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Wax Test-6th Grade Science Fair Project

post #1 of 21
Thread Starter 
Despite trying to convince my kid to do something like powering your iPod from an onion & electrolytes for a project, he decided on ski wax for some reason.

Yesterday, versus fighting Xmas crowds on 'OK' snow, we opted to tour over to our 'test track' hauling a tuning stand, supplies, tools & alpine gear. We had scoped this out two days prior and ski packed it to let it set up for a couple days. This being first phase of three to test three wax temps at various temperatures and conditions. We used Maplus P1 sprays which are easy to change on site, especially with the stand. Eliminating/reducing variables was the key to the focus of the project so we were hopefully down to the wax as the only substantial variable.

With the snow temp at -2°C/28°F (which changed to -1°C/30 by the test's end), the little guy ran a 6° slope for 113 ft/34.4 m) to get a minimum of 3 times per wax. The procedure was for him to position himself at the start, on flat skis and supporting himself with his poles. He would say 'go' when he released his poles & 'stop' when he crossed the finish while I timed him. He'd then duck walked/skated up the track in an attempt to be consistent with the surface from run to run. I'd use BioCitron wax remover scrape/brush/spray/cork/wait ten minutes/brush exactly the same for each wax.

We easily got 3 'consistent times' for the Cold, then Medium waxes, with the Medium the fastest, as expected by 1/10 second for the distance and slope.

The perplexing part came with the Hot. With an overlapping design temp with the Medium, I expected he'd be close to the same times. It turns out his first run was the fastest of the day (must've been the brushing , and he knew it at yelled as he finished almost 1/2 sec faster than previous times. After that he ran his two slowest, 2nd fastest and comparable runs to the medium and cold. : : We ran six times as double checks to see if we were not consistent somehow. FWIW, the average of the middle times and all times were close to the same and right in between the Medium & Cold.

We're not sure why we were all over the board with this test series, the last one. Tester fatigue and the start ('sticking') are our first guesses. Any suggestions for further minimizing variables would be appreciated for the next two (or more) phases. One simple option, is to get him moving for ten feet or so before the start line and then hit the timer. Another is start on a steeper slope.

Assuming 'this thread is worthless without pictures':

The tester, his skis & track in the background.

Hitting the brakes after hitting warp speeds up to 7.7 mph/12.4 kph

FWIW, the gear sled.
post #2 of 21
I love the gear sled pic.

Maybe next year he can try powering his waxing iron with an onion
post #3 of 21
Thread Starter 
We'll need a gigantic onion and gallons of Gatorade. :
post #4 of 21
do I understand correctly: six runs on hot
1 fastest (presumably after brushing)
2 slowest 1
3 slowest 2
4 2nd fastest
5 comparable to medium
6 comparable to medium

post #5 of 21
Nice work! I can't think of any practical suggestions, but if there were some way to reduce the problem to a repeatable test without a "human" factor and without the effects of a changing course, that might help. I wish I had good ideas on how to do that. I can envision a lab scenario where the ski is the incline plane and a suitable test object is slid down the ski and timed between two points.

How do test labs determine the coefficient of friction of various surfaces? That might be a starting point, to duplicate on a simpler scale.
post #6 of 21
Too much confusion and too many varables.

You have two "equal" skis .....

Strip then and just use "Wax A" .......... and the other ski with ...... "Wax B" ........

Decrease the slope and/or increase the distance.

Run the skis down a string line (rig them with a couple of eye hooks), so they follow about the same path over about the same track each time.

Get rid of the brushing and other stuff between runs. One prep whatever you are going to do to the ski ....

Increase the number of runs alternating between "A" and "B" so that "course" conditions and temp changes get "laundered out".
post #7 of 21
Thread Starter 
Originally Posted by comprex View Post
do I understand correctly: six runs on hot
1 fastest (presumably after brushing)
2 slowest 1
3 slowest 2
4 2nd fastest
5 comparable to medium
6 comparable to medium

Hot wax runs on same line (+/- inches)
1 (9.99 sec) fastest (after brushing and possibly warmer skis)
2 (10.42 sec) comparable to MEDIUM's median
3 (10.51 sec) comparable to COLD's median
4 (10.81 sec) 2nd slowest
5 (10.19 sec) 2nd fastest (he appeared to be in a lower crouch than typically)
6 (11.06 sec) slowest & looked it :
7 (10.48 sec) median for HOT

I wondered about removing the tester, using less weight, more distance, etc, but that also removes some of the fun factor. It would be interesting to just spray and run on a string, though. Skiing is full of variables....especially the skiers (couldn't possibly be the waxer). :

It was pretty easy to at least think I was being consistent with brushing and waxing etc. The first two temps were very consistent (within 1 to 3 tenths each run) which makes it seem like any variation was neglible....but the high variability of the HOT times were after brushing and relative to their runs and those procedures. Heck, maybe my wrist stop watch is a variable.....along with a couple frozen elk poop pellets....
post #8 of 21
No doubt your wristtop IS a variable!
post #9 of 21
Thread Starter 
Maybe I can get a grant for one of these ::

I'm sure there is an inherent variable with any human operated stop watch. I can't imagine that my reactions, slow as they are, could by itself substantially influence a spread over a second in times. Could be a factor though and picking up a decent, low cost stopwatch wouldn't hurt. On first blush, they can range from $10 to $100 and more. Are the el cheapo ones even worth a consideration, especially for basic timing purposes?

