Some discussion on the Luderitz post had me thinking of cost effective ways to temporarily improve our speed flats here in Primbee. Once wind gets beyond 30kts there can still be enough chop in 30cm water to either a) slow you down or b) have you going sideways or worse at speeds above 35kts.

The transient weedbergs seem to be quite effective but only in small patches. I thought that if we could temporarily deploy something at the right angles for the day without risking aquatic life or ourselves it might be worth considering.

So here is my go at version 1.0, all constructive comments or experience from hydrodynamics experts welcome.

Buy some orange PE worksite mesh (comes in 1m x 50m roll for $65). This by itself is probably too floppy to cancel out any chop. Buy some thin bamboo canes (available in 90cm x 6/8mm bundles of 500 for $71) and weave this across the width of the mesh. Roll out this mesh on the water and anchor every metre with a small weight or tent peg. Waves/chop being forced through the mesh because of the stiffness of the canes should help disperse a bit of energy.

Good idea,
I have been also thinking that the cheapest way to achieve glassy water for speed run could be laying some sort of wave absorbing carpet on our bays or lakes instead of digging a permanent channel.
Well, designed sleeve 500 meters long should be enough to create decent speed run.
But I am afraid that plastic mesh about will do nothing to absorb wave energy.
I imagine that 500 meters long sleeve made of inflatable strong material partly filled with water 3/4 and 1/4 air should do the trick.

Imagine that we position plastic sleeve on shallow Lake George or Cootharebe, according to wind direction then fill with water and air.

Maybe even sort of barriers used for the oil spill, can be used?




an additional advantage of our plastic sleeve could be the ability to position, shape, and anchor exactly, optimally to the wind direction.

North or South, East or West - our sleeve could be repositioned relatively easy.


see the difference on each side of barrier.

But If I had to invent something on the budget I will get thousands of milk bottles, partly filled simply threaded on long lines.;
IMO should absorb the wave energy sufficiently and cost nothing.

Select to expand quote

Macroscien said..
instead of digging a permanent channel.

Don't write off the channel. If you minimise it down the the bare essentials it could be much cheaper. You only need enough water for the fin and a film of water for the board to plane on. Shouldn't be hard to find a water truck that can do 50 knots?

Select to expand quote

Macroscien said..
Good idea,
I have been also thinking that the cheapest way to achieve glassy water for speed run could be laying some sort of wave absorbing carpet on our bays or lakes instead of digging a permanent channel.
Well, designed sleeve 500 meters long should be enough to create decent speed run.
But I am afraid that plastic mesh about will do nothing to absorb wave energy.
I imagine that 500 meters long sleeve made of inflatable strong material partly filled with water 3/4 and 1/4 air should do the trick.

Imagine that we position plastic sleeve on shallow Lake George or Cootharebe, according to wind direction then fill with water and air.

Maybe even sort of barriers used for the oil spill, can be used?




an additional advantage of our plastic sleeve could be the ability to position, shape, and anchor exactly, optimally to the wind direction.

North or South, East or West - our sleeve could be repositioned relatively easy.


see the difference on each side of barrier.

But If I had to invent something on the budget I will get thousands of milk bottles, partly filled simply threaded on long lines.;
IMO should absorb the wave energy sufficiently and cost nothing.

They had these sort of barriers on Botany Bay when they were building the Desalination plant, they worked well and where great fun.

Select to expand quote

Ian K said..

You only need enough water for the fin and a film of water for the board to plane on.

Good idea buy a test in practice we need to consider the consequence of unfortunate landing.
If there is any difference in crashing at 100 km/hour on the land as opposed to water?

But surprisingly from your example completely, new sports discipline could emerge.Imagine now that you have this small channel for fin and water just to lubricate like water slides.But this slide is going down sloppy hill kilometer long. Gravity alone propels you at speed, but sail now is used to control balance ( like flaps in airplane)

Select to expand quote

Macroscien said..

If there is any difference in crashing at 100 km/hour on the land as opposed to water?

Not that I'm going to try it out, but more chance of sliding on a hard surface. Might be better off sometimes.



You'll need motor bike safety gear of course.

