Some advice on propellers please

[mwilli7119]

You guys have been great and I appreciate all the help.  My VE is coming along nicley. With a little luck I will have a 30th anniversary edition at Osh Kosh or Rough River or both.

I have a Great American prop and the old aluminum spinner. My first inclination is to get the plane in the air with these and change them later if I want to. But on the other hand it won't take very long to order a new prop and composite spinner.. after all it's only money.

Anybody have any advice on what i should get if I change? 2 blade? three blade? what manufacturer. Will I get any weight advantage to speak of by going to something new? etc. etc etc.

Mike Williams
Franklin, TN

[Dan Patch]

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I have a Great American prop and the old aluminum spinner. My first inclination is to get the plane in the air with these and change them later if I want to....

I'd go with your first inclination.  Optimizing your prop is something that takes a lot of knowledge about your particular airplane and engine combination, how you intend to fly the plane, your field length and its elevation, etc. etc.  It's not something that can be done easily before flying for quite a while.  Get flying, gather that data, talk to other VEZ pilots, monitor the forums, and THEN begin to think about your "perfect prop".  Of course, this advice is predicated on getting acceptable static rpm per the manual, checking the acceleration rate during the initial taxi tests, and anything else you can think of to be confident that your GA prop is a reasonable match to the plane/engine.  At this point, there's no way to take even a wild guess if your current GA prop is even in the ballpark since you didn't give any info. on its diameter and/or pitch.  

I'd suggest that you leave the spinner on the bench for initial testing purposes.  It isn't nearly as useful on a pusher (very minor top end speed improvement - if you are lucky).  All it adds at this stage of the game is extra maintenance hassle, weight where you absolutely need it least on a VEZ (unless you have one of the only VEZs to ever be built nose heavy), and a minor degradation in safety (sure can shake things when it starts to come off!).  If you just can't stand the look of the plane without a spinner on it from day one, I'd suggest rethinking your priorities.  


But on the other hand it won't take very long to order a new prop and composite spinner.. after all it's only money....

It won't take long to ORDER it, but the WAIT for delivery can be considerable, depending on the prop maker.  It took roughly 6 months to build and deliver each of the three props I've owned.  


Anybody have any advice on what i should get if I change? 2 blade? three blade? what manufacturer. Will I get any weight advantage to speak of by going to something new? etc. etc etc....

This is a huge topic without a definitive answer.  Check old posts on the canard-aviator forum to get a flavor for the issues and your options.  Obviously, a three-blade will be heavier that any reasonable two-blade.  Modern props are close to the weight of old props, although the thin, multi-laminate construction that GA used (they aren't in business anymore & I have one) is somewhat heavier than "average".  The lightest spinners are always found sitting on the bench.      

[Anonymous]

Anybody have any advice on what i should get if I change? 2 blade? three blade? what manufacturer. Will I get any weight advantage to speak of by going to something new? etc. etc etc.

Mike Williams
Franklin, TN

If you have made some serious airframe or speed mod changes. Probably best to use what you have now and have a baseline.  Props can vary by manufacture also. I have a 62X62 on my Long now. I spun up a 62X66 a few months ago hoping for less static Rs and a goose in cruise. Damn thing spun up to 2500Rs static about a long 100 more than my current prop and there was no need to test fly it.

Personally, I would stick with a good 2 blade.  Main reason you see heavier tin with more than 2 blades, they need to absorb more HP and ensure enough ground clearance.

Might check around with other EZ drivers and possibly borrow a bigger prop to spin up and see what she does.

Good luck;

Jack

[Dan Patch]

Props can vary by manufacture also....

This is definitely true - for a number of reasons, some of which are that there are various (at least 3) different ways to measure propeller pitch, blade chord makes a difference, as does pitch distribution, airfoil shape, blade shape, tip profile, etc, etc.  


I have a 62X62 on my Long now. I spun up a 62X66 a few months ago...

My "best" prop is an old Bruce Tiffts 62x66 intended for O-235 LEZs.  Given the smaller size/weight of the VEZ it proved to be a good match for my O-200 VEZ.  My other prop is a Great American 62x62.  The numbers suggest that it will be more of a climb prop than the B&T.  Wrong!! (see above for why).  


Personally, I would stick with a good 2 blade.  Main reason you see heavier tin with more than 2 blades, they need to absorb more HP and ensure enough ground clearance...  

I would also stick with a good 2 blade, but there are many fans of the 3 blade for its smoothness.  Theoretically, a 2 blade has less blade-to-blade interference and so can be (slightly) more efficient than a 3 blade configuration.  Regardless, the difference (2 vs. 3) is generally small, and a very good 3 blade will out perform a "not quite as good design" 2 blade (and vice versa, of course).  Jack's right about the main motivation for more than two blades being power absorption for the big guys.  I think that, given the extra weight (and cost), a 3-blade prop is even less attractive on a VEZ than a LEZ.  


Might check around with other EZ drivers and possibly borrow a bigger prop to spin up and see what she does.

Borrowing various props to test is definitely a good idea.  Trying ten different props by buying them one at a time is a slow and costly process!  A lot of prop builders will work with you to get your prop right, but you have to be reasonable about what you expect them to do for you for free.  

Step one is to finish the bird!  Step two is to get a good set of baseline performance data for a reasonable prop.  Step three is to decide what you want to improve (i.e., emphasize, such as, climb, cruise, speed...).

Good Luck!

[mwilli7119]

all good advice. thanks.

[mwilli7119]

With an O-235 Varieze? What does anyone think? What should I expect when I fly in the spring.

[TIM BAILEY]

If you don't use your Great American prop, I will take it off your hands, been looking for one for my Vari-Eze for years. I have a Hendrickson that has given me 20 years service and 175mph S&L at sea level.