lightest glass that is safe to build with?

[krp8128]

looking at t his pic, the break seems pretty clean for plywood, the only splintering seems to be at the top and bottom.

I wonder if this was one of those butt-jointed long cores?

[skidesmond]

Does anyone know how this ski broke? I've never seen a ski break so cleanly and have an metal edge snap too. I've seen skis delam and even that on rare occasions. I noticed the groove in the plywood core, must be where he had a wood dowel for alignment (or maybe forgot it... )

As far as using plywood, I wouldn't use it unless it was a high grade furniture with no voids. And that plywood is expensive. At that point you're better of using regular lumber. The plywood at most big box stores isn't that great...

[krp8128]

I don't know where it was posted, but supposedly he uses the highest quality void free plywood money can buy, and it costs him somehting like $8 bucks a core...

I noticed the edge too, seems mighty suspect to me. Could save a little bit of money by using edge scraps every 5th ski or so.

[MontuckyMadman]

he doesn't use dowels so the alignment holes are just huge voids in the matrix.

Must be where he had a butt joint and he has an alignment pin there? How could you not have a longitudinal composite for compression strength?

As long as this guy has been around he really missed some key data on construction.

I said this on ttips the double bias sh1t is his downfall, well that and but jointed plywood. I think a continuous ply laminate with the appropriate weight of composite could work just fine.

[skidesmond]

I'm not an engineer (as I said before) but using a butt joint in a ski seems like a bad idea and I don't know why anyone would use one. I saw a video from ELAN on youtube and in the ski building process they also used a 2 peice core butt jointed. That was a surprise! But I guess if the rest of the material in the ski is good, it must be ok to use? IDK... Still not sure why they would want a butt joint in the ski.

I've thought about jointing wood together, however I was going to use a special router bit (lock joints) made to join wood together, only because I have a lot of scrap laying around after making other projects and it goes into the wood stove or fire pit outside. Lock joints are stronger and gives more glueing surface area than a butt joint.

I have have enough ash and maple for at least 20 pair of skis before I have to think about either vertical/horizontal glue ups.

[MontuckyMadman]

have seen factory cores finger jointed the entire way as a vert lam.


Just want to say that 333 is doing great things with relation to this open source manufacturing. Basically all we do here and sharing all his tech and parts and pieces.

Sounds like he could benefit from some advice from others rather than trial and error.

Are those really that tgr doods kids skis?

[Head Monkey]

So, you know why plywood is cool in general, right? It’s strong for many interesting applications, it’s cheap, and it’s stable. Great for making lots of things: cabinets, boxes, floors, walls, soap box racers, etc. Why’s it stable? Because the plys have their grain oriented at right angles to each other.

Now consider making a ski core out of it. You end up with half of the wood in your core oriented with the grain going across the ski instead of lengthwise. Half the wood no longer provides any longitudinal strength. Half the wood is no longer helping with stress along the axis of greatest stress in the ski. Now add improper reinforcement (glass too light, poorly consolidated laminate), drill a hole through the center of it, and place that hole right under the toe of the binding. Genius. I’m amazed all skis and snowboards aren’t made with plywood. Not!

Look closely at the picture. You’ll see a ragged edge on half the plys and a smooth edge on the other half. The smooth ones are the ones where the grain is running across the ski, the ragged ones are the ones where the grain ran the length of the ski.

And, of course, a reasonable fraction of the mass of the plywood is glue holding the plys together, which is also pretty worthless.

The 333 guy is using plywood for one reason: it’s cheap.

[sammer]

Well said Mike.
But consider 12oz biax or bias ( the jury's still out on this) top and bottom is about half what the real world is using for reinforcement.
I'm thinking 333 is out to lunch.
That same core with 19 or 22 oz triax glass would probably stand up to a little more abuse.
I still can't see myself using plywood any time soon.
and to answer to original question, any combination that gives you 19 - 22 oz
(equivalent) of reinforcement in three directions is probably alright as long as the majority is running 0 degrees ( along the length of your ski)

rebuttals?

sam

[doughboyshredder]

Well said Mike.
But consider 12oz biax or bias ( the jury's still out on this)

How's that? The pics of the skis before being broken clearly stated 12 oz bias. You could even see the fabric. In dipshit's own rundown of why the ski broke he asks "maybe it was the bias fabric?"

[knightsofnii]

i have been brainstorming over the yrs about how to set up a "mobile factory" and go on tour once i had something worth touring. But i would never even attempt it until, well it looks like I already build better shyt than this guy.

I think plywood could be used if its done right. However, home depot plywood? not. If i were gonna do the plywood route, or "horizontal lamination", i'd look to how skateboards are built.
I just dont think the whole core profileing thing works when you have a horizontal laminate, you're taking away layers as you plane down.

I dont know man. "garbage in = garbage out"

I dont mind that it costs me $130 to $150 in materials alone to build my boards, you gotta pay to play.

$399 custom ski. If i were building custom skis, the cheapest they'd go for is $1000. You cant even get a good commercial ski for 400 bucks.

he probably uses home depot resin too. If only he knew that qcm was actually cheaper!! LOL

[knightsofnii]

regarding the 12oz glass. Or lighter glass.

I wouldn't do it with a "production" grade board/ski.

I'd let pros experiment with it, at their own risk.

Pro surfers do that, lots of pro surfers rocking 4oz potato chips, they last one or two sessions then they're junk.

[knightsofnii]

i do admire the guy's vision though.

Is he pressing, or vac bagging?

[knightsofnii]

i just watched all the videos, wow.

He should just figure out how to put a pneumatic press in there somewhere, get some real woodcores, thicker glass and bases, and i dont see why he wouldn't be able to make some bomber skis.

The "rail package" is pretty neat though.

After building all that stuff, i dont see it being that difficult for him to step up his game. he could cap with a wide air bladder press with no cat track. and hanging the skis like bats while they cure is causing all the resin to run to one end of the ski when it heats up.

I dont know man, just a mishmosh of super amazing ideas mixed up with some really poor ones. I wish i was that handy though

[bobbyrobie]

does anyone know what supplier he is using for that base material that is faulty? looks like green/black mixture. i have a roll of what looks to be the same stuff wondering if mine will have the same issues.

[LifeisRiding]

if your base material has a layer of black material on the bonding side, then i would assume you will have a similare problem,

I really admire His ideas and way of doing things, i mean that picture of the broken ski is pretty incredible, but when your building large numbers of products weird things will like that will happen. I have seen a few burton boards completly snap in amazing and unique ways. Also the actual accident that broke the ski, could be the reason

I used Baltic birtch on my last prototype, and its working awesome!
It might be the new design rather then the core, but it has tons of pop!! more so then the verticaly laminated poplar cores i built for my boards last season. Having a ply core seems to add alot of strength because each layer of ply has grain running tip to tip and edge to edge, instead of having many layers of glue between the grains edge to edge.

Also with the baltic birtch i use for every two layers of grain orrientated tip to tip there is one layer that is orrientated edge to edge adding alot of torrsional and egde to edge strength.

Its also alot cheaper and qwicker to build these cores.

I think he is not using a peumatic press because he uses the heat from the sun to cure the boards in the black vacum bags on top of the trailer...