Interesting question came up yesturday..

[BEN S]

I was talking with my buddy Dave about upgrading my engine from the 503 to the 582 to have increased performance, and he suggested a cheaper alternative, Since I don't seem unhappy with my machines ability to get me into the air and the cost involved in upgrading, wouldn't i be better served by switching from a wood 2 blade prop to one of the high performance types with 3 blades and adjustable pitch? At least it would be cheaper.
Well I have no idea what that would do as far as my performance would be, btu I was concerned about the fact that I fly off a gravel runway and how would the props leading edges hold up?
What do you guys think. Since top end speed is of little consequence to me and I usually putter along around 45 to 50 mph would a new prop excite me or will I eventually just need to get the 582?
the machine weighs about 300lbs and I weigh 205 and I am 100 ft above sea level.
Ben S

[brett s]

It would likely give worse performance unless the one you currently have isn't a good match, assuming you're talking about a ground adjustable one. You'll add more weight too.

A 2 bladed one will be more efficient at these speeds unless you've got too much power or are limited in the diameter that'll fit.

[scottessex]

A 50 HP engine is only going to be 50 HP regardless of the prop.
Multiple blades soak up the extra HP when you are limited by diameter,
with a ground adjustable prop, you will be able to set the pitch and get the best
climb or cruise performance whichever you prefer for your flying style.
Id get a 3 blade IVO and take a blade off, that way when you go to the 582 you can throw the other blade on without having to buy another prop.

[Aussie_Paul]

...Add an extra foot to your rotor diameter with a longer hub bar. Just a thought.

Aussie Paul. :)

[BEN S]

That is one I had not considered..what would that do to my performance?
Ben S

[Master Roda]

When you say performance, what do you mean?

[BEN S]

I was thinking about anyway to increase my climb performance as top speed isn't very important to me.
I had a chat with Evan and he kinda set me straight...if I'm gettin all the power I can out of my machine then any changes aren't really going to help me.
And I can't afford to upgrade to a new engine and rotors yet.
Ben S

[Master Roda]

You need power to climb Ben.

[BEN S]

As I understand it it takes MONEY to create lift!;)

I'm not unhappy, but just dreaming out loud about what small upgrades i could make.
Ben S

[scottessex]

Go on a diet? :D

just kidding. The 582 will give you much more power.

[BEN S]

I am always working on the diet part, as far as the 582 goes, it isn't just the simple drop on replacement I had hoped for as I will need to replace my rotors and hub as well. something to do with tip speed and weight of the machine I gather.
But yeah losing some weight couldn't hurt.
Ben S

[scottessex]

I hate all those little guys that weigh 150 lbs. They can fly a 503 like a rocket ship! :(

What size are your rotors? The 582 I think is about 15lb heavier than the 503,
If you are at a higher elevation, than YES larger rotors will help a great deal with climb and performance.

[BEN S]

my rotors are 23 footers I believe. I will probably upgrade to a 582 at some point in my future, but I just love the reliability of the 503. I am not the most mechanically inclined and the idea of having a cantankerous or finicky engine just doesn't sit well with me.

You know if I just lopped off both of my legs like LT Dan in Forrest Gump, I could loose at least 50 lbs right there!
Ben S

[RotoPlane]

Ben is that 100 feet ASL a typo? You can climb faster by brute force (582) or a gentler way by using more disk area…..as long as you are around 1.3 lb/sq.ft. disk loading. As Paul said, you may be able add some hub-bar length to get there.....

[Master Roda]

Ben,

At your gross weight, your at 1.3 lbs/sq.ft.

