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May 17, 2020, 08:43 AM
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Twin Motor Conversions for performance and easy launching – wings, Goblin, Funjet

I’ve always liked twin motor planes, as they offer many advantages for FPV – unobstructed view, usually plenty of space inside, and good load carrying capacity. My first was the old classic Twinstar, converted from brushed to brushless, but being such an old design, has a more cramped fuselage than most, but with such a large wing area, makes a good long range twin.

I have quite a few flying wings, mostly CTH, but wanted more performance on a budget. That typically means heavier motors and ESCs, but the Rebel 14 40” wing I was working on couldn’t take the weight. I had bought some T-motor F80 Pros to try, giving around 2000g thrust on 6S, but couldn’t achieve more than around 100mph. A friend had just bought a 3D printer, so I asked him to make up a couple of nacelles, thinking that with 2x 2000g thrust, I should be good for 125mph+.

The conversion used 2 x F80 Pro 1900kv motors at 38g, a pair of T-motor F45A-32bit 3-6S ESCs at 10g each, so the powertrain was less than 100g. Two GNB 550 mAh batteries would fit either side of the wing with a total weight of 750g. That worked – 135mph level flight with 6x4 APCs and a really easy launch.

With twice the power of a single motor, this conversion was a success, so what about a couple of other tricky to launch planes..

With the wings carefully measured, both planes were converted using printed nacelles and the same T-motor gear used in the wing. The Goblin was always a pig to launch, but on the first flight flew out of my hand with hardly a throw needed.

Flying characteristics
All the nacelles were fitted with zero angle to the wings, but despite this, the Rebel 14 wing was prone to lifting its nose over 120mph or so, and that was corrected using a throttle to elevator mix coming in at 80% throttle and rising to 100% throttle.

These twin conversions flew very well, turbine smooth and extremely quiet, the Goblin cruising at 40mph drawing 4-4.5A, so no loss of efficiency.

Both the Goblin and Funjet have ET Vectors onboard.

Other twins
My first twin – a very old Twinstar with a Vector, DL3, 7500mAh 4S Li-ion and a pair of T-motor MN212-18s give it a flight time of around 60 mins.

Most recent builds, Finwing Albabirds – very good airframes, the white one my performance fit of F80 Pro 1900kv motors and hit 140mph on the level with 6S.

Thanks to Ianda217 for help with the nacelle design and printing.
Last edited by Flynn203; May 17, 2020 at 10:28 AM.
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May 19, 2020, 05:36 PM
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I really like what you did with the Fun Jet, looks like something I'd enjoy flying line of sight.
May 20, 2020, 01:50 AM
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Thanks, a good alternative to a large motor hanging off the rear.
Jun 21, 2020, 11:07 AM
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Goblin twin motor conversion - easy launch

Strix Goblin twin motor conversion - easy launch and improved handling (2 min 39 sec)

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