Tuesday, 26 May 2020
So I figured I’d omit the down-haul, and instead weight the rudder with lead, similarly to the centerboard. Hey, every little bit of tighting moment has to help some, right.
This time with the lead, I just went and bought a pile of lead flashing. I melted it in an old cast iron pan outside, and poured it into a mold made from steel and aluminium.
Tuesday, 5 May 2020
They’re all Le Creuset, mostly vintage. Two of them have had the enamel stripped and replaced with seasoning.
Sometimes I just chuck in whatever’s in the fridge. Pepperoni, chorizo, cherry tomatoes, mushroom, etc. But that usually ends in a thicker omelette that won’t fold.
Sunday, 3 May 2020
- Beam of around 2300mm, to allow the boat to be stored behind my house (the gap between the fence and my garage is 2400mm). This will also allow for trailering without wide load placards, being under 2400mm.
- Length of around 6000-6500mm. This is a bit more vague, as there's no specific constraint here, but the 6m length tends towards a 2300mm beam, so this is it.
- Maximum draft of around 800mm. More than this makes trailer launching at boat ramps really hard. Indeed even launching a boat with an 800mm draft will be hard. Stability and cabin room is however directly related to draft, so there is a strong push to maximise draft at the expense of trailerability.
- Maximum weight of around 1800kg unladen. The tow vehicle I am considering has a maximum towing weight of 2500kg. If we subtract 700kg for trailer, we end up with 1800kg for the boat. Stability constraints again push us upwards here, and trailerability constraints push us down. I think something around 1400-1500kg is probably reasonable. This implies a displacement of around 2000kg.
- As much sailing ability as I can get given those other constraints. Ideally I want something I can sail across the Great Australian Bight in, so some measure of blue water capability.
I'm working on the premise of a 6m LOD, 2.3m beam, 0.6-0.8m draft boat with centerboard mounted in a trunk below the cabin floor. Katie comes pretty close, but the draft is perhaps a little on the shallow side, at around 0.48m board up. Pretty-much everything that's designed without a board has a draft of over 0.9m, which I think is just a little deep.
To find a better compromise, I thought I might try developing my own hull shape. I started with the table of offsets for Buzzard's Bay by Herreshoff, as published in Sensible Cruising Designs. I found the table of offsets to be surprisingly lumpy, so abandoned any attempt to stick to the table of offsets and instead just started drafting lines in Sketchup. The process was first to draw a profile (face), and overall plan view, to constrain LOD, beam and draft. The shape is similar to Buzzard's bay but I brought the bow up more vertically above the waterline, and increased the radius of the turn of the bilge, giving the rabbet a hard inflection rather than a smooth curve.
Then I drew waterlines and stations, got them to line up, drew buttocks, found they were miles off fair, edited the waterlines, edited the stations, edited the buttocks, and went around the loop half a dozen times, until the waterlines, buttocks and stations all intersect with errors of <1mm or so. I think the shape is reasonably pleasing.
Here's the profile:
The plan view is below:
The rear view is also shown:
Finally the quarter-view. I haven't sheeted the hull in sketchup, so it's just a bunch of lines.
Friday, 24 April 2020
So today I assembled everything I have for a test-fit. It took us about half an hour in the driveway to put it all together. First views from the side, aft, and forward:
You can also see the missing bronze fitting that’s supposed to go on my boom, plus a bunch of cleats. At the bottom is my 3:1 centerboard lifting line, using a 29mm double block and a sheave with becket in the board.
Sunday, 19 April 2020
There's a lovely video tour of Katie available at Off Center Harbour.
Katie is a good compromise between draft and stability. She makes use of a lead keel plus a centerboard. My only reservations with Katie is that the cabin is a tad small (Harry designed her to have a big cockpit instead) and I can tolerate a bit more draft than she has in order to improve stability. So some quick doodling on the picture of the plans that I have to illustrate my changed:
Firstly I scaled her vertically by 105%. This small change adds about 25mm of draft (from 480mm to 505mm) and 25mm of freeboard. It also gives me an extra 50mm of headroom in the cabin.
Then I add ballast to bring her waterline up by 25mm. That resets the freeboard to 480mm, and now my draft is 530mm.
My keel extension will add about 50mm on the bottom of the boat, giving me a total draft of around 580mm. I reckon this is still trailerable. It's certainly a lot less than the 900-1200mm draft of other designs I've been looking at.
Harry mentions that Katie originally suffered from mild weather helm. He cured that in the original by adding keel at the rudder end. I propose extending the centerboard back by around 250mm to deal with this. Additionally because of the taller keel we're able to drop the centerboard down a tad so most of the centerboard case inside the cabin is at floor height.
