Sailing The Rip into Port Philip Victoria

[40 South]

Originally Posted by El Pinguino

Totally amazing... I just can't find anything on line with slack water times for the heads.. I'm sure its out there some where... there used to be a handy little book...

Anyway... lets say nominal range outside 2 metres... inside due to narrow entrance 1 metre.
So...it has been falling outside for the last 6 hours.....water level outside is now -1 (low water) but water inside can't escape fast enough so is still higher inside than outside ( -.5)... water rushing out through gap at max rate.
Water outside now rising, level inside still falling.
3 hours later level outside is -.5...... level inside has fallen to -.5 ... slack water
Water outside keeps rising , water running in through hole, water inside now rising.
High water outside (1.), level starts falling, but as still higher than inside (0) water still going in hole.
3 hours after high water outside level now same as inside , slack water, water starts running out.

Hope that makes sense

Looks like its just gone neaps so not a strong stream.

Call 'Lonsdale' to confirm tide/slack water times.

Hope this helps.

Go to BOM site ….Tide Predictions for Australia, South Pacific and Antarctica

Rustic, it is better to go in at slack water flood, the start of the flood, just after low tide.

[Rustic Charm]

Originally Posted by Ann T. Cate

Rustic Charm,

Many places on the Australian Coast have a large amount of impounded water which "wants" to come out through a small opening. For all of them, it is 2 or three hrs. past actual low or high tide that the slack water happens. I don't know if these are correct terms, but we call it "run in" and "run out". Plan on it anywhere there is a substantial bit of water needing to move.

Ann

Yes, I understand the theory behind what happens in such bay's as far as the water flooding and escaping. What I'm surprised at is the confusing way of describing this 'slack' as being three hours after the event.

I always understood that 'slack' tide was when the water stops running, at either low or high tide. I would have thought it the ebb is still happening up to three hours after the low tide, then the 'slack' has not begun. And for that matter it seems odd that they even claim it's 'low' tide if it's still emptying? Ping explained this well.

I'm also surprised that for such a notorious spot, there really isn't much documented on this three hours past stuff.. even the official pdf about entering the rip says nothing about it. Though it does spell out that the 'slack' in the RIP corresponds with Williamstown low and high water times. Which is helpful.

[Rustic Charm]

Originally Posted by 40 South

Go to BOM site ….Tide Predictions for Australia, South Pacific and Antarctica

Rustic, it is better to go in at slack water flood, the start of the flood, just after low tide.

Thanks Craig, The BOM is what I'm using.

And yes, slack water and start of the flood, so I have the current taking me in is what most seem to be recommending.

The question now seems to be coming up is at what 'time' will that be? That's the bit I'm getting confused at. The Yachting Australia pdf

http://www.yachtingaustralia.com.au/.../the%20rip.pdf

Suggests the right time corresponds with Williamstown tides, which are as follows (according to BOM)
Wed 26 Aug Williamstown

Low4:23 am0.25 mHigh10:52 am0.79 mLow4:15 pm0.52 mHigh10:02 pm0.88 m

Where as the Lonsdale (which is at the Rip) has the following,

Low12:30 am0.42 mHigh7:43 am1.35 mLow12:52 pm0.79 mHigh7:23 pm1.34 m

[lockie]

Lots of confusion between times for high & low tides and for slack water at the Rip! Hope I can help...........

Let's start with a rising rising tide in Bass Strait. Water is pouring in through the (relatively) narrow Rip gap, and because it's narrow the level in the bay rises more slowly than the level outside.

Eventually the tide gets to its highest point, at which time the level in the bay is still trying to catch up and is still bit lower than the level outside, so water is still pouring in. Hence at high tide, we don't have slack water (in fact we have close to the maximum stream - bad time to be there). Ok so far?

After high tide outside the level outside starts to drop, but at first it's still higher than the level inside, so the water keeps pouring in. Eventually the level outside matches the level inside, and then we have slack water flood.

As the tide outside continues to drop, the water starts to pour out of the bay. But of course it can't get out quick enough, so the level inside remains a bit higher than that outside. Eventually we get low tide outside and it starts to rise again. But the bay level hasn't caught up so water is still flowing out. As the outside level rises, it eventually matches that inside. Then we have slack water ebb, and off we go again.

Hope this isn't too wordy and helps you understand.

A happy conincidence means that slack water is very close to high and low tides at Williamstown at the top of the bay, which are easy to find out (newspapers, weather websites etc). The actual slack water time can vary by quite a bit from the official predictions due to the influence of winds and barometric pressure, so the Willy tide times are generally about as good as you'll get.

