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Retractable Slalom Course


Skoot1123
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The developers at our lake were attempting to do this, but Dr. Jim came along. Additionally, the lake silted up a little and buried the cables/pullies. With the added complications, it was going to be a difficult thing to accomplish. Glad we don't have to deal with that maintenance nightmare.
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@Kelvin - do you recall how far from the bottom of the lake the cables and pullies were? I figure with any lake there will be silt and sediment, so we would need to make sure the pilings are sitting up above the silt layer.

 

@sunperch - haven't thought of that, but I see where you are going with it. HAHA! Actually we would do this so we can pull the boat guide buoys and/or turn buoys under water while we barefoot and wakeboard.

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@Chef23 - we thought about a submersible course too. Problem that I see/think about with a submersible course is the time it takes to submerge it and bring it back up. Air lines can create a lot of problems...but then I suppose everything can in the long run. Figured a pulley system would have fewer parts than a submersible?? Just my two cents.
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Wally skier really figured out the issues with the previous sinking slalom course - Accufloat irrc?

 

Instead of using an integrated weight/air chamber that sunk to the bottom, the wally skier system uses separate ballast bags, hung below the course balls on a 1:1 ball/ballast set up.

 

Each ball then also has an air chamber, which combined with the inflated ball lifts the arms up.

 

The next improvement that Wally made over accufloat is that his air bladders are flexible, not rigid PVC. He uses a reversable diaphragm pump, so that you can use it to put air in and raise the course, but when used on vacuum mode it sinks quicker AND removes water from the system. Such that if a component/junction does link that water won't accummulate in rigid floats, but instead is sucked out of the system through the pump, which the bags deflate and allow this to occur.

 

Combined this means a course that can be positioned in variable depth water, as you can adjust the length of line to the ballast bags such that all the balls drop 5-8' underwater, and when you pump it up they all rise the same distance before the balls break the surface. Meaning = tension on line, no bowing etc.

 

If you wanted one that was mechanical you add a few issues. Firstly, you need to pull EVERY ball down. So assuming you aren't using PVC booms, but solid anchors, you would need to run pullies and ropes to subbouys at every station, the anchors would need to be very secure such that the system did not foul. I would probably consider then running a flexible tubing such as PEX or irrigation tube from every bouy to a centerline area with your cables run inside individual tubes. You could probably branch off such that each set of balls (boat guides and turn ball, gates etc.) pulled off one line. But you'd have to be careful to set all the slack properly. This to me means adjusting at the ball, and probably using crimps such that they would all "stop" at the surface under sufficient tension to stay put.

 

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I've had an accu-sink course for 11 years now. Only problems I've ever had I caused myself. For example, once I brought the course up and closed the air valve at 20 psi. Everything went great until I drove between the gates and ski buoy and hit a floating bow of pvc and cut the air hose with my prop. Luckily I had a line splice in the glove box and fixed it in a real hurry. People I know who have had problems pressurized their systems too quickly and over-pressured the bladders and or the airlines. I've learned to bring my system up to just under 18 psi and then release pressure to 10 psi before I close the valve and use my slalom course. Occasionally a fisherman will catch an air line and put a small hole in it. Plastic electrical tape wrapped tightly and covered with a couple plastic hose clamps fixes that problem easily. I get a free lure. If a few buoys won't sink I use a hand pump to remove any water from the lines. This always fixes that problem.
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Idea 1.

 

Neutrally sinking bouys - balanced to eventually sink.

 

With individual anchors, and sub bouys constructed of a bucket with sufficient weight to sink the ball, plus an airline, and a vent hole in the top. SUCH - that during use regulated airflow from a landbased compressor fills bucket with air, which slowly trickles through top during use. After skiing shut the valve and the air eventually self purges and all balls submerge. Time to ski, valve opens course rises, compressor runs ever X minutes.

 

Skiing is usually < not skiing if you are worried about submerging a course.....

