Tuesday, 23 December 2014

Postage bastardry

One of the challenges I'm having is getting materials to build my boat with. I live in Geraldton, Western Australia (not to be confused with the other WA). It's about 450km north of Perth, the capital of WA. I rather like bronze, but none of the local metal merchants stock it, none of the Australian mobs I've found are interested in small quantities, so that leaves American online mobs.

I bought a piece of C220 bronze sheet from McMaster Carr recently to make bits from. So far I've used some to make plates to support the becket on my centerboard uphaul, and the cover plate featured in my last post on the front thwart. McMaster advertised a 2" x 24" x 0.09" piece of bronze for US$41.27. Expensive, but them's the brakes. I ordered it, and it showed up a week or so later. The cost on my card: AU$106.72. So the shipping was just as expensive as the metal.

So I asked on the woodenboat forum if there were any alternatives to McMaster, and found online metals. They will cut sheets to fairly arbitrary sizes, and are at least upfront with shipping. I tried a 12x1x0.125" piece of 220 bronze. US$14 for the bronze, but a staggering US$123 for shipping. Just for fun, I tried a 1x1x0.125 piece:

Yup, US$123 to ship a poxy couple of grams of bronze. Bastards.

Monday, 22 December 2014

Getting the insides of the seats sorted before sealing things up

Lots of little jobs. I've done 2/3rds of the third plank, and am starting to have to think hard about the order of events, so I don't make it impossible to do things.

First thing first, I finished off the front thwart. That meant making mounts for various pieces of gear; a 180W sinewave inverter for charging electronics from the battery, an AIS transponder, and an antenna switcher so the AIS transponder and VHF radio can share the same antenna. I also made some access holes in the thwart, both for the VHF antenna, near the mast tabernacle, and so that I can run power and coax back to the cockpit for a radio.

In the first photo you can see where I've added rails for the gear (on the inside, alas). You can also see a little bronze plate I made to seal up the antenna port, just next to the spine.

On the other side of the thwart the hole for other cabling is visible, complete with paint run. I'll cap that off with another bronze plate. Also if you peer into the hatch you can see a power point, for charging devices.

Moving to the cockpit seats next, I added pieces of timber to locate the backs of the seat tops in between bulkheads.

Then I spent ages doing fillets, sanding, cleaning up fillets, and coating everything inside the seats in epoxy. I'm currently vacillating as to whether or not to paint the inside of the seats. I also added hard points to the seat fronts. These are just bronze rings that I turned up. The idea is that they support a rod onto which the rowing stretcher mounts (the three at the right), and the one on the left supports a rod which in turn supports raised planking, forming a sleeping platform. That's the idea, anyway.

Friday, 12 December 2014

New Apple based MythTV machine for home.

I've got a really low tolerance for television commercials. Since the introduction of free-to-air digital television in Australia, we've used a computer at home to record the broadcasts so we can watch stuff at our leisure, and skip the ads. I just installed version four of our hardware, going in a slightly different direction to the previous three.

So in chronological order, here's what I've done in terms of watching television:

  • A Via Eden 800 MHz (from memory) Mini-ITX motherboard, with power supplied via a 60W 12V power supply and pico-PSU, using a PCI DVB-T capture card and 2.5" 400GB hard drive. We ran Ubuntu on this machine, with MythTV. This machine was a complete dog. It was expensive and slow. I bought the mini-ITX motherboard because I was hoping for something that would fit in with our home stereo. It was hopelessly underpowered, despite claims that is was "good enough" to do SD content. It drew around 30W of power.

