Author Topic: Scientific Flatwater Board Testing 101  (Read 27459 times)

PonoBill

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Re: Scientific Flatwater Board Testing 101
« Reply #60 on: June 24, 2016, 04:56:11 PM »
I've been clean for ten years.
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TallDude

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Re: Scientific Flatwater Board Testing 101
« Reply #61 on: June 24, 2016, 05:24:16 PM »
A friend of mine who's a boat designer said that an assumed industry standard of a power boat achieving a point of planing was when the bow wake and the stern wake align (or become one).  I could tell when my windsurf board got to a plane. It would touch rail to rail and be otherwise airborne. I don't even think my skim board was ever actually planing....unless I used it in the UK:)   
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ukgm

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Re: Scientific Flatwater Board Testing 101
« Reply #62 on: June 25, 2016, 12:19:35 AM »
I think I misunderstood Ponobill's explanation a bit,  but the topic is flat water test, hope we will see positive output.

Yes, semantic arguments aside, I would like to get back to this. However, I would like to pick up on a comment someone inferred to in a passing comment earlier - in that flatwater specific boards might not be the best kind of board design for the nuances of mass start racing. That kind of thought would have bearing on any test strategy that was designed. What do people think about this ?

UKRiverSurfers

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Re: Scientific Flatwater Board Testing 101
« Reply #63 on: June 25, 2016, 05:47:48 AM »
Oh, and by he way, since the UK has just voted in a referendum today to leave the European Union, our currency has predictably crashed. So now SUPs are going to be even more crazily expensive here than they ever were. I feel very sorry for the SUP retailers and distributors in this country because they aren't going to be selling many boards in 2017 at this rate. The knock-on effect for the euro and strengthening of the Chinese currency in consequence may also affect board prices more broadly across Europe. Some board brands may have to move their centre of operations out of the UK in order to remain in contact with the rest of Europe - although there are rumours of other countries maybe following suit (eg. Holland) in having an in-out referendum too, so no-one is taking any bets on what will happen to the European dream right now. It's a momentous political, social and economic change and is very likely to impact on the business of SUP for us locally. It didn't help at all that Obama came over here a few weeks ago and told us that we must not leave and threatened us that if we did the US would put us on the naughty step. The UK population sympathetic to leaving basically instantly raised two fingers metaphorically (or maybe one middle digit if they originally came from the US) and told him to go forth and multiply, renewed in their resolve to sever as many ties with their allies as they could.

Anyway, I digress... And the people who voted for the exit from the EU were probably those who couldn't afford a SUP before anyway.

Biggest disaster EVER??

Yes... Just over half the UK population are 'thick s shit' and the just under half have some sort of thought process going on..

You should've had needed to take an IQ test before casting vote!

Im feel totally ashamed to be part of this backward thinking bunch of puppets :(

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ukgm

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Pierre

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Re: Scientific Flatwater Board Testing 101
« Reply #66 on: June 27, 2016, 06:03:47 AM »
Pund crashed? So go and built boards in UK, exports will be cheap and affordable, and british commercial balance awesome, not as France... :P
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Pierre

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Re: Scientific Flatwater Board Testing 101
« Reply #67 on: June 27, 2016, 06:05:38 AM »
Talking back about the topic, UKGM, do you think about comparing different board's lengths? UL vs 14' ?
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Pierre

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Re: Scientific Flatwater Board Testing 101
« Reply #68 on: June 27, 2016, 06:08:07 AM »
Pund crashed? So go and built boards in UK, exports will be cheap and affordable, and british commercial balance awesome, not as France... :P
\HF/- Hi-Fun Hydroworks / custom boards,BZH, since 1982  /  *Link Removed*

blueplanetsurf

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Re: Scientific Flatwater Board Testing 101
« Reply #69 on: June 27, 2016, 06:53:59 AM »

If you want to know if you're planing or not, point your gopro at the tail. If the water is curling up the rails it ain't planing, if it's flinging out, you are. Let's see the pics.

