Author Topic: The fun of unlimited boards (Read 48176 times)

PonoBill · « **Reply #105 on:** May 22, 2016, 07:56:20 AM »

Quote from: hefwiezen16 on May 22, 2016, 04:32:40 AM

And as for round hulls being slower on SUPs; that depends on who's paddling it.

Absolutely. Most people can't manage the constant roll and catch that minimal initial stability delivers.

I understand that languages of science and medicine read and sound the way they do because the need to be precise (and it's always pleasant to exclude the unwashed). I've never heard the term 'clapotis', but that isn't surprising since I have no background in boatbuilding or paddling. Any expertise I have is very narrow, generated by becoming interested in something and studying it intently. The usual limitation of the amatuer. No scope.

I struggle to find words to describe the phenomena I see or infer, but I don't think I'l be adopting clapotis anytime soon. It sounds like something you might develop if you frequently contracted gonorrhea.And clapotis looks to be fairly specific, meaning a standing wave generated by reflection, and not the general backwash or reflected wave energy from a steep beach or a wall. I'm sure the meaning has been generalized, but that makes it potentially confusing to someone who actually knows what clapotis is--which only includes me in the last few minutes.

UKRiverSurfers · « **Reply #106 on:** May 22, 2016, 08:37:39 AM »

Well - in the sea kayaking guides I refer to in my multi day SUP trips, they use the term Clapotis to describe certain areas of coast that are effected badly.

The Jurasic Coast is know for it between K Bay and Lulworth Cove, a result of steep cliffs plunging directly into the sea. It can make even the hardiest folk sea sick

http://www.b3c.org.uk/trips/Lulworth%20Trip%20Report.pdf

Area 10 · « **Reply #107 on:** May 22, 2016, 10:30:47 AM »

Yep. Well I guess this nicely illustrates the varied uses of terminology. As long as we all know what we mean (which is usually discoverable through the context) then I guess it's all good. It seems that on the zone most people just say "confused seas" or "messy waters" or similar - which doesn't tell you anything about the source of the phenomenon but describes the effect upon the paddler quite well, and can be understood by anyone.

And yes, the S Coast of the UK has a lot of different phenomena. The tidal gate round Selsey Bill leads to some really strange things happening at locations nearby, such as the current nearly always going W even when the tide is going out (i.e. heading E). Just weird. But it makes the swell really stand up for downwinding and your speeds at the water surface seem much faster than the GPS is telling you. So you get a longer run for a given transport shuffle than you would otherwise. So these strange phenomena can have their upsides sometimes

Pierre · « **Reply #108 on:** May 22, 2016, 11:50:06 AM »

Quote from: TallDude on May 20, 2016, 11:07:00 AM

Paddlespot,
That's a sexy looking board. I've been down this unlimited design road before. Two things to consider is the windage at the nose, and the full round bottom is actually slower on a sup. The rounded board causes a lot of foot over-steering. The foil created as it heals over (which it will constantly) causes the board turn hard right or left. You basically spend your energy trying to keep the board from constantly zig zagging. Craig Richmond told me that over the years of the unlimited development they found a full length double concave, a slight bevel at the rail then straight up rail is the fastest design he's done to date. Thomas Maximus unlimited has that bottom. Brian Szymanski's Lahui Kai race boards have the same bottoms. Mine is flat with a slight round at the rail the whole length. My next UL will have a double concave full length.
You can take some height (or depth) out of the first 2 of the nose. That's more for a 14' or shorter board. Maintain recovery volume starting about 3' feet back. This will help in quartered wind.

Food for thought.

Theory of less speed on a rounded shape may certainly not be verified in flat water. Oversteering can be solved in other ways than a double concave... Even a rounded shape is for sure not designed for heavy downwind condition, why surfskis have such?
And whatever findings of Craig Richmond, Travis Grant board has a different design and works awesome... My opinion is that a rounded bottom may work best in condition which are best fit for it, but theoretically it should work the best. Oversteering is not an excuse.

Pierre · « **Reply #109 on:** May 22, 2016, 12:11:08 PM »

Quote from: UKRiverSurfers on May 22, 2016, 01:04:21 AM

Please use 'Clapotis' not refraction as the correct term

"Clapotis" is originally a french word which means irregular choppy water, generally noisy of low amplitude. can be current against/across wind or wavelet REFLEXION. the meaning of word can be altered.

Pierre · « **Reply #110 on:** May 22, 2016, 12:16:42 PM »

my last search is the double chine...

