OK, the floating dock is starting to come together and I am trying to noodle out the anchor foundation at the shore and could use your input. I have attached three sketches. The rendering is of the dock itself is for size reference, The first sketch shows the gangway and the hinge mechanism while the second sketch shows the poured concrete anchor/foundation with just the hinge plates penciled in for clarity.
Will this set up be sufficient? I will drive 4 "T" posts as deep as I can get them into the dam an cut them off about foot from the dam surface so that the concrete has something to grab a hold of. My dam has a lot of rock in it and I fear that digging in it and driving post in it will be a lesson in patience, not to mention dealing with the water too. I might even try to post hole dig down an extra foot in a couple places to make a resemblance of sono-tube piers beneath the rectangular chunk of concrete.
I think the floating portion will need something to stabilize side-to-side motion. Either poles driven in with "slip" joints that let the dock rise and fall, or cables connecting the end to shore (maybe crisscrossed under the gangway). The poles would probably work best for such a long dock.
I think you will need to anchor at pond edge, where gangway meets the dock, and end of dock furtherest in the water. In the water I used old tire filled with concrete, eye bolt in center, with chain crossed to oppsite side.
Concerte on ground may be Too big and start to sink that close to the water just due to weight. I think I would use post instead. Or just do the 8"x12" concrete beam with tpost.
Advantage to using a tire is you can roll on the dock to where you want it. I would not use a big truck tire. THe smaller 14" I used ended up about 180-200#
Last edited by BrianL; 03/15/1810:35 AM.
1.8 acre pond with CNBG, RES, HSB, and LMB Trophy Hunter feeder.
Thanks for the input guys! I am really trying to avoid poles in the water and I am not sure how well concrete anchors and cables or chains would work with my situation. My pond has about 3 foot of free board and it WILL use it eventually (I have too much watershed) and last winter was its first and it was dry, the pond went down about 1 foot. That's potentially 4 foot of travel that I need to account for in my anchoring system.
One thing to add, my little 1/4 acre pond is very well sheltered from wind so no constant wave action or side loading, just the occasional storm.
I am thinking about, similar to what Brian said, trying to dig two deep holes for sonotubes (or square forms) and attach the hinge plates to each concrete pillar. This should resist the side to side motion where a big chunk o' concrete might eventually shift back and forth and end up "walking" into the pond. The trick here is, how deep can I go before throwing in the towel? Only one way to find out, I plan to start digging this weekend if the weather allows.
At 31 feet long, that will be A LOT of torque, force, on those two hinges. Think about it as a 31' cheater bar, it won't take much force at the end of dock to start causing problems. I really think you will have to stabilze the other end some way.
Last edited by BrianL; 03/15/1812:42 PM.
1.8 acre pond with CNBG, RES, HSB, and LMB Trophy Hunter feeder.
I have seen 5 gal buckets of concrete with long eyebolts embedded and chains inside pvc up to the dock end used as anchors. Could also use coated wire rather than chain.
Maybe I'm just dense, but I can't seem to imagine how putting an anchor and chain/cable out in the water attached to the pond end of the dock allows for high and low tide (so to speak). If the chain is loose enough to allow for high water then it's not doing anything at normal level (it's too loose). If the chain is tight at normal level, the dock has to pick up the anchors or be submerged when the level rises to the emergency overflow and the anchors hold it down.
What am I missing here?
Now, I could attach to the corners of the first cross walk with chain or cable and anchor them to the bank at the same elevation as the hinge...this would allow for the dock to rise and fall but still resist the side to side forces. This option is a little unattractive to the eye, but would work.
I hope to convince myself that the hinge can be made stout enough to do this job by itself. It is made of 2-1/2" OD, 3/16" wall tubing and 1/4" plate and 1/4" angle iron. It's my ability to construct the concrete foundation that I'm fuzzy on.
I crossed chains under my gangway and added turnbuckles to tighten. My floating dock is shorter and wider than yours and still sways (need sea legs, but not so bad). I also added rails to the dock and gangway all around the chains to prevent anyone falling in over the chains. I don't think slides over pipes are attractive either, but I am not sure what other options you have. If your dock has plenty of flotation, maybe hanging submerged weight would slow the swaying, but I don't know. Maybe something like a keel perpendicular to the shore could work, but again, I have never seen it done.
If the objection is the aesthetics of the pipe/slide arrangement above the level of the dock, why not use telescoping poles with one end attached to the underside of the dock and the other embedded in the pond bottom, i.e. little pipe inside bigger pipe? There would still be a bit of sway as the difference in pipe sizes would need to be big enough to allow the dock to follow the pond level, but should be a whole bunch better than nothing.
Last edited by Bill D.; 03/15/1807:34 PM. Reason: clarification
Here's a pick of the shore hinge just for fun. It's going to be beefy enough I think. The gangway width is 4 feet for size reference. The holes in the hinge plate will easily except 3/4" anchor studs.
I have also thought about reconfiguring some of the dock pieces to allow me to get out past some submerged structure. The first cross piece would be right over some stump piles on the sides. The arrangement below would allow the dock to get inbetween them and get out into open water and yield a bigger platform.
I have red-marked in some cables that should give me the stability at the shore if it it needs it.
Please let us know how it works out. I think a number of us think that physics is working against your current plan, but everyone is wrong some of the time. You can always modify later if needed.