But I'm not going to educate anyone, and most people don't care about this stuff. If you care, read up on this a bit. It's been an important issue in naval architecture and later in board design for the last 50 years. Of all the boards I can picture planing, a 25" wide, pintail 14' downwind board with continuous tail rocker is the second least likely candidate. Right behind an inflatable.
In this photo I'm on a 14' rockered pintail Bump Rider downwind board, going at less than 10 mph.  I'm not sure if planing is the scientifically correct term but I don't think it's displacement, the board is sliding over the surface of the water, not pushing through it, so what would you call this if it's not planing?
« Last Edit: June 27, 2016, 07:35:18 AM by blueplanetsurf »
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ukgm

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Re: Scientific Flatwater Board Testing 101
« Reply #70 on: June 27, 2016, 06:56:57 AM »
Talking back about the topic, UKGM, do you think about comparing different board's lengths? UL vs 14' ?

I'm personally very interested in UL boards but with the racing scene completely redundant in the UK, it wouldn't be the best use of time. I think fin choice and board choice has to be a higher priority for me.

PonoBill

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Re: Scientific Flatwater Board Testing 101
« Reply #71 on: June 27, 2016, 08:55:04 AM »

If you want to know if you're planing or not, point your gopro at the tail. If the water is curling up the rails it ain't planing, if it's flinging out, you are. Let's see the pics.

But I'm not going to educate anyone, and most people don't care about this stuff. If you care, read up on this a bit. It's been an important issue in naval architecture and later in board design for the last 50 years. Of all the boards I can picture planing, a 25" wide, pintail 14' downwind board with continuous tail rocker is the second least likely candidate. Right behind an inflatable.
In this photo I'm on a 14' rockered pintail Bump Rider downwind board, going at less than 10 mph.  I'm not sure if planing is the scientifically correct term but I don't think it's displacement, the board is sliding over the surface of the water, not pushing through it, so what would you call this if it's not planing?

I'd call it "Not Planing", and of course it's in displacement mode. See where the bow wave is, well in front of your feet about where the Blue Planet logo is? See where the stern wave is? Not planing. If you reshaped that board to have a nice big flat spot in the tail it might plane. If you have substantial tail rocker when the bow wave moves back the board becomes a teeter totter. Move it back a little and the tail gets buried.  Imagine the circumstance Talldude mentioned where the bow and stern wave meet with a rockered board. How much energy do you think will be transferred between the board and a bump when the contact area is a line? Have you ever been "planing" on your rockered board when it radically tips forward and back? I haven't. That's what it would do, and it would most likely tip back given the remaining little bit of force.

You need a planing surface to plane. Why does a Simmons board have no tail rocker and a big wide tail? It's not so fat guys with lousy balance can stand on them, it's so they can plane. That's why a short, wide board with that specific Simmons design is fast as blazes down the face of a wave. It planes. Build the same board with anything other than a tiny bit of rocker at the extreme end of the tail and it won't plane. "Regular" short, wide boards with continuous rocker are slugs by comparison. It's also why Simmons shapes are so bitchy about pitch stability--especially to the rear. There's very little secondary stability. You aren't gaining an exponential amount of bouyancy as you sink the tail, it's a flat line.

Look at windsurfing board from the 80's, look at a modern one. We had a hell of a time getting older windfurers to plane. Why? Because they didn't have a planing hull. Talk to any shaper that did both windsurfers and surfboards. Tell him that you think your 14' rockerd board is planing. If he doesn't laugh at you it wil be because he's nicer than me.

It's not speed. It's pounds per horsepower (125 being the magic number) and hull design. You can get a catamaran going 20kts and it won't plane. Never. There is such a thing as a planing catamaran. I remember them. Some outfit in Australia made them. Fun to play with, bitch to control.

Planing is a specifc thing. It's not having a hull that's transversely flattened but has rocker. Call it anything you like, but it still ain't gonna plane. We COULD have planing downwind boards. It's an interesting design choice. I think it might be tough to make it work other places, but in a big bump it could be fast as hell. I think some of the SUP that paddled Peahi this year had planing hulls. I didn't get to look at Kai's board, but it looked very different from the prone guns that follow the traditional big wave design of keeping as much of the rail and hull in contact with big, steep waves as possible.

