Field repair of pulled bindings

AC, are you certain R:EX's have a metal binding plate?

Big Steve, I'm with you on the construction of REX/TMX skis as well. I've owned several pair and never saw any evidence of metal in the topsheet.

No data to support my case, and Zeno's pullout results seem a little inconclusive in supporting tapping, but I still think more surface contact between screw and hole plus less outward stress on the material around the hole plus a good slow-set epoxy is a good idea. I do it on any holes I drill in skis myself.

As for pullout insurance, after seeing Ron J's "Mr. Grip" a few years ago, I carry pre-cut small strips of it that will fit a screwhole (don't know how you'd cut this on a tour, as you need tin snips), plus about 8 Dynafit screws and a "real" #3 PoziDrive bit ground down to fit a Skeletool. Haven't had to use it in the field yet, but I enlarged the holes in an old alpine ski once and they seemed to work well with original Salomon screws.

FWIW: Due to the fact that slow cure epoxy has lost shelf space in my local big box store to 1 minute epoxy and general lazyness on my part I've mounted several sets of skis in the last few years using polyureathane glue (e.g. Gorillia). It is significantly simpler to work with than epoxy -- no mixing -- just a paper cup to dip the screws in water before screwing them in. So far it has worked without problems. The packaging claims "waterproof" -- which isn't a claim made on many epoxies. I've seen no loosening so far. The first mount I did with polyureathane was a little messy -- I used generous amounts and found that the glue expands quite a bit while curing and this left small mountains of glue oozing out around the screws. I applied a lighter touch on subsequent mounts with less sloppy results -- but I like the fact that the glue expands to fill up any gaps in the screw holes.

Polyureathane is of little use in a field repair kit as curing requires warm temps and at least 12 hours.

Of the easy to find in the store epoxies -- I've had good results with J.B.Weld -- provided I also have some tooth picks to work a good amount of epoxy deep into the screw holes -- J.B.Weld is so thick that without care it is possible to place too little glue in the screw hole.

I'd be concerned that PU glue might expand too much and crack the core. Also, I don't like the ideas of bubbles in my glue.

JB Weld is very viscous and thus does not percolate into the ski core. I prefer a low viscosity flexible epoxy which soaks into the ski core, thus forming a resin plug around the screw and spreading the load over a larger core cross section.

Good to see zeno contributing here. Maybe he can provide some links to his pullout tests.

Great stuff here y'all, thanks.

I do the same as Big steve -- 72 hour epoxy and a warm environment (I used a heat lamp when mounting my last set of inserts) to really soak into the core and get good saturation. Haven't had any pull-outs since.

AC, are you certain R:EX's have a metal binding plate?  I thought they were Texalium caps over foam.  I've mounted several R:EX and TMX and never noticed any metal (other than the microscopically thin Al film on the Texalium).  The Kongur is the same ski with an Mg alloy cap.  Anyway, I've never seen a ripout on any of those skis.

No, not sure.  The R:EX was the alpine version of the T:MX; I was looking for the latter as a telemark ski; my local shop had the R:EX and they told me it was slightly heavier (and I checked the weights at the time, it was heavier) and stiffer than the other two because of metal in/under the topsheet.  Since I always overloaded the easy flexing tele skis (and had been on alpine touring and alpine for telemarking for a while), I went ahead and bought the R:EX; I was advised to get the 184 cm since it was so stiff and the 191 would be too stiff.  I wish I had gotten the 191.

A few things.... First, I'm a cabinetmaker. I use glues and fasteners every day. I don't sit in an office on the phone ordering them....

The goal should always be a bulletproof mount to avoid field repairs. I use a few tricks to avoid mounting failures in the field. I do mount bindings for friends and never had a mount failure so far. I have yet to mount a dynafit binding because all my friends tele, but these seem to be the mount most people are concerned about, relating to mount failure.

Gorilla glue is crap. It has adhesive and sealant properties, but very poor void filling strength. Eurathane is essentially rubber and will not fill voids with a structurally strong material. If your ski core is a dense wood, and you counterbore with the proper sized drill bit before driving the screw, gorilla glue is fine as a sealant. I still wouldn't use it myself for other reasons I will state below...

If a ski's core is reasonably dense enough for good screw hold, most failures are not a result of upward force on the screw ripping the screw threads out. More often, I believe that lateral force from the binding on the shank of the screws gradually widen the hole in the ski which leads to eventual failure. One of the things to do if you see your binding is lose, is remove the binding and inspect the holes. If they are ovalized, then lateral force is being applied to the screws and just tightening the screws is not going to fix the problem.

I would do a few things carefully if I thought I had a failure prone ski/binding combination like a 4 screw tele-binding mount or a dynafit toe.

I would dry mount the binding first and unmount it to remove the volcano'd ski material that rises up when the screw threads into the ski core. Removing the volcanos allows the binding to have a greater area of binding contact under pressure with the ski.

I would use epoxy or glass resin in the screw holes to solidly fill any voids around the screws and soak into the core of the ski.

I also paint a layer of resin on the ski where the binding mounts, so the binding is bedded in a contoured recess that will bond with the ski's surface. Once this contoured resin is bonded to the ski, it captures the binding latterally and shares the lateral forces on the shank of the screws and helps prevents ovalizing the screw holes.

Mostly, I don't need to do this kind of mount for NTN since it's a widely spaced 6 screw base plate mount, but I would do it for BD 01's which are a 4 hole mount and capable of being very active. (using excessive binding leverage to drive force into a ski puts a greater load on the mount)

It seems like the dynafit toe has a narrow spaced screw pattern. I would think it would be a candidate for a carefully done bulletproof mounting also.

I liked lowell's prebent hose clamps as a field repair. I would probably take a short length of 1/4"  dowel and a pocket knife too. Field cut the dowel and tap it in the hole, then turn the screw into the dowel to get some pressure on the screw so it doesn't pop out, then use the hose clamp to lock it down. I could see that holding for a while if the skier skied cautiously...

I supose I sound like a pompus, know it all posting this.... maybe it will be helpful to some people and I won't seem like an ass for naught...