Panther Trainer Autogyro

[Andy J]

Quick check on one blade and found it about 1mm forward of the correct position,  which means each blade will be TE heavy.

[Richard Harris]

Andy,

 

Essentially a rotor blade is a wing, if your mounting point is forward of the cordwise CG it can make it pitch sensitive as with a tail heavy fixed wing. This can cause tracking issues with the blades as can differing length way CG positions, this can also create vibrations throughout the head and control system.

Without looking at the plan I am pretty sure I would have set the mounting hole back from the CG to compensate for covering etc, its something I've done for many years.

To bring the CG back in line you could always add weight  forward of the mounting hole centre (tape may work) around the cordwise CG position?

 

Rich

[Andy J]

Now that the wind strength has increased managed to test the auto rotation of the blades up to just below flight speed. Blades spun up ok but have a slight wobble on the head so obviously I need to do some further balancing before I attempt a flight.

 

Would also appreciate some advice on how to check the CoG position. Understand you hang the model from the rotor head without the blades but what angle of dangle is required?

 

Plaster of paris canopy plug is also coming along but needs further work to get a reasonably smooth shape before I try out my new vacuum table set-up.

[bees]

I also need some advice regarding CG, hang angle. I have drilled a hole through the mast at the recommended CG and have inserted some string to hang the Panther, is this the correct method. At the moment the Panther is tail heavy at the moment.

[Richard Harris]

18 hours ago, bees said:

I also need some advice regarding CG, hang angle. I have drilled a hole through the mast at the recommended CG and have inserted some string to hang the Panther, is this the correct method. At the moment the Panther is tail heavy at the moment.

 

Bees,

 

Yes, that is the correct method, it should balance horizontal or slightly nose down using the tail plane as your horizontal datum. It's worth remembering that the model should be ready to fly with the Lipo and blades installed when doing this.

 

Rich

[Mike T]

Question for @Richard Harrisif I may?  I've enlarged my Panther plan by a modest 15% to make it easier for the fus. to take a .52 FS plus associated tankage.  The structure will be as per original (no increase in section dimensions etc.) apart from subbing 1/8 birch ply for some sheet parts at the front for engine and u/c mounting.

 

The question is, do I need to increase the blade chord or thickness, or can I get away with the original plan dimensions, albeit 10-15% longer?

[Richard Harris]

On 17/06/2022 at 14:39, Mike T said:

Question for @Richard Harrisif I may?  I've enlarged my Panther plan by a modest 15% to make it easier for the fus. to take a .52 FS plus associated tankage.  The structure will be as per original (no increase in section dimensions etc.) apart from subbing 1/8 birch ply for some sheet parts at the front for engine and u/c mounting.

 

The question is, do I need to increase the blade chord or thickness, or can I get away with the original plan dimensions, albeit 10-15% longer?

Mike,

You should be fine

 

Rich

[Mike T]

Thanks, Rich - good to know! ?

[riktor]

Hello!

 

A bit late to the party.

I bought an used fuselage on bmfa page, built the head using 3d print and Heli bearings, build the triangle using laminated fibreglass, carbon fibre and beechwood, built the blades as per pictures, and put it in flight.

 

It is sort of ok but it looks a bit unstable on roll and pitch. Look like the CG is way back but I don't have the original plan to check. Also mine has the tendency to tilt hard just after take off plus same when it get a bit of speed. What I did wrong ?

 

Edited January 30, 2023 by riktor

[Richard Harris]

Riktor,

 

Nice Panther and flight.

 

The left roll you are experiencing just before lift off is simply not enough rotor speed, its worth pulling back on the rotors whilst taxiing slowly to get them spinning well. 

Regarding the left roll as your air speed increases, are you inputting down to compensate an upward pitch? the reason I ask this is its a sign of the rotor disc coming out of autorotation (inducing a left roll).

What I would be doing is adding a bit of nose weight, this will force you to add a click or two of rearward tilt.

Try reducing your throws on roll and pitch, if it still feels sensitive add a little tip weight to each blade (say 3-5g) and see how it goes.

 

Rich

[riktor]

17 minutes ago, Richard Harris said:

Riktor,

 

Nice Panther and flight.

 

The left roll you are experiencing just before lift off is simply not enough rotor speed, its worth pulling back on the rotors whilst taxiing slowly to get them spinning well. 

Regarding the left roll as your air speed increases, are you inputting down to compensate an upward pitch? the reason I ask this is its a sign of the rotor disc coming out of autorotation (inducing a left roll).

What I would be doing is adding a bit of nose weight, this will force you to add a click or two of rearward tilt.

Try reducing your throws on roll and pitch, if it still feels sensitive add a little tip weight to each blade (say 3-5g) and see how it goes.

 

Rich

Hi Rich,

 

Thanks for your reply. Despite the video, the tilt is usually in pitch.

 

So after the manual spinning, I keep the rotor pitch up while accelerating. Then I release it and continue the take off run until it take off almost by itself or with a very gentle pitch up ( like a normal plane) but every time the panther has a strong pitch up attitude that I have to balance by pitching down.

 

Then once in stable flight, I can't go faster as it generate an higher rotor speed that will generate a pitch up motion again.

 

About the roll: I'm not sure if it should behave like this ( not gently self centring) or it is normal Thant I have to manually compensate with opposite direction to keep a constant roll turn. It is like having a plane with negative dihedral.

 

Just to better understand. Where should be the CG of the panther?

[riktor]

Today I crashed due to too strong wind while turning downwind. My bad.

 

All fixable but.. where can I find a new canopy?

[Richard Harris]

Riktor,

 

Easily done. The prototypes canopy was a pop bottle shrunk over a balsa mould which doesn't take to much effort to produce. There have been many open cockpit versions made over the years which look OK.

