Sways,
I took my new board out last weekend and it held up great in overhead surf, got in to waves easy, etc. The interesting thing was that the nose really wanted to rise up out of the water. After a few waves I compensated for this by riding really far forward with a wide stance (pretty awkward). Any idea why? Because I'm interested in the principals involved and don't want to lead the jury, I'll tell you the shape, size, fin(s), etc. later. For now, what do you think causes nose lift?
Paz,
C
Excessive tail rocker?
doc…
(gronk- written along with my first coffee of the day, bear with me please)
Uhmm, yeah, I gotta say that Curren is the prettiest surfer to watch. Not so many of what I think of as 'contest moves', more functional, fast and ...yeah, pretty.
As to twin fins and where they are placed. The Simmons boards with two fins are not really applicable here, as they were more like a traditional longboard than anything else. Maybe, yeah, I'll introduce and misapply a new term here: Aspect Ratio. That is, the ratio of length to width. Whoops - coffee hasn't kicked in yet - width to length. Awright - Simmons boards were low aspect ratio, long and not especially wide with respect to that.
So, looking at a Lis fish, wide and short. Aspect ratio kinda high. Fins towards the tail. How come? Well, again, we're talking about what he wanted it for, Big Rock, a nigh onto square tube, very vertical. It'd track better. Plus, fins were back towards the tail then, for everybody and everything. He made a new, short, wide shape, but he didn't break away completely from 'normal'.
Going to fins further forward, yeah, but closer to the rail too. When you think about it, what's that doing? Holding the edge better, no? While it's doing that, it tends to track less and be more able to make very large redirections.
An analogy: fighter planes used to be designed with aerodynamic stability: they would be able to fly themselves if you took your hands off the controls. Good for the pilot, but if you needed radical maneuvers you had to break away from 'flying comfortably', y'know? Enter computers and 'fly by wire' controls: you could then introduce designs that were aerodynamicly unstable, they wanted to turn all the time. But the computer kept it on the straight and level until the pilot input control forces. And then it'd turn like a sonofabitch, faster and more than the aerodynamicly stable planes that came before it.
And contest-type surfing has become mostly about radical turns, big redirections.
In any event; lets get to your board-fin combination. You want to think about a few things here. Without pictures of the board ( and yes, I find that uploading pix is difficult too - best to upload to your own site and link to that rather than directly uploading to Sways) I'm gonna have to get all Socratic on you, asking questions to which you provide the answers.
First off, what kinda shape does the fin take when flexing? Okay, and what effect will that new shape have on the board overall? Will that new shape have positive lift or negative lift, pushing the tail up or sucking it down?
Then, what's the water flow across the bottom of the board? Will putting the fin forward or back affect how it flexes? Would this account for the nose lift?
Or, how long is the adjustment? Would, then, the fin all the way back have precious little planing area behind it to counter the lift or negative lift of the fin? How about when it's forward? Would the planing area behind the fin have enough area and leverage to counteract how the flexed fin pulls the tail down?
Hope that's of use
doc...
The nose lifts because you are standing too far back. It’s that simple. I’m going to guess that this board is quite different in length from your usual ride.
Some kind of funky bottom contour, or the rocker apex is too far back?
Doc,
I don't think it's excessive tail rocker. It's a pretty mellow board all around. (I forget exact #s).
SammyA,
That's true: If the nose lifts up, scoot up. Pretty simple! I usually surf thruster shortboards, 6'5'' to 6'9''. I get my foot waaaay back on these, except to jam through weak sections. So maybe I need to correct that for this board.
You're right: This board is 5'8'', which is significantly shorter than usual.
Personally, I think the fin(s) are in part responsible, that's what it felt like. How would this be possible?
(The reason I don't want to spill all the beans on the shape because it's the theories I'm after, not justifications for them.) C
I seriously doubt that the board’s shape, fins, or anything else is causing this. I would bet it’s due to your learning curve in adapting to a much shorter board. Of course, by you withholding specifics on the board we can only guess and speculate.
How about your tail is too narrow? It’s not the nose rising, but the tail is sinking.
Either that or you got a fat ass from too much holiday eating!
Ah- and Sammy beat me to it - if it's 5'8" then we're prolly talking something piscine. And those like to have a further forward trim, wide tail or no. Ya don't do them like a standard thruster.
