Stringerless - caves

The board I built for Nationals had a misshaped concave, but I liked the way it rode.

I'm a big fan of a single concave, although a typical shortboard in the ocean has a single concave leading to a double concave. The theories abound; Bernoullis, Venturi, etc. I'm not really sure if any or all of them are accurate, but I built a single to double barrel double that was exceptionally fast, but a tad sticky.

I want to try a more subtle single to double. One thing I remember about the double on the tail was that it felt drivier in a turn and didn't require as much "work" to generate speed.

I just started with a "chunk" of 2 pound EPS. and rather than hotwire the rocker, I planed it in.

I've roughly drawn the concaves where I want to shape. I'm sure I'll deviate from them as I start mowing foam, but it gives me something to shoot for.

The "missle" shape towards the tail will be where the double will is formed out of the single.

You can see how some theorize that the water captured in the single ahead of the double is forced into the double concaves and causes the water to move faster - the theory then goes on that as the water moves faster, it creates lift and greater speed.

I'll start by shaping the single towards the nose of the board and then work towards the tail, working around the "hump" to create a double concave through the fins towards the tail.

Not great photos, but gives an idea. The single concave up under the front foot:



The double under the rear foot:

Rail bands roughed in for the rails:



Principally all shaped and ready to be sealed:

With concave you are getting in to that tricky 3D territory.
When I shaped concave I foud out that I maybe need to change from my almost flatbottom rocker to more curved. Because when I planed stringer to the final depth I got negative rocker and therefore I must prolong concave more towards nose. So I guess to get more flat rocker along stringer I need to hotwire more curved shape.
Here is only video I found about shaping of the concave. I think that at old good Shaping 101 video is nothing about it.
http://www.youtube.com/watch?v=Gyp2kNFwRCk

Do you know about more resources Jeff? Swaylock etc?

Hey Petr, Swaylocks has tons of discussion about caves - you need to be careful with some of the theory because there is LOTS of conflicting information. It's principally why I just "try it" so much, it's difficult to decipher at times. Thanks for sharing that video, that's how I do my 'caves. I run one pass down the middle, then go wider with each successive pass. I think I set my plane depth at 1/16" and keep track of the accumulated depth by counting passes.

Like you point out, the 3D component is tricky, you need to do a LOT of measuring and planning before planing This current board started with 3" of nose rocker, so it was quite generous and I think it only takes about 1/8" of concave to effect 1" of rocker change. The other concept that I've found quite interesting is the overall shape of the 'cave itself. Typically we think of that as being a continuous curve from rail to rail, but there is nothing which dictates that is necessary. LOTS of room for experimentation.

Yep Jeff its all about experimenting. Shaping- riding - rethinking - reshaping - riding - etc...

LOL - shape, ride, think, repeat

next board will have caves , now did you run it double out the back or leave it flat so it will be loose?
a cave link from sways
http://www2.swaylocks.com/node/1019210

I did the most ridiculously complicated bottom I could think of. Convex nose, to single, to double, to V out the tail. I've done a double barrel out the tail and it stuck like glue - It was great fun to watch James try and do an air - the board would just go straight and he would go up in the air - no board around. SUPER fast down-the-line though. Anyway...I wanted to test something that wasn't so sticky and I can see why so many folks use a V out the tail, it's almost intuitive to shape the V where the double fades out.

Petr ,
someone said that they cut the lam off the bottom of the board then reshaped then glassed it over again to keep costs down

interesting Jim

here is another experimental stick from Kelly
http://www.surfertoday.com/surfing/1686-kelly-slater-is-testing-new-qthe-manta-rayq-surfboard-by-channel-islands
looks like Gemini

http://www2.swaylocks.com/files/images/2009/08/img_4837.preview.jpg

That Manta Ray is an interesting looking shape. The single channel out the back is cool.

SD,
So what thickness have you gone with on this board, and did you say that you wasn't going to use the special webbing on the rails this time.

Yeah no webbing on this, unless it winds up to "flexy" then I'll add something after-the-fact

Max thickness is 1 5/8 at the rails and the single is 5/16" so what is that in the...middle 1 5/16"? I'm living dangerously

no unless you use a light schedule as the webbed board. you did not see lots of fin box flex with the 4 oz. bottom on the webb board?

I'm going 4/4 top and 4 bottom on this one too. The EPS is 2# in both boards. No, there wasn't any sense of a twist off or flex in the fins, that I noticed. I've made some crap before that felt like a wet noodle That webbed board didn't give me any of that.

what about deck dings and even more bottom dings , may be fine for a pro board , but the average joe wont like to pay big $$ for a board that dings. Dings are standard on real surfboards that last 6 months to a year if you ride alot, but the board rides and flexes like you want. so whats a dude to do!!!

Which is why I am SO glad I don't have to deal with returns, it's just for personal consumption. The HD composite sandwich boards don't ding or dent and as you can see in the first photo, I was able to get weights in the 3.5 pound rabge with traction, but not fins.

also your boards have gotten thicker as well,
at least the ones i saw were thinner than 1.675

Yeah - that was a compsand from Corecell - that thing was industructable...the stringerless, not so much.

A board a week is all I ask.

SD ,
have you tried a single cave to the front of the fin box then flat out the back to keep the tail loose and happy??