  • A Zotac ION Mini-ITX motherboard in the same case as the previous machine. This one used an Intel Atom processor and nVidia ION chipset, which had hardware acceleration that was quite capable of reliably displaying HD content. No PCI slot, so I bought a pair of ASUS U3100 USB DVB-T tuners. I added a WD green 1TB 3.5" hard drive in the space liberated by the tuner card. This one we kept for quite a while (I still have it in my donga with XBMC installed). My issues with this one were more around Ubuntu and myth than the actual hardware. It was pretty early in the days of VDPAU, so every time Ubuntu insisted on an upgrade the video hardware acceleration would break, and I'd spend a frustrating day or two googling for magic incantations to get the thing working again. Also the atom processor was quite sluggish - things like navigating menus was painful. Despite being more powerful than the Via board, it was rather more energy efficient, drawing 22W at idle and around 30W playing content.

  • One upgrade I got sick of it. I'd recently bought myself a nice macbook air for my study, so my old study machine went into the living room. This was a standard ugly desktop PC, with an Intel core 2 duo CPU and nVidia ION chipset in a normal micro-ATX form factor. It had enough power that it'd just work, VDPAU or not. I filled the case with sound absorbent foam in an effort to reduce the noise from the hard drives, and fitted some nice quiet Noctua fans and monster heat sink. I used a small 220W energy star sparkle power power supply in a bid to reduce power consumption, but only managed to get it down to 40W at idle. But it was good enough. We ran with this machine for about 4 years until it recently died.

So now on to our latest machine. Since the acquisition of the macbook air and a retina macbook pro for work, I've become quite keen on Apple hardware and OSX. The hardware is really high quality and just works. The software doesn't break on every update like you tend to get with Ubuntu. I took a deep breath and ordered a spanking new 2014 model Mac mini. I went for the mid-spec model, with i5 processor, Iris graphics, 1TB hard drive and 8GB ram. The plan was to install MythTV under OSX and be free of the linux "almost there" annoyances once and for all.

One gotcha. My DVB TV tuner cards won't work under OSX. Turns out there are no USB tuner cards that work on OSX. My only options are a "HDhomerun" network tuner, or else to build a separate (linux) backend on a different machine with my USB tuners attached to that, effectively replicating the HDhomerun network tuner but adding disk.

That's my long term plan - buy a low power box like an Intel NUC or another Mac mini, install Ubuntu on it, attach a pile of disk and hide it in a cupboard running my backend. That way it'll be doing what linux boxes like to do - running services. No need for X11, no unity, no display. I'll SSH into it when I want to do maintenance.

For now I just made a dual-boot mac mini, and am running MythTV under Ubuntu, so much the same as our previous box but much smaller, neater hardware.

Getting Ubuntu and myth running on the mac mini was a bit more of a pain that I anticipated. You'd think it'd be straightforward on mainstream hardware, but no. Here's the steps I went through, more for my own reference to reduce the random google-fu next time than anything else:

  • Install rEFIt under OSX and repartition the hard drive using the OSX disk tools to make room for Ubuntu. I chose to give OSX 200GB and leave 800GB for Ubuntu.

  • Install Ubuntu 14.04.1 from a USB key. Relatively straightforward - instructions are here.

  • Get my Apple bluetooth mouse and keyboard running. Gotchas were not pairing with the mouse, and upower being retarded and annoying me with "battery 0%" warnings every time I pressed a key. The fix for upower is rather satisfyingly to nuke it. It's not like you need power management on a machine plugged in to the wall, anyway.

  • Install mythbuntu under Ubuntu. Importantly don't install mythbuntu by itself, as it doesn't include all the tools that are needed to get everything else (bluetooth mice etc) working.

  • You'd think that in 2014, after a decade of myth, that a fresh install of the current stable version would work. Alas no. Myth development people are adamant that their product will never get widespread use, and they do this by only half setting up their database connections. Much stuffing about was necessary before the backend and frontend would talk to the mySQL database. No links for this, as by the time I found the incantations I was about ready to give up on myth entirely and didn't write stuff down. Anyway, I'm sure the problems will be different next time.

  • Go through the same Unity "legacy full screen support" pain that I've had to do ever since Canonical forced this useless desktop on everybody.

