Warning a Boat off the Submerged Barrier off Southsea.

[DJE]

A Dutch 37 footer left Portsmouth at the same time as us yesterday both heading East. We made for Horse Sand Fort and he seemed to be making for a point midway between the main passage and the fort. Just about LW neaps with a bit of a swell coming in from the east so I certainly wouldn't have risked it. Fortunately he was transmitting AIS and I was playing with OpenCPN so I could call him by name and warn him off.
He got to the fort about the same time as us and we were close enough to have a chat about it. Although very close to one of the yellow posts he didn't know about the barrier. He thanked us for the call and said "Acutally we are not so deep, but I don't like concrete blocks." My good deed for the day.

 

[chubby]

Does anyone sail across the blocks at high tide? I never have and have always used the marked passages but if the blocks are just awash at LW then if the height of tide is more than your draft with an allowance for swell it should be safe to cross and would avoid the convergence at the dolphins but although logic says it could work I never tried it!

 

[prv]

I wonder how he came to be heading towards it all unawares.

Looked at the chart but didn't see it?

Just didn't bother to look at all?

Wonder what kind of chart he was using - it's pretty obvious on my Imray sheets, and I'm sure the Admiralty make it clear, but on a moderate zoom of Navionics it's merely a row of beacons and an unlabelled dotted line:

Zoom out one step further and the yellow beacons also disappear...

Pete

 

[prv]

Does anyone sail across the blocks at high tide? [...] although logic says it could work I never tried it!

You're not alone!

Tom Cunliffe makes the same point in the Solent section of the Channel Pilot - people who would happily sail over drying rocks when the tide is high enough to do so, nevertheless avoid crossing the barrier. Tongue-in-cheek, he puts it down to a fear of being "dragged to their doom by the ghosts of frustrated U-boat crews"

Pete

 

[rwoofer]

I have to admit many years ago before I knew of the barrier, I didn't spot it on the chart either and happily and fortunately sailed over it.

 

[laika]

Does anyone sail across the blocks at high tide? I never have and have always used the marked passages but if the blocks are just awash at LW then if the height of tide is more than your draft with an allowance for swell it should be safe to cross and would avoid the convergence at the dolphins but although logic says it could work I never tried it!

+1. It should be perfectly fine. But it never seems the right day to try it. Anyone know why they don't publish the barrier's maximum height (/depth)? Are we still worried about the dastardly hun taking control of the pound shops on Gosport high street?

 

[ffiill]

Not knowing the area if I had been using the above chart and with a draft of little over one metre I would probably have cut the corner rather than mess with big ships in the main chanel and potentially hit the barrier.
Dangerous map but then I am old fashioned and use Admiralty Paper and RNC charts and they have everthing on them visible to that wonderful auto zoom in mechanism-the human brain.
I just took a look at my Admiralty RNC and neither I note does the above show the boat passage half way up the barrier or the one close inshore.Also the Admiralty chart gives minimum LW coverage mid way along the dog leg approaching the Fort at 0.3 metres.
Funny how we are though-yesterday I was heading out of Plockton at low tide and was panicking because there was only 40 foot under the keel not the usually 400 plus foot!

 

[prv]

Dangerous map but then I am old fashioned and use Admiralty Paper and RNC charts and they have everthing on them visible to that wonderful auto zoom in mechanism-the human brain.

Exactly - that was my point in posting the screenshot. It's a subject I brought up in a thread over in the Mobo forum about plotters vs charts - charts are assembled by a human cartographer who decides what it's important to show at each scale and area of coverage. The picture on a plotter is assembled afresh by the machine each time you pan or zoom, from its database of charted objects, and it does that using some fairly simple rules. The vast majority of the time it works well enough, but there are times when you need to know about small things even at a wide zoom to get a proper understanding of the situation.

Pete

 

[robp]

Would have thought that eye-balling the dolphin, with its marks would raise some questions. Plus, the inshore passage is fairly noticeable.
Must admit that I was never tempted to test the calcs. Years ago I was invited to race in several corporate race weekends on Sunsail SO36's. Was told that someone who did the calcs a week before took the keel off one on the barrier.
Its a bit like cutting the corner between the starboard mark off East Head and Chichester Bar Beacon. I've seen it done by an experienced skipper at high water but never fancied testing it myself!

