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New Wheel Ski Design: What works best?

B.D.

B.D.

Registered User
Hello everyone; first forum post here. I'm playing around with some designs for skis; if I can figure out something that works well, I will probably end up taking it to market.

i) The first thing I have in mind is that they must be inexpensive. One big turnoff to getting onto skis is the cost of a new set, which can be upwards of $8000 for something the size of a Maule or 180. I know there are cheap Schneiders lurking around, but those are heavy and no longer in production, making it a scavenger hunt to get paperwork or parts from other owners.

ii) My next great debate is hydraulic vs penetration. Hydraulics are less draggy but heavier, take longer to install, and IIRC requires an AME to sign off during changeovers since hydraulic lines are being played with. Penetrations are draggier, lighter and easier to install. Hopefully, I can get some feedback in this area. I had thought about using quick-disconnect fittings and using the argument of them not losing fluid when disconnecting in the STC, voiding the need for an AME, but I have yet to see them work, so I wouldn't know. Or maybe I should avoid hydraulics altogether and do something with cables that use the same plumbing as water rudders in the seaplane configuration?

iii) Another thing I have in mind is being able to use *almost* any size tires, saving the cost and hassle of having to buy one specific set of Goodyears as other manufacturers require.

iv) Include ready-made rigging in the package.. saves everyone time and a headache.

v) They need to be easy to work on (ie replace UHMW bottoms, keels, change hardware to fit one airplane to another). Also need to be sturdy, all of my designs so far have a stub axle and inside mount bracket. Far less risk of them breaking off.

Summary: Trying to find the best compromise of lightweight, best performance, strength, low cost, easy to mount and dismount.

Any and all feedback is appreciated.
Thanks in advance

BD
 
Datums are fairly cheap, lite and work fantastic
Got 5 sets flying by us right now

About our skis | Datum Inc.

Datum's products: Series 1000 ski packages, Series 1500 ski packages, Series 2000 Lite ski packages, Series 2000 ski packages, Series 2500 ski packages, Series 3000 ski packages
www.datumair.com www.datumair.com

Skis | Datum Inc.

Datum's products: Series 1000 ski packages, Series 1500 ski packages, Series 2000 Lite ski packages, Series 2000 ski packages, Series 2500 ski packages, Series 3000 ski packages
www.datumair.com www.datumair.com

View attachment 1054419660.webp9663.webp

Glenn
 
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cubdriver2 said:
Datums are fairly cheap, lite and work fantastic
Got 5 sets flying by us right now
Click to expand...
Hi Glenn, Thanks for the reply. While Datums look like they would work well, they aren't a certified solution. I'm also not a fan of how they're electric. I would hate to be stuck with the skis in the wrong position without electrical power.
 
B.D. said:
Hi Glenn, Thanks for the reply. While Datums look like they would work well, they aren't a certified solution. I'm also not a fan of how they're electric. I would hate to be stuck with the skis in the wrong position without electrical power.
Click to expand...
Linier actuators work great. Only 3 amps to run and about 80% lighter then a hydraulic system.
They are switched independently, so if one fails just put the other ski in the same position as the failed one. They land just fine in the wrong intended position.


Glenn
 
I've recently been thinking through the different options on the market as well. Something I've learned being on the consumer side of this process is that the ski market for GA use is a very very very small market.

When I was speaking to Airglas about their ski, someone told me that without their large Department of Defense contracts there's no way they could offer skis to the GA market at as low a cost as they currently do. Last fall Atlee Dodge took over the STC for Federal/Fluidyne and what I've heard is that they will begin their own manufacturing of the Fluidyne ski. As Cubdriver2 noted Datums are already in production and have their advantages. Each of these skis may have their drawback of function, weight, cost or other some other factor, but these are well established companies providing a ski option to an existing tiny market. You may even ask Datum if they ever plan to become certified and if not why. I'm betting they will tell you it's not cost effective.

