Floating Docks

(part 2 of 3)

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The ice paradox: stability vs. chiropracty

Long, low, heavy, and wide. Okay, easy enough. I’ll build a floating dock the size of West Edmonton Mall. Unfortunately, for many cottagers – myself included – Mother Nature can throw a wrench into the works in the form of winter ice. It’s not the freeze-up that causes damage, or being locked in the ice for winter, so much as the spring melt, when moving packs of ice can grind docks into kindling. On many smaller cottage lakes, floating docks can stay put all year long. Others aren’t so forgiving. “The bigger the lake, the more problems you’re going to have with ice,” explains Greg Westwell of Fendock in Ottawa. “The ice will melt around the shoreline, but it’s the big body of ice in the middle that you’ve got to worry about. If it comes your way, there’s nothing that can stop it.” Similarly, any body of water that experiences strong currents will likely suffer an icy smash-up derby come spring. To avoid ice damage, many cottagers tow their floater to a sheltered cove or the protecting embrace of a marina. Or fork out for a steel-tube pontoon dock, which is virtually indestructible in almost all ice conditions. But for the rest of us, there are only two solutions: Haul the dock onto dry land each fall or purchase an agitator system that gets deployed each year to help keep your waterfront ice-free during the crucial spring break-up period

Actually, hauling out isn’t so bad. In fact, I’m convinced it’s extended the life of our dock by getting it out of the grips of the ice and letting it dry out each season. If you’re planning a new floating dock, it’s critical that you know whether or not it has to come out for the winter, because if you adhere -religiously to the long, low, heavy, and wide aphorism, no amount of beer and favours owed will ever get that sucker out come fall. But there are workarounds for the ice-afflicted. If you go with a traditional wood-framed dock, consider building in smaller sections that can be bolted together in spring, and taken apart for fall removal (still quite a chore, I might add). Keep in mind that each of these sections could still weigh in at more than 500 kg – but that’s much less than the total weight of the dock, and now removable with beer and called-in favours. A second solution is a modular approach, whether built or bought, where the decking, frame, and floats all disassemble for easy removal at summer’s end. A bit fussy perhaps, but your lumbar will love it. Another knock-down possibility is a dock system I call the “all-in-one” (see above) where floats, frame, and decking are combined in large polyethylene float units that are light enough to be easily lifted out for the season. It breaks the floating dock credo, the heavy and low part anyway, but it won’t break your back.

 

The shore connection

Perhaps the most important part of any floating dock, and one that’s often overlooked, is the link that gets you from dock to dry land, usually made up of a ramp and a super-secure shore connection. The ideal shoreline for this, of course, is gently sloping rock, which can be drilled to accept a ramp that attaches with solid steel pins or expansion bolts. For those not blessed with exposed -bedrock, the next best thing is a heavy-timbered crib filled with rocks, like a mini-deck that rises above the high-water mark. The crib can be backfilled or dug down and bolted to bedrock. Not only does it provide a solid place to attach the hinges for the shore end of the ramp, but cottagers can build to a height that compensates for steep shorelines and drastic changes in water levels. That way, you can make sure your ramp angle is as low as possible, never exceeding about 30°, unless you enjoy climbing up on your hands and knees. Another option, one that may affect the permits you need, “is to pour a concrete pad at the high-water mark, with a bracket attached to receive a hinge,” explains Hopper. “Just make sure the shore connection is above all the ice in spring and remember that the higher you go, the longer the ramp will need to be.”

The connections between shore, ramp, and dock – made with the aid of dedicated hardware – can help keep your floater where it’s supposed to be. Ideally, to best resist wind and waves, a ramp should be the same width as the dock it lands on.

In the real world, however, this poses definite problems, particularly when ramps need to be long to accommodate uneven shoreline or wildly fluctuating water levels that would make short ones too steep to clamber up. “The wider the ramp, the more stability it will provide,” explains Blower, whose wood-decked ramps hide a sturdy steel frame underneath. “But if you get too wide, weight becomes an issue. For example, if you have a 10-foot-wide ramp and you try to go out 16 feet, a steel- or even a wood-framed ramp is going to weigh a lot. At that point, you might just go down to a six-foot-wide ramp.” Many builders consider this a minimum comfortable width for a ramp; any smaller and two adults carrying groceries can’t pass each other easily.

But even at the six-foot mark, ramps can weigh a lot, creating two problems. The first is that even if you leave your dock locked in ice all winter, most ramps must be removed, so ice can push your dock around without yanking the ramp off its footings. That’s why many builders make ramps with detachable decking and lightweight aluminum frames. The other concern is that half the weight of
a massive ramp, plus the burden of the people walking on it, must be borne by the landward end of your dock which, if you haven’t planned for the extra load, will have a permanent squat and possibly sink a bit when walked on. The trick is to provide extra flotation, to either the dock or the ramp itself. At Dock in a Box, Doig adds extra flotation to the bottom of the ramp and, if the ramp is longer than six metres, a secondary float that hangs in the air partway along the ramp and only hits the water under a heavy load. “It’s like a staged suspension system on a motocross bike,” he explains. “The first part is very soft, but the more you push down, the more it pushes back. It makes a very comfortable descent.”

One robust variation is the roller ramp. Rather than being affixed to the dock with hinges, the ramp rests on top of the dock, sitting on rollers that ride in a channel fastened to the top of the decking. More common in large commercial applications, these ramps ride up and down with the dock and are often very long to maintain a low ramp angle even with extreme variations in water levels. Without a stiff connection to the dock, these ramps must be augmented with some other mechanism to firmly anchor the dock to land, such as cross-chains pinned on shore. In cottage country, you might find a roller ramp used with a steel pontoon dock or a heavy marina installation anchored by steel piles.

