Rushton Pulling Boat Build
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John,
Again, a 'Thank You' for letting me demo your boat at the mess-about. I liked its speed enough that I bought a set of plans and would like to borrow your molds when I do get ready to start building. Aside: The plans are far less complete than what I was expecting to see. That fact that you built from them is a tribute to your skill. If you're coming to the Open House this Sat, I'll bring oars, and we can get you started on building a set. Charlie |
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Wow, that's great that you are going to build one! Of course you
can use the molds, just let me know when you need them. I also have a strongback that I built for this project that you can use. It will make the mold setup easy, since the mold form locations already have screw holes. It's a bit bulky, being almost 14' long, but it should be transportable on a roof rack. About the oars, I couldn't wait, and have already started them. I'll bring what I've completed so far to the open house on Saturday. John On 2017-06-01 09:39 AM, Charlie03 [via
RiversWest Forums] wrote:
John, |
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John,
I liked the way it rowed. And for our local, choppy waters, it's a better hull than the flat bottoms I typically build. I've never done SOF, and that is going to scare me. But I want a faster boat. I see in the plans that the molds are made from 1/4" ply. Is that what you used and not 1/2" (which would be my choice for greater rigidity)? Are the fore and aft thwarts structural, or could they be eliminated? Yes, do bring what you've done on the oars so far. Charlie |
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I used 1/2" OSB for the molds and strongback, and reinforced them in places with 2x4 lumber. On my boat the fore and aft thwarts are not structural, but I beefed up the gunwales beyond what the plans call for. They may be needed for rigidity if you build the gunwales to plan. I would think that in that case they could be replaced by a couple of simple gunwale thwarts. (As opposed to rowing thwarts) Also, in the plan bill of materials there is a small error; you need 10 stringers, not 6. John On 2017-06-01 02:41 PM, Charlie03 [via
RiversWest Forums] wrote:
John, |
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John,
You made exactly the same choices I would have with the thwarts and gunnels, especially since I'll never be putting a second person in the boat. Give me a few days to look at the plans and to set up where I'll do the building, which will have to happen on my deck and need a stretch of dry weather, then I'll be wanting to borrow the molds and strong-back. For your oars, what blade thickness did you decide on? There no need to be any thinner than 3/8", given that the purpose of an oar is to grab water, not slice through it. Which woods you build the oars with doesn't much matter. But fence-board cedar is cheap, light, and easy to shape into blades and lower looms. For the upper loom and grip, red oar is cheap, strong, and offers the weight needed. But anything can be made to work, even poplar, which is cheap. If you don't have a gram scale and don't want to do the math, then putting the balance point at 4" to 4-1/4" from the pivot point of the oar will give it a light feel, and that can achieved by trial and error. What's likely to give you the most grief is shaping the grip, especially if you're shaping it by hand. If you can, use epoxy rather than TiteBond III for all your joints, because they're likely to be stronger. Blade shape is something you're likely to be in a quandary about. But it is far less important to propulsion than oar length. Swing as long an oar as you're comfortable with, and consider cross-handed rowing to gain length. Charlie |
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In reply to this post by JohnR
John,
What would you think of the canoe being built as a 12' footer, instead of the original design's 14'6"? That would create only an 8.27% reduction in weight. But it'd be a more efficient size to build from the point of buying lumber, as well as be an easier size to load onto roof racks. For sure, if the canoe is to be used as a double, then the increased displacement offered by the original length becomes a necessity. But if the boat is always single-handed --and by a petite rower at that-- greater displacement than would be offered by 12' isn't needed. As far as performance goes, a 12' would be the slower boat, due to hydrodynamics. So that would become the real "cost". How much performance would have to be given away to lower cost of construction and to gain ease of launching/unloading? Charlie |
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In reply to this post by Charlie43
Rushton Pulling Boat Followup Comments
I first launched this boat in late April. Now that I have had it out on the water a number of times I can comment more on it’s performance. But first I’ll do a quick build summary. Length: 14’ 4” (design length 14’ 3”) Beam: 43” (design beam 42”) Weight : 56 pounds (design weight 45 pounds) Draft: 2” with one person Skin: 1050 12 oz. Ballistic Nylon (design skin 14 oz. Ballistic Nylon) Sealer: Ace Hardware Poly-Finish, water-based, clear satin, 4 coats Rowing Performance: The boat tracks extremely well. It takes some effort to turn the boat, but this is easily implemented through rowing technique. Since the boat hull is symmetrical, tin tight quarters the boat can be rowed facing forward without shifting seat position. It takes relatively little effort to row at 3 knots or so. It takes significantly more effort to bring it up to hull speed (5 knots or so) but still nowhere near full effort on the oars. I took hull speed to be the point where my bow wave begins to increase without further speed increase. Wind and waves: When rowing into a l foot lake chop the bow tends to cut through waves rather than ride over them. The boat is so light that larger waves tend to stall forward progress. So I found I had to really keep the rowing speed up in those conditions. When rowing other than directly into waves the boat will roll over the waves, and even twist a bit. This is not a bad thing – it is kind of and easy non-pounding motion. I have encountered a condition regarding wind. The combination of light weight, round bottom and shallow draft allows the boat to easily be blown downwind. So in a breeze you need to point more into the wind than under calm conditions in order to stay on course. Stability: With a round bottomed hull and 43” beam the boat feels a bit tippy when entering it. Like a canoe, you need to step into the center of the boat and get your weight down fast. The boat then feels fairly stable. Once your weight is centered and you are moving, the boat is quite stable. I recently tested secondary stability in hot weather, calm conditions, and warm shallow water. I can sit with my hip against the gunwale and the boat is still stable. Only when I put my body weight on the gunwale and lean out over the water do stability problems manifest. (Much to the mirth of onlookers) The bottom line is that I am impressed and happy with the secondary stability. John R. |
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