When planking a hull, the planks are layed out in bands of strakes, with the strakes all the same width at any given frame.

Planking bands are usually marked out using battens, to make sure they flow fair with the curve of the hull. Once a band is defined, you need to determine the plank width at each frame or bulkhead. For example, if the band consists of six strakes, you need to divide the band's width at a give frame by six to determine how wide the planks should be as they cross that frame.

So much for theory. In practice, I've seen lots of refereneces to a nifty tool called a proportional divider. It's basically a double-ended compass with a movable pivot point. For a six-strake band, you'd set the pivot point so that the distance between the pair of points at one end of the dividers is one sixth the distance of the opposite pair. The tool is engineered with appropriate markings for you to set the pivot point to the desired porportions.

When I first read about this tool I thought, "Cool! I want one!" I did some Googling, and harsh reality set in ... all the proportional dividers I found cost over $100.

So ... back to the drawing board. Or, more accurately, back to the drawing program. I fired up Visio and drew a series of lines that all shared one endpoint and had the opposite endpoint the same vertical distance apart. Any vertical line through this figure would be divided into equal parts. (See attached image below.)

I printed this out and glued the ends together to form a loop. I slipped it over a flat scrap of wood with one edge sanded to form a "ruler edge". I could then slide the loop around the wood until the width of the figure at the "ruler edge" matched the distance I wanted to be divided.

Using this simple tool, I could work along the planking band and mark the correct divisions along each frame or bulkhead. Working the other way, I could mark a plank where it crossed each bulkhead, use the paper divider to transfer each desired plank width from the bulkheads to the plank, and then play "connect the dots" to define the desired plank edge.

Granted, this solution is lacking in engineering precision, but if you cut your planks a bit wide, you can test-fit and sand them until they're right. (You do that anyway, don't you?)

I also figured out that you can dispense with the wood scrap if you're careful to fold the paper loop straight across the image and not at an off angle. The paper does tend to get worn, but you can print out several on a sheet and use them up as fast as you want, for just pennies a sheet instead of a hundred bucks.

The next idea I had was to create a loop for each band and mark lines across the loop indicating each bulkhead's reference location. This way I wouldn't have to re-measure from the model each time a strake crossed a bulkhead.

You can either draw your own image or print out the one I've attached below. Give it a try and let me know how it works for you.

Maybe one day I'll be able to justify buying a proportional divider, but until then, I'll just keep on planking away.

- Tom

Attached Images

Proportional Divider.jpg (34.1 KB, 123 views)

 

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I think it is a fantastic tool. I'm just about ready to start planking away, and having this now it totally perfect timing. I'll let you know how it goes. Tom, Thanks for a great idea. Dan

 

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Thought you might have some interest in this article.

http://www.warriorgroup.org/warships/spring-2005.pdf 

Happy modeling,
Len

 

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Len,

I kinda figured my core idea was non-obvious enough not to be patented - simple geometry.

I wanted something that could calculate my plank widths directly from the model, and then transfer them directly to the stripwood. I also wanted to be sure that when taking measurments from the tool I stayed on the same line I used for the calculation. The one thing that struck me when I looked at that W-to-W article was that I would have expected lines at right angles to the reference lines, but I guess that doesn't really matter the way they're using it.

- Tom

 

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Tom, I thought this tool would be really great as a flexible plastic template. So, I decided to print it on an overhead transparency from days gone by. I copied it to a file and put several on one page. I think that is going to work out nicely. Your idea is superb. Thanks a lot. Dan

 

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