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Variable Rocker Tuning System - Mistral

Created by

Reflex Films > 9 months ago, 22 Jan 2016

Mark _australia

23526 posts

25 Jan 2016 7:26pm

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geoITA said..

Man0verBoard said..

Mark _australia said...

geoITA said..
Flex in the mast tip helps releasing pressure in (otherwise) overpowering gusts. But there is no such thing as a "gust" in the water.

I think there is plenty - sudden sideways (fin) and up.down (hull) loads all the time.

Correct Mark - tail is loaded up when the fulcrum of the chop pushes the zone between the feet and where the dynamic between front and back foot acts as suspension.

Chop = gust in comparison but actually the mast tip is responding to the mass(body weight) connected to the boom and the sailors counter intuitive movements in response to gust, chop..and pushing the front foot which is also critical to trim and responsive to lift generated by air pressure around the board.

Geezus it's all a bit tricky eh?! Some sailors get it - some don't.

the subtle and high response flexing of this tail is so finely tuned...even thinking about it makes it less efficient

In my experience, relative board - water speed varies very little (in both direction and quantity) compared to what happens in a gust. And, most of all, changes are due to variations in board trim (comparable to sheeting in more or less, and/or rake angle changes) but have nothing to do with changes in fluid speed (in both direction and quantity) as happens with a wind gust.
Passing fom a lull to a gust may mean wind changing from say 15 knots to 25. If you assume the board is going on a beam reach at 27 knots, this means relative (apparent) speed changes from 31 to 37 knots (plus there also is a direction change) in few seconds. I seriously doubt that hitting chop may cause anything like that in waterflow changes around board and fin. Expecially when you consider chop hit will give the board a brief impulse, while a gust may last for a few seconds. The trim change due to chop hit will cease in very short time leading (usually) to board and fin having a trim that is not constant, but quickly and slightly variating around a "mean" trim; while a gust, if not dealt with properly, has enough time to alter the ride by much (or to stop it).

It's also funny how until now we used to consider carbon built being superior because of its characteristics of quick response to inputs due to water state, and now are considering absorbing such inputs instead.

Seriously?
Are you telling me that at 40kn and you hit a piece of chop that it does not apply a sudden upwards force to the board?
Anyone who can jump will tell you there is a fair bit of force involved.
Then sideways flex in a fin is on and off a lot, watch a video of it.
As to whether it is the same as a gust hitting a sail, I dunno.
But you said there is no "gusts" acting on a board and I'd say you are very very wrong. The forces acting on the board and fin are just as rapidly changing as on a sail

Man0verBoard

629 posts

25 Jan 2016 7:28pm

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gavnwend said...
This topic is starting to sound to optimistic with a lot of pessimistic chatter.l think we are all left in the gutter with some of us looking at the stars.lets wait for the board to gets some demo's and reveiws by experts.

Bro - it's expert opinions that you don't need..only your own. You know the definition of an expert?

Rob11

240 posts

25 Jan 2016 7:46pm

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Man0verBoard said...

Bro - it's expert opinions that you don't need..only your own. You know the definition of an expert?

We know what a non-expert is... Your comments about head sail movement not affecting board trim are a crock of sh#t

Man0verBoard

629 posts

25 Jan 2016 7:56pm

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Rob11 said...

Man0verBoard said...

Bro - it's expert opinions that you don't need..only your own. You know the definition of an expert?

We know what a non-expert is... Your comments about head sail movement not affecting board trim are a crock of sh#t

Did I say that sail head movement didn't affect(or effect) board trim? That would have been silly, and possibly deserving of abuse

Man0verBoard

629 posts

25 Jan 2016 8:06pm

I'm going to end my engagement here with my learned colleagues however, I'd like to brace the notion that, Pete Thomen will almost certainly be one of those Master Shapers that connects with this design. I don't know Peter, but I know his designs and have drawn similarities between Neil's and his design principles.
These two shapers are in my opinion the quint quintessential of windsurf designers of our time.
In my honest opinion, over and out.

sailquik

VIC

6166 posts

25 Jan 2016 11:51pm

Bugger. Just when I got the Popcorn out and settled in for some fun reading!

Hausey

NSW

325 posts

26 Jan 2016 12:13am

Interesting !

Mistral must have sold hundreds of thousands of boards in the 80's and 90's.

Wonder how many they sold in 2015? As windsurfing got more and more technical, more and more people left the sport. This looks like a great idea - but it isn't going to bring windsurfing back unfortunately.

Neil's custom WindTech boards were magic (as were Thommen's custom F2's). These guys were indeed master shapers and board builders, their boards were so fast and controllable. I remember Neil lent me a board for the Ledge to Lano downwinder race in the mid 90's and it was just so easy to sail off the wind - I'd been stuffing around with other shapers including myself and jumped on what seemed like a magic carpet. Instantly fast and competitive - it was all in the equipment! Neil and WindTech could reproduce fast boards consistently way back then...... when Chris Lockwood was still learning how to sail

Hope it goes well for you Neil!

Wouldn't mind trying it on a kite board!

So Anders Bringdal has done 50 knots on a production board? That's incredible!

izymiester

325 posts

26 Jan 2016 12:15am

I tried the board a few weeks back. Sailed out halfway across from pelican point and back.

