Monday, 25 January 2016

Wednesday, 30 December 2015

Making the most of your eighties computer.

Before the rise of the PC in the mid eighties, there was much more diversity in home computing. Australia even had it's own home-grown computer, called a Microbee, designed and built in Sydney. I was a teen in the eighties, and a 32K Microbee "Personal communicator" was my first real computer. It made quite an impression on me, and to this day I'm really fond of them.

Technological advances are brutal, so old computers get ruthlessly discarded. This is bad, because it means that we are in very real danger of losing an important part of our heritage. Think about it. Who has a floppy drive on their computer? How about a 5.25" floppy drive? How about 8"...? So if you had an important piece of data on a 5.25" floppy, what would you do?

People care, and there's a movement to preserve old digital things. One that I've made some contributions to is the Microbee Software Preservation Project, a group of people who collect, digitise in modern formats, and distribute everything they can get their hands on relating to the uniquely Australian Microbee.

The primary way to keep this stuff alive is to play with it now and then. People have written emulators, such as NanoWasp, which even runs in a browser. There's even a VHDL description of a bee, which is way cool. But I like physical hardware (being an electronics nerd and all). So I've got a few old Bees, one which uses tape and a couple which use old floppy disks. The tape ones are the most easily accessible. Plug into power, plug into a monitor, load a tape, play games. Just like it's 1983 again.

So if you're like me, you'll have stashes of the computers and software, but not a lot of the other paraphernalia that goes with it, like disk drive, monitor, printer, etc. Monitors and disk drives are heavy and fragile, and take up a lot of storage space, so they're usually the first bits to go to landfill.

Not all is lost. You can still play with them, at least with Microbees. A television makes a great monitor, and your PC (mac in my case) makes an awesome tape drive. Go check out the MSPP site for .wav encodings of Microbee software, that will play (making an awful noise if you forget to plug the bee into the speaker output) on your PC. I find full volume works best.

Microbees used a video standard called composite. Back in the early eighties you could buy composite monochrome monitors, which hooked up to the computers of the time and displayed lovely green (or sometimes amber) text. These were rapidly replaced by CGA, then EGA, then VGA, then HDMI, so finding a proper composite monitor is hard.

Not all is lost though. Your DVD player and set top box also have "composite" connections, which are close to those on old monochrome computers.

So, let's plug the Microbee into a modern television using the "AV" connection, which is intended for your old DVD player. The plug is the same as the "AV" socket on the back of the telly, and we straight away get an image! It works, kinda. Not quite as nice an image as a real old monitor gives, but pretty close. Here's what a small portion of the screen of my basic Samsung "720 HD" LCD television looks like playing a classic Bee game:

Now the differences between a television and a composite monochrome monitor are that the television is designed to extract intensity (called luminance) information colour (called chrominance) and sync (telling the screen when to start a new raster scan and when to start a new line) information from the same physical bit of wire. The monitor doesn't care about colour (chrominance), so it just encodes luminance and sync.

So there's no colour information. That's why it's white. I played with my television a bit and worked out that I could convince it that my monochrome data was in fact green. It's in the "advanced" display settings:

And that's made some improvement. But it's still pretty blurry.

For those of us in PAL countries, the colour information is encoded using the PAL standard. This puts the chrominance data on a sub-carrier, at 4.43 MHz, and has an audio carrier at 6 MHz. Importantly, the standard is designed to provide a video bandwidth of just 5 MHz. That's plenty for DVD video, but not quite enough for the Microbee display.

Working out the Microbee's display needs is straightforward. It uses a "pixel clock" of 13.5 MHz to shift out pixel information. The highest video frequency is achieved when pixels are alternately on and off. They're clocked out on the rising edge of the clock, using a 74LS166 shift register. So the video data coming out of the bee is at half the frequency of the pixel clock, or 6.75 MHz.

Now, 6.75 MHz is a tad higher than 5 MHz. That's why it looks, well, soft. Incidentally this is why early computers that were made to display on televisions typically only displayed 40 columns of text. You just couldn't fit more in the PAL bandwidth limit. And for the yanks, NTSC is even worse.

My telly has a "component video" input, that's made for newer DVD players. That uses three wires to convey the red, green and blue information, plus encoding the sync signals on the green wire. Because it's no longer PAL, there's no 5 MHz filter. What if I were to fool the television into thinking I have a component input rather than a PAL one?

Turns out this is easier than I ever imagined. I just plugged a cable into the red and blue inputs on the telly, and it decided it had a component input. The green one still goes to the standard "composite" signal from the bee.