Finally we simply extend the cabin by moving it's bulkhead back around 500mm.
The results of my doodles is shown below:
Friday, 17 April 2020
That's utterly unacceptable.
I'm thinking now of starting on a small "pocket cruiser". Something that I can pull out of the water and keep in the back yard under the pergola when I'm not cruising in it, but still with enough size, weight, and cabin to really go places.
Also I'm fed up with plywood, so I want to make a boat from cut timber. Clinker is the romantic ideal, but strip built is probably going to be a lot more amenable to keeping out of the water for extended periods, so I don't completely get away from epoxy.
I asked for ideas on the woodenboat forum, and have been inundated with suggestions. Seems a lot of people have been thinking along these very same lines.
Here's a spreadsheet tabulating most of them.
Monday, 13 April 2020
So this is what that looks like for Elena:
I’m wondering if perhaps a cooler way to do this might be a loop of Dyneema rather than bronze.
Edit: I made a 20cm bridle from 5mm dyneema. This is the shortest I could do maintaining 20:1 bury in the brummel lock splices. The eyes go over some 12mm dia bronze tubes, which sit under the shroud attachments. I reckon this is much nicer.
Saturday, 11 April 2020
We started with "Masks don't work, and they'll probably increase your risks of getting the virus", accompanied by pictures of health workers wearing (you guessed it) masks, and newspaper stories about the incredible shortage of masks and other PPE for health workers.
Any idiot can tell the reasoning for the message is that while masks do work for reducing spread of the virus, if everyone tries to buy them then those who need them the most (health workers) can't get them. So it makes good sense that the health authorities would lie to us here.
Now the conversation is getting a bit more honest. There's a grudging admission that masks do work, especially when worn by people who have the virus and aren't showing symptoms yet. So the advice is to make something, using multiple layers of t-shirt cotton or teatowels.
It's straightforward arithmetic. A certain percentage of people have the virus but are not showing symptoms. The public health response around people who are showing symptoms is quite good, limiting transmission. It's the asymptomatic carriers that are responsible for an increasing amount of spread. Social isolation works in general here, and widespread wearing of masks in public also helps.
In general, act in public like you have the virus. If you have the virus, the first thing you'd want to do is stick something over your face so you can't breathe droplets of it over everyone.
Being an engineer, I'm not convinced of the efficacy of a piece of woven cloth. The weaving pattern makes uniform sized holes in the weave, through which stuff is easily able to move. I've previously used non-woven poly cloth (specifically engineering wipes) as efficient filters, so a bit of google-fu revealed that this material is the secret-sauce in real facemasks.
So let's make some facemasks. They aren't going to be N95 or P2 certified, but they're going to be a whole lot more effective than something made from t-shirt fabric.
We start with the ingredients. My fabric is electrolube ECW engineering wipes, which are widely available, from for example Farnell. Each wipe makes two masks. I also use some 6mm elastic for holding it to your head, and some 1mm magnet wire for forming the nose bit.
Make the nose wire from a piece of magnet wire, or really anything that you can stick in that will bend easily and retain it's shape. I whack a little loop in the end before insertion so that it doesn't poke into your face.
Saturday, 4 April 2020
It’s getting closer and closer.
Tuesday, 31 March 2020
These were both glued to a 3m length of 19mm x 75mm Tassie oak, and a bit of a slot was cut in the aft metre to allow for a block to increase outhaul purchase. Using a block, I can either go for 2:1 by attaching directly to the clew, or else 4:1 by looping through the clew back to the end of the boom.
I also cut slots in the side pieces for the outhaul to exit, and finally I mirrored everything on the other side. Then I glued it up and went at it with the power plane to make a boom-shaped thing.
The ends are 55mm round,and the center section is 55mm wide by 75mm deep. The taper at the mast end is short, over about 800mm, to ensure I've got full thickness at the vang attachment point. From the main sheet attachment point to the end of the boom it tapers over a distance of about 1400mm.
The rear shows the slot for the block, about 16mm by 35mm:
This shot shows one of the outhaul exit slots nicely. With a 2:1 outhaul I simply did an exit slot on each side, each of which will have it's own cleat, meaning the authaul can be easily tensioned from either side of the boom.
Sunday, 8 March 2020
While the drill bit was still in the hole, I thought I'd have a go at stepping it single-handed, as one does. I started by extending the jib halyard to the bowsprit, and attaching it with a simple bowline. The mast was resting on the transom bridge, with a couple of towels ensuring paint doesn't get scratched.