Goat-Ham-Ah project

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ben_mtl
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Goat-Ham-Ah project

Post by ben_mtl »

Hi all !

After hours of reading treads here and on other websites, I finally started building my own skis !
I first had to find what ski I will make... my program with this ski will be mainly backcountry skiing, I plan on installing Marker Duke bindings on it.
I thought it would be easier for a first pair to inspire myself from an existing model. The Volkl Gotama seemed to be the kind of ski I am looking for so that's my reference : not too long, mid-fat for eastern Canada's mountains, nice turn radius... let's try it !
Length will be 176cm, 133-105-124, +-25m radius.
I used Endre's excel sheets for almost all my dimensions (thanks a lot for that !)

I plan on vacuum bagging my skis as it's less investment for a first attempt and I have all the material for that (I make my own kayaks)

After a lot of sketching I choose a 12mm camber (it my be less when out of the mold) and I took my actual skis (Movement Yaka) as a reference for tip and tail radii. Then I made my mold.
It's made of MDF as most of you guys do covered with 3/16 wood plate, I don't exactly know what it is but it's shinny one one side and bends not too bad to follow the mold shape.
The mold is in 3 parts : tip / running length / tail so I'll be able to adjust for other models (and maybe a splitboard)

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I will shape the core with a planner but first I have to decide the dimensions I'll give it. If I follow Endre's dimensions, combined with lot of measurements of pictures of those skis with bindings, I find that the binding will be far back on the ski. When trying to analyse it with flex analyser excel file (sorry I don't remember who did it but greats thanks also for him !) that's what I have :

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As you can see the binding thick zone is not centered at all... do you guys think It will be a problem ? Did I made a mistake ?
Tips thickness will be 2mm (Tip spacers thickness) and the binding area will be 11mm, I think it should have a good flex considering my 150 lbs.
The core will be made out of maple and poplar, I still don't know if I will make wood or ABS sidewalls, I thought ABS would last longer but that seems it's hard to bond properly to the core, the first skis may have maple sidewalls...

I'm now waiting for my core and base templates to be cut by a CNC (a friend takes care of it) and I'll then be able to start the core.
I'm also waiting for other materials I ordered at SnowboardMaterials.com, I ordered about 2 weeks ago and I still have no news if anything has been shipped... they seems not being very good with communication !

to be continued...
Last edited by ben_mtl on Tue Jun 17, 2008 3:25 am, edited 1 time in total.
ben_mtl
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first update

Post by ben_mtl »

So here are the next steps :

Wood cut in 3/4x3/4" stripes (poplar and maple)
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Stripes being bonded
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Cores after the first planning operation (to have flat surfaces to work with)
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CNC cut templates
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First cut following core template then bonding the maple sidewalls (oversized for now)
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Tip spacers
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The crib
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Cores going though the planer for profiling, first pass to reduce thickness in tip and tail.
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Right now I'm in modifying the crib to be able to profile to the final thickness (tapered with flat tip and tail)

I'll keep you posted

Ben
plywood
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Post by plywood »

you`re truly on the right path! sweet templates, by the way ;) it all looks very clean and well thought out. i`m looking forward to seeing your progress
plywood freeride industries - go ply, ride wood!
ben_mtl
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Post by ben_mtl »

Thanks Plywood ! I'm really not a born woodworker so it takes me some time to figure out the good way to do things ;)
If everything goes right I should be done with the core profiling tonight..
next steps : edge bending... I need to think about an edge bender without the big metallic cylinder thing, I doubt I can find something like that in an hardware store.
rockaukum
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Post by rockaukum »

Go to an auto store and get a tube bender used for bending break and fuel lines. Should cost around $10 -15. Works well http://www.skibuilders.com/phpBB2/viewt ... dge+bender. Another option is to tuck or terminate the edges and not bend them around the tip nad tail sections.
ben_mtl
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Post by ben_mtl »

yep that's what I did on the tail, my edges stop before the tight bend (i did it because I wanted a recess for the skins tensionnner to go through)
On the front tip I actually prefer having a full edge wrap, I'll try to find the tube bender, thanks.
ben_mtl
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small update

Post by ben_mtl »

I'm almost done with core profiling, it took more time than expected..
I'm using the planer method to profile cores, theorically it's super easy but I had a lot of troubles trying to have a straight cut (for the planner to remove the same thickness on both sides of the ski).
I checked the geometry of my crib almost 100 times and it was OK, my guess for all the problems is the planer support was a litle bit twisted... It was a friend of mine's so I'll see if I still have problems when I'll buy one for myself.

