Snowchasers

[telexis]

Hey Fellows,

So here I am, making my first pair of skis! Got all my material and now figuring out the last details... I thought about posting my CAD drawing out here, just in case I did a pretty obvious mistake! Please let me know!

So it is a 150-125-130 ski... Pintail design, kind of an hybrid between the BD Megawatt and the DPS Lotus 120. As you can see the minimum width of the ski is not exactly right at cord center, but about 20cm lower... I think this is how you come up with a pintail design and from the pictures of the Megawatt and the Lotus that seems to make sense.


They the layup... nothing fancy for the first time! The core will be 10.5-11mm at CC, extending 10cm in from of CC and 25 cm behind, tapering down to 2mm at the tip and tail. I will put a bunch of inserts in there, I had problems last year with my O1 pulling out of the ski...


Flat camber... 27cm rocker (maybe longer... like 40cm). Is 55mm enough in the front?


I laminated my core (half of it so that I can cut it on the table saw) this weekend and just plane the laminate this afternoon. Now I need to slice it, and join the two half before profiling them... looking good!

Thanks for any advices!

Alexis
--
http://snowchasers.blogspot.com/

[Wannabebuilder]

don't ferget the rubber!

[ben_mtl]

sounds promising, can't wait to see some pics !
How do you plan on bonding your sidewalls to the core ? I wanted to do that but my test was not so good so I kept with maple sidewalls...
Where did you get all the materials from ?

Good luck !
Benoit

[telexis]

The rubber is not on the drawing... but I got a roll of it and it will be on my skis!

I got all the material from skibuilders.com, the vacuum stuff from aircraftspruce.com and wood from a local retailer... I haven't started doing the sidewall bonding yet, but I am planning to do exactly as described on the website. My plan is to do one "test" ski, and then build a pair...

How are the maple sidewall surviving skiing?

Alexis

[rockaukum]

Very nice write up. Gives a very clear idea of the lay up. sounds like you have a good grasp on the whole process. Best of luck with the skis!
rockaukum

[ben_mtl]

How are the maple sidewall surviving skiing?

I don't know but I'll keep you posted about that as soon as the white gold starts falling.

[telexis]

So I made it! :-)

The mold... Flat camber, about 12in of tip rocker...


Glue a layer of 1/4in melamine on top of it... bad idea... super hard to bend (should have used 1/8in) and the melamine "bubble up" with the heat generated by the curing epoxy... will have to sand everything to reuse it!


Testing the inserts


Gluing the edges. Full edges... I had to heat treat the tip and tail to bend them... So much easier when heated! I used superglue accelerator... then no need for all those clamps!


That is something really wrong... the base doesn't match the template anymore. Was it cause when gluing the edges or the base just wrap?


Cutting fiberglass


Double taping the base on the mold


Epoxy mixing... I use the West System epoxy


Laying up everything


More pictures of the laying up on http://picasaweb.google.com/alexis.luss ... abrication# ... basically:
- base + edges
- VDS on the edges
- 22 oz triax fiberglass
- Poplar wood core (rear half with sidewalls, front half without), not laminated
- 22 oz triax fiberglass
- Top sheet (front third = nothing, middle third = tried dacron for peel ply, rear third = p-tex)

Bagging... reached about -12psi... cured during 36 hours with a heat blanket!


Finished product (2150g per ski... similar weight to the BD Megawatt or K2 pontoon):


Flexing it... kind of a soft ski. Core is 10.5mm underfoot, 2mm at the tip and tail...


Ok... that was a test ski and here is what I learned. If you have answer to any of these problems let me know!

- Ski is too soft... I am planning to add 1mm to the core to make it stiffer. This core was only poplar and wasn't laminated (just a 1x8in piece of wood). Will it be stiffer by laminated it? Will also have a mix of maple and poplar in the finished product
- I like the sidewall (even if it is heavy) and the p-tex topsheet. It seems really durable. I have some bonding problem between the sidewall and the fiber, but only in the section without the p-tex topsheet.
- Obviously the base wrapping is a problem... I am planning to leave the base on the template while I am gluing the edges. Hopefully that will solve that problem! Any other ideas?
- There is some delamination problem between the fiberglass and my woodcore. It doesn't seems too bad, but the color of the fiber is changing to a milky white when I bend the ski... a few idea from where it can come from:
- Not enough epoxy? Not so sure about that... I used about 700g of it for my ski. Should I use more?!?
- Air bubbles during the layup? I definitely seen some during the layup... tried to get rid of most of them, but maybe I left a few... How can I get rid of them?
- Heating the core evacuate some air during the curing... maybe! Next time won't start the heat until everything is hard. Might try to "dry" the core before doing the layup, it was really humid a few days before I did the layup so maybe there was humidity in there!
- I didn't spend a lot of time sanding the wood core after it came out of the planer... Could that be it?
- Anyone seen that?
- I would also been interested in how you clean up the sidewall... spent a lot of time with sandpaper... which is a pain in the ass. Was planning to use a router, but the edge was buried in epoxy!