Now, if everyone just settled for any existing flawed product currently on the market we'd never see any progression so I'm not saying don't pursue your dreams. All I'd recommend is doing some market research to see if your time, energy, blood, sweat, tears, and finances etc will all be appropriately invested in a project that has a viable market. There are many on this site with more experience and knowledge than me and hopefully you will get their insight as well. I'm running straight Airglas skis on my PA-12 and Fluidyne 3600 hydraulic wheel skis on my 185.
 
Thanks for the advice, Cbass. How are you liking the Fluidynes? Is there anything you would change if you could? Approx how much weight does the whole assembly add?
 
BD, didn't mean to shoot holes in your boat. A reasonable priced pair of combo skis would make everyone's life easier. A lot of us have wondered off the main trail because of the cost of whats available
Best of luck on your journey

Glenn
 
cubdriver2 said:
BD, didn't mean to shoot holes in your boat. A reasonable priced pair of combo skis would make everyone's life easier. A lot of us have wondered off the main trail because of the cost of whats available
Best of luck on your journey

Glenn
Click to expand...
Boat still floating 🚣‍♂️. I appreciate all the information I can get, thanks Glenn.

Ben
 
Just as a data point, good luck finding ANY new certified (or probably experimental) retractable skis for anywhere near $8000. Last new set of Fluidynes I heard of was many years ago, at $18000.

The Idea of making skis rigged for a particular plane and ready to bolt on sounds good, but there are a lot of variables. In any case, rigging skis isn’t that big a deal. Trying to provide setups to fit will raise prices substantially, and I’ll bet create a lot of angst…..when someone says “Cessna 180”, there are a lot of variables there.

one of the biggest challenges in designing retractable skis is weight control. The Rosti Fernandez 8001 skis are incredibly light, at around 80pounds or less, including hydraulics. AWB 2500 and Fluidyne 2200 are both well over 100 pounds, not counting hydraulics.

The Rosti skis are composite, and use a very simple and light hydraulic system.

Penetration skis may work in certain snow conditions, but I doubt that a penetration ski would work well in more challenging snow conditions.

I wish you luck. The Rostis prove that retractables can be light, but cheap? Good luck there.

MTV
 
I commend your efforts to create the better mouse trap and your objectives are admirable, however, the aircraft ski market is a narrow niche market. Barring a breakthrough in a miracle lightweight structurally compatible material, the current state of available materials and manufacturing results in the current market status. My recommendation is to research the need in the field by interviewing major players just as DeHavilland and Grumman did when attempting to make a better mission specific aircraft (the DHC-2 and G-164 Ag-Cat), at which both teams were successful.

My current arsenal of skis are Airglas L2500 and L3000 for straights and Federal AWB 2100 and 4820 on the hydraulic side, use depends on mission. I previously flew HH-60 Pave Hawks equipped with Airglas skis so I can attest to their extreme durability and mission utility. I am a huge fan of Airglas products for reasons too numerous to include in this post.
IMO stay away from fixed penetration for performance reasons unless you find a novel method to decrease drag. Focus your inner Burt Rutan by balancing strength and weight, as Rutan once facetiously told his engineers, "Throw it up in the air, if it comes down its too heavy".
TR
 
B.D. said:
Thanks for the advice, Cbass. How are you liking the Fluidynes? Is there anything you would change if you could? Approx how much weight does the whole assembly add?
Click to expand...
I'd have to check weight and balance to see what the ski assemblies add. Looks like MTV was estimating 100 plus pounds. As for changes, admittedly the airplane and skis are new to me so I'm in my infancy of learning them. So far they fit my mission and needs, however I've been encouraged to upgrade to the airglas ski by my peers. My understanding is that the fluidynes struggle in the turns because they aren't a "full" ski in the tail like the airglas ski.
 
The AWB 2500 skis I ran on my 170B added 126 pounds, not including the hydraulic reservoir, axle extensions and hydraulic plumbing, which all stayed with the plane when the skis came off. I don't recall precisely what the Fluidyne C-3600s on our 185s weighed, but it was around the same.