In short, the board felt fast, slippery and there wasn't much holding it back from being as fast as any top of the range slalom boards.

It was soft, light and I managed to gybe it in the chop well.

For a narrower tail board it planed early and is probably equivalent to a 5 to 10cm bigger board in power and attributes.

I dare say it would be a good ledge to Lancelin board

geoITA

201 posts

26 Jan 2016 12:52am

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Mark _australia said..

geoITA said..

Man0verBoard said..

Mark _australia said...

geoITA said..

It seems to me we are talking about different things.
I will let you reason about what's different between a gust and a piece of chop.
As for the sideways fin flex, I think it's caused by variations on the backfoot "push" rather than on changes in water speed.
I said that forces acting on board and fin are usually qucker changing than forces acting on a sail.

Apart from that ... yes, we can say that everything that "varies" has something to do with a variation in wind speed (gust). By some extent.

tobyr

69 posts

26 Jan 2016 12:56am

Just got everyone to bed now some time to watch this forum topic heat u….. Oh it's over

Come back Captain Red Thumbs. What happens if they ask for more explanations…

mathew

QLD

2142 posts

26 Jan 2016 10:47am

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Twisted said..
...

The first prototype worked quite well. After filming with a Go Pro on the tail I noticed it flexed less than expected so started to make it more and more flexible, getting better results. Attempts to adjust the flex by air pressure failed, too complicated. And basically it worked good as it was.

A few other problems occurred with other sailors. When freestyling in waves and sliding backwards down a wave, the tail catches and wants to bend down and broke the tail right off where before it was lasting fine. So we put a strap on the top to stop the tail flexing down.

How does it work?
When getting planing, you give mast foot pressure and lean forward, the tail stays straight and gives more lift without drag. As long as you are hooked in, you are applying more pressure on the mast foot. When you unhook, your weight on your feet increases, the tail starts to flex. When you enter a turn, G-forces increase the pressure on the tail and bends more to turn tight without increasing drag, it feels like you accelerate in the turn. In a top turn, the sail helps to give more pressure on your back foot so give the most rocker and tightest turn.

...

Excellent. Even describes some cases where the thing doesn't work.

JonesySail

QLD

1120 posts

26 Jan 2016 11:04am

Here's some more fuel, woossshhh!

mr love

VIC

2415 posts

26 Jan 2016 12:07pm

With a carbon plate across the tail that I assume is made from sheet it must have no V??? Am I correct. Is there V further forward? Just interested.

ozpricey

333 posts

26 Jan 2016 12:19pm

Cool to see someone doing something different, even if it has been tried before. :) I've seen it in the flesh - looks pretty cool.

Possibly too complex/maintenance hassle/corrosion/etc but I wonder if spring/damper setup from RC cars could be applied to provide flex control:

Ian K

4164 posts

26 Jan 2016 12:30pm

Now you're talking. If the idea takes off we'll demand more adjustment than just the bump stop! I remember when the first treadly came out with suspension? Now look where it's gone.

www.bicycling.com/repair/a20016566/bike-repair-how-to-dial-in-your-suspension/

barn

2960 posts

26 Jan 2016 1:36pm

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Man0verBoard said..
What it also does is essentially/virtually shorten the boards tail, in effect. Most top shapers will know(I'm not one..I was taught by one) that the part of the tail behind the fin is useless for trim or speed - it's just unwanted drag - and it's only role is to prevent ventilation to the trailing edge of the fin and the resultant cavitation and spin-out. VRTS eliminates the static section of tail, therefore drag, but maintains separation between air and fin. Problem solved.

I COULD GET IN A LOT OF TROUBLE FOR POSTING THIS TOP SECRET PICTURE

Man0verBoard

629 posts

26 Jan 2016 1:45pm

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barn said...

I COULD GET IN A LOT OF TROUBLE FOR POSTING THIS TOP SECRET PICTURE

Oh Barny, behave!

Mark _australia

23526 posts

26 Jan 2016 2:49pm

^^ I can't even see what that is?
A 1980's pintail, 3 month old rotten Fruit Rollup ,all on top of a Mistral board, surfboard cover and a roll of 3K twill carbon.
Do I win a prize?

Man0verBoard

629 posts

26 Jan 2016 3:24pm

Mark your powers of observation astound me, but not 100% correct. It's a SUP soft cover that happens to fit slalom boards quite nicely

slalomfreak

NSW

304 posts

26 Jan 2016 6:55pm

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Man0verBoard said..

barn said...

I COULD GET IN A LOT OF TROUBLE FOR POSTING THIS TOP SECRET PICTURE

Oh Barny, behave!

Top pic looks exactly like Ken Winners flap from the early nineties.

Man0verBoard

629 posts

27 Jan 2016 4:14pm

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mr love said...
With a carbon plate across the tail that I assume is made from sheet it must have no V??? Am I correct. Is there V further forward? Just interested.

I'll put my 'idiot' credential on the line here and say there will be shape in the bottom centred under the mast track over 1200-1500 of the entry of the rocker.
There could be vee(panels on the rails) through to the start of the plate - reverse spiral vee to flat..in any case there will be in essence vee, or even better, active virtual vee.. following the flex allowed when the plate is pressurised and pivots asymmetrically off the adjuster screw on the centreline.

Well that sounds good to me so why not?! (-: