Propeller diameter on GyroBee?

rcflier

Junior Member
Hi guys.

I should've asked this before:

Rotax 503 with slightly later A-gearbox.

How large a propeller can I use?
(I'm thinking of 3-blade Ivo prop)

At the moment I'm looking at 60 and 62" propellers.
But what is max. as the larger the better (within reason)?

Cheers
Erik
 

Boots

Active Member
My bee has a 447 2.58 -1 gearbox and 60" 3 blade iVO prop. The tail boom can flex quite a bit on the gyrobee so I wouldn't put a larger prop on it . 60" is right for it.
 

Doug Riley

Platinum Member
You can go a bit above 60" by tilting the engine, prop-end-up. But do watch that tail-tube flex, and/or brace it to the fuel-tank tray.
 

rcflier

Junior Member
Guys, thank you both for your advice.

Boots, that's quite a small engine on that Bee. What blades do you use?

Doug, you already know I have 23' Skywheels, so you know I need all the thrust I can get.

Yes, I know mounting the gearbox with the shaft up, would give more space.
But what is best, CLT wise? Wouldn't it be best with the shaft down?

The thing is, a guy calling himself Jack Ross near Orlando is selling a low hour
IVO prop, 3 bladed 60", for a third off retail price. And even at $660 for a new
one, I'd much rather have a fiberglass propeller than a wooden one. And being
adjustable should help in achieving max. thrust.
My A gearbox should be able to handle that, as it has the large number of springs.

Cheers
Erik
 
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Doug Riley

Platinum Member
Erik, Skywheels are much heavier than the metal blades that we 'Bee-heads usually use. They will bring your CG up, closer to ideal than ours.

As I think I've posted before, my Air Command 447 with 23' Skywheels was a dog on a hot day, while my 'Bee with the same engine, but 24.5 ft. Rotordynes, climbs quite a bit better.

It's best to mount the engine with the gearbox down, even with your possibly better CG location. The 'Bee has a vertical (not aft-raked) mast, at least partly to accommodate the upright engine-down box setup.

It's better to move the whole engine mount up to fit a larger prop, and build in 3 deg. or so of front-down tilt, if you must. That's how I managed my larger prop.

The IVO prop is VERY flexible. If you buy and use one, make certain it can't flex forward and hit anything.

I have a simple 2-bladed wood prop. About the lightest thing you can use, and inexpensive to boot.
 

phantom

Newbie
Can anyone tell me why they use a three blade prop on small engines like 447 and 503 , it seems like you would want the max amount of thrust from the engine but I see a lot of three blade props and I have done tests and you gain performance by not adding a third tip to drag through the air.
Norm.
 

rcflier

Junior Member
Norm, the reason more than two blades are used, is Space (edit: Not true).

Remember the WW2 Corsair? It had to have short legs for
carrier operation, but the large engine needed a large prop.
So it had inverted seagull wings to have as large a prop as
possible and keep the blade count to "only" 4.

I now read Taggart's manual again - he doesn't discourage
the use of Dragon wings on the Gyrobee - sorry. Maybe I
should make the swap, someone told me I could make locally.

Doug, what propeller are you using? Someone on forum is
selling a nice, new wooden 62" prop. I just thought it safer to use a
fiber reinforced propeller. And ground adjustability is a nice
thing. A wooden propeller is hard/expensive to transport over the pond.
An Ivoprop or a Warp Drive is a much shorter package.

Cheers
Erik
 
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phantom

Newbie
I should have made my question more clear as I know the real reason for more than two blades but what I don't understand is why a three blade 60 inch prop is used on a 447 when a 60 inch two blade will give better performance and be lighter, two blade props don't make that horrible sound that a three blade makes and a small light gyro handles better with a two blade prop so why use a three blade?

Norm
 

Doug Riley

Platinum Member
Norm: A couple reasons come to mind.

First, a 3-blader is smoother. Two-bladers set up a drumming vibe in the frame. It's not bad but it's there.

The second has to do with the U.S. ultralight regs. As you probably know, our regs allow us to bypass both registration and licensing if (among other things) our aircraft is incapable of going faster than 55 kt. or 63 mph, wide open, level. Compliance can be a problem, as a gyro rotor's drag DEcreases as you reach these speeds.

The theoretical way out is to use a very fine-pitched, or "climb" prop. A fine-pitched prop tends not load the engine down adequately at cruise unless it has either lots of diameter or more than two blades. Air Command set the example by using four blades on the original Air Command UL gyro, and others followed suit.

