Ski Builders Forum

Photobucket with re-size and rotate these at somepoint ...

There's a lot of focused content in the forum at the moment, so I thought it would be good to add something to this thread. Different way of doing the same thing ... but I would appreciate the feedback.

This is the basic frame - bolted to the floor. Clamps allow for change in centre of the ski, when commercial skis are measured. I regret not creating a longer rail for the shuttle, but it was going to be tricky to achieve:



The shuttle is moved up and down the rail using a hand-drill - it sits on a platform, so as not to stress the thread and twist the shuttle.



The position of the shuttle is referenced against this paper scale which is stuck to the base (double sided tape)



The test starts with the force cell in place and readings are taken:

- no force applied
- force required to neutral position
- 10 kg
- 15 kg
- 20 kg
- 25 kg

Rest 0kg 0mm Total Displacement
Neutral 3.8Kg 7.48mm Total Displacement 7.48 Change in mm
10Kg 18.86mm Total Displacement 11.38 Change in mm
15Kg 29.1mm Total Displacement 10.24 Change in mm
20Kg 37.29mm Total Displacement 8.19 Change in mm
25Kg 45.8mm Total Displacement 8.51 Change in mm

What's interesting is the none liner relationship between force and displacement.

The force cell is then removed - no point leaving it under pressure and measurements are taken every 10mm



The shuttle is relatively simple - held in place using plumbing parts and plastic edging strip







Accuracy level appears good - as the results are repeatable to within +/- 0.05mm

This is what I have set up for focused tip deflection force cell is not in place in these photos:





What's interesting about the results I am getting is they are based on the same ski built differently, so the results compare these changes e.g. 20 cm more CF, an addition 0.1mm in overall height of the core or capped v.s sandwich.

The machine is four processes within the one frame - I would think it could have been made more simply, hopefully it will offer a few ideas to others.

Nice Rich! Will you be publishing your test results? Can you explain exactly how you're measuring and recording results for each test being performed? In the 6th pic it looks like you're flexing the ski downward by a threaded rod attached to a drill. Are you capturing the force applied by the amount of the ski flex? And how do you know the amount of force applied?

That's quite a rig!

Thks SD (It look me a while to work it out - but all the parts are simple,cheap and available) I'm using a force cell SD - it was off-the-shelf, pulled from a set of scales.



My graphs are laid out quite simply, just like White Thrash.

The first set of photo's show the set up for the ski supported at tip and tall. The paper scale is attached to the base of the ski. The tip is treated as zero - micrometer set to zero. The shuttle is then moved to the middle of the ski and measurements taken every 10mm. It's done this way round because otherwise the micrometer is pushed against the ski as it travels towards the centre.

The second test you have pointed at examines the tip in more detail. In particular the points at which the flex pattern has increased by 1mm, relative to the previous point. So its a matter of taking reading for the first 10cm @ 2.7mm thick, then maybe 22cm @ 3.7mm, then maybe 25cm @ 4.7mm and so on. Make sense?

The third test is a torsion rig, using weights and an inclinometer. Fourth is fatigue. I'm not kidding myself, there's a fair way to go - real life results would be nice:

http://www.wired.co.uk/news/archive/201 ... of-surfing

If we could set up the circuit for these: http://www.imagesco.com/sensors/flex-sensor.html , we'd all be well on our way. Struggling to find anything 'open source' to record the results? HAHa ... only watched the video, the article contains a few links : ) Brother-in-law is going to get a call tomorrow )))

Yup makes sense. Serious work....

First, in the early6 70's my favorite ski was a 180 cm Kneissel Short Star. I believe the tail was stiffer than the tip and it was perfect for bottomless powder and handled the piste well also. For the past 30 years I have skied skis with only 6" behind the boot and are 110 to 130 cm long. I have built 6 pairs over the last 4 years and compared stiffness with a very simple method. Clamp the ski to a flat bench at the toe position and lift the tip 1" up. I use a fish scale to measure the resistance. I have found that 12# is fine for powder but not good on the pack. 22# is too stiff for anything. 16 to 19# seems to be fine. My favorite ski that I used in the Dolomites for a month in '10 and used at Alta and Snowbird for 5 weeks in '11 is 127 cm with 7" of tail behind the boot. It measures 19#. There is no camber or sidecut and tip tail is 11.1 & 9.3.

frank I hate to tell you but those are not really skis per say as much as they are snow blades or snollerblades, unless of course you are a midget or little person or a child so the flex numbers proly dont apply to larger skis I would have to gather.

I will ignore MM's immature derisive comments. The commercial version of my skis have been marketed under the trade name Scorpion and most recently Bstinger. Technically, they are a form of skiboard. Several thousand have been sold in the US over the past 30 years. FYI, I am 6'3" tall and weigh 220 lbs. and last season I was allowed to pay Alta Ski Corp. only $45 dollars for my season pass. Alta had record snowfall last season and my short but wide skis worked perfectly in the powder and crud left by first tracks. I kept asking the Bstinger dealer to market a larger version for larger people and when I discovered this site, I decided to experiment on my own. I have built 5 pair and plan 2 more for this season. Flex is very important in any sliding device and my simple method lets me relate known performance on the skis with which I am familiar. The actual numbers do not relate to other skis or boards. For the fun of it, I took a relic pair of 215 cm Head 360's off the wall and their flex measured 16#. Right in my ball park. I used them at Alta in the late 50's where and when you could ski first tracks all day long. I would be curious how the fat boys and bananas check out but there are no ski shops within 2,400 miles of where I live. Remember, as with snow and many other things, it's not how you do it, but how you enjoy it.

how are there no ski shops within 2400 miles where you live are you in Africa? They make skis in tunisia and some other african nations.
Im not being immature I'm just saying, like you said, your numbers don't really apply to anything we do. Dont get your depends in a bunch.

Dont get your depends in a bunch.

Easy for you to say Mr. Madman. 'Dem damn Depends seem to bunch up no matter what I do.

Just sayin'...

G-man

This site is always dependable.