Build your own skis!

A good backcountry ski is fat and light. Maybe you could make air channels e.g. Tua Helium, or use lower density wood species.

<br>zenom -- i agree: fat and light. surprisingly, our homemade contraptions are fairly light, even for their width. materials such as wood, standard p-tex, metal edges, fiberglass and epoxy are relatively light. maple is hard and relatively dense, but mixing poplar makes the skis lighter. but, when we start using metal (such as Titanal) the skis may weigh more.<br><br>

What bindings are you using on the fatties? How much does it cost in materials to make a pair?

<br>the bindings we're using include: Hammer Heads, G3 Targa with stiff and ridiculously stiff springs, Black Diamond O2 and Black Diamond 03.<br><br>the cost of materials is estimated between $100-$130 per pair. the estimate doesn't include metal or exotic layers, for example, Kevlar.<br>

what can we say. we love to ski! and it naturally lead to making skis in the garage.

<br><br>Haha, this is a classic line. Natural for a couple of engineers maybe. Great site guys!

The core doesn't need to be much, that's why many skis use foam. I prefer wood core. The ski stiffness comes mostly from what's surrounding the core. If I were making a ski, I'd router or kerf the wood core to remove mass where it's not needed. Poplar has a higher MOE/SG (modulus of elasticity/specific gravity) ratio than maple (2.95). From a quick look, it appears that port orford cedar, silver fir, or noble fir (4.41!) have an even better MOE/SG ratio than Poplar. I'd be happy to give you more technical info if you want. <br><br>Regarding the bindings, do you see much difference between a beefier binding on a fat ski like the Hammer Head, or a G3?

The core doesn't need to be much, that's why many skis use foam.

<br>actually, i've found that the core does make a big difference. (i'm not sure what kind of foam is used for skis, but it probably has similar properties as wood. isn't foam cheaper? rumors say it breaks down faster than wood.) anyway, i think the majority of a ski's flex is determined by its core; the flex depends greatly on the dimensions of the core and its profile. this is probably the case because the layers of fiberglass that we use (2 layers) is relatively thin.<br><br>

I prefer wood core.

<br>i like wood too. wood has a very nice feel. i think i like it because it is damp, but at the same time, snappy.<br><br>

The ski stiffness comes mostly from what's surrounding the core. If I were making a ski, I'd router or kerf the wood core to remove mass where it's not needed.

<br>an interesting topic. i don't know the answer. the only thing that sticks out in my mind is the following: the natural frequency wn of a simple spring-mass system is:<br><br> wn = sqrt(k/m); where k = spring constant and m = mass.<br><br>seems like there are two parameters to play with. for me, a light ski (small m) doesn't feel very solid, like it chatters and vibrates a lot, especially in hard and variable conditions, at high speed. this makes sense as small m makes wn large.<br><br>

Poplar has a higher MOE/SG (modulus of elasticity/specific gravity) ratio than maple (2.95). From a quick look, it appears that port orford cedar, silver fir, or noble fir (4.41!) have an even better MOE/SG ratio than Poplar. I'd be happy to give you more technical info if you want.

<br>i'm not familiar with MOE/SG ratio. what does it mean, exactly?<br><br>

Regarding the bindings, do you see much difference between a beefier binding on a fat ski like the Hammer Head, or a G3?

<br>i feel that a beefer binding helps to drive a fatter ski. stiff boots help too.<br>

The original powder specilists at ALta took thier wooden skis and had them planed to a wisp.<br>Dolores Lachapelle : <br> from <br> "Deep Powder Snow: Forty-Years of Ecstatic Skiing, Avalanches, and Earth Wisdom" <br>by Dolores Lachapelle (Paperback - June 1, 1993) <br><br>I'm of the opinion that in true powder, edges and side cut are not that important.Fat and soft flex is what I like. <br>cool site !<br>

Kam,<br><br>MOE/SG. Pull out your Mechanics of Materials texts for a more technical answer, but here's my TAY answer.<br><br>MOE = the slope of a stress strain curve in the elastic region. Could be thought of as stiffness.<br><br>SG = specific gravity. It is density relative to water. So if your SG is 1.0 you'd be suspended in water and weigh 62.4 pounds per cubic foot. Could be thought of as mass.<br><br>Basically, I was showing which wood species have high stiffness but low weight. (Actual composite, or peice of material, stiffness is function of material MOE and geometry. Geometry is very influential.) You were considering the same and noting that is the natural frequency, wn. I'm not sure I concur with your wn assesment and effect on ski performance. I have very light pair of Tua Titans, which are pretty stiff (wood core with air channels, but with titanal at top and bottom). I have never had these chatter, and they'll bust through crud at high speed. I attribute their good performance to high bending stiffness and high torsional stiffness. They're great for backcountry because they're light. I've had crappy Black Diamond foam core skis chatter like crazy - they weren't very stiff either.<br><br>My comments about the core not needing to be much are based on the moment of inertia and whatever it's torsional equivalent is called. Again, pull out your Mechanics of Materials text. The materials that contribute most to bending and torsional stiffness are those located furtherest from the cross sectional centriod. These concepts are real and used in design of structural elements, including skis. You don't often see a layer of titanal used at the ski neutral axis. Engineered wood products are the same. The best laminates are placed furthest from the core. The worst are placed at core (nuetral axis) - to achieve highest strength and stiffness of the composite. <br><br>My profession is as structural engineer. My expertise is wood, engineed wood products, and even FRP-wood composites (carbon, aramid, fiberglass). I could go on and on but won't for hopefully obvious reasons. I have a lot ideas about ski design, and can even get you very select wood veneers if needed. Hopefully we'll talk more in person or email sometime. <br><br>Robie brings up another good idea. How about just laminating select thin wood veneers. If it wasn't torsionally stiff enough then add oriented fiberglass. <br><br>A final note. I notice the Bro model uses a layer of rubber as one of the laminates. Interesting. Lot's to try and ski...<br><br><br><br>