So yeah, now we've got a stable myth install running on our shiny new mac mini. The operating system is terrible, but the hardware makes up for a lot of that. It just works, and pulls a measly 11W at idle, and that's including the pair of Asus DVB tuner cards, which are about 1W each.

Alas it's no good for playing my music collection, as I was hoping for. The plan to run a separate backend with OSX frontend is still there, so I never again have to deal with unity, bluetooth, upower, or all the other user interface annoyances that accompany every linux machine I've ever dealt with.

Here's a photo of our hardware. On top of the mac mini is an apple TV, which we use for watching Orange is the new Black, and a wifi hotspot. The tuner cards are hiding under the power cable for the apple TV.

Edit: But wait, there's more! Another incantation is needed before my Apple dvd will talk to linux.

Monday, 8 December 2014

More planking, and starting to finish out the thwarts

With the second course of planking done, a little bit of thought needs to be put in to what's next, as access to various bits of the boat gets much harder as the planks go on.

Before putting the third course in, I finished out the underside of the anchor well and fit the anchor well floor. This has to be done now because, with the king plank in there, the only gap big enough to get the floor in is between the stringers where the third course of planking will go.

Similarly, once the third course is in, I've really got to do the front thwart, as the top for it only barely fits between the stringers where the fourth (top) row of planking go. Finishing out bits like this provides a useful relief from the monotony of planking, though doing fillets is one of my least favourite jobs. I've got a good recipe for the aquacote epoxy undercoat and polyurethane topcoat now. After getting the fillets to a state where they don't look revolting, I put on an even coat of unthickened epoxy with a foam roller. Then I sand that smooth with 80 grit, and apply two coats of undercoat, again using the foam roller, with a paintbrush for the fiddly bits.

The trick with the undercoat is to apply a very thin initial coat, wait about two hours for it to get super tacky, and apply a second slightly heavier coat. That way there are no runs and good coverage.

Finally I do three coats of topcoat, again using the brush to get paint into corners, and smoothing everything over with a foam roller.

Here's a close up shot showing my battery mount. The plan is to hide an Icom IC-400BB marine radio in here, with the controls on the handpiece remoted back to the cockpit, plus a Vesper marine XB-8000 Wifi AIS transponder so we can see where other shipping is, and they can see us. The 20Ah battery will provide oodles of life.

The battery will be secured with a strap and clip, so it'll stay put even if we capsize.

Here's a photo showing the lid on the thwart. I've run out of epoxy filler, so am champing at the bit until more supplies arrive, at which point I'll finish this bit off and get back to planking.

Finally I took a break from boat building to bake some stuff for a work Christmas party. Guess where the cat wanted to sit.

Sunday, 23 November 2014

Half way through planking

This planking gig is actually very easy. Much easier than it looks. You get into something of a rhythm and just turn out planks at the rate of one or two a day.

After an hour's work cutting the bevel into the top of the garboard plank on the port side with my no. 4 and not really getting anywhere, I bought a new cheaters tool, a nice Makita power planer. Where I call my Stanley no. 7 Mr Smooth, this thing is called the brute squad. It removes material at a somewhat disconcerting rate.

Here's what it does to the garboard plank.

To speed things up, I just cut my sheets into 300mm wide lengths. These are light enough for me to put on to easily mark up. I simply clamp one in place, trace along the stringers, add a bottom line with a batten 30mm down from the top of the lower stringer, and cut to shape. After a second test fit to check things, I clean up the edges with either my no. 4 or my spokeshave, depending on whether it's convex or concave, then glue it to the boat.

A little more work is needed at the bow. I decided to disregard advice and try a classical gain, cut with a saw and chisel. I start by ruling a line along the garboard plank 30mm down from the top edge. Then I cut along the line so it barely makes it through the ply at the bow, and surfaces about 200mm back. I added a second cut half way along so I could easily gauge how deep I was going with the chisel.

Then I pare away material with the chisel. As with cutting scarphs, it's actually pretty easy, as the layers in the ply guide you and let you know how deep you are.

