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Rob's Grumpy Tigercub build


Rob Ashley
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She is very aerobatic a delight to fly very smooth upright or inverted - I'm already thinking she will become one of my favourites.

She flew sans canopy and I will add some vents to the nacelles - the TE vents I have work but I guess more cooling wouldn't hurt.

grumpy tiger_rob ashley-152529.jpg

As you can see I was quite happy.

grumpy tiger_rob ashley-152564.jpg

Picture credits go to my good friend Steve.

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  • 1 month later...

After some more test flying I have settled on a CG of 100mm from the inboard LE which is 5mm aft of the position on the scaled up plan (mine is an enlarged version and is 68" span which, if memory correctly serves, is a 25% scale increase). I think it can come further aft a little but she copes well with the balance in the current position.

For those who are considering building one - I would and you won't regret it. Others have been built and modified to look more like a Tigercat and have been fitted with retracts. For me it was my first electric build following a blown IC cylinder liner so I kept it as per the plan.

For those interested my setup is:

2 x Turnigy D3536/8 1450kv motors.

2 x Hobbyking 60A ESCs - these are a little OTT as the motors run at 31A full chat.

2 x 3S battery 3000 and 3300 mAh Lipo (1 in each nacelle) which give between 8-9mins duration.

1 x Rx battery in the nose to help CG and provide power to servos.

AUW was 2.9kg and with 2 blade 10x5E props the static thrust is 3.54kg. She will keep going vertically. I generally fly at 40% throttle and can loop from level flight and do all sport aeros from that power setting.

The build was straight forward, although I needed to re-shape the nacelles after switching from IC to elec. Probably the only item that I remember from the build was bending the nose of the fus at the front but a SLEC jig helped here. I also built a plug for my own canopy but it was pretty easy really.

Rob

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  • 1 year later...

Interestingly after some 25 flights I can confirm Peter's decree that she will fly well on one engine. She does indeed cope very well with asymmetric thrust after a problem I had during a take-off.

I initially setup both the throttles via a Y lead which worked well for a many flights, but then decided to give me trouble (in fact found to be broken). During take-off the right motor stuttered and then stopped completely a few seconds before rotation. So I continued the take-off and flew a few circuits one one motor. The compensating rudder input was quite linear with increasing power and so very predictable, so it was quite easy to fly a good approach and landing. She needed about 2/3rd throttle to fly in the cruise comfortably.

I did some more experimentation and found that you can take-off on one engine as long as you are careful during the throttle up - too fast and she will ground loop quite violently....even with full rudder deflection and tail wheel on the ground, quite exciting really.

I have since put each throttle into its own channel and, strange old thing, no more problems. But I must say this is a very capable aircraft with a wide CG range, good all round performance (even on one engine) and can be flown like a trainer or flick rolled to death across the sky - I think a great testament to the design.

Merry Christmas all.

Rob

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Chris - Good for you! You wont regret it

Peter - That is very true! Recognizing single engine condition is the key to success and then flying accordingly. Although the mantra 'raising the dead' should be respected the GTC doesn't seem to mind turning in either direction with either motor out - just do it with care.

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