Here's a couple pics I found and saved for my own future reference. I think they show what others are trying to describe. To allow for changing water levels, the crossing anchors can be done with stretching/elastic ropes or inserts with cables. There are mooring springs that can be added to chains or cables too. Hope this helps
One thing to keep in mind is that arms, cables, and chains hooked to shore should be in the same plane as the gangway hinges so that water fluctuations do not tighten of loosen the stabilizers.
One thing to keep in mind is that arms, cables, and chains hooked to shore should be in the same plane as the gangway hinges so that water fluctuations do not tighten of loosen the stabilizers.
Very true RAH, I hear ya and thanks for participating!
I feel like I'm being pig-headed (which I'm known to be on occasion) so bare with me and know that I love each and every one of like a brother and a sister (Jimmy Buffet paraphrase).
I can see the good logic in the poles out in the water. I'm not sure how to do that now that the pond is full. My land is very rocky and it's too late to merely drive a pole in by hand. I'd hit a rock within a few inches and I'd be wasting my time. I thought about the garden hose water jet digging technique, but a rock is a rock.
Dam'd Waters, thanks for the pics. The submerged anchors work very well if the dock is allowed to float around some so that the chains have enough slack at normal level to allow for 3 foot of level increase. I need to keep my dock firm and stationary at normal levels, but still get the flexibility for higher water levels.
The stiff arms are going to be my fall back even if they are cables. This gives me the most hope, but adds two more holes to dig for concrete foundations.
I have run some calculations that use 75 mph winds blowing into the long edge of the dock. The resulting force on the dock is about 600 pounds at the mid way point. Transferring that force through the moment at the shore foundation yields a force on each sono-collumn of 2300 pounds. That sounds like alot, but I think two round or rectangular pillars (sono columns) that are sunk into the ground 3 to 4 feet have a good chance of resisting that kind of force. AND that's at 75 mph winds. At 50 mph winds the forces at the pillars drop to 1000 pounds. At 25 it's 500 pounds force. I think this will work so long as my hinge connections at the gangway and floater are good and solid.
Here's a visual for the shore foundation. The cylindrical portions would weigh 312 each and the rectangular step would weigh 840. It would all be rebar'd.
Not sure if standard auger pipes would work for you but they are designed for a full pond (search on "pole auger" and "dock post" at Menards website for examples). Even if nothing breaks, I expect the cables or chains will allow quite a bit of sway to the dock when folks are moving about near the end (based on my dock. I tend to try things my way first and gloat when it works or hang my head and fess up when it does not. My foray with a small blue catfish pond may end up the latter:) Good luck!
Pay close attention where and how you attach your bracket to the wood. To me, that is where problems will show first. If it fails it will be at the weakest point and metal bracket will be stronger than the 2x8. Might double up on the boards on the outside of gangway.
1.8 acre pond with CNBG, RES, HSB, and LMB Trophy Hunter feeder.
Good point Brian, it's not to late to beef that section up. I will be sandwiching the hinge angle iron on the outside with a backer plate on the inside. I will be working on it tonight. Maybe I'll get some pics of my progress over the weekend for the thread.
When I built my floating dock 3 or 4 years ago I had planned to anchor it to the bank with criss-crossed cables to add lateral stability. It is a 12x16 with a 4 x 16 gangway so it's not quite as long asy yours. After I got it in I was very impressed with the lateral stability without the cables, so I decided not to add them unless it was really necessary. I like pitching back under my dock since it's the only shade on the pond and the cables would be a hang-up liability. I watched it closely the first couple of years to ensure it wasn't a problem and it's as tight as the day I built it. We have had several near misses from hurricanes and on direct hit from a puny Cat-1. Just my experience but worth considering. Here is the URL to my photo server, you can back up one level to see the original build if you like.
I went with the exact stiff arm and cable system show in the photo. The only difference is my dock is a 30 foot covered pontoon boat. I used 20 ft sections of galvanized pipe and welded automotive tie rod ends on each end to give it some pivet room. I put turnbuckls on the 2 cables. Have had no problems with mine at all for several years now. If you wanted to beef up the galvanized pipe more, you could put rebar inside of it before welding the tierod ends on. Mine does not flex at all so I didn't use rebar. I screwed mobile home augers in the ground and attached the tie rods to them.
Dear Alcohol, We had a deal where you would make me funnier, smarter, and a better dancer... I saw the video... We need to talk.
The hinge turned out pretty good especially after a few coats of paint.
The shore anchor went well. The sono-columns ended up being only 2 feet deep because I dug down until I hit rocks too big for my manual post hole digger and my patience to deal with. The rectangular head was oversized to compensate. It turned out to be 18" by 18" by 59". Overall it used 1900 pounds of concrete.
The dock was preassembled in the shop so that I could minimize the figuring and building at/on the water. It has since been disassembled back to the individual four framed sections without the decking so that my little tractor could pick them up and struggle them to the pond.
The weather has not been cooperating enough to actually get to the pond due to the wet and cold conditions. It's a bit dangerous getting the tractor on the dam due to the mud, not to mention the fear of installing the tractor in the pond instead of the dock. Waiting for drier weather now.
Thanks for everyone's participation in this thread! You'all have given me plenty to think about and some reassurance.