Course Mainline:How to make one?

[André]

Ok,so after getting Perfect Pass,i need to update the course.This is a permanent may to october installation in about 10 to 12 feet deep. I Plan to still use individuals anchors for the skiers buoys but want to built a mainline for the boat path.I want to use 1/4 inch poly pro rope but have some questions for you guys that done this before.
How could i put the 2 boat buoys hook to one mainline if i don'y use pvc pipe for arms?
When you use arms,does it do anything for flotation?
I don't think i understand how the course is tie to the 2 anchors and why the mainline doesn't bend in the middle of the course.
Any ideas,drawings(that would help a lot,i'm a visual),or pictures would be welcome.
I know that some course manufactures like Insta Slalom and E-Z Slalom sell some guides to build those.If anybody is willing to share,that would be real cool too! :toast:
Again,any ideas are welcome!
Thanks!
:popcorn:

[east tx skier]

Andre, since you're the one that taught me how to do this, it feels odd giving the info back.

I bought around 975 feet of poly rope and marked the pertinent measurements along our pier, then measured the rope by laying it out on the pier and having someone hold it taught. I marked the measurements by affixing a zip tie in place and attaching duck tape to it (wrote which ball or whatever on the duck tape. I had temporary buoys tied to each marker point so I could find it easily. I used pvc pipe for the boat guides and gates. I measured out the distance from far gate to the corresponding turn ball and drilled 3 holes (one for each gate and corresponding turn ball. Using a pvc four way adapter, I had a perpendicular piece of pvc that I used to line it up on the mainline.

I anchored the mainline at both ends. When all was said and done, due in part to the lily pads with which I had to contend, I had a very crooked course. None of the turn balls lined up. If you use pvc, use varying sizes and make it telescope. But, in my opinion, you're still going to get a little bend, and so, as you'll see below, I think a bit of taught rope and a good pair of eyes is more accurate.

Taking your advice, finally, I got about 300 feet of poly rope and marked off the various necessary measurements with it. With one person in a john boat, and two in the water, we checked the measurements on the boat guides. They were correct. But since it wasn't straight, the man in the boat lined it up. Between lining it up and checking the measurements (trial and error), we'd get everyone to agree. We did this with all of the gates; then we went back and measured and sighted the turn ball on the corresponding gates (more trial and error). It got dark and it was late September.

This season, I'm going to double check each side of the gates with the measuring rope (not the 950' mainline). I can also check the diagonals between the turn balls this way.

We have one reference line that goes from the dock to the 3 gate. From there, using our measuring rope, we can find and buoy the entire course in 15 minutes.

So, having just done this. My advice would be that, short of a surveyor, doing it like you have done it in the past (with individual anchors) is a quite accurate way to set it up. A poly mainline (if you're not laying out a complete portable course) tends to be a little more trouble than it's worth.

What's wrong with the course that you have? It might be cheaper to hire a surveyor to check your measurements than invest in a mainline (but I haven't priced this). Rope isn't cheap though. If you do go with a mainline, plan to anchor it with something pretty substantial, like and old engine block.

On the MBO board, there's a homemade slalom course "how to" using a mainline. The EZ slalom and similar setups use diamond patters at the gates, to which the PVC pipe (telescoped) attaches.

[André]

If i would be the only one using the course,i think i would still go for individuals anchors but PWC,tubers slaloming the course behind i/o sometimes catch a bouy of the boat path and sometimes moves them before my bungee cord break even with 2 concrete blocks and a steel pipe.I'm affraid that with PP if one of the magnets is move it will send Perfect Pass crazy!!!
But if i don't come up with a good idea for the mainline ,i will keep on using individuals anchors for the both path.
It's not like i'm going for the world record but would like to keep the course within tolerance.
By the way,i'm moving to "Real subs bouys too...LOL

[east tx skier]

I invested in some real subs over the winter, as well as magnets. I don't think a misplaced magnet will cause the PP to go crazy. The magnets are just for timing. It's not going to adjust RPMs on the fly to bring an off time into tolerance. You'll just get a crazy adjustment suggestion at the other end of the course, which will tell you you've got a problem.