I need to consult with the boss, but upon further consideration, lining up 3 or 6 same skis starting simultaneously, might be best overall. I don't think that over any distance a string or cord will keep a ski in line, though. Maybe a series of tensioned cords with pulleys and prussiks, might (and a PITA). A tensioned cable sounds over the top. I have a medieval classic track setter I made which could be handy, but then side friction would come into play in the tracks.
post #10 of 21
The more skis you add to the test the harder it is to validate the results.

In stats, the magic sample number used to be "25" for the most basic project.

If 2 skis each made 25 runs down the same string line (alternating to wash out temp variation), you would be able to wash out some of the timing issue.

Just discipline yourself to wield the timer. Kid at the top hollers ... ready .. and you start it when he says "go" .... then ... you ... stop it as it crosses the "line".

KISS ... and I ain't talkiing smoochin !!
post #11 of 21
Thread Starter 
Since this is about learning 'The Scientific Method' and not necessarily 'perfect' data, hopefully I can leverage that to enforce the fact the 'fun factor' is not the priority....though if we can combine both, all the better. (Plus, it's supposed to be him dreaming up the tests. : )

I have been wondering how many runs will be needed for reliable results, but since we are planning on three different snow temperatures with the three waxes, it'll get pretty brutal trying to get that many results (3x3x25).

Seems like a longer time & distance with possibly a shallower slope & slower speeds would moderate the little differences like timing, starts, brushing (or not) etc. and wouldn't necessarily need a zillion runs. I time from the bottom when he lifts his poles and stop at the finish. (Picked up a stop watch today).

A couple other musings include scoring two pair of rentals and prep them the same except for the final wax. (Might even consider using the fourth ski with Universal just for grins). Let all go at the same time and record who winds 'x' numbers of heats. Rather than string, I'm wondering if rounded troughs would work as reasonable test tracks.

Thanks for the input and ideas.
post #12 of 21
Nothing wrong with doing a low scale basic test. But, one of the concepets ..... not really get technically get into it ... just introduce the concept ....

Just show on paper how the level of confidence would go up if you increased the sample ... that is, the number or runs.

Also, to introduce the problems encountered and how they were solved or at least modified to make the wax test less reliant on other variables.
post #13 of 21
Thread Starter 
FWIW, I discussed the issues as I see them, including more runs for better averaging, with the boss and he just toured around for a mile or so, looking for suitable alternative runs. The fun factor and him gliding is a given.....for now. He gets the averaging and the need for more times, but physical endurance and time are considerations. The initial test track is still considered our best/most convenient alternative as it is in the shade with a NW aspect and should maintain more uniform snow temps longer than those in sunny areas. I'm heading out to pack a longer section and our plan is to:

1) Extend the length of the run 30 or 40 feet.
2) Start moving first (10 feet or so), with him calling out 'start' or 'go' as he hits the starting line.
3) I'll be at the finish with the stop watch.
4) We will only spray wax and cork, then wait ten minutes for wax hardening.
5) He'll do one run after waxing which will not count to even out the ski bases and temperature.
6) He'll run (5) times per wax to increase the times for averaging. :
7) He'll focus on maintaining consistent body position, line, flat skis and tracking during his runs. I'll set up a visual target.
8) We'll bring more energy food and drinks to keep the mojo up and hopefully moderate fatigue. :
9) This will be repeated twice more at different temperatures and days over the next few weeks. :
10) The dogs, much to their dismay, have been removed from their duties as course inspection staff and tester chasing.
11) We'll be consistent on track prep between runs and waxings.
12) If things don't seem right we will adjust the testing and still consider removing more of the 'human factor' and any other 'substantial' variables than become apparent.

Hopefully, these tweaks will be suitable enough for reasonable accuracy.

post #14 of 21
How is he starting. It should be in the same spot.

It should not rely on a push of the poles. He should be holding onto something with gravity ready to do the job and just have to let go. Tie a length of cord to a tree behind him .. he just hangs on till you holler release.

I would .... "fix" the skis together so that the rider/pilot/crash dummy, can't induce any edging or wedging.

A simple duct tape job .... not a hard "bound & wound" may be the ticket to reduce this variable.

Something simple like a flat paint stir stick taped to the upper surface front and rear. It is taped at a marked point ... use masking tape to mark the fixed points .... if the duct tape is broken prior to passing the timing mark the run is scrubbed ... rider has induced edge or wedge?
post #15 of 21
Thread Starter 
I packed out an area close to 200 ft plus a run-out with a curve. One thing that was evident for the previous attempts and not previously noted was a slight right bend to stay out of an adjacent elk trail. I straightened out the line. (Hopefully, the elk will understand this and stay off to the side.

