It always surprises me to see how quickly the weather patterns change from summer to fall up here. 18+ hours of daylight at the Summer Solstice is now about 10 hours, and we’re losing daylight at the rate of about 5 minutes per day. Strong weather fronts start coming in off the Gulf of Alaska, and it’s not the nicest time to be out on the water if you don’t have to. The good news? It’s now dark enough to see the aurora borealis on a clear night, and when the aurora activity is far enough south. The aurora wasn’t too bright this particular evening but it was still pretty to see, with Ursa Major (the Big Dipper) and the north star – the symbols on Alaska’s flag – just above the green light.
The end of the summer cruising season gave us a chance to make a change to ADVENTURES – something we’ve been considering for a long time: a bulbous bow. Without going into lots of technical detail, suffice it to say that a bulbous bow is a rounded protrusion under the water that helps break waves and improves efficiency. It doesn’t look like it would do all that, but it does very effectively.
DeFever-designed boats perform very well in the ocean, though they are known to “hobby horse” when waves are directly on the bow – we get a lively ride in a head sea. We’ve been interested in a bulbous bow to help dampen that motion, more than to improve speed or fuel economy but we never though we’d find someone with the knowledge and experience to scale a bulbous bow for a boat of our size… until we met Steve Keller in Wrangell. We asked our commercial fishermen friends and they all spoke highly of bulbous bows and of Steve’s work. Jim did his own deep dive into the science and math of bulbous bows, comparing his findings with Steve’s recommendations. Everything matched up, so we decided to take the plunge.
Here are a few photos of the process and the final result – spare us the snarky comments about what it looks like. Boats are known as “she”, and… we like to think of ourselves as more “transgender” now.
We started out with a 10′ long, 3′ diameter fiberglass cylinder 3/4″ thick and weighing 700 lbs. There was a LOT of leveling, measuring, marking, re-measuring, test cutting, and more re-measuring before the final cuts were made to make the cylinder fit snugly to the curved sides of ADVENTURES’ bow.In the photo above, the 10′ long cylinder is still 10′ long… but most of that length is on either side of the bow, and only a couple of feet extend beyond the bow at the top.
A large ball buoy was inflated to fit the end of the cylinder, and used to mold the dome.I’m skipping over a lot of intermediate steps, but here’s the cylinder and dome mated together and fiberglassed to our hull.The overall weight of this addition is over 900 lbs, carefully calculated by weighing the original cylinder, weighing the big pieces cut out of it, and keeping track of the yards of fiberglass cloth and gallons of resin used to construct everything. It’s important that the finished bulb doesn’t make the boat ride lower at the bow – instead we want it to be neutrally buoyant or very slightly positively buoyant. There is a lot of math that goes into scaling and balancing a bulbous bow like this, on top of the skill to construct it.
Our bulb has both air and water chambers to achieve the proper buoyancy. Steve constructed a bulkhead inside the bulb to trap enough air in the aft section to offset the weight of the fiberglass as well as the weight of the water that will be carried in the front section. The dome end of the bulb has two 2″ holes drilled in it (top and bottom) to allow water in it so it’s not too buoyant. This really was a fascinating project.
This is the final result, after sanding and fairing, epoxy barrier coating, and bottom painting. The native style eagle head was Jim’s idea – he drew it, created a large-scale stencil for it, and painted it on each side of the bulb with black bottom paint. Pretty spiffy!The whole process took about 10 days, and living in a boat yard shed with all the grinding and sanding dust was not fun, but the guys were great to work with and the project was a good intellectual challenge. We’re very pleased with the result.
Now we just need lots of sea time with the new bulbous bow to see how the boat’s ride will change. We cruised the 40 miles back to Petersburg, and it was the one time we were disappointed in having flat calm water! The biggest wave we could find was a ferry wake, so we’ll have to wait until the cruising season starts in the spring to really give the new bulb a thorough workout. We definitely saw a big speed improvement, and felt some differences in the ride. Docking is a little different now – with the extension up front the boat doesn’t want to make sharp 90 degree turns the same as before, so it will take some practice to see how much more rudder to use and where to line up. We’re really looking forward to the boating season starting up again in the spring, especially now that we have a new “toy” to experiment with, and an improvement in ride when the sea is on our nose (as often happens in the long channels that funnel the wind up here).