An aside: I'm not impressed with these Record Irwin chisels. They were the best I could find locally, but they're really soft and don't hold an edge for long. At least they sharpen easily. My suspicions about soft edges were confirmed when I dropped this one on the concrete floor, and the tip actually bent over rather than snapping. Also, the rubber bits on the handles are falling apart before my very eyes. I've got my eye on some nice Veritas ones. If they're anything like my spokeshave they'll hold an edge forever (and be a real PITA to sharpen).

Next I use some 80 grit emery wrapped around a large flat file to get everything nice and flat and even. Oh, incidentally, the break from the last post is in this picture. Look carefully. If you're having trouble finding it it's about 1/4 of the way across from the left.

So here's the last plank for the second level being test fit. Of note is that I'm not using screws to pull the planks into the one below. I find that a simple piece of wood between stringers allows me to put even pressure top and bottom with the one clamp. I'm hoping that'll make the cleanup job easier when I flip the boat over.

Here's another view of the clamping process, on the other side, with gratuitous cat content:

Tuesday, 18 November 2014


I put the starboard garboard plank on yesterday. Much the same process as with the port side. However when I went in this morning and removed the clamps, I found this:

Here's a closeup of the split. It looks like the ply has delaminated.

What to do? It looks like the split is mostly in the area where I'll be cutting a gain. Could I fill it with epoxy and clamp it up? What's going to happen when I cut the gain? I imagine taking the plank off will be a huge awful job.

Edit: On the advice of the incredibly helpful crew at woodenboat forum, I tried injecting epoxy to relaminate the ply. I figure if it doesn't work, I'm no worse off - I just cut the plank away and start again.

Here's where the shameless cheating begins. I've been trying my best to use mainly hand tools building my boat; my spokeshave, an assortment of planes and chisels, I even find I grab a hand drill in preference to the electric one. All that just went out the window. I borrowed a pneumatic paste dispenser and went at it with that. This little gizmo is unlikely to be found in most garages...

So the cheating begins by mixing up a batch of epoxy. I'm going to be forcing it down an 18ga needle, so it has to be free of lumps. I use a strainer to ensure the silica is non-lumpy and add enough to get a cream consistency.

Then the stopper goes in the syringe, and the syringe is loaded into the dispenser. This tool is designed for dispensing tiny dots of solder paste for PCB assembly. Solder paste is thick goopy stuff, much like glue.. It works by putting a carefully metered air pressure on the back of the stopper.

So the needle goes deep into the split, and I pump epoxy in. I filled it with about 1.5ml, at which point it was starting to run out.
Finally I clamp it with a piece of ply and some plastic builders film up against the face. I got good squeezage out the top, so there's a good fill of epoxy in the break.
Second edit: Here's the result after taking the clamps off this morning, giving it a wipe with 80 grit, and using the spokeshave to trim the plank down to the level of the stringer:

I reckon that'll do.

Thursday, 13 November 2014

Making the most of the FIFO lifestyle

A quick break from boatbuilding. There's been quite a lot of media coverage of late on an enquiry into a spate of suicides of Fly-in Fly-out (FIFO) workers here in WA. I work in remote WA, though not, unusually, at a mine. So I've been taking a keen interest in the coverage that's been going on, and engaging in some thinking (there's plenty of time out here for thinking) about what works and what doesn't work when you're away from home in the middle of nowhere for a significant part of your life.

This article by Wenlei Ma gives, I think, one of the most coherent accounts of what FIFO work is really like. The key to the difficulties aren't so much the work itself, which is hard, hot and dusty, but more the challenges of being away from family with very little to do but miss home, and the possibility for friction between colleagues in what's effectively a tiny condensed country town.

The other week RED FM announced a competition, called "show us your donga", with a $1000 travel voucher for the donga judged best in the state. I got enthused about that and figured I'd take a decent photo of mine, but then read the fine print of the competition and decided not to enter. Instead I figured I'd share the photo here.