Pierre · « **Reply #111 on:** May 22, 2016, 12:19:39 PM »

Quote from: Area 10 on May 22, 2016, 05:17:44 AM

Yes. Round hulls are of course faster, theoretically, but you need to add width to compensate for the added roll otherwise the paddler can't cope with it. This added width tends to negate the theoretical speed advantage, and make the boards hard to paddle in chop, and also affects things like beach starts, surfability and ease of certain forms of drafting. So although round hulls are theoretically faster, for most paddlers and most situations, the disadvantages outweigh the advantages, and often make them slower for the applications that people actually use them for. But if we all paddled on rowing lakes in separate lanes then all our boards would look like Olympic canoes or rowing craft. People demand versatility and ease of use from their SUPs.

To complete my previous post, Area 10 your reply is wise... But using a round hull with the knowledge of the "Pros" and"Con" about it can be pleasant. Especially when paddling them in situations they fit for. And there are, including in slight downinding condition without too much "clapotis".

Area 10 · « **Reply #112 on:** May 22, 2016, 01:29:42 PM »

I think we agree. There have been successful SUPs with rounded(ish) hulls like the K15 and some of the NSP DC boards. And even one of my own 12-6s has a (fairly mildly) rounded hull (C4 Switchblade). You are right that you can learn to use and admire the handling characteristics - to a certain extent, and they can be fast, for sure. But as I say, to list people they feel a bit tippy for their width and a lot of people are obsessed with going as narrow as they can, so trying to sell boards that roll a bit is not always going to be easy. What sells is not necessarily what is the most effective.

PaddleSpot · « **Reply #113 on:** May 22, 2016, 01:41:18 PM »

Quote from: PonoBill on May 20, 2016, 08:09:09 PM

That's a lovely design if you're going to put a motor or sail on it. or maybe paddle it in flatwater. But downwind boards get pushed from behind. If you're going to try to start from first principles (like "a rudder needs a pivot"--since when???)

Basically, since around 250 BC :-)

“Give me a place to stand and with a lever I will move the whole world”
Archimedes

Quote from: PonoBill on May 20, 2016, 08:09:09 PM

If you're going to try to start from first principles then you have to get them right.

I promise you I'm trying my best, with my old engineer's degree, specialized in mechanics and naval architecture :-)

I know that "downwind boards get pushed from behind", so what

?

To make anything rotate, you need an axis and a torque. The rudder provides the torque, but without axis it can't work properly, just like anyone confirms here. Add a small centerboard and the rudder will make the board turn around it.

Quote from: PonoBill on May 20, 2016, 08:09:09 PM

The rudder rarely turns the tail around the nose of the board, it pushes the tail to one side or the other. The board may sideslip as a result

Precisely, because SUP flat hulls lack the pivot of the centerboard or the support of a deep hull

Surfskis work well because they have a deep, v-shaped hull, so they don't sideslip. Just like old Hobie cats can sail upwind without centerboard.

But everyone knows that SUPs have a problem cross wind, that OC1s, K1's, or any of a myriad craft with decades or hundreds of years of development don't have because they have deep and narrow hulls. SUPs are shaped like big surfboards;that's why they just don't work cross wind. Every flat boat in the world need a centerboard cross wind, except windsurfs cause they use their rails instead. SUPs seem to leave in a world where the escape the laws of physics.

This topic is called "The fun of unlimited boards", it's not dedicated to DW, neither is my future UL. The aim is more to be able to easily paddle 60 miles in a day. But I'm pretty sure it will be perfect in DW conditions. Please have a quick look at how my current "Pierre de la Monneraye design/home made" round 14' goes downwind. Just like a surfski. Not as fast, but as smooth... It was my first test, I have many things to improve, but this round hull is a real downwinder

http://www.supjournal.com/article,breve,video-un-downwind-sur-l-etang-de-berre,4034

Chilly · « **Reply #114 on:** May 22, 2016, 04:06:33 PM »

If you’re in side chop and need to correct your course and turn into the wind, wouldn’t that center board fight you? Compared to a rudder that can easily turn the board with the paddle stroke. The paddle being the pivot point.

PonoBill · « **Reply #115 on:** May 22, 2016, 05:38:19 PM »

Quote from: PaddleSpot on May 22, 2016, 01:41:18 PM

This topic is called "The fun of unlimited boards", it's not dedicated to DW, neither is my future UL.

Somehow I missed that this board is intended for flatwater--sloppy reading on my part. As Rosanne Rosannadana would say: "Never Mind."

But any hull has a center of drag: flat, round or v, and it can and will be turned by a rudder around the center of drag. the question is how much drag is there, where the center is located, and is it enough to provide effective turning for the condtions we subject the hull to. I realize this is the pivot you are speaking of, but to my reading you were inferring the pivot doesn't exist without a centerboard, which is obviously not true.

