DB Tiger Moth 58" span

[Tony Harrison 2]

Some while ago I bookmarked the very interesting thread about Terry Walters's electric-power DB Moth, from several years ago. I'm building one myself, and I wonder if his motor is still the best bet - or if there are alternatives. His was/is an Emax 4020: on the RC Life site they list an Emax GT4020/07 620KV 60A Brushless Outrunner Motor, which is I assume the same one.

rgds Tony

[Geoff S]

I fly my DB 58" Tiger Moth (as in my header picture) on a EMAX GT3526/04 870 rpm/volt with a 12x6 prop on a 4S 4000 mAH LiPo. It draws around 20 amps on straight and level cruise and I usually fly it for around 8 minutes before landing with about 20% left in the battery. Performance is better than scale. I flew it a lot last year.

 

I'm currently building a DB 58" Cirrus Moth which will have a EMAX 3526/05 710 rpm/volt motor with the same battery.

My quarter scale Percival Mew Gull has a EMAX 4030/06 420 rpm/volt motor on a 4000 mAH 6S LiPo currently on a 14x7 prop but I have a 16x8 to try when the weather improves. I used the 14x7 for the test (and only so far) flight and it was fine for this 4.5 kg model.

 

I would have thought a GT4020 would be a bit more than required for the Moth but you can always prop down. The motor weight won't be a problem. I had to put lead in mine to get it to balance.

Geoff

 

Edited By Geoff Sleath on 16/02/2018 23:35:47

[Former Member]

[This posting has been removed]

[Tony Harrison 2]

Geoff, many thanks - I've noted your motor choices, and when my Moth is a bit further on I'll buy one or the other. I don't yet know enough about this business to appreciate the difference between those two versions of the Emax 3526, but for now your advice is appreciated. I'll finish my Moth as late/post WW2 RAF trainer N9498 as flown on its last ever UK flight by my uncle in August 1947, Aston Down to Sealand - where it was crated up and shipped to Burma...

rgds Tony

[Geoff S]

Thanks, Tom. The Mew Gull was test flown in December and I'm waiting until it gets warmer to fly it more.

Tony, on reflection I think you may find a kv of 620 rpm/volt a bit slow. It will need either a big diameter prop or one with too much pitch for what is essentially a slow flying aircraft. Initially I flew my Tiggie on a 13x4 which made take off runs very short (lots of acceleration) but the 12x6 was better in the air and the take off was still quite short. Not very scientific but just how it seemed. I had current telemetry for the early flights to get a feel for the energy consumption; it's now fitted to Mew Gull for the same reason.

Anyway, feel free to ask about battery/motor installation. For a start, get the battery as far forward as possible - ideally under the motor (mine isn't) and plan the power train fitting as early as possible whilst you still have easy access to parts if they need to be modified.

Geoff

[Tony Harrison 2]

Posted by Geoff Sleath on 17/02/2018 11:18:24:

Thanks, Tom. The Mew Gull was test flown in December and I'm waiting until it gets warmer to fly it more.

Tony, on reflection I think you may find a kv of 620 rpm/volt a bit slow. It will need either a big diameter prop or one with too much pitch for what is essentially a slow flying aircraft. Initially I flew my Tiggie on a 13x4 which made take off runs very short (lots of acceleration) but the 12x6 was better in the air and the take off was still quite short. Not very scientific but just how it seemed. I had current telemetry for the early flights to get a feel for the energy consumption; it's now fitted to Mew Gull for the same reason.

Anyway, feel free to ask about battery/motor installation. For a start, get the battery as far forward as possible - ideally under the motor (mine isn't) and plan the power train fitting as early as possible whilst you still have easy access to parts if they need to be modified.

Geoff

OK Geoff - I've recorded all your comments & advice for reference. Might get back to you sometime in the next year or so, as my build progresses.

rgds Tony