We've got a reasonably good deal at my workplace. Some things really need improvement - for example our accommodation dongas are very basic. There's no shade, very few facilities, lots of dirt everywhere and no FIFO pay (unlike the mines, which shower their FIFO workers in allowances). That said, the huge salaries that mining FIFO workers get are a trap in themselves, encouraging high debt levels and creating a position where people who can't cope with the lifestyle feel trapped. On the plus side we have very good food, very short rotations (five days on, two days off), good communications with home, a great bunch of guys to work with and a very relaxed informal atmosphere where we're encouraged to personalise our rooms, which you'd never get on a mine camp.

So here's what my room looked like when I moved in, a couple of years ago (this is actually a neighbouring room, as mine was already well customised by the time I thought to take a photo). Spending too much time in a room like this is sure to do your head in.

Because we're a pretty small operation, we don't have much in the way of recreation facilities. We essentially have a 3m x 3m rec room with a telly and a sofa, and a small gym room. While I get on really well with my workmates, I also really value my time away from them. It's plenty enough to be working a ten hour day, plus eating meals together. When I'm back at camp (around 14 hours a day) I mainly stay in my room, which I see (and my workmates respect) as very much my space. This allows me to relax and recharge, and gain some outside perspective, so I can start the next day fresh.

So over the couple of years I've been working out here I've done what I can to improve the place. I started by buying a television and bringing an old home theatre PC from home so I could watch movies and listen to music stored on a hard drive. Since then my employer has cottoned on to the television thing and bought us all nice 32" LCD televisions with satellite decoders, so I can watch the same crap on TV that everyone else does. I've also got an Apple TV so I can download movies, TV shows (I'm a huge Orange is the new Black addict) and music from itunes. We organised telephones for rooms where people wanted them, and we have really good internet, so I can chat with Perry on facetime whenever I like and for as long as I like.

This is a really important part of coping with working remotely for so much of my working life. We chat every evening at 7pm, just after dinner via facetime. We ramble on about what's happened that day for half an hour, I try to engage the cat in conversation (he always ignores me), and we just do what we can to alleviate the isolation that both of us feel when we're apart.

So after getting the comms going nicely, I set about making my room less stark. I bought carpet tiles from Bunnings and made some nice curtains with proper sheers and tie backs so I could get some light into the place without people walking past looking into my room. I brought out my own doona and pillow, and brought out a set of shelves so I had somewhere to keep things. Mainly lots of bad fantasy novels and junk food.

The wall alongside the bed is shared by the next room along. While my neighbour is as quiet as a church mouse, I'm really conscious of not making too much noise. So a lot of what I've done to the room is about making it so I can listen to music etc. without annoying the neighbours. I'm generally lying in bed while doing this stuff, so installed a couple of little Cambridge Audio speakers either side of my pillow. They're right by my head, so provide really good audio at quite a low level - I can be listening to music or a movie, then sit up and hear stuff all. Just like wearing headphones, but without getting sore ears. I built a nice little 10W MOSFET amp to drive the speakers, which has super low noise and distortion, and have an easily accessible volume control just by the bed.

To further cut noise down, I put a sheet of gyprock up (painted red to further personalise things) between myself and the neighbouring room, with sheets of sound absorber goop underneath it. Shortly I'll fill in the rest of the wall above the bed with a long bookshelf, providing even better sound attenuation.

We upgraded our coffee machine at home, so I took the old one to my donga. It's pretty cool to be able to make myself a really nice cuppa in the morning. Sometimes of an evening I use it to make hot chocolate, and I have a stash of marshmallows for just this, along with licorice of various sorts (I'm an addict) and some booze.

Finally I built a nice shelf to put my satellite decoder on from Tassie oak and some offcuts of marine ply under the telly, and some better shelves under the desk. The result is really comfy and homely.

The sound system also allows me to mask the drone of the airconditioner. It gets to 48 degrees at the height of Summer out here, and often doesn't fall below 30 at night, so for a few months each year we have to run the airconditioners 24 hours. I find if I have some music playing quietly, I'm able to sleep a lot better than just listening to the aircon.

