DW'er from Boulders

Nice vid there Foamballer.
He was flying wasnt he!
They get epic conditions over there the buggers.

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foamballer said..

Looks like a very narrow/long board:

17'4 by 22"

Btw.. IMO reading the water ahead is the same for open ocean.. Bays.. Lakes.. and even rivers.. It's all just water.. We don't have a different kind of water here in Melbourne..

DJ

No disrespect but open ocean to Port Philip is a big difference, wind generated ocean swells of different periods move at different speeds due to the length of the fetch of wind.
The Melbourne DW run starts at the fetch of the wind source where as the open ocean DW run may have a locally generated wind swell on top of an underlying ground swell generated thousands of kms away moving at different speeds of up to 10 seconds or more
Headlands, refracting swells and wind, the depth of water and the fetch of the locally generated wind all influence the local conditions of the DW run you encounter..

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Towny said..

Btw.. IMO reading the water ahead is the same for open ocean.. Bays.. Lakes.. and even rivers.. It's all just water.. We don't have a different kind of water here in Melbourne..

DJ

No disrespect but open ocean to Port Philip is a big difference, wind generated ocean swells of different periods move at different speeds due to the length of the fetch of wind.
The Melbourne DW run starts at the fetch of the wind source where as the open ocean DW run may have a locally generated wind swell on top of an underlying ground swell generated thousands of kms away moving at different speeds of up to 10 seconds or more
Headlands, refracting swells and wind, the depth of water and the fetch of the locally generated wind all influence the local conditions of the DW run you encounter..

Yes.. We are very lucky.. .. You're right.. No doubt there's a big difference.

We choose to use that little stretch of water that starts with zero fetch.. Follows the coastline.. and stays a pretty constant depth.. and if the wind direction is just right it can be very uniformed.. But.. There are plenty of messy open ocean type areas in the bay.. Once we step out of our little section of water it becomes very much like open ocean with very confused waters.. I've done downwinders in these areas plenty of times.. Rickets Point to Frankstone is like this.. Any time we cross the bay it get like open ocean with big ground swell type lumps heading one way and wind made waves heading another.. Plus I've done open ocean type downwinders both on the west coast and the open ocean entering western port bay.. The run from north Merimbula to south Pambula is also open ocean.. Sure it's much more confused and more difficult.. and that's why I choose to use our own nice little Maliko run fom St Kilda to Sandy.. .. I still treat them all the same.. Picking off the little ones and try and line up the big ones when possible.. Looking way ahead.. Not looking at the nose of your board.. and reading the water ahead is still the same.. IMO.. That's what my point was.. Maybe it was a stupid thing to say it's the same.. Also.. I think sometimes my vids make it look much easier that it actually is.. This reminds me of people saying the wind is different in Hawaii.. or the waves are different in Hawaii.. IMO we have places here with very similar type waves.. It just depends on where and where you are comparing.. It's more about comparing apples with apples and it's only when comparing apples with oranges that its different.. Anyway.. There are also plenty of open ocean areas that everything is neat like our little DW run.. It looks like the South African run is similar.. and the guys are now doing the south side of Maui more to get similar zero fetch type conditions.. You just need to find them.

DJ

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antonfourie said..

Towny said..

Btw.. IMO reading the water ahead is the same for open ocean.. Bays.. Lakes.. and even rivers.. It's all just water.. We don't have a different kind of water here in Melbourne..

DJ

No disrespect but open ocean to Port Philip is a big difference, wind generated ocean swells of different periods move at different speeds due to the length of the fetch of wind.
The Melbourne DW run starts at the fetch of the wind source where as the open ocean DW run may have a locally generated wind swell on top of an underlying ground swell generated thousands of kms away moving at different speeds of up to 10 seconds or more
Headlands, refracting swells and wind, the depth of water and the fetch of the locally generated wind all influence the local conditions of the DW run you encounter..

I quite agree with Towny on this, take a ocean swell for example, lets say for arguments sake a 10 second period, that swell is going to be doing roughly 18 km / hour, so unless you can paddle faster than this and up the back of another swell you are never going to catch up a wave in front of you.

As the advice that I got from one of the best, look for the holes and paddle into them.

Most people don't get that..

But watch that vid again from the 5.03 mark.. [the one at the end of all those still shots from the vid that I posted] and see how in 30 seconds he catches a wave that was waaay ahead.. Just keep your eye fixed on that wave.. [the one my yellow arrows point at]

It is hard to get your head around it.. I'm guessing that vid is open ocean.. and not Port Phillip Bay..

DJ

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foamballer said..

antonfourie said..lets say for arguments sake a 10 second period, that swell is going to be doing roughly 18 km / hour.

I'm just curious where you got that speed (18km/hr) from? Is this some standard relationship to the wave period?

If anyone wants some trivia - I did learn today that whitecaps form when the wave height (trough to peak) is greater than about a seventh of the wavelength.

hey by the way, I don't know if you guys have ever looked at these plots available for nsw from new.mhl.nsw.gov.au/data/realtime/wave/#.

They give some really good information on waves. For instance in this example, you can see that the dominant wave energy has about a 7s period coming from between the NNE and SE, but there is also an underlying SSE swell of 15s period, some choppy stuff (5s period) from the NE and some very short period waves coming in from anywhere between N and E. This web page will give you a 48 animation of the conditions for a number of wave rider buoys.

