CDR_Ret

Terry, Have you tried looking on www.hathitrust.org/ {online books) search international marine engineering for the years you are interested in. I have a set that spans 1896-1906 and have seen many naphtha launches some with drawings.

Evidently this particular "boat" topic has never been brought up in this forum.
 
Late in the 1800s when builders were toying around with more compact and energetic sources of energy for propulsion, they developed the naphtha engine, which used volatile fuels produced by the distillation of petroleum to either heat water to steam or, eventually, to produce propulsion by internal combustion. It was the precursor to gasoline engines.
 
Between the 1890s and around 1905, small- to medium-sized vessels called naphtha launches were very popular with the boating public, and thousands were built by companies such as the Gas Engine and Power Company for recreational and commercial use.
 
Now to my question:
 
The brigantine Galilee, in which my grandfather sailed, was conducting magnetic surveys of the Pacific Ocean between 1905 and 1908. Because the vessel was not entirely nonmagnetic due to the hundreds of iron fasteners in her hull and some steel and iron rigging components that couldn't be removed, she produced a small by measurable magnetic characteristic that had to be accounted for in the sensitive measurements and calculations of the earth's magnetic field. This was accomplished by measuring the earth's field elements on various courses at sea, and turning the ship in harbors at the ports she visited. The former was done using wind, sails, and rudder. But the latter was very difficult without outside assistance, and very time consuming.
 
To deal with this problem, on her second and third cruises, she was equipped with her very own—naphtha (or more probably, gasoline) launch—carried in beefed up davits off her stern. Sadly, I don't have very many photos of the launch to finalize my reconstruction of the plans for the ship.
 

Courtesy Department of Terrestrial Magnetism, Carnegie Institution, Washington, DC
 
This is an approximation of what I can see:
 

 
According to various sources, the boat is described as a plumb-bow fantail launch. My best approximation of its length is about 20–22 feet long. Its depth is about 4 to 5 feet. I have no idea of the beam, since there are no views of this detail. I don't even know if there is a transom or if the stern is elliptical or canoe-shaped, like many of the available plans of this type of vessel show.
 
If anyone knows of sources that show either this particular type of launch or one similar to it, I'd appreciate direction to them. I've already checked out most of the diagrams available on the web, but if there is one that looks close to this boat, and in particular shows the plan and body views, those would be of great help.
 
Terry

Evidently this particular "boat" topic has never been brought up in this forum.
 
Late in the 1800s when builders were toying around with more compact and energetic sources of energy for propulsion, they developed the naphtha engine, which used volatile fuels produced by the distillation of petroleum to either heat water to steam or, eventually, to produce propulsion by internal combustion. It was the precursor to gasoline engines.
 
Between the 1890s and around 1905, small- to medium-sized vessels called naphtha launches were very popular with the boating public, and thousands were built by companies such as the Gas Engine and Power Company for recreational and commercial use.
 
Now to my question:
 
The brigantine Galilee, in which my grandfather sailed, was conducting magnetic surveys of the Pacific Ocean between 1905 and 1908. Because the vessel was not entirely nonmagnetic due to the hundreds of iron fasteners in her hull and some steel and iron rigging components that couldn't be removed, she produced a small by measurable magnetic characteristic that had to be accounted for in the sensitive measurements and calculations of the earth's magnetic field. This was accomplished by measuring the earth's field elements on various courses at sea, and turning the ship in harbors at the ports she visited. The former was done using wind, sails, and rudder. But the latter was very difficult without outside assistance, and very time consuming.
 
To deal with this problem, on her second and third cruises, she was equipped with her very own—naphtha (or more probably, gasoline) launch—carried in beefed up davits off her stern. Sadly, I don't have very many photos of the launch to finalize my reconstruction of the plans for the ship.
 

Courtesy Department of Terrestrial Magnetism, Carnegie Institution, Washington, DC
 
This is an approximation of what I can see:
 

 
According to various sources, the boat is described as a plumb-bow fantail launch. My best approximation of its length is about 20–22 feet long. Its depth is about 4 to 5 feet. I have no idea of the beam, since there are no views of this detail. I don't even know if there is a transom or if the stern is elliptical or canoe-shaped, like many of the available plans of this type of vessel show.
 
If anyone knows of sources that show either this particular type of launch or one similar to it, I'd appreciate direction to them. I've already checked out most of the diagrams available on the web, but if there is one that looks close to this boat, and in particular shows the plan and body views, those would be of great help.
 
Terry

Evidently this particular "boat" topic has never been brought up in this forum.
 
