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Sep 25, 2007, 09:18 PM
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jasmine2501's Avatar
Discussion

Hobby-Lobby/Art-Tech/Sapac Pitts maiden flight report


I cried.......













Out of sheer joy!
This plane flies very nicely overall. She is sublime, demure, reminiscent of the biplanes of old. I was really overcome... I don't know if it was the chill in the air, the beauty of her silhouette in the twilight, or the flight itself, but I really did cry. She's better than I expected, but not anything close to the Pitts in the RCGroups "review"

I put review in quotes because this one I have is clearly not the same one they sent the reviewer. It flies very much like a scale biplane should, but is not aerobatic or wild, not in the least - not like the real Pitts, but more like a Jenny or Tiger Moth. Take-off roll was straight but long, with smooth acceleration and a perfectly level lift-off with no surprises. Really a thing of beauty. The plane is somewhat under-powered, and slight up elevator will make it stall on full power - this is with a brushless motor. It is clearly very capable with a fast roll rate, and good response overall, but it needs more speed to do aerobatics like in the 'review' video.

This is not a bank and yank plane at all, requiring rudder to make a proper turn. Overall I'm very happy with it though... I think it might be ok for a second plane, but it's not a trainer. I had to be very light on the sticks to avoid a stall, and you have to wait for it to climb, you can't just pull up and let the motor do the work. Maximum AOA is maybe 15 degrees. You have to fly the wing, and be very careful with the elevator. Landing was very nice, but you have to fly it in, no cutting the throttle and gliding down.

I might upgrade this with a better motor, but I love the way it flies right now, very much like an old-fashioned biplane!
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Sep 25, 2007, 09:34 PM
Registered User
Good for you Jasmine

Now....for how long will you be able to resist a re-power?? ;-)
Sep 25, 2007, 10:09 PM
Suspended Account
Quote:
Originally Posted by jasmine2501
It flies very much like a scale biplane should, but is not aerobatic or wild, not in the least - not like the real Pitts, but more like a Jenny or Tiger Moth. <snip>

I might upgrade this with a better motor, but I love the way it flies right now, very much like an old-fashioned biplane!
Hi Jasmine,

Are you pulling our leg? A Pitts Bipe that flies like a Tiger Moth or Jenny????

The ones I've seen flying looked to be very twitchy and way beyond my skills...

You must be a natural born flyer. Good going!

Chuck
Sep 25, 2007, 10:33 PM
Rocket Programmer
jasmine2501's Avatar
Quote:
Originally Posted by NoFlyZone
Hi Jasmine,

Are you pulling our leg? A Pitts Bipe that flies like a Tiger Moth or Jenny????

The ones I've seen flying looked to be very twitchy and way beyond my skills...

You must be a natural born flyer. Good going!

Chuck
It would be twitchy in the wrong hands. With this power setup, you have to fly it gently. It is not deliberately designed to fly like a Jenny, but it doesn't have enough power for aerobatics, and it won't tolerate too much input from the pilot. I'm saying that you have to fly it like a Jenny, or you're going to stall it. Clearly there is less power here than there should be. It could be a factor of altitude or a cheap motor... I'm getting 7 amps and only 84 watts. As I said in my build log before I even flew it, I would like to see more power in a plane designed for aerobatics. I tried a couple rolls, but I could see right away that it wasn't capable of a loop. It rolls fast, when you ask for it, but it does not hold altitude when you do it, and you have to stay on top of it to recover from the stall. I'll try to get some video at some point, but I didn't have my camera today. One other person was there and he really enjoyed watching my flight. He was flying an "Ultra-stick-like" glow plane of some kind, and he landed so he could watch this one fly.
Sep 25, 2007, 10:47 PM
Wandering IT geek
ronin4740's Avatar
??? Isn't the Art-Tech Pitts basically the same biplane as the Cox Models Christen Eagle shown here:

http://www.coxmodels.com/prodinfo.asp?number=006400

If so I've flown the Cox version and would say that the kit has reasonable, not stunning power. Certainly enough ponies to do basic acrobatics though I've done loops and rolls with her. I haven't flown mine in a while because the weird sized Lipo it comes with went dead on me.

