F-35B Lightning II VTOL - Scale composite build!!! - Page 5

custom t · Oct 21, 2009, 08:39 PM

sweet

RC Ryan · Nov 07, 2009, 02:31 PM

Cool

what CAD program are you using?

RCvertt · Nov 07, 2009, 03:54 PM

Quote:

Originally Posted by Angry_Monk

Im pretty sure this is so cool that its actually illegal....

I heard the real one got canceled because this RC version turned out better

Peter W · Nov 11, 2009, 08:47 PM

This is the best VTOL jet project bar none, really hope you keep at it, the build quality and philosophy is brilliant and inspirational to me

jimbob00 · Nov 16, 2009, 11:16 AM

this project seems unfortunately dead =(

Peter W · Nov 16, 2009, 12:10 PM

they can't give up on it, they've invested hundreds possibly thousands of dollars on this concept as well as tens of man hours.
PLUS I wanna see it in a stable hover sooo bad

bwalt822 · Nov 16, 2009, 03:59 PM

An earlier post said they would pick it back up over winter break which should be in about a month. This looks really cool but personally I'm not holding my breath for a stable hover because everything is coupled together, possibly more than what off the shelf gyros can compensate for.

Peter W · Nov 16, 2009, 06:12 PM

it HAS to work cos I want it too
just add gyros to gyros on top of gyros its gotta work!

ben1101 · Nov 17, 2009, 01:06 AM

Quote:

Originally Posted by bwalt822

An earlier post said they would pick it back up over winter break which should be in about a month. This looks really cool but personally I'm not holding my breath for a stable hover because everything is coupled together, possibly more than what off the shelf gyros can compensate for.

Maybe if each center of axis was pinpointed with a gyro placed there they can get away with the cross coupling...

Besides as Peter said, it HAS to work because I want it to!

EDIT: Its all speculation on speculation anyhow - we just gotta wait I guess....

RCvertt · Nov 17, 2009, 01:22 AM

Quote:

Originally Posted by Peter W

it HAS to work cos I want it too
just add gyros to gyros on top of gyros its gotta work!

And if it doesn't, add one more gyro

Quote:

Originally Posted by ben1101

...they can get away with the cross coupling...

What is being refered to when "cross coupling" is mentioned? Are we refering to force being unintentionally transferred to something else such as yaw affecting pitch as well or am I missing something here?

Quote:

Originally Posted by bwalt822

exactly, you can actually get coupling in all three axes...

Great. Thanks for the informative explaination as well. Once that thing leaves the ground it's difficult for one force not to affect multiple axes like you said. Throw in some wind and all I can say is that I'm glad I'm leaving it up to others to do most of the programming.

bwalt822 · Nov 17, 2009, 07:28 PM

exactly, you can actually get coupling in all three axes. Lets say you go to roll...

One of the puffers will spool up and the other will coast down. The one that spools up will accelerate faster than the one that coasts down which will impart a yaw. Also since the puffer fans are behind the CG then this asymmetric spooling will cause a pitch change.

Now lets talk about what the gyros do...

The yaw gyro senses a change in yaw and tries to correct by moving the rear main fan. This can cause a slight change in lift in the back fan resulting in a pitch change.

The pitch gyro should only control the front fan and when it spools up or coasts down to compensate for the pitch changes it causes a yaw change because the fans angular momentum changes.

Also what happens if a fan needs to spool down faster than what is possible to compensate.

Basically the gains on all gyros need to be set correctly so that they do not create a runaway feedback loop that causes instability. Even then the physical limitations of the equipment may not be able to stop it from being unstable.

Peter W · Nov 18, 2009, 01:23 PM

good info from bwalt thanks, so this is why vtol is soo damn hard hehe

NuttyPro67 · Nov 22, 2009, 01:34 PM

Ok, so once these guys solve that problem they run into a new one! He said in the first post that his finished project weight is estimated to be around 75 oz! Thats 4.5 pounds guys! Based off of my F-35 CAD models, they MIGHT have 2 sq ft TOTAL of wing area on that plane. (My calculations actually favor in the 1.5 sq ft direction).

This leaves the model with a wing loading of about 35 oz/sq ft, and thats estimating in their favor! Thats about the same wing loading of a turbine model, the stall speed on this model is going to be insane!

Good Luck fellas.

