rail thickness - how design impacts performance?

General Discussion
1

OK so I am about to start on the balsa rails of my 6’8" compsand. The board will be a quad with probox’s set for a 3/4/5 fin option. The board is based on the clark 6’8"R rocker. It will be a thin wide board with a flyer (Bert style S-curve) like tail.

So the question is should a board like this have thin or thick rails?

I searched the archives and was not able to come up with anything definitive for how rail size impacts performance.

As for shape I plan to do a standard modern short board 60/40 ish with a tucked under side and hard in the rear.

The board will mostly be for So.Cal. beach break in the 2-6’ faces range.

I only really have experience riding 50/50 railed single fins and modern 2+1 longboards so not much experience with shortboard rails so some guidelines on design vs performance would be helpful. I also have a traditional lis/frey like fish. None of which resemble a modern shortboard performance.

My starting point guess is that thick rail for soft waves and thin for juice, but I have heard the opposite as well so what is a guy to think?

Thank you.

Have a Great Day!

2

You’re right.

A thicker rail extends the volume of the board all the way out toward the rail, providing more float and stability. Thinner rails ball up the volume more along the stringer, providing less float and more sensitivity. So you generally see thicker rails on boards meant to be ridden shorter - like retro fish - or boards for smaller surf. The fatter rail gives you something to push off of on a turn and helps you plane in mushy waves. A thinner rail will dig in too easily in mush surf. Thinner rails are typically used in better surf, where the speed of the wave provides all the planing you need, and the reduced volume in the rail allows it to penetrate the face (or flats) deeper on a hard rail turn, providing better hold.

Also consider your edges, or lack of them. A softer, but thicker rail will let water wrap around it more than an thinner rail with a hard edge. The more water you get wrapping around the rail, the more “suction” it creates. This translates into drag, which is good if you want a control feature, but bad if you’re looking for release - depends on the application.

3

Hey 4est,

If you copy rails off a similar board and make them a tad thinner, you-ll have the best results.

And… Thicker rails means thicker board means harder to flex. So keep the thickness down a bit too, maybe 1/8 inch, to compensate for compsand stiffness. Say normal board is 2.5, yours would be 2.375. And, since yours is lighter, it will float better too, so youll have a good board going for you.

Hope this helps any.

Wouter

4

I’m not helpin’ unless I get some points! I need to feel the love!

But seriously, How wide is the board in nose mid and tail? What thickness are you going after. A 3" thick board with thin rails might have thicker or thinner rails than a thin board with thick rails. What do you weigh and how tall are you? Lastly, what is your shoe size? Often overlooked, is a bigger foot can bury a rail easier than a size 9. Do you want to carve hard on a rail (this will send the board more vertical) or keep it flat (aim down the line).

By beach break, do you mean Zuma close-outs or Santa Monica mush?

5

So part of the thought process even before nj_surfer’s reply is a smaller rail should produce less drag and therefore should be a little faster and could be argueed as better in small weak waves?

everysurfer:

Here are some more specs: 6’8" x 13"(n) x 22"(wp) x 17"(t). I think the widepoint is 4" behind center. The blank was hotwired at 2.5" thickness, though I plan to cut a 1/2" concave into the deck. The bottom is flat with no contours. The core is 1# eps, with 1/8" balsa skins with the rails built up to 1/2" balsa, with 2.3oz glass under the skins. The plan is to use 2.3oz glass on the outside as well. Currently the bottom skin is bagged on with interiour glass only.

The board will be finned for a 3/4/5 fin option using ProBox boxes so there will be some room for adjustment. The fins will be centered in the box at 4", 5 1/2" and 11 1/2" up. The plan was to toe the front fins 3/8" and the rear fins 1/4". ProBox has adjustable cant at 0,2,4,6 degree so lots of finning options.

I am 6’2" 185lbs, though I usually surf in a 4/3 or a 3/2 fullsuit and booties so that adds a little weight. Size 11 foot.

As for surfing style… not sure currently I am a downline longboarder though the intention is for this board to be a more top to bottom verticle board.

As for beach break… it will be an all around board, till I learn more and build another more specific board. Mostly see using it at BolsaChica, Newport Beach jetties, beach just north of Leo Carrillo, and Ventura state beaches. Then I’m sure I’ll take it out in some point surf as well like C-Street, Rincon. Mostly I LB so this board is for when I go surf with shortboarders and also branch out and expand my surf experience.

Naively I had built a classic style fish thinking it would be my beach brake board, before I reallized a classic fish is a downline board and not very good in couple turn closeouts.

Thank you for the input…

Have a Great Day![img_assist|nid=1030398|title=templates|desc=|link=none|align=left|width=1026|height=234]

[img_assist|nid=1030397|title=outline|desc=|link=none|align=left|width=624|height=2095]

6

Since:

  1. The board is thin for your weight. Starting out @ 2 1/2" and then scooping out the deck.

  2. You plan on surfing Mushy waves like C- Street and Staircase (the beach break north of Leo Carillo).

  3. You are more of a cuising type of surfer.

I’d go with a fuller rounder rail, with a hard edge on the bottom up to 1/3 the board length. That will be nice and stable but will give you some down the line speed. The hard edge will let the board turn easier without carving.

Also the toe in in your front fins is too much. You are riding pretty weak waves that don’t have a lot of energy, so you need keep up all the speed you can. get.

7

"

So part of the thought process even before nj_surfer’s reply is a smaller rail should produce less drag and therefore should be a little faster and could be argueed as better in small weak waves?

"

No. As NJ_surfer explained, in small weak waves you need the buoyancy in the rail for it to be able to float on top of the water at lower speed. highspeeds generated by by big surf has the board planning easier so less foam is needed to float the board.

8

Finally someone else who believes shoe size is as important a design factor as height and weight. It’s about leverage isn’t it?

4est- I know this won’t help, in fact I’m just adding to the confusion, but my feeling is if I’m riding a 4 or 5 fin set up I’d go with thicker rails, because you’re depending more on the fins for hold and drive. If I were going to ride a three fin thruster set up I’d have a bit thinner rails. Also, my personal experience with a bonzer with very thin rails is that the board was extremely sensitive and unforgiving. I’m thinking with the dimensions you give (wide and thin) a thin railed board may hang up a dig a lot off the top and on cutbacks.

How about a medium rail??

9

Given the rest of the dimensions of the board would you consider it thin for my weight?

I’m making the assumption that after cutting the concave my effective thickness would net out about 2.25" (2.5" - 1/2" concave, between the concave and the rail will still be 2.5").

Doing some crude comparisons of volume with APS3000 the following boards are about equivalent:

6’8"x13x22x17x2.25 ~= 34.43 Liters (mine)

6’8"x12x20x16x2.5 ~= 34.5 Liters

6’8"x11x18.5x14.25x2.75 ~= 34.84 Liters

Where I am going is yes 2.25" thick sounds thin for my size until you look at the overall volume of the board and then is it not inline?

I’ll plan to go with a fairly full rail shape.

thanx