If you could get a strong set of retractable skis at or below 100 pounds, you'd have a winner. And, at that, you might sell a total of 100 sets of one size, eventually.

MTV
 
I've flown both the Fluidyne 3600s and the FliLite 4,000s on 185s a lot. My memory is both weigh about 120-125 lbs. plus the pump and reservoir.

Both skis handle well in all operations but the 4,000's have a little better floatation in deep snow. For tight turns, just pump the inside ski up and you can almost pivot on the tire.
 
Thanks for all the replies and information.

I think I could realistically get the entire system to weigh 80-90 pounds. But who knows, I may work a miracle and be even lighter.
The only real cost factor in this for me is the upfront STC costs, but doable if there's enough interest.

I've got a couple of ideas that are solidifying a bit more. Idea one is similar to FliLites/GLH skis, where a plate is moved under the wheel. I should be able to achieve this using a spring system that naturally pulls the plate forward and a lever in the cockpit to pull the plates backward, putting the whole thing into a straight ski-like configuration.

Idea two: the ski is shaped very similar to RF skis; rather than using a hydraulic to move the ski up and down, the front ski bungee naturally lifts the ski, and a pulley/cable system controlled by a cockpit lever would pull the ski down and back. While I know that the upward and back forces from the snow would keep it locked in the ski-down position, I still worry that somehow, during a turn or uneven ground, the cable gets pulled on and rips out the lever from the cockpit, doing serious damage.

That said, idea 1 looks like a much better option, but maybe I'm overthinking something?

Ben
 
Maybe Tooltime Tim will post pictures of his Flilite copycat skis. He used linier actuators to move the plate. Seems to work great

Glenn
 
B.D. said:
Thanks for all the replies and information.

I think I could realistically get the entire system to weigh 80-90 pounds. But who knows, I may work a miracle and be even lighter.
The only real cost factor in this for me is the upfront STC costs, but doable if there's enough interest.

I've got a couple of ideas that are solidifying a bit more. Idea one is similar to FliLites/GLH skis, where a plate is moved under the wheel. I should be able to achieve this using a spring system that naturally pulls the plate forward and a lever in the cockpit to pull the plates backward, putting the whole thing into a straight ski-like configuration.

Idea two: the ski is shaped very similar to RF skis; rather than using a hydraulic to move the ski up and down, the front ski bungee naturally lifts the ski, and a pulley/cable system controlled by a cockpit lever would pull the ski down and back. While I know that the upward and back forces from the snow would keep it locked in the ski-down position, I still worry that somehow, during a turn or uneven ground, the cable gets pulled on and rips out the lever from the cockpit, doing serious damage.

That said, idea 1 looks like a much better option, but maybe I'm overthinking something?

Ben
Click to expand...
Upfront STC cost you can figure six figures to get there and likely 5 years. Doing an STC isn't cheap!
 
Surface ice on skis can become an enemy. Anything that can move or slide on a ski should have positive pull or pressure available to overcome freezing of parts. Flying into cold air well below freezing with skis wetted by surface melt or overflow glues components. Same for landing with real cold metal and encountering wet conditions. Simple is better, which is why wheel penetration skis are available despite their added drag.

Gary
 
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To many options. Right now I havé trick air on thé Cub. Théy are thé Best Flying ski . Easy and fast install and removal. Performance wise no loss In Climb or Cruise unlike most ôther hydraulic or penetration skis. Relatively light fo thé Cub skis but a fair bit heavier for thé larger skis. Snow performance is decent . Thé best hydraulic is Air glass order now for next winter. Aéro ski is thé only one that bolts right on and riging usualy fits right out of thé box.
 
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Dealing with hydraulics all the time in my crane biz, and knowing the power of a linear actuator with my Datum wheel skis, this looks like a great setup, simple and no doubt lighter than a juice actuated ski.
 
