A new rotor blade manufactured by design through Curtis Youngblood has arrived in the market place. Curtis Youngblood Enterprises now supply a fresh blade conception based upon years of practical flying experience and extensive model helicopter care.
At first glance the high quality finish is evident along a special care in packaging. One blade comes with anti chaffing tape at the root, mid span, and tip so that during shipment they will not rub together and mar the surface finish. They are enclosed in a plastic bag stored within a nicely crafted but attractive cardboard box. They ship with various spacers (8) in two thickness values for adaptation to common grip sizes. Also included are two metal bushings should you have 4mm blade bolts since they come standard for 5mm. It doesn’t get any better than this.
The construction is carbon epoxy with a foam core, pretty standard but high quality. The blade leading edge has a safety wire embedded running the full span. The feature is intended to contain the fractured blade parts should the unthinkable ground encounter occur. Unfortunately I have first hand experience with this and can vouch for the manner in which the broken blade parts stay tied together. This should one day become a standard with 90 sized machines, I hope.
The units are available in various lengths and we have evaluated the 690mm and 710mm lengths at 185g in both cases on the same R90-SE helicopter. The blade is also available in the popular 50 sized 600mm length. Both FAI and 3-D weights are available.
The blade root is 12mm and reinforced with substantial top and bottom doublers. The symmetrical chord is 64mm and at a maximum of 9mm thick measured approximately at the quarter chord location. The blade bolt center is just aft of this station by a few mm. The blades surprisingly run in a slight leading condition during flight. If one were to remove a pitch link after a flight the blades will feather towards a negative value. This is due to having a careful balance between the chordwise C of G, center of pressure and blade bolt positioning. I believe this combination is one of the key ingredients to making the blades perform as they do. My feeling is that finding the best exacting compromise of these factors comes more from experience and not a calculator. The tips are swept and designed with a unique white progressive pattern starting at 267mm from the blade bolt. I wonder if there is a subliminal message here? Curtis has his name embossed in the root end, to acknowledge why the blades fly the way they do, more on that later. The spanwise balance on our 710mm evaluation set is positioned at approximately 380mm (54%) from the blade bolt or 330mm from the tip.
As with all review blades they are carefully checked for a mass and c of g match. They require no adjustment being spot on. Often blades are corrected after the construction stage for final balance using small holes and plugs located at a vital point for weight placement. These blades use no such method due to a very strict quality control. From looking at the finish and general appearance, I’d have to say these are grade “A” blades. I could not find a single pinhole in the finish on the three sets I have. Sometimes blade suppliers will take the lower grade blades and hand match sets as closely as possible, this may be a cheaper way to go but with a lesser quality finish. Quality appearance is fine, but most important is flying qualities. I’d sooner fly a slightly blemished top performer that a problem laden piece of jewelry. Things we look very closely at are efficiency, handling and auto performance.
With some blades we trade off auto performance for cyclic rate by way of the rotor span. A blade good at auto hang time often is sluggish during flight exhibiting a lower maximum cyclic rate and a higher engine loading. We found that our earlier blades needed to be at 680mm for a 3-D rate but the Radix at 710mm felt about the same. Rotor bogging is similar but autos and power extraction from the engine are beneficial. Some blades bite hard suddenly with an abrupt over powering of the rotor, along with a large associated rotor droop. The Radix however will still bite hard but in a progressive manner leading to smoother and more consistent handling. The rotor is very predictable and powerful requiring less collective/cyclic management for those rather tasking maneuvers. Operation is also quiet and smooth. They also have the ability to generate ample lift at a very low rpm adding to auto hang time. This translates the extra auto energy into an additional pirouette or two, or in some cases a correction for a large piloting error! The following evaluation by Colin Bell pushes the test results to the limits.
During the first flight on the Radix blades I knew they were what I wanted to fly in the long run. First impressions were excellent due to the fact that they pulled as hard but bogged less and were just as quick as my previous set of smaller and lighter blades. I found them to be very smooth and stable making big, fast maneuvers easier but at the same time they were quick from center stick all the way over to full travel, thus providing a nice linear feel. When I started laying them into tight 3D maneuvers I noticed right away that the blade noise was reduced compared to other major brands. Cyclic hungry collective pumping maneuvers didn’t load the engine as much as your typical 710mm, 185gram blades. You would think with that being said there would be a trade off for auto performance, however no such thing was evident. Despite the weight of the blades they are still fairly easy to spool up in autos and don’t loose rotor rpm as quickly as you might think due to a high efficiency. I noticed that I hear more transmission noise from my heli because the blades are so much quieter. During tic-tocs one can actually hear the tail rotor gears load up as the gyro adds tail rotor pitch at each, which I have never noticed before. Overall I’m very impressed with the blades, they are exactly what I’ve been waiting for since the time I entered into serious aerobatic flight.
Carbon tail blades are also available from Curtis Youngblood Enterprises. These are CG corrected and very stiff. They are available 92 and 105mm lengths. The blade is very light reducing the hub stress, which translates into lower axial bearing loads. Coupled with an acceptable gyro-tail control system you can be assured they will not “blow-out” when used with a 50/60/90 helicopter. The T/R blades are foam filled, tapered, symmetrical chord and with a non-swept but enclosed tip. The taper is both in airfoil thickness and chord length. What all this means is that the tail rotor has a higher efficiency due to a more constant inflow velocity. The taper takes into account the different velocities at various points in the disk span. This is similar to blade twist but without any of the associated thrust reversal issues. The 105mm length blade has a mean average chord of 27mm. The bolt- hole is brass bushed for strength and the 5mm root end has grip reinforcements similar to the mains. Included are four 1.5mm thick spacers for other grip applications.
While it’s nice to see the Curtis name on the blades, you are not actually purchasing into a name, you are buying a true high-end blade performer at a very reasonable price. I’ve located retailing of $100 USD for the 710s mains through various merchants. Production was spooling up as of late August 2005. I highly recommend the Radix blade line to those pushing the flight envelope. If you have a chance to borrow some at the flying field for evaluation, don’t turn down the chance since flying is believing.