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Thread: Datum ski speeds

  1. #1
    TurboBeaver's Avatar
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    Datum ski speeds

    Just wondering if anyone can provide real numbers for cruise speeds with Datum wheel skis??? Either with a Borer prop or Catto or standard prop. ?????

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    Bearhawk Builder's Avatar
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    Did you end up getting a set? Sorry can't help with the speeds, Kestrel can give you an idea of the speed loss on his Bearhawk. Not much if I remember right

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    kestrel's Avatar
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    I lose about 3-4 kts on my Bearhawk. 8.50's without skis, 6.00's with the skis.
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    cubdriver2's Avatar
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    Quote Originally Posted by TurboBeaver View Post
    Just wondering if anyone can provide real numbers for cruise speeds with Datum wheel skis??? Either with a Borer prop or Catto or standard prop. ?????
    Is this one of them Oxymoron examples I see in the dickionary

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  5. #5
    TurboBeaver's Avatar
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    Yes we did order a set and just wondering what others see
    In Cubs /12s for airspeeds running them?

  6. #6
    TurboBeaver's Avatar
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    Sorta surprised how few folks on here have Datum skis..... On experimental Cubs. The builder says he has almost 500 sets out there? Alot of the sales are in Canada, but mostly
    he is selling them to potential Rossi 8000 customers, that are firmilar, with the great Fernandez skis in the 1980s that are
    now $20k. So even though he is huge in Europe its interesting with the Experimental aircraft interest so high
    in the US. There appears to only be a handful on here running these wheel skis??? Even though alot of folks can
    run straight skis off a lake or pasture, getting fuel at the airport is a tussel at best. Sacking on 5 gal jugs accross
    the melted ramp to a Cub parked in a snowdrift a 100 yds away; when its 10 below and the wind howling can certainly take ALOT of the zoom out of a great weekend!
    Messing around with ski dollys is almost a ditto operation,
    While no big deal on a nice day, can become a true pita when its cold and windy........
    I got used to Fernandez skis on a 185 and found them like
    MTV to be the ultimate in a wheel ski, however in todays
    current pricing they may not fit most budgets? Probably still the best option because you can run 8:50s with them.
    We will have a set of Datums mounted up on a Cub here very shortly. So will let everyone know how they go and the good and bad about them as soon as we get used to them.
    E
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    Quote Originally Posted by TurboBeaver View Post
    Sorta surprised how few folks on here have Datum skis..... On experimental Cubs. The builder says he has almost 500 sets out there? Alot of the sales are in Canada, but mostly
    he is selling them to potential Rossi 8000 customers, that are firmilar, with the great Fernandez skis in the 1980s that are
    now $20k. So even though he is huge in Europe its interesting with the Experimental aircraft interest so high
    in the US. There appears to only be a handful on here running these wheel skis??? Even though alot of folks can
    run straight skis off a lake or pasture, getting fuel at the airport is a tussel at best. Sacking on 5 gal jugs accross
    the melted ramp to a Cub parked in a snowdrift a 100 yds away; when its 10 below and the wind howling can certainly take ALOT of the zoom out of a great weekend!
    Messing around with ski dollys is almost a ditto operation,
    While no big deal on a nice day, can become a true pita when its cold and windy........
    I got used to Fernandez skis on a 185 and found them like
    MTV to be the ultimate in a wheel ski, however in todays
    current pricing they may not fit most budgets? Probably still the best option because you can run 8:50s with them.
    We will have a set of Datums mounted up on a Cub here very shortly. So will let everyone know how they go and the good and bad about them as soon as we get used to them.
    E
    Maybe there is a language barrier. Maybe not. The Quebecers have a reputation for building good stuff. (BRP for example).
    I have a really nice set of 1500 floats that were built in outback Que. He spoke french, me English but we still made a deal no prob. Fixed penetration Wheels Skis suit me fine, straight Skis would be almost useless where we fly. Can certainly see the attraction to the Datum Skis though, a true straight ski and a true “wheel only”. Lots of variables, simple verses not so simple, wt., transiting from snow across a paved surface (not sure how that works in going from ski to wheel)? Courierguy has a set and I think he likes them. Probably a good choice Turbobeaver, look forward to your report!
    Roddy

