Floating docks... need help brainstorming

[notfarnow]

The floating docks at my wife's family cottage are beat. I should be able to repair them enough to get another year out of them, but they are poorly designed and definitely not worth recreating as-is.

In the past, they've pounded steel pilings in (2" pipe) and the dock rests between the pilings. Problem is, the bottom is silt for 2', and then solid rock. Invariably, they get pulled out every few of weeks and have to be sledged back in. Plus, having large, mangled steel pipes jutting out at odd angles is less than ideal on a dock where kids are running and playing.

So anyway, I've been eyeballing different setups for ideas to use next year. For the docks themselves, I'm thinking 4x10' pressure treated sections on plastic 55gal floats. What I'm really chewing on is how to keep them in place.

Considerations:
-about 30' long
-must be able to dock boats with 6' draught
-Tide is about 3 feet

The final contestants are these two:

Option 1: moorings


Two heavy, permamnent moorings are placed at the sides of the dock, and chains are run from the opposite sides. Weights can be placed on the chains to help keep the dock centered.

advantages:
-Clean design, with no steel pipes sticking out
-Easy to set up each spring, just hook up to moorings (once you find them)

disadvantages:
- dock will sway and wander with wind & waves
- Have to be careful that boats don't get fetched on mooring chains
- moorings can be hard to locate in the spring

Option 2: cradle


A steel cradle is welded up out of 2" pipe. Two bars come up out of the water, and the dock slides up & down with the tides between them. The cradle can easily be carried by two people, weighs as much as 2 sections of scaffolding. Once in place in the water, it's weighted down with about 20 2'cement patio blocks.

advantages:
-Solid: dock doesn't sway or shift with wind, tide or waves.
-No looking for moorings every spring

disadvantages:
-Don't like having the steel poles jutting up
-the 2' patio blocks could be hard to place & remove if the dock is in 6+' of water.


Anyone have any thoughts on this? The easier to set up the better, but the most important thing is making something solid that I don't have to frig with all summer long. I'm really curious to see what setups you guys have.

[Rot 911]

Jake that is a large difference in elevation between hi and low tide for a floating dock. Do they even use floating docks up there? We have a very large (60 mile long) lake close to where I live. They raise and lower the lake level in the winter for water for the hydroelectric dam. The difference is about the same 3 feet. The docks sit on encapsulated foam blocks with cables holding them in place with the shoreline. The walkway running down to the dock is hinged at both ends to pivot with the rise and fall of the lake level.

[notfarnow]

Kurt, some guys use the fixed aluminum docks you take in & out each season, but with a 3' tide it can make tying up boats a real pain. The people on the other side of the cove had a floating dock, but it got beat to hell in a storm. Our side of the cove is better protected.

Cables are a neat idea... the walkway keeping it pushed out and the cables keeping it straight. Only problem here is that I'd be out over 30', and the whole length will be dock, so the cables would be in the way.

[Chocaholic]

We have a similar arrangement. Because we're in a serious drought in the SE, our lake is almost 12' below full pool. Our dock (and all of them on our lake) are not anchored to the bottom at all. They are on encapsulated floats and are anchored to the shore-line via stainless cables on a reel. That way it's easy to move it in and out to adjust for the water level (chase water). The walkway is hinged on each end and we have retractable wheels at the beginning of the walkway.

Draft is not an issue (unless your water is too shallow), nor is weight. You might be over-thinking it a bit. Here's a pic:

[Overpaid Slacker]

Jake -
I like the cradle idea, and the uprights don't need to be out near the end. You could probably put it even less than 1/2 way out, and I'm sure you'd find some utility to having a couple of "storage posts" there.

If the tip of the dock is moving too much, you could use 1 weight directly under it. As for finding it in the spring, just tie a painter to it that you run back and secure to shore.

Good luck!

JP

[VINMAN]

Jake, just curious, do you have to submit plans and get approval with the local Gov? Around here we have the DEP and sometimes Army Corp of engineers to deal with, any time a dock is built.

[notfarnow]

You need to get approval if you are building anything that is permanent (like a concrete dock) or even semi-permanent, like a dock with cribwork filled with stone/rubble. As far as I know, even fastening into rocks along the shore has to be approved. That's only for environmental impact though, nothing to do with safety.

I think you'd have to do something pretty wild before anyone asked any questions. The only person I know of who got in trouble was a guy who poured a concrete pier that his dock attached to. He poured it right on the beach, and it went out 6'. It was ugly, stupid and stood out like a sore thumb. His neighbors complained and it had to be jackhammered out.

There used to be a full dock on the other side of the property, and some of the cribwork is still there. It would be a ton of work though, and that side is right in the prevailing wind. Plus, it would get beat up every winter. My wife and mother in law think that could be neat, but I have NO interest in building or maintaining something like that.

[911boost]

In northern MN the docks are hinged near shore, and during the winter lifted out of the water via a cable and pully system. Since you have such a difference in the tide, maybe a modified version of that idea would work. On my friends docks, the dock is supported by steel poles that attached to old automotive wheels. They act as the feet.

Would it be possible to have a floating dock, using the floating methods that you described, but use the same time of "feet" as some of the docks I have seen. Meaning, you could build a framework uder the floating part, and have sleeves slide over the poles. I hope I am making some sense here. That would allow the dock to raise and lower.

Bill

[notfarnow]

Originally Posted by BSiple

In northern MN the docks are hinged near shore, and during the winter lifted out of the water via a cable and pully system. Since you have such a difference in the tide, maybe a modified version of that idea would work. On my friends docks, the dock is supported by steel poles that attached to old automotive wheels. They act as the feet.

Would it be possible to have a floating dock, using the floating methods that you described, but use the same time of "feet" as some of the docks I have seen. Meaning, you could build a framework uder the floating part, and have sleeves slide over the poles. I hope I am making some sense here. That would allow the dock to raise and lower.

Bill

That sounds a bit like the "option 2" above. The dock would have sliders that would go up & down the steel pipes with the tides.

I just wonder how much weight it will take to keep something like that steady. You get a good wind pushing against the floating dock and a boat tied to it... that's a lot of force.

[911boost]

Thats a good point, if you used the same type of "feet", you could always fill the tires with cement. I am guessing that would hold them steady.

Bill