Slalom Course Advice For Public Water

[WIRiverRat]

I have been putting a course on a public river for the past two years and am getting tired of having to fix something every time we go out and ski. I have introduced a new ski partner to skiing the course and he has access to divers/survey equipment and is willing to help install a permanent course. We have two challenges that I hoping someone has experience with:

(1) River levels fluctuate 5 feet from spring to fall so the course needs to be adjustable.

(2) When the river is low part of the course is only 4.5ft deep. With the need to allow the bouy to raise up we can't just do the traditional subfloat to a line with a counterweight.

 

My thought is to use an augered earth anchor at each bouy. Attached a triple pulley block to that and run SS cable to another triple pulley block on a sub float. This way for every foot the subfloat goes up or down the bouy could move 6 feet. Has anyone ever tried a set up like this? Suggestions for augers? Suggestions for a pulley that will withstand a river?

 

I would really like to keep my sanity and spend time skiing instead of course maintenance.

Thanks

[MNshortliner]

No experience with river courses but my course is on a public lake and I have earth style screw anchors at every bouy , I also have another clip around the thick screw anchor metal to attach the clip to. It is in about 5.5' of water and about once or twice a year I have to adjust bouys due to water level. I bought a heavy duty bungee cord from ebay that is a pretty good thick quality and goes from the bouy directly to the earth screws. So about 6' of bungee cord. I drilled out the eyelet of the bouy just big enough to get the bungee cord through and tie a granny knot at the bouy end. On the other end I go around a dog leash style clip and double back the bungee cord to itself then use stainless steel hog clips to secure the bungee on the leash hook. Then when the water goes down through the summer I pull the bungee cord through the bouy eyelet and add another granny knot to the right level so the bouy is exactly floating where I want it. I only have a max of 12" extra bungee. With your 5' water level change this could work if you tied the extra bungee back to itself so it would not catch skiers or prop/rudders. Hope that makes sense. If need be I could get a pic to post. Also I would go with 24" screw anchors over 18" anchors.

[MNshortliner]

Earth anchors are from Fleet Farm in the farming section. Painted bright orange and very thick metal.

[WIRiverRat]

Do you have a link to the bungee you use? This system is very simple and simple is a good thing. How much fluctuation in water levels can you get before you have to retie the bungee cord? We are on backwater of the Mississippi River and levels and fluctuate by a foot or two every week. I'd like to avoid having to retie every time we ski but if a 6ft bungee can give 2 feet or so I think that would be a good solution.

I have found the earth anchors at farm and fleet. Looking at the 30in anchor just for some added security.

I went to ski last night and someone had broken a pipe and the mainline in 2 places on my current insta-slalom. Looks like I may be doing this project sooner than expected. From what I have seen I need to make this durable enough for the wake surfers who decide to run the course with their boats fully loaded with ballast. Yes we have seen them actually do that.

 

Thank you for the advice. Where in MN are you located? I am right on the border and always looking for new people to ski with.

[h2onhk]

@WIRiverRat , thats a tough situation. I'm assuming since you are in a backwater area you don't have to deal with debris during high water/flooding?

[PatM]

The MAN for all courses is @Edbrazil . He has come across it all and invented 80% of the solutions. You should PM him.

[WIRiverRat]

We don't get too much debris coming down the river, just a few logs in the springtime but that is usually before the course is in. After reading MNshorliner's comments I found some heavy duty 1/2in shock cord. I am thinking an earth anchor with a SS cable to a subfloat from skier to skier then do 1/2in shock cord up to an adjustable plastic clip from skier to skier. The shock tube is supposed to be able to stretch up to 125% of its length so maybe I would only have to adjust the clips a few times a year. Keeps it simple.

We are hoping to do a detailed bottom survey of the river so we know all the depths and then overlay the course on that survey so we know the GPS coordinates of each ball and give those coordinates to the divers. I have put in lots of courses with PVC and cable but never anchors. Hopefully this approach works well.

[jetpilotg4]

@edbrazil is like farmers insurance. He knows a thing or two because he's seen a thing or two

[wtrskior]

I wouldn't use a bungee for your leveling.

 

There are a number of methods to make an auto-adjustable buoy line using hollow core rope (ski rope) or a counter weight on the buoy. 5' fluctuation is not bad at all, the issue you will have is the minimum depth is pretty shallow! I'd think you want to use the earth augered anchors and the subs at a static 2' or so.

 

concur on asking Ed. He has a finger trap method for fidding rope

 

 

[MNshortliner]

I believe the bungee cords I have are the 1/2" but they do not stretch a whole lot with only the buoy tied to them. I would say only about 6" for a piece that is 5 1/2' long. The buoys simple don't have enough float to them to stretch the cord. If you had a smaller diameter cord it would probably stretch a little better but wouldn't be as durable. Be sure that the cord is made of small round diameter rubber strands and not compressed crap rubber that has no consistent shape to it. I bought that the first time and that bungee was pure crap. I am in Inver Grove Heights (South Metro) during the work week but live NW of Alexandria, MN. I am always looking for other to ski with also. Where are you located on the boarder?

[WIRiverRat]

I am down in Lacrosse. If you are ever this way shoot me a message and bring a ski. It sounds like the bungee cords won't stretch enough for how often our levels change. In talking with ski partner last night I think the new plan is do a depth survey this fall and try to find the correct positioning of the course so they we have a little bit more depth at each ball. Then just do the traditional anchor to subfloat to a bouy with counterweight. Any advice on a good counterweight? When water is high it will be hear the surface, want to make sure it's safe on the boat if the driver swerves a little bit.

[wtrskior]

 

skiertoskier.com

 

http://www.skiertoskier.com/Magnets/fingertrap.jpg