lehmann

If I may summarize Bourne's method: take the lines of the hull and build a scale model, in this case, 1/48 scale, measure the volume of water displaced by the model then multiply by 48 cubed and the density of water.
 
Do you have any indication this method was used? I suppose it is one use of half hull models.
 
I recall reading that this method is somewhat error prone, with the main problem being that the wooden model absorbs water.
 
It reminds me of another way to measure measure area: trace the shape onto paper on cardboard and weigh it. Also weigh a piece with a known area. Area of the irregular shape calculated by simple ratio.

Having done displacement calculations by hand using Simpson's rule, I can attest to the tedium and the chance of error.  The use of a planimeter (integrator) makes a world of difference.  However, as I've mentioned before, knowing the displaced volume is only the first, and easiest, part of the calculation (estimation) of the load water line: the second is the weights of the ships components (framing, planking, spars, anchor chain, etc), which could easily have a 20% error band.  A planimeter could be used with the volume calculations of frames, assuming you have drawing for each component, etc, but there's still significant uncertainty in the density of wood.  And, if you want to calculate the stability, you'll need to estimate the center of gravity of all those components as well.  With a 3D drafting application, this can now be done, but by hand it would be a nightmare, even with the Amsler intregrator.    Up until the time of building steel or aluminum hulls with 3D drafting, weights were likely estimates with revisions based on the designer's experience with similar ships.  I'll bet that even today, each component is weighed before it is added to the construction as a check on the calculations.     
 
So, in your researches, you'll only have a definitive answer if you see both the displacement and the weight calculations.  
 
The second aspect is the captain's prerogative for the amount and location of ballast, supplies, water, cargo and armament to achieve the best sailing trim, stability, profitability or defense.   However, as the weight of these items becomes large relative to the weight of the hull, the errors in hull weight become less significant in the load water line determination.  That may be a clue for your research:  what is the relative weight of the hull to the weight of these other components?  If the hull weight is a large percentage then the weight calculations are critical for both determining the water line and the success of the vessel in its intended purpose.  If the hull weight is a low percentage, then ship can be loaded until the desired water line (trim) is achieved.   In my travels through the many treatises on ship design, I don't recall seeing any hull weight calculations or even comments on it, so I would assume that, in general, the hull weight is a low percentage and the water line could be determined by the captain.  This would also remove the need to calculate displacement and allow builders supply vessels based on previous similar designs and rules of thumb.   Note that there would be a rapid evolutionary process here:  builders that supplied ships that were not successful didn't get more commissions or relegated to building traditional hulls. 
 
A third aspect for tracing the development of the mathematics of ship design would be to look at when design changed.  As calculation methods are developed to the point where the designers trust them, they will begin to push the design envelope.  In ship design, I suspect that most significant developments resulted from new knowledge in structural strength, and more recently, in hydrodynamics, but there may have been some new hull designs that were dreamed up as designers saw that they could do "what-if" calculations with some certainty that they wouldn't be judged as indulging in folly.  As happens today, the envelop is usually pushed hardest by the military, racers or some commerce where speed or endurance are critical.  
 
Bruce

Having done displacement calculations by hand using Simpson's rule, I can attest to the tedium and the chance of error.  The use of a planimeter (integrator) makes a world of difference.  However, as I've mentioned before, knowing the displaced volume is only the first, and easiest, part of the calculation (estimation) of the load water line: the second is the weights of the ships components (framing, planking, spars, anchor chain, etc), which could easily have a 20% error band.  A planimeter could be used with the volume calculations of frames, assuming you have drawing for each component, etc, but there's still significant uncertainty in the density of wood.  And, if you want to calculate the stability, you'll need to estimate the center of gravity of all those components as well.  With a 3D drafting application, this can now be done, but by hand it would be a nightmare, even with the Amsler intregrator.    Up until the time of building steel or aluminum hulls with 3D drafting, weights were likely estimates with revisions based on the designer's experience with similar ships.  I'll bet that even today, each component is weighed before it is added to the construction as a check on the calculations.     
 
