Is a rigid 3-bladed rotor for UL possible? I think yes….ignoring the 254 thing….

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RotoPlane

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Notice how straight the lift graph line is in Rotorblade3B UL.jpg…..a rectangular blade would have that line looking like a pot-bellied pig. There is more auto-rotational pull available in this middle driver section.

With 3-blades, this blade profile also has more lift than I wanted with the 7" tips, so I had to go down to a 6" tip. I was surprised how far outb'd the lift centroid or CP fell. The spreadsheet spec.'s are shown in that *.doc file and that data agrees with this drawing.

The forums 150 kb limit doesn't allow hardly anything to be uploaded that I tried....and then it's mostly to grainy to see well. I once was able to use .pdf's for most stuff...rarely can get one to upload now...sorry.

Anyway, I thought I'd show you the way I'm headed....thanks Chuck B. for warning me about using 2-blades with my rotorhead.
 
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Just out of curiosity, how much do the servo flaps impact the blade's performance?
 
Good question Brett….that is something I wondered too. A few years ago I read a post about if the servo-flap drag affected autorotation rotor rpm on the Lynx (I think in Pprune). As I remember, the answer was the pilot could not discern a difference with other non-servo-flap rotors.

The servo housing on my blades has a 0010 airfoil with a drag coefficient of .0093 @ Re 1,161,200 (paint finish) and the servo-flap has a 0015 airfoil with a Cd of .0096 @ the same Re. Those Cd values are quite low especially when considering their low surface area compared to the blade….but only time will tell for sure how well that rotor will fly.

This flap is in the shadow of the blade while at 0° pitch but I believe the gap or slot between them will provide this flap with a smooth airflow when it is deflected to twist the blade by acting like a wing split-flap. The flap (through the collective) will twist the driven tip area more than the root, so it will act similar to a Dragon-Wing blade, only in both plus and minus degrees.

I am sure you will love the smooth, no vibrating cyclic stick ;).
 
Fascinating Ed. I wish I had the knowledge to give any input. I just keep reading and learning rather :)
 
I'm glad Gabi….cause that is what I do when reading your thread….learn. I have also been learning other stuff…like training my eyes to discern a lizards shape while hanging from other forms ;).
 
brett s said:
Just out of curiosity, how much do the servo flaps impact the blade's performance?
Click to expand...

One thing I failed to mention Brett in my post above, is that servo-flaps can cause acceleration cross-couple if the cyclic stick is moved faster than the blades can react. I didn't know about this until Al Hammer warned me of this possibility awhile back. It can be avoided by using lower rate control inputs.

I understand that Lynx pilots are taught to apply gentle control inputs in normal operations; as long as you move the stick gently you can demand rapid maneuvers with large cyclic displacements….without encountering the effects of acceleration cross-couple.

I expect that a small diameter, fast rpm rotor will have less problems with cross-couple than a large diameter and low rpm rotor. I have a fix if I find that this is a problem with my rotor.
 
Hi Ed,

You mentioned Lynx pilots, which Lynx are you refering to ?

The only Lynx helicopter I know doesn't have servo flaps to the best of my knowledge.

Or did I misunderstand what you were saying?
 
The only production ships I can recall ever using them were all Kaman designs, those were teetering rotors too (edit - I forgot about the SH-2, don't know what sort of rotor it had)
 
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karlbamforth said:
Hi Ed,

You mentioned Lynx pilots, which Lynx are you refering to ?

The only Lynx helicopter I know doesn't have servo flaps to the best of my knowledge.
Click to expand...

I know they were talking about the Lynx helicopter, and I remember Kaman being mentioned....but I googled it and now I think I may have been thinking about the Seasprite or K-Max when they said Kaman. Time has a way of screwing up my mind thoughts Karl....

I can however see where servo-flaps could cause some delay like in the phase angle or perhaps still be trying to make the rotor go left while a pilot is rapidly moving the cyclic right, causing cross-coupling. It is going to be fun finding this stuff out ;).
 
Ignoring the 254 thing?

Ignoring the 254 thing?

Hello Ed,

What does “ignoring the 254 thing” mean?

What is the allure of an ultralight for you?

Thank you, Vance
 
The 254 thing refers to the Part 103 rule for an empty weight of 254 lb. I will be filing a waiver request for adding the float allowance to the empty weight. I can't seem to find that float weight now, but I think it was 30 lb….perhaps 50 lb. That third blade kinda put the hurts to my empty weight.

The allure of an ultralight is age and a lapsed medical….and I know there are others out and about like me and haven't flown as pilot in command for many years. I may try to get current later but I just don't want the hassle right now. Plus, under Part 103, I can change things on the gyro as needed, without the EAB required FAA paperwork.
 
Will your ship actually be capable of operating off water?

If not there's no chance in hell they'll give a waiver simply because your ship weighs somewhat more than 254 lbs & you still want to fly it as an ultralight.

Here's what you were looking for from AC 103-7:
Floats Used For Landings On Water.
Only the weight of the floats and any integral, external attachment points are excluded. All other items associated with attachment of the floats to the airframe are included in the vehicle's empty weight. Up to 30 pounds per float may be excluded by the FAA
without requiring substantiation of the float's actual weight. This exclusion was allowed under the rationale that float-equipped ultralights would not usually be operated in the vicinity of airports and large concentrations of people and, thus, would be even less of a safety hazard than those which had conventional landing gear. While amphibious capability would appear to negate somewhat that rationale, some allowance for the "float" capability is made.

