If you have an MTOW of 650lbs, Why do you want a 25' rotor system?Airworthy balanced set wanted for 650 lb MTOW machine that will work on a Bensen type head. Looking at buying new Sportster 7" 25' for a basic capability if I can't find a deal.
Using Jukka Tervamaki calcs. Also Sir Hollmann's. I'm at 3600 ASL. Running their calcs seem to work. I have not developed my own math or codes on this. I am an engineer with tons of math and physics. However, I need to rely on people that have been there and done that. Please, please give me your insights.If you have an MTOW of 650lbs, Why do you want a 25' rotor system?
How does your engineering math work this out?
I would really like to see the math used that come up with 25' disk at 650 MTOW.Using Jukka Tervamaki calcs. Also Sir Hollmann's. I'm at 3600 ASL. Running their calcs seem to work. I have not developed my own math or codes on this. I am an engineer with tons of math and physics. However, I need to rely on people that have been there and done that. Please, please give me your insights.
There's a bunch of math, but I like the rule of thumb Hollmann asserted: around 1.9 lb/sq ft disk loading (DL). That's similar to specs ultralight fixed wing planes are designed. For a 650 lb MTWO at 25' rotor diameter (2r) : DL = MTOW/pi*r^2 = 650 /(3.14*12.5^2) = 1.32 lb/sq ft. ... Low. Could go to 20 ft diameter ... gets about 2 lbs/sq foot. Another factor, solidarity is percentage of blade area to disk square footage. Hollmann had another target number for that. I plugged into Tervamaki's calculator get to a rotor size that would optimize rate of climb at about 1000 ft/min given my projected MTOW, 50 hp max engine and optimized propeller. I would prefer a larger rotor since I start out at 3600 ASL.I would really like to see the math used that come up with 25' disk at 650 MTOW.
Ya know, equation = answer
Thanks. I have Hollmann's design book. His main work was back in the 70's ... but he updated over time. A lot of good stuff. But there's been a lot done since. I use his work as a thoughtful reference. The sportster was a mechanically busy machine and seems to have had a high thrust line. Don't know. Don't have those numbers.Wayne think twice about a Sportster. They look cool but weren’t the most stable of designs. If you want a Gyro from that era look at a Barnett. They are much more pilot friendly. Yes, I’ve flown in both.