Surfboards and C2 continuity

How many shapers out there know what that is?

Here’s a link if you are interested…

In my previous life as a water molecule, I found

that running along a C2 surface was much easier.


This is a much better explanation

and relates mostly to rocker and

outline curves.


I may be wrong, but doesn’t the “coe” discussion represent a subset of the “mtu” discussion? (…and hence one might expect would be easier to follow)

You are right, MTB

I’m familiar with C2 continuity from my CAD background.

The “mtu” discussion is a bit heavy so I kept looking

for a better explanation after I saw my post got some

views but no replies. Too brainy for Monday morning I


I thought the “coe” discussion would help.

Thanks for noticing.


Since you’re familiar with C2 from CAD, you might also realize you can have to surfaces that are extremely close but one of them has a discontinuity.

the way shaping and glassing works could very easily render the design effort to satisfy C2 continuity useless.

not to mention that sometimes you need a discontinuity (to release water flow).

I’m and Industrial designer, and I’ve played with C2 surfaces for a long time, I really don’t think it’s worth the effort here.


noboby cares about C2?

that’s a shame,

since water molecules do.


What about ASP3000?

Does it have the ability to maintain C2?


Hein, how about a sixer of Budweiser to take out the night watchman, then you and me pull a “splash” mold off this surface?

the 100 incher at Mt. Wilson Observatory…

Sleep tight.


What about ASP3000?

Does it have the ability to maintain C2?


C2 is not just about surface finish smoothness.

Good C2 means that the change in curvature

is smooth and gradual as you move along a curve.

Here’s an example of two virtually identical

rocker curves for skim board:

Notice how the curvature in the top image undulates

and in the second computer optimized rocker it’s nice

and smooth.

Now if I were a water molecule, I would find it much

easier to flow along the second rocker.


High end computer aided surfacing can make a difference.

Shape3D has this. Check out the demo:


What about ASP3000?

Does it have the ability to maintain C2?


Sorry My post above didn’t work. Trouble with this editor and linux.

The main problem with C2 is that changes aren’t local. With C0 (when

the cont box is not checked) moving the yellow point only affects one

part of the curve, but with G1 (which is what we get by checking the

cont box and is weaker than C1) moving the yellow affects the curves

on both sides of the blue, but only those. But with C2 any change

affects all of the curves which is not really acceptable from a

surfboard design point of view. Using a different type of mathematics,

it is possible to get both local behavior and C2 but it has a

different kind of points: unlike our blue points, these apex points

are not on the curve and of course harder to get used to so we

abandoned that. Designing surfboards with this setup seemed to be

unintuitive for our testers.

Anyway here’s what I meant to post.