savageseadog
Well-Known Member
There's no chance of it silting
Holyhead Marina
- Thread starter savageseadog
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There's no chance of it silting
Triassic
Well-Known Member
Did I read somewhere that the initial cause of the destruction was a larger vessel breaking her mooring and drifting down onto the pontoons? Once one became dislodged it was a domino effect for the rest? It might explain why the marina has survived previous similar weather yet succumbed on this occasion? Have the larger commercial vessels on the outer pontoons always been there or are they perhaps a recent addition? I'm mindful I got a bit of a pasting earlier on when asking if this marina was considered safe so don't necessarily want to go there again however I wonder if a slow evolution around it's use to accommodate larger vessels might be part of an explanation.
TSB240
Well-Known Member
There is much similar comment on local social media.
I would suggest that the conditions on that night were the worst experienced in 18 years of operation. The size of the moored boats and the mechanism of the catastrophic Marina structure failure will I am sure be part of any post disaster review and investigation.
I would suggest that the conditions on that night were the worst experienced in 18 years of operation. The size of the moored boats and the mechanism of the catastrophic Marina structure failure will I am sure be part of any post disaster review and investigation.
AngusMcDoon
Well-Known Member
There have always been some hefty boats on the outers.
Plomong
Well-Known Member
I didn't say "a pile of stones 4m deep"; I quite specifically said "in 3-4 m of water", understanding that to be below chart datum.
"to sugest a few piles of rock would have avoided the problems is naive in the extreme".
That is just my point: a 250 m long pile of rocks just above water at high tide would have made a considerable difference.
To my way of thinking, the marina was flimsy. That it had no protection from a direction from which strong winds can be expected over a decent if not excessively long fetch, and the use of pontoons on styrofoam floats with concrete outer layer (spraycrete it is called over here), items more suited to canal and river locations, support my view. (The aluminium co. jetty is of little protection as it is built on piles).
To say that I am naive, don't understand the location, to call me an armchair marina designer, say that my comments are misinformed, etc shows that you don't know me. Naturally.
That a decent blow from an easterly direction caused carnage, with what, 60+?? boats destroyed or seriously damaged, and the marina in tatters shows exactly who was naive -- the real-life marina designers.
I know well the difficulties that anyone trying to build a marina may encounter, the resistance from all sorts of unexpected directions, the funding problem, etc., but anything built should be built to a standard that will survive in the chosen location. If that cannot be done within the available funding limits, then chose a different location.
I stand by what I said: The design was not adequate -- mother nature proved that. A modified design could have been built with the addition of a breakwater in relatively shallow water.
Over in this neck of the woods it is usual to encounter 7, 10 and more meters of water (below CD to be clear) in most locations that are suitable for a marina. In my former mooring location, the riser chain was over 12 m, with an 80 cm diameter mooring buoy fore and aft as part of a trot for 5 boats, the inner end of which was anchored to a concrete caisson by a 2" diameter lead-weighted rope. Some thought it was overkill. A storm with green water coming over the breakwater showed that was not so. The breakwater was breeched that night in several places.
Plomong
penberth3
Well-Known Member
Maybe not there, but the point is you can't just dump rockfill at random, as Plomong was suggesting.
Heckler
Well-Known Member
Jonathan Fox pictures of the pontoon joining mechanism bolts on his FB page are quite graphic. https://www.facebook.com/JonathanFox1972?fref=gc&dti=1597283927017309
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DJE
Well-Known Member
Correct. The MMO would require all sorts of detailed analysis before they issued a licence. Also a 10m high rubble mound breakwater would be 50m to 70m wide at the base. At 250m long it would require close to 200,000 tonnes of rock. A bit more than a couple of barge loads.
JumbleDuck
Well-Known Member
The breakwater at Port Bannatyne marina is roughly as wide at the base as it is high. Certainly not 5 - 7 times the size.
