Looking on video and recollection our own high speed crashes I may ask :



Why nobody invented yet harness lines with " safety fuse" ?

In the same manner that every skier is protected in the event forces exceeds setup limit, our harness lines should also have one day
limiter that automatically release one end of the harness line in the case of catapult for example.

Obviously force is much higher that during ordinary sailing. I have few carbon booms broken and aluminium seriously bent.

Can be done ? Or was already tested ? Doesn't work in real life ?

No thanks, I'll have my harness line fixed. In that crash Matt forgot that water and sand are different to sail on . A shorter fin or deeper water would have stopped that crash

www.seabreeze.com.au/forums/Windsurfing/Gps/High-Speed-Crashes/?page=1

ok I see now, that subject was already extensively discussed in year 2008.
Now is 2015 and we still can't to to our windsurf shop and buy simple harness lines with break away pin.
Seems you had really good idea, that may really work.

Are the forces generated during a catapult really higher than hooked in sailing?

Sure, they are at the end, but at that point its too late and in some ways its better to stay hooked.

Although there is an art in the falling, and I much prefer the 'I will hold onto the boom so I know where it is' technique.

And the other worry about coming unhooked, is what happens to ankles/legs, if the feet don't also come out of the straps.

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decrepit said..
And the other worry about coming unhooked, is what happens to ankles/legs, if the feet don't also come out of the straps.

you are right , the same should apply to foot straps eventually.
I remember already landing very uncomfortably with foots in the straps.
In my earlier older board screws simply pop out of the plastic thread and use to replace regularly with inserted plastic plugs to hand something in brick walls , from Bunnings.
So plastic thread simply gave up upon extreme forces.

I think that final solution, soon to be available should be based on stainless steel spring mechanism with precise regulation of the force/ moments/ torque to dismount the line.
As the problem is completely neglected now , in few years time we will be talking here, in this same place about very precise settings. Tables that involve your weight, speeds and skills to setup fuse properly in Newton forces.
Hopefully we will be able to save many ribs, booms and penetrated sails on several dollars device.
Imagine : If you could for extra $50 have assurance that your harness line will dismantle at crash- would you rather save and stick to existing hard wired lines ? Compare this to ski rider- If anybody this days agree to have his boots bolted and glued permanently to the ski?
Now is the best time for those engineers to find the best design of regulated safety fuse, that could be easily re- attached.

I imagine that one of of harness line could be similar to that used in my bicycle locking, anti theft line.
Then spring loaded mechanism to release to precise force. If whole setup require screwdriver to change settings that should be still ok.

Maybe that is a chance for one of our smart Aussie mate to take the matter seriously, finish the design, patent it and start producing in his garage/ workshop.
In year or two Lauderitz speedsters will all be wearing his safe harness lines.
Same but simpler should be found for foot straps.

If too difficult for single person , maybe one the that windsurfing accessories manufacturer should look on opportunity here.

Take the devil you know. The full on unexpected hooked in catapult is mostly not a bad way to crash. Sort of a half forward roll to a back slap. I've been more shook up in the dismounts I've seen coming. If you sort of unhook land reversed/upright you can get a good bit of whiplash.

Harness lines with a random release? No thanks.

Considering that link I posted is now 7 years old and that I believe I am a much more competent sailor than I was then (as I had only just got back into it), I really don't think I have a need for breakaway harness lines and agree with others above. As Ian K said, harness lines with the potential to let go at random would pose a bigger issue in my (as at 2015) mind.

That is more intuition then facts.
I would rather to prefer experiment.
Have this to options to choose and then decide which one is better.
We have plenty evidences of the broken booms , masts ribbs now, but we don't know how it could compare if safe harness lines were available.

The same with helmet . Is optional and some to choose sail with, others without.
But nobody could question safety and claim that helmet actually brings more harm.

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Ian K said..
Take the devil you know. The full on unexpected hooked in catapult is mostly not a bad way to crash. Sort of a half forward roll to a back slap. I've been more shook up in the dismounts I've seen coming. If you sort of unhook land reversed/upright you can get a good bit of whiplash.

Harness lines with a random release? No thanks.

Mechanism during the catapult will be exactly the same as today, if you thing about this closely, Ian.
But maximum moment of force will be limited in that milliseconds that must decide what must to go: boom, harness line, your bones or tendons ?

