Well done Mr Burner , nice to see something different on Sway,s
this build thread ans folloing dicussion is rad, make me pumped to get into the two belly boards i have half shapped in the shed, two edge railed beasts, inspired by greenough.
Thanks for the shout-out. I am happy to see the whole thing come together and glad I could be a part of it.
This thread is just chucked full of Talent and Skill. Charlie brought it to life. Cool collaboration between Bill and Jim. Design and program. Fantastic guys! My hat is off to the genius in this. Much respect gentlemen. Lowel
I have to agree with everything thatās been said about the talent thatās gone into this creation.
But just curious about what itās supposed to do?
The physics suggest the channel will create an area of low (negative) pressure under the tail. The drag should be low. The expected performance advantage would be improved tracking and directional control, without fins.
Charlieā¦I never forget Ewaā¦with Diamond Head in the distance on 2nd photo behind the gate!! Had many go outs there in the hoodā¦with not another surfer in sight. Fond memories.
Amen brother. The mile out reef at the 6 foot depth is surfer magazine centerfold perfection. When my wife paddles out it doubles the crowd.
Pray all is well.
warmest aloha
Charlie
Light soft eps, āthickā wood skins, no stringer, no rocker table on photo, how do you keep rocker under pressure ?
Charlie is the builder. So he will need to confirm my response.
I do not believe a rocker table was used. We went minimalist. I donāt believe there is any deck rocker (deck is flat).
Tail rocker is indirect in the form of the channel bottom. Nose rocker (kick) was cut/shaped into the front third of the blank.
Iām curious, why did you insert the channel instead of simply shaping the channel into the original foam blank?
The channel design has some very specific curves and dimensions. It would be very time consuming and difficult to precisely shape it by hand.
Jim computer shaped my design ā to hundredths of an inch ā as a panel that can be grafted into a blank of any shape. Jim called it a cartridge, now referred to as a āchannel cartridge.ā
The smaller size of the channel cartridge facilitates more cost effective shipping from MN to HI, KY or anywhere else. This allows us to send it to test pilot/shapers.
Wow! Very cool board. Glad you found somebody with the talent to do your project, Bill. It came out incredible. Mike
The more I see, the more I like.
Now, given a set of fixed dimensions for the cartridge, wondering if youāve got an ideal planing area mapped out to work with it? Or is that part of the testing? Thinking about experimental design: if the cartridge was made up as, say, a waterproof subassembly ( completely surfaced, glassed, etc) that could be swapped in and out of several different boards with varying characteristics you could get some great data. Iām sure you can picture what Iām thinking about.
Thanks, looking forward to how this works and develops.
docā¦
Doc,
You are at the trailhead now. But the number of divergent trail choices at the outset is enormous.
Early on, I considered interchangeable channels. But I couldnāt even find somebody to computer shape a foam channel. I had done a couple of projects with Jim before. So when traditional surfboard shaping software/machines were a bust, I went to my garage CNC/CAM magician, Jim. Bottom line, it was clear that the complexity of Interchangeable channels meant real world protypes were well beyond reach in the immediate future.
The number of variable combinations is immense. I used the SWAG method to determine the initial channel dimensions. The first channel was designed for a 42" BB. Then using the SWAG method, I designed a channel for a 48" BB. I sent Charlie both. He chose to build the 48" BB first.
Iām still not convinced the current dimensions are optimum. All of my curves are defined by equations. I can adjust them for any combination of dimensions desired. One-offs are doable if Jim has time outside his day job.
At the moment, my belief is the planing area around the channel is most critical ā referred to as the tail āpontoons.ā But I do not know what the āoptimumā channel dimensions are. I suspect there is a desirable low/negative pressure ā too high or low diminishes performance. This will be affected by velocity.
I tried to recruit several Sways shaper test pilots. By dumb luck and pure good fortune Charlie was the first Sways adept to shape a board.
We still have no test pilots. As offered previously, if Jim has the time, I am happy to work with him to make and ship you some graftable foam āchannel cartridges.ā
The channel is intended for use in several types of surfcraft. However, the original objective was to improve BB tracking without fins. Iām liking the idea of a āFinless Fishā somewhere in the near future. But I think it could be used effectively in combination with a twin-fin set up (quads?).
Bill
BTW for those not familiar with the jargon, SWAG = Scientific Wild Ass Guess.
Hi Bill,
Right? Thereās a few ways to make a swappable cartridge, I think, fairly straightforward, but for the moment ā¦ and itās real nice to see a SWAG in this field, the vast majority of āsurf scienceā is what a friend of mine described as āhand waving and hopeā. I come from a marine engineering/naval architecture background-we like numbers.
Measuring things is the key, and difficult- waves are inconsistent, speed through the water is easy enough in a tank test but speed, say, versus angle of attack on a 3D curved moving surface? Owning, say, your very own wave pool or some river you could play with to make a standing wave?
In any event, yeah, I suspect the ratio of area of the pontoons ( or, if you like, steal the term āsponsonsā from the planing surfaces on racing hydroplane boats) to the channel volume, say, is important. Or, perhaps, the bottom surface actually in contact with the water at a given speed? The volume could be measured, mask it off and pour in water maybe, but given the consistent shape of the channel Iāll bet the area of the back end of it would be good enough. The width versus the height too, that ratio, but thatās a whole other thing. As you say, the sheaf of options is enormous. Spreads out like a peacockās tail ( or, considering the date, a turkeyās)
Which has me thinking about maybe model testing? To narrow that spread? If a fairly fast-flowing stream (or for that matter any reasonably deep flowing system) was available? Foam, or for that matter painted wood, models scaled down accurately, measure drag, measure resistance to sideways force, measure force exerted when the angle it pointed was changed? While test pilots/actual use would give you a very general idea of desirable characteristics, this model testing might be a real good way to fine those down quickly and inexpensively/easily?
Fascinating stuff
docā¦
Doc,
Donāt have time for an expanded response at the moment. Maybe later when I have more time to mull over my words. Gotta get in a fill coat before dinner ā my weather window is closing quickly.
Between the two of us, we have barely identified the tip of an iceberg. I see at least two graduate thesis projects in what we have discussed so far.
I have a broad-base undergraduate science background. I am a retired scientist, graduate education ranged from medical science to aquatic science. My professional research would fall under the broad topic of aquatic science.
My rabbit hole for this channel project, curves in two dimensions and depthā¦
Bill
(chuckling) Ya think? The real trick is in writing the grant applications to fund all of this R&D plus a few beers.
Times like this I especially miss Terry Hendricks. He had, among many other things,. a real gift for devising nice and inexpensive ways to test things.
Modelling hulls and hydrodynamics, numerically, well, they used Crays to do Americaās Cup boats in flat water a decade or two ago. Million dollar plus project. Computing power and the cost of it have changed a lot since then but modelling a surfcraft on a moving wave I would estimate to be orders of magnitude more number crunching, would have to get a good basis/basic data to work from to begin with. Maybe the Navy has something like that for hull design, I do know I couldnāt even attempt to write the software on the best day I ever had.
Glad you reminded me, theyāre giving rain for tonight and I have to get a tarp over something I wonāt get to installing or moving in the dark. Back to earth, as it were.
docā¦
Nodding in agreement with a slight chortleā¦ no sh!t.
A fine spray of coffee descends, followed by a loud guffaw
Exactly.