I followed rockaukum advise and bought a fuel line bender, did a groove on the main wheel and I now have the perfect and easier-to-use edge bender on earth, it's almost too easy and the first time I tried it I was even wondering if I'd need an "un-bender". It takes time to make a clean job but it's easy.

Here are some pics of the modified tool :

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I'll post some pics of the core later today.
ben_mtl
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Post by ben_mtl »

After a busy 2 weeks of moving and trying to make a nice workshop in my basement, I'm finally back on ski building !

Here is my new status :

Core are the correct thickness and I'm pre-bending tips and tails. It seemed to be a pretty easy thing in my mind but appears to be tricky. First I tried to put the ski over a bowl of boiling water the constrain it in a mold and letting dry-> bad idea : the wood starts bending in an uncontrolled and worrying way as soon as it's being steamed.
Then I tried putting the core directly in the boiling water -> same result.
I finally ended leaving the core in the "bending mold", and moisturizing it with a water spray, then drying with an heat gun. It's not a complete success in my opinion and I'm quite disappointed with the result : core is bent but there are some "waves" mainly because of the mix of 2 timbers (maple and poplar). The core is now resting in the mold after being moisturized. hope it will be OK.
If anyone could give a good description on how to do it would be great !

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I also started bending my edges wth my "wonderfull" tool ;) . It work really well but it takes time anyway to get the edge bended the closest to the template.

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bluedog
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pre bending tips

Post by bluedog »

If you want to pre bend tip or tails - try using a bit of steel pipe 6 inches or so diameter and put a blowtorch inside it to heat up the pipe. Spray tip/tail with water then put oven paper over the wood - bend over the hot pipe. Have a practice with some scrap to get the right amount of heat - water should bubble a bit and then turn to steam when sprayed on the pipe. This is how the sides of guitars are bent. If your cores are laminated and glued with epoxy the epoxy may give a bit but should still hold when cooled. This method works a treat with wood veneer topsheets!
ben_mtl
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Big Time !

Post by ben_mtl »

Finally did it !
I removed my skis from the mold yesterday evening after a 24h cure.
Result is awesome ! There are a few little details which are not so good be the general result is really satisfying!
So everityhing went great, laying up was fine and I can say my centering system works. Not too much resin, the vacuum bag was well sealed so the pump was almost not working (this way there are less chances for the resin to be pulled out of the fiberglass)
For now I only have a few pics to share as I have not so much time to write a long story.
Here it is : http://picasaweb.google.com/b.dalcas/Sk ... gGoatHamAh

No need to say I'm very happy with the result, I still need to flash everithing accuratly (anything about how to do this easily?) but I'm already working on the 2nd pair and a splitboard !

Ben
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RoboGeek
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Post by RoboGeek »

hehe.. your addicted now. Soon you'll be shopping for a house with storage space for all the skis!!

Post more pics as you get them!
I used to be a lifeguard, but some blue kid got me fired.
ben_mtl
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Post by ben_mtl »

Here are some new pics of the (almost) finish skis, just need to bevel the sidewalls but the flashing is done.

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Closeup of the sidewat-to-tipspacer transistion :
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Closeup of the tail : a small recess for the skins straps :
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Without binding they weight 2kg each (4.4 lbs) which I think is not so bad for a ski that size.
Last edited by ben_mtl on Wed Aug 06, 2008 3:39 am, edited 1 time in total.
hugocacola
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Post by hugocacola »

Nice looking skis

but now just sand them with a somthh grip tape (for car finish pait) and aply a nice grafic with car paint and then varnish over it.

happy ride
ben_mtl
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Post by ben_mtl »

new pics of my 2nd pair of skis and my 1st split board.

http://picasaweb.google.com/b.dalcas/Sk ... gGoatHamAh#

Sorry I can't give too much details as I'm on the road in the Canadian Rockies, waiting for the snow to fall :p

Ben
plywood
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Post by plywood »

i like the grafics on the ski. has a bit of a geometrical artsy touch! ;)
plywood freeride industries - go ply, ride wood!
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