Intracoastal Marshes; Tidal Docking

[Pete7]

Originally Posted by Yellowtulip

I'm in the uk, and don't have good charts of that area, but it looks to me like much of our East Coast. A likely solution over here would be to drop a mooring in a pool that maintains the depth you need and use your dock for a tender to access it.
Bilge keel boats are common over here, as you mention, but they are a compromise in sailing terms. Bouncing up and down on a had bottom can obviously be problematic, too. Much depends on the nature of the bottom. If it's soft mud, that's probably the best thing, though that can also cause problems. It's been known for one keel of a twin-keeler to become stuck in mud causing the boat to be flooded by the rising tide. Very rare, I'm sure.
Lifting keels or centreboards are also common here. Soft mud can clog up the centreboard case or keel slot with these, and stones can be a problem too. Stony or pebbly bottoms can abrade glass-fibre quite quickly. There's no perfect solution

So how many of these terrible problems have you suffered on your boat, or is the above based on other peoples experience?

Meanwhile, nothing wrong with a bit of mud, supports the hull rather nicely

Pete

[SPC]

Pete,
Is that a centerboard boat? What's it's draft?

[Yellowtulip]

Originally Posted by Pete7

So how many of these terrible problems have you suffered on your boat, or is the above based on other peoples experience?



Meanwhile, nothing wrong with a bit of mud, supports the hull rather nicely



Pete

I had a fin keeled Achilles 24 kept in a mud berth in Rye with a 4'9" draft for years with no problem. That was VERY soft mud.
I had a friend who mistakenly left his centreboard down on a drying mooring. Goodbye boat.
I've witnessed a small boat being flooded by an incoming tide when it failed to rise. There were no holes in it.
I've heard of boats suffering hull damage from pounding as the tide rises and falls.
Westerlys had problems with the bilge keels spreading after long periods on drying moorings.
I did point out that problems are very rare.
You could make an equally long list of problems with any other type of mooring. I was just adding information for the OP's use.

[Pete7]

Originally Posted by SPC

Pete,
Is that a centerboard boat? What's it's draft?

She has bilge keels somewhere under that mud Had to find some choppy waves to wash her clean after we escaped from that harbour. Draft is 3'8" or 1 metre.

Pete

[flyingfin]

You will ruin the thru hulls and put pressure on the rudder every time she sits in the mud

[Jeannius]

Originally Posted by flyingfin

You will ruin the thru hulls and put pressure on the rudder every time she sits in the mud

No it's not ideal but thousands of Brits have been doing it for hundreds of years without the rudders falling off or the through hulls getting clogged.

[SPC]

I noticed a review that said the Gemini Legacy 35, by having fixed keels, would be an improvement for drying out over the centerboards on the 105mc. Why would that be the case? What are the reasons for fixed keels over centerboards in a catamaran?

[Jeannius]

Originally Posted by SPC

What are the reasons for fixed keels over centerboards in a catamaran?

Centreboards have to go up through the hulls. You have to dedicate space in the hull for that to happen whereas fixed keels don't intrude into the living space. For performance oriented boats centreboards or dagger boards have advantages of performance but not worth the hassle on a cruising oriented boat IMHO.

[Yellowtulip]

Originally Posted by Jeannius

Centreboards have to go up through the hulls. You have to dedicate space in the hull for that to happen whereas fixed keels don't intrude into the living space. For performance oriented boats centreboards or dagger boards have advantages of performance but not worth the hassle on a cruising oriented boat IMHO.

That depends on the type of cruising you want to do. If you like 'creek crawling', centreboards, being variable draught, have advantages over bilge keel boats as sailing performance is less compromised.
The centreboard can be partially or fully raised when exploring shallow areas so you can 'feel' your way as well as allowing the boat to dry out.

[Sand crab]

That Gem 105 MC that I had posted about earlier is on Google Earth. It's in Lay Inlet just west of the harbor in Gig Harbor, Washington. Lay Inlet totally dries out at low tide. I went back to a view from 2018 which shows her resting nicely on her bottom.

[SPC]

Cool view, Sand Crab.

So, if I were to do this, what sort of modification would be desired for the dock; e.g. installing stout pilings? Look at my photos for the existing setup. Would it be better to park along the tiny platform where there's still a few inches of water at low tide, or next to it, which dries out but would be more out of the way?

[Sand crab]

I don't think you would want to park in front of the dock because then you would be tipped sideways. Usually you pull straight in towards shore when beaching so on the side of the dock would be best, easiest and cheapest. The dock in the pic is pretty basic as are all the other docks there, just like yours. Some are only connected at the shore and the rest just floats. The problem with this is you would be in shallower water and be a slave to the tides. The area shown has really large tidal swings so there can be pretty deep water in there. Perhaps you can park straight into the dock and tie off to either side which may require dock reinforcements. Or you put pilings out in front of the dock that would allow you to pull in between them and still step off the front.

[valhalla360]

Originally Posted by SPC

I noticed a review that said the Gemini Legacy 35, by having fixed keels, would be an improvement for drying out over the centerboards on the 105mc. Why would that be the case? What are the reasons for fixed keels over centerboards in a catamaran?

In terms of drying out on a low tide, if the mud is soft, the mud can cram up into the box making it difficult to deploy the boards once afloat. That won't be an issue with fixed minikeels.

Plus, fixed keels are typically solid fiberglass, so if they sit down on a rock or log, the keel will at worst get a scrape on it while distributing the load to the hull over a wider area. With centerboard, the relatively thin hull is sitting on the bottom, so a big rock can create a point load which can puncture the hull.

In terms of sailing ability, retractable boards will typically win out (all else being equal) as you can deploy what you need when you need it. Downwind, you can pull them up reducing drag. Up wind, you can put one board down with a more efficient high aspect shape. Plus if you want to go into really shallow waters, retractable boards can reduce draft even more than the minikeels commonly used on catamarans.

Fixed minikeels are primarily a cost/simplification approach.

[django37]

Nearly half the harbours used by pleasure boats on this planet are empty of water at ebb. Cruising boats should by built for this, and many are ...

[GrowleyMonster]

Not the best thing, to sink down into the mud twice a day. Mud is not as soft and cuddly as you might think. It is actually fairly abrasive, and there will be lots of shells in that mud. Your bottom paint won't last nearly as long as it would, otherwise. The hull should handle it okay. Through-hulls will of course get plugged up quite often. You can forget about barnies and other marine growth on your keels and bottom, though.