Going from 325 to 360, do your servos have enough torque to counteract the extra surface area and rotating mass? Though an extra 35mm of blade may not seem like much, being at the outer end of the blade, the velosity multiplies the effect of the extra 35mm surface area and mass exponentially to some degree, putting more load on servos. I may be reaching here, but it seems logical.

 

FFF: to my understanding, higher head speed and/or heavier blades will make for more stability in FFF, but maneuverability suffers from the added rotating mass creating more gyroscopic force, again loading up your servos. Apparently there is some compromise involved in balancing between speed and agility.

 

I use TGY 306G servos in all of my 450s. People use them on Gaui X3 with 360mm blades. Stretched 450 is lighter than X3. I do not think servos are too weak.

 

I was able to flip my Align 600 EFL PRO very fast. Definitely much faster than stretched 450 to 360mm blades.

That is why I suspect airfoil of blades is crucial. My 360mm blades are much thicker than 325 and 335m blades. It creates more lift at low RPM but can create problems (expotential aerodynamic friction) at higher RPMs.

I already ordered tougher Tarot DFC heads for 450s. Just to see the differemnce in behaviour at differen RPMs. V2 of those heads has stronger feathering shaft so it is recommended for 360mm or 380mm blades.

 

Now that I've actually had a chance to watch the videos...... Dissymmetry of lift phenomenon, yes. Gyroscopic precession, not so much. Precession seems to apply to my 120sr with the 45° mixing flybar where the swash precedes rotor by 45°. The little Nano, with it's FBL head, different story. Swash plate is in direct phase with main rotor. If It's set to pitch forward, the swash is a direct forward tilt. So in this case, whatever precession there is- only that the forward pitch sweep actually begins 90° before and ends 90° after, but full forward pitch of the blades (more in rear/less in front) is still directly oriented to swashplate and cyclic stick. I could be splitting hairs here, but either something doesn't add-up, or I have answered my own question.

 

Torque-induced precession (gyroscopic precession) is universal fact of physics.

Lets refrain from discussing:

• Thomas precession
• de Sitter precession
• Lense–Thirring precession

 

I agree, lets leave astrophysics out of the discussion. I get the principle, but while gyroscopes and bicycle wheels are good for demonstrating gyroscopic precession, they overemphasize the effect for the purpose of helicopter rotors. Our rotors have proportionally minimal gyroscopic force compared to an actual gyroscope or bicycle wheel because the mass of a rotor is not concentrated at the outside of the disk. Obviously mass is a factor, a 2 blade rotor will have less gyroscopic force on it and have a more agile cyclic response than a big 5 blade rotor. It just seemed as though the gyroscopic precession was a bit overemphasized where helicopter rotors are concerned.

 

@Beaver

Please check how swash plate is moving blades when they are perpendicular and prallel to the boom.

Every swash plate works like that!

Every CP heli controls are based on 90 degrees phase lag. There are no exceptions.

Look at three blades head:


There is 90 degrees lag embedded in design.

 

Damn. Didn't see the forest for the trees. The 90° is built into the head by the links and bellcranks of the grips being 90° ahead of the blades. I manually rolled the swash full forward and checked pitch..... full pitch on right side and not rear. I digress.

 

good question and you have some notion of the answer already. A thicker foil will require the flat of the foil to rotate more to become active in pitch moments, so therefore they will seem slower in response. Up the agility setting and even add positive expo to compensate, try it. I like the question and reviewed the post for awhile before replying now, do you guys think this is an accurate assessment of the matter?

 

Not sure. A thicker foil means greater surface area for the air to flow over. I imagine this would have the result of creating more lift at the expense of more drag. So i would have thought that this would have created more response. I am not an aerodynamics expert however. Its only my opinion. Can anyone else shed more light on this?

 

I could be wrong, but a thicker airfoil would also be inherently heavier and create more rotating mass, and therefore slower response. It seems like a better option would be a wider blade instead of thicker. The added surface area would displace more air and have better response provided the heli has enough power to handle the extra pitch induced drag and avoid rotor stall.
Did I get that right?

 

ok, I'm redesigning blades and know a lot about foil and chord, different dynamics and through many observations later have seen a thicker wider foil work better than a narrow thin one in low rpm. The fatter blade did not drag either, I know that to achieve lift and pitch the flat rear portion of the foil must be level or greater, and as you rotate the fatter blade it will require more pitch to begin adding pitching angle. This is a good lesson because full scale blades and plank prop blades are twisted to maximize pitch evenly. My work has involved many variations and observations regarding points of breakage (lol). The best aspect ratio for low speed is around 20:1 like gliders have (2ft by 40ft) where-as an aspect of 10:1 is typical on rc helis , 700mmx70mm, 325mmx31mm and so on. I've made up a 550mmx70mm which were very good all around having an aspect ratio of about 8.6 to 1 and were thick in foil. An average of 1/15th the width seems to be the rule for rc heli blades thickness. Problem is (one I've solved in my designs) is that different parts of the blade are traveling at different speeds.

Here's the thing, can a blade create lift if the upper side is pitched heavily but the horizontal plane of the bottom is not true horizontal or greater in pitch? If you ever get a set of asymmetrical blades you actually need one degree of bottom pitch to get lift while you have to spool up in negative pit by 3 or 4 degrees so the heli doesn't get light on the skids, most of the work is done by the airflow above the blade but it still needs to be directed downward and back, first to lift and then to pitch with increase aoa. If air on the bottom of the blade starts going upward into the lift airflow of the upper blade surface it is negating the positive lift airflow.

Cheaper hk blades have a flat 5mm or more seam at the trailing edge of the foil on a 325 set. If you want to narrow a set you can sand the seam off about 3mm max and see what happens, narrow is better in multi blade heads. A lot of times the trailing edge is one square router'd edge, if you sand that to a slightly sharp trailing edge it can improve performance by lowering drag (just knock down the hard edges at a 45° angle). Too much of that machined edge and the blade will need more pitch to work properly as air is leaving the blade surfaces. High quality blades have an even trailing edge foil and very little machined trailing edge, though they disintegrate easily too since there's not much material and glue there that's holding the upper and lower surfaces together..

 

So what would be the characteristics of a heli blade that would provide the following...

1)Maximum 'POP' with minimum drag
2)Fast roll rate:
3)High level of control
4)Resonable speed

Just curious - i would love the ultimate smak blade

 

Cyclones @smakmeharder , tick all the boxes you have there