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Thunder Power RC . Mikado Modellhubschrauber . Futaba-RC

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Aerobatic FAI F3C Contest > Vibe 90 SG for FAI setup
 
 
mdu6
Key Veteran
Location: Montreal

My Posts This: Topic  Forum

I'm getting a head shake at those speed ... 720RT with F3C RT

Can it be I'm running with the main blades a bit too tight ?

Everything is smooth, no vibration and shake above 1800 and
as per Scott's instruction did not use the spindle shaft tube.
11-13-2009 10:53 AM
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blt4ice
Key Veteran
Location: Newark, DE

My Posts This: Topic  Forum		Wait here, main blades too tight? So they should not be as tight as I would normally have them on a 3d machine?

Brian
Heli tools used: Torch, Pipe Wrench, 4 ft. crowbar
11-13-2009 01:06 PM
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Dr.Ben
rrProfessor
Location: Richmond, VA, USA

My Posts This: Topic  Forum		Often with stiffer heads and higher flybar ratios, you need to keep the blades a little looser to avoid a mast bump at lower headspeeds.

Spacey, RPM with those blades is more a function of model than the blade itself. I've run them on several different models and five different kinds of heads. I can tell you for a fact that running my Eagle or Freya at 1700 rpm would be unpleasant to fly in the box. The glow model sits fine at 1500 on the glow model, and there or a bit more on the electric since it weighs more. I believe we tached Wayne and Dwight in the mid to low 1600's last season, and that was up from where they had run for years. I would hope a SG won't mast bumpy badly at anything below 1600 rpm, because if it does, then any slow or (yuk) stretched auto with low final headspeed is going to get ugly. Like we've never had that happen......

The basis for the 1500's is not so much that it's always an ideal rpm range. Rather, in the case of this relative newcomer to this style of flying, it rather assures that the model won't start off mast bumping like a fool at 1400 rpm or a jumpy, twitchy affair due to excess headspeed and cyclic rates. Wherever it ends up from there is truly a matter of taste and feel on his particular model. Scott's reflexes (and yours) are lightning fast d/t youth. Those set ups often don't work for anyone with tortoise nervosa, so recs have to made in consideration of these variables as well since these forums have a wide audience.

Ben Minor

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines
11-13-2009 01:31 PM
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Spacey
Veteran
Location: Pretoria, South Africa

My Posts This: Topic  Forum		Hi Ben,

We will agree to dissagree then on this one.

I run both my Sylphides at 1660~1680RPM during the hover, it was same at the worlds now even in the thicker air. Sure you can probably safely argue I didn't get everything right cause you saw some of my hovering, but I'm the last person on this planet in the F3C world to have anything good to say about my hovering skills. LOL. My biggest problem at the worlds though was mainly due to me running too soft dampening and the wind making the pod bounce around, I think I got that under control now as I found a way to rid of my auto wobbles and increase the dampening for the new schedules.

Either way, I purely go out to find each set of blades's ideal RPM where the wind bounces it around vertically the least first (Vertical being key word here, nothing else). I've definitely found that each set of blades has a magic RPM in the hover where it will move up and down the least due to wind changes. Unfortunately for us this changes with each and every blade, even blades from the same manufacturer as you probably well know. Only after I've found that sweetspot do I start figuring out dual rates and flybar setups to get it flying and handling to my taste. Of course also sit best in the wind in the other two plains.

My Sylphides both weigh in around 5,3kg dry, so about 5,7kg fully fueled and during most part of the hovering. My team mate Arney with his electric Airskippers were using the same blades, different rotorhead and weighed in around 5,95kg..he confirmed also 1660~1680RPM worked best for him as far as vertical bounce was concerned. Then I have a buddy I helped with a Raptor .90, same blades, confirmed same RPM he was happiest with? Hehehehe

Groete,
Rudolf

Oh on the SG topic as far as wobbles are concerned with low RPM's. I find some of the comments strange to be honest? My SG is unfortunately setup for 3D only so it's got the harder dampers and things in. I've slowed it right down during slightly botched inverted autos and such and there's no wobble to seen anywhere in the RPM range? Heck we've for fun dropped the headspeed while running in to 1200RPM in a hover and it was fine. Unfortunately I haven't tried the 720SG blades on it, but yes I would run them VERY loose in the grips, we've found this a must on most if not all helis really.
11-16-2009 01:18 PM
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Dr.Ben
rrProfessor
Location: Richmond, VA, USA

My Posts This: Topic  Forum		There's no disagreement really. I just think it depends highly on the model you have the blades mounted on. I honestly tried running a higher headspeed on both my Hirobo models, and the model just got too touchy on the collective regardless of what I did to the slope of the pitch curve. I'd be interested to know what headspeed Ennio was running at the worlds since I THINK he was flying the SAB's that have the same airfoil as the RT's use. Probably in the low 16's, but that was just a guess based on "ear". This E3 electric weighs more, so I'll be playing with it more to find where the model wants to sit best. I have to limit it a bit to keep power consumption within reason to get through the round, though.

