The Cutting Edge, Part II: It's Time to Build a Dodger
By John LeMole
Editor's note: In the last issue LeMole introduced the drop-top dodger design. In this installment, he reveals, step by step, how to build the dodger. (Sorry, no photos are available to accompany this article.)
Just as no one pill can cure every ill, no single dodger design sign can suit every boat. However, the drop-top-style dodger, which is distinguished by a removable top and a semi-permanent windshield, was created to address many of the traditional dodger's limitations. The drop-top enables boat owners to remove the dodger top without removing the windshield, which spares the window vinyl from suffering; unnecessary wear and tear. It also offers better visibility and easy access to the companionway and side decks. So, now that we've discussed the drop-top's design qualities, let's head for the shop.
As Photo 1 illustrates, the drop-top's frame orientation is the opposite of that of a traditional dodger, which means the forward frame mounts to the cabin house and the aft frame is secured to the forward frame.
Photo 1. The drop-top's forward frame mounts to the cabin house, while the aft frame is secured to the forward frame.
Since the windshield stands alone, you need to give special emphasis to its shape. So, it makes sense to design the windshield first, adding such appearance-improving touches as extra crown, larger radiused corners or perhaps some slope in the slides. Remember, the drop-top look is intended to be distinctive, so devote some extra time to creating an attractive profile.
Before you start designing the frame, however, it's important to address one key issue: When the aft frame is folded forward, how high is it in relation to the forward frame? Due to the hardware, there will necessarily be a space of 5 inches between the folded frames, but that gap hardly will be noticed if the aft frame doesn't stick up higher than the front. Depending on proportions, this arrangement may not always be possible, but it should be the goal.
One last frame design point to consider: Traditional dodger frames usually are set at the extreme aft end of the cabin house. Drop-tops however, should be mounted roughly 3 to 6 inches forward of the end of the cabin house. That way, the line of the aft edge of the windshield can be attached to the cabin house for proper tensioning and a clean line.
Photo 2. The forward struts keep the windshield tensioned, independent of the top. The aft struts are hinged, enabling the aft frame to be folded forward.
Now let's move on to the struts. The drop-top frame is supported by four struts: one pair forward from the deck up to the forward frame, and the other pair connecting the two frames. The pair between the frames tensions the dodger's roof, and is hinged so the aft frame can be folded forward. (I'll explain hinge design sign and installation a little later on.) The forward pair keeps the windshield tensioned, independent of the top. (See Photo 2.)
Your forward struts can he constructed one of two ways: folding or fixed. If, for instance, your customer wants Polycarbonate for the windows, the windshield won't be folded down and you can opt for fixed struts, which then can be placed on each side of the hatch box, using concave rail bases on the upper ends with quick-release pins.
You also can, if you wish, incorporate folding forward struts in your design. In this case, they will be mounted on the sides of the frame and attached with a jaw slide. Note: These struts will require locking sleeves to secure the joints, a topic I'll address shortly.
Now then, the key to working with folding struts is recognizing the fact that the hinge almost never is placed in the center of the strut. A dodger or bimini frame, for example, has a horizontal tensioning strut that pushes the two frames apart, keeping the cloth taut. Unless the triangle formed by the two frames and the strut is a perfect isosceles, the distances A and B will he different.
So, when the frame is folded, one end of the strut will be higher than the other, which means the hinge will need to be situated off center. If you don't account count for this height difference in your design, the frame won't fold down compactly and it will be more difficult to store (See Photos 3 and 4.)
Photo 3. When dealing with folding struts, the joint almost never is centered in the strut.
Photo 4. By situating the strut's hinge off center, the height difference between the folded frames will barely be noticeable.
Designing the hinges
Now, let's design the hinges for the struts. To do so, you'll need the following dimensions:
- the length of the strut, and
- the height difference between eye ends when the frame is folded.
Once you've got those dimensions, assemble all your frame components in their proper locations, substituting solid sections of tubing for the struts. Then, when you're pleased with the frame, remove the tubing from the strut spaces (I leave the eye ends attached to the jaw slides) and fold the aft frame against the forward one, keeping all eye ends pointing upward, as they will be when the folding strut is in place. Measure the length of the strut tubing, end to end. Next, measure the height difference between the two eye ends. (Note: Measure each side of the boat separately in case they are not identical.)
Let me offer an example of the process I just described: Say the strut is 10 inches long and the height difference is 2 inches. We can conclude that the hinge will need to be 2 inches off center, a 6 to 4 inch split.
Now, use those dimensions to create a pattern that you'll use as a template for the struts. Cut a strip of paper or pattern material 10 inches long (the length of the strut). Then, fold the paper so that one edge is 2 inches from the other; that accounts for the 2 inch off-set. Mark the fold's location, which will note the exact location of the center of the hinge when it's installed in the tubing.
The drop top look is intended to be distinctive, so devote some extra time to creating an attractive profile.
But wait don't cut the tubing just yet. First you must make an allowance for the hinge, which, when installed between the strut's two sections of tubing, lengthens the strut by -inch To compensate for the added hinge girth, subtract 3/8- inch from both ends of the strut.
