Monocopter formula question =advanced=

First off, Admins, thanks for listening. Hat's off to ya!




Now this may not even exist right now, or maybe I missed it, but I'm looking for a way to calculate the optimum angle of attack for the blade of a monocopter. It seems there has to be a stall speed and hover speed, somewhere in between is the optimum.

Firstly, if there are any RC folks out there, I'm guessing there is a formula which will give a lift number to a laminar flow airfoil. This number would probably have to have adjustment based on wing length versus width (as an airfoil can have a similar square area, though one could be twice as long and as thin as another).

Secondly, all the factors would have to be involved which include (and I may leave something out)

Dry weight
Loaded weight
Cd (probably a constant for the most part)
Square area of the wing
Length of the wing
Maximum thrust spike
Minimum thrust

And from this could revolution be calculated? If Prof Graham's book has it hidden in the mix and I've missed it I'd appreciate a lesson.

Chuck

chuck, if you wouldnt mind, i'd like to post this question on a different forum where i am 99% sure that an answer would arise.

In his book, Francis Graham derives a set of three equations which govern the flight of monocopters, and which must be solved simultaneously. The angles of the wing and the pop are part of these, as are the dimensions, the thrust used, etc. They are not simple or easy to convey, and I'm not sure I should provide scans of the major useful part of his book. Its worth a read though.

The problem is it varies substantially from the inside portion of the wing to the outside portion, even on MC designs with fairly narrow wings.

Remember the determining factor is tip travel.

Jerry

I would say, "pardon the tech post", but this forum is 100% tech posts!

Originally posted by r1dermon
chuck, if you wouldnt mind, i'd like to post this question on a different forum where i am 99% sure that an answer would arise.

Click to expand...

R1.......If I were in a hurry, I'd post it in every forum I belong to. But for once I have some time to wait and I figured this would be a way to 'ferrret' out the other monocopter guys and pick their brain, unfortunatley for them that would be a one way street.

So it's more following the ancient Hindu proverb of, "the journey is the reward" which in America is simply known as "gone fishin". Hopefully within this thread some discussion of what some are working on may come out. Or one of them precocious young kids could use this as a science experiment and surprise us all.

Dick....I also have the monocopter book. You feel all three equations must be satisfied simultaneously? I'm getting lazy, I was hoping one would suffice. I'm guessing that since the RC guys also use monocopter designs and they don't have the brute force we possess they may have to follow the equation far more precisely. Can't we cheat somewhere? And I doubt the professor wants his pages here, unless there's something important after page 53, as I got 8 page 55s.

Jerry......this is why I had a feeling that not just air foil square area, but also the length of the wing had to be in the equation. Obviously as the length increases so does the tip speed. Your point on tip travel is taken, but to figure that requires a way to estimate RPMs.......then we would have a chance.

And while I'm on the subject of Monocopters I believe it's a necessity for anyone going past the E motor range use a purposebuilt steel pin as a launch pin. You are tempting fate with F or higher or stouter (read that as overbuilt and heavy) airframes. I'm speaking from experience on this one. ;-)



Chuck

Originally posted by Chuck Rudy
Dick....I also have the monocopter book. You feel all three equations must be satisfied simultaneously?

And while I'm on the subject of Monocopters I believe it's a necessity for anyone going past the E motor range use a purposebuilt steel pin as a launch pin. You are tempting fate with F or higher or stouter (read that as overbuilt and heavy) airframes. I'm speaking from experience on this one. ;-)

Chuck

Click to expand...

As I remember all the equations are required; may depend on which values you fix and which you solve for. I did not convice myself that these are 100% correct either, but they are allthere is as far as I know. He is working on a new formulation and has a glimpse of it on the Tripoli Pittsburg site.

For a launch rod for my big monocopter, I used a dull drill bit. Some brass tubing (1/8" or thereabouts) was used as the a shoulder that supported a large washer. The the bit extends about 3/4" above the washer. JB Weld holds it all together.

Dick

I'm gonna play with one new one this saturday if the weather cooperates, just have to attach the boom and drill the lug. It's not big but this one's gonna be a head's up. You headed to Price? I'll bring along the new pad and we'll see if we can't get off a few flights. I'm tied up Sunday so it's saturday or bust for us.

Chuck

Chuck, I'm going to be there Sunday to pick up motors from Ken. I'll look forward to pics and a report though. (pics don't have to wait for the launch )

Dick

It rained and we didn't get the first flight off till 2:30pm. I took the new design mono and was shocked as all getout. It was, without a doubt, the best handling monocopter I've ever flown. And I have no idea why. Flying on a G33 it was heavy (@ 1.4#) and though it followed the wind it stayed vertical far longer than any other i've flown, possibly because of it's weight. The wind didn't really affect it until the back end of the burn. And the coup d'grace of monocopters, it autogyrated beautifully to a soft landing. I believe autogyration comes with efficient wing design, but there is nothing to back that statement. I was more concerned about this one than any other I've built, but it ended up being a most perfect flight. So we did it again.

Now how to figure out what made it work so well.......or just keep building by eyeball.

We are going to try to get an altimeter to work on this one, which will give us one more piece of the puzzle when it comes to comparason. I have a feeling RPMs can be done on a vertical stand, I've just got to find a counter which will trip everytime the mono makes a rev. Adding to the puzzle is the fact that since the monocopter's CG constantly moves away from the motor toward the wing tip as fuel burns off a vertical pole will not give a perfect number. Friction from the growing out of balance condition will make the spin fade. But it will be something to go on.

Chuck

In all the excitement I kicked my brain into neutral and left the new monocopter pad at the field. Ah well, that one cost $4 to build, I guess I'll just have to do it again as it appears that one has become a donation.

https://homepage.mac.com/wesrudy/Chassis2Test1.mov

I will keep this up for one week. This is the video of the preceeding description. There is one more step for this airframe so there will be more. Though it may take two months. This was designed for something different, but it had to go through this test first. More to come.......

Chuck, what a great flight! I need to build another monocopter, maybe this winter.

Ooh just saw your earlier post. The autogyration was nice. My big monocopter didn't attain enough altitude on 2 E9s and fell more like a brick

Dick

Make it with a half inch launch lug, the newly donated mono pad works well on it. ;-)

Chuck

Jerry!!

Hopefully you saw the mono in the vid on the G33....your thoughts on a 1.4#er going up on a G008.......I wanna do it, but after the full science thing with the 'special' motor runs it's course.......It's the thrust to lift ratio I have a concern of......any thoughts?

Air foil 5" X 20 1/4"
OA lenth 26 5/8"
Air foil thickness 1/4"
1.4 pounds
Angle of attack 8.25 degrees
Wing tip to Cg 21 9/16"

Anything info you have, lay it on me!!

Chuck

Chuck,

Did you contact MDRA regarding the 'donated' pad/rod? I am building a monocopter and am pondering wheter to use a 1/2" lug or the set up I used before. I want to see what the are chances that your pad can be located in the huge pile of MDRA launch equipment.

Yes I did, I let Neil and Dave know. It should still be sitting out at the C cell at Price as they leave all but the electronics to save build up and tear down. C 5 as I recall.



Chuck

Thanks. I need one point of clarification. With you set up, do you mount a 1/2" lug in the 'copter, ir is it a 1/2" stud (ie dowel or whatever)?

The stud on the pad is a 1/2" steel dowel. On the mono I just drilled a 1/2" hole in the CF at the intersection of both CGs. I haven't reinforced it yet, but will epoxy in something soon.

Chuck

Just wondering if rldermon or anyone else ever came up with an answer to Chuck's question.

And Chuck, any more development work on this?