 

Rich

[riktor]

3 hours ago, Richard Harris said:

Riktor,

 

Easily done. The prototypes canopy was a pop bottle shrunk over a balsa mould which doesn't take to much effort to produce. There have been many open cockpit versions made over the years which look OK.

 

Rich

I was hopping for a more lazy solution:) like 5£ to someone:)

By the way with more forward CG and balanced propeller was flying amazing! I repaired almost everything. I need some covering film and back in the sky

[Richard Harris]

Riktor,

 

I think my Panther canopy plug has long gone as its been 12 years, I know Steve Jones 2 has made some for others, maybe worth sending him a PM.

Good to hear its flying well with the extra nose weight, look forward to a flight video 😀

 

Rich

[riktor]

@Richard Harris  so after quite a while I manage to have the panther back in flight with a more forward GC, better balanced blade and a decent 4s battery.

 

I need to understand now if the flight experience I had is normal or I still need to adjust something.

 

The model doesn't feel stable, it is actually the same feeling of flying a flybar helicopter. I always have to correct it to keep it level or at a bank angle during turns.

same for heading. one moment is was yawing left, one moment right depending from wind direction.

 

Also never stable for pitch. Pitch correction was very much based on speed. So in summary the panther feels quite like an unstable plane with negative dihedral and very much wrong motor angle.

 

Any feedback about? I almost feel the need of a gyros to make it stable.

[Trevor]

When properly set up, the Panther is very stable - Richard did design it as a trainer after all! I’m no expert but maybe your cg is still not right or perhaps you are flying too fast. Are your head servos and linkages strong enough? No doubt Richard will respond too but a video would be a big help in understanding what’s going on.

[riktor]

1 hour ago, Trevor said:

When properly set up, the Panther is very stable - Richard did design it as a trainer after all! I’m no expert but maybe your cg is still not right or perhaps you are flying too fast. Are your head servos and linkages strong enough? No doubt Richard will respond too but a video would be a big help in understanding what’s going on.

Will try to make a video in the following days. 6kg digital hitec servos with very strong linkage. Bec is super stable at 6v.

[Richard Harris]

Riktor,

 

If you have it set up as suggested it could possibly be light blades, a video would help.

 

.Rich

[riktor]

On 14/04/2023 at 15:39, Richard Harris said:

Riktor,

 

If you have it set up as suggested it could possibly be light blades, a video would help.

 

.Rich

Hi Rich,

As I bought the fuselage off bmfa classifieds I never bought the original plan and article. Can you advise what I should do?

[riktor]

@Richard Harris  today I finally managed to fly again and record a video. Please can you provide your feedback?https://youtu.be/wPFNv8XnZMU

[Richard Harris]

Riktor,

 

It doesnt look too bad if Im honest, Im not on the sticks though. However, there are what looks like a few things that could be going on.

Do you have right thrust on your motor? if you have I would reduce it as there seems to be a yawing moment to the right with power that you are trying to compensate with left roll. This  can give that tipping over effect. If not I would try trimming a touch of left rudder and check the servo is centering with no slop in the rudder linkages etc.

There is also the possibility that you haven't got enough nose weight as it seems to pich up and down?

Your rearward tilt might be very close to being in autorotation which could cause this effect, if you add nose weight (or extra negative shims) this will force you to trim back the rotor disc for neutral flight giving the blades a more constant airflow through them.

Easiest way to check CG is to take it up high and turn off motor, if correct it should drop its nose and descend forwards slightly.

If its incorrect it will stop, hang its tail and do a pirouette, repeating as it tries to weather cock back into wind.

Whilst testing this do not touch the pitch, just leave it in its neutral position.

 

Let me know what you find?

 

Rich

Edited May 8, 2023 by Richard Harris

[riktor]

18 hours ago, Richard Harris said:

Riktor,

 

It doesnt look too bad if Im honest, Im not on the sticks though. However, there are what looks like a few things that could be going on.

Do you have right thrust on your motor? if you have I would reduce it as there seems to be a yawing moment to the right with power that you are trying to compensate with left roll. This  can give that tipping over effect. If not I would try trimming a touch of left rudder and check the servo is centering with no slop in the rudder linkages etc.

There is also the possibility that you haven't got enough nose weight as it seems to pich up and down?

Your rearward tilt might be very close to being in autorotation which could cause this effect, if you add nose weight (or extra negative shims) this will force you to trim back the rotor disc for neutral flight giving the blades a more constant airflow through them.

Easiest way to check CG is to take it up high and turn off motor, if correct it should drop its nose and descend forwards slightly.

If its incorrect it will stop, hang its tail and do a pirouette, repeating as it tries to weather cock back into wind.

Whilst testing this do not touch the pitch, just leave it in its neutral position.

 

Let me know what you find?

 

Rich

I removed (basically 0) right thrust and add another 30g in th nose. Something that is not clear for me. How adding extra. Egative shims (aka having more negative pitch on the blades) will force me to trim it more rear , should not be the opposite, should be?

[Richard Harris]

Increasing negative incidence will reduce lift forcing you to add rearward trim to compensate. Weight into the nose should do the same and is the first port of call,  check the power off decent first.

[riktor]

On 09/05/2023 at 15:46, Richard Harris said:

Increasing negative incidence will reduce lift forcing you to add rearward trim to compensate. Weight into the nose should do the same and is the first port of call,  check the power off decent first.

So removing the right angle to the motor had definitely improved stability, same as adding weight in the nose.

I did the test for the GC and the panther descend almost vertical and sometimes I had to pitch down a bit.

 

I have now increase the negative pitch of the baldes and waiting to test again.

 

How many degrees I should have on the blades ?