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Jun 28, 2019, 05:43 AM
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britinoz's Avatar
I am now the owner of one of these models that is in pretty good condition with a couple of minor scuffs as well as the motor has been remounted towards the rear as well as some interior frame removing.The horizontal stab was a little rough and I decided to replace it with balsa.
I am curious as to the reference points for working out the hang angle.I would expect the horizontal stab to be at zero deg...but I'm not quite sure that is correct on this modelas after removing the old ..I find the the top of the fin is at about 6-8 deg +.
Now I don't know if this is just the moulding shape of the stab or does run at an angle.
I would have thought that the prop should be square to the stab??
To get the motor square to a flat surface..I have to block up the nose by 32mm
So is the motor angle or the stab used as a reference to the hang ??
I have done a little tinkering on the frame and was surprised to find a 17 gm MG servo being used on the steering ..I first thought it was a bit of an overkill but later found that the plumbing is not the best and that servo is working overtime just to move.The outer pushrod tube that starts at the fin is not the same as the one that exits in the fuz.There is a a gap in the middle where the inner pushrod runs in direct contact to the foam and it is one big load on the servo.
I noted that the makers had installed a nice ventilation hole in the underside of the fuz and then filled most of that hole with a steering servo and mounting plate. I have now remounted the servo well away from the hole.I have of coarse started making a new set of blades to replace the supplied chop sticks.
I have gone with 790 X 61 mm that may be trimmed a little shorter.In there basic shape prior to covering ,come in at 84 gms each.
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Jun 28, 2019, 04:12 PM
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106flyer's Avatar
Chris , you need to pick the brains of Graham as his flew well only after mods and fantastic piloting by Rich E

Steve
Jun 29, 2019, 12:40 AM
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britinoz's Avatar
Thank's Steve
I am aware of that......I was hoping that he would pick up on this one.
Chris...
Last edited by britinoz; Jun 29, 2019 at 06:09 AM.
Jun 29, 2019, 05:05 PM
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Ricardo1500's Avatar
Chris did you get my reply email??
Jun 29, 2019, 06:03 PM
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britinoz's Avatar
Rich
Yes thanks I did and took your suggested action.
Chris...
Jul 01, 2019, 09:00 AM
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Chris

Sorry for the delay in replying as have had a few home issues recently which have come between me and the forums.

Firstly in your PM I was not able to get back on the question of hang angle. I tried to reply but it would just not go. Anyway my hang is at 23 degrees being the best I could get without surgery to the frame and the battery back against the ply former. It flies fine at that but has backtilt of 17 degrees which is not a major issue but does put the blades fairly close to the top of the fin. However, as the head has zero flex this has not been an issue. If the hang could be reduced a bit more to say 20 degrees then it would need less backtilt and the blades would be more efficient by operating at a shallower angle. However I have not tried this although most pusher gyros are happy at around 20 degrees. . As supplied the hang angle was over 30 degrees and would account for the many reports of the model dropping its nose and crashing when a turn was initiated.

My hang is measured from the top of the aluminium motor mounting channel as the datum line and the model has the right sit in the air so I guess that is pretty close.

With the existing motor and extended shaft setup the motor is mounted with the motor shaft centre 33mm above the aluminium channel it sits on. The extended shaft runs parallel to that channel and exits the fuselage with no up/down or sidethrust.

The tailplane sits at a positive angle of 5 degrees and the front centre of the V sits directly in line with the centre of the spinner.

Re the steering servo. I have used the inner servo holes on both the snake and the simple wire pushrod to the nosewheel and that seems to work without binding. I have not taken the snake wire out but used it as is.

Hope this and the other info helps.

Keep me posted as to how it goes.