Safety release is not intended as soft and comfortable for bumpy ride but ultimate protection against ultimate harm - like you air bags do not deploy until completely necessary.
I imagine that forces during catapults do exceed limits in exactly the same way and point as today, so you will tumble, roll, exactly as you do today but in critical moment line will snap/ release prevent breaking something, prevent something worse.
I am guessing that forces during catapult could be as much as 10 x as during the worst bumpy sailing maneuvers. So our limiter could be setup somewhere in the middle like 2 - 3 x the maximum expected during bumpy ride.

To start our experiment we should try one day attach electronic logger recording forces on the harness line during PWA slalom session like race. This should give us an idea what we could expect. If somebody from tester dummies could simulate crash that even better for our science of windsurfing.


If we study mechanism of the Matt's ( typical) crash:

1.The max force will not be at 1 photo, when unfortunately

such line release will be the most helpful



2.Will not be during the flight through the air





img]


3.But the moment he hits the water










4.Lucky for him he was somehow accidentally released form harness lines free and keep going/ flying skimming the water with minimal deceleration.
Otherwise he would need to stop from 70 km/h to 0 in the matter of centimeters not a meters.

Some time ago had a look at harness line forces using an instrumented spreader bar - turns out in cross-wind sailing on small chop the harness line force averages about half your body weight, with spikes up to around your full body weight on the bumps. Didn't log any crashes though.

eg Results for an 82kg sailor:

(For details see Walls, J.T, Gale, T.J. (2001). ‘A technique for the assessment of sailboard harness line force.’ Journal of Science in Sport in Medicine, 4(3), p348-356.)

Excellent science ! That is what we need to have a look at more extensive sailing conditions ( including crashes obviously )

You should borrow your instrumented spread bar to the beginners and that will be sufficient to start with our experiments.

Will be very interesting to know more details about your instruments. How is was made etc, maybe picture.

Very interesting.
I have interest to measure forces at different points or our windsurfing equipment. For example what are forces at the mast base to propel us at different speeds, forces on fins in all 3d directions etc

I wonder if somebody calculated what is our max power excreted by sail expressed in kW or HP?

is it something like 2 HP ? or 10 HP ??


If we can have one day complete picture of the forces during windsurfing that will be excellent.

Sailing in shallow water is always risky, but speed sailors accept this in their quest for better speeds. The best way to avoid a painful catapult is to watch out for shallow water and practice your sailing as much as possible. The more you sail the less you catapult I have found. It only happens rarely now for me, normally as the result of a collision with a stingray.

The solution is very simple: just put the hook the other way round so that the open side looks to the sky. So you will release automatically.

Being one of the rare few who sail hook up I have to disagree with this ^^^^^
I still have great catapults!! I think if you get flung even at 20 knots board speed you arent going to unhook.
At speeds over 30 it hurts and happens so quickly you are just along for the ride.

Theoretically we could leave harness lines intact and make hook on spread bar "Active"
to open.

But then hook must be such shape - do not present even bigger danger as straight, easy to inpail .

Definitely there is plenty of room for improvement on this end - hook.

My main complain will be frequent and unneeded unhooking during the ride on chop.

If somebody come with solution or improvements of that simplest so far part of our gear.

So somebody may come with solution to modify the hook in such way that :

- we could still easy hook in and off

-accidental / unintentional un-hooking is prevented during ordinary sailing

- hook ( spring loaded for example) open temporary upon excessive forces.

On another side , self re-lease, and easy during ordinary fall the most critical to save us from drowning - and complicating that hook design that works fine now may not be worth the risk.

As I remember it from 2008-9, Tom Chalko refined his 'breakaway' harness lines to the point where they would not break in normal sailing use, but would break when he has a crash load in them.

He used kite line in a bundle, and he added more lines until he found the right strength for his weight. I think the strength would be different for each persons weight.

Regarding releasable footstraps:

Waaaaayyy back in the '80's I obtained a 'Look' footstrap with an adjustable spring loaded breakaway system. I think it is still installed on one of my old speed boards.

For those of you not into the snow sports, Look is a ski binding manufacturer and has a lot of experience building release ski bindings (and perhaps now pushbike shoe systems?)

Now I think of it, I have have bought two of these and there still may be one in it's box in my Museum!

The problem with it was that it did not completely release at one side. It just made a bigger loop that would enable your foot to slip out. Unfortunately, it could also let your whole leg plunge trough the loop with potentially disastrous consequences!

