Predator III for the slope

[Steve P]

Not so scale, but very neat stuff. I've been so happy flying my RCRCM Strega during the last two trips to Cumberland/Highpoint that I decided a stable mate was in order. So, I've added a PIII to the mix.

My gorgeous Strega after a long fun flight at Highpoint...


I was able to custom order the PIII with a clashing color scheme, orange and black on top, black and yellow on the bottom. No worries about telling which side is up! (From order to delivery was 4 weeks and w/ EMS I was able to track it from the shop, across China to the airport in Beijing, and here to my door.)

3 meter span is a good size and at first glance this plane appears quite similar to the Strega, but has a different wing shape, a small bit more area, bigger flaps that extend all the way to the fuselage side, less of an angle in the center joiner and slight up turn in the outer section for very minor dihedral. The Strega is essentially an elliptical straight wing with some center dihedral only. The fuselage and tails are near identical between the two.





I just started this afternoon and this will be a quicker build than the Strega simply because I have one under my belt. The servo drives are the fussy part, all else is pretty standard stuff. For this air frame, I went with the new KST X10 wing servos sourced from AMain Hobbies as both KST and MKS fit the supplied frames -- X10 = 104.16 oz-in @6v | 131.93 oz-in @7.4v | 149.98 oz-in @8.4v



And... a bit more motor in this one via a 35mm 920 KV Leopard outrunner sourced from Altitude Hobbies. Power will be 4S 1800 mAh turning a carbon 13x7 just like the 780 KV Strega. It's really just to get the plane out over the slope.



Its purdy...

[Steve P]

Put in some time today getting all six servos in place, setting up the v-tails and making up the wiring harness. All take time but overall not too exciting. I’m waiting on an order that includes the receiver for this bird.

I do prefer to “pot” the servo frames by cutting squares of plastic grocery bags, putting that over the frame and then bolting the servo into the frame. A healthy dose of epoxy thickened with colloidal silica on the frame and wing skin and then weigh it down. The epoxy tends to work into the narrow spaces in the frame and between it and the servo. When all cures, remove the servo and peel away the bag. Results in a super tight fit.

[Steve P]

Another maiden flight success from the past weekend.

Predator III had its shake down on Sunday. Definately had too aggressive elevator throws and it needed a half ounce of lead right behind the motor (not a worry as this is for the slope). Performed beautifully, caught a nice thermal in the flight after throws were tamed and the CG brought a touch forward. Still on that ragged edge of too far back that makes for good thermal indication and inverted on the slope. Lands slow and beautifully. I'm really impressed by the new KST X10 thin wing servos. Very tight and strong.

Flew it on my PowerBox CORE + PBR-8E receiver. Lots of good mixes for snap flaps; flight modes of camber, reflex, cruise; option to mix aileron to rudder if I want to thermal lazy; and, landing mode variable flap to elevator compensation. Motor on the left slider, flaps on the left stick.

Probably won't see too much action outside the Cumberland events, but the fact it would thermal quite well was an unexpected surprise that may see it making the trip to the local field more often.

Happiness.

[Steve P]

The admins let me know there was a question about build and CG. While there is no instructions or manual for these planes, Paul Vessey did create his own manual for the Strega which is especially nice for servo install/setup. The PIII with the same fuselage and a slightly different wing pretty much follows along all the same lines and 98mm was my CG starting point which I then moved slightly forward.

https://www.manualslib.com/manual/12...cm-Strega.html

FWIW, RCRCM in the sales website states the PIII CG as 98mm back from the leading edge. The Strega is at 115mm. So all of this is the right neighborhood to start and then refine for personal preference.

Note too above, I went with a simple motor. Mine is modestly powered simply to reach the slope lift way out at Cumberland. It’s not even warm liner class.