Now you can cut the tubing pieces, which, according to our revised measurements, should be 3 5/8-inches and 5 5/8 inches long.
If you prefer to avoid numbers, there's another way to pattern the struts: Simply cut the strut pieces long, install the hinge (which I'll discuss next), lay the strut on the paper pattern with the center of the hinge on the fold mark. Mark the tubing at each end of the paper, and this will give you the finished strut length.
Installing the hinges
The hinge I devised for this application is composed of two hard plastic plugs connected by a flat linking piece, which are inserted into the ends of the strut tubes. What's more, to stabilize these hinges, I recommend using an outer stainless-steel sleeve, which locks in place using pressure balls. Here's how you install the strut.
- Clean the burrs from inside the tubing ends using a round file or rotary rasp.
- Drill and tap holes 3/4 inch from the end of the tube for setscrews. Use a #3 or 5/32-inch drill and a 1/4-inchtap. Also, use cobalt bits and cutting fluid.
- Place the spring balls (I use style #SS 132 from John Boyle & Co Inc., Statesville, NC.), which are positioned on either end of the 5~inch sleeve. Drill a hole (9/32- inches) for each spring ball 2 5/14- inches from theends of the tubes, making sure to place the holes in line with the set screws.
- Install the spring balls then insert the hinge into the tubing, aligning the hole in the hinge with the tapped hole in the tubing. Finally, install the se set screws.
Now for the fabric work: Pattern your drop-top windshield, top and wings as you would for any other dodger, keeping in mind that the drop-top windshield required quires a zippered pocket so it can be tensioned independent of the top. (Even though I don't like affixing a hook~and loop fabric flap to frames, this is a good application for that method.)
Be sure to mark on the pattern where hardware will interrupt the pockets. If you're planning to mount the forward struts near the hatch, you might want to design your cloth breaks in the windows so that they conceal the hardware (See Photo 5). A windshield divided in thirds is attractive, and it enables the boat owner to fold the windshield without creasing the window vinyl or Polycarbonate.
Photo 5. Place your windshield cloth breaks strategically so they conceal the frame's hardware.
One last point about pattering: I recommend pattering these tops with plastic instead of cloth blanks. Why?
You'll cut down on your patterning time if you use plastic and double-stick tape, and it's easier to work with when you're patterning in the shop. Let's go to construction and you will see what I mean.
Before cutting any cloth, I bring my patterns to the layout table and make certain that all the pieces are in agreement; that is, all marks line up and everything makes sense on both the port and starboard sides. In particular, I examine the area where the top, wings and windshield come together. I also draw in final window lines; the locations of zipper pocket terminations and finished lower edges (especially at the wings).
The drop top style calls for a zippered flap to be sewn to the windshield. Note that this flap runs the entire length of the forward frame.
How do you create this flap?
Temporarily attach the wing patterns to the top pattern (double stick tape works well), which gives you the complete top/wing assembly, as it will be built. Then, simply draw a line 2 1/2 inches from your forward frame marks, demarcating the flap location. You also need to add marks where the zippers start, and how far into the flap the you plan to place the zipper, along with any strike-up/hash marks you think will help you control the design's alignment.
If the dodger's shape allows for it, you actually could cut the top and wings from one piece of cloth and avoid creating a seam. If the wings need to be made of separate pieces, however, you eventually will have to remove the wing patterns from the top. But draw the flap before doing so.
Now it's time to transfer your marks from the patterns to the cloth. I do not fair any lines until they all are on the cloth. After fairing the lines, I cut out the pieces and heat-seal all their edges. Then I install the fastener reinforcement to the lower edge of the windshield.
Next I sew the binding on and install the windows. If you're building a three-panel windshield, cut the cloth along the vertical breaks and install the three window pieces separately; this way, they're much easier to handle. After the window sections are in, reinforce them with cloth strips inside and out. Install the zippered frame pockets, and insert the zippers and binding.
Now, go ahead and sew the zipper flap to the windshield. I generally use two zippers, both starting at the middle, but practically any arrangement will work.
Since dodger roofs often incline forward, care must be taken to create a zipper joint that will not leak. I've successfully used the following method:
- On the flap, sew the zipper to the bottom surface and inset it forward of the aft edge 3/4-inch.
- On the roof/top panel, sew the zipper to the bottom face, inset aft from the forward edge 1/4- inch. This will creat a baffle over the zipper teeth.
If you need to create a more complete seal, sew a small beading gasket to the roof's top forward edge, so that it sits between the flap and the top. After the flap is assembled, sew it to the windshield section.
Assembling the top is a fairly routine procedure. Make the aft frame pocket and external chafe patch as you would for any other dodger. Attach the side wings and then sew on the forward zippers and binding. A snap at each end of the flap secures the opening and gives a neat finish.
Now that your drop-top dodger is assembled you'll notice that you easily could install large windows that cross the wing-seam area. With a little window-design creativity, you can maximize user visibility without minimizing the dodger's user friendliness. Remember, even with windows throughout, the dodger still will fold neatly for storage since the windshield and top store separately.
An award-winning marine fabricator, John LeMole is owner of Gemini Marine Canvas, Rockland, Maine.
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