Interestingly, we're back to displaying white, but much sharper white than previously. The television notices there's no data on the red and blue inputs, so defaults to a "luminance chrominance" mode where the luminance is on the green wire and chrominance is on the other two. Not to worry, we can force it to use RGB, in the same method as previously. And the results are spectacular. A display that's every bit as good as I could get on a high-end composite monitor back in the day:

Zooming back out shows my whole bee, ready to kill centipedes:

Wednesday, 23 December 2015

Varnish

Varnishing isn't easy. It takes a while to get good results. The good thing about it is you can always just apply another coat. I think I'm getting better at this, after (thinks!) six coats on my rowing thwart, I've got a reasonably good recipe that looks set to provide a tolerable finish, at least after a few more coats...

My ingredients are Feast Watson spar varnish, Penetrol and real gum turpentine to help the stuff flow, and a proper varnish brush, which is wide and very thin, so it doesn't hold too much varnish, with super smooth bristles, so it doesn't leave great big ugly brush marks. I'm thinning the varnish out with ~15 percent penetrol and a further 5 odd percent turpentine. That gives me a mix that flows out nicely. Of course that's a recipe that's highly dependent on environment, brush, technique...

I started sanding with 180 grit, but found 400 works better in the latest coats. Here's the rowing thwart thus far. There's a bit of general lumpiness but the gloss level I'm getting is fairly good:

My rowlock bases and tabernacle have had a couple fewer coats. In the case of the rowlock base that doesn't seem to be an issue, but the tabernacle still needs some love.

I find when I'm putting it on it's good to keep a little container with mixed varnish+penetrol+turps, plus one with half an inch of pure turps in it handy, so I can thin out and clean the brush periodically, to keep it from sticking to everything.

Sunday, 20 December 2015

Camouflaged cat is camouflaged.

See if you can spot the cat hiding in this picture:

Of course like all good cats, Mogget's goal in life is to ensure his paw prints are in all varnish.

Saturday, 12 December 2015

Finished the coamings

After gluing the coamings in place, the next step involved trimming them so they were the correct size. This involved a process not-unlike trimming my fringe. Take a little off one side, look at it from afar, take a little off the other side, look at it from a distance, take some more off... Luckily I managed to stop myself before I reached the deck.

Then I sanded things smooth, coated with epoxy + filler (this 4mm ply has a pretty crap open-grained face ply, which swallows epoxy), then a couple of coats of unthickened epoxy, then sand down to 180 grit, and finally toplac paint.

Here's what it looks like tonight.

The shaped bit in the bow is to allow clearance so I can flip the forward thwart hatches over. The coaming is about 65mm above the deck at the bow, and 22mm above deck where I'm likely to sit on it.

Next job is to complete sanding the decks out to 180 grit and then paint them with top coat. No, I'm not using undercoat. I really dislike the stuff - it clogs emery way too fast for my liking.

Wednesday, 2 December 2015

Metalwork!

Here's a padeye for my mainsheet. The usual arrangement for a dinghy is that one end of the mainsheet is terminated at the end of the boom. The sheet then goes through a block attached to a traveller or bridle across the transom (I still haven't made my mind up which way I'll go), then back through a block at the end of the boom, along the boom to about half way, then via another block mounted to the boom down to a block mounted to the centreboard case.

I have concerns about pulling a padeye out of the back of the centreboard case, as the loads might be fairly high, especially given that Geraldton is a windy place. It's hard to get inside the centreboard case to add a plate inside do through-bolt, so instead I'll use screws but screw into a couple of different faces, so that the screws are at an angle to one another. So here's that custom padeye so far. It mounts to both the vertical rear of the centreboard case as well as the sloping part, and will be held in by half a dozen #8 screws:

After welding with oxy-acetylene and CIG "Com-weld" filler, it looks really ghastly. I'm calling this piece "snot on bronze".

The below picture shows it mostly finished in-situ, poking up at the top of the aft end of the centreboard case - note the angle isn't 90 degrees (are they ever?).

I'm probably 70 percent of the way through the finish work. I've got to cut down to the bottom of some pits and polish it properly. Even so, from the regulation ten feet I reckon it looks okay.

Sunday, 29 November 2015

Last coaming piece.

Today I put the very last coaming piece on the boat. Now that I think of it, it's also the last piece of plywood. All subsequent bits of wood (spars, rudder) will be solid.

The second layer of coaming progressed very slowly, as I needed lots and lots of clamps for each piece. While waiting for pieces to set up I shaped other areas of the coaming and made some mounts for my nice bronze row locks from Jarrah.

This was fun, as they're a complex shape (practically no 90 degree angles here) and necessitated lots of delicate plane work.

They're held down with two #10 x 50mm screws from under the deck, plus epoxy. When I put the rowlocks in, there's four #8 x 25mm screws through the coaming into these blocks, plus an additional #8 x 38mm screw from on-top. The rowlocks are thus very solidly located to the boat.

The angles are rounded out and bum friendly, and I've raised the rowlocks by about 8mm from our initial test with Perry pretending to row. I think the rowing ergonomics should be reasonably good. It's still a big (wide) boat to row, but I reckon I've done everything I can.

