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Old Aug 03, 2005, 05:34 PM
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Gary Warner's Avatar
Dallas Tx USA
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Hobbico Twinstar 25 ARF: G to E Conversion

Sleepy little group... Here's my latest conversion.

I bought a Hobbico Twinstar ARF today from the LHS. It's a 25-40 size twin motor sold by Tower Hobbies too. It's a fair kit for $119. Specs on box are: 5.5 - 6.5 pounds, 56" wing, 568 Sq. In., 4 channel.

I was considering the AXI 2820/12 motors on 3S2P with 10-6 to 10-8 E-APC props. It should be good for about 10 minutes of traffic pattern 'slow' flying with many touch and goes. Full power climbs will be 950+ FPM.

I'm going to make my own motor nacelles and I might make a new nose cone to improve on the looks. I also plan on increasing the rudder cord a fair bit for better yaw control at slow speeds.

I'll post things I do and find here as a record of this conversion. Here's a pix of the plane and a link to Tower's page for the Twinstar.
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Old Aug 03, 2005, 09:38 PM
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Great conversion, I will be following your thread. I have a friend who almost got this same plane, and was thinking of comverting it to electric too.
Hope everything works out for you,
Best of Luck

Sam
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Old Aug 04, 2005, 12:21 PM
York Electronics
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Dallas Tx USA
Joined Apr 1999
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Thanks Sam.

I laid out the parts last night to get my first good look at things. The motor/nacelle mounts are going to have to go. I will use then as a template for the new nacelles. I plan on extending the forward and rear dimensions to make more of a Cessna 421 type look. The motors will be enclosed and have scale looking air intake holes. The nose is a toss up. I think for now, I'll build it with the stock nose and make changes if they are needed after some flights.

I weighted all the parts that will be used. It's about 3.5 pounds. I'm thinking this will come in at 5.5 - 6 pounds - a bit better than what I had planed for. There's not much room to lighten the model's structure, so I'm just going to build it per plans.


I like that the servo tray is already in place and the pushrod tubes are in place. Looks like the nacelles are going to be the biggest project.

Last night I ran the numbers on Astro 05 DD motors since I already have a good pair. I'd loose about 3 minutes flight time and about 150 feet per minute in the climb. Still considering what to use. Money plays a bit into what I get/use, but I can put what ever I want into it. Any ideas?

This weekend I'm finishing a rebuild of an Artemus sailplane. I expect I can start work on the plane early next week. I guess it was a bit soon to start this thread, but I'm just excited about this plane.

Next posts when I finally get started building.

Gary
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Old Aug 04, 2005, 03:14 PM
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Dont know much about those astro 05 DD. I will see if my friend Herm Perez chimes in here, and might answer that.
I'm planing on putting together a 70 inch KI-45 jap Fighter/bomber that I just got in, and I'm thinking of using those top end MP-jet brushless motors that Hobby-Lobby sell. They can handle 3 1/2 pounds per motor. This with two TP 3s 4200 Li-Po
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Old Aug 04, 2005, 03:23 PM
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Can you supply the part/model number of these motors?

Gary
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Old Aug 04, 2005, 03:27 PM
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Here's the link:
http://www.hobby-lobby.com/brushless-mpjet.htm#AC

The motor part # is MJ20201.
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Old Aug 04, 2005, 03:44 PM
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Gary you might want to check Todd's Models too.

I love my MPJet....

http://www.toddsmodels.com/Brushless%20Motors/mpjet.htm

Mike
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Old Aug 04, 2005, 03:52 PM
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Cool Mike,
Thanks for the link. Now I could save $5.00 on each motor.

Sam
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Old Aug 04, 2005, 04:06 PM
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I like the MPJ 28/20-7. Do you know if they have a radial mount for this one?

Gary
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Old Aug 04, 2005, 04:18 PM
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Quote:
Originally Posted by Gary Warner
I like the MPJ 28/20-7. Do you know if they have a radial mount for this one?

Gary
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Yep...
It is on Todds site, but with no picture. Look at the link above, it is listed below all the motors. I'm pretty sure it uses the same one as the shorter motor. Hobby Lobby only lists one as well.

Mike
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Old Aug 04, 2005, 04:36 PM
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Thanks Mike. I couldn't tell because it was listed for another motor part number.

Gary
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Old Aug 04, 2005, 08:46 PM
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Gary, the two astro 05s you have would be the low cost solution, you already have them.. and they can be fed by one speed control saving you the cost of buying two brushless speed controls. They would be easy to mount if you are building new nacelles.. I would just screw then behind the firewall like you would do in a glider.

Here is the astro website:

http://www.astroflight.com/e/env/000...roducts:af-605

35 amps with an 8*4 prop with 8 nicad cells , about 290 watts. 40 amps with a 3s lipo pack..at 40amps per motor your climb rate would be 1500fpm and your max speed would be 60mph, assuming plane weighs 6.5lbs. You could also use 5s lipo pack with the motors wired in series, that would do 35amps.

Twins are usually more efficient than singles, so the performance will probably be better.

Herm

note: 5s 4200 lipo pack, two AF 05 motors wired in series, one speed control, 35amps total current and about 600 watts, plane should weigh around 5.5lbs if you dont go crazy. Dont fly the motors full out the whole time, they will burn out quickly. Max continuous on these motors is about 25 amps.
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Last edited by hermperez; Aug 04, 2005 at 09:07 PM.
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Old Aug 04, 2005, 08:55 PM
know it all
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BTW, you would have to be nuts to put two glow 40s in this plane.. maybe two sport 40s such as the OS LA40, two 25s is more like it.

A big thread was done on this conversion already:

http://www.rcgroups.com/forums/showt...ight=twinstar+

Herm
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