Hoverfly X8 setup

[Dbasileccim]

I am converting my quad to an x8 and want some simple advice or just being pointed in right direction. I have flown hoverfly flat octo and hoverfly quad for over year and just need some advice on my first "coaxial"

I remember a lot of discussion about props. Smaller bottom larger top (I think that is what I remember). Also I think I remember that the bottom props need to be mounted "upside down"

Any other advice would be appreciated.

Thanks.

Dennis

 

[jes1111]

Higher pitch props on the bottom is the usual approach. I run 14x4 on top and 14x5 on the bottom.

 

[redridinghood]

You can also keep the same props and run a custom mix with a 15% higher speed on the bottom motors.

 

[Droider]

You can also keep the same props and run a custom mix with a 15% higher speed on the bottom motors.

RRH, you doing that in the custom mixer of the WKM?

I would have thought that would have been pre programmed in the mixer selection when you choose Y6 / X8..

I run the same top and bottom and found this the best in the real world of battery use and performance.

Dave

 

[JZSlenker]

I run larger, higher pitch props on the bottom of our X-8.

 

[Webheadfred]

I also run a 1" bigger prop on the bottom and more pitch on the bottom prop. However, I have run 11x47 on the top and bottom and the HFP handles it perfectly.

 

[jes1111]

Just about any top/bottom combo will fly - it's in the nature of the FC to allow for all sorts of imbalances and discrepancies. The oft-quoted "loss of efficiency" means you will get slightly shorter flight times with a coax versus the same components arranged in a flat layout. This "loss of efficiency" occurs because the bottom motor ends up doing less less "work" than the top one, i.e. it consumes less watts from the battery, due to the faster airflow that the bottom prop is experiencing. A small increase in the bottom prop's pitch (say 20%) should allow it to get a better "bite" on the fast moving air from the top prop, thus it will be able to contribute the same amount of work (consume the same watts) as the top. Nevertheless, there are many variables involved - the particular prop design, the spacing between the props, the size/profile of the arm between them, the rpm range within which the motors are operating, etc. Therefore it's impossible to say what will work for any particular machine.

An easy test is to measure the temperature of the top and bottom motors immediately after a typical flight. They should be the same temperature, i.e. they've consumed the same watts. If they are not, the hotter one is doing more of the work than the cooler one and you may want to adjust something . Remember, too, that you are halving the number of arms, so there's a weight reduction there to balance against the "efficiency loss".

 

[DucktileMedia]

I do wonder though, if the weight of 4 extra carbon fiber booms is even noticeable to the heli. I know there are mounts as well but all in all this would seem to be a very minor weight addition. it's really for the smaller size more than anything. personally I want my heli to be as large as possible in the air, the one thing I actually dont like about my XY8. But all in all it is great and especially great under the control of the hoverfly pro!

 

[redridinghood]

RRH, you doing that in the custom mixer of the WKM?

I would have thought that would have been pre programmed in the mixer selection when you choose Y6 / X8..

I run the same top and bottom and found this the best in the real world of battery use and performance.

Dave

On some test flights I made when I had my CC esc logging I found that I needed to custom mix in order for the lower motors to spin faster. Maybe DJI' mix is pushing the same power all around. 15% was enough on my 14X4 to get even work out of my motors.
BTW I really like how my SJ X8 flies. I will never go back to flat 8.

 

[Dbasileccim]

I do wonder though, if the weight of 4 extra carbon fiber booms is even noticeable to the heli. I know there are mounts as well but all in all this would seem to be a very minor weight addition. it's really for the smaller size more than anything. personally I want my heli to be as large as possible in the air, the one thing I actually dont like about my XY8. But all in all it is great and especially great under the control of the hoverfly pro!

The smaller size for shipping was my main reason for looking at an x8 instead of continuing with my flat octo. Iris quote about wanting it as large as possible in the air is obvious but not thought about before the build was complete.

 

[Dbasileccim]

Thanks for everyone's advice. The x8 is flying very nice in comparison to either my quad or flat octo. Don't knowif it is the new firmware (been since April 2012 since I upgraded last) or better build skills, or luck.

Btw, I am flying with 12x3.8 apc and it is working fairly well. I will mess with prop size and pitch next.