Loose and happy - that's funny. Yeah, we started with straight flat and then did just like you're saying started the single pretty short - James is all grown up now and has become a powerful surfer. His surface reverse is amazing to watch as he just powers the 4.5" fins through a frontside rotation. I'm no longer worried about looseness for the young man

At about 1:00 into this you can see James pushing the fins through the wake.

http://walkerproject.ning.com/video/james-walker-lays-down-a

Wow James i very good now. Great inspiration!
What is speed of boat in that video Jeff?

Hey Petr, thanks for the comment on James. We ride with PP set at 11 mph, but you know how that is, it's not calibrated to a gps.

I was HOPING to finish this board before the weekend, but I'm behind. Hotcoat on the bottom, the deck still needs one AND I need to salvage some traction.

I may just have to wax it so that I can ride it tomorrow!

i think you are using more rocker since you started the caves , rocker adds more performance and the caves adds back the speed. bo you like the more rounded rail past the wing towards the tail compared of the .5 roundover you have done in the past and does it seem to sink the tail better for turns. with all the bumps i think you dont need wax ,or just put on water shoes

I know the surface is hideous...I tried to create a texture in the curing hotcoat and created a relief map instead That idea didn't work

I'm trying something a little different with the rocker in this board - but ues your understanding of theory is superlative! I tried to adjust the nose rocker so that it's more of a flip than continuous - so I've moved it forward about 4 to 6 inches, but it has the same height.

I do like that extra round on the rails back at the tail, it allows the rail to sink but the water doesn't wrap it as well and so releases or at least seems to release better.

A buddy of mine wanted me to fix his dads port cover on his sailboat and it has a textured finish on it , you can buy a silicone mold that you place on top of the epoxy then peal off when cured, can get at mini craft of Florida

Yeah, that's the concept, I just didn't want to spend the money and for proto's like this - NOT use traction if it turns out to be crap. Another idea is to sprinkle sugar on the tacky epoxy, it'll leave a texture and then the sugar dissolves when it gets wet...I just can't seem to get the timing right, if the epoxy is too wet, the sugar just melts and leaves a smooth, but messy surface and if the epoxy is too solid nothing happens - well you get a truckload of ants on the floor, but no texture on the board

I'll have to look into the silicone product you are referring to...but I'd really like to achieve the textured surface without spending more money.

use sand, and i am working on one myself

I will second the sand! I use it all the time on decks and docks that need just a little bite. If you find a good sand blasting company and ask them were they are doing field work alot of the time if you sweep it you own it. look for fine silica sand.

I tried sand once, maybe I used too much, or I just suck too much, I kept shredding my calf open!

So this design was GREAT fun. Super drivey and fast, without the loss of manuverability typically associated with fast boards. There are some pictures where we are going 16 or so MPH. Above 14 and you had to pump, but you could catch the boat...15 to 17 was losing ground, but you could ride the wake as long as your legs held up.

The tail released really well, but without traction, James wasn't thrilled airing the board out The other thing that I liked was the apex of the rocker. I need to draw some pictures to illustrate the concept - STICK ART!

The single to double increases the drive of the board, the fade or v out the tail kept it from sticking, but it is "stickier" than a single.

I also moved the apex of the rocker a bit forward and I think that was the biggest discovery for me. I've never seen it as an option on a custom wakesurfer, but I believe it's significant in terms of high performance surf style boards.

The apex is where the nose rocker peaks and turns into tail rocker. Some boards have almost no rocker, but a flip in the nose - super fast down the line, but it gives up manuverability. Some boards, especially stock shapes, try and pick a "reasonable" location - if it's behind the front foot of the rider, it's slowing the board down as the nose rocker is plowing through the water, but it's probably pretty manuverable.

The apex located just at or slightly ahead of the front foot, maximizes both speed and manuverability. My wonderful art work to provide a visual reference

Any one interested to see the original art be sure to drop by the Guggenheim this winter,

this board you said you were going to leave out the special webbing , did you notice the lack of snap and have you gone back to sucking at 3's ? . i did notice that your rocker profile changed in the last few boards you made.

@ Show LOL! Yes, you've finally discovered the truth, I am actually a world renowned artist.

@ Jim beam: Snap is less without the webbing and I didn't land a three - so that HAS to be the trick. Webbing is a worthwhile addition to the stringerless. I'm going back to the drawing board on outline and rocker.

The webbed stringerless has has much snap and pop as a stringered board.

yea your rocker looks like if you lay flat on a table it has no tail rocker but nose rocker starts at 16 to 18" and is 3.5 " up at nose tip

That's a great eye jim beam! I didn't note the measurement of the apex from the nose...but 16 to 18 sounds about right. Off of a flat surface the nose rocker is @ 3, the tail rocker is .75. Using a rocker stick: nose is @ 2.25 and the tail 1.

SD,
what style of glass are you using , E,S,WARP

For the proto's where I'm not sure if it'll be crap or a gem, I use 4 oz E. S if I think it's usable.

can you feel a difference in flex between e and s or its just the strength

When is the Surfdad demo month? (Since you obviously don't like my idea of a Surf & Shape camp hosted by YOU)

@ brewkettle, just strength. In my experience, thickness has a greater impact on flex than the same weight frabic but in s vs e. 4/4 x 4 e or s is pretty much the same excepts for heels dents on the deck

@ dtw, no no no! That isn't it at all. It's just that I was talking with Judy and started by saying: "Hey sweetie, dtw was..." and her immediate response was: "NOT in this house!" Apparently your reputation preceeds you.

It isn't the first time I've heard that. She would make a GREAT camp mom too.