Peter W · Nov 22, 2009, 03:27 PM

heavy vtol eh?
what fan are they using?
wonder if the 12 blade 120mm unit from schubeler would be good, it certainly sounds amaaaazing in videos so far

Brandano · Nov 22, 2009, 04:46 PM

actually, a high stall speed will probably help with the conversion, as the wing lift will stop interfering with the direct thrust from the lift fans. However it will make conventional landings hairy to say the least. the NAVY CTOL version has an enlarged wing on the full size one

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Oct 21, 2009, 08:39 PM	#61
custom t Registered User Join Date: Oct 2009 Posts: 4	sweet

Nov 07, 2009, 02:31 PM	#62
RC Ryan Registered User Join Date: Oct 2009 Posts: 16	Cool what CAD program are you using?

Nov 11, 2009, 08:47 PM	#64
Peter W Registered User Join Date: Jul 2001 Location: London Posts: 1,010	This is the best VTOL jet project bar none, really hope you keep at it, the build quality and philosophy is brilliant and inspirational to me

Nov 16, 2009, 11:16 AM	#65
jimbob00 Registered User Join Date: Aug 2009 Location: germany Posts: 435	this project seems unfortunately dead =(

Nov 16, 2009, 12:10 PM	#66
Peter W Registered User Join Date: Jul 2001 Location: London Posts: 1,010	they can't give up on it, they've invested hundreds possibly thousands of dollars on this concept as well as tens of man hours. PLUS I wanna see it in a stable hover sooo bad

Nov 16, 2009, 03:59 PM	#67
bwalt822 Registered User Join Date: Aug 2008 Location: The Puget Sound Area Posts: 1,617	An earlier post said they would pick it back up over winter break which should be in about a month. This looks really cool but personally I'm not holding my breath for a stable hover because everything is coupled together, possibly more than what off the shelf gyros can compensate for.

Nov 16, 2009, 06:12 PM	#68
Peter W Registered User Join Date: Jul 2001 Location: London Posts: 1,010	it HAS to work cos I want it too just add gyros to gyros on top of gyros its gotta work!

Nov 17, 2009, 07:28 PM	#71
bwalt822 Registered User Join Date: Aug 2008 Location: The Puget Sound Area Posts: 1,617	exactly, you can actually get coupling in all three axes. Lets say you go to roll... One of the puffers will spool up and the other will coast down. The one that spools up will accelerate faster than the one that coasts down which will impart a yaw. Also since the puffer fans are behind the CG then this asymmetric spooling will cause a pitch change. Now lets talk about what the gyros do... The yaw gyro senses a change in yaw and tries to correct by moving the rear main fan. This can cause a slight change in lift in the back fan resulting in a pitch change. The pitch gyro should only control the front fan and when it spools up or coasts down to compensate for the pitch changes it causes a yaw change because the fans angular momentum changes. Also what happens if a fan needs to spool down faster than what is possible to compensate. Basically the gains on all gyros need to be set correctly so that they do not create a runaway feedback loop that causes instability. Even then the physical limitations of the equipment may not be able to stop it from being unstable.

Nov 18, 2009, 01:23 PM	#72
Peter W Registered User Join Date: Jul 2001 Location: London Posts: 1,010	good info from bwalt thanks, so this is why vtol is soo damn hard hehe

Nov 22, 2009, 01:34 PM	#73
NuttyPro67 Cant you feel the freedom Join Date: Jan 2007 Location: Lakeland, FL Posts: 324	Ok, so once these guys solve that problem they run into a new one! He said in the first post that his finished project weight is estimated to be around 75 oz! Thats 4.5 pounds guys! Based off of my F-35 CAD models, they MIGHT have 2 sq ft TOTAL of wing area on that plane. (My calculations actually favor in the 1.5 sq ft direction). This leaves the model with a wing loading of about 35 oz/sq ft, and thats estimating in their favor! Thats about the same wing loading of a turbine model, the stall speed on this model is going to be insane! Good Luck fellas.

Nov 22, 2009, 03:27 PM	#74
Peter W Registered User Join Date: Jul 2001 Location: London Posts: 1,010	heavy vtol eh? what fan are they using? wonder if the 12 blade 120mm unit from schubeler would be good, it certainly sounds amaaaazing in videos so far

Nov 22, 2009, 04:46 PM	#75
Brandano Registered User Join Date: Oct 2004 Posts: 1,385	actually, a high stall speed will probably help with the conversion, as the wing lift will stop interfering with the direct thrust from the lift fans. However it will make conventional landings hairy to say the least. the NAVY CTOL version has an enlarged wing on the full size one