Field repair of pulled bindings

No doubt about it: some K2 cores have soft spots. I hit so many soft spots on my AP's (Coombas with tele inserts, but I Dynafitted them) that I helicoiled every hole in both skis. No kidding. I've mounted several other Coombas/AP's/Coombacks and hit soft spots on every ski, some more than others, installing between 2 and 9 (all) screw holes.

yikes.
I haven't used helicoil screws before. Is that something that could be done in the field with minimal gear or do you need some beefier equip to get those screws in?

Cautions abound about being very careful mounting Dynafit bindings to Dynafit inserts (see Wildsnow for no end of discussion). Lou Dawson is adamant that epoxy must be used to prevent water infiltration. Others have pointed out that not all expoxys are waterproof. The techs at Marmot told me they don't use epoxys or glues. Dynafit instructions say go to an approved Dynafit dealer but say nothing about using expoxys or glues. I used JB Weld (!) to install my Freerides on my R:EX (by mistake , but it turns out JB Weld produces a strong bond; I don't think it is waterproof). I mounted my Vertical STs on my Manaslus with 3-hr epoxy (but had not yet heard some aren't waterproof) and I paid extra special attention to not cranking down on the screws in the inserts. Lou suggests prethreading before going thru the binding and reaming out binding holes if they are too tight. I just ordered some binding glue from Tognar that is supposed to be waterproof.

My Dynafit skis all have some metal topsheet in the mounting area; my Atomic R:EX have a metal layer. I ripped tele bindings out of my Volkl Prestos three times despite have voile releases--they were foam core.

I think boots are getting bigger and stiffer and skiers are going further, higher, and coming down faster than ever in the backcountry. I think things can stressed to the extreme and get worn out quickly (I don't know because I go low and slow).

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.

I agree with Lou re tapping all ski cores, metal top sheet or not.  I think GregL is with me on that.  Tapping allows better penetration of epoxy into the core material  and helps one avoid overtorquing the screws.  zeno's pullout tests also seem to confirm that tapped holes are better (and also seems to favor epoxy).  I now use long set epoxy on all Dynafit mounts.

That's the EXACT ski and set-up that did it to me. I was skiing them with T1s and both tearouts (original mount and helicoil repair) were while skiing inbounds (second run and first run, respectively).

I changed up to Insanes with inserts and used an adapter between the deck and the 7TM binding with good success for a while. Have since moved on to the NTN on that ski with no problems, but the NTN mount (frame breakage aside) is pretty beefy.

Interesting.  I'm skiing them with Crispi CXPs - a much softer boot - and don't use the "power pin", keeping the binding less "active".  And besides, I ski like Tinkerbell 

-Dave

Let's say you don't have mr grip or epoxy with you . You do have your pocket knife /leatherman
And some source of wood or perhaps plastic maybe golf tees . Just whittle yourself some and plug the whole. Cut flush and drive the screw /screws in. 5 min epoxy even better. In effect a wedge anchor. Ski home.

I've had a pullout failure due to water intrusion too in the past. Also, I've forced lots of other failures with pullout tests that Big Steve referenced in order to learn more. 

A few tips on how to avoid a pullout failure:

1) Mount screws with liberal amounts of properly portioned slow set flexible marine epoxy. West Systems G-Flex is the best in my opinion since it has a compatible strength and stiffness for the application (conditions: freeze-thaw, cyclic loading, flexing ski, etc.). Available for $20 for probably 50+ mounts at West Marine.

2) Do not overtighten screws which will strip the screw thread to ski mechanical bond. It is easy to strip especially in soft (lightweight) wood cores and/or lightweight ski constructions.

3) Watch/check for loose screws. A loose screw means poor connection integrity and a pullout is the next step in the failure process. Go to point #1 and #2 above.


A few other points:

For some reason the need for sealing out water in our region is overlooked by many ski mounting professionals.

If epoxy is against ones religion, a flexible marine sealant will work better as a sealant in a ski application (lots of flex) than a brittle material like waterproof wood glue (e.g. Titebond).

Epoxy comes in many flavors - use a flexible marine version.

Removing epoxied screws is clean and easy. Epoxy has a powerful antidote, which is heat. I use a solder tip on any epoxied stuck screws (usually about 30% of them are “stuck”) and the screws come out like a hot knife through butter.

The advice to use waterproof wood glue (brittle), or no sealant, is really bad advice for our wet skiing environment. Perhaps in a cold and dry climate like Colorado no sealant works fine.

The West System syringes to apply epoxy into holes and/or onto screws and West System fillers to thicken the G-Flex have also worked very well in the garage.