason for me not to get started. I have a bad habit of falling into the perfectionism trap and not actually getting anything built while I research and think endlessly about the optimal way to do it. Time to kick myself in the behind and go get started, one way or the other.

Thanks for all the helpful hints, guys!

Last edited by flieslikeabeagl; Dec 03, 2005 at 11:58 PM.
Dec 04, 2005, 12:06 AM
Does it come in Flouro??
Numb Thumbs's Avatar

Make sure you put wires in the wings so you can go either route! I didn't and ended up having to add them later - messy!

Good luck with the decision. Mine works fine on the twin ESC system so I don't feel you are likely to have problems.


Numb Thumbs
Dec 04, 2005, 04:15 AM
Registered User
Bill Glover's Avatar
Originally Posted by flieslikeabeagl
I have a bad habit of falling into the perfectionism trap and not actually getting anything built while I research and think endlessly about the optimal way to do it.
You and me both! After I got my TS1 kit I spent about 4 weeks designing the landing gear before starting any building!

FWIW I would go with twin ESCs. By the time you get to low voltage cutoff even if one ESC shuts down fractionally before the other the power level is likely to be low enough not to be a serious problem, IMO. Big plane, small motors. And as pointed out, reto-fitting a second ESC isn't easy.

As far as I know there's only one single ESC setup that's guaranteed to work - that's the (very expensive) Kontronik twin drive set. With cheap motors there will probably be enough variation between them that a single ESC won't work.

Good luck with the build!
Dec 05, 2005, 10:27 AM
Giampiero - Italy's Avatar

TS2 Propulsion Setup

In the past I used the twin ESC (15A each) setup on 2 speed 400 7,2 V and all was fine. After a tragical CRASH (with ESCs on fire), from several months I use one big ESC (JETI JES 45A) in the fuselage on the same motors, and all is even better (it never goes hot).

For your information, yesterday I tested a totally new (for me) setup.

First Test:
Battery: Kokam 3S1P LiPo 2100 mAh
MOTORS: 2 x Graupner SPEED 480 BB 7,2 V
PROPS: 2 x Graupner CAM FOLDING PROP 6 x 3
Flight time: about 15 mins

Second Test:
Same setup but with a 2S1P Lipo 2100 mAh
Flight time: 10 mins

The test was a great success, with a lot of trust and no problem
with both batteries (11,1V and 7,4V). No special heat to report
on ESC and Batteries, and on motors too.

It was a very windy day ... VIDEO
Dec 05, 2005, 12:42 PM
Sooty100's Avatar,

Are you saying you had plenty of thrust with the 2s1p and 7.2v motors as well?
It looks like your video is just with the 3s1p
I need to change to lighter batteries myself for AP work ( I don't use lipos yet) and am still trying to decide the best way for me to go for a lighter setup.

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