Need help on anchoring jump ramp

[SundevilSki]

[Moving this here from boat talk] Long story short, we've been fighting with our ramp for a while and i'd like some ideas on how to anchor it so it wont move. We have a very unprotected site and have some strong (40mph) crosswinds from time to time. The last anchors we had in place were 4 plastic tubs filled with ~400 pounds of concrete each, on each corner of the jump. Our lake level fluctuates about two feet several times a year and last time we had the jump in place, we think the lake level went up and pulled our anchors out of the mud (we have a deep muddy bottom) and the wind started dragging the jump around the lake. What is the best way to have the jump in a permanent position, while still allowing for lake fluctuations?

[Bruce_Butterfield]

For a muddy bottoms, danforth anchors work great

https://goo.gl/WwB6rr

I think mine are the 24" version that are $40-50 each. Just need to set them by digging the prongs in and being sure the angle is reasonably shallow. They have more holding power than you would think.

[Bainesster]

woah 400 lbs anchors getting moved by the wind, and I thought salt water could not melt steel cables

[paul]

we have 1200lb concrete anchors (4'X4'X1') tied to 3/4" poly rope. The rope is 150ft long and we are in 20' of water. This gives us a very shallow anchor angle. We also have tires between our winch lines and our poly rope for shock absorption. To get the anchors into place all you need to do is pour them on a dock, put some pipes under them once they are dry, float them into place and push them off the dock. Cheap and they are not going anywhere!

[Nando]

We have large screw anchors- the type used to anchor mobile homes- 36" long, with 12" diameter augers. We screw them right down to the bottom (it's pretty firm). I also used these for a cable course. Kind of a pain to install in deep water (you'll need scuba) and your fluctuating water level will still require adjustment, but with these on three separate lakes, we've never had a jump move.

[LeonL]

We use screw in anchors. We did have one pull out during a really significant wind, skirting edge of a hurricane. Other than that we've had them in for 19 years. If you go with a really shallow angle of anchor line, you have to be careful when getting the boat near the jump.

[SundevilSki]

We have a lake liner so screws are a no-no, and there also are no floating docks on our lake.

[SundevilSki]

Can anybody comment on using large pyramid-type boat moorings?

[Nando]

What kind of liner and how much sand/fill is on top of it? Depending on how much soil there is, you may need some sort of flat anchor so that it's buried. On a plastic liner, keeping them from getting dragged will be tough- as you know well...

[Edbrazil]

Here is what we typically used when Tour-ing. 4 anchors at about 1,000 lbs. each. Make

forms from 2x10 12-footers. Cut into 4 equal pieces, and bolt together as a square.

One 'yard' of concrete makes 4 of them. For lines, use 5/16 braided nylon or 3/8 poly.

 

Only failed once, in a 2 mph current and when a boat threw a big wake at the ramp. We

also used to 'pin' them to the bottom with big tent stakes, but looks like that won't work

since the bottom has a liner.

 

See the picture for the layout. When not in use, slack off the front anchor cranks a bit,

in case the water level comes up.