So Ugly It's Cute

[t-turley]

Here's my latest: a profile sort-of Piper Pawnee. It has a WS of 36", area of 200 in^2, and weighs 8.9 oz. Equipment is a GWS carbon brush motor with 5.9:1 gb, 8 300NiMH, GWSR4P, two CS21BB servos, Pixie 7P, and a Dean's base-loaded antenna. Covering is RA Microlite. The first flights were short test hops from one end of my driveway, into the cul-de-sac, land, and back into the driveway. The APC 9x4 wasn't enough to get airborne; the 10x4 was much better, but I think I'm going to try an 8x6 or even 9x6. I intended for this plane to be a true Front Yard Flyer - in fact, that was its name - but its turning radius is too large for my front yard and driveway. Anyway, here it is:

Tony Turley

http://www.rcmicroflight.com/upload/TT-FYF.jpg

[cometkid]

Well, I'd have to say beauty is in the eye of the beholder. Great job!

I have been mulling over a Pawnee PA-25 as a subject after getting a Photo Pak from Bob Banka and a 3-view that was identical to the subject (color and markings). The kicker was I've been doing the BIG electric thing and I was going to draw up a big one for a geared Astro 40 on 20 cells. But, then I had to consider the size of it and the dimensions.

Now, after doing the Pico Stick so many evenings, I decided to do the first model as a profile for the GWS motor. The Astro 40 project is on the shelf.

Your profile Pawnee has inspired me to begin to draw on paper after years of inactivity. I know it's an ARF world today. But I hope there are modelers in the group who would agree with me that designing and building from your own set of plans is true satisfaction.

[jimwalker]

Nice job!!

It looks fun, not ugly. let us know it's flight characteristics when you get a chance to really open her up.

I'm with you Cometkid. I definitely prefer at least building my own planes. Designing one and then building is even better. I turn my nose up at ARF's. Doing it yourself is half the reason I'm in this hobby!

Jim

[flyingbuddy]

I agree there, I spend more time designing than building or flying.
However, flying and crashing an ARF is a lot better on the nerves, no emotional investment. Several times I've spent hours and hours on a plane, only to destroy or mame it on the first outing. Boo-hoo!

[t-turley]

Comet & Jim: thanks for the complements. I took it out for a shakedown this evening at my church parking lot down the street. It still needs some shaking out :D I had originally balanced it out at 40% of the chord, because it has a very long tail moment and large tail surfaces. At the suggestion of some other Ezone members, I moved the pack as far forward as possible, which moved the CG to 25%. The plane really felt sluggish, and barely climbed - except for the takeoff, where, as you see below, it needed lots of down trim. But all it did was climb to about 4', then mush ahead, barely flying. I can say that its stall characteristics are gentle, to say the least. I need to rearrange the pack velcro to get it back to 40%, and I'm going to try a 9x6 slowfly prop, instead of the 10x4.7. The only other SF props I had with more bite were 10x7, which I think would be way too much for the GWS carbon brush motor on 8 cells :rolleyes: I know the plane has enough power, because it weighs less than my Pico Cub F, which flies just fine on the DX motor. Is it possible my Pixie 7P isn't allowing full power through? Another possibility is the batteries: the cells are brand new, and this was only the second charge on them. Anyway, here's the takeoff, shot by my 10 year old son:

Tony Turley

http://www.rcmicroflight.com/upload/PawneeT-O.jpg

[Buddly6]

tyr it with other batts and see what happens

[jimwalker]

If you are using NIMH batteries it takes at least two cycles to see full voltage under load and 4-5 cycles to begin seeing the rated capacity. NIMH batteries are touchy as well, if you quick charged them on the first cycle, you may have injured them. Depending on your charger and methods, your pack may not be getting a full charge. Is the pack warm (not hot) to the touch after charging? If not, your charger may be shutting off before the cells are fully charged.

If your using nicads then that's not the problem unless your pack is bad. I wouldn't think your ESC is a problem, they usually work correctly or not at all.

The CG shouldn't effect it's ability to climb unless it's so grossly nose heavy it requires full up elevator just to keep it's nose up, or it's so tail heavy that it requires almost full down elevator to keep from stalling.

