keel in the mud

[sailhog]

I know there was a similar thread to this one running a few weeks ago, but my situation is a little different and I wanted to register everyone's response.

I have my 27-year-old Catalina 30 parked in a slip on Hilton Head Island. The tidal action is fairly radical here, with the range running around 9 feet during spring tides. While down at my boat during a particularly strong spring tide, I noticed that the water depth at my bow was about two feet, and about three feet at the stern. There are several sailboats around me, and the owners seem utterly unconcerned with depths, as the sea floor is this very light pluff mud. I can't emphasize enough just how light the mud is here, but it's lighter than the quicksand on Gilligan's Island -- it's like talcum powder. My concern not only has to do with what it does to the paint, but what it does to the rudder. The embarkation point for the Dafuskie Island Ferry is just half mile away, and it does throw up a bit of a wake. I rent the space for $225, and it would cost nearly twice that at Skull Creek Marina, which is a half mile in the other direction. Do I need to move my boat? I'm thinking I need to move it...

[sailhog]

I'm waiting for an answer! What's wrong with you people?

[sailingdog]

Ummm... you're an impatient little piggy...

You don't say what the draft of your boat is... or whether it has a spade rudder or a skeg-mounted rudder. If it is a spade rudder, I would be more worried about it than if it is a skeg-hung rudder. If your draft is more than four feet, then I would probably recommend moving to a different marina... part of the problem of being in mud is that you can get some serious corrosion problems due to the oxygen deprivation caused by being embedded in mud. You also don't say what kind of sailboats the others boats are... they may not be concerned because they may not need the same depth that you require. If their boats are swing keel, keel-centerboard, or twin keelers, then they may not need more than three feet of depth.

[sailhog]

I HAD TO WAIT ALMOST 14 MINUTES! Sailhog, of course, was thoughtful enough to responde first.
The draft is 4'4" and its a spade rudder. The other boats around me all have fixed keels and draw at least two more inches. The waterline on one of them looked like it was raised during that low tide. It is definately hard aground.
Thanks, Sailingdog

[sailingdog]

I'd be worried, since spade rudders have little support beyond the rudder stock itself... and generally aren't designed to resist vertical forces well... A skeg hung or keel-hung rudder has a lot more support in some ways, not being freestanding and having the keel or skeg take a fair bit of the vertical loading when you're aground...

I guess it depends on how risk tolerant you are... are you willing to risk the lower marina payments against the eventual cost of repairing/replacing the rudder... if so... then keep the boat where you are... If the cost of repairing/replacing the rudder is low enough, it might still make sense to keep it there... but then there is the loss of use, and the possibility that the rudder will be damaged and not fail until your out on a sail... and then all bets are off... In that case, I would say it might be worth spending the extra bucks and getting a slip that doesn't leave you aground.

BTW, in England, it is pretty common to have slips that leave you completely dry, and that is one reason twin keelers are so popular there. They can stand to dry out and not take any damage, provided the bottom is mud or sand, since they can stand on the twin keels. The keels are usually deeper than the rudder, so the rudder has less risk of damage.

[Faster]

Easing the keel and even the rudder into some supersoft "pluff" mud occasionally is not, itself a big cause for concern. This is not something that's likely to happen everyday..

However if the waterlines are up, then you are indeed hard aground, and now there's more of an issue, obviously. A Catalina 30,left to its own devices, would in all likelihood tend to nose down when hard aground, so the rudder may not be in serious danger. But you're tied to a float, and now your boat may begin to support the float and that can lead to issues with loading on cleats, stresses from the side pull etc. as the float upsets the balance.

I'd say there's a reason why your current slip is less expensive! Maybe move for now and get on a wait list for a better slip at your present location?

[sailhog]

The mud is soft enough that I don't think the vertical stress is a problem. I guess my concern is for lateral stress that would occur when the water taxi does his 180 at his dock a half-mile away because the mud is so soft. I think there's only 4-6 inches of rudder sticking in the mud at the lowest tide, and it is extremely light stuff.
Thanks again, Sailingdog. I appreciate your time and expertise.
Sailhog

[sailingdog]

How much shorter than the keel is your rudder?? also, Faster's point about the cleats loading in directions that they're not designed to take loads is a valid one.

[sailhog]

It's funny that Faster mentioned that, but it's not a problem, as the tide was so low that the dock itself was aground and created slack in my dock lines. No one around here had ever seen the water as low as it was then. This was about eight or nine days ago. It's like the water had been sucked out of the creek by something other than the sun and moon...

[sailingdog]

The flying purple people eater was migrating and got thirsty???