Twizz 2012/2013

twizzstyle · Post by **twizzstyle** » Mon Sep 17, 2012 11:40 am

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!

falls · Post by **falls** » Mon Sep 17, 2012 7:57 pm

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).

skidesmond · Post by **skidesmond** » Tue Sep 18, 2012 4:00 am

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.

twizzstyle · Post by **twizzstyle** » Tue Sep 18, 2012 7:31 am

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.

twizzstyle · Post by **twizzstyle** » Thu Sep 27, 2012 6:46 pm

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

Cornice · Post by **Cornice** » Thu Sep 27, 2012 8:30 pm

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?

twizzstyle · Post by **twizzstyle** » Thu Sep 27, 2012 9:53 pm

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 ... /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

twizzstyle · Post by **twizzstyle** » Thu Sep 27, 2012 10:01 pm

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.

MontuckyMadman · Post by **MontuckyMadman** » Fri Sep 28, 2012 12:02 am

sounds about time to get into the real shit.
metal that is.
.3mm 7XXX series material top and bottom.

ben_mtl · Post by **ben_mtl** » Fri Sep 28, 2012 3:49 am

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...)

skidesmond · Post by **skidesmond** » Fri Sep 28, 2012 4:30 am

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.

powderho · Post by **powderho** » Fri Sep 28, 2012 5:58 am

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.

twizzstyle · Post by **twizzstyle** » Sat Sep 29, 2012 8:11 am

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

KevyWevy · Post by **KevyWevy** » Sat Sep 29, 2012 6:29 pm

Pics or it didn't happen!

twizzstyle · Post by **twizzstyle** » Sat Sep 29, 2012 7:19 pm

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

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Twizz 2012/2013