Author Topic: Optimal width of a downwind board  (Read 15361 times)

PonoBill

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Re: Optimal width of a downwind board
« Reply #15 on: May 30, 2015, 07:01:45 AM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.

Neither statement is right. Planing means a hull rises over the bow wave, not it's wake, which certainly happens on many bumps.
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Eagle

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Re: Optimal width of a downwind board
« Reply #16 on: May 30, 2015, 08:41:47 AM »
As in a boat - or on a SUP > you need enough speed to get out of displacement mode to get on plane.  Generally your bow wave needs to be happening about midpoint and the boat or SUP is going faster than the wave.  Livio and Danny are planing in the pic earlier in this thread.  What we like most about DW and surfing is the planing aspect overtaking waves - not staying in the trough and gliding at wave speed.

The F-16 and M-14 do this well as once the heavily rocker bottom releases - the board takes off like a rocket and you fly to the wave ahead.  The Touring Carbon - Bullet 14V2 - and Dominator also do this but at a much lower speed.  The benefit with the DW boards are they pearl less and are very stable compared to racing boards like the 2013 Sprint in the video.  Was very close to buying the 25" Sprint until I used it on a quick out and back - and it was too hard to stop and stay upright in moderate cross chop and slop.  We like boards that are stable in AW conditions so 27.25" is ok - but probably the 26.5" Bullet 14V3 is near optimal for a rider with non-alien skills.

http://en.m.wikipedia.org/wiki/Planing_(boat)

"To plane, especially to initiate planing, the power-to-weight ratio must be high, since the planing mode of operation involves moving the hull at speeds higher than its natural maximum speed when in displacement mode (Hull speed). All boat designs for planing benefit from minimised weight; planing powerboats are commonly made from light alloy or use other reduced-weight construction techniques- RIBs are typical examples. Planing sailing boats need a good sail area and powerboats need a high-power engine. Steps and Chine (boating) ridges may also be incorporated into the design to encourage both ease of planing and stability. Most surfboards are planing or semi-planing hulls that utilize the push of the waveform more or less in combination with gravity and specific angles of attack for the airfoil to maximise propulsive force and reduce the net downforce and thus achieve planing lift."

Oh off-topic - tested our 16' canoe yesterday afternoon and it was amazingly stable and easy to paddle standing as a SUP.  I was standing at or below water level which lowered the COG at lot - the rounded fast hull worked a charm.  Only problem was you could only get around 3 paddle strokes per side.   :'(  Also had our pup along for the ride which was a bonus.  :)
Fast is FUN!   8)
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Eagle

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Re: Optimal width of a downwind board
« Reply #17 on: May 30, 2015, 11:29:00 AM »
Here are some pics of our little SUP canoe test -
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headmount

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Re: Optimal width of a downwind board
« Reply #18 on: May 30, 2015, 11:40:49 AM »
Here are some pics of our little SUP canoe test -
Width of canoe?

Area 10

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Re: Optimal width of a downwind board
« Reply #19 on: May 30, 2015, 12:20:44 PM »
Looks like the Starboard K15. That was a great board for long distance cruising and racing.

Eagle

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Re: Optimal width of a downwind board
« Reply #20 on: May 30, 2015, 12:28:19 PM »
Here is the We-no-nah link to the Adirondack canoe model in the pics - it is about 20 yo with some faded gel but a pristine interior -

https://www.wenonah.com/Canoes.aspx?id=51

If you look at their solo race canoes > their designs pushed the speed limit fairly far.
« Last Edit: May 30, 2015, 12:30:49 PM by Eagle »
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stoneaxe

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Re: Optimal width of a downwind board
« Reply #21 on: June 02, 2015, 08:35:45 AM »
I know we can discuss all the variables and the science but its really pretty simple. Optimal width=Personal ability to stay upright (most of the time) in the current conditions while still catching glides.
Bob

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UKRiverSurfers

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Re: Optimal width of a downwind board
« Reply #22 on: June 08, 2015, 11:59:11 AM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.