I stringly suggest you get the Port of Melbourne's great little Tide Tables book which has the year's predicted tide times for all parts of Victoria, plus the Rip slack water times and time, plus velocities of the maximum tidal stream. Plus a heap of other fun stuff. You can get it from Boat Books, the government bookshop, and a few other places:

Boat Books Australia

And when you're berthing at Queenscliff, don't forget that the tide runs through the marina. It's strongest closer out to the channel. First time there I provided wonderful entertainment to the crowd of onlookers, when I cleverly allowed for the wind but not the tide which grabbed my old-fashioned full keel and then......well, no need to say more.

Cheers, Graeme

[lockie]

And another thing......

The reason why slack water flood is generally better is that if there is any residual flow, it will be flowing in, not out and banging into the prevailing SW swell and kicking up nasty unpredictable waves like the ebb does.

I'll shut up now.

[Rustic Charm]

Originally Posted by lockie

Lots of confusion between times for high & low tides and for slack water at the Rip! Hope I can help...........

Let's start with a rising rising tide in Bass Strait. Water is pouring in through the (relatively) narrow Rip gap, and because it's narrow the level in the bay rises more slowly than the level outside.

Eventually the tide gets to its highest point, at which time the level in the bay is still trying to catch up and is still bit lower than the level outside, so water is still pouring in. Hence at high tide, we don't have slack water (in fact we have close to the maximum stream - bad time to be there). Ok so far?

After high tide outside the level outside starts to drop, but at first it's still higher than the level inside, so the water keeps pouring in. Eventually the level outside matches the level inside, and then we have slack water flood.

As the tide outside continues to drop, the water starts to pour out of the bay. But of course it can't get out quick enough, so the level inside remains a bit higher than that outside. Eventually we get low tide outside and it starts to rise again. But the bay level hasn't caught up so water is still flowing out. As the outside level rises, it eventually matches that inside. Then we have slack water ebb, and off we go again.

Hope this isn't too wordy and helps you understand.

A happy conincidence means that slack water is very close to high and low tides at Williamstown at the top of the bay, which are easy to find out (newspapers, weather websites etc). The actual slack water time can vary by quite a bit from the official predictions due to the influence of winds and barometric pressure, so the Willy tide times are generally about as good as you'll get.

I stringly suggest you get the Port of Melbourne's great little Tide Tables book which has the year's predicted tide times for all parts of Victoria, plus the Rip slack water times and time, plus velocities of the maximum tidal stream. Plus a heap of other fun stuff. You can get it from Boat Books, the government bookshop, and a few other places:

Boat Books Australia

And when you're berthing at Queenscliff, don't forget that the tide runs through the marina. It's strongest closer out to the channel. First time there I provided wonderful entertainment to the crowd of onlookers, when I cleverly allowed for the wind but not the tide which grabbed my old-fashioned full keel and then......well, no need to say more.

Cheers, Graeme

Well, now you explained it like that, I'll change my statement to Ann that I understood it as I clearly didn't. So, that's really helpful. Thanks for that.

I'll go off the Williamstown tides and try to come in on the start of the flood. That seems to be the best answer. And I'll talk to Londsdale on 12 when I'm about to go too.

[lockie]

Good on yer, have a great trip, and make sure you tell us how you go.

[Rustic Charm]

Ill probably become a CF 'subject' and dissappear and the thread will go on for years about what I did wrong, how the boat wasn't sea worthy, how I should have had a cat, not a mono and been carrying a gun, and and and and

I'll drop some pictures in as we go through.

[GILow]

Originally Posted by Rustic Charm

I'll drop some pictures in as we go through.

A photo of the anchor settling to the bottom of the rip will help.


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[lockie]

Originally Posted by Rustic Charm

Ill probably become a CF 'subject' and dissappear and the thread will go on for years about what I did wrong, how the boat wasn't sea worthy, how I should have had a cat, not a mono and been carrying a gun, and and and and

I'll drop some pictures in as we go through.

I'll consider you a success if you don't appear on the news.

[MarkSF]

Originally Posted by Rustic Charm

How can slack water, occur three hours after high or low water at the rip?

A body of water, once set in motion, has momentum, even when you take away the force that set it in motion (which, in this case, was a difference in depth).

Slack water is always after high water and low water. Just not normally such a long time! 3 hours is a lot.

[dirkdig]

Here are the times


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[dirkdig]

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[dirkdig]

We go surfing there a fair bit,so for 30 years have been looking for slack water,other wise we either end up heading to Tassie or Melbourne


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[Rustic Charm]

looking at the winds now we are in for a good trip but doesn't look like our Flinders mooring will be too comfortable. Might have to see if we can time an arrival directly to the heads or take the extra time to head to San Remo.