Perennial Skis

Document your personal work here. Show photos, movies, and share your secrets.

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Jonsn
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Joined: Sat Jan 02, 2016 1:28 pm
Location: Munich & Bregenzerwald/Austria

Perennial Skis

Post by Jonsn » Mon Feb 06, 2017 3:00 pm

After reading and building for the fourth season I finally made to post some pictures on this great forum.

From the second season I was quite happy with the results and today I still ski almost all of the skis below today. All are built with wooden sidewalls and with either ash or smoked oak veneer as topsheet.

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Currently I am mostly interested in building lightweight touring skis. I started with a full cap construction for the first two builds but had problems with proper core alignment. To solve that problem I went for a semi-cap construction for the next two builds. I made cores with poured sidewalls (6 mm under the bindings and 2 mm for the rest of the ski) and after profiling I handshaped the top of the core (somehow like Fischer or Scott is doing for their touring skis).
All turned out being very lightweight (well, the white skis were too light :? )

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For this season I was fortunate enough to get acces to a proper wood workshop with a CNC machine and a laser cutter. Made the process more complicated in the first place, but once everything is dialed in, I enjoy using these bigger machines.

I built several pairs of touring skis very similiar to Akiwi was recently positng. The core has maple sidewalls under the bindings and tapers towards the tip and tail. In that area I place laser-cut 2.5 mm balsa pieces.

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1030 g/ski are so easy on the hike up, while the Fritschi Vipec I mounted doesn't add much more. I don't like the feeling of the full carbon laminate though, especially in harder snow conditions. For the next ski, I want to add some dampening material, maybe flax or go back to a glassfibre laminate.

burnside
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Post by burnside » Mon Feb 06, 2017 3:37 pm

Wow! Beautiful skis!

Is that a wood veneer topsheet on the 3D/balsa core skis? How did you get it to conform so well to the core?

Jonsn
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Joined: Sat Jan 02, 2016 1:28 pm
Location: Munich & Bregenzerwald/Austria

Post by Jonsn » Mon Feb 06, 2017 4:02 pm

Thank you burnside!

Yes, it is a .6 mm oak veneer. I use a vacuum press. Once the skis are in the bag, I push the veneer in all the corners by hand. It slightly cracks during that, but the cracks fill up with epoxy and are hardly visible after pressing.

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Akiwi
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Location: Olching (Near Munich) Germany

Post by Akiwi » Mon Feb 06, 2017 10:39 pm

I Agree, Beautiful looking skis.. Especially the last ones.
I took my new ones out of the press last night. I hope they hold longer than my last ones.
Holy Cow.. 1030 per ski is very light!
I am nobody. Nobody's perfect, so I must be perfect.

pmg
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Location: Sonthofen

Post by pmg » Tue Feb 07, 2017 1:46 pm

Nice nice! 1030g really is very light, what are the dimensions of the skis?

Jonsn
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Joined: Sat Jan 02, 2016 1:28 pm
Location: Munich & Bregenzerwald/Austria

Post by Jonsn » Tue Feb 07, 2017 2:39 pm

Thank you guys!

The skis have a length of 170 cm and widths of 118-86-110.
Not a real powder width but they float pretty well though and I do not like to skin on much wider skis.

I am working on a full powder ski with a length of 180 cm and widths of 154-125-147 with the same balsa construction method and 750 g/m^2 triax glass. Let's see how heavy/light they are...

Hannes
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Post by Hannes » Wed Feb 08, 2017 7:31 am

Your 3d design looks great.

Jonsn
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Post by Jonsn » Tue Feb 28, 2017 2:50 pm

I've finished a pair of GS skis and took them for a test ride yesterday.
They are 180 cm long with widths of 98-70-116, R=19m
Ash core, maple sidewalls, aluminium tail spacers, 750 g/m^2 triax glass and a smoked oak topsheet with laser cut ash inlays and an epoxy topcoat.

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I am amazed how clean the inlays turned out. Unfortunately I got a lot of bubbles in the epoxy topcoat. Maybe I will sand it down and reapply the topcoat. I also need to pay more attention to get the topsheet centered.

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It is also my first pair of skis that I am totally satisfied with the edgefit and the flatness of the base. After a base grind it the base has a nice structure and there are no gaps visible between edge and base.

The aluminium tail spacers are made from a 4 mm * 50 mm bar. I milled a 1.2 mm * 40 mm pocket in one edge. I think they give a sleek look to the skis and are helpful when knocking of snow...
Next time I won't put an edge under the aluminium, because I hade some bonding issues on one ski.

