Saturday, 16 February 2013

Planking thickness

I've been procrastinating about the next step in the build - subtracting the plank thickness from lines of the moulds (I can procrastinate about anything). Kopanycia has two suggestions.
I'm not keen on either.
My father suggested a third solution which is much more elegant and I'm giving it a go.
The planking is supposed to be 11/32" (Dear Mr. Gartiside, Could you not just have made it 3/8"?). I'm struggling to believe I'll be able to buy the stock in such a specific dimension but I may yet be surprised.
To make the moulds I need to draw a line exactly 11/32' inside the lofted lines for each station. Dad suggested I make a cylinder of wood twice the thickness of the planking and drill a hole through the middle the width of a pencil. Then I can put the batten used to draw the station lines back using the original nail holes and run the pencil round the inside of it. The spacer will ensure that the pencil line is exactly 11/32 away from the batten.
UntitledI started by breaking a pencil in half and turning it down to the thickness of the drill bit I planned to use for the hole through the spacer. UntitledI didn't have a cylindrical pencil handy and anyway pencils appear not to come in the same sizes as drill bits (Dear pencil manufacturer, I think you're overlooking a yawning gap in the market here).
UntitledWith the pencil cylindrical and precisely 7mm thick I turned my attention to an offcut of ash I had from an old project. UntitledI turned this down to 11/32' using a roughing gouge, followed by a parting tool and hook gate. Once I'd sawn off a short length of the cylinder I then used the conical hole the lathe's dead centre leaves to centre the drill bit to make the hole for the pencil.
I was patting on myself on the back at this point. Little more than an hour of gentle work, interrupted by a leisurely lunch, and I was a small step further along. Then I tested it. I won't share the results but if you're familiar with the gently rolling hills of South Downs you can imagine them for yourself. The hole I drilled was fractionally off centre. Barely enough to see if you looked for it. However I'd turned the pencil a shade smaller than the hole in order to allow the spacer to roll around it. As it rolled it doubled the error. Untitled
I changed my approach. For the next model the hole would be a snug fit and I would centre it much more accurately. I used a spindle I knew to be square, marked the centre and then used a dowelling gauge to make sure I was exactly in the middle when I drilled the hole. The conical dead centre of the lathe would be self-centre and ensure that as I turned the piece it would be accurate.
UntitledSequence is everything.
Amid the resharpening of tools and the mountain of chips created I didn't take any pictures of the turning but here is result leaning casually against a dinner plate which served as the test batten to see if the wonder-gauge would produce a fair curve.
Judge for yourself.

Sunday, 2 December 2012

On old vices, new media and timeless techniques.

Chris Schwarz, owner of Lost Art Press and Editor-at-large of Popular Woodworking magazine, has a bit of a thing for leg vices. Though he calls them vises. It's a 'murican thing.
Last night after a lovely day out with our nephew in Greenwich I sent Chris a picture of the carpenter's vice we saw on the Cutty Sark.
This morning it's in a blog post on Popular Woodworking's website.
It used to take that vice weeks to cross the Atlantic, now it's dashing back and forth shaking its unusual guide mechanism across the world.
Cutty SarkIt's such a bad picture I'm not even going to post it here but he insisted on giving a credit. It's nice to be able to help someone from whom I've learnt so much. I will, however post some photos of the ship. Which is amazing. I don't really like expensive restorations of rotting hulks that sit in dry dock and gather dust; boats should sail. The Cutty Sark exhibition is, however, astonishing. Not least because the boat seems to float over the heads of the people sitting in the cafe.
It's beautiful, educational and a masterpiece of engineering. Twice.
The restorers (or preservers I should say, since the ship won't work in its intended function) have tried to use a lot of the original material. Where they needed to add material they've highlighted it. Original steel frames are white, new steel reinforcement is grey.  It's less obvious in the wood work. Cutty SarkMuch of the bright work is original and each restoration has added its own set of dutchmen, or patches, let in to the original, massive timbers. This has created a wonderful palimpsest that is testament to the longevity of our domestic hardwoods, the skill of the craftsmen and women who worked on the ship and the potential of wooden vessels to be maintained and repaired.
And that brings me back to the purpose of the blog: building a wooden boat. Little progress to report, I'm afraid. I'm building a bench at the moment. Chris Schwarz in one of his two (how much is there to say?) books on building workbenches says that a bench should have neither an apron nor a tool tray. Mine will have both. But then he also says "Disobey me!" so I've taken him at his word. I'm chopping mortices for the legs at the moment. Steve Branam has an excellent guide to building this bench, better even than Roy Underhill's original description, so I won't be posting it here - it's already done.

Cutty Sark

Sunday, 2 September 2012

And relax...

The last job to do before taking up the lofting boards was to develop the stem sections. This makes for the most fabulously confused drawing:

All that just to find out at what angle the planking meets the stem.
I've cut all the boards into manageable pieces and got rid of the excess. I don't need the diagonals anymore but am loathe to skip  them. The transom, stem and body plan now take pride of place in the study. Over the next few months I'll draw in the reduction for planking and make plywood templates for the moulds.
The pace will slacken again as GCSEs and A Levels take priority in the new school year but the thought of cutting the transom and carving the boat's name will keep me coming back to the loftings.

Thursday, 30 August 2012

Lots of lofting

The despised kneepads are gone. The lovely new, gel-filled, velcro-on kneepads are staying. I had help with the lofting: Dad popped down for the day. He wore the old ones for five minutes and threw in the towel. I threw them in the bin.
With his help and a looming deadline I'm making very good progress. The body plan went in very quickly, the half-breadths went down fair and the only points we could find that didn't look right were my plotting mistakes, not from the table of offsets. This photograph makes me very happy: a fair diagonal with no need to adjust any points.

