Have been reading the posts on the cloth issues and methods. From what I have read in the past, it seems that people are using biaxial then a cloth (graphic layer) then uni- glass as the top sheet. Is there any known problems with doing a triaxial glass then a cloth (graphic layer) as the top sheet with out using any further glass layer?
Thanks for the help.
rockaukum
further cloth discussion
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Hi rockaukum,
I use a lot of bi-axial and uni-directional in my lay-ups, and one thing that I notice is that the bi and uni layers are much more visible in the lay-up than the triax is... meaning that the fibers of the bi and uni glass don't turn as translucent when wetted out. So, if you want the best color from your cloth top sheet, I'd say put it on top of the glass layers, regardless of what glass you're using. I also like my glass layers to be adjacent to each other, without a none-structural layer (cotton cloth) disrupting the integrity of the lay-up. For me, the only disadvantage to using triax is that it's makeup is generally 12 oz. in the longitudinal direction, and 5 oz. in each of the 45 degree directions. I like to build in more torsional stiffness and less longitudinal stiffness than the triax allows... that way, I get a ski with a softer, round flex that still hangs tough through hard turns... so I use my own recipe of bi and uni.
Oh, if you put your cloth layer on top, be sure to use a smoothing layer so you don't have to do a lot of sanding before applying the polyurethane coat. If you have to sand too much to get the surface smooth, you're likely to sand into the cloth layer, which could leave ugly spots. Ha, I used to put cloth inlays in my surf boards back in the 60's... what does that tell ya?
G-man
I use a lot of bi-axial and uni-directional in my lay-ups, and one thing that I notice is that the bi and uni layers are much more visible in the lay-up than the triax is... meaning that the fibers of the bi and uni glass don't turn as translucent when wetted out. So, if you want the best color from your cloth top sheet, I'd say put it on top of the glass layers, regardless of what glass you're using. I also like my glass layers to be adjacent to each other, without a none-structural layer (cotton cloth) disrupting the integrity of the lay-up. For me, the only disadvantage to using triax is that it's makeup is generally 12 oz. in the longitudinal direction, and 5 oz. in each of the 45 degree directions. I like to build in more torsional stiffness and less longitudinal stiffness than the triax allows... that way, I get a ski with a softer, round flex that still hangs tough through hard turns... so I use my own recipe of bi and uni.
Oh, if you put your cloth layer on top, be sure to use a smoothing layer so you don't have to do a lot of sanding before applying the polyurethane coat. If you have to sand too much to get the surface smooth, you're likely to sand into the cloth layer, which could leave ugly spots. Ha, I used to put cloth inlays in my surf boards back in the 60's... what does that tell ya?
G-man
Thanks for the reply. I was unaware of the weight of the glass in each direction. Now that it has been mentioned, I pulled the 0 direction glass out of a sample and did notice it was much heavier (thicker) that either 45 directions glass.
so what would be a good mix in order to achieve a better torsional stiffness? I like the even flex of the skis built in the past, but this core will be a bit thinner in an attemp to reduce the overall weight (Looking for a "touring" ski) and I believe I will need to increase the torsional rigidity because of that.
Again, Thanks much,
rockaukum
so what would be a good mix in order to achieve a better torsional stiffness? I like the even flex of the skis built in the past, but this core will be a bit thinner in an attemp to reduce the overall weight (Looking for a "touring" ski) and I believe I will need to increase the torsional rigidity because of that.
Again, Thanks much,
rockaukum
nice informations ! very usefull !
I was wondering if ther is any problem in not using a top sheet. When using only glass fiber + epoxy as a topsheet the upper edges of your skis are more exposed to scratches (and so, cuts in the glass fibers which could lead to core exposure) while your skis hit against each other. Maybe I only have this problem because I'm not a "top level" skier...
Do you add extra layers of fibers in this area (which will also stiffen your ski I guess) ou use Kevlar tape or anything like that ?
I was wondering if ther is any problem in not using a top sheet. When using only glass fiber + epoxy as a topsheet the upper edges of your skis are more exposed to scratches (and so, cuts in the glass fibers which could lead to core exposure) while your skis hit against each other. Maybe I only have this problem because I'm not a "top level" skier...
