F-35B Lightning II VTOL - Scale composite build!!! - Page 3

bwalt822 · Aug 18, 2009, 04:48 PM

Although the main risk I see to this project is if the response time of the motors is too slow. In other words, the gyros should be able to detect any uncommanded change in attitude fast enough but the ESC/Motor/Propellor system may not be able to spool up or slow down fast enough.

cray2602 · Aug 18, 2009, 04:59 PM

The problems ive always experienced is that the response from the EDF is usually too abrupt and it over corrects and ends up in an oscilation. No amount of tweaking and EXPO could stop it. But that is with the cheapo GWS mixers, from the roll control video posted id say thats not a problem with their build. Looks rock solid so far.

capt · Aug 18, 2009, 08:25 PM

See post #13 in this thread for a link to a 4 EDF VTOL that flew incredibly well! Proof that it can be done, this one should fly as well if it is light enough.

bwalt822 · Aug 18, 2009, 10:08 PM

Quote:

Originally Posted by capt

See post #13 in this thread for a link to a 4 EDF VTOL that flew incredibly well! Proof that it can be done, this one should fly as well if it is light enough.

That plane did not look capable of conventional flight and was mostly symmetric which helps things out a little.

The only VTOL that I have seen that was capable of transition looked like a modified Cessna 182 and the plane hung far below the two props giving it more stability.

Brandano · Aug 19, 2009, 07:19 AM

Again and again... the pendulum effect is an illusion, the vectors of thrust tilt with the plane. Putting the rotors away from the CG only help with control authority. And even then only if you put the tilt point away from the CG

vertigo-rc · Aug 19, 2009, 08:34 AM

G-force237 how did you come up with the 3d model outline? Did you find a drawing with fuselage cross sections that the rest of us can't seem to find??!! I am working on my own version of the F-35B, but can't find any drawings except for 3 views and model renderings.

jimbob00 · Aug 19, 2009, 09:30 AM

if multi edf is a problem, one could direct the airflow from one big edf to the sides as well with small traps that u can open/close

)

adavis · Aug 19, 2009, 01:05 PM

Quote:

Originally Posted by bwalt822

That plane did not look capable of conventional flight and was mostly symmetric which helps things out a little.

The only VTOL that I have seen that was capable of transition looked like a modified Cessna 182 and the plane hung far below the two props giving it more stability.

Have you seen this? http://verti4.blogspot.com/

Checkout the video.

Best Regards,
=Adrian=

bwalt822 · Aug 19, 2009, 02:19 PM

Quote:

Originally Posted by Brandano

Again and again... the pendulum effect is an illusion, the vectors of thrust tilt with the plane. Putting the rotors away from the CG only help with control authority. And even then only if you put the tilt point away from the CG

now that i think about that, you are right.

bigwood212 · Aug 19, 2009, 03:57 PM

This guy did it. Theres also a vid of him flying it outside where he transitions into foward flight... I cant find it though.

rc edf vtol (1 min 25 sec)

Sky-walker · Aug 20, 2009, 03:40 PM

rc edf vtol (0 min 33 sec)

matthew73 · Aug 21, 2009, 04:38 AM

Great work GFORCE, i look forward to following your ambitios project.

Keep up the good work and good luck.

vertigo-rc · Aug 21, 2009, 07:27 PM

I noticed this when planning my own F-35. When calculating the CG of the aircraft (assuming placing the CG at 25% MAC) I noticed that the distance from the CG to the lift fan and to the 3 bearing nozzle at the rear when in hover mode is the same (as expected), but it seems that the roll nozzles are not located on the CG but are somewhat aft. Does anyone know why this is? I realize that on the real F-35 the CG wouldn't be placed at 25%...there would definitely be a lot less static margin in order to increase maneuverability, but I don't see how the CG could be in line with the roll posts? To make a perfectly scale F-35B you would have to cope with the pitch coupling caused by having the roll posts aft of the CG. Anyone have any theories?

vertigo-rc · Aug 21, 2009, 07:36 PM

I somewhat just answered my own question just as I posted the previous message!! It seems I was assuming that the F-35B was a flying wing! I neglected to take the tail surface area into account, which has it's own aerodynamic center which will shift the neutral point of the whole aircraft (and thus the allowable CG position) rearwards!!! I wonder where those roll posts lie with respect to the CG now????

