Setup is a JetFan 90mm with HET 650 motor on 6S (3S+3S) 4000's , this is the setup I took out of that POS Freewing Fiat G-91 with atrocious ducting that always felt overweight, underpowered and never flew half right
The next day, Saturday, I flew it with the CG at 115 mm and it flew fine, it barely needed any trims. I use the recommended 4S 4000 setup and it flies well, plenty of speed for a foamie . My latest CG is now at 130mm (see picture below).
My nosegear steering lingage kept getting undone at the field, so I had to put a collar to prevent that Z-bend from slipping out.
The elevator and rudder linkages (pushrods) were really flimsy, I had to make the whole assembly a lot more rigid to avoid a possible catastrophy on the maiden.
Given that the original had a wingspan of 9.46m and a length of 12.13m (L-59: 12.20m), whereas the model has a wingspan of 120cm and a length of 132cm, the scale is approximately 9.46m/1.20m = 7.9 :1 .
Of great relevance of the overall fan efficiency, defined as
efficiency = (mechanical work done per unit time) / (input power) , in e.g. (N.m/sec)/Watts
A good substitute for the above quantity is, based on simple formulas relating work to fan thrust and fan efflux:
efficiency = (const.) x thrust^(3/2) / (input power)
You would imagine that if somebody is really serious about designing an efficient fan they would take the time to actually do relative measurements of different designs, in order to figure out which rotor/stator design in the end is best.
Indeed that is how serious fan designers (eg WeMoTec, Daniel Schuebeler etc.) indeed do it ...
But then often a new design comes up (nowadays every other week, in some cases a copy of somebody else's rotor, with one blade added or subtracted so it don't look like a copy ) - without any clear measurements of anything.
If it is a clear shameless copy of a DS-51 fan, then it has to be as good as the DS-51, right ?
Then the relentless overhype follows ("20% more efficient than anybody elses fan'" - to the point that now the overall efficieny adds up to 110% ), and more adverts such as "best fan I ever tried in my xx" etc.
Now, the Jetfan 90 data is interesting and accurate enough to pull out :
1) the relative efficiencies of different motors in the JF
2) the very slow rise of efficiency with power/voltage
3) the large errors inherent in all these measurements
4) the wide spread in motor efficiencies (up to 31%).
The museum is located within a large airport in the Bourget suburb of Paris, and is the site the Paris Airshow (which takes place usually in June).
It has an amazing collection of - what else - French (mostly Dassault) jet aircraft, including some weird looking experimental aircraft, but also Montgolfieres, some very early 20-th century planes (Bleriot), some very nice WWII warbirds (including a FW-190A and a Spitfire Mk. IX) and two Concorde.
Initially I didn't do much to it as far as appearances, looked pretty good out of the box (my wife commented that it was my best paint job ever ) so I just flew it ... The large MiG-21 kept me busy with paint etc.
After almost a year of flying and probably 100+ flights, I decided to play around & practice with the airbrush a bit.