How much Camber is generally built into mold?

[Skivolkl]

How much camber do you all generally built into your molds. I am in the process of building a new mold (my old mold did not has a constant arc on the camber, I ended up sanding it down to much(stupid mistake)). I quess the question is how much camber is generally retained in the ski after it is removed from the mold. It seemed that I was loosing approximately 7 to 15 mm of camber in the skis I made in my previous mold (I was vaccuum bagging, not sure if that makes a difference). It would be interesting to know what all of you have experienced.

[BigG]

What I could read in previous topics is that it depends from what kind of curing process you are using.

If you are using a heated press the camber won't change a lot in comparison to the camber on your mold.

If your skis cures at room temperature the camber will drop a bit.

It's also depending on the used materials or maybe it's better to say it's depending on the layering order.

I hope I'm right.

Geoff

[G-man]

I built 16mm of camber into my mold, figuring that I'd lose about 1/2 of that in the end product. I over compensated simularly in the curves of the tip and tail blocks, as well. I decided to go with a heated press, and so, also went with the heat cure resin system. After pressing, my skis have exactly the same dimensions as my mold. I can place a finished ski back in the mold, and it fits like a glove. During the pressing operation, I first inflate my press to 25 to 30psi, then turn on the heaters. When the temp in the mold reaches 110 F, I increase the pressure to 50 psi. The temperature then continues on up to the the preset 175 F. I let the ski 'cook' at 175 F for 60 minutes, then shut off the heater, leaving the bladder inflated. After a 30 minute cool own period, I deflate the bladder and remove the ski.

I know that some builders have reported that a rapid run up to high temps has resulted in greater than built in/desired cambers, but, mine has remained exactly the same as the camber block... at least so far... go figure.

So, I have skis with 16mm of camber. I think that they'll be just right for early morning steep spring corn... and it looks like around here, we'll have spring corn well into mid-summer. Yaba-daba.

[Mutombo]

I´m drawing the press design. As all of you say I´m going to give about 18 mm camber in order to have a final camber of about 9 or 10 mm. I´ll cure the skis at room temperature so I hope this will be the final result. I´ll post you to show waht happens.
In the other hand, I´m making my skis design and I have a doubt. First of all, I´ve done the sidewalls with an arc and then a spline to close the tip and tail but in this way you have a symetric shape that is no good for smooth running. I think that maybe giving a diferent radius to the front side and to the back side could be the solution. I´m going to do this in order to have about 10 mm more in the tip to the tail but I don´t know if this is what you do to get sidecut.
Any help?

[Buuk]

@Mutombo:
About getting a smooth running ski / tip. I also use an arc to draw the sidewalls and a spline to close the tips. But I probably create the spline a little bit different as you do.

In the first place I create a spline that is connected to construction lines (not a lot of CAD programs support this, SolidWorks does) this makes it easy to change the dimensions afterwards. If your program does not support this you can also use construction lines and then add points to spline as close to the construction lines as possible. Then also draw a small vertical constuction line (the one of 10 mm) from the end of the arc.
Finally draw the spline from the end of the arc to the end of the 10 mm line etc. Maybe you have to experiment a bit with the dimensions, but this will give you a smooth transitions from arc to spline.

Hope this is a little bit clear. If not just tell me.

Buuk

See the screenshots below for a visualisation of the above.

Sorry for the large picture! Just trying to make things clear...

[Mutombo]

Thx man, we finally solve it. The answer was easy. We made the tail shorter than front side so the tip was wider than the tail. All with the same arc. I´ll post a picture of the AutoCad file so you can see it