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Plans for skis

92 posts in this topic

Posted

I see some pretty skinny ski's here.  If your flying off of pretty well packed snow or snow less than 6" deep they work fine.  I can tell you though, Ski flying becomes no fun when you find some good snow and slow down in it and find yourself sunk up to the belly of the plane.  Wider is better!  yes, the skinny ski's are easier on the axles when you are turning the plane by hand, but I would rather be a little tougher on the axles than spend the night tramping down a runway and digging out an airplane.

There is a pretty good reason why the skinny ski's of yesteryear are not made by the big producers anymore.

 

:BC:

 

Leni,  What is your definition of "skinny" and "Wider is better" in inches and also length, for AvidFoxes?   EDMO

mine are around 68" long can't remember exactly and 13" wide.  I have never wished for smaller ski's.  A few times I wished for more surface area.

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Posted

Do any of you guys know right off about how far does the tire stick through the ski?

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Posted

Do any of you guys know right off about how far does the tire stick through the ski?

as little as possible if you plan to operate in deep snow.  Put a little wheel at the back of the ski to keep the tails from dragging.  Even them, you would be surprised how well the ski will glide over pavement even if it does hit.  The wheels should just stick down far enough to get you over the lip of the hangar door if your lucky enough to have a hangar.

:BC:

 

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Posted

I set mine up to be about 3/4" if I air up the tires to ~20 psi.

At normal (~12 psi) they are too close and often rub the runway.

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Posted

perfect thanks better get started here, Looks like I'm on schedule to be test flying by spring, so now I get to play with building the accessory's 

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Posted

Give me thoughts on these

100_1153.JPG

100_1154.JPG

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Posted

As a reference, mine are 16" at the widest and 8" where they go to the inside of the tire.  60" OAL, with the axle in the middle. 

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Posted

Question from a guy who knows little about skis:  I have seen wheel skis where the wheel goes in the center of the skis, but closed in on both sides - So why don't you make the part behind the wheel as wide as the part in front of the wheel on these?  EdMO

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Posted

Question from a guy who knows little about skis:  I have seen wheel skis where the wheel goes in the center of the skis, but closed in on both sides - So why don't you make the part behind the wheel as wide as the part in front of the wheel on these?  EdMO

I have wondered that as well, all that I have seen are open behind the tire, Maybe so you don't end up with 50lbs of snow sitting there,

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Posted (edited)

Question from a guy who knows little about skis:  I have seen wheel skis where the wheel goes in the center of the skis, but closed in on both sides - So why don't you make the part behind the wheel as wide as the part in front of the wheel on these?  EdMO

I have wondered that as well, all that I have seen are open behind the tire, Maybe so you don't end up with 50lbs of snow sitting there,

I thought about that too - there should be a way to turn up that corner behind the tire just like the front end of the ski?   Maybe just put a vertical piece there to keep snow from piling on?   EDMO

Edited by EDMO

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Posted

one thing to think about.. Airglass would be a good site to check out and lets say they use the LA200 or LA2500 straight ski.. the wheel ski used and certified for the same aircraft (in this case PA-18) is a 3000.  Also, there is a reason to run the axle aft of the center of the ski.  Putting more weight on the tail of the ski forces the noses up and will help you climb out of deep snow or pop over that hidden rut.  Longer is better as is wider.  The more surface area you can get within reason the better for those fluffy snow days.

:BC:

 

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Posted

http://trickair.com/design-and-installation/

 

Here is another one to look at.  I like the airfoil on them to minimize drag!  Well designed and thought out ski..

Maybe one day I will look into vacuum bagging and make some molds for a ski like this for our birds.  There has to be a way to make an affordable ski for us that will still take a beating.

:BC:

 

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Posted

I had the "hole in the middle" skis to begin with.  They scooped lots of snow with the tails and didn't want that on the new skis. 

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Posted (edited)

http://trickair.com/design-and-installation/

 

Here is another one to look at.  I like the airfoil on them to minimize drag!  Well designed and thought out ski..

Maybe one day I will look into vacuum bagging and make some molds for a ski like this for our birds.  There has to be a way to make an affordable ski for us that will still take a beating.

:BC:

 

TJay, Look at these - that is what I was talking about for the rear of the skis.  I think any snow would blow off of them too. 

