I have an aircraft that I support that needs a lot of propellers. The aircraft is called a Pixy Drone, an RC parasail(foil) controlled unit powered by a 23cc (1.4cu In) Bergonzini Boss Tech engine. It is made by ABS Aerolight. The unit is used in a rough environment, and anything that hits the prop (grass, corn cobs, small stuff, almost exclusivly on take off) nicks or breaks the prop, leaving them a problem to use. So far, we replace, but this is really starting to hurt cash wise. The engine can spin up to 17000 RPM, but with this style prop, its known to spin between 7600 - 8200 RPM.

The props are listed as 17X4, and have a 3/4" bore for the drive shaft. The actual prop length is 16 and 5/8 inches, with squared off tips. Its a wood laminate (5 ply) and looks to be Maple and Black Walnut. The maker tells me its made on a computer driven lathe from CAD CAM drawings and design of his own.

The props are a huge expense, even more now that the company that makes it is European, and the rate is today 1.17 USD for each Euro. I see several makers of props, glass and carbon fiber, and attactive prices, but non with the same pitch. Also, nobody seems to list the bore either, and I'm thinking of a drill press to adjust. I am aware of changing the size and pitch tradeoffs, and am thinking its worth the try to go with a smaller diameter prop (better ground clearance) and a greater pitch (only 6 and 8's are in the US market that I can see) and still get comparable RPM's and perhaps the thrust needed to basically work this thing. Does anyone have any pointers for making this change? Any suggestions for good props in US for better prices than $141.00 USD?

Here are a few 16 x 6 (the bore can always be drilled out)

http://www.desertaircraft.com/bolly.html

http://www2.towerhobbies.com/cgi-bin...?&I=LXLW12&P=0

http://www2.towerhobbies.com/cgi-bin...?&I=LXE654&P=0

http://www2.towerhobbies.com/cgi-bin...?&I=LXZ985&P=0

I'd worry about boring those props out to 3/4" diameter. But for the price, you could by a dozen and still come out ahead. There may be a way to reinforce the hub, but I'm not certain. Buy one and give it a try. Just stand back.

Kerry

Thanks for the leads. I'm doing a crash course as we speak, using the Bolly Manual, and its very illuminating. What I have learned is that the props we have are basically good props for this application, and are universally known to be expensive. I think carbon fiber is the best thing as an alternative, and think the characteristics might just be fine.

-Charlie

You could also make your own by hand, with the right tools and a bit of practice it's it's not that hard.

or make the blanks and have your local tool shop plot a CAM program off one of the originals, first set up may be a few $$$ but after that it should be cheap

What a good idea this is, to plot one out at the machine shop. I've checked in with a couple of places, and they think the cost effectivenss might not be there with the CAM/Machine shop route, but the spreadsheet tells me it is after 15 props are made. I think the Zinger props are going to be the first and maybe only manufacture that I can order something comparable. I have a lot of issues, as you can see, pusher props, plus a non-standard bore hole in the hub. Thanks again.

Have you thought about turning down the propshaft diameter to a more standard size? That would be a lot easier (and cheaper) than the custom prop route...After all, how much real difference is there at the prop between your engine and a G-23?

The difference is almost non, from what I can tell. I'm working this angle as well. I guess I am in the right forum, beginner for sure, tossed into a world I had not really known before. I have now discovered there are bushings holding the the big bore prop in place, taking up the gap between a smaller drive and the prop itself. Things are looking up for access to pusher props on the general market.