Rocker mold help

For discussions related to ski/snowboard construction/design methods and techniques.

Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp

Post Reply
COsurfer
Posts: 357
Joined: Sun Jul 11, 2010 1:42 pm
Location: Evergreen, CO

Rocker mold help

Post by COsurfer » Mon Nov 21, 2011 4:28 pm

I am making a full rocker mold and trying to figure out how much rocker in my mold to get a final tip/tail rise of 8mm-ish. I tried a 10mm rocker mold and the board went flat out of the press. I tried to search the forum but that is pretty much useless. Any help would be greatly appreciated.

Huck Pitueee
Posts: 192
Joined: Tue Mar 15, 2011 2:51 pm

Post by Huck Pitueee » Mon Nov 21, 2011 4:57 pm

the first board I molded came out nearly flat. So I went to a 3 layer core. Lots of work but comes out of the mold spot on.
base layer with inserts.
Image
mojomo005 by Huck Pitueee, on Flickr

Middle layer with tapers

Image
mojomo006 by Huck Pitueee, on Flickr

top layer

Image
mojomo007 by Huck Pitueee, on Flickr

Huck Pitueee
Posts: 192
Joined: Tue Mar 15, 2011 2:51 pm

Post by Huck Pitueee » Mon Nov 21, 2011 5:12 pm

I keep thinking the top layer of glass should be the pre stressed and cured sheet you can buy. I haven't tried it yet. When you mold a full rockered board the top layer of glass is being compressed as it gets molded.

24Dave
Posts: 102
Joined: Mon Oct 03, 2011 2:14 pm

Post by 24Dave » Fri Nov 25, 2011 10:22 am

HP, I don't get it. Wouldn't you only be compressing your top layer of glass if you glassed the top layer and cured the core flat, then pressed the core into the mold and laminated the bottom layer. A rockered ski/board made from a flat core would, at rest, would be held in a rocker curve from tension on the top layer and compression on the bottom layer. Same for your wood layers, except you can create a lot stronger curve in the core the way you put them together than just relying on the composite to hold the rocker and tip and tail curve. Wouldn't you laminated core hold the shape, and your glass layers wouldn't be in tension or compression?
-Scooby2

rockaukum
Posts: 558
Joined: Fri Nov 03, 2006 9:23 am
Location: Placerville area

Post by rockaukum » Fri Nov 25, 2011 10:49 am

I have done several skis and a couple boards with rocker. I do not use a heated press. I do heat the room to about 100* or so depending on the weather. You may find luck by leaving the board in the press for a full cure. Check epoxie recomendations for times. I have not measured the amount of relaxing the skis do as I just don't care too much. But it seems to be about half. If I shim the press to 8mm i would get about 4mm finished rise, kinda the same for camber. Check old pressings and measure the camber of the finished product vs the mold used. Good luck
ra

Huck Pitueee
Posts: 192
Joined: Tue Mar 15, 2011 2:51 pm

Post by Huck Pitueee » Sat Nov 26, 2011 3:44 pm

24Dave wrote:HP, I don't get it. Wouldn't you only be compressing your top layer of glass if you glassed the top layer and cured the core flat, then pressed the core into the mold and laminated the bottom layer. A rockered ski/board made from a flat core would, at rest, would be held in a rocker curve from tension on the top layer and compression on the bottom layer. Same for your wood layers, except you can create a lot stronger curve in the core the way you put them together than just relying on the composite to hold the rocker and tip and tail curve. Wouldn't you laminated core hold the shape, and your glass layers wouldn't be in tension or compression?
-Scooby2
Proof that the top layer of glass gets compressed is I always see waves especially on the tip & tail where the glass is bunching. Yes the core without glass would hold the shape of the mold some but there would be some spring back. The reason the 3 layer core holds its shape is because the layers slip against each other. Just the act of pressing the top layer into a rockered mold is trying to shorten the fibers. Just think that each layer of materials farther from the mold has a tighter radius and if it doesn't slip against the other layers like a pre cured sheet would the fibers would be forced to shorten.

Post Reply