well to surface the ramp first (oviouslySP?) put plywood then it is usually astro turf (the plastic stuff that the use in driving rang's work the best.) the regular astro turf is ok but absorbs alot of water so you have to keep watering it down. it also gets really heavy if it isn't dried out. and construction fencing i dould was the fastest but the easiest to wreck your bases. this is becasue you have to staple your fence onto the launch ramp and you skis will end up running over the staples and there will be some guages in there.
another option to make a drop in ramp slippery with REGULAR astro turf, put a whole bunch of your no-name laundry soap or dishwaser soap. it can't be the liquid unless you want to spend $6 every time you jib your yard. so if you buy that just load it all over your turf and put your hose on a mist. don't drench your turf whie the turf is on because then your lawn will get all meeded up from the soap.
hopes this helps.
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