 

[Twister_Ken]

I'm still nervous when sailing inshore of No Man's Land despite official reassurances.

 

[oldharry]

.
Its a bit like cutting the corner between the starboard mark off East Head and Chichester Bar Beacon. I've seen it done by an experienced skipper at high water but never fancied testing it myself!

Do it every time coming in/out of Chi with just under a metre draft +/- 3hrs Hw. usually 14 - 15 feet of water, but getting it wrong proves the shallow alarm is working! Not marked presumably because the fairly narrow deep water channel moves quite a bit in stormy weather. and it can shoal rapidly either side. But I never fancied my chances with the barrier: mainly because I have not been there at LW to see for myself just what IS there, while I always check the East channel in Chi early in the season near LW

 

[Daedelus]

Don't recall ever seeing the blocks at LW perhaps they're awash at Chart Datum?

The dolphin gap wasn't always there. Recall the story of the Admiral who was desperate to win a particular sailing race and to the mingled horror, admiration and amazement of the rest of the fleet took a short cut through the then continuous barrier. After the race, which he won, everyone told him he was mad and then he told them that as port Admiral he had arranged for blocks to be removed to make the dolphin gap - which had been intended for some time, but he hadn't seen fit to tell anyone else until after the race.

 

[sailorgirl]

Do it every time coming in/out of Chi with just under a metre draft +/- 3hrs Hw. usually 14 - 15 feet of water, but getting it wrong proves the shallow alarm is working! Not marked presumably because the fairly narrow deep water channel moves quite a bit in stormy weather. and it can shoal rapidly either side. But I never fancied my chances with the barrier: mainly because I have not been there at LW to see for myself just what IS there, while I always check the East channel in Chi early in the season near LW

At LW you can walk out to the blocks inshore and probably paddle across the inshore passage though I've never tried it cos the water is too cold. We used to use the inshore passage regularly but only around HW (2.1m draft) going to & from Southsea.

Have seen small mobo's going across the barrier and once a catamaran but never a monohullled yacht

 

[Evadne]

In my yoof I used to go across it regularly at HW+/- 3 hours, i.e. half tide but always south of the dolphin. Evadne draws 4' 2". Then one day I was passing through the dolphin passage (oo-er!) near low water and saw concrete blocks awash to the north. Ever since then I've used the marked passage. The blocks looked fairly uniform but I wouldn't bet on some not being a bit jumbled. Easily +/- a foot, maybe two in places. The min depth ought to refer to the highest point but IMHO if I feel the need to do the calculations, then that is too close for comfort. Even if it's right it only refers to flat water with 1000mbar pressure.

 

[l'escargot]

I'm still nervous when sailing inshore of No Man's Land despite official reassurances.

Glad it's not just me

 

[prv]

Don't recall ever seeing the blocks at LW perhaps they're awash at Chart Datum?

I've seen photos of them standing several feet out of the water, but perhaps that was while the Brambles cricket match was going on

Pete

 

[l'escargot]

How lucky do you feel?

 

[[2068]]

I've never had the courage to try it, but from observation of the blocks at low tide, a boat drawing a metre or so should have adequate clearance to go straight across on a good high tide, assuming flattish water.

At low tide and in daylight, it shouldn't be an issue if the skipper is awake, as you can see the blocks sticking out of the water.

When the blocks are 1 foot beneath the surface, you might not be able to see them, and there would be a crunch.

 

[stephen_h]

How lucky do you feel?

Looks about 50/50 to me

 

[sailorman]

A Dutch 37 footer left Portsmouth at the same time as us yesterday both heading East. We made for Horse Sand Fort and he seemed to be making for a point midway between the main passage and the fort. Just about LW neaps with a bit of a swell coming in from the east so I certainly wouldn't have risked it. Fortunately he was transmitting AIS and I was playing with OpenCPN so I could call him by name and warn him off.
He got to the fort about the same time as us and we were close enough to have a chat about it. Although very close to one of the yellow posts he didn't know about the barrier. He thanked us for the call and said "Acutally we are not so deep, but I don't like concrete blocks." My good deed for the day.

I go through i flat condsitions