Regarding the performance I am a bit disappointed. The overall flex is very soft, especially in the tail. Torsional rigidity could also be better. Also the camber is too flat and I put a wider radius in the nose, that way the tip feels very loose and overall edge grip isn't really satisfying on harder conditions. It is a nice ski in soft afternoon conditions though.

satch
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Post by satch » Wed Mar 01, 2017 4:49 am

Very ice looking skis. Bummer that one of the top Sheets is out of Position. You'll be able to fix the bubbles in your top coat. But the tops will get scratches no matter what if you ski them and make them a bit more ugly.
I hope you treated the aluminum somehow. I tried a similar Thing and the bonding of the aluminum and the epoxy failed pretty soon. All I did was sand the surface with coarse sandpaper.
What is your core thickness? In my opinion the 750g/m² Glass is OK for a ski with 100mm+ under the bindings but not really stiff...

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chrismp
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Post by chrismp » Wed Mar 01, 2017 6:15 am

Try passing a torch over the epoxy topcoat. This usually pops any bubbles.

As for the aluminium bonding, satch is right. You need to chemically treat the aluminium in order for it to bond with epoxy (here's just one example that should yield good results: http://www.epotek.com/site/files/Techti ... _to_AL.pdf). In addition to proper surface preparation I would also add a layer of VDS rubber above and below the aluminium as it has different thermal expansion than the surrounding materials and also promotes bonding.

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Akiwi
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Location: Olching (Near Munich) Germany

Post by Akiwi » Wed Mar 01, 2017 6:44 am

Love the look of the lasercut veneer.
Maybe I can help you with your finishing.
I am nobody. Nobody's perfect, so I must be perfect.

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vinman
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Post by vinman » Wed Mar 01, 2017 7:53 am

Things I've learned about using an epoxy top over wood veneer after about 80 pair or so.

Skim coat your veneer with epoxy during pressing to get a consistent color and improve durability.

Epoxy your inlays on the backside of the topsheet to decrease the chance of voids. Don't use too much paper tape on your inlays for the same reason.

Use 60 grit sand paper to structure the epoxy skim coat before applying your top coat to improve adhesion.

Wipe with a light solvent to get rid of any fingerprints, oils etc. and Be sure you clean the top of the ski very well with a damp cloth to remove dust from the flashing and structuring process.

Use a heat gun to pop your bubbles instead of a torch. I found the torch, if too hot, would give a weird patterned finish.

Be sure you cure at a warm enough temp in a humidity controlled room to prevent epoxy blush.

Be sure your brush is clean, free of dust, debris and loose bristles.

Gently re-brush and heat gun areas that begins to bubble or orange peel to get things smooth. Repeat as needed until the epoxy begins to gel. Use the heat gun on spots that you rebrush to smooth things out as needed.

Always Keep the heat gun moving to avoid overheating the epoxy.

Don't apply it too thick as it can crack, especially at the base of the tip where it tends to pool a little.
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pmg
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Post by pmg » Wed Mar 01, 2017 11:04 am

Nice looking skis! Built GS skis as well and waiting to test them!
IMO glass fibre is a bit too soft for a GS ski where egde grip is the main goal. Or you'd have to use a lot of glass, e.g. 1050g/m² triax. In mine, I used 450g/m² carbon and in addition 120g/m² uni flax to dampen the ski. Will tell you how it turns out, feels pretty stiff!

Jonsn
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Joined: Sat Jan 02, 2016 1:28 pm
Location: Munich & Bregenzerwald/Austria

Post by Jonsn » Wed Mar 01, 2017 1:49 pm

Thank you for all the replies.

I did degrease, sand and degrease the aluminium just before layup. I have not chemically treated it. I will see how long the bond lasts, otherwise I will the try to acid etch next time.
I think the even bigger problem was, that that the aluminium is no bent during pressing. A slight curve in the mold easily created a gap between base and aluminium. I did not think about that carefully enough.

@satch: The core has a thickness of 11.3 mm over a length of 550mm around the boot center and tapers to 2.8 mm in the tip and tail.

@Akiwi: I can cut veneer for you if you like. I see you do not live very far away from my place

I see i have to take more care when applying the topcoat to get it free of bubbles. Thanks for all the advice...

For my last GS skis I added 300 g/m² biax carbon to the 750 g/m² triax glass. I ran out of carbon fibre this time, but it is definetly worth it. The old skis hold the edge much better...

I am looking forward how your GS skis perform pmg...

satch
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Post by satch » Wed Mar 01, 2017 10:39 pm

For my taste 11.3mm would make for a ski on the sloppy side even with 100mm under the bindings. Depends a bit on the cores.
I've only built one pair with similar dimensions so far. At a core thickness of 12mm i used 800g/m² Carbon quadrax on top and bottom laminate.

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