Armed Polite Society

Main Forums => The Roundtable => Topic started by: Ben on August 25, 2019, 07:47:29 PM

Title: Here's One Way to Clean a Sailboat Hull
Post by: Ben on August 25, 2019, 07:47:29 PM
I bet this got their hull clean!  :laugh:

Pretty cool. I've never seen this before:

https://youtu.be/PEsHLSFFQhQ

https://www.foxnews.com/science/pumice-raft-save-great-barrier-reef
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: RoadKingLarry on August 25, 2019, 09:23:03 PM
I've seen several videos of similar events on the sailing forums.
Wow. I think I would seriously consider a reroute if I were to encounter something like that, too much potential to disable the boat and you sure as hell couldn't run the engine.
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: Hawkmoon on August 25, 2019, 11:38:13 PM
I don't even want to think about what that's doing to the gel coat if that's a fiberglas hull.
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: dogmush on August 25, 2019, 11:55:20 PM
Meh.  It's not all that bad.

The rocks are light, and they're going slow so they mostly just push out of the way.  There's not even much gelcoat damage because the rocks just get nudged out of the way.

Not pumice, but I've nosed my way carefully through floating rafts of all kinds of stuff.  Ice, logs, trash, fishing gear, once a bunch of fiberglass.  Just go slow, and if you see something go under the hull instead of around it, drop it in neutral and coast for a bit.
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: TommyGunn on August 25, 2019, 11:59:45 PM
Isn't that what the captain of the Titanic tried to do??  ??  ??  [tinfoil]
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: dogmush on August 26, 2019, 05:30:04 AM
Isn't that what the captain of the Titanic tried to do??  ??  ??  [tinfoil]

He skipped the "Slow Down" step.
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: RoadKingLarry on August 26, 2019, 05:51:38 AM
Meh.  It's not all that bad.

The rocks are light, and they're going slow so they mostly just push out of the way.  There's not even much gelcoat damage because the rocks just get nudged out of the way.

Not pumice, but I've nosed my way carefully through floating rafts of all kinds of stuff.  Ice, logs, trash, fishing gear, once a bunch of fiberglass.  Just go slow, and if you see something go under the hull instead of around it, drop it in neutral and coast for a bit.

I'd be more concerned with with sucking up abrasive debris into my raw water pump. The story in the OP also mentioned that a sailboat had gotten debris wedged into there rudder and causing it to jam.
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: dogmush on August 26, 2019, 06:06:56 AM
I'd be more concerned with with sucking up abrasive debris into my raw water pump. The story in the OP also mentioned that a sailboat had gotten debris wedged into there rudder and causing it to jam.

Boats differ, of course, but those pics looked like a couple of inches debris at the most.  The raw water intake should be lower than that*, plus you have (usually) at least two levels of straining before the heat exchanger.  Most sailboats (as I'm sure you know, but for the benefit of others) have large rudders with the top at or near the waterline.  Much easier to get something jammed between the top of the rudder and the hull then powerboat rudders, which tend to be deeper and with more space around them.

That said, standard practice for something like that (if you can't skip it) is to slow down (not a problem on a sail boat) and kinda coast straight through.  Most of the time you'll be fine.  I bet they were swinging their rudder back and forth (or didn't disable the autopilot) and that's what got it jammed.

*At normal draft, my main seachest is at about 10ft below the waterline.  We suck stuff up pretty frequently, but just clean the strainers.  An ocean going vessel, even a small one, should have a duplex strainer on anything important so if you clog it, you just switch to the other side and keep trucking while the first one gets cleaned.  I was hanging out in a river once that was so silty, the strainers were clogging as fast as you could clean them, so the snipes were down there just constantly rotating clean, switch, clean, switch. Long day for them.
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: RoadKingLarry on August 26, 2019, 06:26:15 AM
The raw water intake on my ketch is only about 24" or so below water line, It has an external strainer and then runs through a wire mesh filter. That pumice island would be like sailing through sand and gravel. The fine crap would get in and the big crap would clog the strainers
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: Hawkmoon on August 26, 2019, 12:10:34 PM
Most sailboats (as I'm sure you know, but for the benefit of others) have large rudders with the top at or near the waterline.  Much easier to get something jammed between the top of the rudder and the hull then powerboat rudders, which tend to be deeper and with more space around them.


So you are assuming that "most" sailboats are not full keel hulls, with an upper and lower pivot for the rudder? I concede that a lot of newer sailboats are made that way, but I am not prepared to go so far as to say "most." I know that for coastal cruising in Maine I wouldn't have anything other than a full keel design, due to the hazard of running over lobster pot tackle.
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: dogmush on August 26, 2019, 01:15:59 PM
So you are assuming that "most" sailboats are not full keel hulls, with an upper and lower pivot for the rudder? I concede that a lot of newer sailboats are made that way, but I am not prepared to go so far as to say "most." I know that for coastal cruising in Maine I wouldn't have anything other than a full keel design, due to the hazard of running over lobster pot tackle.

No I'm not.  I'm saying that most sailboats (Full or Fin keel) have less space between their running gear and hull and have rudders that get closer to the surface than powerboats of an equivalent size.

Quote
The raw water intake on my ketch is only about 24" or so below water line, It has an external strainer and then runs through a wire mesh filter. That pumice island would be like sailing through sand and gravel. The fine crap would get in and the big crap would clog the strainers

That's probably 20" below any of that floating rock.

That raft's miles wide.  It's not like you're going to just huck a starboard turn and go who knows how many miles out of your way.  Boats tend to have places to be.  Put that thing at Dead Slow ahead, put a lookout on the bow, and limit maneuvering until you're through. 
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: MechAg94 on August 26, 2019, 03:33:45 PM
I recall seeing some show (What on Earth?) where they talked about Satellite images seeing an island in that area that wasn't there later.  I don't recall them mentioning this possibility. 
Title: Re: Here's One Way to Clean a Sailboat Hull
Post by: 230RN on August 27, 2019, 07:17:36 AM
Ah, two things got cleared up:

(1)
*At normal draft, my main seachest is at about 10ft below the waterline."

Quote
On a ship or boat, what is a sea chest? - Quora
https://www.quora.com/On-a-ship-or-boat-what-is-a-sea-chest
A sea chest is any chamber inside the volume of the hull form which can flood and not be considered inside the hull. While sea chests often refer to water intakes they can also include spaces for instrument packages. This page written by Andy give...

(2)  I finally remembered from my rock collection in high school that pumice floats from all the gaseous spaces in it.  Ah, so.

Interesting phenomenon that it can form a raft.

Terry