Finaly ive got my thumb out of my ass and orderd the stuff needed for my first pair of skis. So new to this forum and new to skibuilding. But damn! im up for the challange!
I may bee new too skibuilding but not to composites and the making of grp/frp pruducts. Ive been building model airplanes out of composites for 3 years now, mostley whith vacuum bagged wings around foamcores and fuselages made in moulds. Therefore my first skis will be made vac bagged as I got all I need for that. I hope to bring some new ideas into the skibuilding and offcourse, learn alot from you more experienced guys on this forum.
Why do I want to make a ski then? Well, simply because a think i can make a better powder ski when whoose out there on the market today. And I do have alot of ideas of how to do it.
Enoght of crap talking, lets get to the buissnies!
The meassurments of the ski will be 150-135-120, 182cm. Yes, thats a completly straight ski. From my point of view, sidcut is bullshit when it comes to riding in deep snow. As you edging your ski in deep snow they will bend anyway. And its the bending of the ski thats creates the turn, right? Sidecut just makes skis nervus at high speeds.
Ususally i ride skis thats 10-15cm longer then myself but this ski will be an exeption. (Im 182cm long and weigths about 98kg) Just because im looking for an easy manuverable ski in the trees.
The core should be made only out of balsa wood. And some Birch plywood for binding reinforcment. The balsa is just for keeping the wight down. My goal is to make the skis lighter than 3kg a pair.
The sidwall should be made out of the same p-tex material as the base. Not thick but hopfully enough, and it keeps the weight down.
The profile of the core should be from 12mm thick underfoot to 3mm at tip and tail.
I will use one layer of 750g triax glas and one "diamond" cutt layer of 100g uni carbon cloth.
Havent really desided about the rocker profile but it will be a full rocker ski.
As for the design. Im thinking about using black coloring paste for the epoxy. Have some good experiense of this. And then airbrus a thin mylar film that I will be next to the glass layer in the vacuum bag. The epoxy will soak upp the paint and then the epoxy is cured, the mylar is pulled away leaving a mirror blank pinted finish (hopefully). This is a method used then vacuumbagging aiplane wings.
So, you guys out there. U think it will work?
Uppdate will come as soon as i get all the stuff that I orderd.
Regards //Kalle, Sweden
ps sorry for bad grammar and spelling. Please corect me if somthing is terrible wrong but just DONT wine! I can do this without shoowing it to u!
Balsa core fattys, first try!
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MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
Ive been giving this a lot of thought to. But i came to that conclusion thats its not going to delaminate. I think the balsa wood is a realy underestimated wood just because of its low density.fa wrote:I m afraid balsa won't work
Soon (very! soon) the top skin will delam from core
best of luck
Have you tried this so you know its not going to work or is this just your own thougts?
And where do you think it will delam? In the bonding betwen the epoxy/wood or in the wood it self?
Have tried to search the forum for some threads about balsa skis but havnt found anyone that actually made one and tested it. Or im I wrong?
there is somewhere in this forum a thread about a balsa core snowboard, but i couldnt find it. It delamed first turn.
I never tried a full balsa core. A friend experiment with balsa and a variate of FG and CF cloth skins in building kiteboards this past summer. He made the 3 lightest boards i ve ever seen and then he gave up. They all delamed the first day, just beyond the binding area. In all 3 it looked like buckling in the top skin. He used this 100*10 cm balsa planks (very popular in model making) so the grain was running length wise. I think this is exactly the problem with his design. Balsa is a unique wood with great fiber strength to weight ratio. But these fibers arent held together much, so it has very low resistance in tension applied perpendicular to the grain. (its very easy to peel a fg skin off a balsa plank and when you peel it you ll see quite alot of balsa left stuck to that skin. it s not that easy to peel a fg skin from lets say a spruce plank and then not much spruce will be left on the peeled skin).
Balsa wood is very successfully used in quite serious structures (yachts hulls for exmpl) but there the grain is mainly running perpendicular to the 2 composite skin planes -end grain configuration (check the "baltek" balsa scrim core, i think from "alcan"). In such a structure the core is there mainly to keep apart the two skins, unlike to a typical ski where the sandwiched core is a major flex resisting member.
If you are determent to go on with the 100*10cm planks (with length wise grain), you might wanna add some full length stringer (s), and/or some serious wooden sidewalls to keep the top skin from buckling.
Just my thoughts,
best luck and keep us update
edited: in these kiteboards my mate build, balsa strips were quite wide, 10cm in the 1rst one, 5cm in the 2nd and 3rd & I believe that this was an issue as well. If you go with quite narrower strips epoxied together, then the "epoxy stringers" created on the glue seams might hold the skins better in place.
I never tried a full balsa core. A friend experiment with balsa and a variate of FG and CF cloth skins in building kiteboards this past summer. He made the 3 lightest boards i ve ever seen and then he gave up. They all delamed the first day, just beyond the binding area. In all 3 it looked like buckling in the top skin. He used this 100*10 cm balsa planks (very popular in model making) so the grain was running length wise. I think this is exactly the problem with his design. Balsa is a unique wood with great fiber strength to weight ratio. But these fibers arent held together much, so it has very low resistance in tension applied perpendicular to the grain. (its very easy to peel a fg skin off a balsa plank and when you peel it you ll see quite alot of balsa left stuck to that skin. it s not that easy to peel a fg skin from lets say a spruce plank and then not much spruce will be left on the peeled skin).
