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Dec 28, 2019, 06:10 AM
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Senior Telemaster - convert to Electric

I have a vintage (built from a kit eons ago), Senior Telemaster that has been flying "well enough" with a SuperTigre 61.
I'd like to convert it to Electric. Any suggestions or "lessons learned" from those that have done this?

- James
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Dec 28, 2019, 07:42 AM
A man with too many toys
If I were doing that conversion I would use a Rimfire .80, 5s 4000 to 5000 LiPo, 15x6 prop, and a Talon 60 ESC. I like that ESC because it has a high capacity built-in BEC.

Select a battery that will give you the correct CG and the flight time you want.

Rimfire motors are my favorite for medium and large airplanes. They are high quality and will worth the price.

You might want to experiment with props once you get it flying. With a 5s LiPo you could use a 16x6 prop. I like APC thin electric props best.

Dec 28, 2019, 07:50 AM
A man with too many toys
Originally Posted by jstibbards
Any suggestions or "lessons learned" from those that have done this?
"lessons learned" - don't buy a cheap motor. Like the old saying; Buy cheap buy twice.

The other lesson is to have plenty of BEC power. Some ESC's don't have a big enough servo power for a large airplane and need a separate BEC. For that I like the CC BEC 2.0.

Dec 28, 2019, 07:53 AM
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scirocco's Avatar
Welcome to RC Groups!

It seems most threads on the Senior Telemaster conversions have been in the Giant Electric Airplanes and Power System forums.

Here are some links you might find useful. Also scroll to the bottom of this thread for a listing of similar threads - but lean pickings unfortunately

Here are some general considerations to think about before you leap into the conversion that might help start narrowing what is a very broad set of options, copied from the Power System Suggestions thread.

Originally Posted by scirocco
Because the sort of performance you need is easy to achieve and can be done so many ways, giving some of the other design considerations some priority will help narrow the field.

First off, if you used to run up to 14" props, that will be big enough to build a good power system around, so I'd suggest there is no point in choosing a prop that requires you to modify the landing gear. But if you had "clearance to spare", taking advantage of that to use a bigger prop makes sense in a slow flying model. If you have the clearance the 18" Yoda assumes/suggests allows a lot of flexibility in motor choices - much bigger starts to narrow the motor and battery choices and props get expensive.

So step one, establish the maximum prop diameter you are happy to use - I usually allow at least 1" clearance with the tail up, but your flying field may influence this. If clearance = heaps, then I think for that model and type of flying, 18" would be a good start.

Second, look at weight distribution. A motor just big enough to do the job will typically be a fair bit lighter than the glow engine it displaces. As Yoda mentioned 3W/g is a conservative guide for ballpark motor sizing, so 900W in suggest at least a 300g motor; while a Supre Tigre G61 weighs 756g with muffler. Battery weight is likely to be a fair bit more than a tank of fuel, but as its weight doesn't reduce in flight, at least we can use the battery weight in achieving cg.

So how did the model balance previously with the glow engine mounted and how might it balance with say 600-800g of battery weight wherever you can fit it and various motor weights? If it would need ballast in the nose with the lightest feasible motor, then it would make more sense to look at heavier candidates for electric motors. For example, the outcomes based on the 300g 420 rpm/V motor Yoda suggested could also be achieved with the 360g G60-400 (about the same cost), or by switching from 4S to 6S batteries (with a moderate increase in power) the 485g G110-295, or even the or even the 649g G160-290. I concede there is a cost difference that exceeds the cost of lead, but using motor weight to balance an otherwise tail heavy model will minimise the need for ballast, and the larger motors will be substantially more efficient in the power range under consideration, with consequent greater flight time for a given battery size. A side note here - don't assume because a motor has a big glow number in its label that it is too "powerful". Power depends on battery, Kv and prop size, not the label on the motor and we can exploit motor weight and Kv as we choose within reason to tailor a power system.

With max/desired prop size as a key input and an idea of whether to work with the lightest feasible motor or to look at heavier options, the design space will shrink a lot.
Dec 28, 2019, 11:19 AM
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Thread OP
Thanks very much!
Dec 28, 2019, 11:26 AM
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Thread OP
This in wonderful food for thought - thank you!
The plane is still set up with the original in-flight gear, engine, tank, etc. so I can check the CG
as compared to the plans, and check the overall weight, and prop clearance. Using a larger brushless motor to efficiently provide balance, vis-a-vis lead weight in the nose... brilliant!
Jan 04, 2020, 09:06 PM
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PC Pilot's Avatar
I like the relaxing way the Telemaster flies. I have built several and the current one is a twin. As club instructor, my Telemasters have given a bunch of people the confidence to try the hobby.

Items used are Eflite 32 motors, I think the ESCs are Eflite 60 amp and the plane flies with a 4 amp, 6 cell lipo in the nose.

No provision was made for battery cooling so I limit flights to 6 min of scale type flying. The battery gets warm but not hot.
Last edited by PC Pilot; Jan 23, 2020 at 11:49 AM.
Jan 17, 2020, 07:55 PM
Registered User

Power for Telemaster

Powered my "old school" Telemaster as follows:
1. NTM 4248 - 650KV motor (HobbyKing)
2. 4 cell - 4000mah battery
3. 65 amp ESC
4. APC 15x8E prop

Flies GREAT!
Jan 18, 2020, 08:38 AM
I just want to go fly!
walter3rd's Avatar
Not a senior but the smaller 40 size. Flys great on 42 size motor with 4s batt
Jan 21, 2020, 11:18 AM
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PC Pilot's Avatar
Originally Posted by walter3rd
Not a senior but the smaller 40 size. Flys great on 42 size motor with 4s batt
Congrats on the successful swap.
Feb 14, 2020, 11:05 PM
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speed2004's Avatar
I fly my 8ft Senior T on a Power 90 325KV and 5S/5000 using a Castle 75 amp ESC. I used 90 degree aluminum channel to fit motor mounts and a 1/4 Ply firewall in front for Xmount to keep it flat. It balances well with the big motor up front.
Feb 15, 2020, 07:10 PM
Gravity is a harsh mistress.
Tim Wolff's Avatar
Here's the details on one I converted.

The battery pack was as far back as it could go, literally under the wing and still felt a little nose heavy. So keep the CG in mind when deciding how heavy a motor to put up front.

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