So, in your researches, you'll only have a definitive answer if you see both the displacement and the weight calculations.  
 
The second aspect is the captain's prerogative for the amount and location of ballast, supplies, water, cargo and armament to achieve the best sailing trim, stability, profitability or defense.   However, as the weight of these items becomes large relative to the weight of the hull, the errors in hull weight become less significant in the load water line determination.  That may be a clue for your research:  what is the relative weight of the hull to the weight of these other components?  If the hull weight is a large percentage then the weight calculations are critical for both determining the water line and the success of the vessel in its intended purpose.  If the hull weight is a low percentage, then ship can be loaded until the desired water line (trim) is achieved.   In my travels through the many treatises on ship design, I don't recall seeing any hull weight calculations or even comments on it, so I would assume that, in general, the hull weight is a low percentage and the water line could be determined by the captain.  This would also remove the need to calculate displacement and allow builders supply vessels based on previous similar designs and rules of thumb.   Note that there would be a rapid evolutionary process here:  builders that supplied ships that were not successful didn't get more commissions or relegated to building traditional hulls. 
 
A third aspect for tracing the development of the mathematics of ship design would be to look at when design changed.  As calculation methods are developed to the point where the designers trust them, they will begin to push the design envelope.  In ship design, I suspect that most significant developments resulted from new knowledge in structural strength, and more recently, in hydrodynamics, but there may have been some new hull designs that were dreamed up as designers saw that they could do "what-if" calculations with some certainty that they wouldn't be judged as indulging in folly.  As happens today, the envelop is usually pushed hardest by the military, racers or some commerce where speed or endurance are critical.  
 
Bruce

Having done displacement calculations by hand using Simpson's rule, I can attest to the tedium and the chance of error.  The use of a planimeter (integrator) makes a world of difference.  However, as I've mentioned before, knowing the displaced volume is only the first, and easiest, part of the calculation (estimation) of the load water line: the second is the weights of the ships components (framing, planking, spars, anchor chain, etc), which could easily have a 20% error band.  A planimeter could be used with the volume calculations of frames, assuming you have drawing for each component, etc, but there's still significant uncertainty in the density of wood.  And, if you want to calculate the stability, you'll need to estimate the center of gravity of all those components as well.  With a 3D drafting application, this can now be done, but by hand it would be a nightmare, even with the Amsler intregrator.    Up until the time of building steel or aluminum hulls with 3D drafting, weights were likely estimates with revisions based on the designer's experience with similar ships.  I'll bet that even today, each component is weighed before it is added to the construction as a check on the calculations.     
 
So, in your researches, you'll only have a definitive answer if you see both the displacement and the weight calculations.  
 
The second aspect is the captain's prerogative for the amount and location of ballast, supplies, water, cargo and armament to achieve the best sailing trim, stability, profitability or defense.   However, as the weight of these items becomes large relative to the weight of the hull, the errors in hull weight become less significant in the load water line determination.  That may be a clue for your research:  what is the relative weight of the hull to the weight of these other components?  If the hull weight is a large percentage then the weight calculations are critical for both determining the water line and the success of the vessel in its intended purpose.  If the hull weight is a low percentage, then ship can be loaded until the desired water line (trim) is achieved.   In my travels through the many treatises on ship design, I don't recall seeing any hull weight calculations or even comments on it, so I would assume that, in general, the hull weight is a low percentage and the water line could be determined by the captain.  This would also remove the need to calculate displacement and allow builders supply vessels based on previous similar designs and rules of thumb.   Note that there would be a rapid evolutionary process here:  builders that supplied ships that were not successful didn't get more commissions or relegated to building traditional hulls. 
 
A third aspect for tracing the development of the mathematics of ship design would be to look at when design changed.  As calculation methods are developed to the point where the designers trust them, they will begin to push the design envelope.  In ship design, I suspect that most significant developments resulted from new knowledge in structural strength, and more recently, in hydrodynamics, but there may have been some new hull designs that were dreamed up as designers saw that they could do "what-if" calculations with some certainty that they wouldn't be judged as indulging in folly.  As happens today, the envelop is usually pushed hardest by the military, racers or some commerce where speed or endurance are critical.  
 