I raised the issue of centerboards in downwind rudder boards because I've tried them and didn't like the result. When the board is turned across the wave the centerboard drag overcomes the rudder and the board rounds up. Furthermore, sideslipping is an important part of positioning the board the way you want to.

I do have a ventral fin on my 18' Speedboard, which is a flatwater board, and I like it for certain conditions. The board has a fixed fin, and again, in any condition where there is wind and swell coming from behind, the board becomes more difficult to handle. In races like The Challenge On the Charles" the ventral fin was more trouble than it was worth, since the wind often came up during the race.Nice for upwind, okay for crosswind, lousy for bouy turns. The speedboard nose is an elongated deep, rounded V, much like a surfski. It doesn't need the fin, but it helps a bit.

UKRiverSurfers · « **Reply #116 on:** May 23, 2016, 01:20:01 AM »

Quote from: Area 10 on May 22, 2016, 10:30:47 AM

Yep. Well I guess this nicely illustrates the varied uses of terminology. As long as we all know what we mean (which is usually discoverable through the context) then I guess it's all good. It seems that on the zone most people just say "confused seas" or "messy waters" or similar - which doesn't tell you anything about the source of the phenomenon but describes the effect upon the paddler quite well, and can be understood by anyone.

And yes, the S Coast of the UK has a lot of different phenomena. The tidal gate round Selsey Bill leads to some really strange things happening at locations nearby, such as the current nearly always going W even when the tide is going out (i.e. heading E). Just weird. But it makes the swell really stand up for downwinding and your speeds at the water surface seem much faster than the GPS is telling you. So you get a longer run for a given transport shuffle than you would otherwise. So these strange phenomena can have their upsides sometimes

Yeah but a lot of that strangeness around Selsey and other prominent headlands/points on the south coast is all in the admiralty charts, tide diamonds and tidal streams atlas's..

The worst place is Portland Bill over falls.

As most SUPers don't venture too far along isolated coasts they won't see all the different phenomena... As I said before - every part of the south coast is like a Child's play ground compared to the North Coast.

And the North Coast is my next desired trip! I'll be first, on one of my UL SUPs! Nobody else wants part of it!

UKRiverSurfers · « **Reply #117 on:** May 23, 2016, 01:24:27 AM »

Quote from: Chilly on May 22, 2016, 04:06:33 PM

If you’re in side chop and need to correct your course and turn into the wind, wouldn’t that center board fight you? Compared to a rudder that can easily turn the board with the paddle stroke. The paddle being the pivot point.

The centreboard would actually aid directional stability - therefore making your strokes more effective and better distance per stroke. The centreboard will take the sideways energy and turn it into forward momentum, similar to a sail on a dinghy

SUPflorida · « **Reply #118 on:** May 23, 2016, 06:42:39 AM »

If the small "ventrical" fin is helpful in some conditions and a liability in others.. a minimal size retractable dagger or centerboard could be the answer. But much smaller than that show in paddlespots computer rendering (where the daggerboard appears to have twice the area of the fin).

Apply what Larry has already experimented with in regard to depth and area...this could be the next step in the natural progression of things. If properly designed so as to easily deploy and retract, it would lessen the issue with weeds as well.

PonoBill · « **Reply #119 on:** May 23, 2016, 07:35:52 AM »

Mark Raaphorst at SIC designed and built one some time ago--very elegant. At that time both of us happened to be working on forward rudder steering (steering with a rudder where the ventral fin would be). In my case the rear fin was fixed, in Mark's case the rear fin was also a rudder and the movement was linked. Both turned out to be uncontrollable in most rough water conditions and provided no steering benefit.

The swithchblade ventral fin was part of that development. It was controlled from the deck with a paddle blade or toe. I'm not sure why mark set it aside, but I decided my results were not worth the effort of developing. I liked some aspects of front steering, but found that it was ineffective for the kind of paddling I care about. I also don't bother much with ventral fins. In pure flatwater in a straight line they would make some paddlers faster, but in a typical flatwater race in a course with bouy turns they don't so much. There's an old picture of me somewhere on Facebook during one of the Willamette SUP cup races where I look like I'm giving birth trying to get around a bouy, and getting aced by a guy on the inside. Ventral fin in the Speedboard. The chop and bouncy water from boat traffic made a tail pivot very dicy--at least for my balance.

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Author Topic: The fun of unlimited boards (Read 48176 times)

PonoBill

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UKRiverSurfers

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Area 10

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Pierre

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Pierre

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Pierre

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Pierre

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PaddleSpot

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Chilly

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PonoBill

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UKRiverSurfers

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SUPflorida

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PonoBill

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