Fin aground on a sandbank.... actions?

[Yellow Ballad]

Yes Welsh Grounds. I could always exit further east but that'll mean more time over them. Destination Portishead, I would need to be at the Denny Shoal South cardinal to cross the Kings road shipping channel if I were to go over them. I've just been informed dredgers drawing (sp?) 4m regularly do their business over there but then have the benefit of not falling over if they get it wrong.

Seajet I do like the Seafarer but it has a habit of needing tweeking just when I need it going into harbour etc. I'm hoping the Duet will give me a better constant reading and I can use the whizzy machine when anchoring etc.

 

[Seajet]

Ah, I'm afraid I've never heard anything good about Duet's, though it's the log part which packs up - the saying about NASA kit that their stuff with no moving parts is OK is true in my experience, I have a Clipper depth in the cockpit and it has worked perfectly for years, just doesn't show seabed consistency.

I do think fishfinders are the way to go, much more info inc seabed shape and layers, even a 9 waypoint gps for the same money; they usually come with transom mount transducers but these work fine if stuck inside the hull with sealant.

One snag with the Garmin fishfinder is it comes with a horrendously obtrusive bracket just begging to get knocked off, so I am making a stainless panel to flush mount the display without the bracket.

 

[zoidberg]

It is clear from peering at the charted depths on my MemMap copy of BA1176 and yours ( on screen above ) that the charted drying heights change substantially across the line of your intended track, with time between published surveys. I can't tell from that whether they're increasing or otherwise.....

One thing is clear, whichever chart you end up using. It will be out of date regarding spot drying heights over the Welsh grounds.
Best re-read 'Riddle of the Sands'...... [http://www.ybw.com/forums/images/smilies/rolleyes.png]

 

[Seajet]

Strikes me ignorance is indeed bliss sometimes - if Yellow Ballad hadn't been so conscientious as to ask here, just blithely trundle along I'm sure he has the skills to make it- now he may have ulcers and insomnia.

After all, I did meet a chap ( with young family, on an old mobo ) who thought he was tied up to Guernsey until someone told him ' actually mate, this is Jersey ' - and he'd been across all manner of rocks and tides to manage that.

 

[TSB240]

We spend a crazy amount of time sailing over green bits of charts in our area. As many have said your chart is really unlikely to represent the actual state of the banks you may wish to cross. In our area we have charted depths of 3 metres that are now drying by up to 1/3 metre!

I can suggest a very simple solution should you really have any doubt about the clearance that you may have.

IF possible
get a good view of the banks you intend to cross as the tide is coming in. This may be the day before it could be on the same day. Check at what stage the incoming tide actually starts to cover the highest point of your proposed track across the bank. Compare this with the time of high water and compute back to the earliest crossing you might make with your given draught. In our area we can have the tide coming in at an inch a minute on springs at half tide so it does not take very long to cover your proposed track.

It is unlikely that either barometric pressure or river conditions are going to be so dramatically different in a short timescale.

I am fortunate to have a very shallow draft boat and can usually look out over any of our local banks at say 3 to 2 hours before HW and say if it is covered by water then I can take a short cut. We also have similar crazy tidal ranges in this area.

I was caught out many years ago on an ebb tide. Having a heavy crew member hauled up and stood on the cross trees leaning on the mast ensured our draft was sufficiently reduced to allow us to sail back into deepwater.

Of course in as much this works for getting under a bridge it would also work for you!

 

[UK-WOOZY]

id advise not being towed off if stuck in mud, got my previous 22ft fin stuck in blyth sands. got towed off and it ripped the rudder in half. other than that, i was fine. hindsight, we should have waitied for the returning tide a few hours later.

 

[Seajet]

UK-WOOZY,

that's a good point I for one hadn't thought of; though I always have knives handy so may have used one as last resort if I felt so much horrible load on the boat.

TSB240,

I agree to the extent there's a handy wall to go alongside near my mooring, but I NEVER go alongside, let alone dry out there, unless I've been there at the previous LW to check for generously discarded shopping trolleys, scaffold poles etc.

But in Yellow Ballads' case I can't see how he could survey his route at LW beforehand unless he anchored off or hove to like some Bristol Pilot Cutter and sent in a photo recce' drone, ideally with some sort of rad/alt and ideally depth sensor !

In fact that's an idea; I'm sure at some stage in the future, maybe within our lifetimes, such kit will be available to yots; I can imagine this being particularly useful in the Caribbean to spot coral reef heads - seriously.