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    When I take my 29" Airstreaks off every winter, and put the Datums on after re-installing the (in my case anyway) 6:00's tires, the cruise speed stays the same. Near enough anyway, if anything a bit faster, not slower for sure, that I call it a wash.
    Where I do notice a big difference is if I have a chance to make a flight with just the 6:00's on, but no Datums. But then I also notice how rough my runway is, and that I can't land any of my local off airport sites, worthless in other words!

    Once I learned to make life a bit easier for the actuators, by not having them have to also fight a steep berm during the transition (dragging the plane uphill in effect) they have been trouble free, other then user caused problems. Stupid things, like landing on rocks (hidden by snow) or catching an exposed fastener on my steel ramp (since replaced with a earth ramp), and the biggie: failing to transition to the skis and landing in deep snow, wheels down, in a remote canyon in Wyoming just as an for instance. Or the oppposite, landing on a hard surface with the skis down. I'm here to tell you one can get away with both. In the Wyoming incident, the relief felt when I finally realized that NO, the snow wasn't that damn sticky, I HAD THE WHEELS DOWN..... and I wouldn't be spending the night there, made this learning experience worthwhile. They are about as idiot proof as a plane wheel skis can be, and I've proved it. Skis down, they land fine on frozen grass also.
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    40m's Avatar
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    I looked closely at Datums but chose Summits in part do to the lack of support in determining the best location for the front cable/spring attachment point. I was not willing to cut into the cowl to attach to the engine mount and then find out the geometry was not right. There was no language barrier just an attitude of just do what you have to do to make it work. By now I'm sure this has been resolved with all that are in service however Summits are simple to install with no worries other than maintaining proper tire pressure for ground operations.

    From Genesis: "And God promised men that good and obedient wives would be
    found in all corners of the earth."

    Then he made the earth round... and He laughed and laughed and laughed!

  10. #10

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    Apples and oranges comparing the two. I've landed on gravel bars and other rough surfaces, wheels down, thanks to the ski clearance I have. I wish I COULD use Summits but even my home strip operation, ground ops wise, needs that clearance. Plus I prefer being 100% on skis, with no tire drag. But still find the Summits simplicity real appealing, wish I could use them.

  11. #11
    TurboBeaver's Avatar
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    Thanks for the great info! Sounds like we will see a slight Increase when going from 31" tires to the Datums. I also really like the looks of the Summit Skis; and though not sure what folks are really paying for the larger ones? But the $6995 list price looks like over 50 percent more than Datums ??Which seames like alot considering all the extra hardware involved with wheel skis????
    Roddy stay tuned for the flight testing on wheels as soon
    As we get them rigged! And we will be able to post, the actual speed reduction from 6:00x6 tires to Datums. Thanks to everyone for sharing info. For what its worth a number that was floated out of the factory
    recently was that Datum has sold nearly 500 sets of these all over the world, since they first introduced them? Yet only a handful of folks know anything about them, on this website??? And the biggest shocker to me is they seam to be almost totally unknown in Alaska: of all places?????
    E
    Last edited by TurboBeaver; 11-06-2018 at 08:51 PM.

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    Bearhawk Builder's Avatar
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    Did they make any changes so that you don't have to switch to single puck brakes? That was the biggest no go for me, single puck calipers had to clocked as far up as possible to clear the tunnel, at least on the Bearhawk.

  13. #13

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    Quote Originally Posted by Bearhawk Builder View Post
    Did they make any changes so that you don't have to switch to single puck brakes? That was the biggest no go for me, single puck calipers had to clocked as far up as possible to clear the tunnel, at least on the Bearhawk.
    I don't know if those changes are even in the works, I do know on mine I am limited to single pucks. But, during the summer months it gives me something to scoff at when other fliers with dual puck brake systems still land longer then I do, backasswards bragging rights I guess. Since I am limited to single pucks, I have convinced myself it has taught me the best FLYING technique for landing short, rather then arriving a bit sloppily and just stomping on the brakes. Ski flying has really taught me a lot about brake power, as in none! I got a really bad charley horse on one early flight, during a turnaround I was pushing on the right brake so hard and the plane still kept going towards the trees, duh.....!

