flexable vs solid driveshaft question

[mofo]

Could someone tell me why flexable drive-lines are so popular, and not rigid? Just curious. Seems the shaft spinning so fast has to eventually break the flexable ones. Does it make-up for slight mis-alignment problems? Is it that hard to keep a straight shaft true?Thank you in advance. Just a new guy trying to figure it out.

[kendt]

The flex shafts are quite tough as long as they are set up right. The main advantage is the ability to run surface or sub surface drives. As well as the ability to adjust the angle of the propeller to help with tuning. A straight shaft points down on an angle, whether shallow or deep its fixed unless you use a u joint of some kind which add drag, and would have to be very strong (so heavy) to handle the power of brushless motors.

[longballlumber]

Just curious. Seems the shaft spinning so fast has to eventually break the flexible ones.

Actually, they are quite tough and I maintain the argument the Hughey brand shafts are the best.

Does it make-up for slight mis-alignment problems?

YES

Is it that hard to keep a straight shaft true?

YES - and difficult to support along the length of the solid shaft.


This topic comes up time to time... Flex shafts have been used for many years and have pushed some VERY fast boats (and still does).

Later,
Mike

[mofo]

Thank you for the replies. Mike, I read your tune-up thread on the Motley Crew boat. Very helpful for a new guy like myself. I read about your faith in the Hughey shaft. It was one of the reasons I started thinking about the shaft design, and the reason I ordered a new strut bearing. I thought about pulling my stock one and drilling-out the grease retaining holes, but I had quite a shopping list when I finished your thread, so I threw it in the cart.