I'm glad that you've not seen the mast bump at lower rpm's as being a given for that model, because I worried about suggesting 1500 rpm as a start if that model wasn't inherently willing to tolerate that low a headspeed.

A good discussion is a hell of a lot more interesting than everyone agreeing and flying the exact same set up.

Ben

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines
11-16-2009 06:30 PM
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Spacey
Veteran
Location: Pretoria, South Africa

My Posts This: Topic  Forum
Quote 
A good discussion is a hell of a lot more interesting than everyone agreeing and flying the exact same set up.

Haha..will drink to that!

Interesting you found it a little jumpy on the collective for your tastes. I agree with you on that. I took some advice after the Poland worlds from mister Gray though and simplified my setup, so there's less guesswork. So in my case only my normal mode is setup for hovering, in both dead calm and stormy conditions. I've just trained my fingers to relax when it's calm (Yaya no wise cracks by anyone on my performance at the last worlds! Heh). So even my normal setup is fairly aggresive so I can still fight strong and gusty winds to my best abilities. With the "aggresive" setup my pitch range on normal currently runs -2, +3.5~4, +7. And then it is flattened out just a smidge around midstick where the heli hovers.

Beste groete,
Rudolf
11-16-2009 07:23 PM
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ErichF
Elite Veteran
Location: Odessa, FL 33556 (Tampa Area)

My Posts This: Topic  Forum
Quote 
A good discussion is a hell of a lot more interesting than everyone agreeing and flying the exact same set up.

I totally agree.

Erich
11-16-2009 07:40 PM
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GM1
Elite Veteran
Location: Tallahassee, Florida US

My Posts This: Topic  Forum		Headspeed

It's been a while since I used the RT blades other than to test them on someone else's model (I liked the 700s a lot) but my model will not tolerate more than 1520 with the Radix blades and would really prefer about 1370-1420. I had not been able to run that low as the model with the stock dampers would mast bump but with the softer dampers, it seems it will go much lower. What I'm finding is that in the wind, the low head speed is fine collectively but it struggles cyclically, I just don't have enough steering. I turn it up about 50 rpm to get the head to steer better and just tolerate the increased collective sensitivity. Since the wind is jumping it around anyway, no one seems to notice if I get a little collective happy.
Gordie

On a dog sled team, if you're not the lead dog, the view never changes.
11-17-2009 12:40 AM
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Spacey
Veteran
Location: Pretoria, South Africa

My Posts This: Topic  Forum
Quote 
Since the wind is jumping it around anyway, no one seems to notice if I get a little collective happy.

I'd pay good money for some of that Gordie? Think you can mail across the pond?
11-17-2009 06:35 AM
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blt4ice
Key Veteran
Location: Newark, DE

My Posts This: Topic  Forum		So after reading all that great info here is a question.

On headspeed, you will get a more sensative collective input-output the higher rpm? that of course takes into consideration that you are not changing the pitch ranges, only adjusting the headspeed.

So I guess the key then based on the above being true, that the headspeed needs to be figured to where it sits well in a hover without a wobble, yet you can tune down your pitch range to allow for a nice smooth input to get your collective in a stable area. Of course once again another variable would be wind speed and so forth but that is another story

Brian
Heli tools used: Torch, Pipe Wrench, 4 ft. crowbar
11-17-2009 05:08 PM
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helibugger
Heliman
Location: VA

My Posts This: Topic  Forum		Actually, I think there is one other variable... wind.

From what I have seen the higher the headspeed the better the heli will sit in wind. Think of it this way... with a higher headspeed you have a higher wind speed over the blades (they are turning faster) as such a fluctuation in wind will have less effect on the altitude of the heli... lets say you have a wind that jumps from 5 mph to 10 mph, it will more likely impact the heli with a lower headspeed because the change in blade airspeed is more significant on slower spinning blades rather than faster spinning blades...

But then again I could be wrong, but thats what I think is going on....

And yes the higher headspeed the more "sensitive" the controls are... again their is more air moving over the blades. Think of an airplane. When a plane is traveling at 30 mph vs 60 mph... the same amount or surface deflection will change how quickly the plane responds based on airspeed so the higher the Reynolds numbers (the more air flowing over the wing) the more the plane responds.
11-17-2009 05:20 PM
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Spacey
Veteran
Location: Pretoria, South Africa

My Posts This: Topic  Forum		I'm running the risk here of sounding like I want to force my opinion down, which is the last thing I want.

