Weight,Power,Prop,& Rotorblades

For the pix above:
http://www.asra.org.au/forum/topic.asp?TOPIC_ID=457

For ref:
The performances and efficiency are documented:
Boyette: Rotocraft dec-jan 97-98 p.44.
Magni: Rotocraft dec-jan 00-01 p.27.
and others...
conclusions: better efficiency, better lift, less drag, less (no) vibrations, better flares, stiffer and cheaper blades, less fatigue, better sound and so on etc...
The scisor effect (lead-lag) is not well documented, it seems not to be a big issue for semi-rigid rotors.
Sportcopter solved this problem that exists even with two blades rotor...

Price=(may have changed...)
Sportcopter 25' 7"----> 1700$ X 2 = 3400$
Sportcopter 30' 8"----> 3900$ X 1 = 3900$

500$ cheaper with four blades! ok use them to have a heavier and more complex rotor head...
 
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From what I remember being told, using four blades, without a expensive and elaborate lead lag system, the rotor blades and rotorhead will try to tear itself apart in a extremely short time frame - in one or two flights!

It isn't the same as comparing the price of two sets of dragon wings to one set of fancy sportcopter blades, as there will still need to be alot of fabrication to make the blades have lead lag instead of being ridgid as they are.

Maybe Chuck Beaty will chime in, he knows all about the experiments Ernie and Rusty did.
 
The old Bensen rule for thrust-to-weight ratio was that a small pusher gyro needed 1 lb.of thrust for every 2 lb. of weight. You're a bit shy of that meeting that requirement, Chris. Disk loading is a problem, too: even a 29-foot dia. rotor gives a disk loading of around 1.8, pretty high for a small gyro. As you know, 1-place gyros run around 1.3 lb./sq. ft. Many heavy 2-placers are under-rotored, leading to the need for ridiculous amounts of power (100 hp/person) and a glide angle about the same as a free-falling rock.

The side-by-side config. involves a double hit to performance. It adds parasite drag, sure, but maybe more important is the poor flow to the prop. That's why side-by-sides with big pods are especially noisy; the prop is working in turbulent air, stalling and then going to zero AOA here and there as it spins.

I would guess that the engineless frame of that SXS Air Command would weigh no more than a Dominator tandem, maybe less. My Dom. tandem with 912 S weighs about 490, empty and dry. At a disk loading of around 1.6, it flies pretty nicely with 700-800 RPM difference between cruise and redline.

Is it the Soob or the Sportcopter blades that add so much empty weight?
Enough brute power will lift almost anything, but it's nice to fly with less power and more finesse, if you can. I'd get the biggest diameter (and most efficient rotor) I could fit, but I'd also think about an engine with a better power-to-weight ratio unless you have assurances from Prince that you can get 600 lb. of thrust out of your present engine.
 
Chris,
Dad is without power or phone (Damn Verizon) after the hurricane. The next time I am in his area I will ask if he is bringing a set of 28'. If he is, and they are not committed to someone else, I am sure he would be more than happy to let you try them. As for the four bladed system it was a great idea that needs a lot more work. The idea was abandoned in favor of a 3 bladed head you may see soon.
 
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Chris,

Thanks for the info. No, I didn't get a video with my blades - just a hat. CORRECTION: I did get a video - I just forgot about it but found it at home.

I thought I just had one thick washer (about 1/4" thick) on the top and a thin one on the bottom - and vise-versa on the other side. I'll look again - maybe the "thick" washer really is a stack of several washers.

If you do get to talk to Jim, let us know what he says.
 
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Hey Guys,

I really appreciate the interest and responses I've been getting, thanks.
All of your input is highly regarded!

Mike B., Thanks alot. Sorry to hear about the storm damage. I tried to call him today with no answer. Now I know why. In his ad in PRA mag he has 29ft blades listed. I wanted to ask him which ones he recommended and to see if he could bring a set to ROC for me to try and if I liked them, bring cash and take them home with me. If this doesn't happen maybe I could try Maxie's or something. Please let me know what he says. Thanks again.

Doug, I too thought about larger rotors doing a better job but Vaneck insisted 30ft blades would take more power to fly. I may never get to try a bigger set of Sportrotors. My SC blades weigh 86lbs. total. I imagine my engine package is about 200lbs. So I would say your frame is probably lighter.

Jim V. told me his EA81 performed just like mine is, full power all the time, but now he is very happy with his NSI EJ22. I'm thinking about going the brute horse power way.

I talked to Joe Souza later and he really tried to push Rotordynes on me. His prop recommendation for the Prince still stands. He claims he got 520lbs of thrust from his. That definitely wouldn't hurt my situation.

Jim V. told me to run the engine higher on RPM's by backing off the pitch until I started losing thrust. Basically, find the best thrust and go with that. He likes the Warp Drive.

Joe Souza told me to consider a Paxton Supercharger to add a possible 50hp safely.

I flew again tonight, with the 100lb bag. I love the machine, but I want better climb and weight carrying ability. I'll pick this up in the morning as we are very tired.

Good night all and Thanks again!
 
