Josh's ski building.

Josh · Post by **Josh** » Sun Oct 10, 2010 7:21 am

Right, having been a lurker for a good 2 years i've finally take the jump and decided to just do this

I've read virtually every post here 10 times and think i'm ready to invest the time and money.
I came across this great site while building some wooden skis a few years ago, and decided that after that project was finished i'd start on some serious skis. The wooden skis were brilliant but they were only really good for cross country, and i'm far more interested in alpine skiing

I figure i'd put some pictures of the old skis up to keep you interested while i do some ski building

(and it lets me practice/work out how to put pictures up.

Leather Bindings by josh's ski building, on Flickr[/img]

and they got some use in snowwy scotland this winter

IMG_1904 by josh's ski building, on Flickr[/img]

Just an extra picture now

IMG_1914 by josh's ski building, on Flickr[/img]

Right, now i'm off to do some ski building and take some pics. I should be able to give you a proper update on the ski building in a few hours

Josh · Post by **Josh** » Sun Oct 10, 2010 8:45 am

First proper update

I spent a few hours this week trying to decide on a relatively simple, easy to use press. I am currently settled on using an i-beam press because, despite the high cost, i think i would like to be able to load the press from the side. I designed my first press in sketch up. (see below)

Sketch up press by josh's ski building, on Flickr[/img]

The i-beams i intend to use have the dimensions of:
305mm high
165mm wide
10.2mm flange
6mm web
This means i will only be able to press one ski at a time due to the width of the i beams. But the more pressing (excuse the pun

) issue is how much the beam will deflect.
I am going to have a 2 meter unsupported length and intend to press at about 50psi.
My calculations:
I used this equation, however i am not an engineer. I believe this equation is for when there is a 'point load' and i think i'm right in saying a ski press doesn't exhibit a point load? (but atleast it will give me an idea of the deflection

)

max deflection=(load*unsupported length^3)/(48*Y.M*moment of inertia)

when i put the numbers in:
Y.M (youngs modulus)- 200GPa
Moment of inertia- 8503 (from an engineering website not my own calculation)
Load- 150"^2 at 50 psi = 34020 N
I got a deflection of 0.3mm. Can anyone confirm if this is in the right ball park?

I have also spent some time creating the core and top/bottom molds.

Mould template by josh's ski building, on Flickr[/img]

Bottom mould 2 by josh's ski building, on Flickr[/img]

and some core profiling using a router. (i wish i had a planer)

Core profiling jig by josh's ski building, on Flickr[/img]

and the cores

Core profile by josh's ski building, on Flickr[/img]

Well, i think that's it for today. In the next week i'm hoping to be able to start building a press, then order the materials and do all the rest of the stuff.

Josh

OAC · Post by **OAC** » Sun Oct 10, 2010 9:58 am

You're on your way! Good work.

What radius are you using on tip and tail? Just curious. I'm working on a new mold today and can't decide...

Cheers!

skidesmond · Post by **skidesmond** » Sun Oct 10, 2010 12:39 pm

Great progress! You're on your way. Think about a press that will accommodate 2 skis if you can. I know it means more $$$. I say this only because it doubles the time for everything.

You can always add to it later also. Looks like you have a pretty beefy set up. Looking forward to seeing some skis! Good Luck!

Josh · Post by **Josh** » Mon Oct 11, 2010 8:02 am

Hi, thanks for the encouragement, it's good to know i'm heading in the right direction.
OAC- I think my mold has roughly a 175mm radius at the front and 200mm at the tail. But i'd have to check on snow-cad for the true dimensions

Skidesmond- i wish i could have a 2 ski press, however i am more concerned about consistency between the skis if they are pressed separately. (will temperature differences or minor changes make a noticable difference to the ski?) Time is less of an issue as i don't intend to go into production. I figure that once i have a press i could always create another identical press and weld, or bolt these together to produce a press capable of pressing 2 skis at once.

Josh

skidesmond · Post by **skidesmond** » Mon Oct 11, 2010 9:25 am

Pressing 2 at time gives more consistency. I don't think minor temperature differences will be a factor.

doughboyshredder · Post by **doughboyshredder** » Mon Oct 11, 2010 2:34 pm

skidesmond wrote:Pressing 2 at time gives more consistency. I don't think minor temperature differences will be a factor.

a couple degrees difference can effect the camber.