Bruce

I've been playing with the free version of DelftShip (www.delftship.net) for creating hull designs.  I've done quite a few designs by hand but I've never been able to see how I could create a faired hull with 2D CAD: it would be too cumbersome.  
 
As an test, I created a model of a 30 m "frigate".  Although I didn't use all the tools for fairing the lines, it only took my about three hours to create this design.  I found the tools for pushing and pulling the hull into shape reasonable intuitive.
 
I've attached some of the output files:
Lines drawing Table of waterline offsets (program can also output a point-cloud file) Hydrostatic data Resistance data - it looks like the hull speed is about 9 knots.  Perspective renderings The program can also use a table of offsets to create a model.
 
I didn't add decks, wales or ports, but the program is capable of this.  I did manage to add the keel, masts and a bowsprit, however. 
 
I'm not sure the ship modeller will find this too useful, but there is an interesting feature for laying out the panels of the develop-able surfaces for chine boats. 
 
Those who research hull design, especially how it affects speed, cargo and armament capacity, and perhaps seaworthiness, could find it useful.  I wonder how Chapelle's "Search for Speed Under Sail" would have benefited from being able to quickly do resistance analyses.
 
If anyone wants the Delftship project file, please contact me: this forum won't all me to attach it.  
FrigateResistance.pdf
FrigateHydroStatics2.pdf
FrigateHydroStatics.pdf
FrigatePerspective1.pdf
FrigatePerspective2.pdf
FrigateOffsets.txt
FrigateLines.pdf

FYI, I ordered some Proxxon tools through Home Depot online, but they cancelled the order - no reason given, but I suspect their prices haven't been revised since before the Canada/US exchange rate made the big shift last year.    Check Proxxon's site - they have sale now for many of their items, including the scroll saw
http://shop.prox-tech.com/c/bench-top-units-and-related-accessories_scroll-saw-ds-115-e  $US153.
 
Bruce

FYI, I ordered some Proxxon tools through Home Depot online, but they cancelled the order - no reason given, but I suspect their prices haven't been revised since before the Canada/US exchange rate made the big shift last year.    Check Proxxon's site - they have sale now for many of their items, including the scroll saw
http://shop.prox-tech.com/c/bench-top-units-and-related-accessories_scroll-saw-ds-115-e  $US153.
 
Bruce

I'm assuming here that your underlying question is how to use the lines drawing to build your model....
 
Each set of curves, sections, waterlines, buttock lines, (and even diagonals) could be used individually to describe a hull.  Layers of wood, of the appropriate thickness and profile, can be glued together and smoothed to form a hull.  This is basically, old-school 3D printing, where the thinner the sections, the less smoothing is needed.   You can do this in any of the three directions (if you're really good, you could even glue up wedges shaped from the diagonals!).  One professional modeler, Phillip Reed, makes his frames by stacking layers longitudinally with each layer having the thickness of the frame.  He then smooths the solid hull.  When done, he removes every second layer to get a set of evenly spaced frames ready to be attached to the keel.  
 
The other method is to build sections, which are basically the same as the frames used in construction of a full sized wooden hull if the thickness of the planking is accounted for.  As mentioned in a previous post, the location and spacing of the sections in a lines drawing are arbitrary and chosen for the convenience of the the designer, mainly to make the calculations for displacement and stability easier.  In construction, there are many more frames than there are sections.  Even for a plank-on-bulkhead model, it's a good idea to have more bulkheads than there are sections in the plans so that the planking is better supported.  To get the frame or bulkhead shapes, just add new section lines to the drawing where ever the frames are to go.  In some ships some of the frames are not square to the centerline (in the plan view), but are canted: you can work out the shape of these canted frames by just adding canted section lines and working out their shape. There are also drafting methods to get the shape of the transom.
 
So, yes, you can get a 3D shape of the hull from the drawings, but you may not want to use it directly to build your model (or real ship). However, you can extract all the shapes from the lines drawing.  
 
