Ski Builders Forum

I'm a big fan of the planer sled to profile my cores with one exception. The sidewalls keep blowing off and getting eaten. I've tried poly glue, and epoxy. Glue seems pretty good until I get to about 3-4mm thickness then it fails. Able to pull off the epoxied sidewall by hand with no effort. I also tried carpet taping the core to the sled to keep things in place and placed blocks at the ends of the sidewall so that's not the first thing hitting the cutter.

You guys that epoxy the sidewall on, what do you use? Same stuff you use for layup?

I'm thinking I should I bag it and build a better router setup. Seems like there would be more control over the process as a whole since the planer is pretty much no mercy.

I pre-bond a full sheet of sidewall to 6mm of hardwood using the same epoxy I use for layup. I stick it in my press and heat cure with about 10-15 psi.

I rip that into strips on the table saw. The strips get wood glued to a pre-shaped core.

I've used this method for more than 20 pair with only 1 sidewall getting ripped off. This was error on my part trying to get by with dull planer blades. YMMV with a router sled but I think it would work just as well as long as you take small passes and use sharp bits.

If you can rip your sidewall off by hand you're not prepping it right.

Are you flame treating before bonding? Is everything clean? Whatever you're doing isn't prepping the surface of the plastic for bonding, and presumably you're doing the same thing for the layup, which means your sidewalls may be prone to delaming in the finished skis! My bet is you're not flame treating, or not enough.

That said - even with a good bond, it was rare I would have an entirely successful profile with the planer. Probably the most frustrating part of ski building for me. I think they key is to make sure everything is held down as good as possible. Even the slightest lift will cause vibration, and then the blade will grab the sidewall and devour it.

What I do now with my CNC router would probably work well for a planer as well. I cover the bottom of the core blank with vinyl decal application tape. Masking tape would work well too. Then I use spray glue to glue it down to a board (your profile sled in your case). It can be a pain to peel it off when it's done, but it saves my sidewalls.

I started putting a dab of hot glue at the ends to hold things to the sled. Seemed to work well

Taking a piece out of the sidewall at 45 degrees to the blade can help.

Just an idea (that I haven't tried)
http://www.grainger.com/product/3M-Primer-2RUF7
prep the surface with that if flame isn't working for ya?

I'm building an improved router bridge. Should have some pics up in a few days. My last one was not well thought out although I liked the overall design. I also like the idea of faster "oh shit" reaction time.

That still won't address your comment that you can rip your sidewalls off by hand with no effort. Fix that before you change up your tools!

EW why don't you for now start doing wood sidewall this way you will eliminate the problem of gluing p-tex for now and concentrate on ironing out rest of a process. less potential problems..... better in my book

twizzstyle wrote:That still won't address your comment that you can rip your sidewalls off by hand with no effort. Fix that before you change up your tools!

I'm reasonably certain it was a prep issue. Didn't flame it or anything. I was fairly satisfied with the poly glue except when the core got thin through the planer.

I use a router bridge, and had some probs with sidewall failure. It was always at the end when I had a failure. I tried everything, finally tried west system G-flex.
Works every time. Kind of expensive but when you consider the amount of time involved with getting a core to that point, not so much.
Just sand with 80 grit, and flame. So far 0 failures.

EricW wrote:Didn't flame it or anything.

Dude, you've ALWAYS got to flame UHMWPE before bonding! You still may get ripped-off sidewalls in the planer, but it'll increase your chances big time. You shouldn't be able to rip it off by hand. I always use the same epoxy I use for my layup (entropy CPM), but do a good job of flaming before putting down any epoxy.

(you should flame your tip spacers and base material just prior to layup also)

When I cut away the sidewall to shape the tip/tail for the spacers they are about 2-3mm thick. Even then I can not pull the sidewall away from the wood. The wood flails before the epoxy bond does.

My process:
I abraded with an 80 grit drum sander on a drill. Abrade but don't make it hairy.

Pre-test with a water drop and observe the contact angle. Flame 2-4 passes, at ~1 ft/sec and retest. Continue flaming until the contact angle flattens out. I usually go 6-8 passes per sidewall/per side.


For tip spacer and bases I quickly reflame the whole surface area within 1 hr of layup.

I try to use hot glue for attaching sidewalls. It is not that easy to do due to the time to attaching ratio. But when the work is clean the result is good too. It is virtually impossible to rip sidewalls. Under the router bridge hot glue works good as well. The only thing is that there hasn't to be stick out parts of sidewalls, since router bit will pull out sidewall.

There is a test done by West System, it showed that claning it with alcohol prior layup will improve the bonding. They did several tests on multiple plastics, I tried to sum up all the learnings over time on this page, hopefully its usefull,

http://www.junksupply.com/flaming-and-s ... ller-ptex/

Cheers,
M