I don't know anything about the performance, but I have been thinking of writing Scorpio to ask what on earth a SAAB JAS 38 Gripen is, as the Gripen is otherwise known as JAS 39.
There never was anything called the JAS 38 until Scorpio came along. The SAAB model 38 was supposed to be a light attack (A38) and trainer aircraft (Sk38) in the 1970's. It was cancelled early on, but got far enough in the development work to have its' own Swedish airforce designation number reserved (i.e. 38).
Krister
"Allen Wilkinson" wrote in news:fJhQa.1396$D25.93141 @newsfep1-win.server.ntli.net:
Anyone tried this ducted fan model from Scorpio ?
> It appears to me that the "Truly amazing performance with a 17 turn Buggy
> motor" is a little on the optimistic side !
>
> AW.
>
>
Truly amazing is an - 'interesting' - statement, that has many possible interpretations....:-()
From what I have read, it flies on the stock motor. Which is more than most ARF ducted fans do. You will need a catapult to launch it.
But seriously, if you want to do a proper EDF, spend the money on the hottest power plant you can, and the most efficient. Nothing is more disappointing than a jet plane doodling around at slow speeds.
I think there is a review somewhere on the E-zone.
Not at all. In fact full size jet designers now use turbofan engines in order to get a larger volume of air accelereated less - which works much more efficiently at subsonic speeds. This is teh simple way to get thrust egffciently.
Ducted fans have hopeless thrust at low airspeeds - the blades are fairly coarse cut, and are somewhat stalled at low inlet velocities, because in order to prduce any thrust at speed they need to do violence to the little air they get. Efficiency is always poor, and the only solution is to spin them at obscene RPM - 30-40k.
You need a very 'hot' motor - real 'race' territory capable of doing at least 40k RPM and a power pack to drive it to get serious performance.
The mega 16/15/2 motor looks like a serious contender in this region.
Also, ducted fans need to be doing the speed to get the thrust up at all
- slow launches may just end up in a condition where the model floats around slowly nose up. Its high drag, low speed. At that speed the fan doesn't have the thrust to get the model faster. The ONLY solution is to get the nose down and get some speed up. If there isn't the altitude....hence the use of bungee launchers to get up to 30mph or so, where the fan starts to get 'on step', and the model starts to 'fly'.
A friend an I had such bad experience with e Kyosho F16 - still there waiting for a bungee, a better pack and a brushless motor - that I decided to give EDF's a miss till I was both a better pilot, and understood how to get more power....
IMHO EDF's need at least 100W/lb to really FLY. Ok they will stagger around on less, but what is the point?
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