Doing the final shaping on the coaming is easy on top, as there's plenty of room to plane and my Stanley no. 4 and spokeshave work really well. Alas it's rather harder underneath, as there's not enough space between cockpit seats and coaming to get the no. 4 in. I very nearly pulled the pin on a low angle block plane, but figured for this job a simple piece of coarse emery on a wooden block will suffice. That leaves me a little more money for the enormous pile of blocks that I now have to buy.

Wednesday, 25 November 2015

Coamings and thinking about rigging

I've been on holidays from work for three weeks, and it's been an incredibly productive time for me. After painting the interior I went straight to work on the coamings. Once the coamings are done I can paint them and paint the decks and timber-work, and the hull is then essentially complete, leaving a much shorter list of things that need to be finished before launch.

Here's the first piece of coaming being glued on. I started with the hardest bit, as I figured this was where I was likely to run into trouble. I used 4mm ply, and oriented it so that the central ply had its grain running along the boat. This made it much easier to bend, which was necessary because that's a really tight radius bend around the front of the cockpit.

After this piece, I just kept putting pieces on until the cockpit was filled in. Then I went around for another layer. The second layer needs many more clamps than the first, as the glue area is much larger. Here's an example piece going into place.

Now I'm starting to turn my attention to all the little detail bits. One of the questions that I'm mulling over at the moment is of how to attach my main sheet. The only other Navigator sloop that I've seen any detail of is Dauntless, which goes for a high-zoot factor traveller across the transom. Wayfarers generally opt for a bridle across the transom, and I'm leaning towards this arrangement, as is seems simple and straightforward.

So now the options of how to locate the ends of the bridle. The photo below shows some of the options I'm mulling:

The join in the ply that the eyes are sitting on has a 19mm square Tassie Oak stringer underneath it. At a minimum, I could simply put a pair of #8 by 25mm countersunk screws into this stringer to hold the smaller eye down. For something stronger, I could make a bronze plate up to go under the deck, and use #8 bolts, sandwiching the deck in a similar fashion to what I did with the chainplates. Or I could do the same with the larger four-bolt eye. I suspect the last option is incredible overkill. Indeed I'm suspecting all three options are overkill, but I've sailed on a boat (albeit a 26' one with a cabin-top mounted traveller) watching the traveller coming off the top of the cabin in gusts...

Thursday, 19 November 2015

Finished painting the interior

I've had an absolute blast over the last few days, now that the last coat on the inside of Elena has set up, doing little bits and pieces and finishing bits on the inside off.

The paint is International "Toplac" single component polyurethane. I've got a really good relationship going with a paint supplier at the fishing wharf here in Geraldton, who happily added some tint to their "snow white" to make more of an off-white or ivory colour.

It looked very white when I was applying it, and I was starting to worry that I should have asked for more tint. Once I pulled out the actual white hatches to compare it to, I was really thrilled with the colour. I certainly wouldn't want it any darker.

Here's a photo showing a general overview of the front of the cockpit. The little bronze plate that's visible on the aft face of the front thwart is where I'll be putting an antenna connector for the VHF radio. Every corner that's visible here had a fillet of epoxy with filler, which took ages to get nice and smooth. The little hole at the base of the thwart is drainage for the front of the boat. The observant will note that the area inside the forward hatch is painted a different colour to the rest of the boat, and they'd be right. I painted this with aquacote, which is a water-based polyurethane that set up rather too quickly for my liking.

This detail shows the centreboard pivot, all nicely finished and capped off. Under here is an o-ring to keep the ocean out of the boat.

There are slots under where the coaming will go, to allow me to run a lead to my radio at the back of the cockpit, so I can use the radio without leaving the tiller. Also seen here are the spots under the cockpit seats for storage of gear that needs to stay dry. The little rings will eventually support a removable and adjustable rowing stretcher and raised platform for sleeping. I used Sikaflex 291 as bedding compound under the hatches.

Tuesday, 17 November 2015

Thinking about a trailer.

I'm starting to get a bit more specific about what I want in a trailer. This is bad, because it means I'm up for buying something pretty expensive or else building one. I'm starting to favour building one, as the one quote for a half-way reasonable trailer I got from a mob down in Perth was an astonishing $3800. I guess they figured they'd try one on.

I'm rather liking the idea of a "break back" trailer. Additionally I could build a nice long draw-bar, and organise it so I could remove much of the front of the draw-bar when the boat is in the garage, minimising length (which is important, as my garage is only barely longer than Elena).

Here's a quick sketch of what I'm thinking of. Four bits of 65x35mm RHS, one bit of 65mm SHS, and the rest is bits from BCF or from the local car wreckers. There's a bit of welding involved, but It's about bloody time I bought myself a welder.