By the way...very nice job so far! Can't wait to see you hover and then finally transition this machine("fingers crossed")!!

jeeeeeeright · Aug 22, 2009, 07:12 AM

This is sweet!
Looking forward to see the plane competed (soon?)!

Aug 19, 2009, 08:34 AM	#36
vertigo-rc Registered User Join Date: May 2007 Posts: 12	Nice modelling! G-force237 how did you come up with the 3d model outline? Did you find a drawing with fuselage cross sections that the rest of us can't seem to find??!! I am working on my own version of the F-35B, but can't find any drawings except for 3 views and model renderings.

Aug 21, 2009, 04:38 AM	#42
matthew73 Registered User Join Date: Oct 2008 Location: Melbourne, Australia Posts: 26	Great thread Great work GFORCE, i look forward to following your ambitios project. Keep up the good work and good luck.

Aug 21, 2009, 07:27 PM	#43
vertigo-rc Registered User Join Date: May 2007 Posts: 12	Roll Posts not on CG I noticed this when planning my own F-35. When calculating the CG of the aircraft (assuming placing the CG at 25% MAC) I noticed that the distance from the CG to the lift fan and to the 3 bearing nozzle at the rear when in hover mode is the same (as expected), but it seems that the roll nozzles are not located on the CG but are somewhat aft. Does anyone know why this is? I realize that on the real F-35 the CG wouldn't be placed at 25%...there would definitely be a lot less static margin in order to increase maneuverability, but I don't see how the CG could be in line with the roll posts? To make a perfectly scale F-35B you would have to cope with the pitch coupling caused by having the roll posts aft of the CG. Anyone have any theories? Attached Thumbnails Roll Post Location???? 45.9 KB · Views: 373

Aug 21, 2009, 07:36 PM	#44
vertigo-rc Registered User Join Date: May 2007 Posts: 12	Oops I somewhat just answered my own question just as I posted the previous message!! It seems I was assuming that the F-35B was a flying wing! I neglected to take the tail surface area into account, which has it's own aerodynamic center which will shift the neutral point of the whole aircraft (and thus the allowable CG position) rearwards!!! I wonder where those roll posts lie with respect to the CG now???? By the way...very nice job so far! Can't wait to see you hover and then finally transition this machine("fingers crossed")!!

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Aug 18, 2009, 04:48 PM	#31
bwalt822 Registered User Join Date: Aug 2008 Location: The Puget Sound Area Posts: 1,603	Although the main risk I see to this project is if the response time of the motors is too slow. In other words, the gyros should be able to detect any uncommanded change in attitude fast enough but the ESC/Motor/Propellor system may not be able to spool up or slow down fast enough.

Aug 18, 2009, 04:59 PM	#32
cray2602 I ABUSE LIPO'S Join Date: Jan 2008 Location: Plain ole KS Posts: 1,352	The problems ive always experienced is that the response from the EDF is usually too abrupt and it over corrects and ends up in an oscilation. No amount of tweaking and EXPO could stop it. But that is with the cheapo GWS mixers, from the roll control video posted id say thats not a problem with their build. Looks rock solid so far.

Aug 18, 2009, 08:25 PM	#33
capt Registered User Join Date: Sep 2007 Location: Nevada, USA Posts: 698	See post #13 in this thread for a link to a 4 EDF VTOL that flew incredibly well! Proof that it can be done, this one should fly as well if it is light enough.

Aug 19, 2009, 07:19 AM	#35
Brandano Registered User Join Date: Oct 2004 Posts: 1,382	Again and again... the pendulum effect is an illusion, the vectors of thrust tilt with the plane. Putting the rotors away from the CG only help with control authority. And even then only if you put the tilt point away from the CG

Aug 19, 2009, 09:30 AM	#37
jimbob00 Registered User Join Date: Aug 2009 Location: germany Posts: 427	if multi edf is a problem, one could direct the airflow from one big edf to the sides as well with small traps that u can open/close )

Aug 22, 2009, 07:12 AM	#45
jeeeeeeright Seaplane submariner Join Date: Sep 2007 Location: Norway Posts: 77	This is sweet! Looking forward to see the plane competed (soon?)!