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| Please rate the Align CF Blades : | |||||||||||||||||||||||||||||||||||||||
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| Align have released some carbon fiber blades. The details are as follows : Shape : symmetrical Length : 325mm Width : 32mm Weight : 54g / set |
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| Studying these blades closely reveals that they are not solid carbon fiber.
Under the red taping on the underside of the blade are cutouts. Making
the blade hollow for part of it's length which is covered by the tape. Just flexing the blade reveals that it is quite stiff and will provide a more stable aerofoil than the stock woodies supplied in the kit. The blade is also a fair bit heavier than the stock blades, so theoretically should provide some more stability. |
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| First task was to balance the blades, I had read that others had bought two or three sets of these blades in order to get a good matched pair. This was not the case with my single set. The lengthwise and chordwise center of gravity was spot on in terms of matching of the blades. Placing on the blade balance provided the following result .... | |||||||||||||||||||||||||||||||||||||||
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| The addition of one of the pieces of supplied tracking tape to the lengthwise
Cog yielded a perfect balance. Given how little the tracking tape weighs I would say that these blades were about as close as you are going to get in terms of matching weight and CofG. General fit and finish of the blades is very good and the colourful scheme used will look good in the air, except if you spend a lot of time inverted, in which case you will be seeing a mostly black rotor disk. I would have much preferred if the underside of the blades was bright yellow as well, particularly as a black rotor disk tends to just disappear and not aid orientation in flight. The last thing to comment upon is the blade tip. I'm not sure what advantage the blade tip shaping gives but it is certainly unusual.... |
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| Overall the blades are well made (if a bit plastic looking) and my set
were certainly well matched for weight and CofG. The price is the usual
rock bottom Align price, so they are going to be hard to beat for value. It should be noted that due to the length of these blades (325mm) they should not be run with the stock boom as a tail rotor strike is highly likely. Personally I will be running with the stretch boom to test the flight characteristics of these blades. If you do wish to run these blades with the stock boom then it is possible to cut the blades down slightly to accommodate. It remains to be seen how these blades will affect amp draw compared to their 315mm wood brothers and I will be testing this to see what differences there are. Given the profile of these blades (symmetrical) it is clear that Align are looking to grab some attention with the T-Rex's 3D capability. The bench test of these blades showed a substantial rise in the amps required to drive the rotor disc. Previous full power runs with the Mega 16/15/3 had not peaked over 20 amps, the carbon blades pushed way beyond this with a full power peak of 26 amps. Clearly the larger and heavier blades will affect flight times negatively but hopefully provide a more blistering performance. The flight tests will tell. Initial Flight Testing Having only just rebuilt the T-Rex I was in two minds as to whether to make the first spool up after rebuild with the new CF blades. Particularly as I had replaced a good number of the control linkages, the gyro and the tail servo as part of the rebuild. The first thing was to do an initial spool up to near hover revs and check the tracking. I had only done the blade pitches by eye so there was a good chance it would be out by some margin. Initial spool up showed no adverse vibration and in fact the whole machine seemed to be much smoother whilst coming up to hover revs than with the previous wood blades. I stopped just short of lift off and gave a quick bend to the knee to check tracking, I was pleasantly surprised to see both blades in perfect track. Considering it needed a little work to do to get the wood blades to track this was a good sign. Conditions for hovering were very much less than ideal. My test hop was outside my house and the wind tends to swirl and gust in multiple directions. Add to this that the wind was approx 15-20mph and the T-Rex definitely has potential to give you a bristling of hair to the back of the neck. Before I could contemplate this further a gust lifted the machine to chest height, so no backing down now. After a brief fight for control the T-Rex settled into a solid hover, control response on the collective felt crisp and it didn't take more than a click or so to induce a steady but brisk climb. Throttling back produced a predictable response and somewhat more refined than the wood blades, I think the extra weight of the carbon fiber blades allowing a smoother and slower loss of headspeed from the reduced throttle. Unfortunately weather conditions were worsening and flight was becoming more of a fight for control than anything else. I decided to cut it short there and wait for fairer weather to do a proper aerobatic and performance test of the blades. Initial thoughts from the test hop were that it was certainly smoother in the hover but I'm left wondering if the heavier blades will affect the superb roll rate I had previously enjoyed with the wood blades. With winds predicted to be under 7mph for the next three days I should get some opportunity to explore further very shortly. Standard Flight Testing I managed to get some flight time in today with some gentle circuits and some exploration of the climbout potential on these new blades. Firstly having had no tracking issues on the initial hop it was immediately apparent that there were going to be tracking problems for more serious flight. I had a real battle trying to get these blades to track properly. They will track perfectly just before take off but add some power and they steadily and progressively go further out of track the more power that is provided. Certainly in full power climbouts I could see a 1-2 inch difference in the