Any suggestions?

[BEN S]

I have a rather heavy Sportcopter lightning with a Rotax 503 DCDI and a GSC PROP that is 64x32 two bladed wood prop.
I am thinking of going to a ground adjustable 3 blade carbon prop and was wondering will I even notice a difference? Is it worth the money, and who would you recommend?
Ben S

 

[WHY]

That's a tough one Ben, the 503 is only going to produce so much hp, so it really is going to be down to the "efficiency" difference between the two props. The airfoils on the 3 blade may be a little better than the wood prop but the 3 blades are going to load the engine more so you will have to probably run less pitch.

Tony

 

[BEN S]

Why...

Why...

your screen name makes it hard not to answer with a question, but anyway.
Will that give me more climb or more cruise speed?
Ben S

 

[Resasi]

Ben the composite will give you the chance of altering pitch. Here are some considerations for you.

Props, how well they perform and thrust they produce for any given engine depend, among other things, on diameter and pitch of the blade. The diameter of the blade in inches determines the size of the column of air pushed back, the bigger the better.

The pitch, given in inchs, shows distance the prop moves forward in one revolution assuming 100% efficiency. It also determines the amount of energy the column of air moving backwards has.

A good prop diameter/pitch combination is necessary to give the flight performance desired:-

Coarse props load the motor using lots of power to turn. Good acceleration, not so good with cruise as you fly at 75 to 85% engine power all the time.

Fine pitch uses less engine power to turn so the motor will rev to a higher RPM. Reasonable acceleration, good cruise performance. Once up to cruise speed you are able to back off the power more to maintain cruise speed.

At full power it is undesirable to have prop tips exceeding the speed of sound as a shockwave across the prop face decreases thrust, and as tips go supersonic they will be very noisy. The faster the tip after it goes past the speed of sound the greater the noise and lower the thrust the prop generates, as shockwave increases in size. Your prop diameter will also be governed by gyro geometry. Aim for a max RPM with tip speed about 80% of the speed of sound.

As well as the prop sizes, consider material and number of blades. Propellants operate more efficiently with fewer blades. With more blades each hits some of the turbulence wake of the previous blade. The more blades, the more engine power required to turn the prop. Low power motors tend to have two blade props, high power motors tend to have three or more blades to absorb engine power.

Props are constructed of either wood, composites or both. Wood tends to absorb harmonics and engine vibrations efficiently, hence their use on most direct drive four stroke motors. Wood props tend to be fairly inexpensive. Composite material props cost more, sometimes over twice the price, and don't absorb vibrations/harmonics very well. Usually slimmer built they can be more efficient than thicker wooden blades, and easiest to make three or more blade versions of. Tend to be used on high power applications. Pitch alterable. Durability and ease of changing pitch on them varies with type.

I went with a 62'' three blade Warp as this was almost the max size for the 503 we have on the Hornet. Went for a 52'' 4 blade Arplast for the Bensen and the 532 we have on that due the geometry. Get 310lbs thrust off the 503/Warp combo and around 320lbs thrust off the 532/Arplast. The Warp is pretty rugged, the Arplast a bit more delicate. Had an Ivo but blades flexed a lot.

Horses for courses and whether you want to spend some money and play around a bit with performance and pitch.

 

[BEN S]

Thank you Leigh,

Thank you Leigh,

It seems the more I learn about the props the less clear it becomes. I realize its all about trade offs. The price of the prop isn't really holding me back so that eliminates one of them, the weight of the 3 blade ivo is similar to my wood prop so not too much of an issue there. I would like to have a little more climb on takeoff but my top speed at cruise is only 55mph, and while I wouldn't mind a little more cruise speed I fly out in the open and too much speed gets uncomfortable. Hadn't yet called about the warp drives, but seeing that you chose them over the ivo prop on your 503 tells me something right there! I would love to borrow a prop for a weekend and just try it, but my buddy Daves ivo is very short which introduces another variable. Should I just get 3 blades that are the same size as my 2 blades now?
Thanks for the advice
Ben S

 

[Vance]

My propeller confusion.

