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Curtis Condor biplane twin


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1 hour ago, Martin Harris - Moderator said:

Nobody's mentioned the possibility of a dodgy elevator servo as far as I can see. IIRC you had complained of occasional random trim changes in pitch which could be signs of an ageing feedback pot in the servo preventing accurate re-centring - maybe it finally bit big time...

It's a good question Martin. But the servo is a new JR NX3421 x-bus digital that was and is working perfectly. 5kg torque is more than enough. There was no slop in the linkage either as that was checked prior to the crash.

I think it may have been the gyro giving the odd trim change problem? 

Edited by David Ovenden
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1 hour ago, Martin Harris - Moderator said:

Long shot but are all the servos digital?  I have seen the odd glitch from mixing servo types in the past.  Probably not an issue with modern transmitters but best to consider all possibilities before committing your hard work to the air again!

Yes, all 4 servos are the same type. All JR digitals, all the same spec.

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  • 3 weeks later...

Rigging angles all checked and model weighed and balanced. Amazingly it now balances slightly nose down with only one lipo pack instead of two. So I managed to shed nearly 400g of weight and still have the model balance on the CG.

I removed the servos from the tail and moved them to the nose;  removed some plywood mounts; changed the Robart wheels for foam ones; removed the gyro and got rid of some extension leads. And this has allowed me to use one 4s 3700 lipo pack I stead of two.

The good news that most of the weight was lost from the extreme nose and tail of the model so hopefully that will also be beneficial. Will now have to see if the rebuild improves the flight characteristics  

20220316_215703.jpg

Edited by David Ovenden
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Well today was the day! I was able to test fly the Condor. It is definitely an improved model. After the flights the Tx trims were all still at "neutral".  Take-off was good and a landing was no problem either in spite of a fair breeze a bit off the axis of the runway.

Looks like just one 3700mah Lipo will give 5 minutes of mixed flying which is not unreasonable. One could use a larger capacity lipo but it would need to be located further back in the fuselage to avoid the model being nose-heavy.

It was definitely worth repairing the model and making the modifications which have very much improved the flying characteristics of the model. Losing the gyro and shedding 450g of weight together with tweaking the top wing incidence was a good move it seems!

Thanks to Paul for getting some video of the flight.

 

 

Condor test flight 1.jpg

Condor test flight 2.jpg

Condor test flight 6.jpg

Edited by David Ovenden
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10 minutes ago, David Ovenden said:

Thanks Paul. Was it the wind blowing or me shaking?

 

Someone commented on how my Gypsy Moth was flying on its test flight until I explained its wobbles were merely reflections of my trembling fingers so I empathise with your nerves ?

 

Looks beautiful and you deserve a lot of credit for your fortitude.  As a very good designer/builder modeller once said to me "It's a hard game sometimes."  and it is. 

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