Damned Aktahoe1 got me addicted to crack, and now I'm looking into the crystal ball, seeing some skis in my future. As I may have mentioned, my next aircraft is going to be a kit build in the 100hp class.

I know Courierguy has the Datums, and his photos make me drool. Anyone used the Summits? They're built here in Oregon.

I'm a n00b to aircraft skis... am I correct in my understanding that the Datum is a fully retractable, while the Summit is a set penetration?

Datum:


Summit Aircraft Skis:

My 2 cents worth:though I would have loved to deal with an Oregoner as opposed to a Quebecer, and the associate hassle and cost of the border shipping thing, I was sold on the "balanced" layout of the Datums. The twin tails also of course increases the total footprint, and just looked to me (a snowboarder, just got done 10 minutes ago, 7" of new powder) more "snowworthy". Plus...I didn't even know about the Summits. I'm not sure how they would handle gravel and dirt, which I need to operate out of along with snow, the Datums seemed to be the most wheel worthy also.

Before I got Bushwheels, I suspected everyone who had them raved about them to justify their expense, since then I have turned into a raver also as it is all true. I am trying real hard to remain objective about the Datums but damn I think they are the hot setup, maybe the guy who makes them may move to Oregon?? When you are on the skis, you are ON THE SKIS, no wheel hanging down. But you pay for that in weight and complexity.

The main thing I noticed is the tip design is very different, the Summits have little upturn, the Datums a lot. I do like the carbon fiber construction Summit uses, I guess it comes down to that if I was looking for a Trick Air type wheel penetration ski, and had a paved runway only to deal with besides snow, they would be the way to go, fully retrac the Datums are my choice, (of course I have to justify their expense!)

Add this one for experimental aircraft too. Based in Minnesota.

http://greatwatersaerospace.com/index.p ... 5&Itemid=8

I have not flown either but I have flown a 100hp airplane on skis a fair bit (c-120) and fixed penitration skis suck in many diferent snow conditions. id definitly be looking at the retractibles, drag is huge when you dont have horsepower.

In my opinion fixed penitration skis are a good safety measure for snow conditions were you could probly land on weels but arent sure, but for real ski flying you need a flat bottom ski and the bigger the better!

I just got a reply from Summit for their fixed penetration ski for my plane. 2550 gw and Grove spring gear. The answer was they are still developing a ski for my weight class and it will be several months yet, expected price at $3999. I have not heard back from Great Waters Aerospace. They might have shut down early for the holiday. I priced the Trick Airs for mine three weeks ago. $7200. They are a certified ski and this model would handle a C180. The 100hp class would be somewhat cheaper. I like the fact that the fixed Summit and Trick Air let me use my current axle by mounting a second one on the inside of the spring gear just for the ski and appear really easy to make the initial install. Down side is they are fixed but powder snow here lasts only until the wind drifts and grinds it to the density of a Baja sand dune so I'm not sure if I need retracts.

I don't have any current price for the Datum's. I dealt on some last winter but ran into a snag when I could not get confirmation on the strength of a hollow axle to swap out the solids on my Tundra to carry its 2550 gw. Datum has to out source the axle for my plane. Unlike the Trick Air and Summit they do not come with the ski.

Checking the Datum Hompage, I notice a familar Rans 7 with Datum Skis. They still take my eye for the money and performance.

For $7200 I would think you could find a used set of retractables, like AWB 2500s or a set of Aero 2800 semi retractables.

Penetration skis create a LOT of drag. They are a GREAT way to get stuck. Then again, if you're just installing skis as a drag creation mod, it probably doesn't matter .

If the snow blows like it does in South Dakota like it does in ND, eastern MT and this part of the world, skis aren't worth the bother unless you can go somewhere landable, far, far away... . Snow gets really rough hereabouts, as you say, right after the first wind hits it. Last winter, I made precisely two ski landings. One of those was in a highway ditch, cause the road smoothed it out, and was just so I could say I'd landed on skis....

Good luck, but before I spent that much on skis, I'd take a look around for certified skis as well.

MTV

It can be a tough chioce between wheel skis and retracts. When I designed the Summit ski, I looked at all of the skis so I could to get ideas and perhaps the does and don'ts. I made a trip back up to Anchorage where I once lived and learned to fly. Around Merril Field and Lake Hood there are plenty of skis to look at, those guys are rough on skis.
I needed the skis to be extremely light weight so I built them out of carbon fiber using the monocoque construction method. The snow drag had to be a minimal so the tire only extends past the bottom of the ski by 2 inches and the upturn of the ski tip is an angle to prevent snow plowing, I don't want to push the snow. By changing the mounting bracket, the same ski will fit the 6.00, 8.00 and 8.50 tires. I can remove or install both skis in under 3 minutes. The thing I found the most interesting about my research in skis is that there seems to be no bearing between the skis advertised gross weight rating and its bottom surface area. Just because the ski is rated for an aircraft gross weight of 2500 pounds doesn't mean it will float it in deep snow. Shouldn't there be a standard ratio for aircraft weight to square inches of ski surface?
My Kitfox with a Continental 0-200 has a gross weight 1550 and my Summit ski has a surface area of more than 1000 square inches, so roughly 1.5 lbs. per sq.in. The ski will handle a greater load but it may not float it in deeper snow. My flight today included several landings and takeoffs in almost 2 feet of fairly fresh snow. I made all landings to a full stop and a 15 minute break for photos on one. Turns were easy and no getting stuck. I guess the ski you choose just needs to meet your specific mission requirements.