My propeller confusion.

Hello Ben,

I hesitate to comment on propellers because I am confused on a fairly low level.

It is my understanding that an Ivo prop can be used as a two blade or a three blade very easily.

I seem to recall that an Ivo prop is very close to the maximum polar moment for the Rotax redrive. It would probably be worthwhile to look into that.

The numbers I have seen would indicate there is very little difference between propellers.

My personal experience would suggest otherwise.

In my opinion a larger diameter propeller is usually better at the speeds that most gyroplanes fly.

I don’t know how big is correct for a particular engine.

I have found that three blades confuse me further.

I feel a three blade propeller is usually quieter and smoother.

In my opinion a 503 Rotax engine has a narrow power band compared to my Lycoming so adjusting the propeller to take advantage of that power band may be more useful for you.

Even adjusting the propeller pitch for the mission may have value, pitch for climb when you are sporting around and pitch for speed when you are flying cross country.

Thank you, Vance

 

[GyroDoug]

Ben,

I am not an expert but will share my opinion on a couple of the questions you bring up. I believe the first priority is to get as big a prop disk as is practical. So if you have room to go with a bigger diameter prop, that will get you the biggest change in thrust. You reallly want to stay with fewer blades if possible as that will be more efficient. The biggest reason people put 3 or more blades on a prop is to be able to absorb and use all the HP their engine is capable of. Using a bigger diameter blade can also absorb more power, but once you have gone as big as you can, for your airframe configuration, then you take the next step by adding more blades. If you are going to stay with your 503, I suspect 2 blades will be enough to get the job done and will typically be cheaper, lighter and more efficient. If you were to change to a 582 or 912 engine you may need 3 or 4 blades to absorb the extra ponies you were adding.

Going to an adjustable pitch prop will allow you to dial in the exact pitch you want for the kind of flying you want to do and all other issues being equal, it woudl be a great addition to your machine if you can get it.

The Warp Drive prop isn't the lightest prop out there, nore is it the quietest, or most efficient, but it is one of the most durable. They can take a lot of abuse without having a catastrophic failure and on a pusher machine where things can go through it, that is a very good thing. Best of luck finding the ideal prop for your situation. I hope to see you again soon.

 

[BEN S]

Vance, Doug..

Vance, Doug..

Thanks for the input, I thought about the two vs three blade tradeoffs and still haven't come to a solid conclusion. GSC makes a two blade wood prop that is ground adj. I am not getting all that much help from talking with the manufacturers of the props as they all say theirs is the best. Kinda why I love this forum!
Vance, I DO like the idea of setting the pitch for the type of flying I am going to be doing or the DA I will be flying at, but not all of the props are as easy to adjust. and although the ivo seems to be pretty easy, as Leigh and others I have spoke to say that fine pitch adj isn't reliable on them as the blades flex too much. I know the warp drives reputation for toughness does appeal to me, but since I've been very happy with the wood prop with the epoxy coated tips, I'm not certain that it really is that big of an issue.
And hope to see you both again soon as well! (perhaps in Sept if I can convince my wife to let be return to the lakebed!)
Ben S

 

[j bird]

Ben, Warp is easy to adjust.

 

[Resasi]

The Ivo is the easiest to change pitch, just one nut and all the blades change pitch, but the blades are more flexible that the Warp. We found that the blades flexed when take off power was applied and that may soak up a bit of the thrust. It wasn't so much that the pitch setting was unreliable.

With three blades 63'' was about the max for a 503 and B box for the Warp. The weight/diameter of prop is limited by the engine/gearbox combo you have, and the diameter is altered by the number of blades. If you are using only two blades you should be able to swing a larger diameter than if you were using three. Guess that then becomes dependent on your engine airframe geometry.

Warp do a two blade version, cheaper too. The guy I spoke to at Warp was very knowledgeable and friendly, happy to give advice

You change pitch on each blade individually with a protractor, provided by them. Very straightforward but just a little fiddly.