 

[prv]

But in Yellow Ballads' case I can't see how he could survey his route at LW beforehand unless he anchored off or hove to like some Bristol Pilot Cutter and sent in a photo recce' drone, ideally with some sort of rad/alt and ideally depth sensor !

In fact that's an idea; I'm sure at some stage in the future, maybe within our lifetimes, such kit will be available to yots

No radar altimeter as standard as far as I'm aware, nor depth sounder usable from the air, but a visual recce by drone is entirely possible with current kit. In fact, the latest software update I installed on my Raymarine plotter included the ability to act as a control station for the commonly used DJI Mavic: http://www.raymarine.com/multifunction-displays/lighthouse3/v3-6/

Even before this came out, I've been tempted by the idea of a drone to recce narrow Cornish inlets or give a bird's-eye view of Channel Islands rocky passages - unlikely to spend the money and faff for the one time in a hundred it might really be needed, but it's a perfectly reasonable idea.

Pete

 

[Yellow Ballad]

I'm pretty sure they surveyed a island/rock in the program below by drone, I can't remember if it was just stills ran through a computer program or something more technical with altimeters but I'm sure they had a 3d computer "survey". I can't get on all4 at the moment but it rings a bell.

http://www.ybw.com/forums/showthread.php?504935-series-2-episode-4-the-severn-Britian-at-low-tide

Edit

I can't get off the mooring as it dries at about +6m (hence sailing over green bits every time I sail). I could try and hang about but I would be taken down channel with the tide and then pushed over the top as it floods, I'm not sure anchoring in the same spot for 6 hours in BC chop is my idea of fun. It would be easier to go out in a rib, dinghy or the like but to be honest I don't think it's really worth it in this situation. The highest bank seems to be charted at 7.3m and with a tide of 10-11m you would have to be very unlucky to hit a 9m one. The channel does get surveyed a lot but I agree it's only good on the day, I'm slightly more concerned about wind and tide then I am about depth. The general advice from the old salts at the club is you can go over on the flood but on the way back you go down to Cardiff on the ebb and back up to Newport on the next flood.

I'm sure you can see the banks on the entrance to the Usk and the Welsh grounds from the RSPB site next to the club. I may get chance to have a nosey one day but I'm only normally down to go sailing or work on the boat. Looking from land a couple of miles away though doesn't really help when you're on moving on the Bristol Channel escalator.

All interesting stuff.

 

[Seajet]

Yellow Ballad and PRV,

this is all going very hypothetical and over-doing it, partly for fun.

Military drones are deployed from USN warships all the time for various tasks, and maybe by the RN depending what Maplins had.

There is often talk of spotting submarines from above with certain types of radar - not just at shallow depths - but as mega-billions still get spent on subs maybe just at shallow depths for now.

It wouldn't take much to put a 3d mapping radar on a slightly serious drone right now for all sailing clubs in a place like the Bristol Channel to use, maybe in conjuction with the hydrographers lot at Taunton to give a very recent if not real time view of shifting channels available to boats there...sounds far fetched, but look how quickly photo drones have become available to Joe Bloggs...

I think Plotters with years old info' will soon become passe'.

 

[zoidberg]

Perhaps the good 'Sundancer' should kidnap that kind 'Antares Charts' bloke for the weekend, and have him do a bit of a survey for interested BC-ers.
http://www.antarescharts.co.uk/

 

[prv]

It wouldn't take much to put a 3d mapping radar on a slightly serious drone

Oh, absolutely - look up airborne lidar bathymetry, there’s at least one company already doing it. Lidar rather than radar - same principle but using a laser instead of microwaves.

The drone to carry it is about two metres across, though, and I imagine the survey kit costs many tens of thousands, so it’s not exactly yottie kit like Raymarine clearly consider the DJI Mavic to be.

Pete

 

[alant]

UK-WOOZY,

that's a good point I for one hadn't thought of; though I always have knives handy so may have used one as last resort if I felt so much horrible load on the boat.

TSB240,

I agree to the extent there's a handy wall to go alongside near my mooring, but I NEVER go alongside, let alone dry out there, unless I've been there at the previous LW to check for generously discarded shopping trolleys, scaffold poles etc.

But in Yellow Ballads' case I can't see how he could survey his route at LW beforehand unless he anchored off or hove to like some Bristol Pilot Cutter and sent in a photo recce' drone, ideally with some sort of rad/alt and ideally depth sensor !

In fact that's an idea; I'm sure at some stage in the future, maybe within our lifetimes, such kit will be available to yots; I can imagine this being particularly useful in the Caribbean to spot coral reef heads - seriously.