Yeah the rough calculation is period in seconds * 1.5 to get knots, so actually it would be 15kn *1.8 to get km/h = 27km/h so I was a bit wrong in my calc. So for the average 7 second period you would have a speed of 7*1.5*1.8 = 18km/h

Either way you would have to be a supreme athlete to be able to "catch" a wave in front of you even at 18 km/h because you have to paddle up the back of the swell to get on the face.

I think what DaveJohn was seeing was whictecaps breaking in the same place possibly due to something underwater that was why it appears that you catch up with it.

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antonfourie said..

Yeah the rough calculation is period in seconds * 1.5 to get knots, so actually it would be 15kn *1.8 to get km/h = 27km/h so I was a bit wrong in my calc. So for the average 7 second period you would have a speed of 7*1.5*1.8 = 18km/h

Either way you would have to be a supreme athlete to be able to "catch" a wave in front of you even at 18 km/h because you have to paddle up the back of the swell to get on the face.

I think what DaveJohn was seeing was whictecaps breaking in the same place possibly due to something underwater that was why it appears that you catch up with it.

Sorry, Anton, but you are way off the mark here. This is exactly what catching runs/runners/bumps (or whatever else you want to call them) is all about - we are chasing free rides on the ocean swells - whatever their speed happens to be. If you download any gps recorded data from a downwind run you will notice that the speed varies a lot. If you know what you are doing and have the right equipment you will be able to travel at speeds equal to and higher than the speed of the swell. 18km/hr is easy if you know how to catch and keep runs. There are so many variables involved but this is what makes it so much fun.

What DJ is talking about is certainly doable but takes time to work out. This thread was initially focussed on more "Downwind 101" technique, which is why most of us are sticking with recommending a closer focus area and sticking with the smaller runs. The smaller ones are easier to catch and hold and are often used to help get you onto the bigger ones.

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mikeman said..

foamballer said..

antonfourie said..Yeah the rough calculation is period in seconds * 1.5 to get knots, so actually it would be 15kn *1.8 to get km/h = 27km/h so I was a bit wrong in my calc. So for the average 7 second period you would have a speed of 7*1.5*1.8 = 18km/h

I guess that's for 'deep' water, right?

No, period is period ie the time it takes for a wave to move from one crest to another. So, a 10s period means that there are 10 seconds from crest to crest. Generally the higher the period the further away the swell has travelled (Towny describes it well) and the more organised the swell lines become. Also a good rule of thumb is that swell slows down as it gets shallower, which is why the period is shorter.

Sorter period swells are better for shorter boards and vice verse, which is why open ocean downwinds are generally suited better to longer boards.

That's what I was getting at Mike, my understanding is that an ocean wave starts to slow down when it hits depths less than one twentieth the wavelength. So the relationship between the speed of the wave, its wavelength and its period will change. Wave period is quoted a lot, but I've found it hard to find information on the actual speed of waves, hence the question.

My curiosity comes from DJ's hunting down a runner thing. Is it possible to hunt down an ocean swell (once it has passed)? My instincts initially tell me no, but it may well be like sailing and wind speed. i.e. Yes it is possible to sail faster than the wind. By linking runners, I can see that it would be possible to jump ahead from wind runner to runner and hence travel with the swell and run down a runner - it would just take a lot of skill and not a small bit of luck thrown in.

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foamballer said..

mikeman said..

foamballer said..

antonfourie said..Yeah the rough calculation is period in seconds * 1.5 to get knots, so actually it would be 15kn *1.8 to get km/h = 27km/h so I was a bit wrong in my calc. So for the average 7 second period you would have a speed of 7*1.5*1.8 = 18km/h

I guess that's for 'deep' water, right?

No, period is period ie the time it takes for a wave to move from one crest to another. So, a 10s period means that there are 10 seconds from crest to crest. Generally the higher the period the further away the swell has travelled (Towny describes it well) and the more organised the swell lines become. Also a good rule of thumb is that swell slows down as it gets shallower, which is why the period is shorter.

Sorter period swells are better for shorter boards and vice verse, which is why open ocean downwinds are generally suited better to longer boards.

That's what I was getting at Mike, my understanding is that an ocean wave starts to slow down when it hits depths less than one twentieth the wavelength. So the relationship between the speed of the wave, its wavelength and its period will change. Wave period is quoted a lot, but I've found it hard to find information on the actual speed of waves, hence the question.

My curiosity comes from DJ's hunting down a runner thing. Is it possible to hunt down an ocean swell (once it has passed)? My instincts initially tell me no, but it may well be like sailing and wind speed. i.e. Yes it is possible to sail faster than the wind. By linking runners, I can see that it would be possible to jump ahead from wind runner to runner and hence travel with the swell and run down a runner - it would just take a lot of skill and not a small bit of luck thrown in.

I think that the only real way would be if you had a slow ground swell and a howling wind probably 40kts plus or so where you could catch a wind runner onto the slower moving ground swell

BTW

For the period vs speed thing

www.surfline.com/community/whoknows/whoknows.cfm?id=1111

period x crest- minus foam depth, plus under swell scale refraction size divided by 2 times the size of your paddle surface area, add in how you feel on the day out of ten, x the width of your board minus the length of your board














= nothing

sunday morning light sse winds and swell up here. i might paddle up to the supsa comp.

i don't mind light winds sometimes because it's good practise. you have to make the most of every bump.

you'll learn from doing these type of runs too.

anytime in the ocean is well spent