Basic calculation for volume

General Discussion
41

Just a few random thoughts on a saturday morning cuz I got sidelined from yardwork by a wasp sting, and I’m waiting for the swelling and pain to go down.

First of all, the original poster never responded to the question of why he “needed” this information (volume) on a finished board. He has had several posts deleted for being wildly off topic, and I suspect his interest in surfboard design and building doesn’t extend much past the desire to pimp his surf prediction app.  I haven’t seen any evidence that he designs or builds surfboards, or has any real interest in the process.  Maybe he’ll prove me wrong.  Regardless, as long as he is starting threads that get honest converstions going, he is welcome here just like everyone else.

Yes volume can be a useful metric or datum, but within a certain context.  It also can be a waste of time and even a bit of a red herring, in that it can send people down the wrong road in the search for a functional shape they could enjoy surfing.  People put so much faith in the importance of volume that they fail to look at shapes outside their volume “ideal” as promoted by bla bla bla.

Now the CNC machine is brought into the conversation.  Like Reverb said, the arguments go nowhere, I have never seen anyone change their mind from an internet argument or debate.  Its like nuclear energy or plastic production, it can be good and useful within a certain context, or abused to the point that it causes actual damage, and so some would prefer it not even exist.  But hating its existence will not change the present reality in which it exists.  People who view it or use it for good will not see the issue the same as those who look at a different facet of its existence.  The two sides will never agree. 

Reverb doesn’t have to make an impassioned argument in debate of Tomas’ points, he already has, its in the archives.  But none of that is really here nor there, it largely falls on deaf ears, but some like me did enjoy his knowledge and perception shared on the subject. I also tend to agree with him that the CNC machine (combined with exploitation of cheap overseas labor from economically depressed countries with no child labor or environmental protections) has done WAY more damage to the local shaping industry than any backyarder fixing a ding for his friend for free.

I don’t think anyone is against the measurement of board volume per se, just the abuse or misrepresentation of what that number is actually useful for.

And off topic from everything, sorry to hear Tomas of your pop up issues, at 64 years old I know and can feel that I am probably going to have the same issues before too long.  And I have seen your boards on Ventura Craigslist, they look good! Nice to see you posting here, its been awhile, and you’ve been missed.

42

Thomas,

Very nice design work.  Most impressive.

I started designing bodyboards 3 years ago.  I built a couple of prototypes by hand.  I came up with some secret sauce early last year and quickly realized hand-shaping would be too slow for rapid proto-typing and testing.  There is a “minimum” of 54 potential combinations of shape elements.

My secret sauce has some very precise contours that would make hand shaping way too slow.  The CNC shaping problems are somewhat similar to machine shaping a fish tail.  I contacted a west coast pro shaper about prototyping.  He said he didn’t have enough time and there were no shaping machines in his area that could do the job.  He did indicate that Marko might have the needed equipment.

Nonetheless, buoyancy (volume) is a critical factor for bodyboards.  I’m curious.  What does your formula say about bodyboard length, width, thickness and volume for a rider that is 5’10” at 170-180 lb.

Bill

43

Probably best to start a new thread on prone board design.

Moderator - can this post be moved?

44

Nomasto . . .,

Yes of course - The posts I thought were useful to me and my goals for starting to use somewhat shortboards again got likes

45

The more information the better!! IMO. As already mentioned, volume #s can help you figure out the foil - particularly a board  you don’t have in-hand to feel up. 

 board manufacturers should give thickness, & width at  1 foot out from the tail as well as the nose. (rocker too - but that isn’t going to happen). 

 

Lil off topic but relevant: I spent a bunch of  hours with a pro shaper  over the last week going over design theory, function and practical application of such. He’s been shaping for 50 plus or minus years… and … gasp… we did 99 percent of it on a computer.

 

I learned a ton and very thankful for the opportunity- If all that time had been spent in a shaping bay I wouldn’t have learned and retained even a 1/3 of what we went over, and here’s an example why: Using AkuShaper he would make “mistake” on purpose - in the outline, rocker etc that I could very easily see - then compare directly the same shape with them corrected, and go over the Whats and the Whys etc. 

also took a board I did in Aku and have been riding for  a few months and went over that file. There were some things he saw that corresponded to some of the aspects of the board that were not working. Example: nose rocker had a tighter radius/more curve toward the middle of the board then flattened as it moved to the tip of the nose. Not drastic, but enough to make an impact. Paddles good but pushes water on take off - particularly on waves with a good bit of power. He then corrected it and we compared the 2 directly/overlay/ghost board. Waaaay easier to see all of that and get your head wrapped around it on a computer- rather than looking at & manually measuring physical boards… and including common but hypothetical mistakes/bad design that we could go over. 

 

All that being said, if my neck and shoulders weren’t messed up I’d probably be using my planer and hand shape more boards. At the very least I think Aku etc are great creative and learning tools. 

