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Constant rocker or flatter center section to make concave?

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plummet
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Constant rocker or flatter center section to make concave?

Postby plummet » Sat May 24, 2014 11:29 pm

Hey bro's

I have rightly or wrongly always based the rocker I want from the rails of my board builds. I then reduce the rocker in the middle of the board to create concave.

Does anyone do it the other way around. IE select their desired rocker for the center section and then increase rocker at the rails to create concave?

Discuss. ................

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rynhardt
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Re: Constant rocker or flatter center section to make concav

Postby rynhardt » Sun May 25, 2014 8:50 pm

Hey man.
I've only recently started looking at board design, but from what I've read there's no clear answer.
Different board features such as rocker, outline, concave, edge shape etc. will combine to provide one specific use case which is ideal for for a specific combination. I.e. a different boards will be best for different conditions.
Correct me if I'm wrong, but more rocker gives a softer ride over chop, and carves better, but is slower. Light wind boards generally have less rocker.
Concave gives a softer ride over chop, carves better, is also slower than no concave.
When combining rocker and concave, you can also start looking at the effective water line when you are edging, and supposedly if that is a straight line then you win in the efficiency again.
Another aspect to consider is that a double curvature gives more rigidity for a given volume so you can probably build a lighter stiffer board than an equivalent rocker flat bottom.
And then there are a multitude other things to consider such as aspect ratio, channels, fins, flex.
Sorry, no answers, just more questions.

plummet
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Re: Constant rocker or flatter center section to make concav

Postby plummet » Sun May 25, 2014 11:12 pm

Yeah man. There is a ton of different factors involved. Thats what makes board building so much fun. You can play around with those factors and make a board that suits your needs perfectly rather than buying a board that sorta does what you want.

You are correct. More rocker is smoother through chop and slower but is power hungry and worse upwind.

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downunder
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Re: Constant rocker or flatter center section to make concav

Postby downunder » Mon May 26, 2014 4:49 am

plummet wrote:Hey bro's

I have rightly or wrongly always based the rocker I want from the rails of my board builds. I then reduce the rocker in the middle of the board to create concave.

Does anyone do it the other way around. IE select their desired rocker for the center section and then increase rocker at the rails to create concave?

Discuss. ................


So you effectively bending your rocker press table with a screws all around?

As I understand a flatter rocker in the middle is faster planning...

But, to lift up the stakes on a board speed, I strongly believe the fast surface is the major factor...

plummet
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Re: Constant rocker or flatter center section to make concav

Postby plummet » Mon May 26, 2014 5:30 am

I am using a 3 rib mechanical press top and bottom. For the next board I will also vac bag it as well too.

The mechanical press will press the shape I want and the vac bagging will suck out any excess resin and also conform the glass to the more complex shaping that the mechanical press wont get to.....

clear as mud?

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downunder
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Re: Constant rocker or flatter center section to make concav

Postby downunder » Mon May 26, 2014 7:20 am

Heh,

mind bonging :)

Any thoughts about an air bladder for your press? That would conform...

I do not have a room for it, otherwise would build one.

But, on your concave/rocker question one and quite important thing is how you FG your boards.

If you do not have the same FG on both sides than you can expect more or less c/r depending on your glass.

I just built one board with more concave on the same rocker table with just using a heavier cloth for the bottom (biaxl)...

How's that? Another mind wrecking thingy...

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rynhardt
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Re: Constant rocker or flatter center section to make concav

Postby rynhardt » Mon May 26, 2014 10:54 am

Took me a couple of searches to find this again, but here's the bit about the water line I was trying to remember. The rocker and concave makes a saddle shape, which if you get it right will give you a straight water line.

http://www.losethestraps.com/forum/viewtopic.php?f=8&t=942

plummet
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Re: Constant rocker or flatter center section to make concav

Postby plummet » Mon May 26, 2014 11:46 am

rynhardt wrote:Took me a couple of searches to find this again, but here's the bit about the water line I was trying to remember. The rocker and concave makes a saddle shape, which if you get it right will give you a straight water line.

http://www.losethestraps.com/forum/viewtopic.php?f=8&t=942


An interesting reed rynhardt. Cheers

plummet
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Re: Constant rocker or flatter center section to make concav

Postby plummet » Mon May 26, 2014 11:51 am

Downunder

My 3 rib mechanical press. Now imagine a vac bagging it at the same time too.

My next build will be full carbon on various angles. similar but different to the this layup on the nomad boards.

http://www.nomadkiteboarding.com/index- ... nomad.html

P1030969.jpg

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downunder
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Re: Constant rocker or flatter center section to make concav

Postby downunder » Mon May 26, 2014 12:06 pm

rynhardt wrote:Took me a couple of searches to find this again, but here's the bit about the water line I was trying to remember. The rocker and concave makes a saddle shape, which if you get it right will give you a straight water line.

http://www.losethestraps.com/forum/viewtopic.php?f=8&t=942


ry...

not sure if this is applicable to an TT tho...Rigid one like Mako, maybe, but I wouldn't ride it on my local:)

Used to own the same style board. Never again, thanks.

My reasoning why this is is not so relevant to an TT is that a fin significantly disturbs a water line. Plus, the board is not rigid.
That's why my toe fins are less than 1" high (hand made symmetrical fins). Take a fins off, I'm flying.

Also, a water line changes with edging I think. Edge harder, dig in, see the result. But, I can check with two of my prod. boards...


Plummet,

I just slapped heaps of epoxy to get the mirror shine on my board...The benefit of vac for me is just to press a FG onto the core.


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