Maybe you have a bad motor?
Sep 25, 2007, 10:59 PM
Rocket Programmer
jasmine2501's Avatar
Quote:
Originally Posted by ronin4740
??? Isn't the Art-Tech Pitts basically the same biplane as the Cox Models Christen Eagle shown here:

http://www.coxmodels.com/prodinfo.asp?number=006400

If so I've flown the Cox version and would say that the kit has reasonable, not stunning power. Certainly enough ponies to do basic acrobatics though I've done loops and rolls with her. I haven't flown mine in a while because the weird sized Lipo it comes with went dead on me.

Maybe you have a bad motor?
Yeah I'm pretty sure it is the same plane. If I had more power it would be very aerobatic, but it doesn't generate more than 25mph in level flight on full power. It's possible that I have a bad motor. I'm sending a message to Hobby-Lobby and asking if the amps and watts I measured are correct. I should get maybe 125-150 watts for decent aerobatic flight, and maybe a little more for 3D. I have a motor that pulls 180 watts with a 9x4.7 prop, and this one has a 10x4.7, so if I swap out the power system, that ought to work. I will try to get a replacement though, depending on what the dealer says... because according to their own sales information, it is not supposed to fly like this. Not knocking it though, it's very docile if you are careful with it, but if you try to pull up into a steep climb, you're going to pay.

I sent a question to them already about the battery bay being too small, but they haven't responded to that, so maybe I'll call them. They always return my calls, and seem to be very good about that.
Sep 25, 2007, 11:31 PM
Account closed
jasmine,

Those 84 Watts are measured value with the Watt Meter or was it calculated "guessed"

If you are pulling 7 AMPs at wide open then, the Under Load Voltage of a typical 3-Cell Li-POLY would be somewhere in the level of 10.6 Volts so, really you only have ~77 Watts.

Why not try a 9 X 7.5 Propeller to increase airspeed and dynamic thrust? Have you measured your models RPM at the propeller?

I am sure your Pitts is designed for airspeed and a higher pitch higher than what you have would be a great improvement assuming the motor can take the increased AMP draw.

Thank goodness your Pitts is light enough otherwise you would not be posting such a great "crying of happiness" review here. I have an OLD GLOBAL PITTS and it needs airspeed to stay afloat otherwise she tips stalls in a heartbeat!
Sep 25, 2007, 11:38 PM
Rocket Programmer
jasmine2501's Avatar
Yeah it's measured with my watt meter. I looked at the specs again and the motor is rated for 15 amps, the ESC for 18, and it's supposed to give 110 watts. The recommended prop is a 10x6, but they sent me two 10x4.7 props? I'm going to try a 10x6 if I can find one, and I'll see what I get with that. I have a 10x6 from my Slow Stick, do you think that would work? It's one of those orange ones that comes with the Slow Stick.
Sep 26, 2007, 08:45 AM
Off we go.............
SabreHawk's Avatar
Quote:
Originally Posted by ronin4740
??? Isn't the Art-Tech Pitts basically the same biplane as the Cox Models Christen Eagle shown here:

http://www.coxmodels.com/prodinfo.asp?number=006400

If so I've flown the Cox version and would say that the kit has reasonable, not stunning power. Certainly enough ponies to do basic acrobatics though I've done loops and rolls with her. I haven't flown mine in a while because the weird sized Lipo it comes with went dead on me.

Maybe you have a bad motor?
Yup, I got the same. Finally maidened it on sunday, and boy what a nice experience it was. It seemed so smooth, graceful and looked like it was on rails. And was much easier and predictable than I was anticipating. Very responsive yes, but twitchy no. Though ya gotta really watch it on the ground, it's short tail will have it in a ground loop quick. But that's the characteristic of any plane with a short tail coupling.
Yes, the battery. Many have stated the same on that fat thing.
I did however find what appears to be a good replacement at United Hobby.
http://www.unitedhobbies.com/UNITEDH...idProduct=5635

If the ad is correct it is the same dimensions and wieght as the original Cox battery. But at 1500 mah instead of 1800. And it has a balance plug too, and what appears to be the same deans clone soldered on the output leads.

