Introduction: Making a Curved Snow Ramp
A few friends and I took advantage of the unusually large amount of snow that dropped on us over snowmageddon and built a sled run. Mind you, it wasn't our usual straight ramp, this one was banked and we were going to start it off with a steep start (going down a flight of stairs). We built the ramp and tested and fixed things over and over and by midnight we had a pretty good run that started at the bottom of the stairs. By that point we were pretty exhausted it was too late to do as much work as was needed to finish it all the way up the porch steps.
The next week, however, we were able to go back and finish it up. By the end we had the sled shooting out the end fast enough to potentially cause injury (fortunately there haven't been any). Lots of stuff was learned and will be utilised in next years project which will be epic to say the least. Perhaps it could be considered to be a low-speed luge?
Step 1: Layout
First you need to plan the layout, this is a critical step because if you don't plan ahead, you will probably spend hours refining everything. Since I know this hill by heart, I have no need for the satellite imagery, but I've provided it to give you a top down view of what's being built and a pattern of the resulting exit angles (based on where we hit the dock).
sattelite inage credits: Google Earth
Step 2: Snow, Snow, and More Snow
Snow. As your primary (and probably only) construction material, its importance cannot be expressed enough. Whether your run is straight or curved, if it has a ramp at the end or not, you need snow and lots of it. You don't need 4+ inches of snow on the ground of snow to get started, but if you want to do any sort of course modifying or fixing, you had better make it look like you have more, and that means getting out the shovels and moving some snow!
Initially you need a 'service ramp' of sorts. This will: A) make it easy to walk back to the top, B) give your ramp a side to conform to, and C) make it easy to fix mistakes, shave down bumps and fill in gaps, add or remove snow, make jumps, etc. For straight runs one pathway will work fine, but if you want to do anything more complicated, you'll need two, especially if you're banking and are in need of reinforcement. Your paths will mirror the ramp pretty closely, and should be wide enough to move sled-fulls of snow where they're needed.
Once a path is cleared, guide an unloaded sled down where the ramp will be allowing room on the sides for integrity. Evenly pile snow on the track and tamp it down, do the same for the edges. Do a few test runs with a lighter person to compact the snow and gauge where alterations are needed.
Step 3: Modify, Test, Fix, Repeat
This was the part I had the most fun with, building and re-building and fixing and modifying the ramp to get it just perfect, to alter the flow to get the fastest results, figuring out why some things weren't working, figuring out what was giving us problems and how to correct that, that was fun. After we had a few runs in, we started moving in sled-fulls of snow (about 3 cubic feet uncompressed per load) to fill in the area in front of the window (which required a buildup of about 3-4 feet of snow to be level with the plan) and piling snow along the outside edge for banking. Doing that properly requires a lot of time compressing, profiling, more compressing, and more profiling.
Since I designed this ramp to be fast, I banked it that way from the beginning. Initially that was a problem because we hadn't got the ramp up the stairs the first weekend, but on the second weekend (and 5 more inches of snow, woot!) we got it up the stairs and that pretty much solved it.
Remember: Lower is slower (in terms of banking)
On a side note, continuous testing is critical because if not, you'll probably fly off in the wrong direction or have a rollover (we had both numerous times).
Step 4: Additional Notes
Receiver ramp/crash buffer:Since we built the ramp on one side of a frozen pond and theres a dock right in our way, we kept hitting it. with the initial ramp version, a recieving end wasn't necessary since we weren't hitting the dock fast enough for it to be an issue, but as soon as we added the stair slope, we started running into it much faster. My friend smacked into one of the dock poles and cracked the front end of the sled and I ran into one and knocked a light off. I thought it would be a good idea to make some buffers to redirect the sled and passenger between the poles and some ramps to get the sled safely over (though at the time it was more of a fun thing than a safety thing).
As minor as it seems, its quite necessary if you dont want to keep steping on the sled run. you need one on both sides clear for construction reasons.
Edge fortification (the buttress):
We used wood planks to keep the snow from falling behind the steps and narrow cinderblocks to fortify the edges (packing the snow is okay, but if space is a commodity you need something more).
Photo credits to Denton Mitchell and Lin Deahl-Coy