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i need help with my ramp building

post #1 of 6
Thread Starter 

ok so the other day i built a ramp that is about 5 and a half feet high. the hill that leads to it is 60 feet from the top to ramp. the angle is about 36 degrees at the top and the ramp is on an area about 10-15 degree pitch. the ramp is 43 degree so it will probably get me way up there. is there any way of knowing how far im going to go so i can build a down spot because if not id be landing flat.... this is my first time ever building a ramp and any help would be very much appreciated.




post #2 of 6

There is but it is more math than I am willing to do right now. You need to find or at least obtain an estimate of the coefficient of friction between the snow and your skis. Then you can use that and the angle of the hill along with its length to calculate the speed at which you'll hit the ramp and then from there its simple kinematics to determine you're trajectory. That is unless the ramp is a different material then u need the coefficient of friction for that to calculate how much speed you will lose before you leave the ramp. Even if you do all that it will only give you a rough estimate.


If you do not have a down landing I would not attempt to use that ramp. Landing flat from the heights the ramp will send could cause serious injury to your knees or your face if you try to absorb the landing and then hit your self in the face with your knee ( I have seen it happen). 


Edit; At 43 degrees this ramp will send you more horizontally then it will vertically. 45 degrees is an even split anything higher starts to increase the ratio of height to the horizontal distance. ie higher but not as far

post #3 of 6

It's all about speed. Build it small to start, and adjust your speed accordingly. You're worried about overshot, but that's a problem of too much speed. Once you have a good feel for the hill and the feature, you can start adding size to it, and speed as well. Take it easy and build up the ramp size and the speed slowly. The big thing to remember is that you want the angle of your down to be about the same as the lip, or at least not less than the lip. If it is, you're still going to be taking way more impact than you should.


I'm sure there are complex physics problems you could do to exactly calibrate the ideal angle and length based on speed and mass, etc etc. But I've never used any, and I seem to survive most of my airs.

post #4 of 6

So you've got 60 feet of hill before a 5 foot kicker?  I guess I'm having trouble visualizing what is on the landing side of the jump right now.  I'm assuming there is more hill past it.  I probably would have started about with a jump about half that size and just hit it to see how high and far it would send me.  Then you can get some ball park idea of what kind of additional landing infrastructure would be needed for a larger kicker.  I've got an old USSA Freestyle rulebook somewhere around the house, and I think it has a drawing and dimensions for the jumps we used in the 80s. 




The steeper the kicker the less distance between the jump and landing.



Regardless, it also depends on what kind of hill you have to start with unless you are also building a full tabletop.

Edited by crgildart - 11/8/10 at 4:17am
post #5 of 6

If you know your speed right before you hit the ramp, I could help you. It involves kinematic equations (physics)


post #6 of 6
Thread Starter 

thanks everyone... i think im going to build a small tabletop ramp next to it to get an easier look at it then i can just do a little math and fix problems with the bigger one.

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