Cat Track - Alternate Design

[skidesmond]

I saw Richuks' cat track ( http://www.skibuilders.com/phpBB2/viewtopic.php?p=22112 ) and it gave me an idea for a different design. Has anyone tried making a cat track using layers of thin hard board, sheets of aluminum (or other similar material)?

It would be simple to build. My thought is to have say 4 - 8 pieces of thin material stacked on top of each other. Make elongated holes for the bungee cords hooks. The elongated holes also allow for the material to slide as pressure is applied.

Downsides? I'm thinking there might be a problem if the cat track hangs over the tip/tail molds when the pressure is applied.... Other downs sides? What do you think? Comments? Thanks.

[Dr. Delam]

My main objective with a cattrack is to get more uniform pressure distribution when pressing. Using a very stiff material helps maintain a uniform pressure distribution.

What you are describing sounds like it will not achieve this.

If your bladder completely overlaps your materials when inflated you should get good pressure.

I have been making my tip and tail molds extra long to accommodate ski builds ranging from 170 to 190. I can use the same aluminum sheets in my layup this way without having it fold over the ends of the tip and tail molds.

[skidesmond]

Thanks Dr. My tip/tail molds are adjustable and my current cat track over hangs the molds so in my case it wouldn't work. I started using s single piece of 3/4 mdf for the center of the cat track and then the typical strips for each end to accommodate different lengths of skis. The center mdf is about 50in long.

Just trying out new cheaper ideas. Thanks for the feedback.

[Richuk]

Depending on the width of your hose, you might get away with using 12 mm OSB. Cut a series of parallel three quarter depth cuts at the ends? You could reinforce with a sheet of fibreglass and face with hardboard, but then you're around the cost of AL... maybe? Its a lot less work, but you'd need to limit it to around 75 inches - I've switched to elevated tip molds, so shout if you need dimensions.

Planning ahead, if you decide to add heat to your press ... you might need to throw in some lightweight insulation board?

[Alex13]

I'm with Dr. Delam - the reason for the cat track is to create even pressure distribution perpendicular to the length of the press - the hoses we use wouldn't distribute pressure evenly along the width of the press so we use a cat track. You need something very stiff widthways that will conform to the shape of the mould.

[skidesmond]

That makes sense. Thanks for the feedback!

[SHIF]

No cat track required.
I have several different ski press forms and each has a corresponding upper form which serves to create a close fitting cavity for the ski materials and lay-flat hose “bladder”.
I place a 1/8” thick sheet of HDPE atop the ski lay-up to serve as a super smooth, non-stick pressure face. Then a 1/8” thick sheet of hardboard to help distribute pressure (both not shown here). The bladder sits atop this hardboard layer and is held down by the upper press form block.
When the forms are placed into the steel frame, some layers of hardboard and MDF are stacked onto the forms to fill up any extra space, like big shims.
Then when the bladder is inflated it can only expand a tiny amount in the vertical direction because of the close fitting cavity. This prevents the hose from assuming a rounded shape thus maximizing the contact patch. As long as the contact patch completely covers the ski shape all is good. Additionally the hose conforms nicely into the tip and tail curvature on the ski.


This shows a rockered ski form, tail end, which does not have much tip/tail curvature, but clearly shows the upper press form contour. There are no ski materials, just the form tooling.


This shows a cambered ski form, tip end. The hose stays "flat" when inflated. No ski in there, just scrap pieces.

Cheers,
-S

[Alex13]

That looks like it would work well enough, no good for those of us who make snowboards or 2 skis at once though, without a custom bladder.

Is it hard to load? I would have thought the small cavity would make things difficult.

[SHIF]

This is definitely a “one at a time” concept. It may work for snowboards, if you get a huge lay-flat discharge hose.

Loading this is simple.
The lower press form is the "cassette" in this case. The ski is built on it at the work bench and then you move it to the press frame shelf. The plastic and hardboard pieces, the bladder, the upper form, and the various shims are waiting, stacked on top of the frame, and added one by one to the ski sandwich. The whole enchilada is then shoved into the steel frame, the shims are added as needed, and then it’s pressurized.

I got a bunch of threaded plastic balls from McMaster which aid in moving these behemoths around.

-S

[Brazen]

You said balls.