Select to expand quote

Jetlag said..
Some discussion on the Luderitz post had me thinking of cost effective ways to temporarily improve our speed flats here in Primbee. Once wind gets beyond 30kts there can still be enough chop in 30cm water to either a) slow you down or b) have you going sideways or worse at speeds above 35kts.

The transient weedbergs seem to be quite effective but only in small patches. I thought that if we could temporarily deploy something at the right angles for the day without risking aquatic life or ourselves it might be worth considering.

So here is my go at version 1.0, all constructive comments or experience from hydrodynamics experts welcome.

Buy some orange PE worksite mesh (comes in 1m x 50m roll for $65). This by itself is probably too floppy to cancel out any chop. Buy some thin bamboo canes (available in 90cm x 6/8mm bundles of 500 for $71) and weave this across the width of the mesh. Roll out this mesh on the water and anchor every metre with a small weight or tent peg. Waves/chop being forced through the mesh because of the stiffness of the canes should help disperse a bit of energy.

I don't think that you've got any chop problems at Primbee, it might be faster with a little chop to free up the board. The main issue was the holes in the wind, fix that.

Select to expand quote

Macroscien said..
Good idea,
I have been also thinking that the cheapest way to achieve glassy water for speed run could be laying some sort of wave absorbing carpet on our bays or lakes instead of digging a permanent channel.
Well, designed sleeve 500 meters long should be enough to create decent speed run.
But I am afraid that plastic mesh about will do nothing to absorb wave energy.
I imagine that 500 meters long sleeve made of inflatable strong material partly filled with water 3/4 and 1/4 air should do the trick.

Imagine that we position plastic sleeve on shallow Lake George or Cootharebe, according to wind direction then fill with water and air.

Maybe even sort of barriers used for the oil spill, can be used?




an additional advantage of our plastic sleeve could be the ability to position, shape, and anchor exactly, optimally to the wind direction.

North or South, East or West - our sleeve could be repositioned relatively easy.


see the difference on each side of barrier.

But If I had to invent something on the budget I will get thousands of milk bottles, partly filled simply threaded on long lines.;
IMO should absorb the wave energy sufficiently and cost nothing.

Dunkerbeck used a similar "chop killer" years ago, seemed to work well. I think the only issue was anchoring it to the sea bed, it keep't moving. Naish, Bringdal and Albeau participated in the open sea speed event, got a dvd some where.

Just to be clear, I was talking about laying the mesh flat on the water, not standing upright.
All of those spill booms I looked at were very expensive per metre.

I've been thinking about this as well - some sort of coarse brush, like you get on a steeple case jump.

Something to slow the wave energy down but not to stop it. This might stop the build up on the windward side of wave energy and other stuff affecting the structure.

some sort of PVC (or other material) pipe with coarse brush spikes sticking out of it, that could be towed into place

Select to expand quote

Jetlag said..
Just to be clear, I was talking about laying the mesh flat on the water, not standing upright.
All of those spill booms I looked at were very expensive per metre.

I agree that net could work well. We need to devise that absorbs wave energy and disperses. take energy from one place (top of the wave and transfer to another place at the bottom) .It could be the quite interesting subject of experiments what structure could be the most cost-effective to do just that.

Did you try to float that net to check what effect it is on the smoothing waves?Indeed it seems logical that rigid net should be more efficient than just soft floating.It could be quite interesting subject to marine engineers ( for sure already done in depth) . The most cost-effective barrier/ absorber for waves.
I wonder how it may work for example simple long carpet say 1 meter wide and then floating along? But our material should be also durable / last for years

Olympic size pool lane ropes

Select to expand quote

Jetlag said..
Just to be clear, I was talking about laying the mesh flat on the water, not standing upright.
All of those spill booms I looked at were very expensive per metre.

just create an oil spill using food grade hydraulic oil(safe) and they will setup the booms for free

Or maybe we need some sort of acoustic sounder on the nose of our boards to get some sort of spectral signature of the chop being traversed. A Fast Fourier Transform sort of algorithm? This would be recorded at 1 second intervals in the same file as the GPS speed at each instant. All chop will have a distinct spectrum of course but they could be divvied up into categories. Your local spot may only produce categories 3B, 4A and 5C. In category 5C a 28 knot 2sec may be the worlds best.