Thanks for you advice. I had a great time doing that, but I want to make a good ski that will last all winter!!! :-)

Cheers!

Alexis

[ben_mtl]

To clean the sidewalls I usually just cut it with a jig saw (and lots of blades), following the metal edge. After that it's pretty fast to finish with sand paper to have all the edge exposed. Next step is bevelling with a router following the edge, many topics about this last step.

Nice work by the way !

[sammer]

nice work!

Yes, leave your bases attached to your template until you get edges on. this should help with warping
I bend my edges days before until they can just sit on the template with one clamp

I also label my template sides 1+2
then bend edges and label them 1+2 these get glued to the base that gets cut on sides 1 or 2. This way if my template is a banana then at least my finished skis are opposite bananas (hope this makes sense).
I'm beginning to believe the small bubbles under the top sheet are caused by the squeegee rubbing on the glass fabric (cavitation)
Next pair I'm planning on using my gloved hand to spread my epoxy

laminated will probably make it more consistent but not necessarily stiffer
thicker will definitely make it stiffer.

sand your core before layup. The planer will tend to make the wood shiny, almost waxy feeling. You'll get a better bond if its rougher.

I've been experimenting with my cheap electric blanket and found that set on 2 i can maintain a consistent 80f
after 8 hrs or so i ramp it up to 6 or 7, good for 150-170f and leave that for another 8 or so hours
I usually turn off my vacuum pump after 12 hrs or so
and leave the ski in the mold until its cool (saves the plastic top on my mold from warping)
I'm also using west with slow hardener

hope this all makes sense

***your results may vary***

sam

[telexis]

So I tried breaking my ski using the well known "Karhu technique"... just to see how solid it is! And made a video of it...



Basically everything hold well. It amplified the PE sidewall delamination problem in the rear of the ski and I also "crack" the middle of the ski cause the top layer of fiber is lacking some epoxy (fibers are buckling). It will be pretty easy to make sure that I have enough epoxy on the top layer on my next pair, but as I need to finish a pair in the next too weeks (school project), I will just get rid of the PE sidewall. No time to experiment with different flaming and sanding techniques... just want something that works! ;-)

Enjoy the video!

Alexis

[sammer]

That's awesome, I'm still laughing.
might have to try that with my failed ski. just to see how well it bonded.
I'm still not convinced that p-tex side walls are worth the effort.
we'll see how the pine sidewalls on my 186's hold up.
my latest core has maple sidewalls.
hope to get those pressed in the next week or two.

sam

[telexis]

Here we go... I have one pair in the bag, waiting for them to cure. I had a few problems during the layup (mostly with the scale working randomly... bad) but hopefully they will turn out great... here are a few pictures:

Maple and poplar core (this time it is 3mm at the tip and tail, 12mm underfoot... I am a heavy guy):


Planning the core, notice the inserts holes:


I CNC some p-tex pattern on the base. Although I think I can now reproduce the results easily, it required a lot of experimentation, was a pain in the ass and I don't think I will ever do it again... maybe if it turn out great! :-)


Babies are in the bag...


The shop was close due to Thanksgiving, so I had to work in the lab... The good news is that you can drink beer in the lab! :-)

[ben_mtl]

really nice and clean work !

just a couple questions : why did you put the vacuum plug sideways on one edge ? do you have something between your topsheet and the breather ?

[MontuckyMadman]

I'm sure you know that pros did away with this diecut base process because of problems. Sublimated or otherwise clear base with a graphic layer is a possibly easier way to make your design on the base.
they look awesome way to bang it out.

[knightsofnii]

many, many different ski/board models are still being built with diecuts.


i hope that the placement of your bag connector there doesnt cause any problems with capping. Looks like good stuff man!!