converting RAF2000 to the superior Sport Copter rotor system

eddie

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kolibri your stick shake could from the rotor hub bar being off center just a tad,put a mic

on it and adjust the hub one way about 0.005 at a time,if the shake is increased go back

the other way 0.010 5 to get you back to center and 0.005 the other way. keep going

5 at a time until its smooth.



best regards,
 

Kolibri

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Thanks, eddie, I'll keep that in mind. Jim's hunch is rotor tracking. Whatever it is, I'm sure I can smoothen it out.
 

Kolibri

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Haven't yet been back for more flight testing, but will in a couple of days. Meanwhile, here are some comments on how much to tighten the mast bushing bolt (all in general agreement):

The bottom 1/2" bolt needs to be very tight, and the top bolt that goes through the "magic" bush needs to be loose enough to just see daylight between the upper mast plates and the 1/8" nylon spacers.
Torque the bolt that goes thru the cam & only tighten the bolt thru the bushing until snug
The bolt thru the donut should not flatten the cheekplates hard against the plastic rub plates. This would cause the donut to really compress around the thru bolt and really restrict the flexing from the rotor...causing more stick shake and cabin hop.

That's the purpose of my backing off the donut nut, by one flat increments, then fly and evaluate the effect on stick shake and cabin hop.
I definitely can't "see daylight" between the cheek plates and nylon sheets (at 25 ft/lbs current torque), so I will experiment with gradually loosening the bushing nut. I want to eliminate that as a possiblity first, before I begin to adjust the hub bar.

Regards, Kolibri
 

Kolibri

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halfway through Phase 1 flight test

halfway through Phase 1 flight test

Just flew her 2.0 hours, mainly at higher altitudes (up to 8,000' MSL) to test climb rate. May have to increase pitch a bit for our western mountainous altitudes (field elevations are 4000' min.).


disparity between cylinder responses:
For my setup, nose-down and left roll are about twice as abrupt than pressurizing for nose-up and right roll.​


trimming pitch during takeoff roll:
Since the air-trim has no "memory" once pressure has dissipated, one must start from zero on the first takeoff. It's not a huge deal, but a technique to think through and iron out. (A newbie would find this perhaps overly challenging.)

There seems plenty of nose-up built in with my 4° cheek plate angle and #3 mast cg setting, and though I've not yet flown with pax ballast weight but I'm sure to have sufficient AOA for it.

I think my technique will be to backtaxi with full nose-down pitch, and then on the roll tap the nose-up button once or twice. Otherwise, the forward stick pressure can be pretty strong on the roll.​


higher airspeeds:
I've definitely 5-10mph more than with the RAF blades, and will next flight record some AS/GS/RPM data to compare.​


thoughts on the air-trim system:
LOL, it's a hoot. I fly in gusty air near mountains, and conditions change often. Once, with the old RAF cable trim, I was flying back with a hideous crosswind up there, and after cranking in all the roll trim available, I still had to lean on the stick the whole way back. No more.

What I really appreciate is the SC trim system being independent from the control yoke/tubes/gimbal arm (which I believe is overstressed in the OEM trim linkage). The more I think about RAF adding trim forces to the lower control yoke, the more I shudder in retrospect. Thin wall (0.065") yoke tubes, $2 low-carbon rod ends, and dog-collar chains holding screen-door springs is a recipe for failure (and it's happened before).

Those without SC's air-trim should seriously consider at least adding a rear gimbal arm (use the old RAF arm if you've already upgraded to a Wayne Hubbs arm) on the torque tube and relocating trim cable/springs there. Such could at least prevent a full pitch-down from control linkage failure.

Now, if something breaks in my control linkage, I believe that I could effectively retain flight control via SC's 4-way trim (since the rotorhead would already be in trim from input secondary to the control-sticked gimbal arm). Landing on air-trim alone would be challenging, but I think an experienced pilot could do so and likely save the aircraft as well.​

All in all, it's going well.

Regards, Kolibri
 
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eddie

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I have found that triming for level flight and leaving the trim there works best for me,

holding a little back pressure on landing isnt really a big deal (my trim indicator doesnt work)

taking off with the trim to far back can be a cause for real problems on takeoff, it can

take a lot of forward stick pressure to keep the nose down for me if the the trim is to far

back from being in the landing setting. Also the tighting or loosing of the bushing bolt

really does not make a lot of noticable difference as to the shaking. But perhaps the

sporcopter blades will already be inherently more stable and then there will be a noticable

difference with the adjustment.





Best regards,
 

Kolibri

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My experience with the SC rotor system so far is that trim requirements are more frequent than with the OEM system. Since I replaced the rotors and trim system concurrently, I can't parse out which contributed more to that.