Lastly, you might check all flying surfaces to confirm there are no warps and that the wing and horizontal stablizer are square to each other.

Hope this helps and keep us posted....

[ 08-10-2001: Message edited by: Jim Walker ]

[t-turley]

The cells were definitely at least part of, if not the whole problem. I tried them on two different chargers, and they false peaked on both. They also got very warm after just 10 minutes at 500mA on a timed charger. They are taking less and less on each charge :( When I came home today, I put them on a slow charge. I'll cycle them a few times at slow charge only, and see if they revive. They may be toast. Bummer.

Tony Turley

[t-turley]

Originally posted by t-turley:
<STRONG>The cells were definitely at least part of, if not the whole problem. I tried them on two different chargers, and they false peaked on both. They also got very warm after just 10 minutes at 500mA on a timed charger. They are taking less and less on each charge :( When I came home today, I put them on a slow charge. I'll cycle them a few times at slow charge only, and see if they revive. They may be toast. Bummer.

Tony Turley</STRONG>

Well, I have to retract the above statement. I was basing it on tests with the new plane only. I'm lucky I didn't fry the cells. I've read through the instructions on the Pixie 7P several more times, and the symptoms being shown by the plane were a clear sign of early BEC shutdown. I decided to try the cells with another slowflyer - and that plane tried to fly out of my hand across the room. I also removed the GWS system from the new plane, and soldered a 280BB in place, with the same 8-cell NiMH and a 3" 3-blade prop. Everything worked perfectly. After several hours of testing this morning, I've come to two conclusions:

1) The GWS carbon brush motor is either drawing too much current or creating a lot of noise. According to the instructions, either one will cause early cutoff. I guess I'll try soldering on another capacitor, and see if that makes a difference. My Amp meter is analog, but should still give me a rough estimation of the kind of current being drawn.

2) Compounding the problem, the spur gear was slipping badly on the shaft. That is easier to fix.

I'll work on the above problems later. I need some time to clear my head right now. :)

Tony Turley

[t-turley]

Frankly, I am puzzled. I had a brand new GWS carbon brush motor, so I gave it a two hour underwater break-in, then carefully dried and lubricated it, and installed it in my newly repaired gearbox. No gear slippage this time! I installed it back into the plane, and fired it up: Darn!! :mad: The stupid thing is only getting up to about 1/3 power, just enough to taxi across a carpeted floor. I tried another pack of cells, and got the same results. I know it is not the Pixie 7P or the cells, because they work fine with my 280BB. I guess I could have gotten two bad carbon brush motors in a row, but what are the odds of that? The funny thing is that the motor sounds like it is trying to "get up on step", with brief bursts of higher RPM - sort of like a glow motor that is running too rich, and is trying to reach optimum RPM, but cannot. I guess I'll have to drop back and try the DX motor or its equivalent, and see if that makes a difference. The plane is too small for a 280. Are there any small gearboxes that will accept the 3mm bearings used in the GWS gearbox? Questions, questions...

Tony Turley

[jimwalker]

I've read many posts now about the new carbon brush motors burning up quickly. I bought one and have about 5 flights on it so far with no problems. Maybe GWS produced an entire lot that was bad and depending on who you buy your motor from, you may get nothing but defective motors.

[groundloop]

That Pawnee is beautiful. It has gotten me to start thinking about building profile planes. I used to think that they were ugly, but, after several stick planes, they are an attractive alternative. I know a guy who used to fly the full size Pawnee and he said that they were a "kick in the pants". I have experienced a similar problem with a GWS motor. I think that I may have ruined the brushes during a hot run. It ran about 1/3 to 1/2 power with the surging that you described. It was old so I threw it away and got another one, that solved the problem!

[t-turley]

Thanks for the compliment. I've tried a couple of other motor combos since my last update, and I'm still not satisfied. The latest was a Mabuchi 50 disguised as a Dymond 1, geared 5.89:1 with various props and battery combos. Even with an APC 10x7 and 8 300NiMH, it was anemic. So I'm going with my final option, which should have been my first option: a geared DM20BB. I have one running in my GWS J3 F, and the plane has power to spare. I hope to have the gearbox finished this afternoon, and I'll post pix when I do.

Tony Turley

[ 09-08-2001: Message edited by: t-turley ]