Propeller ice guard

[Paul Bradshaw]

Hello, I have an ice guard on the propeller on my tug. The guard sorrounds the prop but does not extend over it. I am told I will get a little more speed if I extend it to sorround the prop. Can anyone tell me if this is true and if so how much of a gap should there be from the tip of the prop blade to the ID of the guard?

[BobS]

If you extend your ice guard so that it becomes a propeller duct, you might indeed get a bit extra bollard pull out of your tug. However the duct would need to be very close to the tips of the propeller blades so as to reduce tip-vortices.
While - assuming you get the diensions right - you might increase power when towing, it is likely that the duct will create extra drag when sailing at speed, and steering stability may also be adversely affected.

[Paul Bradshaw]

Thanks for taking the time Bob and for the invaluable information.