They are replys to what is said before and they did lead completly away from the original subject.
Read from the beginning and its easy to follow but jump in part way and it doesn’t seem to fit.
ya dont like it dont read it
go to another thread cary on greg interesting stuff
huie
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in actual fact vee was taken out between the fins and put under the front foot the affect was to straighten the centre rocker and put the curve on the rail line ! the old theory was that by having a big vee between the fins made the bd looser,it did the opposite-I use 1"concaves now which still uses the same principle --curve on rails ,low curve centre stringer for speed,so in a straight line bd generates speed and when you go to turn ,you tip the bd over onto the curve in the rail.
For this to work, doesn’t the concave depth need to be set relative to the rocker curvature ie: deepest through the tail kick, and flat at the nose and tail?
Also, although I haven’t seen boards like this, I am sure the answer is known…what if the concaves are only cut over 1 foot at the rear rocker transition, and 1 foot at the front (and flat between the feet, and nose/tail). The net effect is flattening the stringer-line rocker from nose to tail. Or do you have to include concave from front rocker transition to rear to achieve the effect?
wouldn’t it be similar to what’s typically called a “staged” or three panel rocker.
I think Mctavish coins the term to describe his longboard bottom like his fireball design where there’s distinct seams in the bottom curve. one curve on the nose, flat mid section and another curve in the tail.
It was the complete challenge to the continous curve school which was more aesthetically pleasing but perhaps not as functional?
Chandler has something for longboards he calls a four panel bottom which changes into four distinct patterns but I think it’s more bottom contour than rocker.
My hacker understanding of bottoms contours is that aside from release it’s primary motivation it to alter the botttom rocker in relation to the rail rocker what ever that means regarding performance. Kind of like the two Shane’s banana boards with the super concaves that sparked Webber’s rise to media fame like the reverse vee did for Maurice. I kind of like Greg’s foil dissertation on the whole subject as there’s seems to be only a few that look at the concept that way instead of in pieces…
In the end once the paddle problem can be resolved like in towing the only that matter as far as bottom/rocker design is what’s going on with the foam directly under your feet than what’s happening 2 feet in front or behind of them.
Quote:
wouldn't it be similar to what's typically called a "staged" or three panel rocker.I think Mctavish coins the term to describe his longboard bottom like his fireball design where there’s distinct seams in the bottom curve. one curve on the nose, flat mid section and another curve in the tail.
It was the complete challenge to the continous curve school which was more aesthetically pleasing but perhaps not as functional?
…
I plugged the rocker numbers for every board in Essential Surfing (early 80s boards) into math programs, and calculated rocker curvature as a function of position on the board. There were no continuous curves. Every board had a prominent transition point for the rear rocker ie: roughly 18 inches up from the tail (close to where a rear foot might fall while riding), the curve breaks. The curvature near the tail is not so different from the curvature between the feet, but the angle is. The point of maximal curvature on the rear half was at the transition point.
The point I was making about concaves is that assuming you have a rear rocker with such a transition, and your goal in making the concave is to decrease the stringer rocker relative to the rail rocker, you need to cut the concave deepest at the rocker transition. And use no concave at the very tail. If you wanted increasingly flat stringer rockers, you would need to keep the concave zero at the ends, and make the rocker deeper in the middle (opposite the main curve), while continuing to take a little more concave at the transitions.
Of course concaves are also used off the tail in many designs, but a concave that deepens into the end of the tail will increase the stringer rocker, not decrease it.
Blakestah,
Good post. The original concave in shortboards done by Brewer in the early 70’s was deepest at the tail. Later we did them, still in single fins, which were blended concaves which were done kind of like but opposite to the blended vee with the apex just in front of the fin blending to flat off the tail. As you noted, this removed the tail break from the center line and added drive and speed over the flatter reverse vee, which it replaced. We actually stated doing these in the late 70’s long before the reverse vee even showed up. The breakthrough in three fin concaves actually came when Bill Hartley made one of his single fins into a three. This happened in the mid 80’s but we couldn’t sell them until we went through the reverse vee stage and then Greg Webber got a look at one of Bills boards at Angourie and he was able to popularize the whole thing.
What happened to Bill?
This is defiantly one of the best threads on Swaylocks! Thanks for the info!
Taking concave in the tail to an extreme: Hard to see in these pics, but the concave increases out the back, loading up the flex panels. I got a lot of cool feedback from these models.
Still surfin. Spends a lot of time now in Indo.
The “H” was…and still is THE MAN!