Features September 8, 2011

A Do-It-Yourself Winter Cover Frame

Above: The fully assembled conduit frame ready for covering took about four hours to construct the first time can be disassembled in about an hour and reassembled in two. Originally, the frame was built with additional pieces of conduit running fore and aft under the arches on each side The longitudinal proved unnecessary and were eliminated.

Why is it that folks who tuck their dogs into fancy hand-knit sweaters seem to be the same ones who leave their boats unprotected through northern winters? Snow, ice, air pollution, and sunlight, combined with alternating periods of freezing and thawing, can age a boat much faster in the winter months than in the more moderate climate of summer.

Perhaps the reason why many fiberglass boats are left uncovered is that their owners remember the problems of building a wooden frame over their wooden boats from years gone by. A complicated framework of 2x4 trusses and furring strips is as expensive and time-consuming to build as it is difficult to store for the summer.

There is an alternative to the wooden frame, however, and to the poor practice of using the mast for a ridgepole. A durable, lightweight and inexpensive framework of thin-walled steel electrical conduit can be easily assembled in less than a day. Best of all, it is reusable, easy to store, and can be built with only a hacksaw (or tubing cutter), a screwdriver, a tubing bender, and a wrench.

Conduit, also known as EMT (electrical-mechanical tubing), is readily available from building and home centers as well as electrical supply outlets. The frame for a 30- to 35-foot boat will take about twenty 10-foot lengths of 3/4-inch l conduit (about 7/8 inch OD),1 a 20- to 25-footer might require ten or twelve lengths of 1/2-inch conduit. In addition, you will need a few conduit connectors, a couple dozen hose clamps or gizmos called Kover Klamps, and a roll of duct tape. The total cost for the frame materials for a 30-footer runs about $100.

Two curved risers, attached to the bow pulpit and stern rail, support a fore-and-aft ridgepole made of straight lengths of tubing. The ridgepole is supported along its length by a series of arches, made from two lengths of tubing connected at the top. The arches attach to the lifeline stanchions, giving the frame a great deal rigidity. When laying out the arches, try to allow enough headroom to permit passage fore and aft on deck with the frame and cover in place. If the mast is left stepped (not recommended), run the ridgepole off-center to one side of the mast.

The photo above should help you to determine the proper dimensions and proportions for your boat. If you boat is larger than about 35 feet, or if anticipate a great deal of snow, you may want to add additional uprights between the deck and the ridgepole.

Plastic Tarpaulins

At one time, a custom-fitted canvas boat cover was a hallmark of the well found yacht. With the widespread growth of yachting came cheaper alternatives such as covers made from short ends of awning material or old sails. Next it was clear polyethylene-fragile, degradable in sunlight, and rarely tough enough to last through an entire winter.

Today, the best answer is one of the readily available covers of polyethylene reinforced with polypropylene. There are dozens of these covers on the market, some good and some not so good. Typically such covers run from about 6 or 7 cents up to 15 or 20 cents per square foot. In a somewhat higher price range, Griffolyn makes some rugged and well-finished tarps ranging in price from 10 to 40 cents per square foot, depending on the size and type. Price is not always a reliable guide to quality, but tarps marketed specifically as boat covers are generally better than the typical department-store and main order variety. The cheapest tarps will probably last a full season if well protected; the better ones should last for several years. If you are purchasing one of the better tarps through the mail, it would be wise to ask for a sample swatch before ordering.

The secret to a long life for a plastic cover is to stretch it tightly over the frame and around the hull. Polyethylene tarps can't stand much flapping and flogging and will quickly succumb to fatigue and abrasion. This may mean an occasional trip to a boatyard to routinely check the lashings. Also make sure that the cover is protected from sharp points and rough surfaces. Scrap carpeting or old towels taped to protrusions will help. Conduit is smooth enough not to need padding; it is the connectors, bolt heads and other sharp corners that do the damage.

When a cover begins showing signs of wear (thin spots where light shines through, for instance) it can be preserved with strips of good quality duct tape. Duct tape will stick well to a plastic cover-at least for one season-if it is rubbed on well.

Some companies have begun to market ventilators to be installed in their covers. In our experience, we find that a polyethylene cover gives plenty of ventilation without the work and cost of installing vents. Most plastic has pinhole-sized "vents" (or it will have after a few months use). And, of course, there is no need to ventilate the cover if you leave the boat underneath buttoned up tight as a drum.

This drawing shows the basic construction of a typical arch. The pitched-roof shape is easier to design and bend than a hemispherical shape. Note that two bends are needed, one just above the stanchions, and another at the top to accept the connection to the other half of the arch.

Start the construction of the arches by putting a smooth bend about two feet above one end of each piece of conduit. This photo shows tubing benders: one good bend (bottom), and a bad one (top). A kink severely weakens the conduit, so make the bends carefully and try not to make them too tight.

Attach the upright members of the conduit frame to the stanchions with hose clamps.

Six or seven feet between stanchions is too much unsupported span to withstand heavy snow loading, so intermediate arches run to lengths of 2x3.

U-bolts are used to attach the 2x3s to the stanchions, and the arches to the 2x3s.

The secret to preserving the cover is to lash it tightly under the boat so it cannot flood. There should be no pockets where water can collect.

Comments (6)

I made a lightweight version, which withstood southern Ontario lakeside snow loads, out of plastic 3/4 inch electrical conduit and nylon pull ties. I found it necessary to use 5 hoops across boat and 6 vertical lines of conduit running fore to aft. Mine was 6.5 feet high at the arch top, so I could work on the boat over winter. An advantage of conduit is that you do not need a pipe bender or some of the heavy U-bolts, etc.

Posted by: Randall W | November 30, 2013 8:15 AM    Report this comment

Another option: Our 30' sailboat winters moored at our Chesapeake Bay house, mostly covered with a 20' long tarp over the lowered boom (since 2009). The heavy white tarp (best we found on eBay)costs

Posted by: John R | November 13, 2012 2:10 PM    Report this comment

There are several issues with the type of cover described here:
1) the plastic tarp will rub the topsides and mar the finish, no matter how tight you make it the small movements induced by wind will take their toll over the winter season.
2) any sags in the tarp will create a pocket that will grow with rain, snow and ice accumulating. These will become quite heavy and potentially destructive very quickly so the cover must be checked weekly and any pockets dumped out.
3) grommets in plastic tarps should not contact the hull, again they will mar. Many grommets aren't strong enough and might pull out. Make sure you use heavy duty tarps. Cheap ones won't stand up to even one season of fierce winter winds.

In the end, a well constructed fitted cover made of TopGun or heavy sunbrella or other suitable canvas is a good investment if you plan to own your boat more than 5 years. Been there, didn't want to spend the money for one, but now glad I did.

Posted by: LDH | November 4, 2012 5:18 AM    Report this comment

I built a pvc frame for my 22' sailboat. Easy/Inexpensive/worked great!

Posted by: Neil K | October 3, 2012 10:24 AM    Report this comment

It occurs to me that you could also eliminate the inflexibility and some u-bolts, as well as the bulk of the 2X3's, by utilizing 4 way conduit connectors to allow for horizontal runs of conduit between the stations.

This also allows the plastic to rest directly against more conduit surface, instead of leaving an (admittedly), small gap because the 2X3's are bolted inboard of the stations.

Lastly, using conduit for the horizontal runs would allow you to bend it to follow the shape of the boat.

Posted by: John H | September 9, 2011 7:02 PM    Report this comment

Is there some reason metal conduit is used instead of schedule 40? The plastic conduit would not rquire bending

Posted by: KENT K | September 9, 2011 6:54 AM    Report this comment

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