Boy im really wanting to get back out there and fly her some more, but rain is dominating things over the next four days so................
Sep 26, 2007, 09:18 AM
Rocket Programmer
jasmine2501's Avatar
I used my TP 900 battery and it fit perfectly, but with the battery they sent me, I couldn't get the CG right... it is a higher capacity, but it's lighter than the TP 900... and I nicked the insulation on the China battery somehow on that plastic. Will fix that, open it up a bit somehow, and get that one to fit. I might have the CG too far forward, but for a maiden flight that's good.
Sep 26, 2007, 09:32 AM
Off we go.............
SabreHawk's Avatar
Hmmm interesting. My Cox Christen Eagle balanced perfectly with the stock 1800mah one. And not only that it rquired no trimming whatsoever once airborne, all I did was make sure all links and such were adjusted accordingly and all surfaces were zero'ed out straight and flat.

Jas, what kind of flight time do you get from that TP-900 ?

The Eagle is supposed to get 10min. on the 1800mah. So im wondering.
Sep 26, 2007, 12:05 PM
Rocket Programmer
jasmine2501's Avatar
Quote:
Originally Posted by SabreHawk
Hmmm interesting. My Cox Christen Eagle balanced perfectly with the stock 1800mah one. And not only that it rquired no trimming whatsoever once airborne, all I did was make sure all links and such were adjusted accordingly and all surfaces were zero'ed out straight and flat.

Jas, what kind of flight time do you get from that TP-900 ?

The Eagle is supposed to get 10min. on the 1800mah. So im wondering.
well, I called them and they said I should be getting a lot more power, so that would cut down the flight time. I got about 15 min and the battery was barely drained at all. I'll update this thread when I try it with the correct prop. They said it is supposed to be a 10x6, and they said at this altitude I might even try an 11x7...

And yeah, that's what I meant by "no surprises" The plane was nearly perfectly trimmed from the start. I trimmed in one or two clicks of right rudder, and that straightened it out perfectly.
Sep 26, 2007, 03:42 PM
Suspended Account
Quote:
Originally Posted by jasmine2501
I got about 15 min and the battery was barely drained at all.
Hi Jasmine,

You got 15 minutes of flight time and only barely drained a 900mAh battery?

The Pitts has a 33" wingspan and weighs 22 ounces. Even if you used up half the 900mAh battery, that's the equivalent of an 1800mAh battery getting a full hour of flight time on the Pitts. The Pitts is definitely not what anyone would call a 'floater'.

Something doesn't seem right here. Not trying to question your veracity at all, but this is really strange.

Chuck
Sep 26, 2007, 04:11 PM
Rocket Programmer
jasmine2501's Avatar
Quote:
Originally Posted by NoFlyZone
Hi Jasmine,

You got 15 minutes of flight time and only barely drained a 900mAh battery?

The Pitts has a 33" wingspan and weighs 22 ounces. Even if you used up half the 900mAh battery, that's the equivalent of an 1800mAh battery getting a full hour of flight time on the Pitts. The Pitts is definitely not what anyone would call a 'floater'.

Something doesn't seem right here. Not trying to question your veracity at all, but this is really strange.

Chuck
Yeah you're tellin me... it was really underpowered (read up) - when I took the battery off, it still had 11.9V - that's a little less than half drained, I think. It was pulling 7 amps when I tested it, so really it should have only lasted about 8 minutes... yeah something is not right. I'm trying a 10x6 prop and see what happens then. It was a maiden flight, so I wasn't pushing it, but it should have drained the battery nearly dead. And no it's definitely not a floaty plane at all... it stalls when you cut the power a little or pull up. I had to fly it down for the landing on nearly full power. Again... I should be getting way more power out of it.

Oh, and no way does it come anywhere close to 22 oz. It is super-light, even with the battery... not sure where you got that number, but my Slow Stick is 21-22oz, and this little thing is way lighter.
Sep 26, 2007, 04:36 PM
Suspended Account
Quote:
Originally Posted by jasmine2501
Oh, and no way does it come anywhere close to 22 oz. It is super-light, even with the battery... not sure where you got that number, but my Slow Stick is 21-22oz, and this little thing is way lighter.
http://www.hobby-lobby.com/pitts-bipe.htm

Chuck


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