Is Shock Cord OK for the top 4 feet connected to a slalom buoy ?

swbca

On a new submersible course that I am installing this week, I was planning on using 5/16" shock cord for the top 4' connected to skier and gate markers. When the course is submerged this particular shock cord is stretched to 160%. I have adjustable shock-cord hooks for making large adjustments, but the day-to-day 3" water depth changes would be evened out by the shock cord. If it lasted 5 months that would be good enough for me. My concern is that it might forget it relaxed length when its stretched to 160% almost all the time.

cruznski

We use Marine grade 5/16" shock cord to the buoys. Our turn and gate buoys are Wally buoys. Our set up is not a submersible but has to accommodate changing water levels which is done with 7lb weights in PVC tubes that slide. I think you will be fine with it for a season. Ours are not stretched that much though.

BobF

I would suggest using latex surgical tubing instead. We used to use bungy-type shock cord, and it wears out relatively quickly compared to the latex tubing.

klindy

Use a 4’ shock cord and a 4’ poly line. Then raise the course until there is slack in the Polly (3’ below the surface?). Then when submerged, the shock.cord doesn’t stretch to 160 % and the load is held by the poly. Some creativity at the buoy attachment will allow for some minor adjustment without getting all tangled up with the two cords.

thager

@swbca I know you have a unique submersible system but my accu-sink system recommended against using bungy cord. Not sure why, but probably due to different stretch rates using same cord. Did you use it before on your first system? Might make it harder to sink and require a greater winding footage of cable. Also, at 160% of stretch the next outcome could be shock cord breakage? Still, if you haven't tried it previously it might work also.

MDB1056

For my portable course I've gone with fixed length non-bungy lines for everything. Works fine. As long as they're all pretty much the same length everything should float pretty evenly. Mine are all about 5 ft. Eliminates another variable. No issues to date.

skierjp

Best bungee on the market. Buy it at Amazon. This is what most people-use in Florida. It will last about a year and a half.
If it was me I would go with a Accufloat slalom course with a marker buoy at each gate. You could float the course in 15 minutes. Way less aggravation then a submersible and cheaper.

aupatking

@swbca you're pretty much describing our river course. Has been there since 1977. Bungee seems to last years. I don’t remember the diameter but it’s a black spool I get from a shrimp net supplier down the road. They make life pretty easy. I get everything I need but the turn balls. If I can find one of the hooks we use, I’ll post a picture. They adjust very easily but are prone to breaking over time and hard abuse (idiots on jet skis and people slinging their kids on tubes into the course). The hooks I use on our lake course (Wally Buoys) are way more durable, but way harder to adjust.

lpskier

Bungy is fine. If you want to make your life easy, only tie bowline knots.

swbca

@klindy Using poly rope as a limiter may be helpful. The buoys are 60% submerged by design, so the extra 40% to sink the ball doesn't stretch the shock cord that much further. I want the length of the shock cord to provide some consistency in the skier buoy submersion after a heavy rain. Thanks for the creative suggestion.

Skoot1123

I have used surgical tubing since we put a course in our lake. Going on 6 years at the lake and most of the tubing lasted about 5 years. (Some was broken by ice and some I replaced prior to breakage). However we don’t have as much UV exposure as in Florida.

skierjp

The problem with surgical tubing is keeps stretching and stretching

Than_Bogan

Shock cord should be fine. I've used some in the water on a mooring under constant tension and it lasts for many years. I use the bungee/rope pairing like klindy suggests, so it can stretch a few feet and provide tension, but the load switches to the (longer) rope if the bungee stretches far enough.

Don't use Adam Cord, though. He'd drown.

Than_Bogan

Note that I prefer nylon rope for this purpose, because it sinks, so the extra length of rope is at the bottom when the bungee is the one holding the tension.