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Old Jun 29, 2012, 04:12 AM
Hamburger
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head speed for 4-blade 450?

Hi,
what would be a good head speed for a 4 bladed 450 size FBL CP heli, please?
It will be used for gentle scale like flying only.

Just to keep things in perspective and making comparison easier, what would be the corresponding recommendation for a 2 bladed 450 size FBL CP heli for that same flying style?

Thanks.
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Old Jul 02, 2012, 10:27 AM
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On my stock Trex 450 with Black Angel 4-bladed head, I've run head speeds down around 1800 RPM. I run a little higher head speed on my Cheyenne owing to the heavier weight.

Here's a clip of the 4-bladed Trex flying:

NEAT Fair 2010 - 4 Blade Helicopter - Trex 450 (1 min 15 sec)


This is a very pleasant machine to fly.

Jim
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Old Jul 02, 2012, 03:39 PM
Hamburger
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Thanks. Ghat would be quite lower than most 2 blade headspeeds.
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Old Jul 05, 2012, 12:36 PM
kin
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I recommend the 4 blades same Jim 1800 +/- 50-80 rpm , it is a very good range . 3 blades possible 1900 and 5 blades you should down to 1600-1650 rpm . but 5 blades you need to add the tail respon and add tail blades length at lead 5-8mm longer .and more blades the width of the blades need more narrow . don't make the motor over load and high load for the blades (wide blades ) .it is not good for muti blades head . bad look and bad over load ! so you can find a narrow blades .let the total blades loading not too big different . otherwise you ned update your full power system . the cost is a lot higher than you buy a new set narrow blades from smartmodel ! Ha !Ha! not hard sell here . but it is true !
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Old Jul 07, 2012, 01:08 AM
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Yep... you want skinny, low drag blades and a lower head speed. If you can't easily get narrow-chord blades, at least find some thin 3d blades with concave surfaces near the trailing edge... this will reduce the load on your swash servos a lot.
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Old Jul 07, 2012, 09:00 AM
Hamburger
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Ok got it.
Is 315mm blade length gonna help (instead of 325)?
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Old Jul 07, 2012, 12:48 PM
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1800 is perfect. i run 2000 on 2 blades but they are spinblades asymetrical blades so they have alot of lift and a very wide chord. i have a md530 fuse so its a tad heavy. i had a 5 blade head and ran 1800 or so and it was great. had the tail figured out too but due to a blade strike and the head had issues and no parts from rcaerodyne available (oh yeah we will have them in a month, heard that 3 times) i gave up on it.
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Old Jul 12, 2012, 04:52 PM
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ok, I will try and get shorter/narrower blades. Headspeed shall be set to 1800.
Thanks everybody.
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Old Aug 17, 2012, 04:31 AM
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I have the 4-blade working with 1850 and regular symmetrical 325mm blades. Thanks everybody!

Not sure if I should get the special narrower blades for a 4-bladed head? The set costs about 100$ and I do not care for the looks. So does the heli fly better / differrently with those narrower blades - if so, how? I am only interested in smooth park flying atm.
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Old Aug 19, 2012, 10:17 AM
Redjestird Youser
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Quote:
Originally Posted by hamburger View Post
I have the 4-blade working with 1850 and regular symmetrical 325mm blades. Thanks everybody!

Not sure if I should get the special narrower blades for a 4-bladed head? The set costs about 100$ and I do not care for the looks. So does the heli fly better / differrently with those narrower blades - if so, how? I am only interested in smooth park flying atm.
Which narrower blades? The Heliartist CF scale blades? I think that's what you are speaking of as the price is stratospheric, so here's some video of those...



450 Hughes 500C (2 min 56 sec)



I have these at 1800 rpm, and I did notice that lift is somewhat reduced. Cyclic response is lesser I'm thinking...which can mess with your FBL system also if it expecting a certain level of cyclic response, depending on what system you are running. On my MiniVbar, I have the gain maxed out for best flight manners. I do like the way it flys...so I'll call them good
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Old Aug 22, 2012, 02:26 AM
Hamburger
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Originally Posted by SidewaysLS4 View Post
Which narrower blades? The Heliartist CF scale blades? I think that's what you are speaking of as the price is stratospheric, so here's some video of those...
I meant Spinblades http://www.der-schweighofer.at/artik...sch_spinblades going at 70Euros (plus shipping).

your heli in the video looks real nice.
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Old Aug 22, 2012, 09:49 AM
Redjestird Youser
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Well, they are known to make nice blades. Any idea how wide those are? I didnt see a measurement that I could see on that site
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Old Aug 25, 2012, 03:21 AM
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no, sorry. I guess you could look that up @spinblades?
For the time being I consider those too pricy for my taste.
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Old Dec 21, 2012, 05:28 AM
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Quote:
I have the 4-blade working with 1850 and regular symmetrical 325mm blades.
In the meantime I increased head speed to about 2000 for better tail stability and love flying that combo. I got the homebuilt fbl controller dialed in well enough for now. All I do is mild park flying.

It has gotten me curious as to what pitch range is recommended/typical for a 4-bladed head?

For now I have a pitch curve that resembles [-3, -3, 0, 8, 15] degrees pitch. Throttle is [0-50-70-82-95]. The effective pitch may be lower due to the non-locked phasing of the head; I get a 10 to 20 degrees rotational freedom of the head vs. swash (and yes, the anti-rotation collar is fixed to main shaft). Upon throttling up it results in a fairly recognizable bump when blades jump from negative to positive pitch - possibly again due to the non-locked phasing.

So this boils down to me having a couple questions:
1 - what is your pitch range (in degrees) for a 4-bladed head?
2 - with a multi-blade head do you limit yourselves to the upper half of the throttle/pitch stick range on your tx for positive pitch or do forsake negative pitch altogether and use a setup (mechanically and in tx) which uses more of the throttle stick range and servo travel to get finer control?
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Old Dec 21, 2012, 02:19 PM
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For scale flying, you should set a pitch range of -2 till +9 or similar, more or less like you would for any scaler... It is adviseable, to set-up mechanics such, that you utilize as much as possible of the practical servo throw for your collective range.
Maybe your FBL system prevents you from doing that. In that case, it is your choice whether you learn to fly manually and set up the helicopter as perfect as practically possible, or use FBL, and necessitate a less perfect mechanical set-up and set higher demands to the swash servo's.

It is VERY adviseable to remedy that rotational freedom between swash and head, it might someday come and surprise you....

I fly a BO105 and an EC 135, both with a Copter-X fully rigid 4 bladed head.
Blades are Spinblades semisymetric 350 mm, running at 2000 RPM. Both are flown manually without any electronic stabilisation, other than a rate gyro on the tail.
The EC135 uses a separately driven electric tail fan. It weighs 1100 grammes and gets a safe 9 minutes out of a 2600 mAh pack.
EC135Bert1.wmv (3 min 44 sec)

The BO105 weighs in at 1250 grammes, and uses MCPX blades on the tail, shortened to 62mm (2.5"). It gets over 8 minutes out of the same batterysize
Bert 450.wmv (4 min 4 sec)


Brgds, Bert
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