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Old 06 May 2011, 08:02   #1
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Shallow Water

What minimum depth do most of you look for to safetly use ribs when checking tides and chart?
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Old 06 May 2011, 08:22   #2
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What minimum depth do most of you look for to safetly use ribs when checking tides and chart?
Far too many variables to give a definitive answer!
In my 'usual' operating area in a calm sea I get twitchy with less than 2m under the keel, but that's over a muddy/sandy seabed which shouldn't(!) do a great deal of damage.
I treat rocky or shingle bottoms with much more respect.
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Old 06 May 2011, 08:52   #3
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What minimum depth do most of you look for to safetly use ribs when checking tides and chart?
Welcome to Rib net!

For me, it all depends on what speed I am doing, what the conditions are etc.
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Old 06 May 2011, 09:12   #4
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For me also I get twitchy around 2M mark, but if it is 2M I would be going rather slowly anyway, its also depends if your in an area you know well or not, if you know it well then you probably know where things start to get shallow and slow down and keep an eye on depth. If you don't know it well then there aint no substitue to studying a paper chart and tide tables.
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Old 06 May 2011, 09:13   #5
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Welcome to Rib net!

For me, it all depends on what speed I am doing, what the conditions are etc.
Ditto.

I won't plane unless I'm certain it's safe to. If I see the depth go to less than 10 feet, I'm back down to displacement speeds unless I know the area is clear.
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Old 06 May 2011, 10:38   #6
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thank you, i'm fairly new to ribbing as well as the forum if you couldn't tell!

i was out the other week and certainly aimed to be in at least 3m all the time, especially when planing. The worry i had was going back up the river and to the slip i wasn't sure if there was enough water, but i made it and it ended up being more than 1.5m.

Depending on the weight in the baot etc i would normally aim to have a depth of a least 1.5m even at very low speed
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Old 06 May 2011, 10:42   #7
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Have you got a depth sounder/fishfinder and a chartplotter?
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Old 06 May 2011, 10:45   #8
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yes i don't want to take any risks
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Old 06 May 2011, 12:56   #9
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I've probably done as much shallow-water ribbing over the past two years as anyone on this forum, most of it at Mont St. Michel, and in its surrounding estuaries; I don't seem to go anywhere else nowadays. I think shallow water causes people more concern than bad weather, rocks or night sailing. Being off the chart in 2ft of water, ten miles from safety makes you feel very exposed, believe me.

I would say that if you're going to get into 'skinny water' ribbing you have to accept that sooner or later you're going to run aground; it's only a matter of time. It may or may not be the end of the world but in any case it's a small price to pay for glory. Have a look at this video if you want to see what a real shallow water cock-up is all about. I have loads of others on my YouTube channel:

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Old 06 May 2011, 13:20   #10
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Quote:
Originally Posted by GeoffChopper View Post
What minimum depth do most of you look for to safetly use ribs when checking tides and chart?
Why not consider doing a course in navigation Essential Navigation and Seamanship would be a good starting point followed by a practical course .
Takes the guess work out of the equation and will give you more confidence.
Can organise you an online course if you like (blatant plug I know).
You will learn about tides and passage planning and how to use a tidal curve so making your boating more fun and your insurance company should offer you a discount.
Tim
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Old 06 May 2011, 13:43   #11
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thanks for all your comments and help, i've done a RYA Level 2 course so have a few basics, the next course i'm heaing for is the vhf.

The main reason for initial question was more to do with finding slipways and making sure the the boat would get down the river/access to open sea and wondering what other people allowed for river depth so i know what time to use the slipway based on the tide curves available.
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Old 06 May 2011, 14:04   #12
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Hi Geoff,

It will be slipway specific - and sometimes very local to the slip. I need +3.8m of water to get my boat into the water at my local slip - but the last +1.5m of depth is just to get the last 20m to the slip!! You can get in and out of the harbour itself (and the mooring) at anything above +1.7m.

You need to look at the chart for where you'll be operating, and get a feel for what's going to happen as the tide changes!!

On the other stuff, if it's calm, and I'm approaching a sandy beach - I slow down at <5m (depth) - displace at <3m - minimum speed at <2m - and watch the depth sounder carefully and knock it into neutral at <1m. This is on our local (relatively flat) sandy beaches, that I know quite well, and know that when I've got 0.6m under the keel the skeg of my outdrive leg will just be touching the sand.

On a boulder beach - I generally stay well clear - and if the chart says mud - it's not worth the cleaning!!

D...
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Old 06 May 2011, 15:42   #13
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Nothing like a fist hand view of the bottom of the slip, get yourself down there at a really low tide and have a look. Check the approaches for banks, rocks and old cars!!! Even at 2 knots you can go from 2m to nothing in less than the length of your boat if you’re off line.
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Old 06 May 2011, 16:10   #14
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I have my shallow alarm set to 1.5m i know the depth of the hull in the water so that gives me arround 2m of depth ish.
engine get tilted up as soon as I get to 1.5mtr just to make sure I dont hit the prop/skeg.

I know the boat will float in about 12-18 inches of water.
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Old 06 May 2011, 17:20   #15
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Last time I was out I was down to 1.6 feet of water on the sounder, engine tilted up, which given that I was miles from home was starting to make me pucker a bit as I wasn't sure if the sandbar was going to get any shallower before I got over it and I'd not crossed it before. As it was I was ok, though I wasn't certain if the tide was rising or falling so I did take a different route on the way home...

I agree that less than 6ft/2m in unfamiliar waters makes me really pay attention and slow right down even if the chart says it is OK.

GJ0KYZ's video is excellent

As somebody who launches off slightly dubious beaches, I also agree that a good poke around at dead low water is well worth doing so you know where the lumpy bits are (& can pick up any prop mangling debris and dispose of it)
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Old 06 May 2011, 19:18   #16
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I used to regularly run in 2 foot or less at planing speed , as has been said its all to do with local knowledge and experiance.

If its mud,sand you may get away with it , but all it takes is one rock and its expensive !

I am happy to do 30knts + if I know the area well , but if its unknown its 6knots max . Interestingly the local RNLI ILB runs on the plane as soon as possible to lift them out of the water , rather then at displacement which took more water etc - but they had other things to think about and didn't pay for new ss props !
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