Another ski option

[Sheetmetalfab]

I built this thing to try on my purpose built Snowbike about a year ago.
Never mounted it since i had a yeti ski.
Just put it on my gasgas with 14 st.

Its way more predictable on hard crusty than the Timbersled ski.
(Better than the yeti ski also obviously)

Turns while leaning hard over are much smoother and it seems nearly impossible to wash out. *haven't had it in the deep yet

 

[Sheetmetalfab]

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[Sheetmetalfab]

One gripper ski with all the topside shaved.

One original Timbersled ski (simmons gen 1) split in half and bolted on each side.

Totally ghetto looking and heavy.........
Rides soo sweet.


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[Kaarlonen]

That is how a ski should look like.
It has center keel type profile
It has off the shelf carbide runners.
It has tried and true working base for a ski.
It has construction that could be easily scaled to many needs.

I think ski profile should be something similar if one wants to get good performance both on and off trail.
First there is that narrow center keel with runner for hard packed snow on trail where the keel doesn't need to be tall to get grip.
Second there is wider actual ski base to get the ski going on top of the snow but still not too wide to make leaning difficult.
Third there are wings with offset from the main ski surface to get lift in soft snow and second set of runners to get more bite when leaning over.

Yeti ski has massive keel or almost three keels with aggressive runners so in powder it works like magic but on trail it is maybe too aggressive.
We'll have to see how the new 2018 ski works.

TS ski is kinda same shape but less rounded profile and less pointy and aggressive keels/runners so it has better manners on trail but less performance in deep snow. (Again how is the new ski working? anyone?)

This is pure speculation and some educated guessing but I think the reason your ghetto ski works well both on and off trail is those three planar surfaces offset from each other. A bit like powerboat bottom.
There is a reason they are shaped like they are. In a planing boat the lifting surface dynamically reduces in size as speed goes up - bottom of the boat sees the water as a harder medium to get through so the boat lifts upwards because it needs less surface area to keep it self planing.

Now if we move from water to snow we cannot use fluid dynamics, but same principles apply in some ways. In hard packed snow ski needs less surface area to stay on the snow than it needs in powder.
(Like if hardpack was water moving faster against the boat and powder was water moving slower against that boat).
When running somewhere between soft and hard snow ski needs greater surface area than on hard packed snow but less than on powder.
(Here comes the need for dynamically self adjusting lifting area.)

If we eyeball yeti or TS ski they both have center keels and runners on the edges but horizontal surfaces that provide lift are all on same level so ski is using all or none of that surface. There is no dynamically chancing surface area depending on lift force the snow provides.
Yeti ski has tall keels to provide stability and bite in the deep but on trail those keels bite too hard and deep into the trail. That is because there is not enough surface area in the tip of the keels to keep them on top of the snow so they dig in until the lift area of the ski hits the snow and stops them going farther.
TS ski acts similarly but its keels are shorter so they do not dig into the trail so hard and ski is easier to control.

If we build ski with correctly sized multi planar surfaces to get dynamically changing lift force and keel bite from different snow conditions we can use tall keels for good deep snow performance and still drive wind blown crusty trail with ease.

 

[Hawkster]

Your statements are very good but not all boat hulls are designed the same . The more aggressive they are the more speed is scrubbed . Those that are more aggressive also produce more horse power . The jet ski line of any single manufacture is a good example .

TS has a good all around ski and the old one would of been even better if it was a true flexi ski . There is a world of a difference between a ski that flexes compared to a rigid ski . They had room for improvement but decided to take another route since it appears Yeti had a little influence in the new PTS ski .

The Yeti ski one upped the TS in aggressiveness and float . It compresses The snow under the ski better creating lift , it actually climbs up onto the snow instead of pushing it's way up .

I'm also curious about the Camso ski because it might be an exceptionally fast ski because the design is not as aggressive as these other two . The price is the only thing that keeps me from pulling that trigger .

The other skis kind of take a back seat to these guys .

The Camso ski is also similar to the first generation ski that Boivan had on the fanners . It was just as wide but hull shaped with a lot of wear rods but it also had a slight curve to simulate the curvature of a tire and the back side behind the spindle was noticeable short that made a big difference in taking aggressive feed back out of the bar from bridging or driving over bumps that all these skis have that causes those awkward wipe outs .

I also run the old Gen II ski on those days where I just want to hall butt and in the right conditions neither the TS or Yeti ski can run that pace because they are scrubbing speed and actually slow the nimbleness of the machine .

With all that babbling the question is why do these one ski manufactures have such a long ski made for such a light machine ?

 

[Kaarlonen]

You are correct and there are endless number of variations in shapes and sizes.
I tried to kick up some conversation and at least you took the bait .

Could it be that the ski has extra legth and floatation for situations where almost all weight is on the ski like in nose down landings.

I sketched up this picture to better visualise my earlier post. Also added that compression of snow to get lift. That was a good detail to point out.

 

[Hawkster]

I tried to kick up some conversation and at least you took the bait .

Could it be that the ski has extra legth and floatation for situations where almost all weight is on the ski like in nose down landings.

I think a better word would be SUCKER!

I was expecting the length reply also

The latest Yeti video did a really good job of exploiting the fun factor and addressing how they keep the front end from taking the load of the machine . Granted it's going to happen .

That is a neat ski , is the intake and out on the compressed the same size ? Besides floating you could have a ski that actually throws a roost to the track .

Not to mention it looks like a fast one .

 

[Kaarlonen]

I am probably going to build a ski this summer with that profile, but make it adjustable in width, keel height, float area dimensions etc so I can test different variations quickly in the field.
I cannot say what shape works best, at this point I have only estimations based on theory and real life experience.

That snow compressor under the wing probably just needs to be straight tunnel that gets smaller at the end of the ski. I see no point doing accurate arc shape since snow doesn't care about fluid dynamics. At least not in the prototype phase. Simple tunnel with slightly bigger intake than exhaust so the snow compresses and any excess snow is forced downwards and ski is forced upwards.

I'm hoping to someone challenge my treory/ideas so they can be improved.
I'm sure there are many things that I have not thought of.

 

[Sheetmetalfab]

I am probably going to build a ski this summer with that profile, but make it adjustable in width, keel height, float area dimensions etc so I can test different variations quickly in the field.
I cannot say what shape works best, at this point I have only estimations based on theory and real life experience.

That snow compressor under the wing probably just needs to be straight tunnel that gets smaller at the end of the ski. I see no point doing accurate arc shape since snow doesn't care about fluid dynamics. At least not in the prototype phase. Simple tunnel with slightly bigger intake than exhaust so the snow compresses and any excess snow is forced downwards and ski is forced upwards.

I'm hoping to someone challenge my treory/ideas so they can be improved.
I'm sure there are many things that I have not thought of.

I put more time on this ski yesterday.
Does well at slower speed choppy snow and crust.

Its not a deep snow ski that's for sure.
The ts ski floated better in the 2-3' of corn snow I found.

I think it needs the dual center carbide for higher speed trail.