Taking the ground

[jonathankent]

Now I know that the boat rises and falls with the tide and sits on the bottom quite happily. But, what about if you are on the boat at the time. Does this extra weight/movement make any difference to the boat digging in and refloating again. I know when I walk on the mud I sink in and isn't always too easy to remove myself, but what about the boat. Has anyone had any issues refloating, or am I just being too cautious?

 

[Tisme]

You're being too cautious. The bouyancy from a boat is enormous.
Try holding a fender under water; it's not easy and your boat will be more bouyant than that.

 

[tillergirl]

I shouldn't worry. TG sits in mud in her winter berth and I am regularly on board. There is a slight 'popping of a cork' effect when she frees herself of the suction but she rarely is more than an inch down on her marks before she pops. The same used to happen when she was on her drying mooring off Heybridge Basin - not that I was aboard so frequently. Mind you, where a ship opposite had sat in the mud at low water for a couple of years, they advised against drying out there where presumably the mud was 'disturbed'.

 

[wooslehunter]

Wheather you make any difference really depends on how much you weigh in comparison with the boat and only when it's sinking or rising. Once it's on the mud it's likely to make little difference since the bottom area of just about any boat will support lots of weight on mud. You can bolt a couple of small boards to a pair of wellies and walk on mud quite happily - that's how the coastie mud rescue teams work.

What may be important is the shape of the keels if you have more than 1. A single keel is vertical and will slip into and out of the mud with no problem. Twin keels are sometimes a problem if they are not vertical as on my boat. They are splayed out. This creats quite a loading in wards when the boat settles and the pushes them out when it rises. This has been known to damage the hull after a few years and so Centaurs are often beefed up around the keel joints as is mine.

 

[SvenglishTommy]

Your weight will be practically irrelevant. It would take a lot of force to counter the bouyancy of the boat. It can be a bit unnerving when the keels pop out though.

 

[jonathankent]

I have a triple keel. There is a small ballasted centre keel, approx 3' long and 4" wide. Then there are 2 angled bilge plates.

I have had the inside of the hull beefed up this winter as the fibre glass on top of 2 cross members had cracked. The hull was OK, just the fibre glass on top. Anyway, these are now twice the size they used to be.

I was just 'concerned' about the relatively small surface area compared to the weight of the boat, and then if you are onboard moving around whether this would force the relatively narrow keels further down into the mud.

 

[Wansworth]

Simple test:If you can get thru the companion way on your yacht your not fat enough to affect the situation,a handy hint!

 

[VicS]

I have a 19 footer (with vertical twin keels). Your question is a valid one but it is not something to cause any concern. Just moving about on board has little effect but I have found that when sleeping on board alone with my weight directly above one keel it does tend to sink in deeper. I have been known to swap to the bunk the other side part way through the night just to even things up but for no reason other than the comfort and conveniece of getting it level again. In your case the effect may be more pronounced as the little bilge plates will sink easily but on the other hand if the centre keel sinks in fully it will probably hold the boat more steady. If you are happy with the strengthening work themn there really should be no problems. You will just have to see what happens.

The problems with well splayed keels like the Centaur have been mentioned. For them just sinking into the mud and rising back out again is enough to do serious damage (like pulling the keels off) unless they have been strengthened. FWIW we have recorded an extra 1 ton of pull necessary to pull a Berwick (which has similar keels to the Centaur but seems to be more strongly constructed) out of the mud. Sometimes the crane driver, who knows about such problems, just leaves it until the rising tide does it more gently.