We'll be pulling our buoys out when we're not there and thc course is right by our dock. Fortunately, we don't get jet skiers on that part of the lake as they're mostly on the river. You have to be looking for our cove to find it because it requires that you leave the marked channel. Thus, if you don't know the right way to go, you're flying blind in a lake with lots of stumps in it. For us, it's a beautiful thing. The only company we have is fishing boats, and after a few passes, they leave.

Perhaps more substantial anchors is the answer. One block is plenty for what we're doing. The bottom is very muddy and makes for really good suction once it's set. Basically, that block isn't coming up unless you get underneath it and really give it all you've got. You might want to pour some blocks with re-bar in it.

We use surgical latex tubing (3/8") instead of bungee. Pretty durable stuff. Got 10 10-foot strands on ebay for $9.99, which is cheaper than you'll find anywhere. 3' per buoy is plenty for what we're doing.

[André]

Sooooooooooo,the magnets WILL not affect the rpm,and the display shows the time of the pass base on the magnets?
Sound stupid but i have never came close to a Perfect Pass.
I only know that i NEED one! LOL

[east tx skier]

Basic magnet setup will be entry gates and exit gates (both sides and the 3 ball (in either direction). Some people add the 1 ball gates (in either direction). Some people go all ball timing, which was bound to happen since it's just four more magnets. For what I'm doing, the first setup was plenty (of money -- around $80).

Thanks to lawyers like me, you'll be hard pressed to get the sort of answers that would be helpful on magnet depth. People that sell magnets will tell you to put them as deep as you can because they don't want you to somehow snag a magnet and sue them. The speed control folks will tell you to run it as shallow as possible (right under the ball) so you can get the most accurate reading (there's some issue about surge off the one ball (see below)). Most people I've talked to tend to run them right under the ball and haven't had any problems. But the lawyer in me causes me to now say, I'M NOT INSTRUCTING YOU ONE WAY OR THE OTHER. :D

This part is from memory, but the perfect pass manual details it well. After you put in your weight and crew weight (if you have passengers) and some basic info about your boat and motor, you'll set your baselines by running the program in slalom and setting it for the various slalom speeds in either KPH or MPH. At each slalom speed, just give it plenty of RPM to get to that speed (but don't over throttle). The control will take over when it gets to a predetermined RPM for your engine/boat. It will also beep at each magnet location (assuming your pickup detects the magnets. Once you go through the course, bring it to a stop. The control should display your time and suggest that you increase or decrease by x number of rpms by pressing ^ = yes. You press ^ and run it through again. More than likely, it will tell you you're in tolerance for a pass at that speed. Just work your way down the slalom speeds to 25 or so and you're done.

Now, when you run the boat through the course, at the end, it will either tell you that you're within tolerance or ask if you want to adjust your baseline. I don't think it makes adjustments in the course although I've heard that it can surge off the first ball to get up to speed. I haven't experienced this in my first year and a half of use.

[André]

Get it.
That's why you need an accurate course if you're running with the magnets and adjusting your speed when ask by the display?
If your course is "short",the timer will think that your running hot and ask you to lower the rpm ?
Tried to download the manual,but something is wrong with the Acrobat thing,surely on my side.Dawn hamster is tiring...

[east tx skier]

I don't think the mainline that you make yourself is going to be any more accurate than just measuring buoy to buoy. Even without underwater obstacles, the more rope you have, the more stretch there will be when it is taught (even in low stretch rope). The only way to be absolutely sure is to have it surveyed. When I run my baselines on our course, I'll keep the gps running and compare. If you look at the slalom course deminsions, there's an acceptable margin of error there. By my measurements, mine was accurate to the inch. So if my measurements are off, I'm probably still within acceptable range.

If you're intent on using a mainline, but plan to leave it in year round, go with stainless steel. If you're just using it to measure, there are several places that sell rope in bulk. I needed mine fast, and spent the extra money to buy it at Lowe's. In the end, I wish I'd just bought 300' and done it the easy way. But at least this way, I won't wonder if it could be more accurate.

[André]

Maybe i will stick to my individuals boat guide system and only drop the concrete blocks for 2 steel plates of about 30 pounds each with a steel pipe welded in between
to keep the right distance between boat guides like a dumbell with a eyelet at each end to tie the ropes,subs,bungee and buoy.
Work in progress...

[east tx skier]

Since you've already got it set, I think it'd be easier to bolster the anchors on what you've got. If you're really concerned about accuracy, get it surveyed.