Late in the 1800s when builders were toying around with more compact and energetic sources of energy for propulsion, they developed the naphtha engine, which used volatile fuels produced by the distillation of petroleum to either heat water to steam or, eventually, to produce propulsion by internal combustion. It was the precursor to gasoline engines.
 
Between the 1890s and around 1905, small- to medium-sized vessels called naphtha launches were very popular with the boating public, and thousands were built by companies such as the Gas Engine and Power Company for recreational and commercial use.
 
Now to my question:
 
The brigantine Galilee, in which my grandfather sailed, was conducting magnetic surveys of the Pacific Ocean between 1905 and 1908. Because the vessel was not entirely nonmagnetic due to the hundreds of iron fasteners in her hull and some steel and iron rigging components that couldn't be removed, she produced a small by measurable magnetic characteristic that had to be accounted for in the sensitive measurements and calculations of the earth's magnetic field. This was accomplished by measuring the earth's field elements on various courses at sea, and turning the ship in harbors at the ports she visited. The former was done using wind, sails, and rudder. But the latter was very difficult without outside assistance, and very time consuming.
 
To deal with this problem, on her second and third cruises, she was equipped with her very own—naphtha (or more probably, gasoline) launch—carried in beefed up davits off her stern. Sadly, I don't have very many photos of the launch to finalize my reconstruction of the plans for the ship.
 

Courtesy Department of Terrestrial Magnetism, Carnegie Institution, Washington, DC
 
This is an approximation of what I can see:
 

 
According to various sources, the boat is described as a plumb-bow fantail launch. My best approximation of its length is about 20–22 feet long. Its depth is about 4 to 5 feet. I have no idea of the beam, since there are no views of this detail. I don't even know if there is a transom or if the stern is elliptical or canoe-shaped, like many of the available plans of this type of vessel show.
 
If anyone knows of sources that show either this particular type of launch or one similar to it, I'd appreciate direction to them. I've already checked out most of the diagrams available on the web, but if there is one that looks close to this boat, and in particular shows the plan and body views, those would be of great help.
 
Terry

I have been devoting a lot of time to DELFTship in the past few weeks while "social distancing."
 
This is the hull of the 1891 brigantine Galilee, in which my grandfather sailed between 1906–08. The hull lines are based on the G.C. Berger plans available from the Smithsonian HAAMS program. They need a lot of work to make them usable, which is why I used DELFTship.

The interior views of that old ship are really amazing!
 
Terry

With regards to DELFTship, I am using the program to determine the true deck line along the bulwark of Galilee's hull plan reconstruction. I thought it might be useful for those trying to learn the program if I did a mini-tutorial as I worked on the problem. The first post of the tutorial starts here. I'm including lots of discussion on program features that are really glossed over or ignored in the program manual.
 
Please let me know what you think of the presentation and suggest anything that could be improved upon.
 
Thanks!
 
Terry

It is really a pleasure seeing that Rene's lessons did lead to beautiful results.
Well done!

I have been devoting a lot of time to DELFTship in the past few weeks while "social distancing."
 
This is the hull of the 1891 brigantine Galilee, in which my grandfather sailed between 1906–08. The hull lines are based on the G.C. Berger plans available from the Smithsonian HAAMS program. They need a lot of work to make them usable, which is why I used DELFTship.

The interior views of that old ship are really amazing!
 
Terry

Well, I've spent some of my time during the past two weeks self-isolating from coronavirus exposure to sort through the rabbet question.
 
After taking a look at the DELFTship model as I left it last Fall, I realized that there was very poor fidelity between the model and the original Berger lines plan. So I basically decided to work over the model lines again to attempt as much as possible to approach the original lines. After several iterations, I realized that the lines in the halfbreadth, elevation, and body plans simply were not compatible, so I did  the best I could to at least approach the hull shape that produced fared station, waterline, and buttock curves. Considering that I basically had to build the aft end and transom from scratch using reference photos and the real ship had a 5-inch hog, the results were pretty gratifying.
 
As a result of this work, I am posting several other new items pertaining to the Galilee plans elsewhere in the forums.
 
All that to say that I needed a fairly stable set of station lines so I could determine the angle of the garboard strake to identify the rabbet lines. The results are shown below. As we discussed, the back rabbet line curves upward along the middle run of the keel and becomes nearly flat at the ends before reaching the stem and sternpost. The thickness of the strake is full thickness at 6 inches while it thins down to 3 inches, which is the hull planking thickness, at the ends of the hull.
 