Can't believe anyone would consider slitting their wrists, just because their A22 was aground on a sandbank.

 

[Seajet]

Can't believe anyone would consider slitting their wrists, just because their A22 was aground on a sandbank.

Nor can I, but it may be an option if some people were to end up alongside - their wrists that is

 

[zoidberg]

I'm hoping Tom/'Sundancer' will brief us here on his escapades.... and escapes!

 

[Yellow Ballad]

Hi Wil, all went well but the forecast changed slightly and as I have a few days off work to go sailing I decided to use the NE to take me to Cardiff this morning (4am) and the tide and the 5kn northerly to take me up to Portishead this afternoon as the wind was lighter. Managed to sail 2/3rds of the way up but I had a ship coming up the channel to Portishead so I motored the rest of the way to keep out of his way and get in before the tide turned. I recon I would have had to motor across if I came from Newport this after and to be honest I hate motoring.

I was talking to a couple of the club guys last night who quite happily sail over the Welsh grounds and I checked the older charts at the club going back a couple of years showing the depths very similar to the latest one.

 

[Seajet]

You did well listening to Wil, and your approach to nav puts a lot of people to shame - I'd like to think I'd have done the same. Virtual pint here, you'd be welcolme on my boat any day.:encouragement:

 

[bitbaltic]

Yes Welsh Grounds. I could always exit further east but that'll mean more time over them. Destination Portishead, I would need to be at the Denny Shoal South cardinal to cross the Kings road shipping channel if I were to go over them. I've just been informed dredgers drawing (sp?) 4m regularly do their business over there but then have the benefit of not falling over if they get it wrong.

Seajet I do like the Seafarer but it has a habit of needing tweeking just when I need it going into harbour etc. I'm hoping the Duet will give me a better constant reading and I can use the whizzy machine when anchoring etc.

I’d put off from commenting on this thread because it seemed a bit strange that you didn’t say what you would be sailing over until several pages in- would have got quick replies and local knowledge on the BC forum by starting a thread ‘Saiing over Welsh Grounds?’

Above half tide there is plenty of water in there to sail over them so your club pals are right. There is a charting issue somewhere near ?welsh Hook where an offlying bank is separated by a Channel with uncertain depths; but i’ve Been through there loads of times without issue.

Welsh Grounds does kick up a bad sea state close to the edge in bad weather even when there is plenty of water. Going up Channel I used to stay clear if the edge of it if possible.

Welsh Grounds does not really change depth dramatically. Cardiff Grounds, though, does. I’ve been in there and sounded 3m less depth than charted.

I’d happily sail over Welsh Grounds to Portishead but not over Cardiff Grounds on the way back.

 

[zoidberg]

I'm well pleased your day went well, Tom. You did the work needed.

PPPPPPP, as always.

 

[Yellow Ballad]

I’d put off from commenting on this thread because it seemed a bit strange that you didn’t say what you would be sailing over until several pages in- would have got quick replies and local knowledge on the BC forum by starting a thread ‘Saiing over Welsh Grounds?’

Above half tide there is plenty of water in there to sail over them so your club pals are right. There is a charting issue somewhere near ?welsh Hook where an offlying bank is separated by a Channel with uncertain depths; but i’ve Been through there loads of times without issue.

Welsh Grounds does kick up a bad sea state close to the edge in bad weather even when there is plenty of water. Going up Channel I used to stay clear if the edge of it if possible.

Welsh Grounds does not really change depth dramatically. Cardiff Grounds, though, does. I’ve been in there and sounded 3m less depth than charted.

I’d happily sail over Welsh Grounds to Portishead but not over Cardiff Grounds on the way back.

Bitbaltic, good to hear you're in agreement. I didn't really post where I was heading as I know its a ok thing to do in the right conditions and I didn't want to turn the thread into a "you're sailing over green bits!" doom and gloom thread. More a what happens when the "fhit hits the san" thread so I and others can learn from it. I've not touched bottom yet but I'm in no doubt I will and if it all goes wrong I want to know the best course of action. There's been a couple of posts on fb from penarth rnli about yachts going aground in the Wrach channel, two on one tide! Sailing a fin I want to be clued up and as Zoidberg says PPPPPPP.

Seajet, thank you for the compliment, I've drank that virtual beer many times over since tieing up... but it's no more then anyone else who owns/sails a boat should be thinking about. If you ever want a Bristol Channel mud bash give me a shout, it's not all that bad... apart from a survey boat and a ship I didn't encounter another vessel to worry about!