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Panther Trainer Autogyro

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Panther Autogyro

Panther Autogyro

info for builders of RCM&E's March 2013 free plan

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Second Time Around

Second Time Around

Colin Budds rediscovers his love of autogyros

Steve Jones 229/03/2017 06:20:30
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498 forum posts
369 photos

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don cardy29/03/2017 11:15:17
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19 forum posts
37 photos

Hi Everyone

The last two posts have been interesting and add to the discussion about the position of Panther's CG. If a normal Panther balances slightly nose down using the position shown in the plan - using ferrules to aid this process - then the actual CG is somewhere on a line passing downwards slightly forward of vertical through the ferrule. I don't now have a "normal" Panther to check but my estimates are that the CG will be just over 1 cm below but slightly forward of the ferrule. The fact that the CG is some way below the ferrule is confirmed by the reported balancing tests which indicate that Panther takes up a slightly nose-down but stable position. If the CG is in the position I suggest then with the down thrust shown on the plan the thrust line passes about 1 cm below the CG.

With the pre-rotator I have added to my Panther the CG is raised by at least 1 cm and is almost exactly at the point where the pylon enters the fuselage. This means that the normal thrust line passes at least 2 cm below my CG and may be the cause of some of the instability I have struggled with. I've therefore increased my down thrust to compensate.

I have noticed how some posts have referred to the improvement after the battery has been lowered in the battery compartment. This clearly influences the vertical position of the CG rather than the fore and aft position. I've been doing some measurements on the effect of putting ballast effectively on the floor of the battery compartment at the front. This both moves the CG both forwards and downwards and my measurements suggest by roughly the same amount in both directions. I'm hoping to test this out in practice when the wind drops - in my case is it the fore and aft or vertical CG position which is the more crucial to get right?

Don

don cardy29/03/2017 21:49:11
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19 forum posts
37 photos

Hi Everyone,

Below are two pictures of a hang test to show where the vertical CG is on my Panther. Remember that my CG is higher than normal by about 1 cm because of my use of a pre-rotator. This hang test includes the effect of about 80 gm of ballast under the battery compartment which moves the CG forward a bit in the fore and aft direction but helpfully lowers the CG too. Thus the close-up shows that the CG is marginally below the junction of the pylon and the fuselage whereas without the ballast it is on that junction.. The hang test involved removing the battery compartment cover and then allowing Panther to swing on a rod held across the back of the firewall where it enters the battery compartment. A bit scary but I think safe.

Don

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don cardy05/07/2017 16:10:41
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19 forum posts
37 photos

Hi Everyone,

Much time has passed so it's time for an update on progress with my Panther. After many, many repairs, my original Panther was confined to the dustbin and a No2 version built and more lately a No3 too. These later models are an attempt to deal with the various problems encountered with No1, but sadly will do little to help when disorientation rears its head!.

Setting aside the disorientation issue, and ignoring some of the red-herrings which arose along the way, the problems I had after a very successful maiden flight with No1 seem largely to be related to the addition of an extra 100gm at the top of the pylon in the form of a pre-rotator and the later update of this unit to use a 6mm spindle and a quite large and rigid hub at the center of the rotor's delta plate.

The pre-rotator had two effects; it raised the CG vertically by at least 1cm and at the same time moved the CG backwards so extra ballast was needed in the nose such that the AUW of Panther was increased by at least 200gm. My Panthers have all tipped the scales at over 2kg; No2 is 2.37kg and No3 is 2.28kg.

This issue of AUW is interesting. When designing Panther Rich Harris aimed at a disk loading of under 5oz/sq ft and chose a rotor diameter of 46in. If Panther weighs 1.7kg the disk loading is 5.2oz/sq ft, but at 2.4kg this increases to 7.36oz/sq ft. Now there seem to be quite a number of heavy Panthers running quite successfully at around this disk loading, but nonetheless I've settled on increasing my rotor diameter to 50in to reduce the disk loading of my heaviest Panther (No2) to 6.2oz/ sq ft.

There is another issue relating to AUW and that is the power/weight ratio of Panther. With an AUW of 1.7kg and using Rich's recommended motor 350W minimum the ratio is 93W/lb which is within the range recommended for sports models, but increase the weight to 2.4kg and the ratio drops to 66W/lb. By upgrading from a 3s to a 4s battery and aiming at a minimum of 500W the ratio becomes a more acceptable 95W/lb.