Balsa wood is very successfully used in quite serious structures (yachts hulls for exmpl) but there the grain is mainly running perpendicular to the 2 composite skin planes -end grain configuration (check the "baltek" balsa scrim core, i think from "alcan"). In such a structure the core is there mainly to keep apart the two skins, unlike to a typical ski where the sandwiched core is a major flex resisting member.
If you are determent to go on with the 100*10cm planks (with length wise grain), you might wanna add some full length stringer (s), and/or some serious wooden sidewalls to keep the top skin from buckling.
Just my thoughts,
best luck and keep us update
edited: in these kiteboards my mate build, balsa strips were quite wide, 10cm in the 1rst one, 5cm in the 2nd and 3rd & I believe that this was an issue as well. If you go with quite narrower strips epoxied together, then the "epoxy stringers" created on the glue seams might hold the skins better in place.
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twizzstyle
- Posts: 2204
- Joined: Tue Mar 07, 2006 8:25 pm
- Location: Kenmore, Wa USA
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PowderKing
- Posts: 20
- Joined: Mon Feb 08, 2010 6:21 am
- Location: Davos CH and Laren NL
- Contact:
http://www.bmb-ski.nl/index.php?option= ... 72&lang=nl
It's dutch but with google translater....
They tested balsa with carbon for a climbing ski.
It's dutch but with google translater....
They tested balsa with carbon for a climbing ski.
Building skis when there ain't no pow!
Yepp, its the 100*10 balsa sheets im planning to use. Got the idea from my model airplane making. Where we use thin balsa sheets betwen to grp/crp layers as vingskins in hollow molded constructed wings. And there it works oustanding. Just because of it compresion streng compeared to other foam materials.
But my idea is as mentioned, to make stringers out of the balsa sheets and glue them together with epoxy. (There is stringers in 100cm lengthes to by but thats much more expensive) And maybe even put some uni corbon in between the stringers. Or maybe som standing 1mm balsa in between the stringer. This should realy help the core from compression and bucking.
But after reading the link and heard from your storries i change my mind about the mounting plates. The binding mounting should be in some moore high density wood stringers glued in. And maybe even some higher density stringers on the edges.
Really thanks for the input guys! Super forum so far!
But my idea is as mentioned, to make stringers out of the balsa sheets and glue them together with epoxy. (There is stringers in 100cm lengthes to by but thats much more expensive) And maybe even put some uni corbon in between the stringers. Or maybe som standing 1mm balsa in between the stringer. This should realy help the core from compression and bucking.
But after reading the link and heard from your storries i change my mind about the mounting plates. The binding mounting should be in some moore high density wood stringers glued in. And maybe even some higher density stringers on the edges.
Really thanks for the input guys! Super forum so far!
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Eirik Hanes
- Posts: 53
- Joined: Tue Nov 09, 2010 11:47 am
I am thinking about using balsa or divinycell for skis aswell, check out www.diabgroup.com they have a bunch of different core materials.
Balsa cores....
Balsa cores can work.
Been building balsa cored skis and boards since 1992. There are no inherent problems with it. You do, however, need to design/engineer around the material to get the most of its strengths, and to minimize the weaknesses in the material.
Firstly, skis (or boards) are a cored panel composite structure. Their behavior and load requirements can be calculated accordingly. This means that the core needs to have sufficient shear strength, resistance to crushing, etc., that are needed for the structure in question.
That out of the way.
What do you need to do to make it work? A few things.
1. Make the cores thicker than a typical wood core. Probably about 2-3 mm in the shovel. 13-15 mm underfoot, and back to 2-3 at the hip.
2. DO NOT GO SHY ON GLUE/RESIN ON THE UPPER FACE/CORE BONDLINE!
oops. Gotta go, will finish later
Been building balsa cored skis and boards since 1992. There are no inherent problems with it. You do, however, need to design/engineer around the material to get the most of its strengths, and to minimize the weaknesses in the material.
Firstly, skis (or boards) are a cored panel composite structure. Their behavior and load requirements can be calculated accordingly. This means that the core needs to have sufficient shear strength, resistance to crushing, etc., that are needed for the structure in question.
That out of the way.
What do you need to do to make it work? A few things.
1. Make the cores thicker than a typical wood core. Probably about 2-3 mm in the shovel. 13-15 mm underfoot, and back to 2-3 at the hip.
2. DO NOT GO SHY ON GLUE/RESIN ON THE UPPER FACE/CORE BONDLINE!
oops. Gotta go, will finish later
A litle uppdate from sweden. Ive been reading a lot about balsa and other light weight materials in skis. And ive realized there is a lot of problems to be solved to just go with balsa.
Therefore my ski will be a bamboo/balsa hybrid core to solve some of the problems wich comes along with a pure balsa core. Still thought, im aming for an really low weight powder ski.
Unfortunally, the guys at bmb ski that are suppling me with bambo. Had there shippment of bamboo delayed from china. So hoping to be back building in february somtime.
Big thanks to bmb skis for fast and smoth mail replys thought.
I will be back here as soon as my material arives.
Therefore my ski will be a bamboo/balsa hybrid core to solve some of the problems wich comes along with a pure balsa core. Still thought, im aming for an really low weight powder ski.
Unfortunally, the guys at bmb ski that are suppling me with bambo. Had there shippment of bamboo delayed from china. So hoping to be back building in february somtime.
Big thanks to bmb skis for fast and smoth mail replys thought.
I will be back here as soon as my material arives.
