Effect of barnacle clad prop when sailing

[pcatterall]

Well, I know the effect when motoring..... a disaster ...top speed cut from 7 to 4 knots!

Thie boat has overwintered in the water so this spring we will go out ( to Sardinia) armed with my new bore scope and tablet viewer and try some scraping with a pole!!
But my question is what is the effect of a big cluster of barnacles on my 3 bladed prop when sailing? I think the prop when clean has up to half a knot of drag so suspect that that a big wadge of barnacles wil have considerably more effect?

 

[William_H]

No I don't think the barnacles on the prop will make drag much worse than a clean prop. That is assuming that the barnacles don't make the prop any bigger in diameter.
However it is likely that the rest of the hull will have been fouled so slowing it down.
I would advocate you get in the water with a mask and snorkel (plus gloves and a scraper) and clean the prop, and check the hull at the same time.
In moving the boat you might need engine power so you really need to clean that pro. good luck olewill

 

[KenMcCulloch]

I think if there are enough barnacles on the prop to increase the drag under sail, the prop itself will have become next to useless at its own job. Toward the end of last season I noticed a marked reduction in drive particularly when manoeuvring (as oppposed to simply motoring ahead) under power. It was little surprise to find a fine colony of acorn barnacles around the boss of the prop. Scrape them off!

 

[JumbleDuck]

Thie boat has overwintered in the water so this spring we will go out ( to Sardinia) armed with my new bore scope and tablet viewer and try some scraping with a pole!!
But my question is what is the effect of a big cluster of barnacles on my 3 bladed prop when sailing? I think the prop when clean has up to half a knot of drag so suspect that that a big wadge of barnacles wil have considerably more effect?

I would expect it have negligible effect with the prop locked but a substantial effect if you normally sail with the prop spinning free.

 

[TQA]

TOP TIP

Fix your scraper to a 6 ft pole.

Now you can do the job from the surface using your snorkel gear as before.

> 10% of the effort you need when diving.

 

[jac]

I think if there are enough barnacles on the prop to increase the drag under sail, the prop itself will have become next to useless at its own job. Toward the end of last season I noticed a marked reduction in drive particularly when manoeuvring (as oppposed to simply motoring ahead) under power. It was little surprise to find a fine colony of acorn barnacles around the boss of the prop. Scrape them off!

Does an encrusted prop make prop walk worse? I can understand that it would reduce the drive so as a consequence it might take longer to get sufficient flow over the rudder to get steerage but does it also make the stern walk sideways more due to the increased surface area on the prop going sideways

 

[Ruffles]

I've found that an encrusted prop reduces speed by very little in flat water but often by half or more when you hit some swell such as poking your nose out of Portsmouth entrance. On one occasion I lost steerage way. Very embarrassing.

 

[Resolution]

TOP TIP

Fix your scraper to a 6 ft pole.

Now you can do the job from the surface using your snorkel gear as before.

> 10% of the effort you need when diving.

Thanks for that. Have noted and will try it in three weeks time. I hate cold water!