Going with a theoretical kinda approach, figure out the center of your planing area when you're using it, not overall. Your weight wants to be centered over that when you're in trim.
And now for the audio-visual segment of our lesson: http://www.youtube.com/watch?v=GCNHv-kJvOk
Note where he is on these things, especially on the bigger stuff, at speed - Panama, I think Back foot is rarely way back, instead it's shifted some, as need be.
Hope that's of some use
doc...
SammyA,
I've ridden shorter boards before, just not THIS shorter board. As far as not giving away all the details, it's kinda like double blind testing. A lot of stuff gets thrown around in surfboard theory--I mean, go into any surf shop and ask the kid behind the counter what a given bottom contour or rail line will do. They'll give you an answer. It will likely be BS but there's always an answer to explain a given aspect. That aspect removed, and just the phenomenon described, can we explain why based on our theoretical knowlege? Maybe I'm being lame. I'll post the dims and photos (if I can) soon. I'm telling you though, it felt like the fin--one fin--caused the nose to lift. Weird.
C
I'm not fat, the tail's not thin. In fact, the opposite. C
It's clear to me. The board is too long. Cut 8" off the nose so it won't stick up. Mike
This happened with one of my boards not long ago. The tail rocker started too early ( long blank, short board, bad idea! ), so i added more plugs a few inches further up. Goes better now.
OK, so the board is a pretty traditional fish planshape: 16.5x21x16 or so. It's about 2.75'' at the thickest, pretty dramatically foiled to the rails/nose/tail, with the foward point like 4 inches up. There is no buttcrack. It just ends flat. I surfed it with a 10'' flex fin shaped by Larry Allison (ProBox Larry). A frickin' beautiful fin. Red. The nose lifted when the fin was all the way up in the box. It became more neutral when it was seated farther back.
Sorry, I keep trying to "attach new file." No photo.
C
Well given that there is no information other than the tail isn’t fat and the board is 5’8" there is no info for any guess to be based off of. my only guess is pretty low tail rocker.
In a thousand years, I couldn't surf that good. Some of those barrels, the way he sets up for them, it's perfect. Right in the sweet spot. On a fish!
One thing I've noticed is that fins have moved up on the boards since the beginning. Lis had em back there. Simmons had em way back too. So did early McCoys. I had an old timer tell me, "That's to keep that big tail in the water." Is that right?
more or less. the further forward the fin the more the board will slide and spin. Old boards like the original fish, the simmons, and old longboards had wide ass tails; wider tails are slidey and loose so they had the fins further back to give them some traction.
Hi c-slug -
Greg Loehr's 'Theory of Pitch' lays out a few ideas. It might be worth a look.
Wow, doc, not bad for your first cup of coffee. Some really interesting points there that I hadn't considered (esp. shape of fin, in flex, in relation to bottom of board). Tonight I'll try harder to post some pix. I think that would really be helpful. However, I will say that knowing that wide tailed boards could be slidey, I placed the fin box way back, so even as far up as the fin was, it's still maybe 5" from the tail at the trailing edge (?).
I was sort of hoping someone might touch on this without me giving all the dims away, but here's my impression: It felt like the fin was a fulcrum on the board, like I needed to be standing right on that fulcrum or the teeter-totter would spill the contents. I never really thought of fins like that, I suppose because on a thruster there isn't one point, there's a cluster. And I almost always try to have my foot behind the leading fins (which is fore of the middle fin). In this case, a foot behind the fin is like stepping on a garden rake and getting it in the face.
On another note, the board felt like there was no fin at all--until that fin grabbed in a turn. Then I was riding the fin as much as riding the wave--rather, I was playing one against the other. It was really amazing. Very little drive but fast, and I could turn a 360 as easily at a drawn out arc (which is to say, not very easily). The waves were overhead, but mushy and not powerful. Add power and I don't know what the results would be.
So far, a fun board with lots of potential if I can figure it out. I have two fin boxes on the rail too. Also waaay back (5.5'' from the tail). They just looked right there. I showed it to a respected shaper thinking he'd admonish me. "Looks right to me too," he said. Now I just need to find a couple of fins with minimum rake to see how this combo will work. I welcome suggestions.
Thanks for all the help, and thanks for the link JohnMellor! Looks like I'm going to have plenty of swell this week to get this thing dialed. C
Turn it around backwards and try that? Or take the fins out....that will give you something else to focus on.