10/23 Raptor Video

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Kyle Boatright

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Revised Belt Tensioner Design !!!! Is it me or does the 'new' design tensioner just squeeze the belt against the pulley ??? rather than be placed 'mid-span' from drive pulley to PRU pulley and provide a proper belt-tension element ?
I watched the latest video last night while multitasking. If the tensioner works that way, well, bless his heart. I didn't notice.
 

mcrae0104

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Revised Belt Tensioner Design !!!! Is it me or does the 'new' design tensioner just squeeze the belt against the pulley ??? rather than be placed 'mid-span' from drive pulley to PRU pulley and provide a proper belt-tension element ?
No, it doesn't just squeeze against the pulley. If you look closely, you can see the belt's teeth disengaging from the pulley above the tensioner. It appears that it's mounted as low as possible without interference from some motor mount tubing.
 

BBerson

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It looked rock steady in that video. So nothing has changed other than no turbulence or possible pilot technique improvement. (using rudder with stick or something)
 

flywheel1935

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No, it doesn't just squeeze against the pulley. If you look closely, you can see the belt's teeth disengaging from the pulley above the tensioner. It appears that it's mounted as low as possible without interference from some motor mount tubing.
Um,I hear what your saying, but the tension roller still looks like it too close to the PRU pulleys, maybe reducing the rollers diameter would allow better tension !!!, but guess P is fine with that ?
 

Wild Bill

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I thought the same thing about the tensioner. It may be tensioning “properly” but it just looks like it should be closer to the middle of the straight section of belt.

On the subject of stability PIO, etc..
It’s looking much smoother with every flight.
Something I don’t have a clear understanding of is how the rudders work. Seems like I remember that they were designed to deflect in both directions. I missed the videos on that somehow.
If they do go both ways and the rudder pedal are sensitive, this would explain part of it.
Most canard rudder systems that I know of only go outward. With your feet off the pedals both rudders return to a neutral position that never changes.
Even 1/16” of movement at trailing edge of the rudder equals significant roll response.
It’s not like most airplanes where you can mishandle the rudder and get away with it.
I’ve tried to think about how dual direction rudders would feel in a canard. Seems like it could be tricky especially if they are sensitive.
 

wsimpso1

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I was watching for the roll-pitch interaction, and it does seem to be getting smaller, as if it is pilot induced and the pilot is improving on that count.

As far as the rudders go, the tip sails of Long-EZ and derivatives are wing extensions in that they are lifting foil shaped, and low pressures from the top of the wing wrap onto the sails. Even the lower extensions are foil shaped with lift towards centerline. Normally, these rudders are like flaps - they can be deflected out (down) but not in (up). They hit stops like a flap and are spring loaded to stay on the stops, with each one actuated by its own pedals. Well worked out system...

Does anybody KNOW how the rudders are rigged? Anything but Long-EZ replication will have all sorts of tails that might make for interesting interactions.

Billski
 

BBerson

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In post 865 Jeff talks about "canting the verticals to counter roll/yaw coupling".
Beyond my understanding, but might be adjustments PM can make if needed.
 

rbarnes

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If the rolling motion was/is turbulence induced, what does it say about stability in some real moderate "I wish I'd stayed home" turbulence ?
 

BBerson

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If the airplane doesn't have the stability you like then get another airplane. It's a choice. Some pilots prefer near neutral stability. The Wright's accepted negative stability until the B model Flyer.
 

Rik-

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Just watching the latest video and one thing I’ve noticed in every flight that Peter has retraced the gear is that his gear door on the main gear appears to be open at the leading edge scooping in air.

What kind of drag would this present?

Must say, it seems very stable in flight now
 

Marc Zeitlin

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Does anybody KNOW how the rudders are rigged? Anything but Long-EZ replication will have all sorts of tails that might make for interesting interactions.
IIRC, they work exactly like other canard rudders - they deflect outward only. There's only a single cable running out to the winglet, and then a wonky mechanism with a small belcrank up in there to push the rudder out. So in that sense, they're no different than LE/COZY/etc. rudders.

Now in Raptor, for reasons associated with the nosewheel steering (NOT castoring nose gear, like in other canards), the rudder pedals needed to be coupled so that you could push one and the other would return. So there's a lost motion mechanism that couples the pedals to the rudder cables so that a rudder is only deflected if THAT pedal is pushed forward, and there's no deflection if the rudder pedal is aft of neutral.

