Upsss ..... we do it again .....
03-16-2010, 02:40 PM
#26
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RE: Upsss ..... we do it again .....
ORIGINAL: shockwave
Good Luck on the YF-23 Project; it is an Amazing aircraft! You will find it a bit challenging to get the CG right; about 60% of the structure will be aft of the CG which created problems the 65 inch Nitro/EDF and 100 inch Twin Turbine versions of the aircraft I have worked on. You will find that the design is bi-stable and will want to pitch up abruptly especially during landings.
I look forward to seeing a 1/7 version of this bird take to the sky's.
Take it easy.
David.
Good Luck on the YF-23 Project; it is an Amazing aircraft! You will find it a bit challenging to get the CG right; about 60% of the structure will be aft of the CG which created problems the 65 inch Nitro/EDF and 100 inch Twin Turbine versions of the aircraft I have worked on. You will find that the design is bi-stable and will want to pitch up abruptly especially during landings.
I look forward to seeing a 1/7 version of this bird take to the sky's.
Take it easy.
David.
gave it some thought.
Piching up in slow flight (high alpha) shows that the pressure point of the total aircraft is moving in front of the preset cg. In other words the tail fuse surface stalls- the Vtail is still flying- producing still the nec downforce for stable flight, unfortunately now to the wrong stability point.
Or:
Thrust angle did not fit slow flight-
If I get it right it is too much negative angle (aft pointing downwards)
Flying fast and furios with a lot of engine power, the vtail will compensate (showing adequate stability) by more longitudinal dihedral but slow flight (no engine power) will be a very bumpy ride.
Will check on the pressure point in y (height) direction.
Please feel free to prove me wrong- I am learning every day.
b.r.
Wolfgang
03-17-2010, 03:02 AM
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RE: Upsss ..... we do it again .....
Hello Wolfgang,
Sounds like you are on the right path for working out the stability issues with the 23.
Here is a link to some my experiences with the YF23 project; others have also responded with their experiences.
[link=http://www.rcgroups.com/forums/showthread.php?t=556618]YF23 PAV3[/link]
I am still working on the 100 inch version but not as much as I would like.
Take Care
David.
Sounds like you are on the right path for working out the stability issues with the 23.
Here is a link to some my experiences with the YF23 project; others have also responded with their experiences.
[link=http://www.rcgroups.com/forums/showthread.php?t=556618]YF23 PAV3[/link]
I am still working on the 100 inch version but not as much as I would like.
Take Care
David.
03-17-2010, 03:36 AM
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RE: Upsss ..... we do it again .....
High David,
Txs for posting, congrats to your nice YF23.
Have watched your vid and it seems to prove my theory with thrust angle.
It will not loose the tail surface aerodynamical, but in my opinon the cg is a little to far aft. Havent seen the channels aft for the airflow of the impellers, but I think, they are guiding the air in that way to put pressure on the nose.- which saved your day on the first unintended flight anyway.
When you realised that you have the unintended pitching up moment, was the impeller at dead stop?
b.r.
Wolfgang
Txs for posting, congrats to your nice YF23.
Have watched your vid and it seems to prove my theory with thrust angle.
It will not loose the tail surface aerodynamical, but in my opinon the cg is a little to far aft. Havent seen the channels aft for the airflow of the impellers, but I think, they are guiding the air in that way to put pressure on the nose.- which saved your day on the first unintended flight anyway.
When you realised that you have the unintended pitching up moment, was the impeller at dead stop?
b.r.
Wolfgang
04-05-2010, 07:52 AM
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RE: Upsss ..... we do it again .....
Hello,
I noted with interest that you are working on a model of the YF-23. Gorgeous plane. Would you consider selling me a copy of the 3D CAD files you developed as I am interested in designing and building one and I was hoping to avoid reverse engineering the thing from scratch.
I hope to hear from you soon.
SDA
