Here is what I mean
(Note: disregard the poorly foil, its for illustration only)
The normar tail rocker line would be the lower border of the yellow area.
However would introducing a different (concave/inverted) curve into the existing tail rocker add drive? (Top border of yellow area)
I understand that the channeled boards might have something similar going on, but I think the channels are straight (no curve).
Any thoughts?
Great feedback, thanks fellas!
Everysurfer (Mark): did you expect the board to behave that way? Or did you shape it that way for the hell of it?
Wildy: Would you be able to expain why this feature works this way? Im no engeneer, the way I see it is that the water gets re-directed by the transition. Re-direction of water means change in velocity (Note: NOT SPEED). Since there is change in velocity there has to be a force exerted. I thought this feature might add drive, but as always these things seem to be counter-intuitive.
John: Many thanks, I remember seeing those boards on one of the finless threads. Looks alltime.
and
Cuttlefish: I must ask…how does it feel?
I wanted to try this feature out on a singlefin.
So far its dimentions are: 6’3" x 19 1/2" x 2 5/8"
Tail 13 7/8"; rocker 2"
Nose 12"; rocker 4"
There is still plenty of foam left in the tail, so there is room for this feature.
What say you? Yay or nay?
johnmellor,
Is the inverse curve only on the rail rocker or along the stringer as well? how far up do you put yours?
thanks
… I imagine you flatter out the “rail” rocker behind or at the side fins until the back fin “if it were a thruster set up” (this might be what the name “semi-inverse” actually implies ?.. )
As I stated before. I found the opposite in the way I shape the interpreted design, I put a strong direction change, Like being on a “Bali Ball” you know those training things for balance.
However when I make em I do a complete direction change. eg equal flat before and after the initial rocker direction change “rocker bend”.
I’m guessing for it to skitz out and get loose and crazy and super fast one would scoop out the rocker “of a per shaped smooth curve” under the back foot hence having the last bit of tail flip almost “being opposite of flip” and heading back down (so to speak!).
I’m not saying any one is wrong now. (I’m trying to watch my words so I don’t open myself for Bitch Slipping or Grilling or offend any one!)
Any way, we share - we learn.
…Feel free to debate
Yorky
I did it, but further forward.
Back where you show it, it would cause a vacuum sort of effect, slowing you down. If you put it in front of the fins, it gives huge lift. Think of an airplane coming in for a landing with its flaps down.
Makes a super loose and fast board, that can’t be ridden over waist high surf. Once the waves get to chest high, or over, it gets out of control. Not so much slidey like a finless board, but squirty like a watermellon seed between your finger tips. Mine is a thick double wing quad. Great for slow summertime surf.
seems like alot of drag
I've used that design feature a lot, combined with other bottom contours. I used it pretty much like your sketch, maybe a little smaller and towards the tail.
I applied this to my bottom design after some pretty extensive work with an engineer.
Designed and shaped correctly it's like taking the brakes off. Allowed my 6'5" to glide like my old 7'0". I used it on thrusters, but mainly on in-line fin design set-up.
Good thing was you could use it as a brake leaning on the back foot, but then you could plant it on the front foot and just take off again without that tail lift drag.
I've used it - on bellyboards and surfboards with good results. The old school 'spiral vee' was a similar concept. I.E. dual concaves with a reversed curve at the end.
It always felt like I got a little extra lift on take offs and more speed down the line. The negatives might include decreased maneuverability but that's often the tradeoff with down-the-line speed concepts. On a really sucky wave with a lot of water moving up the face, it might not be the rocker curve of choice.
It's esentially the opposite of an accelerated tail rocker which also has it's place on board designs.
For a wild example of the reversed tail rocker concept, check Dale Solomonson's TriPlane bellyboard... http://www.quivermag.com/node/664
I had this happen due to lap-cave on the bottom tail area…poorly sanded and finished.
felt like it hung up off the top.
this feedback was provided from 2 other riders who experienced the board independently.
Up to you… I would just give the board a bit more tail rocker and do a single concave and let it run out the fin and flatten it out a bit out the back? You will get a nat inversion that way.
yep, works great… allows for a nice flowing rail thickness into the hard edge too. I’m into em!
Yeah like every surfer “a bit further forward”
Hi cuttlefish -
IMO that is a good example of the spiral vee concept. I've seen deeper dual concaves but I'm not arguing with that one bit. That photo should be in the Swaylopedia.
astevens -
"Is the inverse curve only on the rail rocker or along the stringer as well? how far up do you put yours?"
That depends on the board. On a bellyboard I did awhile back the bottom was concave both rail to rail and along the stringer. That was coupled with a hoop fin so the whole tail was kind of a water chute.
I've also shaped dual concaves - some very similar to the DVS cuttlefish posted.
AFOAF -
I think part of the trick is setting it up with the right tail rocker and vee. Measured with a straight edge at center, there should be a decent amount of overall tail rocker. Side to side, I guess the vee is up to you. I'm not sure how your fin set up was but the DVS has what looks to be a 2+1 with pretty small sidefins. I don't have any specific numbers.
A Bonzer is a logical extension of the same concept.
yep done em for years on my hp quads…
this was a flat bottom, hard edge, the rocker went wonky at the last 2-3" or so.
I didn’t ride the board much, admittedly…my buddy seems to be doing alrigth on it.
.
…looks like a concave for me…
Nope, I’m not that clever! It was on my second board ever, and first with concave. It was really just a mistake of not foiling properly. Rode it and could tell something was different. Put a straight-edge on the bottom, and saw what I did. I’ve gotten the same feedback from others who have ridden it. Super fast and loose on weak waves, but unstable when it gets above shoulder high.
I have a super old wave tools 6' single fin pin by lance collins. it has the same deal with the inverse rocker on the rail, no concave, just a vee that peaks before the fin, and fades out to flat. Its a fun board, but I don't surf it much.
side question though... what are your experiences with boards like these in bigger stuff, and do they feel sluggish on rail cause of the drag on the end of the tail?
thanks