With respect to rudders on these planes deflecting in both directions, there's a good reason not to do that and a reason that most people THINK is the reason they don't do that, but isn't.

Firstly, if you want to have each rudder move in both directions, the cabling becomes far more complex - you need to link the rudders together with a cable, as PM has done with the ailerons. It's WAY easier to have one cable to pull the rudder out, and a spring (and air loads) to push it back in against a hard stop. So, cheaper and easier.

Secondly, people think (wrongly - and this includes a LOT of canard pilots) that the rudders work because they cause drag on the winglet which yaws the plane in the direction of the deflected rudder. While the rudders DO cause drag, they are also causing a lot MORE lift inboard, and since they're aft of the CG, THAT is the main cause of the yawing moment - in fact, the lift inboard is on the order of 10X the force of the drag aftwards. So people think that if the rudder deflected in both directions, that the outward deflecting rudder would be counteracted by the inward deflecting rudder. This is incorrect, as the inward deflecting rudder would still produce ~80% of the yawing moment of the outward deflecting rudder (outward is 110% of the lift moment, while inward is 90% of the lift moment). So the two rudders would provide ~1.8X the force of a single rudder.

Now, there's also the issue of rudder flutter when deflecting inboard with a soft "hard stop" - a number of folks (including me) have had that happen. I do NOT know what the effect of an inward deflecting rudder would be with a very stiff control system (interconnect cable). My guess is that if the system was stiff enough, it would work fine, but refer back to "Firstly" for why we don't do that.
 

BBerson

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A small hydraulic shock damper might prevent that soft inward deflecting rudder from flutter.
I installed a shock damper on the Grob rudder in accordance with the Airworthiness Directive after a rudder flutter case.
 

Marc Zeitlin

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Marc Z, just re-watched, "Did we fix the shimmy" from a year ago, cant see any connection from rudder pedals to the nosewheel ??? Thought steering was by Diff Braking, which is why the Raptor was eating discs and pads ????
So it's very possible that this past year has driven me either completely insane or senile (or both), but I certainly thought that the Raptor has nosewheel steering. This video of the DESIGN, granted from about 6 million years ago, indicates a nosewheel steering system:


but it could have been OBE, and given that I see about 40 different "N" numbers/year, I could easily be confused about what I saw in GA about a year ago, as I can't find any specific reference to nosewheel steering.

A comment from the video you pointed to:


does reference differential braking steering, however, but who knows how accurate comments on YT are... In this case, they may be right and I may be completely mistaken, and merely remembering the first video I point to above.

Now, if you're right, then the coupling of the rudder pedals would just be "so that it's like other planes that folks are used to" - there are a few Velocities that are set up like that, because why not? It's just extra weight and complexity, so that we can use toe brakes.

@canardlover - Jeff - can you confirm or deny my sanity here? Happy to retract the claim if I'm full of BS.
 

Joe Blough

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How about a 2L turbo diesel for something like a Kitfox? Trying to go cheap on a power plant is probably not a good idea. Those 912 is Rotax are sure light...
 

wsimpso1

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How about a 2L turbo diesel for something like a Kitfox? Trying to go cheap on a power plant is probably not a good idea. Those 912 is Rotax are sure light...
Check out these threads and go from there.
 

canardlover

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So it's very possible that this past year has driven me either completely insane or senile (or both), but I certainly thought that the Raptor has nosewheel steering. This video of the DESIGN, granted from about 6 million years ago, indicates a nosewheel steering system:


but it could have been OBE, and given that I see about 40 different "N" numbers/year, I could easily be confused about what I saw in GA about a year ago, as I can't find any specific reference to nosewheel steering.

A comment from the video you pointed to:


does reference differential braking steering, however, but who knows how accurate comments on YT are... In this case, they may be right and I may be completely mistaken, and merely remembering the first video I point to above.

Now, if you're right, then the coupling of the rudder pedals would just be "so that it's like other planes that folks are used to" - there are a few Velocities that are set up like that, because why not? It's just extra weight and complexity, so that we can use toe brakes.

@canardlover - Jeff - can you confirm or deny my sanity here? Happy to retract the claim if I'm full of BS.
Marc,indeed it was supposed to have a steerable nosewheel.. He ,however, in the interest of expediting completion purchased a used Lancair IV nose gear leg and went with differential braking instead. Last I knew steerable nose wheel was still to be incorporated in any production effort.
 
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