Prop circles

[Downeaster]

My Flexofold 3-blade saildrive prop (20") has some etched 'circles' on the blades (see photo below). They are not deep - maybe the thickness of a fingernail at most. But too deep to buff out.

I assume they are from barnacles that were attached for too long? Anyone have other ideas? Is it ok to leave them or should I have them filled somehow?

[HopCar]

My first thought was cavitation damage. I know very little about it but it can do serious damage. https://www.dmsonline.us/bubbles-are...er-cavitation/

[Downeaster]

Thanks for the link. Yes, I was wondering about that too. But the circles are not in any sort of regular pattern and some are close to the hub. I don't know much about cavitation but it sounds like the artifacts would be in a pattern and consistent from blade to blade. And to have a few near the root of the blade seems inconsistent with cavitation also? I really don't know - just trying to conjecture.

[Orion Jim]

I’ve seen one or two over the years. I just sanded them out. Never saw one reoccur in the same position.

[Downeaster]

Yes, the positions are definitely random. All three blades, both sides, random pattern including some near the hub. Most are too deep to sand out, I'm afraid. Most were fair to the surface and not even noticeable until I cleaned them up.

I'm hoping that they will be faired and protected when I coat with prop paint. This assumes I don't have a serious issue I'm not understanding.

Any other thoughts or ideas anyone?

[HopCar]

Show it to a prop shop and see what they say.

[Adelie]

Originally Posted by Downeaster

My Flexofold 3-blade saildrive prop (20") has some etched 'circles' on the blades (see photo below). They are not deep - maybe the thickness of a fingernail at most. But too deep to buff out.

I assume they are from barnacles that were attached for too long? Anyone have other ideas? Is it ok to leave them or should I have them filled somehow?

Aliens.
https://www.cruisersforum.com/forums...ne-244538.html

[Cheechako]

Barnacles is my guess. You could paint the prop with bottom paint. It's marginally protective, possibly retarding growth a bit, but couldn't hurt. It seems to stay on in those areas but not up to maybe 1/2" from the edge.

[Downeaster]

I talked to a prop shop and they also thought it was from barnacles left to long on the blades before I purchased the boat. No pink ruled out galvanic/electrolytic corrosion. Cavitation is typically towards the edges and apparently unlikely at sailboat speeds anyway.

I'll put some sort of coating on it and see how it fairs.

[Sailmonkey]

Those are, like crop circles, coded communications from an alien species.

[Downeaster]

I was a bit worried about mentioning it, but on one of the blades the circles are in a very particular pattern that exactly matches a constellation in the Andromeda Galaxy. That one also glows in the dark, btw...

[Sailmonkey]

Originally Posted by Downeaster

I was a bit worried about mentioning it, but on one of the blades the circles are in a very particular pattern that exactly matches a constellation in the Andromeda Galaxy. That one also glows in the dark, btw...

See....that makes way more sense than barnacles!