Finally, reduced prop walk on my E32-2!!!

[SteveL]

A number of you have commented thoughtfully as I tried to work through the problem of extreme prop walk on my E32-2. Yard guarantees not withstanding, a 12" 3-blade MaxProp did nothing to relieve the problem. However,building-up the propeller blades from 12" to 15" has made a night-and-day difference ($700). It's like a new boat.

I originally thought that I would have to modify the keel to get the prop to fit. However, the blades of the MaxProp attach to the stern-end of the hub (the part that actually sits on the shaft) and because the prop shaft is angled down sharply, that created additional space beneath the hull. There isn't much room between blade and keel, only about 1/2 inch, but there is minimal vibration and I have plenty of power forward and enough control in reverse. The blades must be feathering, too, as we reached 7 kts a couple of times in 15 kt winds.

Fred Hutchinson was the guy at PYI, Inc. who worked with me to solve the problem. I can't say enough about how helpful and responsive he was.

At last I have a vessel that walks like an ordinary sailboat. I am a happy sailor today!

Steve

 

[mherrcat]

Here is something I found on the Michigan Wheel website:

The clearance between the propeller blade tips and the hull bottom should be at least 15% of the propeller diameter and ideally, 20% or more. So for example, a 20” diameter propeller would have 3” minimum clearance and better still 4” or more. A common guideline for recommended propeller to strut or keel clearance is 20% of propeller diameter measured between the propeller blade edge and strut leg or keel. This is often measured at a point on the propeller blade edge about 70% of the distance from the shaft centerline to the blade tip.

Based on that you should have at least 2 1/4" of clearance. With only 1/2" I think you are probably hurting the efficiency of the prop or may even risk causing damage to the hull. The engineers amongst us can probably explain this.

 

[Loren Beach]

Rules vs "Guidelines"

Here is something I found on the Michigan Wheel website:



Based on that you should have at least 2 1/4" of clearance. With only 1/2" I think you are probably hurting the efficiency of the prop or may even risk causing damage to the hull. The engineers amongst us can probably explain this.

While it's a science, it's not an exact science. All adjacent hull shapes will vary. I have always heard that 10% of the diameter was a good clearance to shoot for, but less might be OK.
This might well be one of those situations.

Loren

 

[SteveL]

Fifteen percent is what Fred at PYI, Inc. initially said the clearance should be. But once I contacted him with the actual measurement, he kind of shucked and said it would probably be fine even with this amount, though more would be better.

I'm going to live (happily) with 1/2 inch for this season.