 

I don’t personally give a toss about the surf industry but I’ll just had this: Be creative, adapt and take a crack at success or continue to do the same old thing, drivie yourself crazy and out of business. 

 

 

46

If I may chime in at this late stage: 

Buoyancy is volume. That is, the immersed volume gives a buoyancy equal to 64 pounds per cubic foot or 1.066666666666667 kg/liter in standard seawater. If you’re surfing Lake Michigan or the Red Sea, your mileage will vary. . 

Note that I said immersed. The part of said board, or boat, or whatever that is actually under water. Calculating that, for a ship designer, was an absolute beeyotch for Naval Architects/Marine Engineers back before they had software for it. It was done graphically using a perimeter measuring tool called a planimeter and some cute numerical quasi-integration methods like Simpson’s Rule. We won’t even get into righting moments for a given angle and displacement. Put it this way, they test that by putting weights on the deck of a vessel and seeing what it does. 

History, making the numbers dance. Used to be what I did. 

In any event- is the craft completely submerged?  Then it’s volume gives you the floatation…except if you’re sitting on it, at rest, your legs are in there too, making their own floatation figuring the immersed volume of legs and then there is the specific gravity of the human leg…see where this is going? Complicated. 

 Now, what does volume do, besides float you at rest? I mean, in use the board isn’t completely submerged. Just the opposite, it’s a planing hull, generating lift from other hydrodynamic forces. The more volume at, say, the rail, maybe it makes a difference to how it tracks, how much of the bottom is generating lift, what the drag is, for a given speed and a given weight, among a bunch of other things. I wouldn’t want to try to write the modelling software. 

The nice thing about being a kneelo guy, or a paipo guy, is all we really worry about is if the board itself floats. Beyong that, it’s just gravy. 

 

doc…

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I’m not going to name names, to save other people headaches, but here in Santa Cruz there are a couple of guys who can shape by hand but have definitely mostly “shaped” via software and PC, with high-visibility labels and plenty of happy local & international customers (including pro riders who surf better than any of us ever have, or ever will).

The biggest labels in town – renowned handshapers long before CNC cutting was even around – are all producing via scrubbed CNC cuts.

The other day, when the glasser (long time glasser in SC) came to pick-up blanks, he (not gossipping, just in passing, a fact dropped) mentioned that one of the better known “soul shapers” around is having his boards cut on CNC before he handfinishes. The shaper makes no claims that I’ve ever heard or seen that he doesn’t use a machine, but I doubt ANY of his customers would ever guess their boards are first cut on machines, and would be pretty shocked to find that out.

I remember seeing a post somewhere (website or social media) by another well-known shaper (internationally well-known), big market name, steadfastly disclaiming machine shaping and hyping his boards as never cut by machine, 100% handshaped, and in the photo of his blanks rack you can see a bunch of freshly CNC’ed blanks of his boards lol.

And on the other hand you have shapers like Ryan Lovelace who (recently saw a comment online somewhere, maybe in a printed interview, or transcripted interview), that he can feel the difference between a CNC’ed version of one of his boards (presumably finished by him) and a handshape, and that he prefers the handshaped results. I believe him, personally.

I have never gotten the results I hoped to get with CNC cut blanks (always Marko EPS, in my case), though I regularly handshape using the numbers from designs first created in Shape3D, using the printout and traditional templates & blending to handshape from raw PU, despite that the finished dims are usually easier to keep closer to the original targets, and despite that the EPS/CNC’ed boards are usually less off, side vs side, than handshaping from a stock or custom blank. I chalk it up to maybe something in the way rocker is executed on the specific CNC machine(s) not being quite as digitally prescribed, and/or my just not being a fan of how EPS feels using the construction I used for them (maybe I would like some type of compsand better, I have no idea).

IMO the biggest advantage handshaping has over CNC is that it’s difficult with Shape3d to incorporate vee into the design. Handshaping, that happens sort of organically, via cutting the rocker in first, then introducing the rail rocker changes off of the established stringer line. With software, that is much more difficult and painstaking to do, and if you’re going to do production you want your file/design to be very close, especially if a ghost-shaper is going to be involved. IMO that is one reason you rarely see vee in CNC’ed production boards; i.e. it is somewhat difficult & paintaking to “program” vee into the design. It is much more common to see a CNC’ed board whose design you’d think, just looking at it, would usually have a little “spiral vee” if it were handshaped but that instead has a flat line across the double barrel in the tail (where you would expect a bit of vee).

48

Thanks for the well thought out response Batfische.

I know a couple pro shapers that do machine cuts only and they always do vee by hand. 

how well the machine is dialed in/operator are a big part of it too. If their results are inconsistent and unpredictable then what’s the point. If it’s consistent and there are limitations then you can design files with that built in to get the results you want-sometimes w a bit of hand shaping or tuning. I’ve heard plenty of stories of sloppy/shitty cutting services. 

There’s also guys that can’t physically hand shape- so they have cuts done, some in varying stages of completeness and finish by hand.