 

Anchor tenets

Getting solid anchors off the end of your floater is crucial. As wind and waves act on its long axis, the dock – and all the boats tied to it – becomes the arm of a massive lever that wants to separate your ramp from shore. Some professional builders use barges to position 1.5 to 3-tonne anchors, often to a total of twice the weight of the dock. Depending on lake conditions, other pros consider this overkill even though, once under water, a great deal of anchor weight is lost to buoyancy. The trick for home builders is to use a number of smaller anchors that are more easily managed on shore. Most cottage-country building centres sell pre-made 70-kg concrete anchors, barely manageable between two people, while Dock in a Box offers two-piece anchors, each half weighing 57 kg, that fit together before going to the bottom. “We recommend that cottagers pour their own anchors using Sonotubes,” says Hopper. “They come in varying diameters and it’s fairly easy to make a hefty weight that will actually roll down to the dock.” (For another anchor you can build, see Cottage Q&A, April/May 2005.)

In the simplest scenario, on a small, straight dock, you’d place two anchors out from the corners of the dock, with their connecting chains criss-crossing underneath. Leave the chains long to provide some sag, or “scope,” which will help them hang on in a blow. “We use a 1:4 ratio of water depth to chain length,” says Don Dailey of EZ Dock Ontario, based in Brigden. “So if the water is two metres deep, we’d want to see about eight metres of chain on that. You want to have the potential for some up and down movement.” Larger docks and letter shapes will require more anchors in different locations. And if prevailing winds are strong, a leading anchor, placed far over on the windward side, is necessary. Dailey also suggests using “angel weights,” 45-kg anchors that hang from each chain, about halfway up, so they don’t touch the bottom. “They keep your chain nice and snug,” he explains. “They also keep your dock from reacting quickly to waves.”

This anchor business may seem like a lot of work, let alone the building of a floating dock. But I can tell you from personal experience that it is as nothing compared with the wretched task of dismantling our overbuilt crib dock, where just about every above-water connection had to be attacked with an angle grinder to make it yield. Our modest floating dock, however, is a dainty addition to the shoreline, and performs all the functions the old dock used to. Best of all, come fall, it can be hauled out of the water with a block-and-tackle and some rollers. No sweat.

By the way. Is anyone interested in buying some used rocks? I don’t think we’ll be needing them anymore.

 

The traditional

This is probably the most common floating dock in cottage country, and the simplest. A wood subframe, usually pressure-treated 2 x 4s with 2 x 8s or 2 x 10s, will either enclose expanded polystyrene (EPS) billets or be bolted to polyethylene float drums. A second layer of subframe, of similar dimensions, will then sit on top, with the two connected by specialized corner brackets made from galvanized steel, or corner posts (4 x 4s or 6 x 6s), through-bolted with galvanized fasteners. Depending on dock size, cross-pieces with similar connections are added along the length of the frame. Decking (usually 2 x 6s) and a skid plate that protects the flotation during haul-out complete the job.

While not as high-tech as other designs, this style of dock can easily be home built, with lumber and parts that are readily available at building centres, or from kits that supply precut wood, hardware, and plans. For not-so-handy cottagers, there are many companies that design and build solid, traditional docks. “I can show you docks that are 18 to 20 years old and still doing fine,” says Harold Blower of Rose Point Contracting in Parry Sound, who has built more of these floaters than he can count. Blower uses Styrofoam-brand buoyancy billets, which he tops with wire mesh to protect from muskrats, and prefers a pressure-treated subframe crowned with western red cedar decking. For a typical dock, three by six metres, he charges about $2,600.

Blower builds in sections, then connects the sections to create the final dock, which is attached to shore with a steel- or aluminum-framed ramp (covered with wood decking) and anchored with criss-crossed chains to a pair of one- to three-tonne concrete anchors. “The further out from the dock you drop the anchors, the better,” Blower says. “It’s like a boat. If you drop the anchor straight down, it doesn’t do any good. But if you run it out on an angle, leaving some scope, it holds a lot better.”

 

The metal monster

The welded-steel pontoon dock is probably the toughest floater in cottage country. Neither big water nor bulldozing ice bothers these brutes, but they will take a chunk out of your wallet. The floats, fabricated from spiral-welded steel tube, are only limited in length by their ability to be moved. End caps are welded onto the tubes, creating an air-filled float. A steel superstructure then connects pontoons and provides support for wood decking, creating a dock that is literally bulletproof.

At The Ironworker, in Pointe au Baril, Scott Kemp constructs his steel docks using 60- and 75cmdiameter tube with walls four and six millimetres thick, and when the welding is done, he has a floater that weighs in at about three tonnes (for a 2.5 by 6 metre dock, the smallest he makes). “There are no other floating docks that are as stable, because of their mass and low centre of gravity,” says Kemp. “When you walk on a steel pontoon dock you think you’re walking on land.”

Pontoon sections can be bolted together to create letter shapes or even support a boathouse, and are held in place with several 1.5-tonne anchors and cross-chains attached to shore. Using aluminum tubing or truss -construction, Kemp can build ramps – complete with handrails – from five to nine metres long, a feat impossible with lumberyard materials.

According to Kemp, his docks can be left in all winter, except for a few that face severe ice movement and may need to be moved into a cove. “A fast flow of ice could possibly tear out some chains or move an anchor but it won’t damage the dock,” says Kemp, who figures a basic 2.5 by 6 metre dock with ramp, anchors, and installation costs about $10,000. “They’re the most expensive docks but they’re also the best,” he says. “You launch them and never touch them again.”

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Floating dock photo courtesy of Dockinabox