Hi, I've been "doing my reading" for a while now and my son and I want to build some skis. This site is an amazing wealth of information thanks to all the contributors.
Six months ago the plan was to build a single ski, heated press as it seemed it would make things more economical and we're not going into business. After talking with friends, and of course doing more reading, a two ski press became the plan. While looking into other parts of the puzzle like cat tracks, bladders, molds etc. I came across the single ski press system Shif has set up. He obviously has it dialed. What intrigues me about his set up, among many things..., is instead of the typical cat track with square tube strung together, he's using sheets of plastic and hardboard and a bladder with sufficient contact area.
This method would seem to generate really good contact even in the tips and tails where some have had issues with gaps.
What are the pros and cons of these two methods?
Thanks for any advice.
Press
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
Thank you for the accolades.
The biggest negative to my set-up is that I have to make a close-fitting upper form for each lower press form I build. It's not difficult but takes more time and creates more tooling to store.
I'm also limited by only pressing one ski at a time. It's not very efficient doing all the prep and clean-up work for two lay up sessions per ski pair.
Also, going without a cat track limits the maximum ski width I can build. My bladder is maxed out at about a 140mm wide ski. If I got a larger firehose, too much hose would overhang the ski outline and cause my hardboard and plastic sheets to deflect into the lower press form. This would create issues getting good contact pressure on the laminates of the ski, there would be pressure voids along the top edges. I did some tests to learn about this.
The biggest positive aspect to my method is the excellent contact pressure in the tips and tails of the ski profile. The key is to keep the bladder as flat as possible to maximize the contact area.
The other advantage is that I don't have to fabricate and handle the cat track assembly.
Overall I think for garage hobby ski builders my method is fine. For any sort of limited production endeavor, the double-wide cat track and cassette method is a much better choice.
Cheers,
-S
The biggest negative to my set-up is that I have to make a close-fitting upper form for each lower press form I build. It's not difficult but takes more time and creates more tooling to store.
I'm also limited by only pressing one ski at a time. It's not very efficient doing all the prep and clean-up work for two lay up sessions per ski pair.
Also, going without a cat track limits the maximum ski width I can build. My bladder is maxed out at about a 140mm wide ski. If I got a larger firehose, too much hose would overhang the ski outline and cause my hardboard and plastic sheets to deflect into the lower press form. This would create issues getting good contact pressure on the laminates of the ski, there would be pressure voids along the top edges. I did some tests to learn about this.
The biggest positive aspect to my method is the excellent contact pressure in the tips and tails of the ski profile. The key is to keep the bladder as flat as possible to maximize the contact area.
The other advantage is that I don't have to fabricate and handle the cat track assembly.
Overall I think for garage hobby ski builders my method is fine. For any sort of limited production endeavor, the double-wide cat track and cassette method is a much better choice.
Cheers,
-S
Thanks Shif, that was quick.
Can a adjustable press form be used? It seems to me the forces across the laminate would vary using either method based on the accuracy of the upper and lower press form fit?
The ski width issue makes sense. Could you add extra 1/4" hard board to stiffen the form? What size hose are you using?
You mentioned in a thread that a two ski press might be nice some day. Would you go with the same method or switch to the tubular cat track?
Can a adjustable press form be used? It seems to me the forces across the laminate would vary using either method based on the accuracy of the upper and lower press form fit?
The ski width issue makes sense. Could you add extra 1/4" hard board to stiffen the form? What size hose are you using?
You mentioned in a thread that a two ski press might be nice some day. Would you go with the same method or switch to the tubular cat track?
Many here have built adjustable press forms to build skis in different lengths. Seems like a lot of work to me.
I could add more pressure distribution layers to help prevent the bladder from bending things down over the edge of the ski core. I’ve not needed to do that since my preferred ski design is 138mm at its widest point.
My fire hose is only 4 inch diameter which flattens to about 6.25 inches wide. I have to really squeeze things together when loading into my press frame to keep the contact area wide enough to cover my ski design. I wedge pieces of MDF between my upper form and upper I-beam prior to inflating the bladder.
A two-ski press and forms is ideal but would be difficult to handle using my technique. I assemble the ski (lay-up) directly on the lower form. Then I add pressure distribution sheets, the bladder, and the upper form. Then load the whole enchilada into the press frame. A two-ski form would weigh too much and make this process difficult or impossible. The cassette method is much preferred for building two skis simultaneously. Watch some of the excellent manufacturing videos linked to from the forum, all production builds are done using the cassette and cat track method. Since I only build skis occasionally, my method works well enough.
How committed are you and how much money are you willing to risk? A dual-ski press adds to the tooling cost, and if you screw up during a lay-up, you lose two ski cores and base assemblies. A single-ski press is less efficient but also less expensive to build.
Good luck,
-S
I could add more pressure distribution layers to help prevent the bladder from bending things down over the edge of the ski core. I’ve not needed to do that since my preferred ski design is 138mm at its widest point.
My fire hose is only 4 inch diameter which flattens to about 6.25 inches wide. I have to really squeeze things together when loading into my press frame to keep the contact area wide enough to cover my ski design. I wedge pieces of MDF between my upper form and upper I-beam prior to inflating the bladder.
A two-ski press and forms is ideal but would be difficult to handle using my technique. I assemble the ski (lay-up) directly on the lower form. Then I add pressure distribution sheets, the bladder, and the upper form. Then load the whole enchilada into the press frame. A two-ski form would weigh too much and make this process difficult or impossible. The cassette method is much preferred for building two skis simultaneously. Watch some of the excellent manufacturing videos linked to from the forum, all production builds are done using the cassette and cat track method. Since I only build skis occasionally, my method works well enough.
How committed are you and how much money are you willing to risk? A dual-ski press adds to the tooling cost, and if you screw up during a lay-up, you lose two ski cores and base assemblies. A single-ski press is less efficient but also less expensive to build.
Good luck,
-S