[BEN S]

Yuma is not very far above sea level, it just gets really hot here in the summer. As for the disk loading figures Jon is most assuredly correct as he knows my machine and he built my rotors. is 1.3 good? is it too little? Any of my friends will tell you that I am mathmatically challenged....so what does the disk loading mean as far as performance or climb rate goes? How would extending the hub bar help that?
As we used to say in Dive School "I am but a hungry sea sponge in an ocean of knowledge"
All comments are welcome.
Ben S

[RotoPlane]

Ben, if you have 7" chord blades, a 2' hub-bar, 22' dia. rotor and hauling a 505 lb AUW, you have the approx. following spec.'s:
(A)
Disk Loading: 1.33 lb/sq.ft.
Blade Loading: 39.35 lb/sq.ft.
Rotor RPM: 387 (this depends on airfoil and blade incidents)

Changing the hub-bar to 3' long….you will have a 23' dia. rotor with these approx spec.'s:
(B)
Disk Loading: 1.22 lb/sq.ft.
Blade Loading: 37.64 lb/sq.ft.
Rotor RPM: 362 (this depends on airfoil and blade incidents)

Item (B) will float more (rougher ride) and climb faster than (A)……. and is cheaper than a 582. Perhaps you should talk to Jon since you have his blades……

[BEN S]

I don't fly with a rotor tach. is lowering the rpm on the blades a possible problem? What are the drawbacks involved in lengthing the hub bar? Is there a magic nuber for the disk loading that gyros are looking for?
I really appreciate the help.

On a side note this should be my 300th post.....do I get another star yet?:ohwell:
Ben S

[RotoPlane]

A disk loading of 1.3 lb/sq.ft. is considered optimum.
At 362 rrpm, you will have a tip speed of 436 ft/sec…..400 ft/sec. is considered optimum.

[RotoPlane]

I'll add this….since it gets hot there and you fly slow, I would think that you would like a 23' dia. rotor….unless you fly in gusty high winds. Pete (Passin' Thru) has done a bunch of flight testing on these types of things and he could give you a definitive answer.

[Master Roda]

Ed,

I have flown my blades on a lightning (22,23,24,25) with no problems. Well under 1.3lb/sqft and over.

Ben just needs more power. Sorry Ben.

[BEN S]

TNSTAAFL.....If you are a sci-fi buff.
I can hope and dream cant I?
What about putting one of those R/C jets on the back?
Ben S

[RotoPlane]

When confronted with a low climb rate, one needs to first look at inefficiencies and then lack of power. Right now your 22' rotor is turning ~387 rpm with a tip speed of 466 ft/sec. That rrpm takes more power due to blade drag than say if the rotor was 23' and turning 360 rpm or 436 ft/sec. With these figures, if the blade pitch angle could be increased, I would set the rotor to 340 rpm (I like even figures) or 410 ft/sec. This lower rrpm will allow the disk angle to decrease some, resulting in less drag and therefore a greater climb rate or airspeed. Streamlining some high drag airframe areas would also help. At least that is how I view it…… But then, since you're rich….go for the 582 ;).

[BEN S]

I looked at putting on some of those airfoils that fit over the tubes on my gyro to help streamline it, but the were not that easy to install on a machine that is already built and I didn't know if they would work all that well anyway.
Perhaps a very lightweight half pod on the front would help, but it would have to be featherweight.
Maybe someday I will have a 582 but for now I'm pretty content to fly around and look down on all the little people.
I do appreciate your ideas though.
Ben S

[Master Roda]

When confronted with a low climb rate, one needs to first look at inefficiencies and then lack of power. Right now your 22' rotor is turning ~387 rpm with a tip speed of 466 ft/sec. That rrpm takes more power due to blade drag than say if the rotor was 23' and turning 360 rpm or 436 ft/sec. With these figures, if the blade pitch angle could be increased, I would set the rotor to 340 rpm (I like even figures) or 410 ft/sec. This lower rrpm will allow the disk angle to decrease some, resulting in less drag and therefore a greater climb rate or airspeed. Streamlining some high drag airframe areas would also help. At least that is how I view it…… But then, since you're rich….go for the 582 ;).

He has 23 footers Ed.

Ben,

Go for the jets!!

[RotoPlane]

He has 23 footers Ed.

Ben,

Go for the jets!!

Oh….you said he was at 1.3 lb/sq.ft in post #15….so with a 505 lb. AUW…….
The (sqrt of ((505/1.3)/PI)) X2=22ft. If he already has 23 footers…then I wouldn't go lower than the 1.22 lb.sq.ft disk area……..so a larger engine is needed. Just thought I would clear myself up ;).

[Master Roda]

Oh….you said he was at 1.3 lb/sq.ft in post #15….so with a 505 lb. AUW…….


I think he's closer to 550 Ed.