At the moment there is only one category where you can be realistically compared with anybody else. category 1A - dead flat. Hence this quest for flat water and manipulation of flat water. Where will it end?

Select to expand quote

kato said..

Jetlag said..
Some discussion on the Luderitz post had me thinking of cost effective ways to temporarily improve our speed flats here in Primbee. Once wind gets beyond 30kts there can still be enough chop in 30cm water to either a) slow you down or b) have you going sideways or worse at speeds above 35kts.

The transient weedbergs seem to be quite effective but only in small patches. I thought that if we could temporarily deploy something at the right angles for the day without risking aquatic life or ourselves it might be worth considering.

So here is my go at version 1.0, all constructive comments or experience from hydrodynamics experts welcome.

Buy some orange PE worksite mesh (comes in 1m x 50m roll for $65). This by itself is probably too floppy to cancel out any chop. Buy some thin bamboo canes (available in 90cm x 6/8mm bundles of 500 for $71) and weave this across the width of the mesh. Roll out this mesh on the water and anchor every metre with a small weight or tent peg. Waves/chop being forced through the mesh because of the stiffness of the canes should help disperse a bit of energy.

I don't think that you've got any chop problems at Primbee, it might be faster with a little chop to free up the board. The main issue was the holes in the wind, fix that.

Can't fix flukey NSW westerlies mate.

Select to expand quote

mark62 said..
Dunkerbeck used a similar "chop killer" years ago, seemed to work well. I think the only issue was anchoring it to the sea bed, it keep't moving. Naish, Bringdal and Albeau participated in the open sea speed event, got a dvd some where.

Disagree: The 'Chop Killer' was a failure. At best it helped smooth the very tiny surface chop on top of the waves, but the waves come under the floating structures. Watch the videos again and you can see their boards are bouncing like crazy, and they have some frightening crashes. And they didn't go on with the experiment.

The Oils booms would be little better if they simply float on the surface. The mesh fence would be no help either for the same reason. The waves simply pass through/under it. To stop waves, a barrier has to extend below the surface to at least the depth of the wave circulation (I think this is approximately a bit more than the height of the wave). So a water filled 'oil boom' that is semi submerged may work, especially of it has enough mass to absorb the wave energy, but nothing that floats on the surface will make any significant difference.

Your best bet is still to take the cue from nature: Artificial weed. I proposed this a few years ago, Plastic fronds attached to a mat in the bottom the extend almost to the surface. I had not thought of the steeplechase jump material as a source. That is a great suggestion and might be readily available and affordable, especially if you can get the old stuff when it is discarded. I also proposed that it might not have to be a continuous mat, but that regularly spaced lines of the fronds might be enough. This is what they need in the Luderitz Canal to kill the following shop when the wind angle is over 130 degrees. In the strongest winds, broader angles than 135 are faster in Theory, but in practice the water gets dangerously choppy with following wave trains running along the channel. Solving that issue might see another jump in possible record speeds. Seb obviously saw the problem in Luderitz and did some experiments with floating mats in 2014 or 2015. But they did not seem to be successful.

So my suggestion is to get some contacts at the Racecourse's and see if you can obtain some of their old steeplechase jumps. Cut them into the right depth length and see if they make a difference. The fins should go through them with little or no noticable resistance.

Select to expand quote

Ian K said..
At the moment there is only one category where you can be realistically compared with anybody else. category 1A - dead flat. Hence this quest for flat water and manipulation of flat water. Where will it end?

I agree - it would be good if there was some way to measure or classify chop and therefore be able to realistically compare speeds.
Everyone has easy access to choppy waters

Motorboard proppelers could modify the surface temporary.
It may be time and energy consuming to run the water track , grooming device but definitely could prepare surface for one-off record run, jets ski pr similar.
On another hand chasing is common on dogs racing, jetski use by big wave surfers.



As to devices to consume wave energy I think maybe some inflated but the sink to the bottom devices may work.
We could do such experiment in a small pool - sink partly inflated air matter race using weights.

