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HomeScaleAircraftScale HeliScale Helicopter Main Discussion › Use a FBL system on a 4 bladed head or not?
05-29-2012 04:18 AM  6 years agoPost 1
Skytrek

rrApprentice

Suffolk, Va

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Hi guys, I'm almost finished with a 90 size BO-105 and have decided to go with a four bladed head. I know this question comes up from time to time and I have read lots of post on the topic. However, I'm still on the fence concerning a the use of a FBL system. This is not an issue of $$ or not understanding how a FBL system works,,,,I have a pod and boom utilizing a CGY 750. I'm wondering if a four bladed head can be setup to fly without it and still be enjoyable to fly?

Barry London

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05-29-2012 05:27 AM  6 years agoPost 2
Mojave

rrElite Veteran

Palos Verdes, Ca. USA

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I hear that it can be done, but I'm spoiled. I really like the vbar FBL system on all of my helis. It makes flying more fun for me. Electronic swash phasing is super simple, the links are vertical and the head geometry is correct VS links layed over when the head is mechanically phased. The heli is easier to handle in a strong wind also. JMHO and .0002
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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05-29-2012 09:46 AM  6 years agoPost 3
darrens

rrKey Veteran

United Kingdom

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It is dependant on the specific flight dynamics of each individual machine. Just some of the things which dictate whether or not a helicopter is stable in flight and whether it needs a FBL system are;

Rotating Mass

The heavier your blades, the harder it is for them to deviate from their track, the more stable your helicopter

Headspeed

The higher the headspeed, the greater the effective weight/centrifuge/enertia, the harder it is for them to deviate from their track, the more stable your helicopter is.

Damping

Head damping is more compliant than a fully rigid head.

Blade Tortional Rigidity, rigid blades are less forgiving while flexible blades are more compliant and have a damping effect.

Helicopter Mass

The heavier the machine, the easier it is for the weight to destabilise the head....think pendulum/lever effect

C of G High/Low

Excluding Fore/Aft C of G, this is whether the mass of the helicopter sits high or low as the lower it is, the lower the effective leverage on the main shaft (the lever). Lower weight equals less stability.

Conclusion

If you have a machine which has light blades, slow headspeed, no damping, rigid blades, is heavy and with the weight sitting low, then those dynamics will ensure it is a handful to fly even with stabilisation.....no matter how skilled you are on the sticks or how good a FBL unit you choose.

Of course, if you have a multi blade machine with more positive flight dynamics, then it is entirely possible that it is comfortable to fly by any pilot with even moderate skills. It's also possible that even without stabilisation, it is more comfortable to fly than the stabilised machine with negative flight dynamics. Ultimately, you can best guess where yours will sit but you will not know until that first flight

He who dies with the most toys is the winner!

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05-29-2012 11:32 AM  6 years agoPost 4
Richard Morgan

rrApprentice

Virginia Beach, Virginia USA

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Barry:

In a word "yes". Suffice to say we all have our favorite system. For me, I recommend the Skookum 720 with the power bus. Easy setup and it works. You will swear you are flying a flybarred head with more stability. Plus, I believe there are some neat add ons for the system in the pipe. "Darrens" is correct in his explanation, but with your set up on the BO-105 you will be just fine. Give me a call, I may have a set of Vario blades that will work for you as well. Keep up the good work.

Richard

Richard

Is it just me, I thought all Helicopters flew in 3D......Hmmmm?

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05-29-2012 12:31 PM  6 years agoPost 5
Heli143

rrElite Veteran

Phenix City, Alabama

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Barry,
first of all, yes, it can be done without a FBL system as Copterdoctor set up my five bladed head without a system and flew it around very nicely on a windy day. but he is much more experienced.
Now this is my first multi blade heli and when I pulled it into a hover it felt like it still had the flybar on it.
However, as Mojave said, things change with a wind blowing and I haven't tried that yet
I am going to purchase the Spektrum 7200BX to use on my 407 with four bladed head then I am covered

Roy Mayoral

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05-29-2012 02:17 PM  6 years agoPost 6
doorman

rrProfessor

Sherwood, Arkansas

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Spektrum 7200BX
I would agree with all of the info you have recieved so far.. and I have flown both ways..with and without.. I usually do a mechanical set up first and do a test hop just to see how things are going to work, and I have a couple of those that I kept that way.. it is a bit of a different feel, but nothing really terrible...
But, in the end, just to make sure I will not be grounded at a fun fly because of wind, I end up putting a stabi system on it...and the BX has been my prefered system so far because I can dial it down enough, even with low HS enough so that it doesn't feel like it is trying to control the heli.. I hate having to fight gyros!!!!
Have fun, is the bottom line, and the final choice will ultimatly have to made by you... Good Luck, Stan

Note from the manual:
You can also use any swashplate geometry by
selecting User Defined (PC software required). So, you will need that optional cable to set the phasing for the head...

AMA 2918-Team Spin Blades,,Castle Creations, Unique Aircraft

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05-29-2012 09:22 PM  6 years agoPost 7
Joel Rosenzweig

rrVeteran

Marlborough, MA - USA

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Barry,

Try it without stabilization so you can see how it feels without it. Then try it with the stabilization system of your choice and see if you like it better.

I've flown the multi-bladed setups with and without stabilization and have never found the stabilized version to be worse. Everything I build now has a flight stabilizer inside of it. They are that good.

Joel

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05-29-2012 10:38 PM  6 years agoPost 8
Skytrek

rrApprentice

Suffolk, Va

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First let me say thanks to all who posted! What a wealth of knowledge and experience! More reason I love this hobby!

What I'm getting from the info is this;

You can set up a heli to fly without a FBL system and enjoy the experience. However, there are so many variables to get correct....a novice may crunch a nice scale before getting to enjoy anything. Also, a nasty gust of wind may change the experience from good to bad..... rapidly.

However, there's nothing wrong with going without a FBL system to experience the feel and ensure the best proper set up. I may decide I like it but this would greatly depend on my flying skills and not recommended for a beginner pilot. Most scale flyer's have gone with a system for insurance and ease of use and setup. Many quality systems have adjustments to remove the artificial feel.

What I have decided to do;
Purchase a FBL system but do the first few test hovers without. This way I know the mechanical setup is correct and the FBL system wont over work my servos. Once happy I'll install the system and enjoy with piece of mind. Thinking I'll go with a Skookum or another 750.

That's where I came down any other thoughts appreciated or please let me know if I'm way off base!!! Thanks again!

Barry London

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