:: View topic - Twizz 2012/2013

Finally finished my first pair of the season, so it's time for my journal!

For those who aren't regulars, this past spring I designed and built a CNC router from scratch. I've done a few things with it since then, but up until now no ski stuff.

This is the first pair of skis made using the CNC router, and coincidentally the first pair of skis I've made for someone else! I've helped one person in the past make skis for himself, but this time I made the skis, and am handing them off to... my wife!

(we got married 3 weeks ago)

She is an ok skier on the groomers, but has had virtually no time in powder. I decided I'm changing that this year, so I made her some powder boards.

I give you - the Pinky Sticks! I took my powder skis, the Piggy Sticks, made them a little narrower at the tip and tail, and a lot more sidecut. Same length. I used the same mold, which is flat with a lot of early rise, but I heated from the bottom instead of the top. My piggies are entirely reverse camber, where as the Pinkies came out with just a TINY bit of camber under foot, which will be good for her.

The topsheets are sublimated nylon from Miller Studios. I can't say enough good things about the quality they put out, and their excellent customer service even for one-off hobbyists like me.

Dimensions are 160cm length, 145/120/135 (I think... something close to that anyways, I don't have the exact numbers in front of me)

His and hers!

Camber comparison. You'll notice the tiny amount of camber on the pinkies, and slightly less early-rise.

Gratuitous colorful lotus inclusion

Some notes on this pair:

Bases need more grinding, they are just slightly convex, but I think I can grind them flat.

They came out slightly longer than the Piggies, wtf? Not sure how I managed that, supposed to be 160cm, but whatever.

I got a little ugly wrinkling in the topsheet at the tips (see the Stumpysticks picture above). The picture makes it look worse than it is, but its still there.

I tried something new for sidewalls... I had a 2" wide slab of pink sidewall, I profiled it on the CNC and then ripped it into four sidewalls. I tacked it too the cores at the center with some superglue and then just did the layup like that. Turned out good, nice bonding with no delam anywhere, but in one spot the sidewall got pushed away from the core a little too much, enough that cutting off the flashing removed all sidewall in about a 2" long area. In the future I will do more superglue tacking along the entire length, similar to how most of us do edges, rather than just the center. The tips were stapled to the tip spacers so they were held in there fine.

While I'm not much faster with the CNC now, since I spend more time messing around on the computer, and getting things aligned and clamped and tested on the router than I did just cutting things by hand, the accuracy and general quality went up by many orders of magnitude. I used to have a motto "don't worry, it'll fill with epoxy". Tiny gaps between the edges and the base for instance were common place on my skis, hard to see on the finished ski, but there none the less. Now everything fits together TIGHT with no gaps anywhere.

If I can just figure out how to stop the top sheet tip/tail wrinkles, I'd say I'm ready to start selling these bad boys.

Congrats and great job on the skis, they look great.

Next up is some new powder skis for Kevin (KevyWevy... who never comes on here anymore). We CNC'd the cores today and epoxied on the sidewalls. Should have those pressed in a couple of weeks. I've also got another pair in the works for myself that will be some sort of park/spring/rainy day ski I guess. I'm running out of types of skis I need, so at this point I'm just building for the sake of building and trying to come up with snow conditions to justify them...

Awesome man, I need to make some his / hers skis to continue the gf's evolution. She's ok on groomers now but we've got a fair way still to go before I can ski with her all day before starting to get twitchy.

Great looking skis Twizz, are you designing your graphics in rgb color wheel? If so how are you converting to cmyk for printing?

Depending on what art software you are using you can just go up into the settings and change the color profile. For the most part it will be "similar" though some colors (namely brighter colors) will change slightly. But you can tweak it after the color profile change.

^^^^This.

I do everything in Photoshop and Illustrator, and its just one click to change to CMYK.

A few more photos

Profiling the cores, I profiled one piece of bamboo wide enough for both cores, and cut the shape after.

