Dock broke - question about aluminum trusses or other aluminum DIY solutions

[Pricestavern]

Originally Posted by 8gv

While this system looks very easy to assemble, what about the length of the legs going into the ever deepening water?

That's a good point. Plus, I'd be concerned about the effect of my boat bouncing around against it during rough weather. The dock shown looks like pretty light construction. I'd worry that it would get bent or kinked with the boat shoving it around. I don't think dock whips would be usable with this system, either. Be nice on a pond or slow moving river, though.

[DickR]

Originally Posted by Pricestavern

.... Plus, I'd be concerned about the effect of my boat bouncing around against it during rough weather. The dock shown looks like pretty light construction. I'd worry that it would get bent or kinked with the boat shoving it around. I don't think dock whips would be usable with this system, either.....

That dock in the video did seem a bit lightweight, but then a lot of rigidity is achieved with L-sections or a wider dock. As I mentioned, my 6x30 crankup is quite torsionally rigid, being anchored solidly at the shore, and I do have whip mounting plates welded onto the frame; the whips bolt through the deck sections to those plates, and they don't move at all. The boat pitches substantially when a big boat wake crashes ashore, and the whips take all the action, while the dock stays put.

As for ease of installation, I turn the winch handle and the frame sets gently down to the bottom. I carry each cedar deck section, 6 by just under 4, out to the frame and set it in place; a section weight is mid-upper 50s (lb), an easy one-man move. When I get decking laid out to where the lift cable attaches, I detach that and wind it back onto the winch reel for the summer, then drop the last two deck sections on. I have to lay down on the dock surface to reach under with a wrench when I bolt the whip bases in place, but that's easy.

For removal, the process is just reversed. It's handy to have a magnet attached to a string for retrieval of nuts and washers that leap out of my hands into the water under the whip plates. Doing this on a cold November day seems to make the small parts jump around a lot more actively. After the cable is reattached and the rest of the deck sections carted away, the winch hauls the "lifting ladder" up easily to perhaps 30 degrees above horizontal, at which point the "Y" cable from its end down to the dock frame goes tight. Then the cranking gets harder as the heavy frame comes up out of the water, to a point where the closest dock legs will stay comfortably above where the ice will be. The whole process is a lot easier now, compared to the ordeal of wrestling water-logged wood frames up over the embankment each fall.

As TiltonBB said, you can build your own deck sections yourself and save some labor cost. I did that for mine, using cedar for its light weight and natural rot resistance. I did a quick calculation on weight of other choices, and I found that pressure treated wood or composite decking would have nearly doubled the weight of each section.

[Pricestavern]

DickR - what is the frame of your crank-up made of? I too have a crank-up (20') but the frame is made of a single, welded aluminum box girder-like structure. The one shown in the video is sectional. I think that would make a difference in its rigidity, no?

[DickR]

The dock frame is welded aluminum. The top chord is 2x4 all around. Perhaps 16-18" below that is a 2x2 chord. The two are connected vertically with pairs of 2x2 pieces on each side, where the legs go. There are four pairs of 4x6 PT wood legs out over the 30 length, or a bit short of eight feet apart. The pairs of vertical 2x2 pieces have a small gap between them, and the bolts holding the legs strapped to the frame pass between the pair. A piece of peel & stick rubber roofing membrane keeps the PT wood separated from the aluminum.

Across the 6' width are 2x2 cross members, except 2x4 at the two ends. There also is 2x2 cross-bracing. The lifting ladder is rectangular, made of 2x4 sides and 2x2 "rungs." This is 24 ft long. It sets down over the lateral members and cross-bracing and, with the two sides of the dock, helps support the deck sections.

In the first pic, you can see the two whip mounting plates, one near the outer corner, the other 10' in. The second pic shows the frame mounted on the header bar assembly, which was welded up in place for the set of boulders at the shore. In that second pic, that's not the lake bottom under the header bar. It's a lot of rock debris from drilling into the boulders for the expansion bolts and from chiseling out a place at the top of one boulder to make room for the header bar. The ice was well over a foot below that dirt, right down to the lake bottom.

[sluggo]

Dick You didn't mention that we cut and lap all of our joints before the process of the mig and tig welding and we also cross brace and gusset the joints so the dock can handle pretty much anything you put on it ! Thanks for posting your pics its great to see are dock work from Center Harbor Dock and Pier on the forum....

[sluggo]

quality of the welds when finished ....

[sluggo]

This is a crank up we built this year to replace an old wooden seasonal to add in a finished product to the thread.

[TiltonBB]

The longer dock is 47 feet and required a boom to lift it. The boom collapses for summer and is stored underneath the decking.

The wider dock was actually two separate pieces that were bolted together permanently after they were placed in the water.

When the dock is raised for the winter make sure you attach lines to the shore from the outer end. The lines are to prevent the dock from swinging side to side when it is windy. That will break welds or otherwise put a lot of stress on the dock.

After a lot of years of lifting the decking, recently I have been using a hand truck (two wheeler) to remove and replace the decking. It sure beats carrying them!



k.