Monday, September 3, 2018

Casting a set of drafting whales

I have earlier expressed my interest in building a boat on this blog, and I have slowly gathered information from books, blogs, etc. on the process of doing so.
I even purchased a set of drawings for a small lapstrake tender (the "irreducible" by Weston Farmer) and believe it or not - I milled some larch for the project a couple of years ago, so it would be ready whenever I was.

Before building a boat, you are supposed to loft the plans, which is a fancy expression for enlarging the drawings to full size on e.g. a piece of paper.
Boat drawings come with something called a "table of offsets". These represent positions in a coordinate system, and then once all are plotted you connect those dots and that should give the finished plans of the boat.
There is a small but important thing to notice about this dot connecting business though. The lines are not straight lines. So you need a flexible batten to help you draw that curve. Furthermore, the curve is not the same all along its length, so you will need something to hold the batten in place at various points while you adjust it, and then finally you can draw the line.
Those things are known as drafting whales. (drafting ducks, lofting ducks or lofting whales are other names for them).

For a couple of years I have regularly fantasized about casting a set of those. But I wasn't sure how to make a mold that would give a really nice result without trying to learn sand casting, and I didn't want to spend an enormous time on achieving anew skill for this.
A thing that kept holding me back was that I had the idea that those whales had to look really nice. In a way this suddenly became vital for the positive outcome of the planned boat building adventure.

I mean how could I ever present a boat that I had built unless the drafting whales used were perfect? Probably the majority of people who would ever see the boat would immediately demand to see the drafting whales I had used for lofting the plans!
It wouldn't matter if the boat was pretty and tight etc. because clearly those whales were the most important part of it all. Actually the reason why people build boats was probably so they could use their drafting whales.

Finally this time while at home I managed to get a grip on reality, and consider that maybe people wouldn't care if I had used a heavy stone, an old flywheel, a lead ingot or a horse shoe instead of a perfect whale when I laid out the lines. So maybe it would be OK to cast some even if they ended up less than perfect.
It was a daunting thought!

So somehow at a quarter past nine in the evening, I headed into the shop determined to try to make a wooden mold.

A piece of larch was split in the middle on the table saw,  and I quickly sketched the profile of a fat little whale on one side of it. On the adjacent side I sketched the outline as seen from below.
That didn't take long.

Finding a sharp gouge and removing some material was also very fast. In very little time, I suddenly had half a mold.
I held the two sides of the mold together, and traced the whale profile from the first mold to the second piece of wood.
Removing the wood was just as quick, and in just a bit more than an hour I ended up with a decent mold. I couldn't believe that it had taken me several years to gather the courage to do it.

The next day I melted some lead from old tire weights and some sheet lead that I had lying around.
A 3" nail was bent and inserted in the mold. The two parts were clamped together in the vise, and I poured the lead in.

The first whale casting caused a bit of bubbles, because of all the gas that would escape from the charring of the sides of the mold.
The next casting was perfect until I opened the mold too soon.. It broke in two.

After getting an idea of the solidifying time, I ended up making 10 whales. In the end the mold became more and more charred, so the whales started getting a larger and larger back fin.
But it will be no problem to remove this with an ordinary knife.
I plan on painting the whales after removing the surplus lead from them. But that will happen at some point while I am at home.

First half of the mold.


Mold clamped in the vise.

Filled with molted lead (now solidified)

The first whale is the one with a bit of color.
Notice how the back fin gets bigger.


8 comments:

  1. Excellent piece of humor. It reminds me the style of Jerome K. Jerome in "Three Men in a Boat (To Say Nothing of the Dog)".
    The whales are nice too. Those avoid putting nails in the living room wood flooring ;-)
    Sylvain

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    1. Hi Sylvain

      Thanks a lot for the nice comment.

      I suppose that I could loft in the "entrance hall" of the house. The floor there is really old and have wormholes in it. So no one would think about it if there were a couple of more small holes. I am not sure if I can fit the roll of paper in there though..
      But the living room floor using nails would probably be a really bad idea :-)

      The Barnsley table would have been great for lofting, but I only cast the whales after my friend had picked it up, so I guess that I'll have to use a floor somewhere.

      It is a good thing that the children are so old that you can talk a little bit of sense into them. It mighte be difficult to explain to a toddler why it is OK for dad to draw something on the floor when it is not OK for them to do it..

      Brgds
      Jonas

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  2. They look cute. I wonder if a different species of wood would hold up any better? Elm is such a nice wood.

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    1. Hi Brian.
      Thanks, I think that maybe elm would hold up better, but it would also be a little harder to carve out the whale shape.

      But now that I have got the whales I could maybe make an open sand casting using one of them as a pattern.

      But since I am only planning on making a small boat I don't think that I'll need more than 10.

      I suppose that I could make a couple of nice transport crates for them.

      Brgds
      Jonas

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  3. I think I need to see these weights in use to fully understand their function. Onward, sir. The seas await your capable craft.

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    1. Hi Mitchell

      I found this picture that shows a bunch of whales in action:
      https://www.google.no/search?q=drafting+whales&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwi_m82b66LdAhUDVywKHXVQDKwQsAR6BAgGEAE&biw=1920&bih=943#imgdii=hqAh_eE3IFpnMM:&imgrc=-6OGIRAyF3l7yM:

      I am afraid that the sea will have to wait a bit longer though, there is still a bit of way left before I am "floating".

      Best regards
      Jonas

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  4. That was fun to read, thanks. Had no idea what you were talking about until at least halfway through, and even then it came slowly, like a good mystery. I can see why you'd like for them to look good, they'll probably adorn your shop for the rest of your life. They already look good to me.

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    1. Hi Jeff.

      Thanks for the nice comment.
      The sad part is that it is true that I spent so much time contemplating how to make those whales.
      If you try to search for drafting whales or drafting ducks, some really nice pieces show up.
      One guy in a boat forum has a picture of probably 20 units painted as different ducks' heads. Male and female ducks alike. they are nothing short of impressive.

      I am "afraid" that they will see very little regular use. So I think that I will make a storage crate for them. But I guess that it couldn't hurt to keep one on display just as a conversation piece.

      Brgds
      Jonas

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