Neither statement is right. Planing means a hull rises over the bow wave, not it's wake, which certainly happens on many bumps.

Oops - Bow wave I mean..

Rises over and not over takes??
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paddlestandingup

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Re: Optimal width of a downwind board
« Reply #23 on: June 08, 2015, 05:37:01 PM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.

I'm not sure.. Yes you can ride a bump and not be planing.. but you can also be fully planing on some bumps IMO..  :)
Well, certainly you can do what I call "surge-riding", which happens quite a lot with raceboards that don't plane easily - you are definitely getting a push but you are sitting high on the bump and going at the same pace as it. But what I think of as downwinding is an experience that is pretty much indistinguishable from surfing: the board is moving far faster than the bump and this allows you to plow over the bump in front and into the next trough, and so on. The board feels loose and free, and is throwing up spray at the sides and you need your foot over the fin to move it around to avoid poking the nose into the bump in front. So I don't know if that is what you'd call planing, but that is what I'm aiming for in my downwinding. You can connect bumps by turning and following the direction of the troughs, or you can do it by getting so much momentum up that you are skipping over them, and that's when the real excitement happens, to my mind.

I think this is a fine explanation of the "point" of downwind SUP.  Contrary to what Area10 wrote, I've heard people say that you never want to go up the backside of the bump in front but when we are linking bumps that is exactly what we are doing right?  At least, I think that is what I am doing.  Surf down one to build speed and plane then up the back of the next and then drop down that one and so on for as many and as long as we can.  I think this is the goal especially in short period conditions as each bump is only being surfed for a couple of seconds.  Does this sound right?

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Re: Optimal width of a downwind board
« Reply #24 on: June 08, 2015, 06:28:59 PM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.

I'm not sure.. Yes you can ride a bump and not be planing.. but you can also be fully planing on some bumps IMO..  :)
Well, certainly you can do what I call "surge-riding", which happens quite a lot with raceboards that don't plane easily - you are definitely getting a push but you are sitting high on the bump and going at the same pace as it. But what I think of as downwinding is an experience that is pretty much indistinguishable from surfing: the board is moving far faster than the bump and this allows you to plow over the bump in front and into the next trough, and so on. The board feels loose and free, and is throwing up spray at the sides and you need your foot over the fin to move it around to avoid poking the nose into the bump in front. So I don't know if that is what you'd call planing, but that is what I'm aiming for in my downwinding. You can connect bumps by turning and following the direction of the troughs, or you can do it by getting so much momentum up that you are skipping over them, and that's when the real excitement happens, to my mind.

I think this is a fine explanation of the "point" of downwind SUP.  Contrary to what Area10 wrote, I've heard people say that you never want to go up the backside of the bump in front but when we are linking bumps that is exactly what we are doing right?  At least, I think that is what I am doing.  Surf down one to build speed and plane then up the back of the next and then drop down that one and so on for as many and as long as we can.  I think this is the goal especially in short period conditions as each bump is only being surfed for a couple of seconds.  Does this sound right?
Yes.  Exactly right. 
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Off-Shore

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Re: Optimal width of a downwind board
« Reply #25 on: June 09, 2015, 07:26:55 AM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.

I'm not sure.. Yes you can ride a bump and not be planing.. but you can also be fully planing on some bumps IMO..  :)
Well, certainly you can do what I call "surge-riding", which happens quite a lot with raceboards that don't plane easily - you are definitely getting a push but you are sitting high on the bump and going at the same pace as it. But what I think of as downwinding is an experience that is pretty much indistinguishable from surfing: the board is moving far faster than the bump and this allows you to plow over the bump in front and into the next trough, and so on. The board feels loose and free, and is throwing up spray at the sides and you need your foot over the fin to move it around to avoid poking the nose into the bump in front. So I don't know if that is what you'd call planing, but that is what I'm aiming for in my downwinding. You can connect bumps by turning and following the direction of the troughs, or you can do it by getting so much momentum up that you are skipping over them, and that's when the real excitement happens, to my mind.