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    TurboBeaver's Avatar
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    I heard a couple of rumours about both double pucks were
    Possible and 7:00x6 tires with some finagling????
    I am sure we will find out just what you can and cant very
    Shortly! This is the one part of the ski that the Rossi's (and Summit's) certainly have
    an edge; with them having 8:50's and double pucks, as a standard set up! But the fact they cost as much as a nice old
    Tcraft or Chief has most definitely kept sales extreamely low as well. Around here about the only one that had them
    was the Warden Service or Forestry in Maine. You can probably trace every set of used ones here, back to belonging to the State originaly? As far as single pucks are
    Consirned with low preasure clyinders (rubber diaphragm) Scott, we ran them for years and they were fine, I have double pucks now with new pads and new diaphragms and they will barely hold an
    1700 runup........ So unless you have HP
    Boosters on your clyinders not sure single
    pucks are a huge factor, but sure would have been nice to have that option? The
    8:50 optional size would have been sweet
    To have more AOA which would certainly
    Enhance performance. 3" ext gear would help this somewhat and will probably make
    Borer lenght props possible? ( 3 point only?) The guy that brokered the deal is a very smooth negotiating individual; that speaks fluent French, he liked the guy that sells/ builds the Datums. Was very impressed with the facility, and workmanship he saw. BUT he couldnt do anything with this fellow, as far as he could
    Tell: you will do bussiness on HIS terms or
    He wont even sell them to you! NO discount for buying 3 sets:::and does NOT accept US cash !!! He expressed the fact
    Our money was worth more was effectively
    A discount in itself............so we didnt go down that road. So in summary good guy,
    Nice shop, great product, fair price. Cons: 6:00x6 tires, single pucks only?? May have to run shorter prop or 3 point only?
    Certified check in Canadian funds only.....
    His way or hyway........lol.
    Last edited by TurboBeaver; 11-07-2018 at 04:32 AM.
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    Bearhawk Builder's Avatar
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    Jean Marc was a class act when I dealt with him. Excellent customer service after the purchase and a quality product.
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  16. #16
    TurboBeaver's Avatar
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    Thats great news! So that is another one for the plus column!

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    RaisedByWolves's Avatar
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    One plus for the summits is there is at least one field approval, hopefully two soon.


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    WWhunter's Avatar
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    [QUOTE=TurboBeaver;731049

    His way or hyway........lol.[/QUOTE]

    That is a FACT!! At least that is my experience after buying a set of used Datums. I attempted to get different axles from him so they could be used on a different plane than this set was originally made and sold to fit. May have been the language barrier, but I ended up having a machinist friend make me a set instead. Sometimes it is easier to just move on.

    As was mentioned, overall a good guy with a great product.

  19. #19

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    I have double puck Clevelands on my PA-12, Borer prop and 3-inch extended gear. 2500 Datums. No problem.

  20. #20
    TurboBeaver's Avatar
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    Nunavut12,
    You have a picture of your skis to post here?

  21. #21

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    Here's one. It took some experimentation with the rear check cable to get maximum ground clearance.

    DSCN0385.jpg

  22. #22

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    I re rigged mine a couple times, maybe three, getting things fine tuned. we appear to be rigged similar. No big deal, cable is cheap, and Jean had suggested a lot flatter angle of attack while in the air then I had first set it up for. that and some other tweaking got me to where I've left it for the last several years. Ground clearance is real good going forward, dragging it backwards while on the wheels it's adequate. It's all a compromise of course, the main thing is how good it all works when on the skis! I also get a kick out of doing all the things I don't do when on the Airstreaks, when on the 6:00's: landing on pavement, long taxis, hard braking on pavement, those little tires are cheap and I don't baby them like the 'streaks.
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