The issue of the rising vertical CG position is the most critical of the lot. The recommendation is that the motor's thrust line should pass through the CG position; Rich says "or slightly above the CG position". To achieve this the thrust line on my original Panther need to be raised by increasing the downthrust. In my later Panthers I've lengthened the nose section and fitted the motor directly to and at the top of the firewall. With this arrangement the thrust line passes only 5mm below the CG. The pictures below illustrate the arrangement.

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I've practised making rotor blades of various lengths on a thin ply substrate. Lightening holes have been used to limite the weight increase to about 10gm more than a blade of standard construction. The picture below shows one set of more normal length blades. My No2 and No3 Panthers use blades with this construction and are 600mm long to achieve a rotor diameter of 50 in. The blades are mounted with the flat underside at a negative incidence of 1 degree as measured by a pitch gauge. This appears to give a reliable spin-up.

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Being new to autogyros I have rigorously stuck to the gymbal pitch being set at 6 degrees positive and the leftwards tilt at 2 degrees as recommended for Panther's initial settings. With my lack of success with Panther No1, I decided after hop tests with No2 to take this model to the 2017 UK international Gyro Meet at Winterton and to seek help with trimming.

I'll continue this story in a second post.

Don

don cardy05/07/2017 16:16:09
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19 forum posts
37 photos

Hi Everyone.

My trip to the Winterton Meet was very rewarding. This picture below shows No2 ready for that trip with a partially completed No3 in the background.

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I had a wonderful time at that meet and am grateful to Rich Elliott for so willingly trimming the model out. I shall long remember Rich holding my TX in the air and exclaiming "hands free", and am grateful to designer Rich Harris for taking some nice pictures of my Panther the next day.

So what emerged from the trimming? The gymbal pitch has increased from my 6 degrees to 10.5 degrees and the leftwards tilt from my 2 degrees to 7 degrees. Now these seem to be quite significant changes but I can guarantee they are right because Panther No2 has had several short smooth flights without mishap.

I am going to attempt a tentative analysis in the hope that others might chip in and confirm or otherwise. The original Panther design with its short plain bearing for the rotor would had had lots of give in the backward tilt direction adding to that of the pylon. Those who use old gearboxes for the rotor shaft often use a simple prop mounting to secure the rotor's delta plate. Some of the spindles are only 4mm diameter. Thus with a slim spindle secured to the very centre of the delta plate there is probably quite a lot of flexibility in the backward tilt direction, again adding to that set on the gymbal. In my case, with the pre-rotator I have a strong spindle (it has never bent in all the crashes I had with No1) and a stiffened centre to the delta plate because of the large ply bosses I am using. With such stiffness built in, did the gymbal tilt back have to be increase to 10.5 degrees to compensate? The picture below shows my pre-rotator head.

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This leaves me with the issue of the gymbal's leftwards tilt increased to 7 degrees. Rich Harris told me that this is all about compensating for coning and I've found stuff elsewhere which attempts to explain all this. Clearly the heavier the model the more coning there will be and my Panthers are on the heavy side. At the same time I'm using longer blades but of a very similar weight to the standard blades. Are mine rotating less fast than normal and therefore coning more? Lots of unanswered question which perhaps only telemetering can help with? All I can say is that I'm grateful to have a Panther which now flies well and after several successful short flights with a normal landing look forward now to improving my piloting skills.

Don

Trevor05/07/2017 21:40:41
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355 forum posts
51 photos

Glad you got it sorted in the end Don. Good luck with the next one!

Trevor

Richard Harris06/07/2017 00:11:42
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2033 forum posts
1865 photos

Don,

It was a pleasure meeting you and your wife and great to see your Panther take to the skies. I did take a number of photos but am struggling to upload photos onto this site of late.

I have managed one

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Same place next year I hope, it will be our 10th Annual meet

Rich

Leif Scott06/07/2017 15:44:13
3 forum posts
5 photos

Hello all,

I finally got a couple finished. The red one is OS52 four stroke powered, yet to have a test flight due to engine issue.

Blue and yellow is turbine powered, ops I mean electron powered and has one test flight so far. it was a little harry but made a few adjustments and hopefully will get another test flight this evening.

A special thanks goes out to Maakus and ismith2uk as I loved their colour schemes and shamelessly copied them.

A few construction elements:

Rotor heads are machined aluminum with press fit flanged cartridge bearings and the shaft is 1/4 diameter AN bolt (AN is full size aircraft grade bolts). Firewall on the glow version was moved back to allow for longer engine. This reduced the compartment behind enough that I was forced to make a custom fir fuel tank. This was all done to try and achieve the flying characteristics designed by Richard. In hindsight I should have left the firewall where it was and had a longer nose as I had to put some ballast in the cowl.