Idris · Post by **Idris** » Mon Oct 11, 2010 11:32 pm

Where abouts int the west Midlands are ya? I'm driving past in a few days.

Tom

skidesmond · Post by **skidesmond** » Tue Oct 12, 2010 4:26 am

doughboyshredder wrote:
skidesmond wrote:Pressing 2 at time gives more consistency. I don't think minor temperature differences will be a factor.
a couple degrees difference can effect the camber.

Ok, guess I have another variable to try to control.

Josh · Post by **Josh** » Tue Oct 12, 2010 1:20 pm

Right, I've got little to show you right now but I have taken some big jumps forward in the process. Firstly i have a friend, with plenty of metal working experience creating the press. I gave him my designs and he is pretty much going to stick with the original dimensions. Secondly i have managed to source some 9" flat firehose (thanks to richuk's contact

) Once both of those have arrived i should be well on my way to the first pair of skis.

Currently i feel unqualified to state whether temperature will effect the camber of the skis, however i would guess that a change might result in a slightly stronger, or weaker 'set' with the epoxy which may influence how well the ski can hold its camber.

Idris- I'm not sure how to quote yet, so i hope you see this. I'm based in worcestershire, just a few miles outside of worcester itself.

Josh

Josh · Post by **Josh** » Sat Oct 30, 2010 12:58 pm

Finally another update, i've been working on a few things. Firstly i've got a steel press

it's similar to the design i showed above, but uses 8" x 8" i-beams. Though it has a 12" gap between the two main beams. It's untested at the moment, but it should be ok. It's held together with 16 grade 8 1" bolts and some welding around the edge of each joint, which was done by a friend who knows a lot more about metalwork than me ( but i'll stand well back upon first inflation anyway!)
Here are some pictures...

Ski Press 1 by josh's ski building, on Flickr[/img]

Oh, i've also routed out the rest of the molds for the ski as shown in the pic. No pictures of that process though, i couldn't take photos and route (sp?) at the same time

Ski Press 3 by josh's ski building, on Flickr[/img]

Just a picture of the mold, i haven't yet bolted it together, so some of the bits look uneven, though once they're lined up they should be spot on identical

Ski Press 5 by josh's ski building, on Flickr[/img]

Another one of the press frame.

I have also got hold of some 6" when inflated firehose. And have finished profiling my first cores, (it's pretty scary when you see how thin 2.5 mm is but i guess i've got to trust the calipers

That's all for now. Though i would like to know, am i better to use an aluminium (aluminum for some of you

) cat track or can i get away with 3/4" square wood?

a.badner · Post by **a.badner** » Sat Oct 30, 2010 6:47 pm

wood is doable. but you need a strong bungie/spring for it. my cat track is made of hockey sticks.

but consider.

my $o.o2 are that you have a one ski press. a cat-track is less than necessary. the cat tracks are good for two/three hose presses. they ensure uniform pressure. but on a one ski press its un-needed. AND youre using a 6 inch hose.

when a hose is being limited to two sides ( on the y axis in this case), the hose expands perpendicularly ( towards the x- axises )

here is a equation for that.

let x= height of opening in between molds (to be calculated)
let y= width of hose while compressed. ( ski width )

and to determine height of top mold mold :
let a = height of base mold
let b = full height of press opening.
let x = calculated number from first equation.
and c = be height of top mold.

it worked for me. hope you consider this.

EricW · Post by **EricW** » Sat Oct 30, 2010 7:00 pm

I'd probably stick with a track just to make sure you get a good press out of it. You'd want quite a bit of overhang on the bladder otherwise. Not sure you will get that with only a 6" hose. May be do a few test inflates to see what kind of coverage you get before spending the extra cash on a track.

Press looks pretty sweet by the way.

a.badner · Post by **a.badner** » Sat Oct 30, 2010 7:10 pm

only a 6" hose

6'' when infalted. thats a big hose.

its a 8'' layflat i believe.

EricW · Post by **EricW** » Sat Oct 30, 2010 7:31 pm

It's more like 10" when flat I believe. Still, you'd have to make sure you get good coverage. The hose would have to have almost no clearance to stay wide enough when inflated. Seems like kind of a hassle to squeeze a layup into the press that way.

November Snowboards didn't use a track but he did half cap or full cap construction. I'm not sure if it's ideal for sidewalls. I can't remember where he got a bladder that big.

Ski Builders Forum

Ski Builders Forum

Josh's ski building.

Josh's ski building.