A few points to consider:
Since the frames have thickness and the surfaces will have to be beveled so the planks fit properly, the profile of the sawn frame has to be from the widest side of the frame (usually, the side closest to mid-ship) As mentioned above, take into account the thickness of the planking when drawing the frames.  In plank-on-bulkhead construction it is common to use two layers of planking (double-plank) to better ensure that the final planking layer is properly supported and fair (smooth). For a full ship ship, these details are worked out by on a full size drawing - and the process is termed "lofting".  
 
Bruce

I'm assuming here that your underlying question is how to use the lines drawing to build your model....
 
Each set of curves, sections, waterlines, buttock lines, (and even diagonals) could be used individually to describe a hull.  Layers of wood, of the appropriate thickness and profile, can be glued together and smoothed to form a hull.  This is basically, old-school 3D printing, where the thinner the sections, the less smoothing is needed.   You can do this in any of the three directions (if you're really good, you could even glue up wedges shaped from the diagonals!).  One professional modeler, Phillip Reed, makes his frames by stacking layers longitudinally with each layer having the thickness of the frame.  He then smooths the solid hull.  When done, he removes every second layer to get a set of evenly spaced frames ready to be attached to the keel.  
 
The other method is to build sections, which are basically the same as the frames used in construction of a full sized wooden hull if the thickness of the planking is accounted for.  As mentioned in a previous post, the location and spacing of the sections in a lines drawing are arbitrary and chosen for the convenience of the the designer, mainly to make the calculations for displacement and stability easier.  In construction, there are many more frames than there are sections.  Even for a plank-on-bulkhead model, it's a good idea to have more bulkheads than there are sections in the plans so that the planking is better supported.  To get the frame or bulkhead shapes, just add new section lines to the drawing where ever the frames are to go.  In some ships some of the frames are not square to the centerline (in the plan view), but are canted: you can work out the shape of these canted frames by just adding canted section lines and working out their shape. There are also drafting methods to get the shape of the transom.
 
So, yes, you can get a 3D shape of the hull from the drawings, but you may not want to use it directly to build your model (or real ship). However, you can extract all the shapes from the lines drawing.  
 
A few points to consider:
Since the frames have thickness and the surfaces will have to be beveled so the planks fit properly, the profile of the sawn frame has to be from the widest side of the frame (usually, the side closest to mid-ship) As mentioned above, take into account the thickness of the planking when drawing the frames.  In plank-on-bulkhead construction it is common to use two layers of planking (double-plank) to better ensure that the final planking layer is properly supported and fair (smooth). For a full ship ship, these details are worked out by on a full size drawing - and the process is termed "lofting".  
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

In wood working, hand-made joints, such as dovetail joints, are always done by making one side of the joint first, then using that part to scribe the other part.  There is no way to get a tight joint by making the two pieces independently.  Since the devil in in the details, they are:
 
1.  Whatever the profile of the joint, scarf, dovetail, miter, or a simple butt-joint, the surfaces of the joint must be exactly square to the surface of the profile. Otherwise, you may be tight on one side and have gaps on the other.  Using a file to finish joint by hand will  always end up with a convex surface and gaps on the edges.  So, have a good small square, with a light behind so you can see gaps.  For small parts there may not be a good surface to place the square, place both the piece and the square on a flat surface.  
 
2.  To help make a square cut, place the piece on a cutting board, then cut straight down, at 90 degrees to the board, with a sharp chisel.  You can use a block of wood to keep the chisel at 90 deg.  Cabinet makes us what is called a "paring chisel" for this which sharpened to 15 degree angle instead of the usual 25 degrees used on general purpose chisels.  An X-Acto chisel (#17, #18) is a good choice for model work.  The tool needs to be razor sharp, and do not take off too much in one cut - just take off shavings.  Use other tools to get the rough shape.
 