I can imagine that wave will have big trouble to go over a soft bottom that will collapse under the incoming wave. I could imagine our air matter race device to accept energy from the top peak of the wave and transfer to the lower point our waves.Possibly to smooth very shallow channel, we don't need very thick air coushins, Maybe just few cm can do the trick? It could have the format of our popular bubble matt, but with two bubbles strategically connected so when you press one, the air is pumped to another on at the distance.This device should be quite easy manufactured simply by thermal joining two ordinary PVC sheets or rolls - same as sold by Bunning black stuff. We just run hot roll pattern to join two sheets to create bubbles pairs patterns. Then whole matterace are will partiallytly inflated and then sink flat at the bottom of our channel - using, for example, cheap steel mesh used for concrete reinforcing.

Has anyone mentioned the lane ropes in a pool? They are partly submerged and stop interference going into the other lanes.

Blue plastic 44 gallon drums would be ideal you can pick them second hand for $10
www.google.com.au/search?q=plastic+44+gallon+drums&rlz=1C1CHMD_enAU550AU550&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiNovCezYjXAhUGJpQKHYnJCxMQ_AUICigB&biw=1075&bih=569#imgrc=OsA-8NER9GYgRM:

Select to expand quote

BSN101 said..
Has anyone mentioned the lane ropes in a pool? They are partly submerged and stop interference going into the other lanes.

Yep

Stuthepirate said..
Olympic size pool lane ropes

I don't think that anything proposed would work. Refer the following URL

www.coastalwiki.org/wiki/Floating_breakwaters

A floating breakwater would need to be either:
- a rigid structure at least half the width of wave length or
- a structure with sufficient mass to have a natural period of oscillation that is longer than the waves
otherwise it would just bob up and down as the waves past under it.

Select to expand quote

John340 said..
I don't think that anything proposed would work. Refer the following URL

www.coastalwiki.org/wiki/Floating_breakwaters

A floating breakwater would need to be either:
- a rigid structure at least half the width of wave length or
- a structure with sufficient mass to have a natural period of oscillation that is longer than the waves
otherwise it would just bob up and down as the waves past under it.

This is not entirely true. About floating breakwaters.
I think that floating rigid breakwater that is firmly attached to the bottom could do the job too.
This anchoring will substitute for large mass that is needed otherwise.
But here is completely useless because tides will require constantly adjusting the length of that teether. I still opt for my idea of sank at the bottom air channels. For a technical reason: There are completely invisible, do not obstruct passage.
Our underwater water eater simply transfers energy half a wavelength and could be installed be the entry of the port to protect water and ships inside, along the beaches to protect banks. I can imagine that could be installed as solid permanent structures for industrial water protection. In such case, labyrinth/ of underwater siphones filled with air should be able to smooth area above.


This is mechanism how my wave-eater should work in principle at least>Maybe I should apply for patent first ( before publishing here )

Select to expand quote

John340 said..
I don't think that anything proposed would work. Refer the following URL

www.coastalwiki.org/wiki/Floating_breakwaters

A floating breakwater would need to be either:
- a rigid structure at least half the width of wave length or
- a structure with sufficient mass to have a natural period of oscillation that is longer than the waves
otherwise it would just bob up and down as the waves past under it.

Recall that my original post was about making already good spots into awesome spots, not stopping large chop. We are already in water less than knee deep and even loose clumps of weed are very effective at forming glassy patches behind them. Even stringing out a small net to help build up a wind blown weed mat might be enough. Wavelengths I'm talking about are 1m or less.

sailquik is right. The main problem on a 135+degrees-run is the running swell or rolling chop you have to overtake from behind. So artificial weed should be the solution.

Select to expand quote

Jetlag said..

John340 said..
I don't think that anything proposed would work. Refer the following URL

www.coastalwiki.org/wiki/Floating_breakwaters

A floating breakwater would need to be either:
- a rigid structure at least half the width of wave length or
- a structure with sufficient mass to have a natural period of oscillation that is longer than the waves
otherwise it would just bob up and down as the waves past under it.

