Tip Rounding

BobGutsell · Oct 1, 2011

I understand this is a way to get a prop to rev harder. A mate was telling me that rounding tips increases Lift. Is that true?

john addinall · Apr 18, 2012

hi there. as far as i know making the tips round you make less lift. cleaver props have rake degree's. a 10 degree rake will have more lift then a 15 or 20 rake prop. chopper series, round ear props is normally a low lift prop. to get a prop perform better, give it a back and barr cutt. that help for me.enjoy

john

lohring · Apr 18, 2012

Rounding the tips reduces the diameter. Very small diameter reductions will reduce the power requirement a lot.

Lohring Miller

hugh hargett · Jul 19, 2012

Yes, but whats the definate answer on what it does to the lift of the prop? BY reducing the said diameter dont you inheriently increase the pitch or not necessarily???? Does not a higher pitched prop have more lift as its blades lay flatter with respect to the waterline?

Jeff Barnhart · Jul 19, 2012

hugh hargett said:
Yes, but whats the definate answer on what it does to the lift of the prop? BY reducing the said diameter dont you inheriently increase the pitch or not necessarily???? Does not a higher pitched prop have more lift as its blades lay flatter with respect to the waterline?

Think about the thrust cone a little bit. Pitch is how far the prop moves forward in a rotation. As the water moves along a high pitch blade (i.e. moving more forward per rotation than a low ***** blade), you effectively shrink the thrust cone (i.e. smaller rooster tail). Props with a lot of lift generally throw a higher roostertail. This only general, blade shape is also a factor.

hugh hargett · Jul 19, 2012

I guess you dont increase the pitch by reducing the diameter on a said prop, per-say, but the pitch ratio ?????

Jeff Barnhart · Jul 20, 2012

The concept is almost like a gear in some sense, small gear=higher rpms, smaller prop=higher rpms. Bottom line is, the motor/engine needs to be loaded so that it is operating at the peak of its power curve. It's all about thrust vs. drag, you're trying to generate as much thrust as possible with as little drag as possible.