Sorry UK, if I want to waste my breath a little more talking about this I'll start a new thread, but at least we've not talking about Brexit.
« Last Edit: June 27, 2016, 09:25:45 AM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

PonoBill

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Re: Scientific Flatwater Board Testing 101
« Reply #72 on: June 27, 2016, 09:29:27 AM »
More on topic, I've ordered a stepper motor and controller to build a precision winch. My 360 servo idea didn't work--too wimpy, even with a big metal gear servo. I was going all nutty trying to figure out how to keep speed constant while the winch drum grows in diameter as you add windings when I realized I don't have to. The speed and power recorder will be on the board. Duh. I just need to keep the motor speed constant so there aren't any sudden pulses.
« Last Edit: June 27, 2016, 09:36:09 AM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Pierre

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Re: Scientific Flatwater Board Testing 101
« Reply #73 on: June 27, 2016, 10:07:51 AM »
To summarize, a hull is submitted to 2 vertical forces: weight and its opposite. in static conditions, supporting force opposed to weight is BUOYANCY which is HYDROSTATIC LIFT, defined by Archimede's principle, When hull moves through water other forces occuring at some speed are HYDRODYNAMIC forces due to wave resistance and are lift at the bow and the stern wave, and negative lift at the hull's largest wetted section... those lift forces have a marginal effect as their sum is about zero.  so hull is still supported by hydrostatic lift... we are in displacement conditions.
when  a wide enough  hull speeds up above hull speed, its stern wave moves behind tail and bow wave moves below hull,   weight is supported partly by buoyancy and gradually, partly, by hydronamic lift... If hull is a pure planing hull and speed is enough, generally when stern wave is very far behind hull ( more than 2 or 3 hull's lengths), so to see stern wave a bit behind hull does not mean you are planing, you just start to experience some kind of semi-planing...
On planing condition  weight is supported almost totally by hydrodynamic lift. this occurs on hard chine V-shaped, flat, or concave,  flat rockered wide hulls, at speeds about double of "hull speed" ( depends on hull shape). A planing hull , when on planing condition, Does not need volume to stay on water ( such as wakeboards, water skis, Alaias, paipos, "sinker" windsurf boards...
planing speed depends also on water depth... in very shallow water ( as on a skimboard) planing is easier...
Some saling boats with flattened rounded section can nearly plane, if rocker is very flat and sail power is a lot... a windsurf board planes easier due to flat bottom, but performs less at displacement speeds. motor powerboats are often V-bottomed to avoid slamming and keep control in choppy water, even this delays planing. Hard chines help planing ability.
SUP boards ,if very low- rocker, and if paddled by swift and strong athletes, can reach some kind of semi-planing conditions, hlped by po-up effect due to loss of weight between stroke, excepted on DW with bumps ( or on flatwater with very very srong winds  ::)) but I do not believ hydrodynamic lift is more than half of hydrostatic lift...
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Eagle

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Re: Scientific Flatwater Board Testing 101
« Reply #74 on: June 27, 2016, 04:49:25 PM »
If you want to know if you're planing or not, point your gopro at the tail. If the water is curling up the rails it ain't planing, if it's flinging out, you are. Let's see the pics.
In this photo I'm on a 14' rockered pintail Bump Rider downwind board, going at less than 10 mph.  I'm not sure if planing is the scientifically correct term but I don't think it's displacement, the board is sliding over the surface of the water, not pushing through it, so what would you call this if it's not planing?
I'd call it "Not Planing", and of course it's in displacement mode. See where the bow wave is, well in front of your feet about where the Blue Planet logo is? See where the stern wave is? Not planing.

Tell him that you think your 14' rockerd board is planing. If he doesn't laugh at you it wil be because he's nicer than me.

Planing is a specifc thing. It's not having a hull that's transversely flattened but has rocker. Call it anything you like, but it still ain't gonna plane.

https://www.google.ca/search?sclient=tablet-gws&site=webhp&source=hp&q=planing+hull&oq=planing+hull&gs_l=tablet-gws.3..0l3.2134.6006.0.6655.12.10.0.2.2.0.134.1058.2j8.10.0....0...1c.1.64.tablet-gws..0.12.1061...0i131j0i10.bOEYjzvt1ZM
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