Shearer. Boo. Come in here

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crabmeat thompson
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Re: Shearer. Boo. Come in here

Post by crabmeat thompson » Tue Jun 20, 2017 3:59 pm

Nick Carroll wrote:
Tue Jun 20, 2017 3:18 pm
carvin that's just refraction mate. It's at the heart of heaps of the world's best waves. Pipe is just one glaring example. All the French beachies. Puerto Escondido, Nazare, Black's (CA). Almost everywhere in the mentawais. On and on and on. But you do have to have a shoreline that co-operates with the refraction. You can stick sand slugs offshore all you like, but if the shoreline's not up for it, the surf will still be shit.

Interesting how artificial reefs have dropped off the hype radar at just about the same time as wave pools have sprung forth upon it. Artificial reefs were the Old Monorail, wave pools are the new!


what kind of shoreline cooperates with refraction, then?
Drailed wrote:Sound like a load of cunts to me Trev.

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Re: Shearer. Boo. Come in here

Post by Nick Carroll » Tue Jun 20, 2017 4:21 pm

Pipe co-operates with the refraction off the outer logs and third reef pipeline reefs in west swells because of the Pipe-backdoor lava reef slab. If that slab wasn't there the wave would just close out like on the sandbars down near Pupukea. It's fcuked in a north swell because the refraction off those same outer reefs pushes a north swell straight on to the epic Rockpile reef 400m down from Pipe, while Pipe itself is just a small messy closeout. That's a simple example.

I see a bad example of non-co-operation near here at southern Palm Beach. There's a persistent deepwater sandbar well off the beach. It shapes a clean SE swell into a potentially excellent left. But the sand on the inside is often just a dead straight ahallow bar and the wave just instantly closes out despite approaching in a way that hints at what might be but isn't.

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Re: Shearer. Boo. Come in here

Post by carvin marvin » Tue Jun 20, 2017 4:37 pm

Here are my observations of how Illuka break wall works.

You have bland typical closeout bathymetry running from the breakwall along the beach.
The black bathymetric lines in the diagram show the beach depth 1 metre, 2metres , 3 metres and 4 metres.

Image

But the break wall is not straight, it has a long slight bend in it.
This effects the swells by causing the energy to bounce off the break wall and move at an angle in the swell line and as this happens the swell increases in size.
This process starts a fair way out.

The black lines in the following photo indicate the angle of the swell energy relative to the swell line and the increasing number of black lines show the distance across the swell line this energy has moved.

When it gets to a suitable depth it breaks as a peak (red line)and the right hander peels over the bland bathymetry.

Image

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Re: Shearer. Boo. Come in here

Post by crabmeat thompson » Tue Jun 20, 2017 4:38 pm

@nc

So theoretically... they need to add a refraction reef offshore. But the real work needs to be done in close. Like geo sandbags in the shoreline?

What about narrowneck reef? There were some good days out there when the reef was around 6-12 months old.

The shoreline never changed, but waves did.
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Re: Shearer. Boo. Come in here

Post by alakaboo » Tue Jun 20, 2017 4:53 pm

carvin marvin wrote:
Tue Jun 20, 2017 4:37 pm
Here are my observations of how Illuka break wall works.

You have bland typical closeout bathymetry running from the breakwall along the beach.
The black bathymetric lines in the diagram show the beach depth 1 metre, 2metres , 3 metres and 4 metres.

Image

But the break wall is not straight, it has a long slight bend in it.
This effects the swells by causing the energy to bounce off the break wall and move at an angle in the swell line and as this happens the swell increases in size.
This process starts a fair way out.

The black lines in the following photo indicate the angle of the swell energy relative to the swell line and the increasing number of black lines show the distance across the swell line this energy has moved.

When it gets to a suitable depth it breaks as a peak (red line)and the right hander peels over the bland bathymetry.

Image
Carvin you're getting things all mixed up.

The energy and the swell are one and the same. They can't be at tangents to each other.

The black lines in your first image are wrong. They should be on the same angle as the breaking waves, about 45 degrees left of where you've drawn them.
It is shallower next to the wall because it is a lower energy environment. Most of the energy comes from the southeast.

There is also focussing of the offshore swells back towards the breakwater from the sand at the bar. Zoom out a bit and you'll see it in an arc from the southern wall.
Semi-permanent rips also form near the wall as the escaping water can't go south.
The peacock slowly shakes himself out in an act that could be mistaken as effortless were it not for the thought of his withholding a quivering.

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Re: Shearer. Boo. Come in here

Post by Nick Carroll » Tue Jun 20, 2017 6:20 pm

crabmeat thompson wrote:
Tue Jun 20, 2017 4:38 pm
@nc

So theoretically... they need to add a refraction reef offshore. But the real work needs to be done in close. Like geo sandbags in the shoreline?

What about narrowneck reef? There were some good days out there when the reef was around 6-12 months old.

The shoreline never changed, but waves did.
well you just can't tell. Shorelines change over time in relation to distal bottom contours. Sometimes they would re-arrange themselves in response to differing levels of wave energy along a stretch of beach, sometimes not. There's just so much going on and it's all gonna change slowly over the next 50 years and beyond with sea level rise and other effects of global warming.

Maybe the narrowneck reef had a short "shock" effect on the coast but over time the coast absorbed that and just came back to itself.

I just think it's all a waste of valuable time, I mean everyone on here is always complaining about governments wasting money, well what more ridiculous waste of money is there than trying and almost certainly failing to set up reefs for people to surf when there's a fcuken shit load of good waves around already, just go get 'em.

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Re: Shearer. Boo. Come in here

Post by BA » Tue Jun 20, 2017 6:35 pm

Nick Carroll wrote:
Tue Jun 20, 2017 3:18 pm
Artificial reefs were the Old Monorail, wave pools are the new!
Aaaaahhhh, it all makes sense now.

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Re: Shearer. Boo. Come in here

Post by steve shearer » Tue Jun 20, 2017 6:37 pm

alakaboo wrote:
Tue Jun 20, 2017 3:29 pm

The science is solid, but I'm not aware of examples of large sand slugs from high energy environments. If you're going to spend that much, most councils want something that will last more than a couple of years.
Though in practical terms, the ebb tide delta from any trained river is effectively the same, and they work, whether intended or not. That's a big factor in the quality of dbah and TOS.

Your allusion to coolangatta bay/Kirra is a bit misleading given the range of other things that went on, and the sheer scale. In effect they probably buried a pre-existing focussing structure in Kirra reef.

Just to clarify, there's two factors (well more than 2 as i mentioned before about east coast rivermouth/breakwall spots), you have the refraction around the bar (ebb tide delta) and you also have the inshore bathymetry.

when you are pumping sand straight from the beach into that inshore bathymetry as they do permanently at TOS and intermittently at D-bah you have the two phenomena reinforcing each other.
No inshore sand and it doesn't matter how good the refraction from the bar is (a point NC also made using a different example).

Compare that with North Wall and Iluka. Both waves go missing for long periods of time following big swell events when the inshore bars get gouged out. You got a system to feed sand back into the inshore bars and you restore wave quality a helluva lot quicker.
North Wall or Iluka can lie dormant for months after they've been gouged, South Straddy comes back within hours/days of pumping.

So unlike NC, I see that as money very well spent and I think it's that process which should be mimicked. But of course, it's expensive.
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Re: Shearer. Boo. Come in here

Post by alakaboo » Tue Jun 20, 2017 7:32 pm

I agree with both of you, sort of.
I wouldn't do it for shits and giggles like Steve is sort of suggesting as the costs to do things properly are in the 10s of millions, but when there is already a plan to pump/place sand as part of a soft coastal protection strategy, why not try and do it in a way that improves the surf.

I agree with what Steve said about needing both good inshore and deepwater bathymetry, but for mine the key thing is that the distance between the two needs to be sufficient, otherwise you get wide breaking nothingness, ie Coolangatta when (deliberately) overnourished.
The peacock slowly shakes himself out in an act that could be mistaken as effortless were it not for the thought of his withholding a quivering.

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steve shearer
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Re: Shearer. Boo. Come in here

Post by steve shearer » Tue Jun 20, 2017 7:38 pm

Do you mean distance, as in physical distance (ie the offshore bar has to be >100m from the inshore bar for eg), or distance as in distance between the depths of the inshore and offshore bars (ie the the offshore bar has to be >3m deep at mlw)?
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Re: Shearer. Boo. Come in here

Post by Nick Carroll » Tue Jun 20, 2017 7:57 pm

well there is an example of this at the south end of my beach.

South Newport is framed by an exposed rock reef which extends about 400m offshore. beyond this is a series of deepwater bombies which extend about a k out. These bombies refract long interval south swells into a reef break we call "The Pool" which first breaks on a ledge about 300m out.

That 700m or so gap is mostly quite deep water which seems to give the refracted swell a bit of time to regather itself. So by the time it connects with the inside Pool reef it has a fair bit of oomph, though it's not moving as quick as it does on the bombie.

The Pool is shit though it could be epic if the reef had some more structure - but that is by the by - the regathering of the swell after its encounter with the bombie is fascinating. Like if you watch from the cliff overlooking both reefs you can sometimes see individual swell waves merging back into the wave train as they make the trip from the bombie into the Pool. I've blatantly exploited this numerous times to the dismay of other surfers who've been sucked into chasing the first wave of a set, then turned around only to be smashed by the second wave, while watching me catch it.

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Re: Shearer. Boo. Come in here

Post by Nick Carroll » Tue Jun 20, 2017 7:58 pm

poor loofy has probably been flogged by this exact phenomenon

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Re: Shearer. Boo. Come in here

Post by alakaboo » Tue Jun 20, 2017 8:03 pm

The offshore bar ideally is deep enough that the average swell doesn't break, but shallow enough that it can create a focal point on the shoreline.
There needs to be time (distance from the shoreline) for the refraction to have a strong enough effect. As Nick said.

The optimum distance and (change in) depth of the offshore structure (analogous to the curvature of the lens below) is dictated by the wave height and period.
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The peacock slowly shakes himself out in an act that could be mistaken as effortless were it not for the thought of his withholding a quivering.

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steve shearer
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Re: Shearer. Boo. Come in here

Post by steve shearer » Tue Jun 20, 2017 8:12 pm

Copy that.

There's also a highly efficient version of an offshore reef pinnacle refracting certain swell angles at Lennox Point, but fcuked if I'm going to detail it in a public forum.....while it is understood as a Pointbreak Lennox Point is often a true reef break due to the influence of this pinnacle and basalt boulder bottom which extends seawards from the point and forms a natural T-shaped junction - the back button. This'll hold surf up to 12-15 ft before the back pinnacle starts breaking top to bottom.
Saw Herro ride a 15ft wave from this pinnacle one day. And I think Bob McTavish has used it as a take-off once or twice on giant days.
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Re: Shearer. Boo. Come in here

Post by channels » Tue Jun 20, 2017 8:14 pm

BA wrote:
Tue Jun 20, 2017 6:35 pm


Aaaaahhhh, it all makes sense now.

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I have to say, your Simpsons knowledge is encyclopaedic.

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Re: Shearer. Boo. Come in here

Post by Cranked » Tue Jun 20, 2017 8:21 pm

Hahaha. You guys just reminded me of the the racetrack at ulus earlier last year. We had some really torrential rain for a few days. The waterfall in the cave was alltime and a 100m of beach appeared just outside the cave creating a new sandy point break just at the end of racetracks.

So we had the experience of walking out from the cave across a 100m of the new sandy beach to the new sandy point break. Bizarre. Two days later it was all gone.

I've got some pics somewhere.
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Re: Shearer. Boo. Come in here

Post by foamy » Tue Jun 20, 2017 8:23 pm

The classic Simpson's Monorail episode, except for the song, was conceived and written by Conan O'Brien

Classic non-Australian breakwater created waves
Hawaii - Ala Moana, Maalaea
California - Sandspit, The Wedge

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Re: Shearer. Boo. Come in here

Post by The Mighty Sunbird » Tue Jun 20, 2017 8:41 pm

Penis plugs wtf
Erase.

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