Mike

Mike, welcome to BCP. Thanks for your insight on the Summit design.

You have a beautiful Kitfox 7, hopefully I can take a peek inside one of these days soon.

Z

Thanks Zane,
Our business is at the bend airport, your welcome anytime.
Mike

Mike,

I agree with you that there should be some standard nomenclature for skis, and the same should go for floats, which suffer from the same nomenclature mysteries. Ask a float manufacturer what the ACTUAL bouyancy is for their 2347 float and you're apt to hear 2800. Oh, well.

You may have solved the problem of tire drag on penetration skis. If so, good on you. I can tell you that on my retractable wheel skis, with 8.50 tires installed, the tire only protrudes below the ski surface less than an inch, and it creates a TREMENDOUS amount of drag.

There's no doubt that penetration skis are simple to install and remove and can be tough. Weight is always an issue. What is the weight of your skis, with rigging? That is a HUGE problem with most skis. I've run Rosti Fernandez retractable skis, made in Germany, with a total installed weight of 76 pounds and they were wonderful skis. They also have a LOT of surface area, as you describe.

I hope your skis are real winners. IT sounds like you've considered most of the real difficulties of ski design.

MTV

Zane wrote:Mike, welcome to BCP. Thanks for your insight on the Summit design. You have a beautiful Kitfox 7, hopefully I can take a peek inside one of these days soon. Z

Ditto on the welcome, Mike. I assume that's your Kitfox in the photo of the Summit skis in the first post? How about a photo of the whole airplane? I've always liked them Kitfoxes....someday.....

hotrod150 wrote:

Zane wrote:Mike, welcome to BCP. Thanks for your insight on the Summit design. You have a beautiful Kitfox 7, hopefully I can take a peek inside one of these days soon. Z

Ditto on the welcome, Mike. I assume that's your Kitfox in the photo of the Summit skis in the first post? How about a photo of the whole airplane? I've always liked them Kitfoxes....someday.....

He has a few pictures in his gallery. Welcome Mike, nice kitfox!

Thanks for the welcome everyone. I love this type of flying and having an experimental category aircraft lets me be creative with a variety of add-ons like the skis, tires sizes, props, engines, VGs, etc. without having to get anyones (FAA) permission.
My skis weigh in at 17 pounds each with the rigging. The 1/8" UHMW adds another 3 pounds. I was working on getting some new videos yesterday but my camera crapped out on me. I haven't figured out how to attach a photo to these posts yet, can anyone help me with that?

Thanks,
Mike

PM'd ya Mike

Mike,

Be careful with the 1/8 inch thick UHMW. We found that it tends to "bag", and then crack, then create a huge snow scoop . Even though the 1/4 inch stuff is heavier (about twice as heavy, actually ) the extra weight was well worth it. It took a season or two for the thin stuff to bag out, but it was a VERY bad thing to discover upon landing somewhere deep.

Great weights for those skis.

MTV

Mike,
I will pump up the Summit skis in my travels, it's not like I'm married to the Datums, I just own a pair. I never did learn to pronounce the Datum head guys name, what with him being French Canadian, I can do "Mike"! Point being as I mentioned earlier a lot of advantages dealing local or at least in this country. You're design looks like a great bet for those in the market for penetration skis, sure can't beat the weight and simplicty of them.

if you got stuck you can pull the tires and get out of there on just skis Id like that alott better than the snow shoe option.

Been snowed in over the weekend. There is a place worse than here we call North Dakota. Friend called from up there, said it had been snowin for four days. Most of the storm his wife just stands there and stares thru the window. If it don't stop pretty soon he's gonna hafta let her in.

Sure would like some skis for the plane.

dirtstrip wrote:Been snowed in over the weekend. There is a place worse than here we call North Dakota. Friend called from up there, said it had been snowin for four days. Most of the storm his wife just stands there and stares thru the window. If it don't stop pretty soon he's gonna hafta let her in.

Sure would like some skis for the plane.

I'm sure that joke, or variations thereof, has been around for decades, BUT, it is the first time I heard it and I laughed loud enough to wake the dog!

4.4 hrs on skis today........

I have had the Datumair 1500's on my Rans for the second winter now. They work very well and are very maneuverable on snow. There is a lot of surface area on the snow and the main reason I bought them for the Rans rather than penetration skis is the fact that when you are in Ski Mode, the wheels are resting on the ski deck and the aircraft weight is supported directly by the wheel axle just as if you were on wheels..

Here are some videos:

http://www.youtube.com/watch?v=fuZKoRuIZGc

http://www.youtube.com/watch?v=sWDrJF0A3TA