Terry

 

Well, I've spent some of my time during the past two weeks self-isolating from coronavirus exposure to sort through the rabbet question.
 
After taking a look at the DELFTship model as I left it last Fall, I realized that there was very poor fidelity between the model and the original Berger lines plan. So I basically decided to work over the model lines again to attempt as much as possible to approach the original lines. After several iterations, I realized that the lines in the halfbreadth, elevation, and body plans simply were not compatible, so I did  the best I could to at least approach the hull shape that produced fared station, waterline, and buttock curves. Considering that I basically had to build the aft end and transom from scratch using reference photos and the real ship had a 5-inch hog, the results were pretty gratifying.
 
As a result of this work, I am posting several other new items pertaining to the Galilee plans elsewhere in the forums.
 
All that to say that I needed a fairly stable set of station lines so I could determine the angle of the garboard strake to identify the rabbet lines. The results are shown below. As we discussed, the back rabbet line curves upward along the middle run of the keel and becomes nearly flat at the ends before reaching the stem and sternpost. The thickness of the strake is full thickness at 6 inches while it thins down to 3 inches, which is the hull planking thickness, at the ends of the hull.
 
Terry

 

Well, with the coronavirus panic-buying depleting all the dust masks at our local home improvement stores, I was at a standstill with some of my workshop projects. However, my  wife has been following some fabric arts forums where they are discussing making masks for hospitals to supplement those needed for non-critical care situations, so they can use the N-95-esq masks for critical care/COVID-19 cases.
 
So, she found the pattern, we selected a fabric, got the elastic bands, and I made a nose-bridge support out of a piece of copper wire.
 
The result looks like it will work fine!

 

Nice looking masks, Bob.
 
My wife says she has enough elastic for the apocalypse, which she has been collecting for decades.

we're making masks for the medical caregivers too.  But now elastic is out of stock, so we're making them with long ties that can be trimmed to length.  My daughter creates fabric print designs and contracts with a printer to produce a sampler proof cloth for the designs.  She's now cutting up the proof samplers for masks.
 
 

Well, with the coronavirus panic-buying depleting all the dust masks at our local home improvement stores, I was at a standstill with some of my workshop projects. However, my  wife has been following some fabric arts forums where they are discussing making masks for hospitals to supplement those needed for non-critical care situations, so they can use the N-95-esq masks for critical care/COVID-19 cases.
 
So, she found the pattern, we selected a fabric, got the elastic bands, and I made a nose-bridge support out of a piece of copper wire.
 
The result looks like it will work fine!

 

Well, with the coronavirus panic-buying depleting all the dust masks at our local home improvement stores, I was at a standstill with some of my workshop projects. However, my  wife has been following some fabric arts forums where they are discussing making masks for hospitals to supplement those needed for non-critical care situations, so they can use the N-95-esq masks for critical care/COVID-19 cases.
 
So, she found the pattern, we selected a fabric, got the elastic bands, and I made a nose-bridge support out of a piece of copper wire.
 
The result looks like it will work fine!

 

That looks like it will work fine. I bought a pack of N-95s about 3 weeks ago. Good thing I did too as I've been power carving basswood which is really dusty. Also I gave two to some friends who have been cleaning out an old house and a shop that were mouse infested. You can geet the Hanta virus from mouse waste. Anyway good on your wife. I see mostly women doing this around the country where they can get the material.  Bill

Well, with the coronavirus panic-buying depleting all the dust masks at our local home improvement stores, I was at a standstill with some of my workshop projects. However, my  wife has been following some fabric arts forums where they are discussing making masks for hospitals to supplement those needed for non-critical care situations, so they can use the N-95-esq masks for critical care/COVID-19 cases.
 
So, she found the pattern, we selected a fabric, got the elastic bands, and I made a nose-bridge support out of a piece of copper wire.
 
The result looks like it will work fine!

 

Well, with the coronavirus panic-buying depleting all the dust masks at our local home improvement stores, I was at a standstill with some of my workshop projects. However, my  wife has been following some fabric arts forums where they are discussing making masks for hospitals to supplement those needed for non-critical care situations, so they can use the N-95-esq masks for critical care/COVID-19 cases.
 
So, she found the pattern, we selected a fabric, got the elastic bands, and I made a nose-bridge support out of a piece of copper wire.
 
The result looks like it will work fine!

 

Living a couple of blocks away from her last resting place, I watched the tides wash over Galilee's keel for many years. I should have taken a closer look, but it's too late now. (Her transom is (was?) preserved at Ft. Mason,  Golden Gate Recreation Area, San Francisco.) 
 
