|Jan 03, 2013, 10:31 PM|
DIY Snow Skis - Yet another thread
Well for those living up near the top end of the planet Winter is upon us. While many spend this time hibernating in the warmth of their workshops, I decided to slap some cheap skis on my plane & venture out into the snow...
And then, just when I was starting to have fun, total buzz-kill...
I won't mention the brand name but I expect you've come across these at your local hobby shop. Did I mention they were cheap? As with most things, you get what you pay for. So I tossed em in the bin, fired up the CAD software & set about designing my own skis...
Download Plans (PDF)
I've heard Formica (used in counter tops etc) makes a pretty good ski material. Tough as nails & best of all, nice & slippy on one side...
I used a heat-gun to help form the ski-tip...
The ski's spine I made from scrap pine. I used contact cement to temporarily tack my templates to the wood...
A little time at the scroll-saw, some sanding & we have a pair of ski-boots...
Clamping while the epoxy cures...
That looks like it might work...
Happy with Mommy & Daddy ski I produced a Baby ski too...
Masking off the slippy side of the Formica in preparation for some paint...
A dusting of primer...
A coat or two of black & they're looking the part...
While this looked good on the bench, as expected when I picked her up the skis flopped around all over the place. My el-cheapo skis used a spring to hold the skis in a slight tips-up attitude. While I could have copied that system I chose to take a slightly different route...
A length of wire bridged between the forward section of the two skis attaches to a spring. This holds the tips up while in the air & also helps keep them parallel to each other...
String attached to the rear acts as a stop & maintains the tips-up attitude. Once she touches down the string goes slack allowing the skis to follow the terrain...
I slipped the string under a screw & washer so that I can easily adjust the angle of the skis...
The baby ski is a little simpler, looks like it'll work fine with just a spring...
Well there she is, ready for some fun in the snow...
No doubt there's lots of other DIY ski designs out there & this obviously is not the only way to go but I figured I'd share what I came up with.
Download Plans (PDF)
Let it snow, let it snow, let it snow!
Oh yeah & before you ask, the plane is a Spacewalker by House of Balsa. Awesome park flyer & a lot of fun to build.
|Jan 04, 2013, 03:29 AM|
I hope it doesn't happen but you might just find that the Formica begins splitting at the rear edge of the spine. That's a pretty sharp ending to the spine and it's pretty close to where all the loads from the gear are centered. Time will tell. But other than this possible future issue the method and work looks great. But then this seems to be a common finding with your workmanship from all I've seen.
|Jan 04, 2013, 07:54 AM|
Great design, photos and write-up - thanks!
I like your method of holding the skis nose up but not TOO far nose up. I have a set of those black plastic skis and they've been OK the couple of times I've used them but the execution could be better. The nose gear spring failed on me the first time out.
Looks weird but it had no effect on the way the airplane flew and landed so I flew for the day like that. That airplane is a tail dragger now so perhaps I'll try your alignment method.
|Jan 04, 2013, 02:18 PM|
What a great photo! LOL yeah that might be a tad too much tips-up *grin* Yeah I wasn't too impressed with the el-cheapo ski's spring mechanism either. Looked like it had a few potential failure points (not that my design doesn't too).
I purposly didn't extend the ski's spine reaward as I wanted some flex back there. You're correct, that is a fairly abrupt ending to the spine. I probably could have tapered the strength somehow although I'm not overly worried about it. For a lightweight park flier I expect it'll be fine. That Formika is hard-core stuff but I'll keep an eye on it.
|Jan 04, 2013, 05:14 PM|
Nodd were are you located?
Great design, photos.
ok iam in on this thread and how to do the snow flying with skis, my first try with skis was not so good, i have the dubro ones and dident put the springs on, bad idea the plane wanted to nose down in flight, as i now know it was from the skis pointing down and pulling the plane down. i have to ask tho if i use the same dubro skis and put a 1/4 oz of weight on the back of the skis will this prevent the skis from making the plane nose down. iam thinking no inverted stuff tho.
|Jan 04, 2013, 07:11 PM|
I'm in Connecticut, US around 50 miles from New York City. We get a fair amount of snow here.
I'm not sure that weight or balance is the way to go with skis. You need something that actually holds the skis in position once its airborne. The DuBro skis use a spring that wraps around the axle that holds the ski against a stopper bolt. Not surprised that you skipped installing the spring though. Its pretty fiddly to setup & the hardware that came with mine was for a tiny 1/16" axle (probably meant for a much smaller airplane). I did find a larger set of DuBro skis but they felt way heavy & at almost $30 I decided to just build my own. More fun that way.
|Jan 04, 2013, 09:03 PM|
glad iam not the only one that thinks the spring is a fiddly thing to set up, but after reglueing the landing gear on my pulse 25 i did go thru the steps to hook up the springs and they will work, ill have to give them a try in the next few weeks. i dident know about the smaller skis till i had spent the 30.00 on the ones i have, making them is on my to do list to.
|Jan 06, 2013, 10:47 PM|
Thank you. Like most DIY stuff, hard to say exactly how long it took. An hour or so a day, here & there over a few days? *shrug*
Well I tested the skis today even though most of the snow at our field had melted. I did some taxi runs on small areas of the white stuff. I was really impressed with how fast she got up & moved, barely had to blip the throttle & she was zipping along. Unfortunately there wasn't enough snow to try turning around so I didn't get to see how the tail-ski steers. She did track nice & straight though. I also tried her on the grass but she just tipped forwards. The same thing happens on grass with 3" wheels on this model so that didn't surprise me.
Anyway happy with the ground handling I set her up on a largish patch of snow & let her rip. Talk about whip-lash, she accelerated to flying speed in just a couple of feet & was airborne almost immediately. Apparently snow Vs Formica is utterly frictionless *grin*.
I expected to have to mess with the elevator trim but other than a notch or two of left aileron she flew hands off just fine. I did notice she flew a tad heavier, was a little more twitchy during high G maneuvers. That was to be expected though, the skis are heavier than the wheels but not by much. Overall she pretty much flew as normal.
I should probably note this plane has a history of losing its main gear during heavy landings. It's actually rare that I go home with the gear still attached to the plane but it's an easy fix so I've not done anything about it. Knowing this I was reluctant to land until I'd had some fun flying her. But my club mates were egging me on to try some touch-n-goes. I did a few & she skipped happily along the snow & back up into the air. Then of course on the fourth attempt I missed the snow & hit a patch of grass. SNAP off came the gear with my new skis attached. Oh well, that was the end of that for the day.
Overall I'm quite pleased with the skis. I'm looking forward to more testing, assuming it snows again. Let it snow, let it snow, let it snow!
|Jan 10, 2013, 12:05 PM|
United States, IN, Elkhart
Joined Jun 2007
Here in the snow belt of the Great Lakes you either stay inside and build or fly on skis. I have been making them for almost 40 years. I am attaching pictures of a set I made for my 1/4 scale J3 Cub. I used the original Piper document for setting the positive and negative ski angles. These take a couple of days to make due to letting them dry. You simply soak the ply in hot water for an hour. While that is going on I have time to make my form. Normally I use a 2x4 cut about the length of the ski. I cut the radius across the 2" section of the 2x4 and make sure I leave a bit of straight to clamp. Then you put the plywood in the "press" you made and use C clamps to tighten the form. Let it dry for a day. The rest is in the photos.
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