My impression is that the takeoff and landing trim settings are greater than with OEM cable trim.

As far as stick shake vs. mast bushing bolt torque goes, since I today negated any issue of excessive torque (i.e., I can now see daylight . . . ), the remaining stick shake must be caused by slightly mistracking blades. I'll deal with that adjustment next flight.

Cheers, Kolibri
 

Wiplash

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Once, with the old RAF cable trim, I was flying back with a hideous crosswind up there, and after cranking in all the roll trim available, I still had to lean on the stick the whole back.

I'm confused by this statement.

Let me first say that I've never flown in an RAF and have never flown in the mountains. All of my flying has been in "The Black" and my Lowrider Air Command and I only have 88 hours of flying experience.

Why would you have to hold side pressure or use roll trim to counter a crosswind? Wouldn't you be crabbing into the wind to counter a crosswind during cruise flight?
 

Aussie_Paul

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I'm confused by this statement.

Let me first say that I've never flown in an RAF and have never flown in the mountains. All of my flying has been in "The Black" and my Lowrider Air Command and I only have 88 hours of flying experience.

Why would you have to hold side pressure or use roll trim to counter a crosswind? Wouldn't you be crabbing into the wind to counter a crosswind during cruise flight?
Exactly.

Aussie Paul. :)
 

eddie

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The only time I've had to hold side stick was to stay away from a canyon wall because of

a side wind or gust pushing me towards it,perhaps that was what he was trying to say,

when flying X-country its like you say you just crab into the wind to hold course.






Best regards,
 

Kolibri

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clarification: that was back when I was still trying to adjust the cable trim chains for pitch and roll balance, and hadn't then enough right roll trim to fly without right seat ballast. The x-wind exacerbated the condition. Sure, one normally rudders into a x-wind.

_______
Am looking forward to making the final tweaks. My RRPM seems a bit high at 350, so pitch may need to be increased ½° for >3500' here out West. (I had the same issue with the RAF blades, but left them as is.)

Regards, Kolibri
 
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fara

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clarification: that was back when I was still trying to adjust the cable trim chains for pitch and roll balance, and hadn't then enough right roll trim to fly without right seat ballast. The x-wind exacerbated the condition. Sure, one normally rudders into a x-wind.

_______
Am looking forward to making the final tweaks. My RRPM seems a bit high at 350, so pitch may need to be increased ½° for >3500' here out West. (I had the same issue with the RAF blades, but left them as is.)

Regards, Kolibri
That still doesn't make sense.
Normally one does not rudder into x wind. One simply flies like there is no rudder by crabbing into x wind unless you are uncoordinated like in a slip which you should only do on a crosswind landing final approach and not in normal cruise flight.
Now the trim due to side by side config where one seat is empty. Ok but I don't know if roll trim is better or you should carry a little ballast weight like many helis do but once the roll trim is adjusted that also should be hands off flying I think.
For example, we use electric linear actuator with a spring now to trim for pitch on AR1. The rotor is trying to fly at fastest position and the spring is pulling it down to trim at slower speeds. The air system does the same thing. In gusts that trim pressure acts as a nice dampening device actually. For roll, we have simply a fixed spring on the left lower control rod and adjust it once to take any roll out. We never have to touch it again at any speed to Vh. It flies hands off but it's a tandem configuration not side by side.
The cabin hop seems to be due to tracking and excessive stick shake due to balance. You can't do anything for 2 per rev shake. Though those bushings in your mast should if set properly hide the tracking issue. I not quite sure I like the bushing idea. Calidus does that also so perhaps it's ok but having the mast divided in upper and lower halves and joined loosely with elastomer bushings and bolts going through the center of them seems like idea to try which I have not yet. It seems to work on Calidus and Sport Copter and RAF I guess.

Wish you the best of luck.
 
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Kolibri

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Normally one does not rudder into x wind. One simply flies like there is no rudder by crabbing into x wind . . .
fara, are we not speaking of the same thing? How does one crab into x-wind without the rudder?


Now the trim due to side by side config where one seat is empty. Ok but I don't know if roll trim is better or you should carry a little ballast weight like many helis do but once the roll trim is adjusted that also should be hands off flying I think.
I'll experiment with roll trim with/without a flat weight on the floor. I'd rather not have to carry it, though.


