concave

[hart]

Bryan,

Good to hear from you...it only seems yesterday (but its actually a decade and a lot ago, really) that an apprentice called out to his master.."Hey Chris, can you come and check my rails?"

"Why?" he asked

"So I know they're the same" the grommet stuttered.

"Well" the master said "You'll only have one in the water at any one time..so what will it matter?.....

"As long as they feel the same..its cool".....

The master was Chris Crozier who was shaping for PC and hundreds of other Northern Beaches surfers that were caught up in a mini-revolution of kneeboarding happening in Sydney.

The kid, was me.

I was taught to shape ambidextrously..if the tool allows, both left and right.

Whatever you do with one (fore) hand, you must do with the other (back) hand.

All about (a)symmetry of form...a bit like kneeboard surfing itself.

And any hand crafted product, must reflect the hand from which it came. There must be that understanding, albeit acceptance.

But back to concaves?

To tune them initially you gotta use a surform..after you cut it with your planer first. And all bloody surforms are right-hand bladed. Go figure.

There were no concaves in PC's era..and no (computer) shaping machines either.

But they are every where you look now..

hart.

Wax,

After all that, I'm so glad I learnt to type. Not.

BSH

[hart]

Sanding blocks (whether they are hard or soft) are finishing tools.

Used to clean the cuts of the previous stage.

And because of that rigid little thing right in the middle of a blank (stringer)... blocks cannot be used efficiently for strokes that cross from one side of the stringer to the other, cause the stringer (being harder) will stay high while the foam on either side gets dragged down. (Which is why some guys intentionally shape double-concaves..but I better not go there)

Concaves must be cut long before we get to the block stage.

They must be planed-in initially (36,000rpm planer) and then tuned with a surform.

Once you get the depth and the shape..it gets cleaned-up with blocks.

I use 2 different types of block (hard and soft) with 4 different stages of grit to 'clean'.

But use a planer and surform to 'shape'.

hart

[Jon Manss]

I always rough out my concaves with my planer but the last time I shaped a board at Freeline John had a nifty tool made out ot 1/8th inch plywood 4 inches wide 12 inches long with two blocks of wood attached to either end and a string streatched on top of the blocks. The bottom of the plywood had sandpaper attached. The results was a flexable convex sanding block and it actually shaped nice concaves with solid control. I still like to preshape with the planer but this devise really worked well.

[hart]

Jon

any chance of a pic?

hart

[Jon Manss]

Yeah I'll get you one. A picture is always worth a thousand words I'll get accurate measurements also.

[Headwax]

In the library today at lunch reading surf magazines - specifically items on shapers' comments about their boards.

A lot of shapers claim their use of concave gives their board "lift".
I'm not sure exactly what they mean by this.......

Any comments?

(hey I'm up to seven posts!)

[K-man]

Been hearing that for years,and I don't know squat,but...In that same area[bottom]My understanding is that ''concave'' straightens out the rocker at the stringer..The answer to these questions.....


K

[surfhorn]

Concaves have to do with the movement/displacement of water.....much like air moving over a wing to cause lift (but wetter....lol).

[lowrider]

Welcome back HW, when did you get out??

[willli]

A lot of shapers claim their use of concave gives their board "lift".

Take it with a grain of salt and you won't be bitter
when you realize that "lift" is the new buzz-word
translation: "I plowed a concave cos I had no idea how to make the board work, but it adds 'lift' (makes it go faster) (reduces friction) (fetches a higher price) (makes me sound like I know what I'm doing)etc

probe further and you get the standard analogy: airplane wing

How does it specifically help your board? (concave)

I dunnno. Provides lift.

the dog has seen his tail.

[surfhorn]

I went through the concave thing years ago. Now I'm old and boring...just a rounded vee nose into flat midsectin and vee on out.

Speaking of airplane wings, in 1969 my friend and I glued a wing from a model airplane to the bottom of his 8'0" shortboard...we thought it would deflect water and keep his board from pearling. Guess we should have worked in a better ventilated room........