Introducing a 'fixed' ski isn't appealing from a PITA, time and safety factor. I'd think it'd also introduce a 'psychological factor', worrying about not having free motion. Checking out our KUU Tip Straps with releasable velcro & quick clips could make the fixed skis approach easier to deal with (front & back), but a narrow stopping area with steep sides and trees would make me nervous if I was doing it, much worse watching my kid. 10:1, mom vetos that one.: Plus, I'd have to visual see whether or not the straps (or tape, etc) were still connected as he's flying by the finish. We'll see, I guess. Seems like I'd have to assure a very even & buffed out run to also make sure the fixed skis approach is without influence versus assuming multiple runs moderate subtle differences

Previously, he was very good about releasing the poles and not pushing with them, but setting a fixed start and release is easy enough and coupled with waiting until he is moving past a start mark would hopefully moderate any substantial start variations.
post #16 of 21
Sounds good Terry, let us know when the next round of data is in!
post #17 of 21
With all the possible variables you have, you will need to increase the number of test runs you do. This will increase the fun factor but also increase the work/effort factor.

Even with limited variability 20 test runs give you a population that can be statistically evaluated. I would at least double that. I would not worry about "servicing" the skis between runs. instead I would do 5 un-timed runs to "condition" the skis. Any good wax job should hold up to the limited "vertical" you are putting it through.

The key to evening out the affects of variables is do more tests.
post #18 of 21
And remember to weigh him before and after each run.

No snacks, sandwiches, hot drinks or potty calls during testing.

Weight of the crash dummy will be strictly monitored.
post #19 of 21
Thread Starter 
Today's data:

Distance: 148', Slope 5 to 7°
Packed, transformed old snow
Snow Temp Start: -8°C/18°F; End: -6°C/21°F
12/30/07 12:00Pm 12:45PM 1:30PM

P1 Hot Medium Cold
Design Temp 0° to -3°C -2° to -9°C -8° to -22°C
32° to 27°F 28° to 16°F 18° to -8°F
Run #1 (wax) 10.10 sec 9.81 sec 10.88 sec
Run #2 10.06 sec 9.71 sec 10.41 sec
Run #3 9.75 sec 9.93 sec 10.32 sec
Run #4 10.40 sec* 9.87 sec 19.75 sec
Run #5 9.75 sec 9.75 sec 10.00 sec
Run #6 9.90 sec 9.87 sec 19.94 sec
Run #7 9.97 sec 9.75 sec 19.79 sec
Run #8 9.93 sec 9.53 sec 19.75 sec

Total 79.86 sec 78.22 sec 80.84 sec
Average 9.98 sec 9.78 sec 10.11 sec

2 thru 8 69.76 sec 68.41 sec 69.96 sec
Av 2 thru 8 9.97 sec 9.77 sec 9.99 sec

w/o hi or low 59.71 sec 58.76 sec 60.21 sec
Av. w/o hi/low 9.95 sec 9.79 sec 10.04 sec

-Tried 200 feet but it was too fast for safety and the stopping area and we reduced it to 148'. Steeper start than previous test, increased speeds and reduced times.
-spray waxed and corked. (No scraping or brushing after waxing.) After five minutes put skis on snow, in shade, with bases up to cool to snow temp for 5 more minutes
-Tried the release method of fixed straps and stakes, but it added a conflict with poles. We decided supporting the start with his poles, releasing and yelling 'go' while moving through start line worked easily and seemingly consistently.
-* time was definitely influenced, at least in part, by a too quick timer start
-a squall came in towards the end of the medium test, changing wind direction, air temp and covered the sun for final (cold) waxing
-my sense is that brushing would definitely have increased the initial speeds/shortened times of the cold wax (harder wax) test. Next test series I plan to brush as the first one, with brushing, as it did make for more consistent times with the cold & medium temp waxes.

FWIW, aside from the chatter, this is a 14MB clip from a typical run.
post #20 of 21
Oh! Does the crash dummy know what wax he is running on?

Tape white paper on all of the containers so he can't see what he is running on.

Actually ........ as a "control" .... you could be sneaky and tell him he is running the "fast wax" ... when it's actually the slowest to date.

Now .... that may be the actual highlight of the whole experiment ... the illustration that the results may be influenced by the anticipaition of the tester ... should the slowest suddenly become fast over a series of runs.

That ... would be "science in action" ...
post #21 of 21
Thread Starter 
Just realized I botched the editing of the results. These were the proper times:

It seems pretty obvious that as the cold layer got 'scraped by the snow', the speed increased. More times sure would have helped here. Brushing would have been quick and easy to be consistent with. Talking to a nord friend regarding this test and proper techniques, he said that extra brushing and care is typical for colder waxes......

FWIW, the little shredder was not aware of 'the fastest wax', but rather attempted to be as fast as he could on each run.
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