With choice of pitch I guess there are also choices. Do you want acceleration or top speed. A coarser pitched blade allows you to accelerate quicker but loses out at the top end when you are looking at speed to a finer pitched prop. The finer pitched prop will not accelerate you as efficiently say during TO as a coarser pitched prop.

Then it is a question of extracting the max amount of HP from your engine without exceeding the max rpm in straight and level flight with WOT (wide open throttle). That you can play around with by altering the pitch settings and then running it with your gyro tied down. Put a scale in the middle and you will get your available thrust as well.

I did a lot of searching around to try and choose a prop and finally went with recommendations from people who flew gyros a lot (like every day, it's his business), and durability. Since we were geometrically limited on blade length we went with three rather than two blades to try and get as much from the 503 as we could.

Don't have much info on Arplast as it is a French company. Good prop but nicks very easily.

 

[BEN S]

Thanks as always Leigh..

Thanks as always Leigh..

I will look at the warp drive closer.
I wish there was a place where you could just borrow a bunch and bolt them on and try them out. Although my idea for a holster library didn't work out in the shop either.
Wouldn't that be a great way of shopping for stuff though? you just go and try it on for size ands see if you like it! Could be made to work with women as well, like a dating site or something! Oh wait I guess thats called a cathouse.....
I'll call warp guys today.
Ben S

 

[PW_Plack]

...A coarser pitched blade allows you to accelerate quicker but loses out at the top end when you are looking at speed to a finer pitched prop. The finer pitched prop will not accelerate you as efficiently say during TO as a coarser pitched prop...

Actually Leigh, I think this is just the opposite. A "climb" prop has less pitch to allow the engine to reach max HP at static, while a "cruise" prop is coarser (has more pitch) to allow using all available HP at higher airspeeds without exceeding engine redline. That much pitch can cause partial stalling of the prop at low speeds, and may not allow full HP for the start of a takeoff run.

Another reason some people go to props with three blades is the same reason some rotors go to three blades - to reduce vibration.

 

[j bird]

Ben, do you think Sportcopter knows what their doing? Why don't you use what they use on a 503 Lightning.

 

[Kevin_Richey]

Try-a-prop

Try-a-prop

Ben: Have I got a deal for you!

Would you like to try a brand new RH three-blade 62" Sport Prop?

Or, a used RH three-blade 65" SP?

You can for free w/out buying! How about you just pay the shipping to/from here to there.

You can then get an idea what type of thrust differences they give you w/out having to pony up to a manufacturer to try one out...

I have both. The 62" one has the leading edge tape come loose from years of heat and cold in the hangar working on it, and would need removing, along w/ the sticky residue. The 65" one doesn't have that leading edge tape, and has the later-offered curved tips. It came from the late Ken Rehler's custom built gyro. He sold it to me when he went with an engine that required a LH prop.

What full-throttle speed do you get w/ your GSC wooden prop you have now? Jim V. says that the 62 mph, straight and level, full throttle speed I get w/ the same prop you have is directly related to the pitch, to keep the Lightning's top speed restricted to be under the 63 mph ultralight limits. This was back when the Lightning was marketed as an ultralight, which Jim V. said the first one or two did meet ultralight regs.

 

[BEN S]

Jay,

Jay,

I talked to Evan (at Sportcopter) for about an hour about the prop differences and he wasn't convinced it was going to make much if any difference for me. The fact that just about all the guys here use ground adj props tells me it might be otherwise. but what I really need is to try it on my machine. It's not that I can't afford to buy the prop, I just hate spending the money to find out there is no difference.
Ben S

 

[BEN S]

Kevin

Kevin

I'll call you as soon as I get a free moment here.
Ben S

 

[scottessex]

Ben I have a 64" IVO prop that is set up to be used as a 2 blade or 3 blade.
I posted it here before but no one was interested. PM me.
https://www.rotaryforum.com/forum/showthread.php?t=29927

 

[BEN S]

Hey Scott!

Hey Scott!

Message sent!
Ben S