Christmas Curare EP

It's gone very quiet on the Forum, Everyone must be beavering away making things.... :whistle:


Virtually done now. Along with the cut-out in the cowl to help force air through the fuselage and over the ESC, I cut out an exhaust hole on the underside of the fuselage and fitted this nice little exit (it is a Habu 2 exit that was spare and just happened to be blue). Spinner was modded to allow air over motor. (the manual recommends no spinner for EPs) but it would not look right. Ruin the sleek lines. Got the idea from my EFX racer.

Replaced the UBEC which I suspect is 3 amp burst 5 for a Hobbywing 7.5 amp UBEC, 5 amp continuous. No issues now.

AUW = 3.25kgs Motive Power: Tried a 12 x 8 on 6 cell = 1409 watts, 61+ amps. not a problem for the 100 amp ESC, but the motor max is 60 amps apparently? But there again it is not as if you flying WOT all the time. Came down a bit using a 12 x 6 = 1105 watts, 50 amps. I think the latter is adequate for now. Anyway, I am using it as sport plane and it will be me on the sticks. :lol: Fast taxi down the road to check steering. All's OK. Tucked away nicely in the hangar till whenever.

With the forecast at present and after Christmas the forthcoming kitchen rebuild and living room decorate :ohmy: it could be two months before freedom again

Phil
6" pitch won't be much good, this model needs a bit of speed, you need less diameter and more pitch 8-9" is what I would be looking at, obviously go down on diameter though.

MikeSeale wrote: Whilst the Curare will fly well with a 11x7 prop, we have found whilst it sounds powerful, it actually just stirs the air and makes a lot of noise past about 3/4 throttle. Chris is running a 11x8 on his Wot4 and I'm using a 11x8.5 on the Blue Angel. These seem to load up the motor better and produce a much nicer result. You could also try a 12x6.5 or 12x8.

Jon, going by the above info, I have tried 11 x 7, 11 x 8. Also the 12 x 8, 12x6. Another option maybe is the 11x10 which I don't have?

Jon, C of G was at 1100 mm

Cg should be fine there, maybe a touch nose heavy if anything, assuming you meant 110mm, if you really are at 1100mm, you are in trouble!!

When I was running 60 2 strokes in f3a in the early 90s, we were using lots of pitch, commonly 12 x 11 to 12 x 13, airspeed was good back then

PhilF51 wrote: AUW = 3.25kgs

Please can you weigh the fuselage, battery and wing separately? My Blue Angel weighs 3.326kg which comprises 1.608 for the fuselage, 0.663 for the battery and 1.055 for the wing. It would be interesting to see where the extra 100g comes from considering both have the same motor and (I think) the same battery capacity (4000mAh?)

For Mike - Using the same digital kitchen scales (verified using a known weight) as used to weigh the Curare assembled.

Fuselage = 1555 gms, wing = 1030, 6 cell Turnigy 4000maH 30-40C = 645. Total weight adds up to 3.230 kgs

Thanks for that, Phil. It's interesting to note that my Blue Angel airframe, built using 1970's techniques (thick planks of balsa and a foam wing), is just 78 grams heavier if we used the same battery. I think that most would assume that a modern laser-cut airframe would be a lot lighter.

Mike

After it's maiden on Sunday last thanks to Jon although I think Mike was itching to have a go some tweaks and adjustments need implementing. CG could do a little move. Judging by the trim settings a slight mechanical adjust on the ailerons. Rudder is a bit more though, showing up on the vertical.. Jon thinks it may be more speed required or some motor thrust line adjustment.

Easiest route is to increase speed. The prop used was 12x6 which pulled around 50 amps static. Initial prop at time of building was 12x8 but this pulled over 60 amps. Today, Wednesday 16th December Santa arrived with some props, one of which is an APC-e 11x10. Without to much ado it was reamed and balance checked - perfect. Time for another test.

A 6 cell lipo 4000 maH at 96% capacity, Firsr run-up to half throttle gave readings of 28 amps / 685 watts. Idle back for a moment then wind it up to WOT. Reading was 61.5 amps 1220 watts. Did this twice and not much variation of readings.

Unplugged LiPo from the ESC but left the meter connected which now scrolls thought last readings. Battery volts 24.11 (82% cap); Amps Peak = 64.5; Peak Power = 1311 watts; amps used = 364 maH. These figures are at a static test so some unloading of current should bring drop in current. Just how efficiently the prop uses this power is yet to be tried out. :whistle:

<em>As a footnote: This same motor fitted in the Wots Wot running off 5 cells and 13x8 prop developes 1200 watts at around 60 amps. It certainly hauls the heavier draggy biplane around easily</em>.

PhilF51 wrote: Rudder is a bit more though, showing up on the vertical.. Jon thinks it may be more speed required or some motor thrust line adjustment.

Just to be clear, yaw tracking in a vertical is nothing to do with speed, it needs a side thrust adjustment, what I said was that you need to get the right prop for it first before we can fine adjust the side thrust, as prop choice has an effect.

With the 12x6 it flies too slowly (as predicted ) which is particularly noticable on the vertical lines.

Hate to say I told you so

JonTappin wrote: Phil
6" pitch won't be much good, this model needs a bit of speed, you need less diameter and more pitch 8-9" is what I would be looking at, obviously go down on diameter though.

Thanks Jon. I think my text is slightly ambiguous, leading to a misconception of wot I ment! :lol: