screw you!

For discussions related to ski/snowboard construction/design methods and techniques.

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plywood
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screw you!

Post by plywood »

big thread: how to mount a binding.

to be honest, the typical way of mounting bindings with woodscrews is somehow cruel to your skis and a bit like back in the stoneage - primitive.

so to list up some alternative ways of mounting bindings:
-inserts, incorporated during the building process
-screwed inserts (?), the same as you use after ripping out the bindings. they have a wooden external thread and a metric internal one i think
-...what else?!

and a question to the ones that used inserts: did you secure the screws with some screwglue or something like that? because one of my snowboard-experience was a complete loss of riding control due to loose screw that came out of the inserts - it must have looked silly, front leg fixed normal, rear leg with boot in the binding...but binding not fixed to the board anymore.
never had any problems with self-loosening screws in inserts? what do you think about it?
plywood freeride industries - go ply, ride wood!
Greg
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Post by Greg »

I have used screwed in inserts on a couple pairs of skis and have found them to work really well. So, a little about them:

The screwed inserts come in two varieties: low quality made from zinc, and high quality made from steel. The low quality ones cost much much less than the high quality ones, but there is a really good reason for that. So far, I have only used the low quality version for reasons I will get into later.

The low quality inserts don't have a full thread around the insert, instead, they have flaps that stick out and thread into the ski, and the material they are constructed of is pretty weak. So, if you are going to use them, make sure you get the hole in the ski drilled properly, use some wood glue around them, and be careful about tightening them too much. When you put too much torque on a low quality insert, it breaks apart (in the ski) and will not go any further into (or back out of) the ski. My other big complaint with the low quality inserts is that the internal threads are not very durable for multiple mountings. You can pretty much mount your bindings one or two, maybe three (if you're lucky) times before the threads will be ruined. And, this kind of defeats the purpose of using the inserts.

One other issue I had with inserts was that it was difficult to find screws that would fit through my bindings. I used 1/4"-20UNC stainless steel screws, but I had to grind the heads smaller so that they would fit through holes in my bindings (Salomon S914 bindings). This may not be an issue with other ski bindings, and it should not be an issue at all with snowboard tele bindings.

So, that was the bad parts about low quality threaded inserts. But, the good thing is that even though their threads on the inserts I used are kind of shoddy, the bindings hold firmer to the ski than a binding mounted with wood screws. And, this firmness really helps to increase the confidence when the skiing gets technical... I have had bindings pull out in bad places before and watched as the ski tumbled to the bottom of the hill. And I am pretty confident that with inserts, this won't happen.
Easy
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Post by Easy »

@ Greg: So why did you use the low quality version? Is it just the price difference?
krp8128
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Post by krp8128 »

I've been toying with the idea of using adhesives to mount a plate to the ski.

My thought here is that the flexible adhesive bond will allow the ski to flex, even with a plate attached at the center.

Just keeping this in the back of my mind for now. I really need to make up some plate samples to mount on a piece of fiberglass for testing before I would ever try this on the slopes.
rockaukum
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Post by rockaukum »

I like the inserts. Permament attachment. I do use a dab of locktite to help keep the screw in place. I have heard of others that use a metal plate to aid in holding the mounting screws inplace. Of the one I have seen, they routered out a trough in the binding mounting area and inserted the metal during layup. Sounds very secure. Teleman sounds like he is going to try this on some AT ski mounts. I'm looking forward to the results on his set up.
ra
plywood
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Post by plywood »

thanks for the inputs!
i thought that it could be a problem to find screws for the inserts that fit the holes in the binding...

a few days ago i ripped my old K2 snowboard apart and tried to preserve the inserts. they`re really built for heavy duty! maybe i can post a picture, they were constructed really funny: some internal piece that holds the metric thread in it and this piece went through a thin disk made of an other metal.
the internal piece didn`t bond to the fibreglass, just the disk sticked to it...
plywood freeride industries - go ply, ride wood!
hafte
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Post by hafte »

I used inserts in the first two pair and found I had issues keeping them centered in the ski during the lay up/ pressing. I had the core over lap the base/edges just a bit and once the core was put down I couldn’t tell if it was centered over the base and edges. The inserts are straight along the long axis but shifted ~1/16”/1-2mm to the inside edged. I lucked out. Both skis shifted so that the bindings are closer to the inside edge. They seem to ski fine.

The screw inserts that Greg talks about would work fine. The only ones I have found so far are at home depot and are brass… I think. And I just don’t feel like trusting them. I’ll have to see if the nut & bolt bin have some in SS. I could go for that. I think they would be too long for a snow board. You would only get them in so far and have to grind off the rest.

BTW, if you are using hammerhead bindings they say NOT to use lock tight. It will eat the plastic. I believe I read this on ttips.com

Hafte
Idris
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Post by Idris »

To avoid this problem. Super glue 2 of your inserts to the base before layup. Of course you have to cut holes in your glass to accommodate them.

This is how many indie snowboard makers lineup their cores (also a few ski makers I hear)
hafte wrote:I used inserts in the first two pair and found I had issues keeping them centered in the ski during the lay up/ pressing. I had the core over lap the base/edges just a bit and once the core was put down I couldn’t tell if it was centered over the base and edges. The inserts are straight along the long axis but shifted ~1/16”/1-2mm to the inside edged. I lucked out. Both skis shifted so that the bindings are closer to the inside edge. They seem to ski fine.



Hafte
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rockaukum
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Post by rockaukum »

While talking to the shop that will be doing the base grind on my latest skis, his concern was during the grinding that he has had issues with the inserts releasing from the base. His thought was that all the inserts were attached (glued) to the base material during layup and wuold release and therefor float(?)or pull up. I also have heard that while tightening an insert that was glued to the base may pull up the insert and leave a dimpled base? Anyone here have first hand experience on this?
I learned from another maker to use a little plastic spacer for alignment. I tried these and they worked great. No slip, slide or anything. The spacer is used on electronic boards to space them off of the case. I got 100 for about $5. through McMaster Carr.
ra
plywood
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Post by plywood »

you bring up something i completely forgot:
i have no experience with inserts directly glued to the base material, but here s what i noticed on all my snowboards: i normally screwed on the base plate of the binding as hard as i could because otherwise the screws began to loose after just a few runs. this just caused some core material or whatever to "collapse" a little and you could feel that the base wasn`t even anymore. the spots on the base where the inserts where underneath sunk a little in.
and i think it`s not just because of me tightening the screws really hard, it`s more a general problem i suppose...maybe on a snowboard the inserts get a bigger load than they would get on a ski because of the different/bigger leverage, caused by the wide board and the binding plates etc.
plywood freeride industries - go ply, ride wood!
MartinJern
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Post by MartinJern »

I know what u mean with the dimples in the base but i also had the oposite problem. I used old inserts from a trashed board and to avoid getting epoxy in the threds i filled them with wax, when i mounted the bindings u could see big convexitys on the base. i dont think i got all the wax out before i mounted the bindings and to much pressure in the insert caused a dent in the plate at the bottom. Im not using secondhand inserts anymore its not worth the trouble with wax when new ones are less then 1eur/piece..
Baumnog
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Post by Baumnog »

Another technique to keep you core centered is using small finish nails on the sides of the cores.

During dry lay-up align the core then set small nails on the sides in a couple places. Keep the height of the nails lower than the top sheet to reduce puncturing the bladder.

Since the core is slightly larger than the base it shouldn't get in the way.

This way you can get fiberglass under the core.

To minimize dimples where the inserts are located make sure to have an accurate depth when you countersink them.

Hope that helps.
Greg
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Post by Greg »

Easy wrote:@ Greg: So why did you use the low quality version? Is it just the price difference?
The first time around it was because of the price, and not knowing any better about the quality issues. The second time around it was because I figured that I would only need to mount the bindings once, so the quality wasn't so much of an issue.
shralpster
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Post by shralpster »

I just found this site and I'm totally gung ho to build some skis. I was thinking about inserts from a quantity of bindings perspective. As my quiver grows, I'd like to have a couple quality bindings, perhaps one randonee, and be able to switch them on skis without causing damage. Will the quality inserts you're talking about allow for convenient swapping of bindings? If that isn't a benefit, I'd probably just try my hands at screwing into the core first and see how well they hold up.
Idris
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Post by Idris »

shralpster wrote:I just found this site and I'm totally gung ho to build some skis. I was thinking about inserts from a quantity of bindings perspective. As my quiver grows, I'd like to have a couple quality bindings, perhaps one randonee, and be able to switch them on skis without causing damage. Will the quality inserts you're talking about allow for convenient swapping of bindings? If that isn't a benefit, I'd probably just try my hands at screwing into the core first and see how well they hold up.
Yup, this would work for swapping bindings. It is something I should put some more effort into as I am forever screwing and unscrewing bindings.
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