Aside from that, the plans were followed and no significant deviations were made.

Cheers to everyone and happy rotating,

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Richard Harris06/07/2017 22:59:48
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2033 forum posts
1865 photos

Leif,

Very well finished Panthers, I have always liked Ian's yellow and blue scheme so a good choice there thumbs up

Don,

I have managed to upload a few photos via my phone, I have added these elsewhere so I hope you don't mind me posting them? Kind of gives the feel of our annual meet, great helpful bunch they are!

You may have more left and up trim probably due to the weight but it flies, and flies extremely well smile

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Rich

Corsair01507/08/2017 23:00:52
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13 forum posts

Hi, I am about to start building a panther autogyro, and I was wondering, is it possible to use factory made blades of the same specs instead of building them? I do not have the skill to properly build my own.

Thanks

Richard Harris08/08/2017 09:35:42
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2033 forum posts
1865 photos

Hi Celab and welcome to the forum smile

Before you go spending good money on blades that may not be suitable please link us to what you are looking at?

The blades and their aerofoil are key to making the Panther successful in the air, any deviations could be expensive.

Try to steer clear of helicopter blades as these will just not work.

Despite what you may think about making blades they really aren't hard to put together. we can guide you through the process step by step if it helps?

Rich

Steve Jones 208/08/2017 20:22:05
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498 forum posts
369 photos

Don't be put off by making blades, they are straight forward if you follow Rich guidelines. Just make sure they are balanced and you will be fine

Steve

Corsair01508/08/2017 23:32:02
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13 forum posts
Posted by Richard Harris on 08/08/2017 09:35:42:

Hi Celab and welcome to the forum smile

Before you go spending good money on blades that may not be suitable please link us to what you are looking at?

The blades and their aerofoil are key to making the Panther successful in the air, any deviations could be expensive.

Try to steer clear of helicopter blades as these will just not work.

Despite what you may think about making blades they really aren't hard to put together. we can guide you through the process step by step if it helps?

Rich

Thanks, I will try my best at building them I cannot start the build any time soon, as I am moving.

When I do though, as soon as I get to the blades, I will ask for help.

It is nice to know people are there to give advice and help when problems arise.

Thanks.

Corsair01508/08/2017 23:32:47
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13 forum posts
Posted by Steve Jones 2 on 08/08/2017 20:22:05:

Don't be put off by making blades, they are straight forward if you follow Rich guidelines. Just make sure they are balanced and you will be fine

Steve

Thanks, I will give it my best shot!

Corsair01508/08/2017 23:32:50
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13 forum posts
Posted by Steve Jones 2 on 08/08/2017 20:22:05:

Don't be put off by making blades, they are straight forward if you follow Rich guidelines. Just make sure they are balanced and you will be fine

Steve

Thanks, I will give it my best shot!

Richard Harris19/11/2017 16:12:07
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2033 forum posts
1865 photos

I received an email during the week from a gent called John over the pond in New Jersey,USA. John has just completed his Panther and has modified it by adding a stub wing to help him with orientation. Though not flown as yet I thought it was more than worthy of a post as he has made a cracking job.

Its great to see these models still being built, I will hopefully get a full flight report back in the coming months.

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Rich

nuno ribeiro22/04/2018 23:10:16
1 forum posts
53 photos

Greatings,sorry not about the Panther thaat is almost done,but having bought the dag R2 plans,and expanded to the Dag 60 measures,I wonder if i could use and fly the same full tethering head?thank you

Nuno Ribeiro

ken anderson.23/04/2018 16:22:09
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8409 forum posts
772 photos

anyone near me in ne...1.... land thinking about building a panther..... I have a completed fuz and some other bits including a top notch head and a couple of brand new heavy duty servo's.......get in touch with me for a bargain.....collection only...send me a PM.........no hooks thanks..who want the gear for next to nothing.....

ken Anderson...ne...1...panther dept.

Richard Harris24/04/2018 09:36:50
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2033 forum posts
1865 photos

Nuno,

Yes, you can use the same type of head just remember to upsize your servos to suit.

Ken,

Why don't you finish it? if you can upload some pictures I will post it onto the FB group.

Rich

ken anderson.24/04/2018 17:07:32
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8409 forum posts
772 photos

hello rich...I did have a few go's with Tom's Cranefly's..and in the meantime got all the stuff together and commenced building the Panther...but lost interest and its lying there in limbo ......

ken Anderson...ne..1..... limbo dept.

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