Concave depth

[mical]

About to make a 5'8" x 20" x 21/2" thruster White Diamond style sled.

Looking at around 27 litres of volume.

I have the wide point just a touch forward of centre.

Wondering about the concave, I know it's a 'deep single' but how deep is deep?

Never having touched one and probably not likely to, I thought I'd ask here.

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[Natho]

Why do you want to go deep?

I take it that with that type of board you are keeping the rocker fairly flat?

If you are not sure about going deep, esp if you have not worked with deep concaves before...Its an easy way of stuffing a board if you don't know what you are doing. I would say keeping the concave more on the slight side will be a safer bet.

Deep concaves tend to require a fair knowledge of placement/ rail rocker combo or you can end up with a dog that does not turn too well.

A slight concave should still work well in that type of board. still Im sure there are others out there who will add their own 2cents as these are only my own thoughts.

goodluck. At least you are having a go.

[mical]

Why do you want to go deep?

Just because that's what's in the Robert's model, wanted to try and keep it a similar as possible.

Had considered of keeping it more slight as it's simpler to do, but thought I'd see how difficult it is and what is considered deep.

I take it that with that type of board you are keeping the rocker fairly flat?

Nose rocker: 3 13/16, 0 13/16 and 0 1/16
Tail rocker: 0 19/16, 0 7/16 and 0 1/16

Thoughts?

[mical]

^^
Never heard of them. Where are they based? Got a number? Who of the 44 are on his team?

Back to the music thread for you

[mical]

Dino, thanks for your input .. now head on back to tangents please.

There's enough shit slinging and stone throwing over on the 'teh erBB', start your own thread if you want a fight with Mark.

[Natho]

Mical, go with the deep concave and give it a go if you like. If you stuff it up you can just put it down to learning, and then try again.

And how dare you boys put sh*t on Mr Mark.

[silvafish]

deep concaves work great..when you have a super hard edge on the rail..you can crank your rocker to blend with the concave and the thing should pull into the tube on sucky waves real nice..the sander is the man to talk to about the needed edge.

[Nick Carroll]

back it off mical. 20" is too wide for a deep concave; it'll tend to lock down on one side or other.

v slight single concave under the wide point dropping back to subtle double concave through the fins and a v slight vee just behind the back fin. This combo will put just a little bit more rocker along the last foot of rail before the tail, where you need it to turn, and allow the board to roll from rail to rail a little easier, while preserving a bit of lift under the front foot.

Super concaves belong on narrower boards with a lot of rail rocker and they take a long time to master in design terms.

[lovenutz]

How do you measure your 27 litres of volume?

what do you relate this with in terms of your weight etc?

I just read some article about Matt Bilois talking about finding your ideal cubic volume or something

http://www.stabmag.com/jed/stabs-guide- ... r-dummies/

[Natho]

With modern day surfboard design software, measuring board volume is easy. Its spits out the volume for you.

Its interesing stuff. Makes you realise that there are so many variables that affect board volume other than the dimensions that are written on the stringer.

[lovenutz]

how do you compare your boards cubic volume to your weight etc? Really interested in this..

[mical]

^^
A good start

back it off mical. 20" is too wide for a deep concave; it'll tend to lock down on one side or other.

v slight single concave under the wide point dropping back to subtle double concave through the fins and a v slight vee just behind the back fin. This combo will put just a little bit more rocker along the last foot of rail before the tail, where you need it to turn, and allow the board to roll from rail to rail a little easier, while preserving a bit of lift under the front foot.

Super concaves belong on narrower boards with a lot of rail rocker and they take a long time to master in design terms.

Thanks Nick, I'll think this over a little tonight.

I've poured over the 'White Diamond' thread on surfermag forums and most seem to say they're a deep single with a hard rail right through to increase the rail ine.

I guess this is a mix of a white diamond and lost rocket, closest two boards to what I'm after for the knee to head high shifty onshore beachies closest to where live.

Here's the rough unfinished template:

So if 20" is too wide, what's the suggestion Nick?

In relation to the original question, how deep is 'deep'?

..the sander is the man to talk to about the needed edge.

That be me also :?

Nose rocker: 3 13/16, 0 13/16 and 0 1/16
Tail rocker: 0 19/16, 0 7/16 and 0 1/16

Thoughts?

[mical]

Also, if I make the vee out through the tail slightly deeper how would that go with a 2 +1 large twin + smaller trailer setup?

Sorry, trying to learn as I go here.

[Nick Carroll]

well whatever they say on surfermag forums, 20" is quite a way from rail to rail. The wider the board, the longer it takes you to shift the board from one rail to the other, thus the slower the turn response. And one of the effects of deep concave is to exaggerate the distance from rail to rail -- to make the board feel wider than it is.

So you end up with a board with considerable lift but slow turn response.

Somewhat defeats the purpose of going under 6'0" I reckon.

Another effect of deep concave is to change the stringer rocker line in relation to the rail rocker line. 5'8" is not a whole lot of length to fit in the skilful manipulation of these two rocker lines. It takes even a v good shaper a lot of boards to figure this out well -- most don't even go near it.

I dunno what the idiots on surfermag think is "deep"; anything more than 3/8" is pretty deep.

The slight vee exit should suit a small back fin just fine.

[mical]

^^
Thanks Nick, I get what you're saying about deep concave taking even good shapers a long time to understand the effects on rocker.

As I'm not a good shaper by any stretch, not sure I want to go with too 'deep' a concave. More a slight single but I thought I had read somewhere the concave on the white diamond was a 'deep single' .

The guy who machines them had this to say:

The program we used as a mother board had a single to double which we modified into a single. I had my doubts about a single with a tail that wide. I'd been told in the past it wasn't a good idea. Maybe on a longer board, that is true. I think on something as minimalist as this, the surfer is still able to easily over power the single to go rail to rail. No "catamaran" effect. We also blocked the rearward slices and put a harder edge in. Then I nagged Robert's sander with random screams of "MORE EDGE RICO!" about every 3 minutes. Anyway, clearly it works.

That's why I wanted to make this as one of my first few boards. They sound good for what I contend with quite often at my local and like they'd be fairly straight forward to make.

Then you started talking single to double to vee and I got worried.

You've made me take another look at the template I roughed out and I agree, 20" is too wide. I'll drop it to 191/2" and try to run a slight single through it back from the wide point with a little vee behind the back fin.

Wondering how I should adjust the tail width now to compensate the 1/2" drop in width, and how that'll effect my vol. Gonna have to rethink this now.

Anyone have thoughts on the rocker?

[PeepeelaPew]

...

[Cpt.Caveman]

Looks super fun to me. I've never surfed a board with those design combinations - a wider tail with a diamond to retain volume by going shorter, and to shorten the release point. I'd love to hear how it goes!

[Little]

Why don't you just buy one off the rack instead of fcking it up yourself?