warped base?

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backyardskier
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Post by backyardskier »

Had this happen to me for the first time, no idea what caused it to happen. I cut my bases to shape and attach edges at a later date, while i wait i press the bases down with weight.

Really posting to see how guys like on3p store skis with edges attached and not worry about wrapping.
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vinman
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Post by vinman »

I store bases with edges attached without much trouble. The warp usually comes from a base that is not relaxed.

I now cut my base off the roll, split it, heat it to 120 F for 10-15 min and cool to room temp before cutting.

This makes nice flat base sections to be cut and I don't have to worry about some curl in the base causing it to not sit flat on my template.

This also pre-warps it per-se. I was told by someone who was in the plastics field for a long time that there is a "thermal memory" in the material. Basically when the plastics are heated and compressed for sintered material they will have a sort of grain structure and there is "memory" in this somehow (paraphrasing) which can cause the material to move when subject to heat. So by "pre-warping" it you remove this memory and it will allow the material to be cut to shape with less chance that it moves after.

with using this technique I've nearly eliminated having to re-cut anything due to warped base material.
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iggyskier
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Post by iggyskier »

backyardskier wrote: Really posting to see how guys like on3p store skis with edges attached and not worry about wrapping.
Image
We always attach edges at the same time the bases are cut. We've never had issues with edges attached.

A few other things to note - our bases are pressed flat under pressure overnight before we route them (this is primarily to ensure solid vacuum while routing the base). Also, that photo represents less than a single day's worth of bases for us. We run as lean as we can so parts do not sit long (sometimes only a matter of hours).
gav wa
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Post by gav wa »

I do the same as vinman. Put a flat board in my press and put 3 or 4 base pieces in at once and warm them to 70°c for about 20 minutes then let them cool in the press. I only press that at half my normal pressure, just holds them flat.
I find its totally important for drag knifing the bases as the pieces all then keep shape properly, they go together better and if you are not rough with them they dont warp even with big sections cut from them.
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backyardskier
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Post by backyardskier »

I called crown plastics and asked them what they recommend to get the best result. Cut the base to length let it flatten out and prior to cutting to shape hit the sanded side with a flame to relieve stress.
Danielbroski
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Post by Danielbroski »

I'll have to try heating the plastic in the press.

But since I first had this problem, I have been doing a rough cut of the bases the day before I route them, (+ about a half inch or so of what the final shape is going to be), and then letting them settle. Its worked pretty well, but I still worry about them warping.
pmg
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Post by pmg »

Danielbroski wrote:I'll have to try heating the plastic in the press.

But since I first had this problem, I have been doing a rough cut of the bases the day before I route them, (+ about a half inch or so of what the final shape is going to be), and then letting them settle. Its worked pretty well, but I still worry about them warping.
I do roughly the same: Cut it with 2mm extra on each side, let it rest for at least a day and then route it in its final shape. I can easily see the warping prior to routing, at some point of the base its 2.5-3mm on one side extra and on the other only 1.5-1mm. But after routing it in shape I never noticed even the slightest warp.
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MontuckyMadman
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Post by MontuckyMadman »

I roll that shit out on the cnc and cut right away. Strap it to a template and egde it the next day. No issues.
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Idris
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Post by Idris »

MontuckyMadman wrote:I roll that shit out on the cnc and cut right away. Strap it to a template and egde it the next day. No issues.
Strap/clamping the base to the template when edging is the key.

Doing this I've managed to use some nasty base that would warp 5cm over it's length and still have straight skis in the end.

Once the edges are on your good.
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mammuth
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Post by mammuth »

Put on vacuum template, route base, spot glue edges .. doesnt warp. I even do flaming afterwards without permanent warping
Tom
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