Unloading a prop and Prop Diameter reduction help.

[Samuel Hagan JR]

Doing a Barr Cut or Lynx cut helps unload the prop doesn't it.

Also when you reduce the diameter do you keep it the shape of the blade or do you keep the area you take off alone.

 

[shoboat]

Sam,

Good questions. When you reduce the diameter of a propeller you also change the

pitch ratio of that propeller. It goes higher up depending on how much you cut off.

So if you are cutting down a X-455 to say 52 mm the pitch ratio increases and is no longer

a 1.4 pitch ratio. Now the backcuts do a lot of different things on different boats. On some

monos the Lynx-cut has less lift than a Barr-cut. You are taking away a certain amount of

blade area ratio with the backcut. It also helps the boat corner better because when the boat

drops just a little in the corners it flows water thru the hub area. With less blade area, diameter, less pitch, or less cup it will also change the lifting characteristics of our boats.

Only one good way to find out what these changes make to our boats, go out and test them

in good water and document the changes from your baseline set up. Less blade area also

increases the RPM and it helps the pipe work better and be more responsive to our pipe changes. It can allow for a shorter overall pipe length change and give you more RPM and speed. If I was you get a good pitch gauge and then you will see what each change does to your set up.

When I reduce the diameter on any blade, I blend the whole leading edge proportionally.

Just cutting off the tip is not the best way to do it. Make sure you rebalance it again even if you are

Cutting it down on a lathe like I do.

Thanks,

Mark Sholund

 

[lohring]

Excellent advice. A summary of the basics of propellers can be found in my Props articles in the October 2013, April 2014, and April 2015 NAMBA Propwash.

Lohring Miller

 

[Michael Caruso]

Excellent advice. A summary of the basics of propellers can be found in my Props articles in the October 2013, April 2014, and April 2015 NAMBA Propwash.

Lohring Miller

Guy's, I printed out Lohring's article and re-read it picking up something I missed or my brain did not save each time. Lohring thank you so much for suppling tools for me to learn from. I want you to know it has been appreciated by me at the very least.

Mike Caruso