I think this is a fine explanation of the "point" of downwind SUP.  Contrary to what Area10 wrote, I've heard people say that you never want to go up the backside of the bump in front but when we are linking bumps that is exactly what we are doing right?  At least, I think that is what I am doing.  Surf down one to build speed and plane then up the back of the next and then drop down that one and so on for as many and as long as we can.  I think this is the goal especially in short period conditions as each bump is only being surfed for a couple of seconds.  Does this sound right?
Yes.  Exactly right.

I've posted this before but here it is again. This is the master Jeremy Riggs on riding and linking bumps. You will see that the waves are not all lined up in rows and are constantly evolving and "spreading". Linking is not just about going up the backside of the wave in front. It is sometimes finding where the waves merge together and riding the bridge that forms between them.

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PonoBill

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Re: Optimal width of a downwind board
« Reply #26 on: June 09, 2015, 07:28:34 PM »
The "Wells Express" on the Viento run in Hood River is a perfect example of linking bumps. I need to figure out a way to get a good video of it.  There's a wide sandbar, at least a mile long with a deep channel on the main river side. With a big wind and big swell going on the swells are peaking and breaking on the bar and not in the channel. If you ride on the edge you get steep waves connected to faster waves with a constant curve. You catch one and just hang on, keeping your board pointed along the edge of the channel. the board links one wave to another in a steady progression, sometimes for the entire length of the bar. If you do it right, you get going faster and faster until you're simply too scared to fall. This is the place where you sometimes get to watch your 17' board flipping and cartwheeling at the end of your leash like a gaffed tarpon.
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Pierre

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Re: Optimal width of a downwind board
« Reply #27 on: June 10, 2015, 01:10:17 PM »
depends on paddler's  size and weight, skill leveland conditions...
for average conditions, using boat stability theory, I computer this couple years ago.. depth of board in water is optional
more or less , the taller you are or the heaviest, wider you need.
if you are a beginner, take wider,
if backwash or cross bumps(current, etc) are likely to be encountered, take wider.
this table is just for reference,shaper rails, wide noses may improve stability, recessed decks too ,... this is for a 12,6 pin nosed average transom,for a 14', reduce 1/2 inch, for a 17,another 1/2 inch...
« Last Edit: June 10, 2015, 01:11:49 PM by Pierre »
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yugi

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Re: Optimal width of a downwind board
« Reply #28 on: June 11, 2015, 01:41:44 AM »
^^^  That is spot on for me. Comes out as 26.2. I’m now on wider (14’ x27) as we have pretty wild backwash and cross bumps on our main big wind direction. I’ve ridden x26 wide and feel ready graduate into that when I find the right board. Might be tricker at first in festive conditions but I feel I’ll gain speed for the rest of the time I’m paddling in non-planing mode (use my board for all conditions + the odd local race).

What was your base theory behind your calculations? Was it smoothing out the curve between different rider sizes and what worked for them or from know weight/planing theories?




Pierre

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Re: Optimal width of a downwind board
« Reply #29 on: June 13, 2015, 01:53:31 PM »
^^^  That is spot on for me. Comes out as 26.2. I’m now on wider (14’ x27) as we have pretty wild backwash and cross bumps on our main big wind direction. I’ve ridden x26 wide and feel ready graduate into that when I find the right board. Might be tricker at first in festive conditions but I feel I’ll gain speed for the rest of the time I’m paddling in non-planing mode (use my board for all conditions + the odd local race).

What was your base theory behind your calculations? Was it smoothing out the curve between different rider sizes and what worked for them or from know weight/planing theories?
Hi Yugi,
Simply computed from boat stability formulae...  your height of center of gravity divided by a factor '"skill factor" or" technical factor" must be placed below the metacentric height of your hull. this is ration of Length*width^3/(12*volume immersed)
that does not include secoundary stability (due to extra volume above water especially on top of rails,on widened noses and tail etc...) and aids to stability due sharp rails or chines,deep skegs and so on... ofr stability losses due ie immersed part of board creating free surface, heightened deck and other stupid things.


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