Ripping bindings

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gladegp
Posts: 45
Joined: Sat Sep 22, 2007 2:10 am

Ripping bindings

Post by gladegp »

Hi

I've made a pair of skis with a fir core and a 22 oz glassfiber layer above, then a cotton layer and top sheet.
First I mounted my Dukes and ripped them after 2 days of skiing (this also broke the binding) then I had a store mount them with alpine bindings (Rossi FKS) using the kind of inserts that can be put in from above. These I ripped after half a day.

What do you do to solve this problem? Will a simple aluminium sheet of say 1 mm suffice or will I have to use the kind of inserts that I put in from below. This means a lot of work aligning the core and so on.
plywood
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Location: wilen, switzerland
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Re: Ripping bindings

Post by plywood »

sorry to hear that!

the solution is quite easy: the best is to not use fir ;)

no, i`ve used fir too, but it really sucks. not very tough and crap for using as sidewalls. so it definately needs some reinforcement under the binding. i did following:
straight unter the toe and heelpiece of the binding i routed out some "pockets". i did like 2 steps, a bigger pocket over the whole width of the ski, 1mm deep, and a slightly smaller one, also 1mm deep. then i filled up these pockets with 1mm veneer. plywood would work too. and finished is the partial reinforcement! furthermore i`d suggest to add an at least one extra layer of glass right under the binding where the screws get through, no matter what type of core.
so it helps a little, the screws now got at least 2mm wood and some fibreglass to grab on...better than nothing. but still not really really solid. if you ripped out a binding with inserts i`d definately go to harder wood, for example ash or something like that. the difference is huge!
on my fircore skis i could screw in the bindings by hand quite effortless. on the ones with ash - forget it.

and yeh, maybe you were really unlucky to rip out bindings twice...but i think the dukes are problematic in general as they only got one screw that holds the binding in place... you`re not the first that ripped out this screw, this happens even on "solid" factory skis. so i think the dukes need a bombproof core ;) go for ash!
plywood freeride industries - go ply, ride wood!
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littleKam
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Post by littleKam »

exactly what type of inserts did you use? the brass inserts?

I mounted a pair of Jesters on my skis with a pine core. But I used the regular inserts and they seem to work well. If you want to use fir I think it's fine, but you'll have to use the inserts that have the flange underneath the core.

BTW, aren't K2's skis made from fir?
- Kam S Leang (aka Little Kam)
TexMurphy
Posts: 42
Joined: Fri Sep 14, 2007 8:59 am

Post by TexMurphy »

littleKam wrote:exactly what type of inserts did you use? the brass inserts?

I mounted a pair of Jesters on my skis with a pine core. But I used the regular inserts and they seem to work well. If you want to use fir I think it's fine, but you'll have to use the inserts that have the flange underneath the core.

BTW, aren't K2's skis made from fir?
When you say regular inserts do you mean M6 inserts the ones found on snowboards or M5 inserts to match dimention of ski binding screws?

If you use M6 what type of screws do you use?

If you use M5 where did you find them?

Thanks in advance this is a question thta is bugging me big time.

Tex
danishstock
Posts: 18
Joined: Mon Oct 22, 2007 4:13 pm

Post by danishstock »

gladegp,

You can probably salvage the skis. Try drilling out the ripped out spots with a forstner bit (the flat bottom type) and filling the holes with epoxy. The epoxy "plugs could then be drilled and tapped for standard screws. You would not be able to simply drill a pilot hole and drive screws in.

I've never done it for ski bindings, but I have waxed the threads of a screw and poured epoxy around it. After the epoxy cures, simply back the screw out and you have a perfectly tapped hole. One of them stuck on me, so I just heated the screwdriver tip a little bit, held it in the screw head for a minute to let the heat move to the screw and soften the epoxy slightly and out it came.

There are several things you can do to prevent the epoxy "plugs" from pulling out:

1. Before you pour in the epoxy, undercut the hole with a dovetail bit in your router. This will require a bearing collar and an appropriately sized hole template. The hole will then be narrower at the top keeping the plug in place.

2. Add an additional layer of glass over the binding area and plugs.

3. You could also try incorporating inserts into the drilled out holes instead of trying to drill and tap.

Just a few thoughts. Good luck and let us know how it turns out.
gladegp
Posts: 45
Joined: Sat Sep 22, 2007 2:10 am

Thanks

Post by gladegp »

Thanks for the good answers.

The reason I'm using fir is because it's cheap and I can buy it already laminated so it's much easier. Ash is really expensive especially when I need someone to cut it up for me. And then I need to laminate and so on. As I don't have a good workplace this is a lot of work.

The duke is only mounted with one screw when mounted on blizzards or the like which have a center insert. Otherwise they are mounted like regular bindings with 8 screws. This is what I did.

The inserts we used were brass inserts put in from above. These weren't much use at all. I guess they're supposed to expand or something. Useless.

Maybe I'll try laminating on a piece of harder wood or metal under the binding. Otherwise I'll have to use inserts with a flange underneath.
I might drill holes from the bottom and put in flange inserts and then fill these with p-tex.

But apart from the binding problem my skis skied great. Great floatation, no nosedive, 120 mm underfoot and still a good carver, 195 cm long and still excellent in the forrest.
bluedog
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Joined: Fri Jan 18, 2008 8:16 pm

ripping bindings

Post by bluedog »

Have done thousands of binding mounts in skis that have much weaker cores than Fir! Some have had chipboard cores but the worst were kids foam core skis - you always had to be very careful and pre-tap the holes. I would suggest that you try and pre-tap the holes using the same screw you are mounting the binding with or a tapping bit with the same thread as the screw. Use some glue in each hole to help seal out moisture - wood glue, epoxy, or silicone sealant work well. From the sound of it, your bindings are the main cause so, here is another solution - Make a plate out of HDPE and use extra screws to hold the plate to your ski - then mount the binding to the HDPE plate. You can also drill some emergency holes to the rear or front of main holes in case you rip out while you are out skiing. Hope this helps - cheers
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