Note the side view showing the up-angle of the underside of the rear part.   I still think a fence on top of there would work, since the tire has broken the airflow anyway?     After all - its "Experimental", and you can change it if needed.  Maybe something like a pointed rear half of a wheel pant on top would even streamline the tire drag?   Just thinking and wondering.    EdMO

Edited by EDMO

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Posted

I had the "hole in the middle" skis to begin with.  They scooped lots of snow with the tails and didn't want that on the new skis. 

I think some thin aluminum or UHMW over the top of the tubes would shed the snow really well and not add crap for weight.  The tubes tend to hold the snow in and let it build up, especially in slushy stuff.  The down side is the first time you step on the ski you gonna bust your ass if you have UHMW on the tops as well.  Some strategically placed grip pads would be needed for sure!

Some folks are not flying in areas where any of this additional "covering" is even an issue or required but some of us would benefit greatly by a covering like the trickaire skis have on top.

:BC:

 

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Posted

I see a lot of skis for the mains but very few for the tail wheel, Why is that,

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Posted

Lot of people get by without them.  Some advantages of having them are that you don't sink into the deeper snow as bad with a tail ski, and if you pack your runway with some kind of a drag, running without the tail ski leaves ruts in the field.   Not wheel penetration type, but here is what I used on the Avids.  JImChuk

 

new skis 005.jpg

new skis 006.jpg

new skis 007.jpg

new skis 008.jpg

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Posted

I see a lot of skis for the mains but very few for the tail wheel, Why is that,

If your not in deep snow a tail ski is not to big of a deal.. If you have deep snow or as Jim said and nice groomed runway then a tail ski is a MUST!  If you don't have enough elevator authority to get the tail out of the snow with power and full down elevator then you extend you take off run A LOT because of the anchor you are dragging behind you.  Not to mention the fabric on the bottom of your bird getting ripped up on crusty snow when the tailwheel breaks through and you sink up to the fuse in the tail.

This is the tail ski that Larry and Brett came up with.  I plan on making one a bit larger so I can run the 8" tailwheel with it and get a bit more flotation.  You can see in the first pic on the right side of the ski is a tab just forwards of the axle.  This was put there to hit and adjustable bolt ski stop to keep the nose of the ski from coming up too much.  This is a weak point and all it did was buckle the tubing the fist snowmobile track I hit in the snow.  I will be a doing a little redesign on it when I make it bigger.

:BC:

 

 

Zi6_0086.JPG

Zi6_0089.JPG

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Posted

It was later modified to have two stop bolts.

I'm playing with a design that will not have a any pivot.  I really don't see the need.  An axle attachment and a support arm attachment.  The trick will be getting the AOA of the ski correct.

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Posted

It was later modified to have two stop bolts.

I'm playing with a design that will not have a any pivot.  I really don't see the need.  An axle attachment and a support arm attachment.  The trick will be getting the AOA of the ski correct.

I think a heavier spring at the front and just a stop so the ski cant invert when you hit a rut.  I have had that happen twice and had to flip it over then use .040" safety wire to hold the front of the ski up to get it home.  I now carry extra springs and small shackles to make repairs in the field but a redesign to it is on my list of things to do as well some time soon.  We are actually starting to get enough snow around the house that I will be going to ski's sometime soon I think.

:BC:

 

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Posted

Agreed, Leni.  I flipped that ski design several times, too.

This is why I see no need for the pivot at all.

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Posted

with all this information here some day we will have a perfect airplane,

 

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Posted

Yeah, it'll look like a Pilatus Porter...

p12-1-17.jpg

 

 

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Posted

But paint it Yellow, so everyone calls it a Piper Cub!  :BC:  EDMO

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Posted

Agreed, Leni.  I flipped that ski design several times, too.

This is why I see no need for the pivot at all.

If you are running straight skis.. No need for pivot.  Look at the burl tail ski.  Its a dog dish with a bolt hole in it.  If your running wheels ski's and taking off pavement and then climbing up to the mountains to play in the snow then I do think a pivot will help.  If would be really easy to put a better stop system on it so it cant invert and holding the nose of the tail ski up is pretty simple.  I would much rather have the nose high and no way it can invert than trying to figure out how to get the ski to "fly" level but still sit level tail low as well.   Not sure if that really made sense but I think you know what I can getting at. 

In all, you designed a really good tail ski that is easy to fab and economical as well.  Just needs a few tweaks to now beef up known failure points and give the new ones hell.  I am guessing we will go through a few designs before we settle on one that is a good all around compromise.

 

I would give both nuts for the porter, but after I sold the house and boats to afford the purchase price I would have to get another job to feed the damn thing :lol:

 

:BC:

 

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