By Keith J. Lindholm
If you are in the market for a teak dorade box and a stainless steel cowl vent, there are numerous possible combinations to choose from. I found it very useful, when trying to determine which would be the box/vent most appropriate for my boat, to make a cardboard model prior to placing my order.
Having gone to one of the websites that sells such equipment, I took the measurements provided for the dorade box I was considering, traced the dimensions out on stiff cardboard, cut the (five) pieces out with a utility knife, and taped them all together to make my temporary dorade. I did the same thing with the cowl vent I was selecting and taped it (using a wooded stick for support) on top of the box to complete the combination of the two.
The cardboard prop insures that you purchase the correct combination for your boat that will be the most functional, proportionate in size, and aesthetically appealing since the dorades/cowl vents add to the beauty of you vessel. The prop also allows you to move it around on the deck and will aid in your final location for installation.
Since I own an Island Packet 31 and could find no other with dorades/cowl vents installed, making a prop was the only option before I was going to spend nearly $600 dollars. For my application, I used the Monterey dorade box with the three-inch low profile cowl vent, along with the low-profile three-inch mushroom vent inside.
Once you have made your selection, read through the entire instructions first, while making notes of the items you will need, and then follow these detailed step-by-step instructions. This will make the installation process a breeze:
1. Take your dorade box, place it on top of a thin piece of cardboard, trace out the bottom for your pattern, and cut it out with scissors. Using a tape measurer, find the center of the pre-cut hole in the dorade box and mark the location on the cardboard template.
Then take whatever size plastic pipe liner you have for the interior, turn it upside down (lip faces up), and trace the outside diameter directly in the middle of the cardboard pattern with the previous mark centered. This insures that both the dorade and the mushroom vent are lined up correctly and centered accordingly.
2. Now that you have your template in hand, place it on top of the cabin where you are going to install the dorades (similar to what you did with the cardboard dorade), both port and starboard, and with the projected height of the combination of the two in mind, take a good look at all your spars, rigging, lines, sheets, boom vangs, winches etc., and make sure that the installation will not interfere with anything on deck.
Make visual references, or measurements if necessary, of hatch, winch, and rope clutch locations on deck and then go below and make sure that you are drilling into a clear cabin roof area and not too close to an interior grab rail or any other interior bulkhead or hardware.
3. As you recall, you traced the outside diameter of the plastic pipe liner (Step 1) in the center of the template, directly in line with the pre-cut dorade hole, and you need to mark the exact center (again, a repeat of Step 1) of that circle that represents the size of the hole saw that will be needed according to your purchase.
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| "Make visual references, or measurements of hatch, winch, and rope clutch locations on deck and then go below to ensure you're drilling into a clear cabin roof area." |
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With your center marked and the template in the exact installation spot , take a 3/32 or 1/16 drill bit and drill a hole through the center mark of the circle and completely through the cabin top. Repeat this process on both sides and always hold your drill at the approximate angle of the deck (known as “deck camber”) when drilling holes.
Important: Once you have both small holes drilled on port and starboard, go down below once again and confirm that there is sufficient room for the 3 ¼ or larger diameter hole that is about to be made in the next step according to your pipe liner size.
4. Now, once you are satisfied that your installation location is fine from down below, take some masking tape and a regular plastic trash bag and tape the opening edge of the bag to the ceiling of the cabin to catch all the dust and debris.
Make sure the small pilot hole you drilled is in the center and shape the bag with your hands so it hangs freely. Next, measure the outside diameter of the deck pipe liner, the circle you already have traced out on your template, and this will be the size of the hole saw you will need. (In my case, using the three-inch pipe liner, I used a three-and-one-quarter-inch hole saw and the liner fit too snug. I then used a rasp file and removed just enough material for a perfect tight fit.)
Back on deck, drill the first hole (remember: hold the drill on the same angle as the deck camber) where your trash bag is secured down below and then vacuum up the area and clean out the hole with a damp rag to remove the dust.
With your plastic pipe liner in hand, go back down below, remove just a small portion of the trash bag, and see how the liner fits up into the hole. If it goes all the way in up to the flange, fine—the hole saw size was perfect; if not, then put the bag back in place and work a half round rasp file around the hole from outside until it does. You’ll probably make several trips down and back during the fitting process. Once you have a good fit, follow the exact same steps on the other side.
5. At this point, you should have both holes drilled through the deck, the outside mess vacuumed up, and the trash bags gently removed and thrown away. Now wipe both holes clean with denatured alcohol to remove any dust since you will be sealing the edges around the holes with epoxy or 3M 5200 sealant. (I chose to use epoxy because after I cut my holes in the deck, there were small voids around the edges and I wanted to be certain the edges of the holes were completely sealed to avoid any water saturation into the deck coring over time. 3M 5200 sealant can also be used, however it is difficult to get smooth and doesn’t sand very well.)
Before mixing your epoxy, go back down below and tape a piece of plastic loosely to the cabin top under both holes. Now, mix your epoxy (any two-part brand will do and you only need a small amount) and spread it around the inside of your cutouts making sure you completely fill in any voids (holes) in the coring.
I used a latex glove and my finger to spread the
thin coat of epoxy and it worked great to get a nice even coating around the holes. Once the two holes are sealed, wipe off any excess material that may have gotten on the deck, cover both holes with a small piece of plastic, and tape it down to the deck. Then, remove the plastic down below and cleanup any excess material around the bottom edge as well. Let the epoxy cure overnight and proceed to the next step.
Editor's Note: Next month, Keith will continue describing his step-by-step dorade installation instructions. Stay tuned!
About the author: Keith J. Lindholm has been sailing for nearly 30 years in and around Biscayne Bay, FL, where he now spends his leisure time aboard his 1988 Island Packet 31 True Love. He is a third generation carpenter and besides sailing, working on boats is his second passion.
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