Anyway, hope you've enjoyed the tour :)

Sunday, 9 November 2014

First course of planking - bow end

It was with a great sense of foreboding that I set forth on the quest to fit the bow end of the port garboard plank. Tales of woe, misery, and giant squids climbing out of the anchor well and throttling the unwary sailor abound on the high seas.

Actually I was getting a little carried away there with the bit about the squid. I'm rather partial to squid for what it's worth, especially fried with salt and pepper and some lovely fresh chips. And whilst there is a (vanishingly remote) possibility that one could make it the fifty odd metres from the ocean (what's that in leagues?) to lurk in my anchor well, it's pretty likely my trusty guard cat Mogget would get the thing well before it took up residence. Not to mention that until I've finished planking, the anchor well isn't, well, a well.

Where was I? That's right, I was pointing out that whenever you read blogs describing the building of navigators, there's always a lengthy description of how awful it is to pull the garboard plank around to sit nicely on the stem. So I approached the task with, as it happens, considerable trepidation. And foreboding. Did I mention foreboding already?

The process starts the same as all the other planks. I put a length of ply in place, mark it with distances, and use that as a template to cut the real thing. I left it a little oversize, particularly at the front. Then I clamped it to the plank immediately aft and progressively pulled it into place, mainly using pusher clamps off the building frame.

Here's the crux of the problem that everyone has. The plank doesn't want to pull neatly around the foot of the stem.

I solved this problem by going at the foot of the stem with a spokeshave, and using a clamp right at the back of the stem to pull the plank the rest of the way in. Then I ruled a line for the stem on my plank and cut it much closer in size. Here it is on test fitting eleventy of lots. You can see that there aren't actually all that many clamps involved to hold it in place. when you get the bow in, much of the rest of the plank pulls up hard.

Once satisfied with the fit I gooped it up with a truly heroic amount of epoxy and put it back on. This time I used a few more clamps to make sure the joins are all nicely closed. I'm really glad I put the king plank and inner gunwales on before doing this. The bow is as solid as a rock, and didn't pull out of true at all.

Here's a view taken from the bow just to satisfy myself that the boat is still straight. I really like the curve this plank makes. Very cool. Note the clamp on the opposite side of the building frame from where I'm working. This ensures the frame doesn't pull too much out of true.

Finally here's me getting an even coat of epoxy in my hair, whilst cleaning up the fillets deep in the bowels of the beast.

Saturday, 8 November 2014

First course of planking - aft end

John Welsford recommends starting the planking at the aft end of the boat. This way you get a little practice before hitting the bow, which I'm led to believe is rather hard.

We started by buying more sheets of 6mm ply. I didn't have easy access to a trailer for this lot, so instead bolted some 2.4m lengths of pine to my roof rack, and clamped the sheets of ply to that. It worked rather well.

We used a scrap bit of ply to "spile" the plank. This was done by ruling lines along the ply at regular intervals, clamping it where the plank would go, then measuring off the end of each line to where the floor and first stringer are. I wrote these numbers on the spiling plank, then transferred the points to a sheet of ply, interpolated with a batten, and cut the plank out. I spent a little time finessing the join between the plank and floor, then duplicated it for the starboard side.

I did a proper dry fit and finessed the lower stringer to ensure everything pulled in nicely.

Once I was happy it fit, I drilled some holes in it for ties, mixed up a batch of goop and stuck it on the boat. I repeated the process for the starboard side, then for the next plank forward, which goes all the way to just forward of bulkhead 3. The photo shows the port midships lower plank setting up. Lots of clamps, and lots of copper wire ties. This is as much as I'm comfortable gluing on in one go. I had to work faster than I like for fear of the goop going off before everything was clamped up. As a result I think I got as much goop on myself as on the boat.

The midships plank is joined to the aft plank with a simple doubler. I was originally going to scarf the plank, but figured I'd just (for once) follow instructions. It turned out nicely.