Recall that my original post was about making already good spots into awesome spots, not stopping large chop. We are already in water less than knee deep and even loose clumps of weed are very effective at forming glassy patches behind them. Even stringing out a small net to help build up a wind blown weed mat might be enough. Wavelengths I'm talking about are 1m or less.

Maybe, but unfortunately, anything that floats just on the surface, as the wiki says, will allow the waves to pass virtually unhindered. The reason the weed works is that it attached to the bottom of the lake and effectively inhibits the underwater circulation of the wave and stopping the wave from forming.

Jetlag, it sounds like you are seeking a glassy water state. I have not sailed your spot, but the PiT sailors who have say that it is probably flatter than the fastest part of the speed strip at Sandy Point. That sounds pretty good to me.

Select to expand quote

Macroscien said..
Motorboard proppelers could modify the surface temporary.
It may be time and energy consuming to run the water track , grooming device but definitely could prepare surface for one-off record run, jets ski pr similar.
On another hand chasing is common on dogs racing, jetski use by big wave surfers.



As to devices to consume wave energy I think maybe some inflated but the sink to the bottom devices may work.
We could do such experiment in a small pool - sink partly inflated air matter race using weights.

I can imagine that wave will have big trouble to go over a soft bottom that will collapse under the incoming wave. I could imagine our air matter race device to accept energy from the top peak of the wave and transfer to the lower point our waves.Possibly to smooth very shallow channel, we don't need very thick air coushins, Maybe just few cm can do the trick? It could have the format of our popular bubble matt, but with two bubbles strategically connected so when you press one, the air is pumped to another on at the distance.This device should be quite easy manufactured simply by thermal joining two ordinary PVC sheets or rolls - same as sold by Bunning black stuff. We just run hot roll pattern to join two sheets to create bubbles pairs patterns. Then whole matterace are will partiallytly inflated and then sink flat at the bottom of our channel - using, for example, cheap steel mesh used for concrete reinforcing.

Don't get me wrong Macro, I am in no way compianing about the picture here, (that would definitly be a great way to get up a ski hill), but did you actually mean to post another one? Maybe of a jetski?

Mal Wright told us in 2006 that we should try running directly behind a Jetski which will flatten the waves for us. We didn't get around to trying it because at that time we didn't know anyone with a Jetski. He was right though.

Select to expand quote

sailquik said..

Don't get me wrong Macro, I am in no way compianing about the picture here, (that would definitly be a great way to get up a ski hill), but did you actually mean to post another one? Maybe of a jetski?

Ratrak was used as a metaphor here - to smoothen terrains. But you are right, jetski is exactly what we need to lay smooth path of water in front, although quite easy to be distracted sometimes.

Besides that, water behind is mixed with air bubbles behind a motorboat. We don't really know how it may affect water resistance but it could happen that suddenly such foam could be much faster than dense water.

Select to expand quote

Ian K said..

Macroscien said..
instead of digging a permanent channel.

Don't write off the channel. If you minimise it down the the bare essentials it could be much cheaper. You only need enough water for the fin and a film of water for the board to plane on. Shouldn't be hard to find a water truck that can do 50 knots?

I think making the canal narrower is a good way to avoid rolling chop. L?deritz 2011:

Select to expand quote

Dr Speed said..

Ian K said..

Macroscien said..
instead of digging a permanent channel.

Don't write off the channel. If you minimise it down the the bare essentials it could be much cheaper. You only need enough water for the fin and a film of water for the board to plane on. Shouldn't be hard to find a water truck that can do 50 knots?

I think making the canal narrower is a good way to avoid rolling chop. L?deritz 2011:

Its a wonder why they dont put in a few speed runs next to each other. Looks like there would be enough room for at least another.

Drag races! 3,2,1, go!

The other runs could be on different angles too to make the most of conditions.

But too scary narrow for me!

I wouldn't completely dismiss to possibility of the original post idea being able to kill of the last 15 to 20 cm of chop. Certainly worth the 136 bucks and some string and about 10 or 20 bricks to give it a go over a 50 meter section.

On the down side, I'd want to be sure that those sticks were tied on properly and that I didn't end up crashing in to that lot. Still, probably more comfortable than the concrete wall at West Kirby.