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Old Oct 16, 2003, 03:26 PM
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eSmasher's Avatar
Ayrshire, Scotland
Joined May 2003
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ZAGI performance - reality check req.

I fly a ZAGI 480 (UK variant of a 400 with a 480 motor) using 8x1300 NiMh cells and Gunther prop.

Just after I built it it flew fine according to the test pilot - I have gradually mastered it with a few vertical landings etc.

I now find that while I can roll I can't loop. I am not convinced by the rolls either I need to give full down when inverted to avoid the nose dropping.

I think I have allowed the CoG to move forward too far as I have put the lead back in after an arrival - does this seem a reasonable assumption?

Graham
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Old Oct 16, 2003, 04:14 PM
Single-task at best...
tim hooper's Avatar
Telford, UK
Joined Feb 2000
7,498 Posts
Graham,

If those are the AA-sized NiMHs, then you'll feel way underpowered compared to either 500ARs or 800ARs. I use my NiMH pack in my transmitter!

Make sure the prop is on the correct way for a pusher application too............

The CG (if I recall correctly) should be 8" back from the nose.

tim
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Old Oct 17, 2003, 03:22 AM
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Ayrshire, Scotland
Joined May 2003
448 Posts
The pack is the one recommended by Overlanderand the prop is the correct way round. I will check if I am still at 8" tonight.

I am no so much underpowered as under controlled I had to put the rates on to make it manageable but when I pull up for a loop it will go vertical for quite a while but won't go over the top

Graham
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Old Oct 17, 2003, 03:57 AM
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France
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Look closely to the CG, each time you "bump" make the batterie move, a small move can make a big difference.
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Old Oct 17, 2003, 07:51 AM
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Outside of Dyer, Tn. USA
Joined May 2000
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Welcome to the site No Rudder!
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Old Oct 17, 2003, 08:41 AM
Fiberglass dont bounce???
RandyK1's Avatar
Zion, Il.
Joined Sep 2002
2,408 Posts
Sounds like your CG is too far forward. (remember, 8" is only a starting point) Move your CG back a little at a time and test fly. You will be able to tell if its too far back if it gets too "twitchy" (easly overcontrolable) in this case just move it a little bit forward. I had the same problem with my 400X. I now fly a Unicorn (stock CG was 10") I had to play with the GC to get it to fly like I wanted it too,(CG is now 10 1/2") so now it flys great, tight loops & rolls are no problem and it glides forever. Before you start playing with the CG, remember to set your control throws back to stock, you can play with the throws after you fix your CG. Good luck & dont give up, you will be very happy with your plane after you take the time to do this......R.....
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Old Oct 17, 2003, 08:42 AM
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France
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Well thank you very much and hello every body.
Sorry for my English in advance.
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Old Oct 17, 2003, 01:05 PM
Blue Foam & a Happy Home
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www.DadsFunPage.com
Joined Jun 2003
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eSmasher - Thanks for asking a good question.

Everybody else - Thanks for the great answers.

My Zagi has been inconsistant. Some times it flys great and other times I have difficulty climbing. I thought maybe my charger was not peaking correctly, but now I suspect that I've been moving the battery around. I take it out each time to charge it and put it back in where it looks about right.

After reading your replies I will find the sweet spot and mark it for future reference.

Thanks again to all.
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Old Oct 17, 2003, 01:34 PM
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eSmasher's Avatar
Ayrshire, Scotland
Joined May 2003
448 Posts
Welcome No rudder - and don't worry about your English it is much better that my French and very understandable.

bradm - my battery jams into place so I set the CoG with some lead so even when the battery comes out or I swap it for the spare the CoG is unaffected.

I think I will need to play with the CoG tomorrow - looks like good flying weather.

Graham
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Old Feb 18, 2004, 07:54 AM
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Ayrshire, Scotland
Joined May 2003
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This thread is a blast from the past but I was rather busy and the weather just got better here.

Starting yesterday I moved my CoG back and today I got loops - not great loops - not even good loops - but loops. I realised I might be stalling it before it gets beyond vertical as I yank back on the stick too hard.

Some extra speed then a smooth gentle back pressure seems to work. A bit different to my SlowStick where you can pull turns as tight as you like (haven't risked loops with my e-glider).

I think I will move the CoG back a bit more as it is still well under control.

Perhaps tomorrow if it is sunny again (and my pesky work phone doesn't keep ringing - got to love working from home and flying out front- well 100 yards to the football field)

Graham
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Old Feb 18, 2004, 08:58 AM
The original Flying Pigs Sqd.
Up&Away's Avatar
Netanya, Israel
Joined Aug 2002
10,030 Posts
Bradm,

Does your battery have the room (and ability) to shift during flight? First thing to do is to put some velcro in the battery bay, and on your pack, then make some foam spacers so you will always put the battery back in at the same spot. That way, once you found the right position, you will always get back to it.

Don't forget to post some pics!
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Old Feb 18, 2004, 09:45 AM
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eSmasher's Avatar
Ayrshire, Scotland
Joined May 2003
448 Posts
The battery wedges in to place and is held with velcro. I use a block of lead taped down to set the CoG. I hope to move it back until I find a good spot then chop off some of the lead and move it forward to get the same CoG......

I will post a picture later


Graham
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Old Feb 18, 2004, 10:02 AM
The original Flying Pigs Sqd.
Up&Away's Avatar
Netanya, Israel
Joined Aug 2002
10,030 Posts
Instead of moving the lead back, decrease the amount of lead. You will improve the CG position, and improve the weight, thereby the performance!
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Old Feb 18, 2004, 11:50 AM
Blue Foam & a Happy Home
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www.DadsFunPage.com
Joined Jun 2003
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Up & Away,

I've experimented with different locations without much difference. I now think the motor is wearing out because performance is consistantly down - before it was more eratic.

Unfortunately my Zagi is down right now too. I was unable to pull up enough from the bottom of a loop to clear a chain link fence. Since the elevons were in full up, one of them snapped due to the instant stop. Should be a simple fix.
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Old Feb 19, 2004, 12:45 AM
The original Flying Pigs Sqd.
Up&Away's Avatar
Netanya, Israel
Joined Aug 2002
10,030 Posts
While you're at it, check the soldering to the motor and ESC. It could be a weak connection. I had something similar on my Unicorn, when I had a loss of power after a one point landing. Only two threads where still connected to the motor!

Also check your servos. After a crash like that, when the elevons are damaged often the servo gears are as well. I have made it a reflex that, when I see that no amount of any input will prevent coming into contact with a stationary object, I cut throttle and take my right hand of the Tx. The servos will centralize, and the chance of damaging the servogears are much smaller.
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