DJE
Well-Known Member
That means side slopes of 2:1 which is impossibly steep for a rubble mound. Admittedlty my figures were based on sand fill with rock armour and side slopes of 1:2 or 1:3 and a 5m to 10m wide crest. If it was all rock and you had a good foundation you might get the slopes up to 1:1.5. With a 5m crest this would give a base width of 35m.
JumbleDuck
Well-Known Member
How big is "rubble"? The PB one is made of fairly big rocks. Here's a picture
From base to top it's about 7m (I can measure next time I'm there), the pathway along the top is about 2m wide and the slope of the side you can see carries on to the bottom.
D
Deleted member 36384
Guest
Why should Holyhead be a special case for funding a breakwater? There are at least 4 exposed marinas that have all suffered damage due to the wrong wind direction that I am aware of. There are also the same number of private marinas that have built robust sea walls to protect their marinas from all wind directions. The fact is that floating breakwaters are a poor solution to exposed marinas, it gets proven time and time again.
DJE
Well-Known Member
JD I think we're talking about different things. A rubble mound is random shaped rock tipped into place with slopes equal to or flatter than the natural angle of repose of the material. (For big breakwaters the individual rocks in the outer layers will weigh several tonnes.) The one in your picture looks like masonry which is much more difficult to construct - especially the bits below low water level.
JumbleDuck
Well-Known Member
I don't think it's masonry, but it certainly looks as if it is more sophisticated than rubble piled in the water. Now you've got me interested - I shall have a good look at it next time I'm there.
JumbleDuck
Well-Known Member
As Rhu Marina demonstrated over its first winter, and regularly ever since.
Resolution
Well-Known Member
There is a new marina near us in Turkey that has an interesting outer breakwater wall, comprising a line of steel pipes/piles sunk into the seabed. Depth is about 12 to 20 metres (but no tide), so these are pretty long tubes. I think they are about one metre diameter each (but it is all underwater now) and the gap between them is smaller. The breakwater has to cope with frequent 30 knot winds and perhaps one metre waves. In these conditions the concrete pontoons move by a couple of centimetres each time a wave hits.
Some pics of the construction on this website http://www.turnkeybodrum.com/gulluk-marina
Of course tides make marina construction so different.
Some pics of the construction on this website http://www.turnkeybodrum.com/gulluk-marina
Of course tides make marina construction so different.
vyv_cox
Well-Known Member
I am unable to find them. Can you give any more direction please?
lw395
Well-Known Member
Haslar Marina in Gosport has a 'wave break' structure around its exposed side. This is piles into the seabed with wooden planks between.
The engineering is not impossible, but it probably helps to have a few hundred yachts paying Solent prices to fund it.
There is probably a limit to what people will pay to keep their boats in the water through winter storms?
How many of the these boats have seen significant use over the Winter? I'd guess most were just there because its a cheaper/easier option than laying up ashore?
At the end of the day though, there will always be boats trashed by storms.
The engineering is not impossible, but it probably helps to have a few hundred yachts paying Solent prices to fund it.
There is probably a limit to what people will pay to keep their boats in the water through winter storms?
How many of the these boats have seen significant use over the Winter? I'd guess most were just there because its a cheaper/easier option than laying up ashore?
At the end of the day though, there will always be boats trashed by storms.
ShinyShoe
Well-Known Member
Quite a few of those boats are working boats. They don't stop working for winter.
A number of the yachts were taking part in a winter series. The risk of higher winter marina fees is more lift out for winter, numbers in the series drop and the series folds meaning even more lift out for winter and so the cost for the few who want to cruise in winter becomes astronomical.
Boats - Yes. Marinas - should not be destroyed by relatively unremarkable conditions (we've had stronger winds just from a different direction).
80 boats in one Marina on one day - that shouldn't happen.
lw395
Well-Known Member
But when you look at the numbers, you've got a few working boats, then a handful doing a bit of winter series, the rest wintering.
The economics of it are far removed from a Solent marina.
Camper's has a pontoon wavebreak which can be pretty lively in a good Northerly, but they don't go mooring fishing boats to it.
Some of the outer pontoons in Cowes used to be untenable in a NE gale. But they protected the inner pontoons.