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WOW! Lots of information! Thanks much! Nice thing is that we have a bulk of the expensive hardware already available. Not the buoys - but the SS cable and clamps etc. I have a diagram I'd like to scan in and share as well. Will comment more on it when I get a bigger window of time!
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In the late '80s I skied a few times with a guy who had a course with individual anchors with pulleys or loops and all the lines were attached to a single point (a large teflon-coated steel loop that he stole from some industrial application that was anchored to the bottom), then routed to his boathouse where he had a garage door opener which pulled everything down about 4' and raised the whole course with the touch of a button. There were a few similar courses in MN then. I remember that it involved LOTS of rope and had to be carefully adjusted, but it can be done. The stress on the individual ropes is low, because they're only pulling down one ball and even with all the buoys, the total pull isn't much. I suspect that there's even more work with this setup than with a Wallysinker or Accusink, but... Some other old farts must have more information...
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Skied with a guy that had one in MN. He put it in when our lake was drained for Hydo dam repair. He used mobile home anchors as points of attachment. He could raise and lower with a hand crank trailer winch attached to a dock post. He had a loop many feet short of the winch were he hooked it to a concrete anchor well under water for the winter. I never saw it when installed but used it for several years. Worked ok but not in the best location and was abandoned.
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Some of the guys I ski with at a former lake built a nice sinking course. I did a write up on the water ski forum, but that's gone. I think Ed put it on his EZ Slalom website, but I can't find it. I'll look around for the pictures I took.

 

Basically, they put a combination of rocks and a small wheel/tire in a 5 gal bucket under every buoy. It was neutrally buoyant with air in the tires. When you let the air out, it sunk. They had a hose leading to each bucket/tire and it led to shore. Take a portable compressor to that hose and it would fill all the tires at the same time. Took apx 10 min to rise and sink.

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@clemsondave - I think I have seen that article before. Not sure where it was but i remember the pictures of a bucket/gravel and an old tire/wheel combination. I too was wondering if Ed at EZ Slalom had any experience with this type of setup.

 

The idea we have actually doesn't use any pulley's, but rather eyelets that would be attached to the concrete we'd pour in the bottom of the lake (~8ft deep). As long as the eyelets were oriented correctly the pulling force wouldn't be too terribly high. If someone was able to pull the course down with the handcrank - it seems then that the force isn't all that high. We would probably put some sub-buoys in to make sure there is enough bouyancy to overcome the friction of the eyelets. Of course if that doesn't work we could go to another option/way, but I'd rather do it right the first time!

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With 8 ft of water I think the sub-buoy/ counter-weight system might be best, as long as it is reasonably clear. You can float it/ sink it in about 20 minutes, and have a nice accurate course with little chance for issues.

 

I'm in 50' of water for my public lake course, so I have a Wallysinker. Works pretty well but there is a bunch of work involved in getting it right. I bought mine second-hand, which didn't help. It comes up in 15 min but we have it set a little deeper due to fishermen and boat traffic. Get the bigger pump if you go this route.

 

The 5 or 10 minutes you might save for an automated system versus clipping the balls on and off will literally take years before they equal the time to install and maintain a sinker. I've been told that 20' is about the max for the sub buoy approach due to accuracy, which is why I went with a sinker.

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@clemsondave and @Skoot1123. We've changed servers for the web site 2 -3 times since we posted that article on our web site so it got lost in the shuffle somewhere. I still have the photos though, and I may still have a copy of the file for what was on the site but I'll have to do some real digging to find it. I've posted the photos I have, maybe Dave can offer some narative to go with them.

 

The only opinion I'd offer on any of the above suggestions would be this - the more mechanically complex whatever you put into the water is, the more maintainance and headache you create for yourself. A lot of good ideas in theory, but as always the devil is in the details. Add water and expose it to the public water Wally's... My design mantra has alwas been pretty much to opperate on the KISS principle. The more mechanically simple it is, the less you'll end up having to screw with it.

 

Ed

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