Sidewall slab profiled

Bases cut with homemade drag knife

So friggen jealous of that CNC twizz

also, if you wipe your equipment down with bounce dryer sheets it'll help keep foam/plastic bits from stickin to your gantry

Nice skis and the CNC is not too shabby either! I too am running out of reasons to make skis for myself, with the exception that more is better :-)

The skis look super cool! You will have a happy wife for a long time Twizzstyle

show us that diy dragknife pleeeeaaase!

great job on the skis!

about the wrinkles in the topsheet: are you using parchment paper on top of the ski? if so, i found that attaching it to the aluminum with spray adhesive helps with that. you can leave the parchment on there for a couple of pressings as long as it doesn't get damaged.

Dryer sheets, seriously??? I'll have to give that a shot! That's awesome!

I also realized that my dust collector was clogged, so it was hardly sucking... once I cleared that it did a much better job of keeping stuff clean.

I'll take some pictures of my drag knife tonight for you Chris. It's just an $8 carbide drill blank from McMaster that I ground into a knife-like shape, and I just leave the router off and let it free-caster... seems to be doing a pretty great job, although I think it could probably be sharper, and there's probably a better shape for the blade. I just winged it.

I am using parchment paper on the top, I'll try out the spray glue on the cassette for the next ski, but do you think that's really causing the wrinkles in the top? They seem like big wrinkles to just be caused by the parchment paper... I didn't really notice if the parchment was wrinkled there or not, I'm always too excited pulling skis out. It's like christmas and I rip into everything as fast as I can!

Ditch the parchment paper on the top aluminium layer Twizz

Good release wax and by the time you put the big rectangle of topsheet on there you hardly ever get any epoxy on the top aluminium layer anyway (and any that gets on there is peripheral to where the actual ski is).

I agree w/ Falls, I used parchment paper before but a good release wax works excellent. I use Butchers paste floor wax. It's available at most hardware stores and online. You want a wax with carnauba wax in it. If epoxy does get on the AL it pops cleanly off.

Ok thanks guys. I've got good release wax (partall from Fiberlay), I just use the parchment for extra insurance. But you're absolutely right, nothing gets on top anyways.

So... ~7 years ago or so, before I worked at Boeing, when I was still in school, I used to go to the Boeing surplus store all the time and buy random crap. One time I bought a slab of nomex aerospace-grade honeycomb for cheap. It sat around for years with no project with a good use for it, and went mostly forgotten.

Until now... I noticed the honeycomb sitting on a shelf buried under some stuff in my shop.

This is going to be awesome. More to come in the next few days

Twiz- I heard the Boeing surplus closed u know if thats true? I have always wanted to go. OH... and when are they going to get some good engines on that plane of yours?

Yes the store closed a few years ago, it was pretty sad. They still have an online surplus deal with auctions, much like ebay. But it doesn't have the small stuff that made the store so much fun (like drill bits and end mills by the pound, cheap!)

https://active.boeing.com/assocproducts/surplus/Index.cfm

No comment on the engines

Thats a production issue, I only deal with the experimental airplanes, once we certify them it's someone else's problem

So for the skis, here is what I am planning...

I am going to make two pairs of mostly identical skis (identical in shape/size). One pair will be my normal processes, with a solid bamboo core and triax fiberglass top and bottom.

For the second pair I am going to cut out most of the core, leaving just a thin edge on the outside to glue the sidewalls to, and two bits for the binding inserts. All of the area I'm removing will be replaced with the honeycomb, and then the bamboo and honeycomb will be profiled on the CNC at the same time.

I'm then going to sheet the top and the bottom of the bamboo/honeycomb core with some bamboo veneer I have. This is just to keep the honeycomb from filling with epoxy during the layup. Then it's just a normal layup.

Since I'm removing so much bamboo, I'm losing a lot of stiffness. I'm trying to figure out if I want to make that up with a thicker core, additional fiberglass, or just some uni carbon. Doing some math, it looks like increasing the middle of my core from 12mm to 14.5mm, all else the same, will give me just about the exact same stiffness. That might be the route I go, adding any more composites just adds weight.

My only concern is the veneer adhesion to the honeycomb. I'm worried about having it come apart after landing on the tails hard (I had that happen with some horizontal grain bamboo in a pair once). I'm not sure if there is really any way around that though... you're gluing onto the edge of the honeycomb, which is basically paper, so there's hardly any surface area for a good mechanical bond.

sounds about time to get into the real shit.

metal that is.

.3mm 7XXX series material top and bottom.