Cheers

Graham
Jul 01, 2019, 07:32 PM
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britinoz's Avatar
Graham
Thanks for the info.that is just about what I wanted to know BUt I am surprised about the + stab.although that's what all my measuring was telling me.
I have made a set of blades 790 X 61 with 10 oz tip weights that came in at 103 gms each when completed...that would be pretty similar in weight to your when you take the size difference. Yesterday I ran them up on my work bench (with the model strapped to it )and found that at flat chat there was a bit of flutter...but I'm thinking that they were running possibly faster than required in flight.
Rich E advised me that I could have probs with long blades and so going to trim them back to about 28" and try that.With a 3300 lipo my model comes in at 84 Ozs with a disc loading of about 4 OZS so reducing the blades a little should still give me a floater.But what a pain balancing a two blade set up.
Chris...
Jul 02, 2019, 02:03 AM
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Hi Chris

Tend to agree with Rich E. Mine flies reasonably floaty on 710 mm blades and lifts off and lands at slow speeds., so would not wish to go more than another 10-15mm. Also the tip weights ( presume you mean 10 grams!) are the same as mine.
I pushed the mounting hole another couple of mm forwards than normal to compensate for the extra backtilt.

Graham
Jul 02, 2019, 04:51 AM
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britinoz's Avatar
Graham
Thanks for the update...work in progress.
Chris...
Jul 06, 2019, 05:16 AM
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britinoz's Avatar
Graham
I was wondering if you noticed any tip noise when running up on the prerotor?
I have balanced my blades and they get up to speed with a bit of a "wobble" but at top speed run OK but they put out quite a "howl" although I'm pretty sure that they are spinning considerably faster than they would in flight.
I have ordered some blade blanks from Astik Models in Latvia that are 900 X 61 (need a bit of trimming) so hopefully will be able to give them a go soon.
Chris...
Jul 15, 2019, 06:04 AM
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Chris.

Other than the usual whistle when the blades get up to speed there is no unusual noise or vibration when on the pre rotator. I wonder if the bolt hole is too far forward causing them to become unstable due to the greater backtilt?

Just checked my blades. My bolt hole is 22 mm back from the leading edge and the blades balance level crosswise with pin in each end , at 18mm from le. Lengthwise cg is 327mm from tip and total blade length 710mm. Blade weight is 90.5 grams.
The other thing here is that there is no flex or teeter in the head and therefore the head will not cone other than any natural flex in the wood of the blades. Not 100% sure but could more tip weight help?

Graham



more tip weight might help
Jul 15, 2019, 07:30 PM
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britinoz's Avatar
Thanks Graham
All you info is noted.
I have the Astik blades in transit at the moment and they are a 65mm wide compared to your 61mm and will be making up a pair when they arrive.
I am hoping for a better result with them compared to my home made ones.They have a good autogyro profile.
My set have a very solid 2mm T/E and this may cause the noise that I mentioned.
It was similar to "flutter".
I have noticed a lot of noise/ vibration when running up the motor that I think is coming from the metal tubing.I have never come across this on any of my models and I guessing that is because I have been using timber as a crutch and this would dampen the sound.
Chris...
Jul 20, 2019, 05:39 AM
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Chris

I just remembered that my supplied prop was way out of balance as supplied - could that be part of your vibration?

Graham
Jul 21, 2019, 08:09 PM
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britinoz's Avatar
Oh that prop...yes it could be out of balance as I have not checked it yet.But what a pathetic piece of twisted plastic it is.
Should I manage to get this model flying OK ..then I will be definitely looking for a replacement.
Chris...
Jul 29, 2019, 03:26 AM
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britinoz's Avatar
I'v made up a set of Astik blades ,and did a bit of a test today. Ran them up to around 1500 RPM with out any apparent vibration. I actually made two sets . One at 65mm width and one at 55mm,both at 710mm / 28" long.These ran up a lot better than my own builds.
The question is ....does it look as if I have enough head speed for ROG....I think that I do ..But But,what do I know.
Chris...

Testing ASTIK Blades on AC-10 Autogyro (5 min 4 sec)


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