(I don't know how well the 4-blade strategy really workled on those machines. A friend of mine had a box-stock Commander 447.
He regularly blasted around at 80+ mph, 4-blade prop whining like an 18-wheeler's tires on a straightaway. At those speeds, his nosewheel rode far lower than his mains, because the HTL (no H-stab) was trying its damnedest to flip him out of the sky. But it never did.)
 

phantom

Newbie
Thanks Doug, I never thought about the top speed of ultralights, I did everything I could to cut drag on my 503 powered dominator and it will go over 100 mph in level flight but I do have the 72 inch two blade prop pitch set to where the engine will reach 6300 rpm at 90 mph.

Norm.
 

Boots

Active Member
Erik,
My bee has 23' dragon wings and flys good with a 200+ lb pilot . The 447 works for me .
I had a 503 but the light weight 447 was the better choice to keep the gyro Ultralight.
 

rcflier

Junior Member
Doug, I stand (sit, really) corrected.

So there are other reasons for three blades - I never thought that.

Rodney, I'll see, if I can make a swap for Dragon Wings locally (although I like fiberglass better).

Cheers
Erik
 
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Doug Riley

Platinum Member
Erik: Dragon Wings are fine if you have a prerotator. If not, you may find them difficult to hand-start, and prone to hard flapping at rather high RRPM. Ask Boots how he manages with his.

I have Rotordynes for my 'Bee, although I like DWs very much on machines with prerotators.

I hand-started the 28-foot DW's I had on a big tandem Dominator a couple times, but it wasn't pretty and it took forever before they would "catch."
 

rcflier

Junior Member
Hi Doug.

I just got a green light to build a Gyrobee, both from the one responsible for
all hardware and from the one who has to oversee and give me a thumbs up
on my build. So I am finally getting started!

He wants me to keep my Skywheels and engine. He flies a low rider Air
Command with a set of Dragon Wings - brave man. Well, he has the skills.

So now all the pieces are starting to come together. My home shop with lathe,
metal band saw and tool mill plus the expensive parts I already have. And my
small piece of land, large enough for a gyro.

Cheers
Erik
 

rcflier

Junior Member
I just said "No, thank you" to the IVO prop.

The blade steel protection gaped, so I didn't dare buy it.

If I had to buy one right this moment, it would be a Warp Drive.

Because it's so rugged. But noisy, right? I'll have to fly over a noise meter
as part of the certification.

But how about this "Kharkov" propeller? (Dealer: Meglinsky and sons):

http://www.rotaryforum.com/forum/showthread.php?t=44928

The scimitar blade shape and thin tip might make less noise.

And maybe be a bit more efficient?

Cheers
Erik
 
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PW_Plack

Active Member
If I had to buy one right this moment, it would be a Warp Drive. Because it's so rugged. But noisy, right? I'll have to fly over a noise meter as part of the certification.
I doubt the tip style of the prop has as much effect as the close proximity of the tips to the keel as they pass the frame. There might be a simple, lightweight shape which could be added to the keel right where the prop passes to reduce the noise signature.
 

Resasi

Gold Supporter
For the Hornet, basically a drop keel Bee, I chose a Warp drive 63’' three bladed prop on a 503 DC DI with a ‘B’ box. Used 23’ DW’s and a light electric prerotator from Aviomania.

Having crept over the 254lbs it then went Experimental. It flew well and performed nicely.
On static tests it pulled 319lbs which seemed reasonable.

https://www.youtube.com/watch?v=IhUDbQxLgOY

P.S. The squeaking sound was the swivel chair my son was sitting on in the hanger while he was videoing this.

On hot days at Zephyrhills with max (ten gallons) fuel it was struggling

Sadly for a number of reasons my son and I parted it out. (still have the electric prerotator.)

The 52’’ 3 bladed IVO and 503 I had on the Bensen in England was insufficient to do more than training, high hops and low 500’ circuits in cool temps, generaly to be had in the UK.

The 503 was changed to a 532, and the IVO to a 4 blade Arplast which then upped the static thrust to around 290lbs and produced a lively and very nimble little machine which was a joy to fly.
 
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rcflier

Junior Member
Hi Leigh. Thank you for dropping in.

I may make my own electric prerotator. And I know someone
who really knows both electronics and programming.

But, if I am swamped with the work of getting parts,
building and earning my license at the same time,
what would your Aviomania prerotator cost?

Cheers
Erik
 
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