This means that all the lines in the body plan will work.
I've adjusted the colours in the photo to emphasise the red. Often builders will set out the diagonals in a different area of the lofting board from the half-breadths to avoid confusion. A different colour also sets them apart.
It's a testament to Paul Gartside's design and drafting that this all worked so well. I've read detailed explanations about how to adjust points in each of the different views of the lines constantly chasing one's tail around the lofting board until all lines are fair. We didn't have to do any of that. The lines as drawn in the body plan are fair in the profile view, the half-breadths and the diagonals. Time will tell if the boat looks right.
I spent a devil of a lot of time on my hands and knees peering at increasingly faint pencil lines. I won't miss this and am looking forward to working upright for a while.
The last job left before I take up the boards is to develop the stem sections. The inner and outer faces of the transom are developed and looking good, the sections for the keel are drawn and I have finished the bevel board which means I could actually lay down the keel!
In the photo to the right you can see the keel sections. Kopanycia recommends drawing these on the body plan but says that because of the number of lines on top each other it will become "confused". My solution was to lay tracing paper over the body plan and then draw them in. It's not the drawings I want, so much as the measurements, so I can happily bin them but some how I can't bring myself to so inevitably they'll kick around the study until long after the boat is built.

A couple of things have vexed me.
Yesterday I set out to draw in the crown of the transom and discovered that my trammel beam was an inch short. At least that's how it appeared. I brought a piece a couple of feet longer from home but it was still too short! I taped the two beams together and that extra inch actually needed about three feet. In fact the end of the trammel had to be off the board to get the proper sweep from the crown to the edge of the transom.
What is the poor book I've chosen to impale with trammel point? It was the first thing that came to hand at the right height. Stabbing compass holes in classical texts takes me back to my own childhood. I like to think Odysseus would be happy that it's been scarred in an effort to bring a boat to life. I'm not sure the Gartside #127 would have got him back to Ithica but it might have helped him escape from Calypso.

I'm following Kopanycia's instructions closely but sometimes he leaves me wondering. When drawing out the keel sections I've been recording the measurements specified in the bevel board. Most of these measurements are taken from the outside of the keel, the bottom of the hog or apron or the top of the keel. However measurement A, which tells me where the ghostline/apex line/call-it-what-you-will is measured from the centreline, not the outside of the keel. This seems daft to me. Why not measure it from the outside of the keel which is surely going to be the surface I'll want to register my marking gauge or square from?
It's a small point but seems to ignore the purpose of lofting: to build a boat.

Thursday, 16 August 2012

There may be trouble ahead

I need better kneepads. And knees. A better pair of eyes wouldn't go amiss either.
I've spent the day dancing around my lofting floor in on oddly contorted waltz.

Fair's fair
Today I finished the lofting grid and set out the profile lines. I can now see exactly how big (small) the boat will be. 10 feet really is a very small boat. The next time I put this much love into something I'll want more to show for it.

As I loft some of the skill of the designer becomes apparent.

The book I'm using explains in details how to loft a keel that changes in width over the length of the boat. Gartside's dinghy has 1 1/2' keel all the way along. Much easier to loft and then to build. Similarly he makes the stem and transom far easier to draw and build than they mights be yet achieves a really pretty shape.

However some of the niceties of the process still puzzle me. After the profile lines I'm supposed to set out the rabbet line. No problem at the stem: Gartside gives loads of measurements for that. At the keel however the table of offsets reads "Follows top of keel" for the rabbet. No problem - a look at the construction drawing shows that the rabbet line is one plank width below the top of the keel. However because the planking meets the keel at an angle which changes over its length the rabbet line is not a measurable and consistent distance down from the top of the keel. In order to plot it on the lofting I have to "develop" it from the lofting. But I haven't drawn the body plan lines which will tell me the angles yet. It's a bit of a catch 22/32.

I need the position of the rabbet because I'm supposed to plot it into other views.

No matter, while there's sunshine, and music....

Wednesday, 15 August 2012

Lofting in anger

After a seven month hiatus there's finally something to show.
Lofting board
Not a lot, I admit and it took a surprising amount of work to get this far. The best part of a day to get the MDF boards in and nail them down, then paint them white.
Lofting tools
The tools, from left to right:

Carpenter's square - hardly used for this
Chalk line and blue chalk to establish the datum
Trammel beam, pencil and trammel heads to help draw right angles
Rule or Ruler
Large pair of compasses
Hammer for putting nails on the points to spring the lofting battens around
Kneepads  - rubbish ones
iPad with plans and table of offsets
Book to tell me how to do it.
In the background - lofting battens

This represents a step forward and a commitment: I only have two and a half weeks before I have to take it all away. I'm using a room in the school I work in and in September term starts.
I work best with a deadline!
A grid tomorrow.

Sunday, 15 January 2012

Boat of the week #10

Seen at the London Boat Show.

Stirling 9' clinker dinghy Stirling 9' clinker dinghyA brand new Stirling and Son 9' clinker dinghy built by Will Stirling over the last 7 days. I left my visit to the boat show until nearly the end hoping to see Will finishing the planking. It seems he was much too quick for me! He wasn't even there when I visited the stand so I just took photographs and inspiration. The boat is timbered out and a stringer riser installed for the thwarts (I must find the name for this). This boat, and the gorgeous 14' sailing dinghy next to it, were rare treats at the boat show this year. Despite the economic crisis the show was once again dominated by enormous plastic motor boats. It's been a while since I went to the London show and it will be a few years until I go again. More power to the Stirlings' elbows.

Stirling 9' clinker dinghy