Never user Datums not certified. But théy move forward in flight usualy a négative effect on aérodynamiques. Fly low level tracking Survey for 8 hours a day and See how you like thèm . I developed a dislike for the Fluedyne L shaped ski on m’y Maule for that réason,that and the weight. Switched to tricks much better and no change on Where I can land and take of. Just a bit more graby on crusty snow.
Thé trick Airs fly as if théy are not there and still give me the ability to land and refuel etc anywhere in the bush.
 
I agree that Fluidynes aren‘t the best, especially in challenging snow conditions. They’re the skis I’ve been most massively stuck with on a 185.
one of the problems with penetration skis is they always limit the size of tire, therefore the clearance on other than snow. That’s one of the beauties of the Rossi Fernandez skis, which permit useof 8.50 tires, and provide lots of clearance of the tails, without thos miserable little tail wheels, some of which really drag in snow. some are worse than others, but they all create drag.

MTV
 
Dog said:
Never user Datums not certified. But théy move forward in flight usualy a négative effect on aérodynamiques. Fly low level tracking Survey for 8 hours a day and See how you like thèm . I developed a dislike for the Fluedyne L shaped ski on m’y Maule for that réason,that and the weight. Switched to tricks much better and no change on Where I can land and take of. Just a bit more graby on crusty snow.
Thé trick Airs fly as if théy are not there and still give me the ability to land and refuel etc anywhere in the bush.
Click to expand...
Datums don't hardly notice them in either position. So much that I sometimes forget to pull them back after a wheel takeoff

Trickairs are only certified choice for most but Summits work a lot better but Datums work the best. Side by side comparison with all 3. IMHO

Glenn
 
The summits look interesting - a bit lighter than trick air but not certified both run 850 tires and a single rear wheel.
After the original rear wheels got flat spotted (frozen with overflow) I did install 4 inch snowmobile bogie wheels , they are quieter and less drag in the snow and way lighter. They also do not freeze up as easy -- (no exposed metal). Not certified is simply a no go for many of us that use them to make a living. This has been very limiting on may aircraft. In Canada we can still find and use the Kehler skis, they are relatively light for Hydraulics and work well on 180/185 and cessna 206 .
 
Dog said:
Never user Datums not certified. But théy move forward in flight usualy a négative effect on aérodynamiques. Fly low level tracking Survey for 8 hours a day and See how you like thèm . I developed a dislike for the Fluedyne L shaped ski on m’y Maule for that réason,that and the weight. Switched to tricks much better and no change on Where I can land and take of. Just a bit more graby on crusty snow.
Thé trick Airs fly as if théy are not there and still give me the ability to land and refuel etc anywhere in the bush.
Click to expand...

Dog said:
Datums move BACKWARDS in flight, not forward, assuming one has them in the SKI position when flying anyway which is the proper way to fly with them. But yeah, not certified, and not likely to be.
Click to expand...
 
All Datum users know to fly with the skis "back", for less drag, whether or not we take off from pavement and plan to land on pavement. l like to immediately go to skis when taking off pavement, as soon as the wheels get air, it just looks cool, feels cool anyway, plus I may forget otherwise! In an engine out at low altitude, odds are the skis will work as well and maybe better than the tires.
 
Depending on ski and aircraft, moving the ski back from a forward position can move the CG aft some and reduce tail down load, which can lower wing loading and improve cruise. Whatever position offers the lowest drag. I suppose light skis don't change CG much. I just liked the ides of skis down/wheels up over remote terrain.
 
Bit of a side question here: does anyone know if the FAA requires tail skis to be STC'd or certified?

Our regulation on this matter in Canada is as follows: "Tail skis and pedestals do not need to be approved as components and will not be rated for strength by Transport Canada. It is recommended, however, that they be designed to meet the same strength standards as main skis on the basis of the maximum static load on the tail ski as installed in the aeroplane."
 
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