Ken, you should call & ask for the video. It goes through tracking & pitch adjustment.

After talking with him, I decided not to mess with the pitch because then I have to retrack. I just don't feel like messing with that.

Please try those blades again & let me know what happens. At least you have something to compare them to. Thanks, Chris
 
Chris, I believe, rightl or wrongly that larger diameter blades take less power to fly untill you get behind the power curve which will probably be 15 mph lower than it is now. Larger diameter rotors will fly at a less disc AoA to carry the same load. Less drag = less power required.
I really don't understand why Jim would say that.

Just get them blades longer!!!!!!!

Aussie Paul. :)
 
Hate to say this, but from what I have heard, RAF blades are good lifters and will haul alot of weight on less power than some other blades. Might want to try a set of RAF blades Chris. I know Larry has a set or two, see if he will loan you a set for a flight.

Maxie Wildes swears by RAF blades. He has flown alot of blades and really likes the RAF blades on heavy machines.

RAF's newest version of blades seem to be much better constructed than the older blades. Other than the bolt that holds the blades to the hubbar I would be comfortable with flying a set.
 
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Chris,

Have you evaluated any new front tyres yet?
 
Paul, maybe Jim didn't want me to try & trade blades with him. I tend to agree with you on this matter.

Ron, fitting Larry's RAF blades is already on the drawing board. Is Maxie using them on his tandem?

Tim, I already ordered a Hegar 4" wide by 6" dia. wheel with a 13" diameter round profile tire from LEAF. I'll let you know how it fits. Talking to Hegar, they said I could get 1/4" narrower but that would eliminate the tubeless spacer. I did not want to compromise strength or add a tube. If need be I can remove it later & see what happens.

Gotta search superchargers!
 
Chris: I have the newest rotorblades from RAF...and I have taken my 270 pound son, along with my 220 pound butt....22 gallons of fuel...and flew on an 85 degree day. The climb rate obviously wasnt good...and it wasnt expected to be....but those blades are tip weighted and landed with plenty of extra lift. I made a bunch of landings...and they were very easy to land as soft as you want.

Stan
 
Maxies only gyro, a Tandem Aircommand Ultralight trainer, is not to weight over 496 pounds to be legal. So the only choice he has for blades is Dragon Wings due to their being the lightest blades on the market.

Maxies old machine, The one that Automan1223 has now, used to fly with RAF blades and that was a heavy gyro. Maybe the heaviest two place out there. It flew good and could fly at least a 200 pound pilot and a near 300 pound passenger with a Stock Carbed EJ-22
 
My latest thoughts

My latest thoughts

OK , last night before dismantleing my gyro, to load on the trailer, for the trip to ROC, I did a few more "test" flights.

It was calm but it must have been some good air because, with the 100lb bag, my climb was not all that bad. I flew around for a bit & noticed my inst. pod wobbling pretty good(cabin hop?) This annoys me as I don't like anything shaking.

I landed & rid myself of the cement bag. I mentally prepared myself for the change. This time the front wheel came off quickly & I didn't have to balance for long before she became airborn. Wow what a difference! I had 500' before the end of the 2500' paved runway. I backed the rpm's down to 4600 & she still kept climbing. I could maintain 50mph & altitude at 4500rpm.Another note... the shake was gone. If only she would perform this well with another 250lbs!

My taller towers from AC put my teeter bolt 4 1/4" up from my bearing block. Jim V. said he liked more than that but he could use that, so my hub bar was built for that measurement. The other day he asked how that was working out & I told him...Fine. He said that I may get more shake when I add more weight, due to undersling. Well, I think the 100lb bag is enough to cone the blades far enough to make shake. Since I am making new towers to accept the RAF blades, I may talk to Jim V. about a taller teeter block to help smooth this out. Depending on my tests I may be asking for 30' replacement blades also.

I would like to try 28' DW's for a direct comparison but have a feeling I would be better off with 29' s. If the DW's do the job, I will buy them.

Would the 29'DW's have 2-12' blades with a 5' hub bar ? Could I adjust undersling by selecting another teeter bolt hole? Who thinks the DW's are going to blow away the SC blades?

How many of you think I am gonna like them so much that I plunk down the cash & take em home?

Who feels that it is a horsepower situation?


Today we will tweak the prop pitch to achieve max thrust even if I have to rev upwards to 6000rpm. Change oil & pan gasket & make her as pretty as possible for the "judges" ! I can't wait to pull in at ROC & see you all again. I think we are gonna have great weather & fun!
 
Just a quick note Chris,if you decrease the pitch on the blades a little they will spin faster,flattening the disc and may rid the coning shake.
 
Hmmm,stuffed that up didn't I.
Your git'n shake when your loaded,more RRPM.So to increase the pitch will reduce RRPM,and maybe rid the shake.

I'll shutup now.
 
Thanks Birdy & good morning..... Here anyway.

You mean speed up the blades for less coning , Right?

I will get to that phase eventually. But for now I am not gonna mess with the pitch & track yet. Thanks for the suggestion!

Have a great day!
 
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