Ski Builders Forum

Hepp

A friend of mine wants a fish tail on a cruiser board - not pow only and I am a little afraid that it will be to soft in the "fish" part of the board if I build it as I normaly would.
All you guys that have made fish boards, have you compensated by beefing up the core thickness in the tail? and if so, how much?

what is the relationship between core width and strenght? can I somehow calculate it to end up with the "same" feel as I would get in a normal tail?

- Petter

I have cut a few factory boards with quite deep swallow tails and found them to ride really well so increased thickness on the tail is not criitical.
Having said that when I build my own I do make them thicker in the tail because I love a really stiff tail for carving.

The Burton Cruiser 165 from the 80's were thick all the way back. Worked then and should work now...

I dont compensate on the thickness of mine, mind you they spend most of their time in soft snow. I think extra flex in the rear is part of the intension of the design. It you plan on bashing lots of hardpack a little extra beef couldn't hurt, Maybe add 1mm to the core thickness?

I got this beam calculating formula from a friend;

normal width x normal thickness in 3rd = new width (fish tail width) x new thickness in 3rd

I don't know how to write these matamatical numbers and symbols on the computer and my math skills are very rusty, but I think it goes like this:

Exampel with a 4 mm core in a 300 mm wide board turned into a 100 mm wide fish "arm" with same flex.

300 x (4x4x4) = 100 x (YxYxY)

Y = square rote in 3rd of ((300 x 64) / 100)
Y = 5,77 mm

It opens up a few nice design possibilities if it works out. In my calculations above, one of the "arms" should have the same flex as a normal tail. When on edge it would turn and feel like normal. But when doing a ollie, and using both "arms" at the same time the tail would be what equals 5 mm in thickness and a lot stiffer with more pop..! ? Yes yes I know that a fish tail on a park/pist board is a stupid idea, but a soft, smooth and goodloking ride with pop, ahh maybe not so stupid after all.

an almost 6mm thick tail is not going to provide any pop whatsoever, if that's what you're going after.
It's going to be too thick to be flexible.
If you're concerned the tail of a standard design may be too thin, try stepping up in half-mm increments. If your normal core tail is 2mm, try 2.5mm. or try pushing the taper back towards the tail a couple of cm.

I am afraid that you might be right but the 4mm turning almost 6mm was an exampel. Using the formel above, "moment of inertia", the thinner the tail is the less incresment there is and it has to be calculated with the width. So if the end of the tail in the fish is 1/3 of the width of a normal tail and supposed to work as a normal one, 4 mm of normal thickness would have to be made almost 6 mm. 2 mm "normal" would turn 2.88 mm. If I put on one extra mm all the way the flex pattern will change as it will be stiffer in the thinner parts and softer in the thicker (closer to the binding).
But maybe it is possible to design the fish in a way so that it fits with an extra mm all the way. With a simpel V-cut, the thin ends would be ca 1/3 of the width and need an extra mm. Further up the board it would be closer to 1/2 the width. 4 mm in half the width = 5.04 mm
I am way out of my engineering skills here, this is me trying to theoris ski/snowboard - building, but at least it is a starting point for some simple experiments with woodcores and weights - and that is a lot more me!