Difference between Blades for FB and FBL - HeliFreak
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Old 05-24-2010, 11:51 AM   #1 (permalink)
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Default Difference between Blades for FB and FBL

I would like to know which is the difference between those blades for FB flight and those for FBL flight
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Old 05-24-2010, 07:38 PM   #2 (permalink)
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Default Interesting place to post this question...

but I'll be happy to give you my take/experience over the past 2 seasons with FBL.

There's a couple of things to keep in mind about FlyBarLess (FBL) model helis.

1. With the flybar removed, you can expect a HUGE increase in cyclic rate - even at the same cyclic pitch deflection - pure physics - you've reduced the amount of mass and gyroscopic forces in the rotor system by removing the flybar & paddles.

2. The cyclic as a whole now borders on the side of "unstable". In certain circles, the word 'unstable' reads as "now extremely agile".

3. Strong blades! The forces applied to the blades on a FBL heli can be greater than those of a flybarred (FB) heli.
The heli will be faster in FFF and you'll have much greater cyclic rate to flip & roll - AKA higher G's.

4. With FBL relative to FB - you'll have less rotating mass AKA Inertia; Autorotations may need to be a bit more carefully managed - if running a relatively "light weight" set of blades.

With the above in mind...

A very stiff CF blade is pretty much par for the "menu" amongst manufacturers offering FBL blades.

These blades are usually a tad bit heavier than their 3D counter-parts.
The blade weights/CG are moved outward to help in both stability and inertial aspects.

Most FBL blades will be very "neutral" in the chord-wise CG.
Hang a blade from a nail, hang a weighted string on the end of that nail.
Once everything has settled - note the relative blade position to the string.
Blades that "hang" with the string running straight-down the blade from the bolt hole are said to be "neutral"...good general purpose blade - Sport, 3D, FAI & FBL.
Blades that lean backwards - less leading edge in-front-of the string - are "relaxed" (even more stable) - like a beginners/sport blade.
Blades that lean forward - more leading edge in-front-of the string - are "aggressive" - 3D blade.

In a nutshell - STIFF, Neutral Chord CG, Outer span CG (AKA FAI style blade).

Give you a real world example of 2 different RotorTech 600mm-Class blades on my vBar4.0 setup on a Pantera:

RT610 - 610mm in length: known as a good,snappy 3D blade - has a neutral chord CG, inner span-wise CG relative to the RT600 and light - 129g.

The RT610 is a WILD, UNTAMED ANIMAL! I can lower the rates within the vBar software and get pretty predictable flight charateristics - but hard for me to manage and keep REALLY SMOOTH - as I prefer smooth flying models over "herky-jerky" setups.

RT600 - 600mm in length: known as a good FAI and Sport blade - again neutral chord CG, outer span-wise CG relative to the RT610 ~1" and a weight of 140g.

These blades are plenty "quick" in the cyclic rate - but are much smoother and predictable for my flying skill-set. Auto pretty well too - but not much "hang-time" at the end.

Hope this helps to get you started in the correct direction on your FBL intentions.
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Old 05-25-2010, 01:14 PM   #3 (permalink)
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Like all ways, your knowlege is apreciated. I'm not the intention to flight in FBL mode because I'm totally newbie. But just want to know something additional about the hobby in wich I hope belongs.

I recently bought a P50. She still in the box, waiting more economic content to the budget asigned in order to purchase all the gear and tools, but, you know this is a slowly process (specially if you are married and with 2 childrens and a teen jaja).
So thank you very much for your answer.

Saludos.
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Old 05-25-2010, 06:25 PM   #4 (permalink)
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Quote:
Originally Posted by salamandras View Post
waiting more economic content to the budget asigned in order to purchase all the gear and tools, but, you know this is a slowly process
I think about 95% of us are in the same boat, or have been!
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Old 05-25-2010, 07:49 PM   #5 (permalink)
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i love this forum it's like going to school every evening,so much knowledge to soak up
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