If you realy want to experiment you could also use carbon triax instread of fibreglass (Braider.com sent me enough fabric fora pair of skis for free when I asked for details on their product...)

Twizz - I wonder the same about the bonding to honeycomb, since there is so little surface area. A cap construction would probably help keep it altogether. I wish I still had my very old Hexcel skis

chop chop, take a peak inside.

If you have access to some honeycomb core, you probably have access to some film adhesive. Why use the bamboo veneer when you can use the real thing? I would think it would bond to the honeycomb way better and simplify your math calculations.

I made a "test core" yesterday. Just a single bamboo flooring board (~4" wide). I had the CNC cut out 3 large areas, leaving two small areas near the middle for the binding inserts.

I cut out some honeycomb, put it in those holes, then epoxied the whole thing to some bamboo veneer (using supersap). After it cured, I stuck it back in the CNC and cut the profile. This worked ok, but at the tips where it was down to 2mm some of the honeycomb ripped out.

After profiling I epoxied another layer of veneer on the top. It's cool, cause it just looks like a solid piece of bamboo, but it weighs hardly anything. BUT, just a little bit of flexing, and you can hear the bond breaking all over the place, and the veneer starts getting lots of ripples. Just what I feared. Back to the drawing board - maybe foam would be easier than honeycomb

Pics or it didn't happen!

Who let you back on this forum??? I'm a moderator now, Ima ban your ass (I don't think I can ban people)

What's next, you're going to be posting on Newschoolers??

brb

Twizz--are you bonding the honeycomb directly to the core at all? Or, are you just bonding it to the veneer and then the veneer to the core? If you wrapped the entire honeycomb piece in a film adhesive before you inserted it into the core you would gain a lot more contact area for bonding. If I understand what you are currently doing correctly, the "walls" of the honeycomb aren't bonding to anything.

That's correct the walls aren't bonded to anything. I'll get some pictures up later today.

The delam happens on the top and bottom faces of the honeycomb

I thought of using foam in the honeycomb so you'd have a surface to bond too, but then that defeats the purpose (would make quite the mess as well).

Maybe try a core cutout in the tips like Kastle does on their skiis, then the honeycomb throughout the rest of the ski. Just a thought...

Found this. I did not read it all but a quick read of the abstract made it look promising. Should be right up your ally.

http://www.in-tec.com/news/wp.pdf

Wow thanks Vinman, that was a great read.

One of the biggest things I took from it was the required surface finish of the honeycomb. I cut my honeycomb into slabs on the bandsaw which left a very fuzzy surface. I thought the fuzzies would be great for soaking up resin and forming a good bond. Turns out it's actually the opposite, a fuzzy surface gives you the worst bond with honeycomb.

This said to wet sand the surface with 320 grit to have a perfectly clean face on the honeycomb, and that will give you the best bond. Interesting!

Pretty much the same as with regular wood, a planed surface is better for bonding than a sanded surface. I hope it helps. Good luck, keep us informed.

As promised, some photos of my honeycomb shenanigans last weekend.

The slab I've had sitting around for years

Sliced into 15mm thick slabs

CNC'd out some areas to put the honeycomb in

After profiling. Notice the bits that were ripped out at the tips

You can see the fuzzy finish that I thought was goodness, but have now learned is badness for bonding.

And just for fun, I laid out all of my Piggy Sticks from the past few years. Another new version is currently in the works with a very new shape to me, should be pressed in a couple of weeks.

I also mounted the bindings on the "Pinky Sticks" (the skis I made for my wife). Homemade skis always look SO much more serious with bindings mounted.

Just needs to snow!!!

Twiz... are you still doing the same angle on your tip spacers (as on the original piggysticks) or have you moved on to straight across cut?

I can see where your honeycomb deteriorated in the tip and tail with profiling.

I think smaller sections of honeycomb cutout of your core might work.

Is it possible to loose the frizzies?

From what I got from that article I would try smaller areas and forgo the veneer just glass prepreg* for the next trial.

*wetout your triax on a separate table just before layup.

The top sheet pattern is definitely looking good and becoming your trademark!

sam

No I just do straight across on all my tip spacers, I only did the angle on the first few pairs.

That article talked about wetsanding with 320 grit to get rid of the fuzzies, I'll give that a try.