Do you add extra layers of fibers in this area (which will also stiffen your ski I guess) ou use Kevlar tape or anything like that ?
rockaukum,
I've played around with a number of fiber orientations and weights, and I guess what works best depends a lot on what you I plan to use the skis for. As an example, some of my favorite local backcountry areas are open slopes, and some of them are heavily treed slopes. In the tight trees where quick turns will keep me from hitting a tree, I like a ski that has a soft longitudinal flex so it will quickly make a tight arc when I crank it on edge and dump some weight on it. I like it to have low swing weight so it will come around fast when I need it to, and I like it to be wide enough to float in soft, often heavy conditions so that I don't have to fight a lot of snow weight on top of the ski when I'm trying to get the ski to transition and turn quickly (tele skier here). So, for this this type of 'touring' ski, I'm going to design the core pretty thin and kinda wide (125/95/115 ish), use minimal 0 degree fibers (might even leave out the uni above the core), lots of 45/45 fibers, and at a length of about 175cm (I'm 6 foot, 175 lbs). On the other hand, for a 'touring' ski for the more open slopes, (where I like to open it up and let the skis run) I'd build the ski with less side-cut, less width, more length, a bit thicker core (more longitudinal stiffness), and more 0 degree uni-directional fibers (again, more longitudinal stiffness). I'd still go heavy on the bi-directional layers because I can't think of a time that I'd want less torsional stiffness, regardless of condition. With this ski, I don't care about swing weight... I want stability at speed. I generally don't fuss too much about overall weight, cause I like the work-out on the climb, and I use 7tm tour bindings on pretty much all of my skis, which are a bit too much on the heavy side to be too terribly concerned about ski weight. As I indicated above,though, when it comes to swing weight on a ski that is intended to turn quickly, I do focus more on certain weight parameters.
So, overall, I'd suggest that you use your core design (thickness profile) to give you the longitudinal stiffness that you want. It is much lighter to stiffen a ski with a mm or two of core material than it is to stiffen a ski with added layers of glass. Try playing around with different combinations of bi-directional glass to give you the right compromise between performance and weight. I use bi-directional fabrics that range in weight from 9 oz. to 34 oz., depending on what I'm going to use the ski for. I personally don't see the need to use carbon fiber or titanal... just good ol' pine for damping and light weight, good ol' properly oriented glass for the structural skin, and proper core design for the rest.
Regarding your question of what would be a good mix to achieve better torsional stiffness... just about anything is going to be better than the 10 oz. bi-directional make-up of the standard 22 oz. triax... the heavier you go, the higher the torsional stiffness will be... kinda depends on how little uni you want to go with, which depends on how thick you want to make your core in order to make up for the stiffness reduction from reducing the weight of the uni. Did that make sense?.. it's getting late.
G-man
I've played around with a number of fiber orientations and weights, and I guess what works best depends a lot on what you I plan to use the skis for. As an example, some of my favorite local backcountry areas are open slopes, and some of them are heavily treed slopes. In the tight trees where quick turns will keep me from hitting a tree, I like a ski that has a soft longitudinal flex so it will quickly make a tight arc when I crank it on edge and dump some weight on it. I like it to have low swing weight so it will come around fast when I need it to, and I like it to be wide enough to float in soft, often heavy conditions so that I don't have to fight a lot of snow weight on top of the ski when I'm trying to get the ski to transition and turn quickly (tele skier here). So, for this this type of 'touring' ski, I'm going to design the core pretty thin and kinda wide (125/95/115 ish), use minimal 0 degree fibers (might even leave out the uni above the core), lots of 45/45 fibers, and at a length of about 175cm (I'm 6 foot, 175 lbs). On the other hand, for a 'touring' ski for the more open slopes, (where I like to open it up and let the skis run) I'd build the ski with less side-cut, less width, more length, a bit thicker core (more longitudinal stiffness), and more 0 degree uni-directional fibers (again, more longitudinal stiffness). I'd still go heavy on the bi-directional layers because I can't think of a time that I'd want less torsional stiffness, regardless of condition. With this ski, I don't care about swing weight... I want stability at speed. I generally don't fuss too much about overall weight, cause I like the work-out on the climb, and I use 7tm tour bindings on pretty much all of my skis, which are a bit too much on the heavy side to be too terribly concerned about ski weight. As I indicated above,though, when it comes to swing weight on a ski that is intended to turn quickly, I do focus more on certain weight parameters.