They did not catch on.

Found this pic. Not very clear because it is severely enlarged and cropped. I will get a better one.

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Macroscien said..

If we study mechanism of the Matt's ( typical) crash:

1.The max force will not be at 1 photo, when unfortunately

such line release will be the most helpful



2.Will not be during the flight through the air





img]


3.But the moment he hits the water










4.Lucky for him he was somehow accidentally released form harness lines free and keep going/ flying skimming the water with minimal deceleration.
Otherwise he would need to stop from 70 km/h to 0 in the matter of centimeters not a meters.

In my experience, the line/harness breakage occurs at the moment of your second freeze frame when the mast hits the water (and severely decelerates). This can be before the body hits the water. Here he is already parted company with the boom:



I am pretty sure his harness lines snapped, along with his harness and boom as well in this incident.

No damage to anything on that crash, just embarrassed

One way around the hooked in catapult would be to reverse the hook/harness line situation. I have thought a bit about this but never tried it mainly due to apathy on my part but it goes like this. Have a hook on the boom-facing up on top of boom (you could even have a couple for upwind /downwind balance points ) and the harness line on your harness. Advantages being 1) less aero drag as no leeward harness line upsetting flow over sail. 2) Half the cost of harness lines. 3) catapults over the boom should be an automatic release. Matt may be the perfect guy to test this. No responsibility taken for any unforseen consequences :-))

Now there's an original idea YoYo although I reckon point load on the boom would be a worse situation than spread load from harness lines. I used to position my harness lines touching but had a few breaks which I believed was from continual point loading so I now spread them about 15 to 20cm apart. I'm trying to get my head around how hooking in and out would occur with your idea.

Out of interest do those clip harness lines breakaway in big crashes?

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Macroscien said..
Excellent science ! That is what we need to have a look at more extensive sailing conditions ( including crashes obviously )

You should borrow your instrumented spread bar to the beginners and that will be sufficient to start with our experiments.

Will be very interesting to know more details about your instruments. How is was made etc, maybe picture.

Very interesting.
I have interest to measure forces at different points or our windsurfing equipment. For example what are forces at the mast base to propel us at different speeds, forces on fins in all 3d directions etc

I wonder if somebody calculated what is our max power excreted by sail expressed in kW or HP?

is it something like 2 HP ? or 10 HP ??


If we can have one day complete picture of the forces during windsurfing that will be excellent.

I reckon Windsurf companies should give proto gear to beginners for testing. Especially ones that get ambitions and capabilities mixed up regularly.

I haven't broken a harness line yet. But anything attached to the lines ally or carbon has been put to the sword. When I did break a carbon boom there was a section missing about 300mm long where the lines used to be (broke in two spots) so having a sacrificial point might have saved a perfectly good boom and having to sail back to the car very cautiously.

If you buy yourself one of the original NP automatic harness, it had a built in safety release - the automatic model that has the serrated teeth strap and clip mechanism.

the teeth were too small, so if you had a good stack the harness bar rips out. the only down side is that you lose the bar. :)

Sailquik's reference to the Look footstrap reminded me that there was a Look harness line safety realese back in the late 80s.
Eric Beale had developed it with them and he gave me one to try in 87 but i rummaged through my old gear in the garage and it is gone now.
It was a small device [in the signature Look blue and gold] that was integrated into the harness line back in the day that harness lines were rope!
There was a tapered pin that engaed with a corresponding contracting socket than had a threaded collar that you wound in or out to determine the pressure at which the pin relaesed from the socket.
I never used the sample that Beale gave me and it is not on the Look website anymore [28 year on].
The concept seemed sound but in never caught on.

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sausage said..


Out of interest do those clip harnesslines breakaway in big crashes?

Nope. I've used the clip harness lines for the last couple of seasons and done some spectacular over the handle bars action without the lines breaking (only the nose of the board smashed off). They're tough despite being plastic.

You can see the Look safety harness line I referred to above in this recent pic of Beale.
Clearly he still has some stock!!

I've used a reactor bar for years and because of the roller instead of hook separation in a crash happens with ease.

I thought about this a while ago and came up with this a hook so its angle depndant rather than force dependant . the attatchment to the boom would have to be very sequre with grip on the back to make sure it didnt rotate as you fell though