sin9le concaves

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alakaboo
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Re: sin9le concaves

Post by alakaboo » Mon Jul 04, 2011 9:29 pm

think you might be on the wrong forum Natho, no one here knows squat about design :lol:
Natho wrote:I gave a mate a go who is a great surfer and is very good at picking up on technical aspects in a board.
I'm neither of those things, but I think I get what you mean by twitchy. Only way I can describe it is in snowboarding terms...
It's like when you are riding on the groomed slopes but there was a small powder fall over night (2 inches or so). when the board is flat you are riding powder and it feels loose, when on a rail you are engaged with the hardpack underneath. When transitioning between rails there is a feeling of weightlessness that is similar to what I think you mean.

I like single concave forward in boards that I use in a-frame peaks with steep takeoffs. Immediate lift without a bottom turn, and typically I am not going to turn until I am on the shoulder and it's an all or nothing turn. But only up to about 3 foot. Above that you can get the squirrely twitchiness I think you mean.
And only in slightly wider outlines.

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Re: sin9le concaves

Post by Nick Carroll » Tue Jul 05, 2011 7:40 am

Natho, yeah, you are probably experiencing the effects of increased lift from the deeper single concave. The lift is being applied to the equally increased rail rocker as you head down the line, and the board is trying to transfer the lift to that rocker. Thus a twitchy feel, which I am sure disappears as soon as you set the rail into a turn.

Deep single concaves work best when they're softened by one or more design aspects, ie a slight vee behind the back fin to release it, or a carefully worked round pin to put more curve in the outline and thus modulate the effect of lift on the rail. (Deep concaves really hate straight outlines.)

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Re: sin9le concaves

Post by Natho » Tue Jul 05, 2011 11:03 am

Thanks Nick. Yeh what you have described is what Im feeling and it makes sense. The board has less plan shape curve than what Im used to.
I have also found that twitchy feeling in rounded pins when surfing less than ideal waves. Though in that case it seems to have more to do with
the round tail pivot at the back end and less to do with concave. In that case the twitchy feeling is more in the back end.
I’ve found myself moving away from singles and back to single to double.
I find the double takes away some of the single twitchy feel and track that I have experienced. The double also helps in quick directional changes. I find once I go to a rounded
pin there is less need for the double though.

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Re: sin9le concaves

Post by Cpt.Caveman » Tue Jul 05, 2011 4:55 pm

Maybe the extra bite from the deeper concave (increased rail curve hooking into the wave) combined with the no-mans land in between when trimming flat is the cause? Just that the transition between the two states is very quick in a narrow board when its up to speed and feels like twitch, rather than disengage/float then sudden bite and redirection?

In boards for small to medium waves I tend to prefer more subtle concave around the middle/front foot, and then deepening concaves in the last 3rd of the board to help concentrate the pressure created when you put some weight back and start to turn. I love that sensation of lift/acceleration when it kicks in, and I like being able to rely on slightly smaller fins because of the extra grip from the concave.

I have different tastes to you in boards of course, so I don't know how much that applies to what you ride. I'm sure my boards are thicker foiled and more generous in volume and width, needing elements to balance out the extra lift created by that alone.
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Re: sin9le concaves

Post by diggerdickson » Wed Jul 06, 2011 11:31 pm

Im glad this topic was sorta revisted because its a bloody interesting read when I look at what Im riding and what I have ridden, a lot of what you guys are saying is making a whole lot of sence, great imput guys :D
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Re: sin9le concaves

Post by Natho » Thu Jul 07, 2011 9:09 am

Cptn correct me if Im wrong, but I think what you are describing as concave ‘bite’ is that suck to the face you get with concaves.
Like most aspects of board design it all comes down to balance. Too much of that suck to the face and your board can tend to track up the face and/or make it hard to break into a quick directional change or turn. Ive had this experience when riding deeper singles in good indo type waves. That's why I tend to like a bit of double in the back end to break up the single, allow water trapped underneath to release and allow the board to break rail to rail easier. The exception would be a rounded pin as already suggested by NC whereby you are already getting some release and rail to rail freedom from the curve in the back end.Or even a slight V behind the back fin. I think the actual placement of the concave relative to rocker, plan shape and foil also has a fair bit to do with it. I mean you look at one of those Maurice Cole super deep concave things that NC was talking about a while ago. It just shows that a very experienced shaper can still work a deep single relative to the other design aspects of the board. Put a deep concave in the hands of a less experienced shaper and there's less chance of a good board as its easy to stuff a board using deep concaves.
Call me old school but Ive never been a fan of extremes in board design in general, for myself anyway. That's why I find some of the older generation shapers such as Simon, Dahlberg, Eagan etc shape boards that just go. Normally there are no extremes and everything just blends and works.

