In a recent thread, I posted a dilemma with my Hirth F-33/Powerfin 56 inch B model prop and what seemed to be lower than appropriate static thrust.  The responses I got suggested that I needed a bigger, narrower blade prop, in the 60 or 62 inch diameter range.

I was able to try an Ivoprop and Warp, both 60 inch, and achieved about 155 lbs thrust - about 35 more than the Powerfin.

I probably have a new prop in my future - any strong opinions between Ivo and Warp?  I think I want something ground adjustable.  I guess I could consider a fixed pitch wood prop.

Any advice greatly appreciated!

Ernie Luce, AirBike 77, San Antonio, Texas

Fixed pitch wooden props are lighter and less expensive. Belt drive or gearbox will last longer with a lighter prop, and throttle response will be quicker. If you have to have or just want a ground adjustable, I would reccomend one with infinitely adjustable blades. Wooden blades can have minor damage repaired easily, composite blades will withstand a little more abuse, if they are solid.

What is the ratio of your belt drive?

Thanks Bill

Belt drive 2.5 to 1.

Thanks, Ernie

Based on a program Called PropDesign that I down loaded from http://www.nicon.org/chapter328/PropDesign/  I came up with these numbers:


Hirth F33 Cruse @ 75% Power with 62 inch prop and Est speed of 53mph @6000 Ft-MSL

Ratio     RPM          tip speed HP     pitch     Chord   thrust     efficiency    
   
1.8:1     2500/4500  676.3  19.5     28         4.1     98     70.8%
   
2.2:1     2045/4500  553.2  19.5     34.8      6.4     97     70.6%    

2.5:1     1800/4500  486.9  19.5     40          8.6     96     69.8%

The pitch seems way out except for 1.8:1 ratio    

Thanks for your help!

Ernie

Hi all,  I've flown with an IVO on my Himax, then a GSC when I wrecked the IVO and then back to an IVO because I thought the IVO was a better prop.  (three blade 60")  I have even switched from a Powerfin  to an IVO on my Avid.  I've heard the warp drive props are very strong but that they are heavy.  Another thing I like about the IVO is that all you have to do to adjust it is turn the bolt in the center and all blades are adjusted at the same time.  Adjusting the others is a real pain.  I've never flown with a Warp drive but from my experiences with IVO's and what I've heard about Warp drives,  I would for sure go with the IVO.  Just my two cents worth.  Jim

Thanks for the input!!!

I had a warp on my old quicksilver - and they are tricky to get each blade adjusted the same.  Seem to be a good prop though.

The ivo (that I have borrowed for my AirBike) sure is smooth - smoother than I ever got the powerfin adjusted.

Ernie

I built a device that fit on the prop blade and held one of those small lazers.   It will project a line accross the hangar to somewhere on the wall.  I would mark the spot and then put the lazer holder on the other prop blade and adjust it to hit the same spot.  You could move the lazer dot 1/4" at 30', not sure of what that amounts to on a 4" wide prop blade, 1/10 of a degree???  but it sure seemed that the blades all ended up at the same setting.  It still isn't near as easy as adjusting the IVO.  Jim

After much thought I finally ordered a Powerfin (I wanted the wider blades because I had to use a smaller diameter than I really wanted). According to claimes, its rotational inertia is less than the other brands, which is also important to me. I liked the idea of the adjustability of the Ivo, but they are heavy, and as someone said to me...if one of those CLUBS hits the ground, you can kiss your crankshaft goodbye. Powerfin claimed theirs would break before taking the crankshaft with it.

Thanks - I was told the wide blades were part of my problem with the low thrust.  I agree with the low weight and breakability of the Powerfin.  28 hp is probably marginal, so I will probably go for the increased thrust from one of the clubs.

Thanks!

Ernie