My only reason for doing the veneer is I worry about the honeycomb just filling with epoxy (rather than the epoxy squeezing out like normal) and the skis becoming super heavy. What I should really do is get some of those pre-cured pre-tensions fiberglass sheets.

Beehive!

Have you guys seen the foam core Kelvin has for sale on blank slate now?

At $38 per core it's a bit pricey, but looks like nice stuff.

http://www.blankslateskis.com/foam-core-fiberglass-reinforced-140mm-x-15mm-x-1854mm/

Templates for the two new pairs we're doing.

(I'm still cutting out the bases with the drag knife on the CNC, but I still like to use the template for bending the edges, and attaching the edges)

You're just showing off now!

Hi

Try page 12 and pop them in the CNC. No furry bits!!

https://www.onsrud.com/files/pdf/OC-12-MillingDrillingToolCatalog.pdf

C.

Nice templates. I see you even have the bump out for the 3/4 wrap, nice touch.

Hey, if I've got the CNC, I might as well take advantage in every way I can!

I should have cut my piggy into the templates too!

Picked up a bunch of bamboo today since I was all out, and I have a friend from high school who is a graphic designer coming up with some graphics for me (I told him I didn't have anything in mind for what I wanted... my only requirement was that it be "epic"... I have no idea what I'm in for). I'm hoping if he can get me some graphics in the next week or so, then I should be able to get everything ready to press both pairs (the honeycomb, and the normal ones) in a few weeks time. If I can't figure out a good bonding process for the honeycomb, I may just cave and fork over the money for a couple of the foam cores from BlankSlate.

I also visited K2 today, since it's just down the street from my work. I hadn't been inside the new place since they moved from Vashon, and hadn't visited since I worked there. The new place is amazing, and they're doing some really cool stuff. I really miss working there

Longtime lurker, but am really intrigued by the honeycomb. I saw that Salomon added the honeycomb to their tips and tails in the Rocker 2 last season.

I think they've added the honeycomb to replace the tip/tail spacers to provide more strength through the tip without adding too much weight. Not sure what they're doing to prevent too much epoxy being trapped inside though.

Just thinking about using honeycomb in the core that way would make me think those thin strips of bamboo on the outside of the honeycomb would be subject to more pressure during a flex. Of course I'm probably completely off, but just thinking as I type.

when hearing the word "epic" Chuck Norris comes to mind

Ha! When I told my buddy "epic" he said something along the lines of "you mean like Vikings with light sabers riding raptors?" I think I'm in good hands

I HAD THOSE TOYS AS A CHILD!!!!!!!!

In fact, my parents still have the t-rex with the thing that attaches to its back. My nephew has been playing with it. I can't remember the name of the toys...

Ah yes, Dino Riders!!!

Hey twizz...

I'm lucky enough to have a fair amount of both honeycomb and last-a-foam lying around to play with. I remember being told that the honeycomb was tougher to machine, so this week I started playing around a bit with the last-a-foam with some "spare time" (hahaha).

Anyhow, I found the last-a-foam equally difficult to bond to. I'm whipping up some mixed material cores for a non-lift service hiker prototype pair. I'll throw some photos up later in the week.

I'll check with my priceless resource about bonding issues with honeycomb and let you know what he has to offer.

Killer looking product by the way, congrats again on the CNC build too.

Awesome, let me know what you learn!

Would love to see what you're experimenting with too!

Change of plans on the honeycomb... I'm too worried about bonding issues.

Instead I ordered some of the foam cores from BlankSlate, and I'll give those a shot. I'll save the honeycomb for another day.

In the meantime, I've got the normal bamboo cores profiled and ready to go (profiled on the CNC with the sidewalls already attached - no issues whatsoever!!!).

Just waiting on the graphics now from my friend, I've seen a rough sketch... and it's pretty awesome!

How about honeycomb filled with foam?

What about machining the honeycomb pattern, maybe a little larger, into your core? So basically the spots that you have cut out for the honeycomb. After that is all cut out, wrap the core with veneer top and bottom to keep epoxy out. A core with hollow spots, more or less.

Make sense?

One of my custom skwals has a really funky core layup that is wrapped in veneer and carbon...i gotta take some pics...really funky layup compared to what is the 'norm'.