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Re: sin9le concaves

Post by diggerdickson » Thu Jul 07, 2011 9:39 am

mmm, good post natho, Ive been thinking with concaves of a subtle single, leading into flat between the fins and after the trailing fin a slight v, this should realease the water okay, nothing in the extreme at all, Im going to try this on a twin fin. What are your thoughts here, would be intereted to hear if anyone has this sort of set up.
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Re: sin9le concaves

Post by Natho » Thu Jul 07, 2011 10:54 am

Digger Im no particular expert however to me one thing that Twin fins lack is a feel in the back end for the centre point of the board. That’s one reason why many shapers started running a V between the fins on Twinnies. Later on Simon came along with the thruster which then addressed that problem. Just going flat through the fins alone on a Twinnie says to me that you are going to end up with a rather sk8ty feeling board. A slight V out the back will help to a point, however to me it makes more sense to run the V through the fins. Even more so if you are shaping a wide board. The theory is that the spine created by the V through the fins will give some sort of centre point feel between the two twins.

To me the benefit of concaves are best felt between your stance rather than just forward. Just running a single through the fins may not address the Sk8ty feel either, however a double or Con V combo would in my opinion. Anyway Im sure there are others on here who will have more experience with Twinnies and design than me.

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Re: sin9le concaves

Post by diggerdickson » Thu Jul 07, 2011 11:24 am

mmm, food for thought natho, cheers mate
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Re: sin9le concaves

Post by Natho » Thu Jul 07, 2011 11:54 am

The other thing to think about is how the water is going to flow under the board. Normally with concaves the water is channeled right through the board either with a single right through to the tail, a single into a double, a single into V or single into Con V. Thinking about it, a single up front then going into flat kind of doesn’t make sense to me as far as a clean flow under the board. It’s like you’ve got a single up front channeling water into a awkward flat section which is not going to be too friendly in channeling and releasing water flow under the board. Only my thoughts.

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Re: sin9le concaves

Post by black duck » Thu Jul 07, 2011 2:02 pm

Basic ignorance 101 - question from a non-shaper :

If you have a single to double concave, doesn't that mean you will also end up with V through the tail, albiet a soft(ish) V ? Creating a double concave must, by it's form, generate a soft V between the caves, no? Is it not called a vee because it's too soft? Not sure about the definitions here.

My Bourton round tail quad is spec'd up as having V in the tail. The V is so soft as to be hardly noticeable. Not sure how it translates in enhancing rail to rail transitions when the V is so soft. The subtlety is somewhat lost on me.

I haven't seen well defined and "acute" V through surboard tails for a long time ('cept for the odd twinnie). Not saying they aren't out there, just not common in standard shorties. Just a thruster thing?
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ric_vidal
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Re: sin9le concaves

Post by ric_vidal » Thu Jul 07, 2011 2:26 pm

Some other considerations...

how much of a board is in the water at any given time?

is the water actually moving along the full length of a board, laterally across it (say when turning) or a bit of both?

are we trying to 'have' speed or generate it?

planing area, displacement or other

Lots of considerations, no hard and fast rules. There may be some popular variations that have been around a fair while. But even in a single to double, which is more effective, the stringer higher than the rails for double in single?

May just depend on how you like to, or can ride. Even then, different waves will call for different designs.

Only one solution, try lots of boards, and when you think you have found the magic one, keep looking. :D

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Re: sin9le concaves

Post by dUg » Thu Jul 07, 2011 9:10 pm

... and then there's the blend from single to double... and how that's done. In my case, usually very badly.

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Re: sin9le concaves

Post by diggerdickson » Thu Jul 07, 2011 10:02 pm

dUg wrote:... and then there's the blend from single to double... and how that's done. In my case, usually very badly.
hey dug, blending aint easy, try blending channels in, its now my waking nightmare, but mate, gotta keep trying :D
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Re: sin9le concaves

Post by Davros » Thu Jul 07, 2011 11:16 pm

I remember a thread about concaves last year or so, it was a bit of a debate about concave depth, at the time I have a board with the deepest single to double concave and for me I just didnt dig it, seemed to bog at bit and the bottom turn seemed to be really pronounced (rider no doubt as well and could be the rounded rail etc...)...anyway have been enjoying longer more shallow concaves at the back with knifey rails.......

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Re: sin9le concaves

Post by ric_vidal » Fri Jul 08, 2011 9:46 am

Davros wrote:...anyway have been enjoying longer more shallow concaves at the back with knifey rails.......
You should read Geoff McCoys take on rail edges, Davros. Quite a different slant... then there’s the loaded domes...

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Re: sin9le concaves

Post by dUg » Sat Jul 09, 2011 1:33 pm

diggerdickson wrote:
dUg wrote:... and then there's the blend from single to double... and how that's done. In my case, usually very badly.
hey dug, blending aint easy, try blending channels in, its now my waking nightmare, but mate, gotta keep trying :D

digger oddly enough I don't reckon blending channels is as hard - but I have always gone from a totally flat area mid section into them. getting the channels themselves right... that's a different matter. :shock:

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Re: sin9le concaves

Post by diggerdickson » Sat Jul 09, 2011 9:01 pm

dUg wrote:
diggerdickson wrote:
dUg wrote:... and then there's the blend from single to double... and how that's done. In my case, usually very badly.
hey dug, blending aint easy, try blending channels in, its now my waking nightmare, but mate, gotta keep trying :D

digger oddly enough I don't reckon blending channels is as hard - but I have always gone from a totally flat area mid section into them. getting the channels themselves right... that's a different matter. :shock:

dug, thats funny, for me its the other way at the moment, though I did stuggle with doing eight, but last pratice on six come out bloody well, but struggle blending em in.
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