Once the dust settled from my panic, I pulled the ties, cleaned up the excess goop with hot air gun and scraper, and layed in some fillets. Then I put a layer of 70mm wide 200gsm fibreglass tape along the seam to strengthen it.

Here's the open area amidships. I've done both sides up to bulkhead 3. Now for the dreaded bow end...

Thursday, 30 October 2014

Finishing the birdsmouth mast prototype

Continuing the exercise, I opened the slot up with a 6mm router bit, cut a couple of V cuts into the back of the sailtrack section to lighten it, and bevelled the sides of the sailtrack section with a plane. Then I glued the rest of the staves together, forming a rough birdsmouth section.

Once this had set up I planed off the sharp edges, then planed it into a sixteen sided figure.

Then finally I planed it further to a 32 sided figure, and sanded it reasonably smooth. I think the results speak for themselves. If nothing else, it's rather pretty.

And now for the moment of truth. 489g for 30cm. That's 1.6kg per metre, or right on 10kg for a 6.1m length. I reckon that's reasonably light.

Wednesday, 29 October 2014

Prototyping a modified birdsmouth mast with an integrated sail track

Out here in the boondocks in Western Australia we don't have terribly much access to traditional boatbuilding timber. Douglas Fir? Not a chance. Spruce? You've gotta be joking.

What we do have in very plentiful supply are Jarrah and Tasmanian Oak. Jarrah is an incredibly dense, strong, durable timber. Great for railway sleepers (all the railway sleepers in the London underground were made from Western Australian Jarrah), but challenging to build a boat with. Tasmanian Oak is slightly less dense than Jarrah, but still isn't exactly a lightweight timber. So I'm wanting to build a wooden mast. You can see my dilemma. There's no way I'm going to build it out of Pine or Western Red Cedar, because both are much too soft. I'm interested in the birdsmouth construction, but I want a sailtrack, and I can't think of a straightforward way to do that with normal birdsmouth.

Well if a simple method won't suffice, surely a complicated method will. If I build a sailtrack piece out of Jarrah, then use that to replace the back three birdsmouth staves in an eight sided spar, then mirror everything so the left and right sides are the same, I end up with something that will do what I want.

So I designed my mast in sketchup. The birdsmouth bits are 30mm x 12mm Tassie oak. The sailtrack bit is made from two pieces of 30mm x 12mm Jarrah, cunningly joined after cutting the track with biscuits. Then a pair of 18mm x 30mm tassie oak bits get laminated on, and more cutting happens to make the back of the mast. After assembly the whole lot is planed to an oval shape 63mm wide x 76mm long.

Sounds easy! I wasn't so sure, so thought I'd prototype something. Importantly I want to use only methods of construction that will work with 6.1m long bits of timber. I'm thinking that means doing everything with my trim router.

I started by cutting the birdsmouths into my 30mm x 12mm tassie oak. I used a 12mm dia 90 degree V bit in my trim router, with some guides screwed into the base.

I repeated the exercise with a 12mm round bit in the side of some 30mm x 12mm Jarrah to make half the sailtrack.

Then I laminated two pieces of the sailtrack Jarrah, plus two lengths of 30mm x 18mm tassie oak. This is going to be the hardest part with the full length mast. Keeping squeezage out of the sail track is going to be hard. For the prototype I forced some wadding down the track once it was assembled to clear the squeezage. Doing that over 6.1m is going to be challenging. It might be easier to cut the slot part before gluing so that I can get access to the inside of the track.

Once my lamination had set up I cut rebates into the tassie oak part to locate the front five staves.

This is what my prototype looks like now. I still need to bevel the back sides and cut open the sailtrack slot, glue the whole shebang together, then plane it to an oval. I weighed this 300mm section this morning at 649g. That's with a fair bit of material still to be removed. That means a 6.1m mast built like this should weigh around 13kg, and hopefully be as strong as they come...