But no, wind will have the same effect regardless of the headspeed really. The amount it changes the blade's relevant airspeed is still the same.

With my method you need to kinda pick a day with gusty wind and strong at that too, we literally hold thumbs for terrible wind conditions if we want to test blades and hovering setups. What we would do is get the heli hovering in the tough wind, take our hands off the collective stick and observe what the heli is doing with the wind, of course the wind will pick the heli up as the wind gusts stronger, and visa versa the heli will drop as the windspeed reduces. Then we start picking up the throttle curve and dropping it untill the effect the wind have on the heli vertically is at its very least. There is a headspeed where the blades will sit best on their own in the gusting windspeed up and down.

Then it's simply a matter of my mate grabbing the tachometer and checking what the headspeed is, then we finetune the pitch/throttle curve and lock the governer after that is said and done. It's also quite easy if you use a governer with remote headspeed adjustments to quickly raise and drop the headspeed to play around a little.

The rest you guys are good on though. Higher the headspeed the more effective any changes in collective pitch and cyclics. Lower just the opposite again.
11-17-2009 07:51 PM
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MANCHA
Senior Heliman
Location: Cabo San Lucas, Baja- Mexico

My Posts This: Topic  Forum		I would like to drop my 2 cents.

I have a SG setted for FAI.
YS red head, JR8717, F611 gyro, 720 sg RT, 30 grms. CF SAB paddles,
soft kit dampers, 105mm SAB tail blades.

sea-level flying club though.

That being written, my lowest confortable RPMs at hover are 1,630.
however I compited last September in my Nationals at 1,830 meters above sea level I used 1,650 rpm, and did ok.

The note about over tiding your main baldes is true, since SG main blade grips are metal you tend to overtide them and there is an inmidiate up-dowm and vibration happening, trust yourself to leave them a little loose, it works.

When I am on competition, early in the morning I place my blades, hover with kind of loose tide, land and re-tide them a little bit and do not move them again, this trick always has helped me !

As a foot note, my FREYA with RADIX 710, hover confortable at sea level at 1,450 rpms but at high altitude it likes 1,550 rpms.

Saludos.
11-18-2009 08:42 PM
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papatango
Veteran
Location: Toronto, Ontario, Canada

My Posts This: Topic  Forum		Somebody pleeeeez choose a head speed so I can finish the e-conversion.....
11-18-2009 10:08 PM
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Dr.Ben
rrProfessor
Location: Richmond, VA, USA

My Posts This: Topic  Forum		Patrick,

The set up for your model rpm-wise WRT the electric is not going to be determined by your hover rpm; it' what you want to turn upstairs. Once you get the kV and gearing set to yield about 2K upstairs with reasonable headroom for the the governor, virtually any combo is going to run OK in hover within the suggested headspeed ranges. If you want a number to use for argument's sake on that model, go with 1600-1650.

Ben

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines
11-18-2009 10:40 PM
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MANCHA
Senior Heliman
Location: Cabo San Lucas, Baja- Mexico

My Posts This: Topic  Forum		PAPATANGO

my set up is:

normal: 1,630 rpm;
idle 1: 1850 rpm;
idle 2: 1950 rpm.

enjoy!

MANCHA
11-19-2009 01:28 AM
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papatango
Veteran
Location: Toronto, Ontario, Canada

My Posts This: Topic  Forum
11-19-2009 02:33 PM
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3 pages [ <<    <     1      2     ( 3 )    >    >> ]1517 viewsPOST REPLY
Boca Bearings . XHELI.COM . Autography FlightPower

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Aerobatic FAI F3C Contest > Vibe 90 SG for FAI setup
 
 
pinoy
Veteran
Location: Muncie, Indiana USA/Obando, Bulacan Philippines

My Posts This: Topic  Forum		Is there any other head dampener that you guys use on your SG? I had the one piece hard dampener then switched to the the two piece O-ring softer dampener that came with the kit. Is there an after market dampener that would works better or the stock works just fine? Oh BTW, really new to the FAI flying, this would be my first machine for it. Pinoy...


Heres my set-up;

Vibe SG 90
8717HV on swash and throtle
8900 on tail
Spartan gyro
Multigov governor
YS 91SR
hover RPM 1550
idle up 1 RPM 1900

Feel free to make any suggestions.
11-20-2009 12:45 AM
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3 pages [ <<    <     1      2     ( 3 )    >    >> ]1517 viewsPOST REPLY
Thunder Power RC . Mikado Modellhubschrauber . Futaba-RC

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Aerobatic FAI F3C Contest > Vibe 90 SG for FAI setup
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