Poignard
Well-Known Member
Would that work when there is a 2.0-2.5 knot current pressing the yacht against the pontoon?
Cross tide (river) pontoon berth
- Thread starter Ammonite
- Start date
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Deleted member 36384
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What has the OP got to lose by trying it, the boat will either turn or not. If the OP steers off at the same time, it will drive the stern into the pontoon and may increase the force to pivot out and round.
James_Calvert
Well-Known Member
Isn't this the "spronging" of which the original post was seeking an opinion about?
I've only seen someone try to do something like this once, alongside the main walkway in Falmouth Haven. He couldn't get the bow out far enough to safely depart forwards and eventually sprung off conventionally, motoring out in astern.
The video makes it look very easy, but there doesn't seem to any wind or tide pinning the boat into the berth.
I've only seen someone try to do something like this once, alongside the main walkway in Falmouth Haven. He couldn't get the bow out far enough to safely depart forwards and eventually sprung off conventionally, motoring out in astern.
The video makes it look very easy, but there doesn't seem to any wind or tide pinning the boat into the berth.
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Ammonite
Well-Known Member
It only took 23 posts to get there. Clearly I need to work on my descriptions!
I'm hoping that the thruster along with starting with the sprong on the outside quarter before transferring the load to the outer miship cleat to complete the turn will make it more effective but until I get out there and try l dont know how much shove it will give me.
I have a feeling I shall remain pinned to the pontoon in anything above a knot
Halo
Well-Known Member
Leaving a boat against a pontoon with a regular 2kn tide pressing her on seems desperate to me. Won’t the flotsam and jetsam and weed get snagged round the rudder?
Will the fenders cope with a Gale and a surge tide pressing her on ?
Will the fenders cope with a Gale and a surge tide pressing her on ?
Daydream believer
Well-Known Member
Nobody has mentioned prop wash. My boats stern reacts quite well to a few very short bursts on the prop. So depending on what way it is pointing it will have a greater/lesser effect on my ability to get the stern off a pontoon.. By having a rope to the bow, a few bursts on the prop & the stern would come off quite easily.
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Nimrod18
Well-Known Member
“Spronging” is a new one on me - might give it a go next time I feel like experimenting.
Confess that I thought the OP had repeatedly (and carelessly) spelt “Springing” incorrectly. Apologies for doubting you OP!
Nil to add to previous advice.
Confess that I thought the OP had repeatedly (and carelessly) spelt “Springing” incorrectly. Apologies for doubting you OP!
Nil to add to previous advice.
matt1
Well-Known Member
If the tide isn’t at its strongest, or there is negligible wind (or in your favour) you may be able to combine bursts of prop wash against the rudder, synchronised with bursts of bowthruster to make her go sideways. Works for me getting my high freeboard against the wind
Daydream believer
Well-Known Member
It is the latest lockdown game
You make up a new name & slip it into a post as if it was quite normal & it sends everyone rushing to be the first to type it into google. Then , not being able to find it they start using it, as if they knew what it meant all along.
Hacker
Well-Known Member
It isn’t a new term. I saw a video on it at least 2 years ago.
D
Deleted member 36384
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It is the latest lockdown game
You make up a new name & slip it into a post as if it was quite normal & it sends everyone rushing to be the first to type it into google. Then , not being able to find it they start using it, as if they knew what it meant all along.
It's the first I have ever heard of the term but it is used in the video as well, in their captions, so it appears to have some nautical provenance.
Ammonite
Well-Known Member
The layout of the pontoons is such that its fairly well protected from debris and the worse of the weather whereas a lot of other boats will be beam on to wind and waves (small) in a SW gale. A surge tide or gale from the South or West will be blowing the boat off. The pontoon is also fendered so while clearly not ideal Im not concerned over the boats safety
Never Grumble
Well-Known Member
what page in the book?
PhillM
Well-Known Member
May I ask where this mooring is, that might help get more advice from those local.
D
Deleted member 36384
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Page 58., Technique 9, Tide on the beam, boat being blown on.
Do you have the book? It’s not that difficult to find considering pages 56 and 57 are dedicated to departing with combinations s of wind and tide pushing the boat on.
It is worth noting the graphic on page 58 with the photograph of the method on page 59, regarding g the stern line length and distance from the quarter. Then compare with the video in my earlier post. Also two different hull shapes, both doing this maneuver.
My Rival 41C struggles to spring off in astern if there is any wind on the bows due to the high aspect of bows.
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Never Grumble
Well-Known Member
Thanks, I have the book, just goes to show that I haven't read it all. Perhaps some reading in the coming month ready for when I can get out again.
dunedin
Well-Known Member
Might be interesting to try to work out the maths on the forces involved on the GRP at the rear quarter, being forced against the pontoon if trying to “spring” out against the tide. And to be successful the corner has to move along the pontoon being subjected to these forces.
Saw on a 10m boat with the water centre of effort mid way along there would be a nice 5m lever on the tide effect as soon as the side is a cm off the pontoon. And side forces of water massively stronger than windage, anything below a hurricane.
My brain can’t fully work the maths, but the stern sprong and engine is also pulling the stern corner inwards, whilst the corner scrapes along the pontoon if successful, popping any fenders out.
Best tried in a school boat, not your own.
Saw on a 10m boat with the water centre of effort mid way along there would be a nice 5m lever on the tide effect as soon as the side is a cm off the pontoon. And side forces of water massively stronger than windage, anything below a hurricane.
My brain can’t fully work the maths, but the stern sprong and engine is also pulling the stern corner inwards, whilst the corner scrapes along the pontoon if successful, popping any fenders out.
Best tried in a school boat, not your own.
thinwater
Well-Known Member
Think about how much force it takes to create 3 knots of side movement.
Get a different slip. I've seen some bad acidents that just weren't worth going out. 1-2 knots, sure. 3 knots, go home.
Ammonite
Well-Known Member
The good news having looked into it in more detail today is that I have over estimated the ebb which will actually be more like 1.5 - 2.0 knots max at springs so provided Im not being blown on I should be able to sprong off apart from a couple of hours when its above 1.0 knot
doug748
Well-Known Member
Spronging works for me, springing off never did unless conditions were perfect.
The advice is to steer into the dock but I found if you want really big angles you have to do a bit of judicious steering into the turn.
Great thing about spronging is that all the action is a the rear of the boat so the singlehander can helm and take charge of the line conveniently. It also keeps the rope short. I always use a floating ski line so it can be cast off and ignored, if busy.
I'm not keen on the idea of trying to transfer the pivot to a centre cleat halfway through though; I think there is scope for a YouTube video in that one.
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