Single Anchor Slalom Course?

[PhatTony]

Hi Dudes

Does anyone have any tips on setting up a slalom course for an irrigation dam? It is about 3m deep, drops to be completely empty by the end of summer.

I was thinking of steel post's driven into the base of the lake and a sub-buoy system as well. But was looking for ideas to keep the buoy rope tight as the water level lowers. 

One idea I was looking at was threading the loose end of the rope through the steel post eyelet, having a buoy on that rope loose end, but tied short, so it would be submerged, but trying to float to the surface and hence keeping some tension on the rope. My only concern is twisting of the rope?

Any suggestions welcomed. Thanks in advance.

[PhatTony]

https://www.tjhs.ca/?page_id=93

[DvarianDan Johnson]

@PhatTony - very cool..........

[101driver]

@PhatTony Really good post with excellent explanation and pictures. Really like that solution.

My old club we had a lake which fluctuated in depth significantly because of the river next to it. Normal depth was about 9 feet it could fall to 7feet but rise to 15 feet after a rain storm in the river catchment area. Cycle time from 7 to 15 feet  could be hours. We used a full floating course for years but wind and high water level caused it to drift off, we spent a lot of time resetting the anchor weights and straightening the course. When it came to replace it we did a lot of research and came up with a trouble free solution. We ended up with a fixed course but with a long wire to a very heavy anchor near the bank with the winch on. The other end also had a long tether but the wire was replaced with a nylon anchor rope 1.5 inch diameter aprox, this had design stretch and because of the length a lot of stretch. The anchor at the nylon rope end was also weighted near the bank as well. Because the anchors were so far from the course the angle that the tether ropes moved through and the amount of extension needed was minimal. As as % of total length of nylon anchor rope small and within it's design to adsorb wave shocks pull etc on a yacht. The course just came up and down with the water level utilising the yacht nylon anchor rope stretch. I only used the winch normally end of season to take some tension off because we had experienced much higher water during winter floods.

The critical element is moving the two end anchors far enough away from the course and having enough stretch rope length to accommodate the extension needed. In your case as the water will drop steadily through the season can you not just pay out some line on the winch end?

[swaterkd]

I know people who use these Duck bill anchor .  They are easy and work very well.

[swbca]

If 3 meters (10 feet) is your high water mark, and the water drops to zero later in the season, have you figured out the minimum safe depth for running a ski boat with skier ?   4 feet would be my guess.

If you end up using a second float to maintain tension,  the two floats are going to seek the same distance from bottom when the water is down to 1/2 of maximum water depth = 1.5 meters or 5 feet. If you use a 2 float setup you would have to make a mid season adjustment so the 2 float system can allow for water less than 5 feet.   Sounds like a good place to ski.

[101driver]

I also use the duckbill ground anchors, set correctly the wire rope will break before they pull out. I use them to secure boat trailers mini diggers generators etc. If you mark the low point of a boat trailer in the centre and put one of these in and lock the trailer to it, it's not going to be nice for some one trying to disc the rope off, so good deterrent. I put one in every boat bay in the shore compound at the old club. Perfect for anchoring course as @swaterkd suggested. Once you start using them you just find more and more uses as dead fast to put in.

[Nando]

My course uses a counterweight and subfloat that is essentially the opposite of the diagram @PhatTony showed (a counterweight instead of the subfloat[here in the frozen north, muskrats will eat the foam subfloats]).  The counterweights are just red solo cups filled with concrete attached to a screw anchor on the bottom that go through a loop on the buoy.  Since ours is in slightly deeper water, we use a subfloat, but if it's shallow there's no need.  Similar to @PhatTony's setup, at some point of shallow water, the counterweights will hit the bottom, but as long as it's deep enough to ski, that shouldn't be an issue...

[PhatTony]

@Nando - thank you!

With the counter weight, a couple of questions please...

Do you have any trouble with twisting of lines?

Do you have any trouble with say a buoy strike, buoy being removed/tangled and then the anchor rope sinking all the way to the bottom of the lake?

[Nando]

@PhatTony, yes, lines do sometimes get twisted and we also have some issues with weeds.  Generally, the boat wakes keep weeds clear but we'll occasionally have to jump in to untangle things if it's obvious that a buoy is floating loose or low due to tangling.  We have subfloats about 3-4' down so that we can find things.