Norsk Alpine

[Jekul]

Well I've finally been able to upload some pictures and I'm slacking on some work to finally put a journal together.

I wanted to design and build a press that would be relatively easy to assemble/disassemble in case my dream of moving to Colorado is realized this summer. With that in mind I passed on any designs that required substantial welding. I also passed on designs requiring large pieces of steel AKA: I-beams/structural beams. In the end I chose to use Structural pallet rack. It came in appropriate 8' lengths, and after some stress analysis I was able to design a safe press.

All of the connections are bolted together, and the heaviest piece is less than 40 pounds. Pictures are below, unfortunately as soon as it was built the top level became overflow storage in the garage.




I also chose to build an adjustable mold. I used a featherboard principle on each end, where my tip/tail blocks are allowed to slide in the alternating slots formed by the fingers. To adjust camber I built the blocks 3/4" taller than the base of the mold, and place a 3/4" mdf board over the top of some 'camber shims'.





The first pair of skis I pressed turned out...OK, for a first pair.
4001 base,
22oz triax FG
Maple/Poplar Core
22oz triax FG
White topsheet

I had some issues getting everything to fit in the mold, so I had once core shift during the entire process. I also had inserted some dowel pins in the core and glued to the base. I am NOT doign that again. I left them too tall, and they left impressions on the base. I also pressed them with almost no camber.

Here you can see the dd'd bases.


On the second pair of skis I build everything outside the press, put my press sandwhich together and then slid the entire thing into the press. The bases stayed aligned much better, but the camber I added was segmented, and not as fluid as I'd like. However I had stained the core and the bonding between the epoxy and wood is very strong.

Layup:
2001 Clear base
12oz triax Carbon Fiber
Poplar core
10oz biax Carbon
12 oz biax FG
Clear PVCP topsheets



Here you can see how section the camber turned out...



Any comments and suggestions are welcome. A big thanks to this forum for getting me started!

[skidesmond]

Not bad for the first sets of skis. I'm curious about the press. Very innovative. What pressure did you press at, could you detect much deflection and where did you get it?

I like the idea if sliding the form/mold into place. I wanted to do that on mine also but didn't at the time. Sometimes sliding the ski layup into the press can get tricky. I may work on that idea over the spring/summer.

I think you need to add more shims for the camber. Looks like the camber is a bit wavy in one of the pics. It amazing home much pressure there is at play and it looks like the 3/4 mdf may have flexed during the pressing. Try adding more shims. Then do a dry run of the press and see where the mdf flexes, add more shims if needed.

So how did they ski?

[Jekul]

I pressed at 40-45 psi for both sets of skis. I calculated deflection (without the mold) to be around 0.06", so maybe a bit less with all of the wood and mdf in place.

The camber on the second pair was very-funky and sectional. I've got another pair of skis ready to go for this weekend, and I'm going to attempt placing shims every 1" or less. And if I have (make) time I'll even do a dry run at pressure. In the long run I'll either make a fixed-camber mold, or ideally have some shims cnc'ed that run the length of the ski.

Since the bases on the first skis essentially turned out convex, they were really loose. When kept on edge they had good grip and a nice soft flex. But I was just exstatic that they held together for two days without breaking! It was a great feeling to be riding my own skis, definitely a pride-maker. I may persue this convex shape for a pair of park/trick skis in the future since it reduced the chances of catching an edge.

The second pair of skis turned out really soft. VERY SOFT. I attribute this to my poor consistency cores (too thin). Since I ski in the icy upper midwest I was going for something with moderate stiffness for edge grip. I missed by a mile. However...they turned out to be awesome mogul skis! The high flexibility allowed the skis to conform to the mogul shape, while the CF snapped the ski back into position for a consistent approach to the next mogul.

Since the third set of cores is finished already I'm going to use them on the next build. However from now on I'm plannign to use a local CNC shop to get some repeatability in the core profile.

[ben_mtl]

Good job !
You undoubtedly need more shims under the MDF camber, when I was reading and saw the pic of the shims I said to myself "he's gonna have wavy camber"... then I saw the finished skis.
You're on the good track. CNC is the way to go if you want accuracy but going with a CNC service for each pair of skis will cost you a lot of money... personnaly I have a set of templates CNC cut for each model of skis, then I try to work carefully and take great care in building steady and accurate tools (I'm talking about a router bridge for the core thickness).

What is that orange stuff on your ski ?
Where did you purchase the carbon tape ? Is it UD carbon ? I'm looking into adding a 2" UD Carbon strip on both side of the cores but it's super expensive...

[skidesmond]

...When kept on edge they had good grip and a nice soft flex. But I was just exstatic that they held together for two days without breaking! It was a great feeling to be riding my own skis, definitely a pride-maker. ....

I totally agree! The thrill is like skiing for the first time again. What are your core dimensions? My cores are generally 12mm+ under foot and taper to about 3mm to tip and tail. I use ash wood. I also have full wood cores, no tip/tail spacers or plastic sidewalls. They tend to be on the stiff side but hold excellent on the hard stuff. The next pair I'm going to bring the core down to about 10-11mm under foot and 2mm in the tip and tail.

[Jekul]

Ben- for the CNC service I'm looking at it's a $300 us engineering fee (he has to figure out how to program his cnc for 3D, he only does 2D currently). After the initial fee he figured it would be around $20/set of profiled cores. Right now at the hardware store I'm paying around $15/set for just core material...so I'm willing to pay a little more to have them precut.