Amphibious Floats.
up to 30 pounds per float may be excluded by the FAA. The weight of all attached items associated with the installation and operation of the landing gear is included in the calculation of the dry, empty weight specified in 5 103.1(e)(1). Satisfactory evidence of the weight of those components must be available.

Amphibious Fuselage.
Where the fuselage is intended to function as a float during water landings, up to 30 pounds (tile average weight of a single float) is allowed by the FAA to be excluded from the empty weight where the ultralight is capable of repeated water takeoffs and landings. (Operators may be required to demonstrate the water operational capability of their vehicle in order to receive an allowance for the added weight.) Up to 10 pounds per outrigger float and pylon is also allowed by the FAA.

"Float" provisions not discussed here should be reviewed with FAA personnel at a Flight Standards field office.
Click to expand...
 
Ed,

What was your thinking behind the servo flaps? I have been interested in servo flap control for a long time but on gyros. I have even made blade segments to study the mechanics of the movement of the flaps.
 

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Goals and limitations.

Goals and limitations.

The limited range from 5 gallons of fuel and 55kt maximum speed seem to me like some pretty big limitations to avoid studying for a test.

When we changed the engine on the Predator the paperwork seemed very straight forward and the return to phase one was probably a good thing to sort things out. I found value in having two knowledgeable gentlemen looking over our work.

The process of getting an airworthiness certificate seems simple enough.

What am I missing?

Are you going to get flight training?

Are you going to conduct the first flight?

Are you going to manufacture and sell this aircraft?

How much do you feel your 3 blade system will weigh?

When I began building Mariah Gale I found value in articulating the why of it including the reasons for the build and the goals of the project.

I would love to see a similar mission statement for your aircraft. I suspect I am not alone in this.

I feel it would make it easier for forum members to help you.

Thank you, Vance
 
Joe -I look at servo-flaps as a natural way to control flexible in twist rotorblades….especially when using a rigid rotorhead. They eliminate those heavy pitch bearings and the high cyclic loads caused by the constant pitching of the blades. I believe Kaman's servo-flaps are the right way to go for gyros too….because they eliminate the direct cyclic movement of both the rotorhead and blades and could be used with a semi-rigid head. I personally feel that you are on the right track Joe……
 
Vance said:
.
Click to expand...
The limited range from 5 gallons of fuel and 55kt maximum speed seem to me like some pretty big limitations to avoid studying for a test.

Heheh….yes it does huh….but I'm looking at this UL as a test bed for a larger machine to come later, and it forces me to keep it light.

When we changed the engine on the Predator the paperwork seemed very straight forward and the return to phase one was probably a good thing to sort things out. I found value in having two knowledgeable gentlemen looking over our work.

The process of getting an airworthiness certificate seems simple enough.

What am I missing?

My freedom from paperwork? I had a lot of that for years as a Projects Engineer....it has value but I am recording HD video of each step as a record for any future needed paperwork.

Are you going to get flight training?

Yes...as a refresher. I'm a good airplane driver.

Are you going to conduct the first flight?

You bet...my ideas, my work,….my responsibility. I couldn't bare it if someone else got hurt testing my machine.

Are you going to manufacture and sell this aircraft?

If it flies well and is safe...perhaps I may make plans available.

How much do you feel your 3 blade system will weigh?

Not absolutely sure....but right now, I can see almost 30 lb over the 254 lb limit.

When I began building Mariah Gale I found value in articulating the why of it including the reasons for the build and the goals of the project.

I would love to see a similar mission statement for your aircraft. I suspect I am not alone in this.

I feel it would make it easier for forum members to help you.

I'm sure you are correct Vance, but my project is tiny compared to yours. Also, did I mention abhorring paperwork? EAB will bring that on in due time....
 
Just out of curiosity, how much do the servo flaps impact the blade's performance?
Click to expand...
To get an idea about the changes in rotor behaviour when drag is added one might have a look at this analysis of a rotor with tip jets:
http://hdl.handle.net/2060/19930082771
The most interesting part is tables one and two. Note e.g. how collective changes from slightly positive to negative with increasing drag.
 
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Rotor Rooter said:
Ed,

These might be of value, if you don't already know of them.

Trailing Edge Flaps for Active Rotor Control Aeroelastic Characteristics of the ADASYS Rotor System


The Servo Flap Controlled Rotor

Also some trivia. Nick Lappos mentioned years ago that a trailing servo-flap that is close to the trailing edge of the blade will pitch the blade in a different direction from that of a servo-flap that is a reasonable distance back from the trailing edge of the blade (as is yours).


Dave
Click to expand...

Thanks Dave. I have read the servo controlled rotor and I vaguely remember reading about the ADASYS rotor system. I wanted more flap control power than a "aileron" type could give me for twisting the blade 12° max with collective pitch….perhaps ~15 to 20° on the servo-flap.

You're right….the aileron trailing edge down causes the blade to rise (not much of a twisting action) and the spaced aft flap trailing edge down causes the blade to twist onto a dive.

An advantage of the aileron type is the blade can be torsionally stiffer than for the flap type and still work, but I think it would be more sluggish than the flap.
 
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