. . . having the mast divided in upper and lower halves and joined loosely with elastomer bushings and bolts going through the center of them seems like idea to try which I have not yet. It seems to work on Calidus and Sport Copter and RAF I guess.
Jim Vanek speaks well of the RAF 2-part mast, and with a new bushing installed and all the nice SC parts, I should be able to null out most of the stick shake. The SC rotorhead is bushed, which must also help. Cabin hop is less pronounced than stick shake. Thanks for your comments, and good luck to you on your AR-1.

Should have it all squared away next week. Not flying today due to high winds, some actually 50kts not far away.

Regards, Kolibri
 
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eddie

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I think that Fare is right, you use rudder not to crab into the wind,you lower the side

into the wind and then use the rudder to maintain a straight line (on Course) usually

lots of rudder. Thats the way I land in a cross wind its also called a forward slip. I lower

my side into the wind and then use rudder for a straight line of travel with the centerline

when I lower my tail to the runway the gyro will weathervane into the wind and at that

time my airspeed is at zero. Easy Peasy. A crab is when you are flying sideways to go

forward in the direction you want to go,thats also about the time you realize you are way

in over your head with regards to the wind.




Best regards,
 

Kolibri

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Thanks, eddie. I don't quite get how this all got tangled up (probably due to differing techniques for varying x-wind strength), but let's move on.

_______
Still waiting for winds <30kts in between snowstorms for the rest of my Phase 1. Ah, well, back to work meanwhile on other things.

Next flight I'm going to very precisely track the blade reflectors with a mirror or tac light, as apparently they are very sensitive to variation.

For 30' SC blades, .010" pitch block bolt adjustment means 1" at blade tip.
For a 24tpi hexagonal bolt:

½ flat will move .00347" = 0.35" at tip
1 flat .00694" = 0.69" at tip
1½ flats .01042" = 1.04" at tip
2 flats .01389" = 1.39" at tip​

I haven't much cabin hop, and since SC balances all rotors to hub bar I suspect that balance is good.

Regarding rotor pitch for altitude, I seem to be right in that cusp of where standard pitch is OK-though-not-great, and adding a shim may put me on the opposite side of optimal for the other OK-though-not-great.

Regards, Kolibri
 

eddie

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We are on the south end of the same storm very high winds 40+. I thought the blades

were flown before shipping,if thats so the track should be perfect ? I had to increase my pitch 1/2 degree @ my alt.



Best regards,
 

Kolibri

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Yeah, it's a doozy, ain't it?

____
Jim does fly each set of blades before shipping, and so I wondered the same. If I had to guess, it's probably related to miniscule-though-stacked variances of bolts and torque from my assembly vs. SC's. There are two plates per blade between the tension straps; lots of things bolted together to line up. I suspect such could easily cause ¾" of tip difference.

I'll bet just a squinch of pitch block adjustment will do it. Probably every owner should expect the same; seems pretty normal.

When do you get yours? (Since you'll be using RAF cable trim, it'd be nice to hear from others about that here.)

Regards, Kolibri
 

fara

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fara, are we not speaking of the same thing? How does one crab into x-wind without the rudder?



I'll experiment with roll trim with/without a flat weight on the floor. I'd rather not have to carry it, though.



Jim Vanek speaks well of the RAF 2-part mast, and with a new bushing installed and all the nice SC parts, I should be able to null out most of the stick shake. The SC rotorhead is bushed, which must also help. Cabin hop is less pronounced than stick shake. Thanks for your comments, and good luck to you on your AR-1.

Should have it all squared away next week. Not flying today due to high winds, some actually 50kts not far away.

Regards, Kolibri
Hi Kolibri:
Crabbing should not require rudder action.
I think a decent explanation is given here

http://www.askacfi.com/3010/crabbing-slip-sideslip.htm

Crabbing is completely control neutral

May be its just semantics but they are important to differentiate between a slip and crab. One is un-coordinated flight and one is co-ordinated
 

Kolibri

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Yep, it's been a semantical misunderstanding, thanks.

I didn't mean for anyone to infer that I recommend uncoordinated flight at cruise.
 

eddie

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My pitch trim is the stabalator,it is a true aerodynamic trim. It really works excellent.

and it is electrically operated (toggle switch). Should be around the end of the month.






Best regards,
 

Vance

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Depends on your point of reference.

Depends on your point of reference.

Hi Kolibri:
Crabbing should not require rudder action.
I think a decent explanation is given here

http://www.askacfi.com/3010/crabbing-slip-sideslip.htm

Crabbing is completely control neutral

May be its just semantics but they are important to differentiate between a slip and crab. One is un-coordinated flight and one is co-ordinated
From the FAA Aerosense Glossary:

Crabbing: A rudder-controlled yawing motion to compensate for a crosswind in maintaining a desired flight path, as in a landing approach.
 
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