Friday, April 27, 2012

AMH-12

RECAP

The skis I made last year seem to have done well.  My brother has spent time skiing the Panjshirs at Crystal Mountain in the state of Washington.  The Arlias have seen east and west coast skiing and have performed well.  A pair of the Arlias even survive falling from the roof of a car onto the pavement at high speed. ( http://mwallworkrn.blogspot.com/2012_02_01_archive.html ).








I continued to use my Goliaths in the backyard and took the tomahawks to the slopes.  To date none of the skis I have made have failed and only a single Goliath V1 edge has torn out (I have corrected this problem).

2012

This year I decided to make only a single pair of skis. I want these skis to be good for east coast skiing, where I live, but also have the ability to take on big mountain snow. Additionally, I wanted the ski to be relatively light to take on backcountry trips. I have temporarily named the ski the All-Mountain Holuta (AMH-12).

The ski dimensions are 127-88-109 and 186 cm long.  Additionally, the ski has tip and tail rocker, camber, and reverse side cut at the tip and tail. The rocker will allow for easier powder skiing while the camber will allow for good edge grip on hard-pack. The reverse side cut at the tip and tail shortens the turning radius of the ski from ~21m to 17.7 m.  This will allow for quicker turning despite the length of the ski.  The reverse side cut will also lighten the ski and allow for smoother maneuverability in deep snow.  The ski was lengthened over past years (186 vs 181 cm) since the rocker shortens the contact length of the ski.  Adding a few centimeters to the length re-lengthens the contact length.  The final design is below:



In order to make the skis light, I am using Aspen, Poplar and Oak in the core.  Several 5mm strips of oak spread through the core serve to provide ample stiffness to the ski while filling the gaps with aspen and poplar lightens the ski.  Oak is not frequently used in skis, and I'm not entirely sure why.  It is a little expensive but it is very hard and stiff.  Oak is also stronger than the majority of commercially available woods.  The hardness wears out tools more quickly which may be why it's not used commercially.  I am also planning to add two oak rails to the top of each ski; this rail will significantly improve stiffness and edge grip. A preview of the core is below:


I have also started making the templates.  Similar to last year, I have three templates: a base, rough core, and core member template; the use of these templates will be explained later.  To make the templates, I had the designs printed full size and then used spray glue to attach them to high density fiberboard that I purchased.


The templates are then cut out and are ready to shape the ski.

3 comments:

  1. Great job Jon- looking forward to skiing with you and Matt and Cooley inFeb 2013 at Crystal. Ski deep and steep and the trees or don't ski.

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  2. Great skis, can't wait to hear how you like these Aftermath. I'm in the process of designing my first skis, and one issue has occurred to me. If the core is cutout to the shape based on the top-view of a drawing, once pressed into the profile shape (camber/rocker) it will be slightly shorter than designed. Do you use your CAD to flatten your design and get a true core size shape, or just not worry about the small loss in length?

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    Replies
    1. Andy, I typically assume 2cm longer for my designs. For example, the CAD drawing for the Aftermath shows 188cm, but is advertised as 186. I think this was based on measuring a pair of skis when I first started, but it's really up to you. I skied the Aftermaths at Jay Peak, VT this past week for 4 days. The skis were fighting against me when I was turning the first day so at lunch I detuned the edges on the rockered portions of the tips of the skis. After that change, they skied very well and I used them all week.

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