How shallow do you consider too shallow?

BrAinZ · 10 August 2009, 21:27

Being a paranoid type of guy, I tend to steer well clear of any potentially shallow areas.

Quite fancy a trip up some of the rivers along the Solent, but figure that I'm going to have to get a little less scared about going into shallower waters.

I suppose the depth shown from the sounder is from the bottom of the boat, so technically a sounder depth of a few feet would be adequate.

So I was wondering, what sort of depth do you guys consider "too shallow" ?

codprawn · 10 August 2009, 21:33

Depends what the bottom is like - if it's sand or mud no probs - rocks are another story.

Shallow is the norm where I am - an oar or paddle is a great way of feeling your way around. My depth guage reads zero when I am still afloat - just!!!

chewy · 10 August 2009, 21:37

On some sounders you can put an offset in so the depth shown is below the skeg.
I don't mind taking the boat in so I can jump over the side and stand up. You'll build up confidence with time.

badbaws · 10 August 2009, 21:40

Check a chart first, or get local knowledge

SeaSkills · 10 August 2009, 21:40

Quote:

Originally Posted by codprawn

Depends what the bottom is like - if it's sand or mud no probs - rocks are another story.

On the other hand, sand and mud can get stirred up and sucked up with the cooling water, so a different set of problems

m chappelow · 10 August 2009, 21:50

Quote:

Originally Posted by SeaSkills

On the other hand, sand and mud can get stirred up and sucked up with the cooling water, so a different set of problems

yes,,, sand and grit makes lovelly grinding paste,,,,makes the inside of the water pump look like new, lol,

badbaws · 10 August 2009, 21:54

You say the Solent.. where do you mean as is quite a size.. I have been a long way up quite a few shallow areas in RIBs and never had a problem personally, but just check tides in Ashlett creek and don't watch the mill pond level instead of the sea water level as you may get stuck!!

Poly · 10 August 2009, 21:55

"Acceptable depth" is surely related to speed, and to whether the tide is flooding or ebbing?

BrAinZ · 10 August 2009, 22:13

Thanks for the posts so far.

So what depth on your gauge would make your concerned?

10ft, 6ft, 3ft ?

codprawn · 10 August 2009, 22:16

Depends on the charts - if it is a nice flat area then about 8ft - you need to slow down quite a bit as it gets shallower. It all boils down to local knowledge.

badbaws · 10 August 2009, 22:21

That is what they invented powertrim for..

chewy · 10 August 2009, 23:11

Quote:

Originally Posted by BrAinZ

Thanks for the posts so far.

So what depth on your gauge would make your concerned?

10ft, 6ft, 3ft ?

Depends what the draught is on the boat....

GJ0KYZ · 11 August 2009, 06:28

Shallow water is a way of life here in the Channel Islands. My depth sounder can read zero and I'll still be afloat. I use the boat hook-over-the-side technique described above all the time. Maybe one of those new-fangled forward-looking sonars is the answer. By the way, don't go to Mont St. Michel if you don't like the idea of shallow, murky water; it will give you the creeps.

Try folding paper: http://www.flickr.com/photos/gj0kyz/

BrAinZ · 11 August 2009, 06:33

We've got a Ribeye S650, which according to the website has a draft at rest of 0.55m

I'm a little confused though, as to where the GPS/Sonar would measure the depth from.

chewy · 11 August 2009, 07:15

It'll be either through hull transducer or mounted on the transom.
You need to measure how far your leg goes into the water too.

PeterM · 11 August 2009, 08:39

I spend the first & last mile & a half of any trip in about 2-3 feet . Once you get used to it you stop worrying and you jusy go very slow. But as its all mud underneath its not to bad.

Following other boats in the channel can give very false reading as the mud is stirred up - but if a ' big' boat is in front you know they will hit bottom first !

Generally for me its only to shallow when the prop has to be out of the water to keep going!

Dry_Doc · 11 August 2009, 09:16

We operate in the Humber. Shallow water is a fact of life!
Less then 1.5m sets off the alarm but you can get away with less than 1m under the keel if you proceed with extreme caution!
It's mostly mud and sand so not too much of a problem if you ground out at slow speed. The exception is the launch/recovery site which is a rock strewn mess.

ben tye · 11 August 2009, 09:44

I like to check out the bottom on a low spring tide and take some photos and notes. As previous posters mentioned, drive slowly and with caution and enjoy the less accessible areas of our coastline.With the engine leg up a little the draft on most RIBS is fairly minimal. Watch out for falling tides on a spring as you may be stuck for quite some time. Most of the channels in the Solant are marked. Also check out your Reeds Almanac which will tell you how many hours either side of high tide you can enter a channel.

walruz · 11 August 2009, 13:19

I regularly have to run in shallow water. I always consider anything more than 1 mtr as enough to full belt it. But I do know the waters I do that in well. The rest of the time, as others have said, proceed with caution and use your power trim and it shouldn't be too much of a prob. I'vwe only scraped the prop in the sand once n 2.5 years including regular beaching.

Ian

jyasaki · 11 August 2009, 15:51

The area I usually abalone dive has us launching in a tidal river, then running out to sea. Chioce of 2 launch spots: a concrete ramp in a small arm off the river, or into the river itself. Lots of skinny water. I always pull the stainless prop, and put on a (now beat to crap) aluminum wheel instead.

If I launch off the ramp, I have to get to the river itself, which is pretty much impossible at low tide, and a depth of maybe a couple of feet at high tide, over a bar of sand, pebbles, and mud. The bar itself tends to move with the flow of the tides. My transducer is just off the centerline of the hull, and has read as low as 1.2 feet or so without hitting anything (which isn't to say that I haven't hit stuff before...) With the motor trimmed way up, I sometimes have to get people out of the boat and walk/push/pull it over the bar.

The same goes for the mouth of the river (which you hit no matter where you launch), though there you can time the swell to help get over the really shallow part. High tide is generally no problem; 26' commercial fishing boats use the marina as a base (but time their arrival and departure for high tide, I think.)

The depth reading on my finder is, as far as I know, depth under the keel for the time being. I haven't set the offset yet (mostly laziness, but partly because I haven't decided which is best: display depth from the surface for diving, or depth under the skeg when trimmed in.)

Anyway, when it starts reading skinny water, trim the motor up, and go slow. And be ready to kill the motor if you hit anything unless you really dislike your current prop. And carry a spare, and the tools to swap it out.

jky