3.  With one piece made, the shape is copied to the other piece with a scribing knife, which has been sharpened on only one side of the blade so the cutting point is tight against the part you are tracing.  There is no way a pencil tracing is accurate enough.  You could use a #11 blade, but since it is sharpened on both sides there is a good chance that the scribed line will be 1/2 the blade thickness away from traced part.   A razor blade may work, but you may want to break if off to look more like a #11 so you can scribe in to corners.  Commercial scribing knives can be expensive, but Lee Valley Tools sells a reasonably priced one.  There's no reason you couldn't make your own by re-grinding a dull #11.  I've tried using scratch awls and needles for scribing, but I found they tend to follow the wood grain.   I would only use a point scriber for tracing concave curves that a flat knife couldn't follow: however, I can't think of any ship joints like this (unless you change you hobby to making jig-saw puzzles.)
 
4.   After you have roughed out the shape of the second piece to close to the line, the benefit of the scribed line comes into play.  Just hook the edge of the chisel in to the scribed line and cut straight down.  Even if your eyes can't see the line, you can feel when the chisel hooks.  In some cases, you could scribe both sides of the joint and cut from both sides.  One trick when cutting from both sides is to make the surfaces slightly hollow (concave) to ensure the edgers are tight.  Some people consider this a bit of a cheat, but it does ensure the joint line has no gap, which easily happens if the joint surfaces are evenly slightly convex.
 
After a test-fit of the joint, some paring cuts or scraping may be needed, but you will be very close to a perfect joint.  If a joint surface is convex, you can scrape it in the middle with the edge of a knife with a round profile (#10 knife).
 
If my description of the process is not clear enough, there are lots of places on the web that have good pictures.  Start at www.finewoodworking.com.   
 
Bruce

A source of linen thread is http://www.threadneedlestreet.com/in Issaqua, WA.   They have Londonderry brand line in sizes from 100/3 to 18/3 in white/grey/beige/ivory/black.  They are used to modellers and have a pdf prepared by a customer giving diameters.  

Copper and copper alloys, such as brass, can only be hardened by work hardening.  This is usually done by running a sheet between rollers, or it can be done by drawing (pulling a wire through a hole smaller than the diameter of the wire).  Hardening can also be done by beating with a hammer, but the results will be uneven, to say nothing of the resulting uneven thickness.  At some point the material becomes brittle, which may limit the amount of bending possible for your part.  In a rolling plant, the sheets get hard after a few rolls, and so, they need to be heated (tempered) to soften them so the thickness can be reduced some more.
 
Iron, is also hardenable by working, but the amount is limited.  Hardening cannot be achieved by heating and quenching (rapid cooling) unless the carbon content is greater than 0.12%.  This limit basically defines the difference between iron and steel.  To go beyond this, other elements are added, creating alloys.  On the topic of alloys, brass is an alloy of copper and zinc;  bronze, is an alloy of copper with tin, phosphorus, aluminum, nickle or silicon.  
 
Aluminum can also be hardened, but this is mostly done by precipitation or solution hardening, where the material is kept at a certain temperature for period of time.   The hardness is designated by a "T" code, as in 6061-T4, which is the most common grade of aluminum.  
 
We work in brass and copper in models because they are easy to work, easy to solder or braze, and are corrosion resistant.  We could use stainless steels (there are many grades), but they tend to be quite hard, as anyone who has tried to drill and tap a 4-40 thread in stainless knows.  Aluminum has some of the same properties of brass, but it's very hard to join, although I've seen some aluminum "solders'.   Although aluminum is corrosion resistant, it does form a soft oxide layer that comes off easily. 
 
Probably more than you wanted to know, but now that it's been emptied from my brain, I have room to learn something else....

Jay
To remove the table, loosen the two knobs that lock the module to the rear T- track; pivot the table up so it clears the saw, the slide the module to the right. Then, remove the arbour. Everything off in less than a minute. Putting back on is just the reverse. No adjustments needed.
 
Bruce

Jay
To remove the table, loosen the two knobs that lock the module to the rear T- track; pivot the table up so it clears the saw, the slide the module to the right. Then, remove the arbour. Everything off in less than a minute. Putting back on is just the reverse. No adjustments needed.
 
Bruce