Ski Builders Forum

i have not been using an extra layer of fiberglass underfoot but i have noticed that a lot of people are doing this. i think a too soft of flex underfoot might cause some alpine bindings to pre-release.

Recently i made a pretty soft ski for my lady friend. she mounted them with fritschi eagles. i think that the bindings will provide some rigidity on their own, but the binding might just move around in the rear heal lock, and i think they design the bindings with slop room for that. does that stress the retention screws more, or does a stiff ski stress the screws more?

do you guys think AT bindings like the dukes or fritschis provide some stiffness for the ski, or is it negligible?

I might be worried of a premature-release if someone mounted alpine bindings on a pair of soft ass skis, because the ski can bend a lot underfoot and could pre-release. although maybe the bindings account for some of this flex? when you adjust your boots into a pair of bindings, there is space for the binding to move to account for the flex of a ski.

i have a pair of dynafits on a pair of super stiff skis and i am not worried there at all, but i might be worried if they were soft underfoot. dynafits are monster of their own.

so what are other folks doing? is an extra layer or 2 of glass underfoot a good idea? is it only relevant if the skis are soft flex and mounting alpine bindings?

is there a standard for stiffness underfoot?

You should be using some type of plate retention in the binding area.

They have many different types of glass with chop and biax and all sorts of stuff. There are patented al material and rubber reinforced binding plates You could duplicate these and be in patent violation. Thinner the ski the lighter the wood....yadda. You should go to a ski factory in your region and talk to some people.

All these things should be considered, they are important if you are selling your skis to the general public.

The extra layer of glass many people use (including the pros) is for screw retention, not to stiffen the ski in that area. The core is so thick there, flexing is minimal (I realize that's a general statement that isn't necessarily true for all skis)

During my short time working for a large ski manufacturer, I did quite a bit of testing on screw retention with different layers of glass in this area. Both pull-out, and stripping by over-torquing the screws.

I wonder if a mount job on purely wood would have similar strength characteristics compared to the same wood with a layer of 20 ounce glass. Composites are brittle and don't do a great job with mechanical fasteners, so maybe in reality the wood will do most of the work.


Rubber reinforced glass. that sounds sick. i like the concept. i would like to see some of the R&D going into that.

Just mount the f***ing bindings and go skiing!

Some flex is to be expected and is part of the ski design. I would not work on the assumption that binding are built to support this. You can approximate this with a comparative test against commercial skis. This is your safest route to understanding the issue.

The density of the core material is the most important factor in respect of binding retention. The layers you see being added provide an additional 5-7%, in terms of pull out testing. The loads you are concerned about are shear forces ... our fabrics are not orientated to support this.

Adjusting the thickness and density of the core is your quickest route. Add a metal binding plate, if you want to compromise the thickness.

Not sure how it all factors in, but the base of any alpine boot is darn stiff too, and your "fastening" that down to the binding as well.

I always put down an extra layer of glass as a precaution to screw rip-out, not to increase the ski stiffness (though it does some)

ISO8364 might help you ... google it but it's not free

Forgot about those ... yep, a much better route to a safer design!

I have posted a lot about binding rentention related concepts. I figured there was an iso standard. I don't really want to shove out 80 Swiss franks to see it though. Can you guys summerize? What's the secret to a safer design?

What weight and what type of glass binding mat are you guys using.

And do you feel like it adds stiffness? If so how much do you decrease core thickness to account for this added stiffness?

Ive just been adding an extra layer of triax from a left over bit of 22oz.
Once that's used up I'll probably use 19 that I'm using for the rest of the ski.
I don't think it really adds much stiffness to the ski but definitely gives a little extra for screws to bite.
That part of the core doesn't have much flex to begin with.

sam

do you taper the ends into a diamond to feather the flex at all? I was thinking of just using some chopped strand mat but wasn't sure what weight to use.

I use my leftover 20oz triax, an 18" long piece just to cover the most common binding mount patterns.

Ya I usually cut a bit of a taper and most times the glass is pretty frayed so blends in OK.
Some skis you can see the reinforcement better than others.
I think chopped strand would be better, I'm just using what I have.
You can see it here.



sam