So, overall, I'd suggest that you use your core design (thickness profile) to give you the longitudinal stiffness that you want. It is much lighter to stiffen a ski with a mm or two of core material than it is to stiffen a ski with added layers of glass. Try playing around with different combinations of bi-directional glass to give you the right compromise between performance and weight. I use bi-directional fabrics that range in weight from 9 oz. to 34 oz., depending on what I'm going to use the ski for. I personally don't see the need to use carbon fiber or titanal... just good ol' pine for damping and light weight, good ol' properly oriented glass for the structural skin, and proper core design for the rest.
Regarding your question of what would be a good mix to achieve better torsional stiffness... just about anything is going to be better than the 10 oz. bi-directional make-up of the standard 22 oz. triax... the heavier you go, the higher the torsional stiffness will be... kinda depends on how little uni you want to go with, which depends on how thick you want to make your core in order to make up for the stiffness reduction from reducing the weight of the uni. Did that make sense?.. it's getting late.
G-man
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thetradwoodboat
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g-man, i just wanted to say that i think your opinions on glass, weight, core, side-cut and stiffness are right on!
i've only been at this ski building for three seasons (10 pair), but i couldn't agree more. i have moved toward using triax and a light layer of biax above and below the core, the weight difference is minimal and my skis are still lighter than any production model. i think core profiles are really important to a ski's performance. i'm enjoying soft tips and tails these days for all my new england tree skiing.
i'm wondering if you would elaborate on what you know about core materials relative to dampness. i haven't tried pine yet. it does seem like it could be a damp option.
nate
i've only been at this ski building for three seasons (10 pair), but i couldn't agree more. i have moved toward using triax and a light layer of biax above and below the core, the weight difference is minimal and my skis are still lighter than any production model. i think core profiles are really important to a ski's performance. i'm enjoying soft tips and tails these days for all my new england tree skiing.
i'm wondering if you would elaborate on what you know about core materials relative to dampness. i haven't tried pine yet. it does seem like it could be a damp option.
nate
Nate and x8rider,
I've been away 'ski testing' again. Regarding my opinions of core materials, the reality is that I really don't know much that anyone should take very seriously. Like many others on the site, I'm just a ski junky who likes to make stuff.
But, I must admit, I just love the way my pine core skis ride. Once in awhile, I'll jump back on a factory ski (one of my old skis, or trade with a friend for a more current model) for a run or two, and I always just can't wait to get my home-builts back on. On firm/icy conditions, factory skis seem to ride 'harse', which I'm assuming is from a lack of efficient damping. I just don't get that harshness with the pine cores. Maybe it's a 'placebo' effect, cause I built them. It would be interesting to get more feed-back from other builders who have used soft wood cores. It does seem that most of the discussion regarding efforts to increase damping characteristics (by using titanal, more VDS, etc.) is from builders who are not using soft woods in their cores. At this point, though, I must emphasize that all of my opinions are totally subjective... which is really quite okay cause I'm mostly trying to just have fun, which, mostly, I am.
G-man
I've been away 'ski testing' again. Regarding my opinions of core materials, the reality is that I really don't know much that anyone should take very seriously. Like many others on the site, I'm just a ski junky who likes to make stuff.
But, I must admit, I just love the way my pine core skis ride. Once in awhile, I'll jump back on a factory ski (one of my old skis, or trade with a friend for a more current model) for a run or two, and I always just can't wait to get my home-builts back on. On firm/icy conditions, factory skis seem to ride 'harse', which I'm assuming is from a lack of efficient damping. I just don't get that harshness with the pine cores. Maybe it's a 'placebo' effect, cause I built them. It would be interesting to get more feed-back from other builders who have used soft wood cores. It does seem that most of the discussion regarding efforts to increase damping characteristics (by using titanal, more VDS, etc.) is from builders who are not using soft woods in their cores. At this point, though, I must emphasize that all of my opinions are totally subjective... which is really quite okay cause I'm mostly trying to just have fun, which, mostly, I am.
G-man
So I went head and pressed the skis yesterday. I did not use the plastic top sheet and went with this set-up.
Base
Triaxial glass
Core
Biaxial galss (19 oz)
Cloth
Took them out this am and did the rough trim. they weigh in at 4# 4 7/8oz.
They seem very soft tip to tail but I have not flexed them yet. plan on letting them sit for a few days...
I will post some pics and a breif write up soon.
rockaukum
Base
Triaxial glass
Core
Biaxial galss (19 oz)
Cloth
Took them out this am and did the rough trim. they weigh in at 4# 4 7/8oz.
They seem very soft tip to tail but I have not flexed them yet. plan on letting them sit for a few days...
I will post some pics and a breif write up soon.
rockaukum