TimothyB
09-11-2005, 09:05 AM
In the years I've been reading about spiling and planking, and the time I've spent talking to boatbuilding professionals, it occured to me that there was one aspect of spiling plank that was covered in only one text that I've read, and in fact all of the other texts seemed to miss this detail. Allen Taube gives a great account of it in "The Boatwright's Companion" and I thought I would put it onto the forum for Googlers to find. I was a Math major, and so this info seemed obviously correct to me .. it might not seem so to people who hadn't spent a few years with malleable shapes and 2D-3D projections.
Selection from "The Boatwright's Companion" pg 68, author Allen Taube.
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Reversing the template - transitting from the 2nd to the 3rd dimension
You all know that when trying to cut a cone out of a piece of paper you cannot simply cut out a long rectangle and bend it into the spahe of a cone. No matter how hard you try, the two dimensional flat rectangle cannot be made into a three dimensional cone. There is, however, one and only one two dimensional shape, that when cut out and bent, will form the exact shape of a three dimensional cone.
Now that you understand this concept, you'll also understand why a straight plank cannot be made to fit into an opening in a three dimensional, curved, and rounded hull. There is, however, one and only one two dimensionally shaped plank that will fit into the three dimensional opening in the hull. No tape measure in the world will be able to tell you the correct shape of that two dimensional plank. That is why a template must be made.
The important thing when fitting planks is that the inboard or inside edges of the panks must touch each other. The outside or outboard edges will have caulking bevels, so their fit is not as critical.
The template or spiling batten is placed inside the removed plank hole and secured to the frames. The marks are taken from the inboard edge of the plank above and below the hole. Because the spiling batten was marked on the outboard surface, these marks must be transferred to the other side of the template. This is done by drilling through the template to the other side with a small drill bit, holding the drill square to the template, or by hammering a small nail through the mark. Mark the word "Goodside" on the side of the template to which the marks were transferred with the drill bit to avoid confusion when transferring them off to the inboard side of the new plank. This point must be understood for it is the key to making a good template. Always remember to reverse the template!
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So, essentially, what he is saying is the spiling template is made from the inside edge of the planks surrounding the repair.. but if you just USE the template as is, you will be making a plank with those dimensions on the OUTBOARD edge, thus potentially causing lots of planing, swearing and edge setting.
Earlier in the book he talks about when he first used this method on a replanking job, having been told of it by a pro named Peter Lamb, and his joy when the plank "kind of fell into the hole and fit" because the spiling had been so perfect. :)
He goes on to posit that this method would hold true for all templates where there is any bevel involved, like floor timbers, thick bulkheads, etc.
[ 09-11-2005, 10:15 AM: Message edited by: TimothyB ]
Selection from "The Boatwright's Companion" pg 68, author Allen Taube.
--------------
Reversing the template - transitting from the 2nd to the 3rd dimension
You all know that when trying to cut a cone out of a piece of paper you cannot simply cut out a long rectangle and bend it into the spahe of a cone. No matter how hard you try, the two dimensional flat rectangle cannot be made into a three dimensional cone. There is, however, one and only one two dimensional shape, that when cut out and bent, will form the exact shape of a three dimensional cone.
Now that you understand this concept, you'll also understand why a straight plank cannot be made to fit into an opening in a three dimensional, curved, and rounded hull. There is, however, one and only one two dimensionally shaped plank that will fit into the three dimensional opening in the hull. No tape measure in the world will be able to tell you the correct shape of that two dimensional plank. That is why a template must be made.
The important thing when fitting planks is that the inboard or inside edges of the panks must touch each other. The outside or outboard edges will have caulking bevels, so their fit is not as critical.
The template or spiling batten is placed inside the removed plank hole and secured to the frames. The marks are taken from the inboard edge of the plank above and below the hole. Because the spiling batten was marked on the outboard surface, these marks must be transferred to the other side of the template. This is done by drilling through the template to the other side with a small drill bit, holding the drill square to the template, or by hammering a small nail through the mark. Mark the word "Goodside" on the side of the template to which the marks were transferred with the drill bit to avoid confusion when transferring them off to the inboard side of the new plank. This point must be understood for it is the key to making a good template. Always remember to reverse the template!
---------------
So, essentially, what he is saying is the spiling template is made from the inside edge of the planks surrounding the repair.. but if you just USE the template as is, you will be making a plank with those dimensions on the OUTBOARD edge, thus potentially causing lots of planing, swearing and edge setting.
Earlier in the book he talks about when he first used this method on a replanking job, having been told of it by a pro named Peter Lamb, and his joy when the plank "kind of fell into the hole and fit" because the spiling had been so perfect. :)
He goes on to posit that this method would hold true for all templates where there is any bevel involved, like floor timbers, thick bulkheads, etc.
[ 09-11-2005, 10:15 AM: Message edited by: TimothyB ]