for a bridge. spans i would say 40 to 60 feet. 4 fee wide. only 4 4" galvanized metal pipes / posts. and i want to say 2x12's are used as the under side supports, with regular decking board on top.
i was way to young to remember post being put in. but i want to say they took a piece of 2x6 and placed over top of pipe, and used a 2 to 3lb hammer. and slowly tapped the posts down. while standing in the boat.
i really hate this bridge. when the water gets low. IT GETS LOW, 4 to 6 feet low. when lake is full of water and going out the overflow pipe. water is about 2 to 3 inches below the 2x12s. so you end up with 5 to 6 feet drop and no easy way to get in and out of a boat. when the water is down that low.
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year or 2 ago. i had some 55 gallon drums laying around. some old plywood, and some ugly 2x8's laying around. so bought a couple boxes of screws and built raft / dock. i put about 10 gallons of water and some antifreeze in each drum. for little extra weight in bottom of drums. and added a 2x4 ladder, that hinges right at the water line. so lower half of ladder can be pulled up out of the water and tied off with a rope when no one is around.
it will stay on the lake forever. well at least until it is about to sink or completely fall apart.
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hopefully later this year, i have some 5" x 9" x 16 feet long pieces of lumber 3 of them. and a bunch of hard board insulation. and will be building another dock. that sets much closer to the water level. to a point were i can actually set down on dock with a couple folks and still keep our butts dry, but have just below knees all the way under water. there are a good amount of DIY builds on the internet and most likely some here on this forum for hard board insulation/Styrofoam docks.
i may end up skipping the stryofaom for this dock. and use 2 to 4 55 gallon drums at one end, and placing other end up on the bank. and tieing it off, so i have a way to tie off the 55gallon raft/dock and tie off the row boat. perhaps diving if i place it in certain area. i may end up driving two 4" or so metal pipes down for posts. and for giggles. once drove down and cut to height. get some bags of concrete and dump down the pipe. all the way up to the top.
i doubt i will even attempt to use wooden posts. way to heavy for me to try and jack around with. and no real way to get a tractor near spot i would want the posts. and a pipe should be easier to pound down into mud granted i will most likely need to have a longer metal post vs wood post.
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thinking about it. i may build the floating dock and just tie it up with ropes, and wait till winter and good thick ice on lake. and rent a 2 man post hole digger with extensions. and dig me some holes through ice and right on down into the mud.
i suppose if you had 2 row boats. and 4 people, 1 in each boat to keep boats were they need to be, and another in each boat working on putting post in. (1 holding other using a small sledge hammer 2 to 5 lbs) and slowly tapping down a wooden post that had a point on the end.
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another thing for "water level when low" mom's house there was a concrete 3 feet wide or so 6 to 8 feet long dock. that you could go diving off of. when water level was low, 3 to 6 feet, it was a pain in rear to get up and out of the water, from regular pool ladders, to extension ladders, to ladders that fold out into an A. to other,
floating docks, i have come to love. and makes life easier getting in and out of the water. and i am loving the 2x4 ladder that hinges right at water level. it looks like an extension ladder. but a little bit wider. and ran the 2x4's about 5 feet up into the air. and then ran 2x4 angle brace further back on the dock. allow folks to either step around and onto the side of dock when getting out of the water. or through the middle. with the hinge, and nylon rope able to pull ladder out of water to keep it from rotting on me and **more so** keep algae and junk from growing on it and making it slick. the lower portion of ladder does want to float up on me some. but it is fairly easy to put a tiny bit of weight on ladder and it sinks, and allows you to climb right up and out.
