Optimum blades

[BeefBear]

When thinking about blades, somone somewhere must have an opinion about how blades are constructed and in doing so they must have taken into consideration the air density and weight to be lifted as part of the equation. Given that we tend to fly these things all over Australia, is it possible that certain blades will perform better geographicilly due to the differences in the normal air density we find ourselves in throughout the year?

Ted

[bones]

Ted i understand where your coming from on this one thou,,,,, it could end up in one of those (dare i say it) down wind turn subjects.
On my old gyro, it has 25' McCutheons, and it flys bloody good with them too, with the tacho it showed about 335 rrpm straight and level, now a little while ago some tyre kicker said he was interested in buying it, but hte problem was he was told he would need 26' rotors, so on one of my trips to Hoody's i swapped rotors with him to try it for myself, his were 26' allu, now being longer rotors they should have spun slower, instead they were 360 straight and level, which goes to prove that my rotors even though they were shorter were much more effective, which didnt surprise me since the machine used to be a tandem machine, with the same rotors..
So you could chase this all over and still not have an answer, and one other thing, even two sets of rotors of the same maker MAY behave differently, just as two R22 helis can fly very differently ect ect...

[russ]

We as the pilot, have little input re blades.............as the maker has preselected his aerofoil section, generally there is about 3..4 aerofoils in the market. But each maker has his preselected one, and THAT is it. Then the maker has predetermined HIS determined angle of attack to set into his blades. However some makers can slightly increase or reduce that setting prior sending them to you. This can be achieved with discussion with YOU, as what you want your machine to be doing. Now the next is the overall "disk" size..........this too, can be achieved to suit YOUR application.

Each aerofoil shape has it's own performance, and then also there is the posible downside to that aero section.................throw in pitch,disc size.............machine weight,application etc......and it's becoming a more complex issue..............but quite achievable to sort

[BeefBear]

Okay, let me see if this right;

Cross country blades should be longer rather than shorter

Mustering blades are higher energy than cruising blades

Ted

[russ]

To say yes to both of these..................gives you the negative issues that come into play, with the affirmative answer

To say no to both of these..................again some negative issues have to be addressed with this decision

Every action has a reaction

I do know of one blade maker here in Oz, that is experimenting with a "twisted,tapered" profiled blade. Am hearing it's the bees knees for ALL applications

Rotorblades are trickey little DEVILS

[Aussie_Paul]

Russell, I flew the first Revolution twisted, tapered, thinning, and with a high performance VR-7 helicopter airfoil section for the last 4 feet. Rob and I had been discussing the requirements for my lead sled machines, i.e. MTOW 600 kg. We were trying to improve the 2 blades system. Why? Because up until then everyone just added to the diameter. Finally a point is reached where the camels back is broken and the rotor shake is too severe.

Rob though t and I agreed that if we could improve the 2 bladed systems it would be great as we did not want to have to go to a 3 bladed system!!!!

These first blades saved me 400 engine rpm and performed spectacular, BUT we lost stability compared to Robs original 8H12 blades. I sent them back to Rob and he warmed them up a little and add3ed some reflex to the VR-7 airfoil. That improved stability a little. I then add3ed large trim tabs approx 2' from the tip with approx. 5 degrees of "up" at the trailing edge setting. This improved stabi9lity again by a very small about. I loved those blades as the trill did not seem to change much at all between 30 and 80 kts. A mustereres dream blade, but no good for me to sell with Firebird to inexperienced gyro pilots!!!!

Next Rob sent me the same blades without a change in the airfoil for the last 4'. We lost 200 engine rpm BUT we were still 200 engine rpm in front of the originals, and had enough stability back that I was happy!!!! These are the blades that Rob now supplies.

At this time, when I rang him to start talking rotor blades for Firebird, Rob had never made blades longer than 26'. Originally Rob supplied me with a longer hub bar to bring the diameter up to 29'. The Raf used 30' and Hybrid was 48kg lighter than a Raf, so I was happy with 29'. Boy the 8H12 airfoil, same as McCuchen, but balanced at the 25% point instead of the McCuchen 30+% point were the most stable, AND SMOOTH, blades that I had flown.

I really enjoyed experimenting with Rob’s blades, and Rob’s expertise. I think that Rob now has the best understanding of anyone re rotor blades in Oz.

I hope that this story gives people some idea of what actually goes into rotor blade design. I believe that I was a good tester for Rob, as I was picky re stability and performance due to developing Firebird. People who only test their own stuff can easily talk themselves into a positive!!!!

I have tested so many rotor blades, will pick the best composite, and the best alloy blades to be certified on Firebird, that gives people choice.

Aussie Paul. :mrhappy

[bones]

Paul,
The McCutheon and now that i have a set of Rob's blades are veery good units, but as to compare the difference, i havent had to chance yet, though a couple of months down the track i will try the red blades on my new machine, to see if i can feel any difference, even though the red ones are 2' shorter i not sure the difference will be that great.
One thing that i'm not terribly impressed about the Patroney blades, and i will ring him about them one day is the rotor noise, i just cant seem to load them up enough to get them really thumping the air, a little while ago while we were out at Hoody's, Ted from the Isa was down with his machine, he had 26' AK's, one time when i was on the ground Ted banked it onto the strip, and holy heck those blades let us know when he was turning.
That is just from a mustering point of view, the more rotor noise you can get the easier the job is to do..
Good to see that your testing things for Rob though Paul keep it up, doesnt surprise me none though, us Qlders are pretty bloody good you know.. :joy: