31 May 2010

Back to Witblitz Racing

The first foray in to Witblitz racing had been pretty hard work with an evil handling plane, which disintegrated as the day went on. Subsequent comms with Christo van der Merwe and Andre Killian suggested a version 2 and a visit to the coast by top racer Christo van der Merwe meant a quick Saturday night build as he was the only local source of Uhu Por glue, that I could locate at short notice.
It was re-match for Russ and Dave against Pylon boffs Pete Sherliker and John Dorse, with Christo there to stir things up. It was disappointing for all when the elevator servo on Christo's plane failed on first launch but he stoically re-assembled the sweet flying plane with Uhu and masking tape, so we were able to see it in action later in the day.
It is worth summarising the changes because the plane flew on rails from the first launch and was light years ahead of my first attempt:
1. Use only Uhu Por glue - I even made Uhu Hinges (Christo and Andre).
2. Move the CG forward from the 66mm recommended on the Witblitz site to 50mm - a must and Russ also smoothed up at the new CG point...... (Christo).
3. Glued the wings direct to the fuselage as I had seen evidence of the lacky bands lifting during high G turns and lacky bands are a pain (Andre).
4. Dispensed with all forms of pretty covering, to dramatically lighten the craft (Andre) - I suspect it would have mid air crunched just as badly, anyway.
5. Fitted single instead of dual ailerons, which was lighter and made for smoother response (Christo).
6. Moved the horizontal tailplane to the fuselage bottom ala "Stik" to ensure a better bond to fuselage and maybe tame the pitch control.
7. I used parkie foamie theory and added a 4x1 mm spar top and bottom of the wing - extremely rigid compared to the alarming bend in Christos, not that it seemed to slow him for a second.....
8. I noticed Eric Arnaud had beefed the horizontal tailplane a little and that the flappy tailplane had been the source of most of previous misery for me, so added some 4:1 mm carbon to the hinge line and part the way along (obviously not at leading edge).
The jury is out on the spar items in 7 and 8 but obviously added very little weight. John Dorse scoffed a little at my foamie efforts but did not have to hang on to the bucking bronco at that first event ;-) I also wanted to the stay with orignal Depron type theme.
Below is my comms to the locals, probably a bit sketchy on exact detail:

I gained a whole new respect for Witblitz planes yesterday. Moving the CG so far forward so far was magic – Russ started on two 13 lappers, same as the first race meet we did, but then got in to his straps and clocked a 15 lapper and then a 16 lapper! Right up there with the hotshots who were still doing more laps but more cuts. Christo did 19 laps with two cuts so 17 laps his was the best of the day. Both John and Pete after cuts were 16 lappers as well. I was chuffed, starting with 14 then 15 less one cut and confetti – mid airs with foam suggest EPP may be worth a look as I doubt film covering will help the Depron much....

Christo flew like F3B speed rather than the inefficient “round the pylon” we do, once his plane was rebuilt (his elevator servo failed on the first launch). Clearly better but hard to get used to.

Not sure if the 4x1 mm wing and tail plane carbon spars helped on stability but the plane flew with Velocity like locked down stability and was verrrry light, using only one aileron and the 1100 Hyperion pack. I also moved the elevator to the bottom, ala Mini Stick. Chalk and cheese compared to the old one and Christo was most impressed. I would say one aileron is a Witblitz must for me from now on, absolutely vice-less. Only thing was mine was outboard and Christo’s inboard, both worked fine but I suspect Christo is on to something.

No comments: