Ski Builders Forum

I have been at this for over 4 years and have made near 35 pairs with very few failures, really none but one I just cant ride as I made the core wayy too stiff.
We have upgraded all our tooling and materials to cnc'ed templates, core profiling and camber molds from the previous diy methods as well as a burly press and full heat.

So I have seen this in every pair we have made and virtually all skis on the shelf at your local store, but what is it?

Is it just very very hard to avoid or eliminate?
Is it the nature of this many materials in a compression laminate over a long run of 190 cm or so?

4frnts are the worst I have seen, but they are made in the same factory as many other brands that display much less of this. ??
Some of them I have seen, looks like the edge is a washboard or pseudo magnatraction.

Solomon and rossi have it too as well as all the boutique skis in the states i have seen.
DPS avoids it in what I have seen.

Nordicas are pretty solid as well as the newest atomics in the last few years.
One ski will be straight and clean while the next ski will have the denting, right next to one another in the store.

Its very hard to photograph and maybe harder to explain but I will try.

I doubt it makes a difference when you decamber the ski in a turn but just for my own anal perfectionist qualities-can I overcome it?

EXPLANATION: So when you hold the ski up to your nose and get it in a parallel light and look down the length of the ski along the cambered edge, the camber is not smooth and instead of a smooth even arc you can see denting, or in the last case of mine a single dent. Its in the same spot in each ski pressed at the same time.

We used to think it was the mold so we redid that as it happened in the same spot on each ski as we pressed them one at a time.

Now with a new top and bottom mold the single dent right in the middle as opposed to in the tail like we saw before.

It has to be a registration from the mold as its the same on each pair but we cant see it to fix it. How can the registration from the top mold go through the air bladders?-because they are super hard at 65psi?

We have allot of AL sheet between the layup and the molds.
4 18ga on the bottom and 4 on the top. heat blankets and AL cattrack also.
I noticed on3p and some others have a thicker sheet, 16 ga below the cattrack and Monkey used a 1/4" sheet on top of his mold, we have a 16ga sheet there instead.

It doesn't seem to be cattrack registration but maybe.
The pressure is greatest at the highest point of the camber but the top mold is an inverse of that.

We put blocks in the middle to make the molds expandable like the on3p molds we have seem previously.

Its very hard to see, you have to hold the ski just so and in the right light.
You can also see it when you hold the skis together and decamber the skis when standing on the tails but that can give a false reading as some larger camber skis with stiff laminates just don't decamber evenly when you hold them together with your hands.


The denting is very subtle, it doesn't show up in the grind. The skis are flatter than most on the shelf I see in my ski town.

Go look at your skis, like I describe, do any of you others see what I am talking about?

Perhaps a lower pressure like a vacuum would not cause the edge to conform to what ever defectiveness I have?

Is this why big companies press at 90-120psi?

Its rather frustrating. I really feel that I am doing everything right with the exception of real custom tailored cassettes.


Other possible causes are the use of a thicker chopped glass section just in the binding area, but I don't think so, we only saw it in the tail before.

Does this make sense?

Hypothesis' please?
Thanks

Any chance on taking a pic and then pointing out where the dent is? I checked my skis and didn't see a dent as you described.

So the dent is on the bottom/edge of the ski?

Wonder if an AL sheet might have a thin spot/weak spot causing it to deform slightly when under heat and pressure?? Is it worth trying a sample cold press and then a sample hot press to see if both register the dent? It's a time consuming test.

i doubt I can photograph it.
Seriously its in every production ski on the shelf to some degree minus a few I mentioned.
BD also has it but they are one of the better ones.
Yes base side on the edge.
Hold the ski flat out in front of your nose parallel to the ground and have a light source on one side like a surfboard shaper would use.

That's a weird one. I'm thinkin' if I had some .250 silicone mats to put under and over I'd try that to see if it lessened.

that's a good idea B, I did think of that.
I just hate to buy something and have it do nothing or create other troubles.
What durometer you think?

Good question, I'm using 80 but it was just arbitrary.

I've never seen it, but I press at 80psi in the bladder (90 plus at the laminate).

The other thing I've noticed while bending is that there are areas of the edge itself that seem to be a different density...it's possible that the edge itself is harder or softer in that location. I know some builders that have gone to great extremes to bring that under tighter control. DBS, I press pretty high these days too 75-80, but I don't think that's the issue here.

for sure. Some of the edge is obviously annealed to a different hardness. Sometimes I get an edge that is much easier to bend and I am like, woah that was easy.
Sometimes I get one that I just cant get a bend to stick when doing some of the hand bending.
But if that was the case it would be different from ski to ski and in my case the problem is identical and repeatable.
What do those builders do re-aneal the edge sections prior to layup?
Seems unnecessary.

Yep. Heat then liquid nitrogen quench. I was having issues with topsheet indentation outside of the "normal" crap we all go through. I use that blanket on top now and...tah dah! I never bothered spending the time to track every single tiny bump or height differential in my track. That's just me though.

that really sounds redic.
I bet not even wagner does this.

I only skimmed your post...
But
Do you have a vertical support in your press to prevent deflection?
The last pair I made were a flat camber underfoot and when I lay them on a flat surface I can see minute areas where the edge comes up off the flat surface then gradually goes back down to make contact. It appears to be like a series of waves. My explanation that I haven't verified is that under high pressure the steel beams I have actually deflect between the vertical supports leaving the supported areas slightly higher than the spans in between.
Not sure I am even talking about the same thing as you, but if you have a single vertical support at the centre of your press then that could be it........?

There is another side to this. Grinding. More? My stuff, such as it is ends up the exact same weight after quite a few passes at varying grits before stone finishing. Did you measure comparative edge height on the skis you sighted down?

falls wrote: Not sure I am even talking about the same thing as you, but if you have a single vertical support at the centre of your press then that could be it........?

shit

why would that effect the tail?