tracking and some vibration as a consequence. This is more than a little disappointing as the blade performance is superb. Climbout on these blades is close to double that of the stock woodies. The tracking issue is most certainly a symptom related to these blades as I'm not getting the same problem with any of my wood blades. Aside from the tracking issues the blades performed predictably through forward flight and circuits. The machine holding it's heading well and generally having a less meandering feel to it's progress through the air. Next step is to check the aerobatic potential but before doing this I need to find some cure to the intensely annoying tracking issues. After some more investigation I think this is all to do with the weight of the blades and the damping in the stock head. Given the extra weight I don't think the stock dampers are sufficient to keep these blades in track. So possible solutions are now on my mind. I'm going to try two different solutions. Firstly Align have released a new headblock with (surprise, surprise) double dampeners, this should stiffen things up nicely and is most certainly recognition of the tracking problems being experienced by many people. Secondly I saw a nice mod utilizing fuel tubing for the damper and using brass blade root bushings (from the stock wood blades) on the feathering spindle instead of the plastic ones. I will get to try the second of these later this week but the first one will be a couple of weeks as Align have only just released the new headblock. I installed some new fuel tubing dampers to the head tonight and used brass blade root bushings instead of the plastic inserts to squash the dampers and firm the head. Initial tests showed a marked improvement in tracking but there is still some variance in the tracking at 0 degrees pitch. I'm working on how to firm this up further but at this point I would say I can run the flight tests on the Align blades as tracking is now within acceptable limits. It will be interesting to see if the new Align headblock has similar or better results. Update 06/03/2005 I now have the Align blades tracking perfectly. The fix turned out to be a number of different elements combined. Firstly the dampers needed stiffening and this was achieved using fuel tubing as the dampener and replacing the plastic feathering spindle bushes with the brass bushes from Align main blades. Secondly I installed the MicroHeli washout arms, which got me to a position of the blades being almost but not quite tracking perfectly. Last upgrade was the MicroHeli flybar set and the whole thing now tracks perfectly. I'm not suggesting that everybody goes and buys these upgrades to get perfect tracking, the point is that the tracking appears to be dependent on removing the slop from the washout and flybar arms. Now I can get on with testing these blades properly without getting bad vibrations upsetting the gyro. Once the new Align rotor hub arrives I'll test that as well to make sure it is just as effective as the fuel tubing dampeners. Update 17/03/2005 I have tested the new Align Rotor Hub and the results can be found here. The clear result of these tests is that these blades are not responsible for the bad tracking experienced and that the stock flybar mixers and hub are in fact most responsible for the bad tracking issues. This solved I can now get on with the task of testing these blades performance properly. I have now had opportunity to fly these blades for fast circuits, approaches and climbouts. Now the tracking is sorted I can appreciate what a nice performance these blades are capable of delivering. Climbout is fantastic (as I already stated). Hovering is very stable due to the relatively heavy weight of the blades and this also translates into more predictable and less twitchy forward flight characteristics. These blades certainly make the T-Rex a more comfortable heli to fly around and I have found my self less 'on edge' whilst flying with these blades. I have yet to try the aerobatic potential, this is next on my agenda. My expectation is that the roll rate will be lower due to the heavier rotor disc. Update 25/03/2005 I have now done loops rolls and inverted flight with these blades and had opportunity to get a real feel for their capability. The flight characteristics are very much a compromise. The blades are heavy which makes the roll rate slower, this means that 3D performance is somewhat less punchy than with lighter wood or carbon blades. For a beginner doing sport flying they are ideal as the machine feels much more solid in flight, less twitchy and less aileron/elevator sensitive. These are all the positives and unfortunately there are an equal number of negatives. Despite all the work to tighten the head on the T-Rex I still can't get them to track perfectly and they still go out of track in flight, which is most annoying. Secondly despite being balanced perfectly and having identical center of gravity these blades cause my whole machine to shake, which in a small part is the tracking but the shaking is more than just tracking would create alone. I haven't managed to identify what causes this as just changing blades fixes the problem. Today I fitted the SAB 320mm blades which are almost as heavy as the Align blades and experienced none of this bad vibration. I'm stumped as to the cause but it certainly isn't imbalance in the rest of the head as all other blades work perfectly, even ones of similar weight and length. Conclusion If it wasn't for the vibration and tracking issues I would recommend these blades highly as they have great power and stable flight characteristics, however for the 3D purist they are probably a bit slow. These blades do demand a lot more from the motor and amp draws are higher, so a good pack and powerful motor are a necessity to run them. It maybe be something unique to my set of blades that is causing the vibration and tracking issues but having had them on the head balance several times I can't find a cause or remedy. Due to this I can't recommend these blades at this point in time as the vibration upsets both the gyro and the heli flight characteristics in general. I will actively look to try another set to see if I get similar problems but for the moment this is my conclusion based on the review set of blades. |
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