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Old Sep 30, 2008, 10:20 PM
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The blade numbers go up to 11
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Sydney, Australia
Joined Aug 2002
4,478 Posts
Originally Posted by k_sonn
It's not the sound of the Stumax fan that I find unimpressive, its the lack of performance the fan has when compared to a TF4000/Nue 1912 1Y combo running on 10S at 89A and 3200 watts. IMHO it's your awesome energy management piloting skills that make it look good.

I know you're not a big fan of mine, Kirk, but let's get things into perspective. The SM110-52 was designed to fly .91 ICDF sized scale models with scale inlets off grass runways at scale speeds with enough thrust at those speeds for good aerobatics. Take a model with 66cm^2 (ie 90%FSA) inlets and put a 120mm fan in it and see how poorly it performs, yet the SM110-52 will do fine. Take a model with 90cm^2 inlets and a 120mm fan will beat it every time, but there aren't many models in the right size range with such large inlets. It wasn't designed for guys who just want to half-pipe all day long as if they're flying in a virtual skateboard rink. As it was designed for good bottom end performance, it unloads considerably during flight. A customer with a Spark had telemetry which showed 3.2kW static but ~2.6kW in straight and level flight (less in a dive), increasing to ~2.8kW when going vertical. That's a drop of 25% in flight, and the good thing is in gave the extra when required. It was radared at 145mph, which compares favourably with it when it had a DS75 in it. We're still working out the optimum exhaust size, it is very dependant on inlet size, so it's not a "one size fits all" like a rotor/stator fan which is much less critical. IMHO, Gordon's flight shows us that it has the grunt to pull a 16lb model up into a vertical 4 point roll without a big dive to get speed - it's the low down thrust that keeps it going rather than its own momentum - in fact in Gordon's excellent video there is very little of what you call energy management, most of the verticals are done after a simple turnaround. Yes, it does compromise a bit of performance in order to get the good sound, but I haven't had any complaints from customers yet, from nearly 40 units sold. Some people gauge performance by only one factor - straight line speed, usually out of a dive - but there's more to it, especially if you fly off grass, as you have to make it into the air safely before you can do anything else.

That said, I'm looking forward to whatever model you choose do do, as you always do such a good job. I can do a super shiny, pylon racer type finish with my eyes closed, but there's no way I could ever do a scale model to your level, my patience just isn't there.

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Last edited by stumax; Sep 30, 2008 at 10:26 PM.