The CF I used on bottom was 12oz triaxial 0, 60, -60, cost around $40/yd for a 30" wide piece. On top I used 2" UD I bought at a local shop (Express Composites, Minneapolis) on sale for $5/yard.

The orange part of the ski is acutally the stain I used on the core. I really pops through the ski. I wish I had used a narrower CF tape so it could be seen more readily.

Ski Dimensions:

Ski One: 133-96-116. however it should be noted that I forgot to account for the edge thickness during my build, so add about 4mm to all all dimensions. Core was about 10mm under foot, tapering to 1.5-2mm tip/tail.

Ski Two: 112-70-98 (plus width of two ski edges). 9mm underfoot, 1.5mm tip and tail. I also used tip/tail spacers on this pair.

[knightsofnii]

dude this is very innovative stuff,
you just made a complete mockery of the whole camber vs. rocker movement, with the "magne-rocko-cambi-what?"

Sorry I'm not bustin, I love seeing how things improve from one try to the next, so keep it up!! The camber shims are a neat idea, I hope you can figure out a way to groom out those bumps

[sammer]

My first reaction was the same as bens (camber will be wavy)
I don't know if more shims is the answer. I think you'll still end up wavy just not so much.
You might try using another sheet of 3/4 mdf.
I use a similar idea for my camber mold (but I vacuum) and find that 2 sheets of 1/2" mdf works better than more shims.( you'll probably still need more shims as well)
Your on the right track just keep at it.
One suggestion... don't put all your expensive materials into your first builds.
Figure out your process first then spend the money on carbon etc.

sam

[knightsofnii]

Yea we still have a scrap pile of "test materials" that we use when we try out new designs, new dimensions, new molds, etc.

And definitely dont go throwing big $$$ at stuff like sublimated graphics, carbon stringers, etc, until you can nail your basic stock build, your wallet will thank you and you'll be more stoked on building the next boards.

If I think back, it cost us over $10,000 before we were building consistently good stuff. That's probably not the norm, but it's real easy to get in deep. We've so far probably made every mistake in the book, but I think its made us better builders by learning the hard way . Keep it up!

[knightsofnii]

But if it makes you feel any better, my first 3 build attempts were done with a weak bottom mold skinned with formica, and sand-bags, and everything i could pile on top of them that had weight and mass. Third try, I used the first attempt as my "top mold/caul plate" and more more more more weight, and actually got a rideable board.
So dont worry about it, you're just going thru the growing pains of building, stay driven and you'll build sick shit!!

[CAFactory]

Instead of using shims underneath your bottom mold of the press for camber, how about using a planer to create a sloped piece of mdf (using a core profile type method. You could make 2, one for each side of the camber. The slope would be completely smooth and therefor you would come out with a nice, even camber. Its an idea I've been playing with and will try out when I get my press made.

[sammer]

CA... I used a core that I accidentally profiled too thin to shape my camber mold for a few of my skis.
(First core I spent real money on, used pine and maple and birch)
I ripped both cores down until they were,
when side by side, the same width as my mold.
It worked awesome for an improvised mold.
That mold is still in use, and although its had a few mods, the old core is still under there.

sam

[Jekul]

Thanks for the suggestions guys. Just so you know I got all the triaxial carbon for free as a 'test sample'. So no money spent there. Everything else was as cheap as I could find for being in such small quantities. I was at around $145/pair on the second set. Of course if I added in my time then they're priceless!

Right now I'm having difficulty making a planer crib for my 13" planer. I'd really love to be good at this because it would save me money and improve my quality. I did try to make a planer crib two weeks ago...I'll try to post some pictures, but I haven't taken any yet. In all my wisdom I made it 8' long. I designed it to have the core sit in the middle. The primary problem I had was that the leading edge of the crib was taller than the core. So I couldn't put it through the planer without hitting the leading edge. I thought it was similar to the other designs on here, apparently I'm missing something...

[CAFactory]

I had this problem as well. For me, the answer was to make the core profile flat at the tips for the first 4-5 inches, if not more. If the top board you are using will not bend to horizontal you might want to try using a thinner board. That being said I understand that others might do it differently.

[powderho]

Right now I'm having difficulty making a planer crib for my 13" planer. I'd really love to be good at this because it would save me money and improve my quality. I did try to make a planer crib two weeks ago...I'll try to post some pictures, but I haven't taken any yet. In all my wisdom I made it 8' long. I designed it to have the core sit in the middle. The primary problem I had was that the leading edge of the crib was taller than the core. So I couldn't put it through the planer without hitting the leading edge. I thought it was similar to the other designs on here, apparently I'm missing something...

I think 2-4" longer than your core, per end, for the planer crib is just about right. If it's much longer its prone to being eaten by the planer. My old planer crib was shorter than the cores, and it worked just fine too. A bit more snipe though. My crib is just two pieces of 3/4" MDF and some shims. Scrap poplar shims made with the planer work good enough. I have multiple t-nuts inserted in the bottom MDF. They really help get a snug fit when your bolting it together. I use some 100-grit sand paper and spray adhesive that holds the core down all right.

I was checking out the industrial racking at my work that looks a lot like yours. It claims a load rating of 4000lbs right on it. Who knows what the factor of safety is on that. 3-5? Still not that strong. I've always been curious as to how people estimate the force their press is seeing. How did you figure out the contact area of the bladder inside the press? I figured that 2/3 of the surface of the bladder was actually in contact with the press. With this reasoning, my factor of safety was around 2.6 at 100 psi. That's for the 40, 1/2" grade 8 bolts that link the top and bottom pieces of my press. Deflection of the steel itself was negligible. Anyway, nice work and ditch the shims.