I'll offer a few observations, 
 
1.   How could those DTM guys know the keel to garboard faying surface was pointed, unless they pulled the garboard, which they wouldn't have done because they had no need to do it if they were only looking to identify the fastenings. Turner's own yard built the ships he designed and he personally supervised the building. I would hazard to guess he did not draw any design details remotely close to what the DTM guys drew. His crew knew how he engineered his vessels and didn't need to be told how to lay out a garboard seam. Ergo: It's a pretty safe bet that aside from the placement of the keel bolts visible to the DTM surveyors, the rest of the drawing depicting what they couldn't see is likely some lubber's fantasy.
 
2.  No self-respecting wooden ship builder would drive keel bolts any closer to the garboard seam than they absolutely had to. That arrangement looks to me like it's sure to leak in short order. It's clear from the DTM drawing that whoever drew it didn't know shipbuilding because all of the drifts were drawn as being driven straight down. Drifts are always driven at opposing angles so as to lock the timbers together. 
 
3.  It's very hard to believe any wooden ship builder of that time, and particularly one as practical as Turner, would ever find a justification for building a "pointed" garboard and rabbet. It would be difficult and expensive work for no benefit, for all the reasons you noted. For what it's worth, this old wooden boat guy has seen more garboard seams and rabbets than he'd like to remember, "in the flesh" and on paper, and I've never, ever, see one a "pointed" one.
 
4.  With a nod to Howard I. Chapelle's tremendous contributions to the preservation of the American maritime heritage, the HAMMS lines are notorious for errors. Don't forget HAMMS was a WPA project designed to make work for unemployed architects, surveyors, photographers, and draftsmen and not all of them had specifically maritime trade skills. We can't be too hard on them, but we have to remember they are "secondary sources" and not primary historical records.
 
I'd say you'd be safe in using "common practice at the time" to "fill in the blanks" where there are gaps or "inexplicables" in the available record. Chapelle was quite forthright about doing the same in his work. Sometimes one has to extrapolate.

It seems very atypical the way it was drafted. I'd concur with Mr. Cleek. And wrestling a 6" thick plank bow and stern would be a mighty task: it would have to be tapered in thickness.

Thanks, Bob.
 
I'm in complete agreement with your assessment of the DTM draftsmen. During the field assessment, the engineers may have been able to obtain some verbal description of the hull's construction to add to what could have been visually verified from inside the hull. But trying to put all that together into dimensional drawings may have included some guesses.
 
As I noted in several posts in my Galilee thread, Berger's plans, or at least the subject, seem to predate the HAMMS project, which occurred in 1936–37. That idea may be in error. Berger's plans show her as a brigantine, but by the early-30s she was a an aging three-masted fishing schooner and had many alterations to support the fishing industry. According to her history documented in R.A. Stradford's Brigantine, Schooner, Houseboat: Journeys of the Galilee, the vessel was purchased by an ex-pat British captain named John Quinn, who with his wife used it as a houseboat, beached in the Sausalito mudflats from 1934 until the late 1950s.  
 
The Berger plans include a note thanking J. Quinn as the last owner of the Galilee (as well as Ray Bowes) for assistance in the production of the plans. However, the plans show the ship as a brigantine, so he must have used the ship-as-houseboat mainly to confirm her overall dimensions and arrangement. His plans, which are now part of the HAMMS archive (and are copies of copies of copies ...) look very similar to C.G. Davis's Rudder magazine drawings from 1899, including the erroneous transom shape.

With the ship moored and/or in the mud, I'm not sure how Berger could have validated much of the keel configuration.
 
So, I think I will do the best I can to map out the rabbet assuming a more-or-less rectangular garboard strake that tapers from 6" to 3" thick in the vicinity of the bow and stern.
 
Terry

Thanks, Bob.
 
I'm in complete agreement with your assessment of the DTM draftsmen. During the field assessment, the engineers may have been able to obtain some verbal description of the hull's construction to add to what could have been visually verified from inside the hull. But trying to put all that together into dimensional drawings may have included some guesses.
 
As I noted in several posts in my Galilee thread, Berger's plans, or at least the subject, seem to predate the HAMMS project, which occurred in 1936–37. That idea may be in error. Berger's plans show her as a brigantine, but by the early-30s she was a an aging three-masted fishing schooner and had many alterations to support the fishing industry. According to her history documented in R.A. Stradford's Brigantine, Schooner, Houseboat: Journeys of the Galilee, the vessel was purchased by an ex-pat British captain named John Quinn, who with his wife used it as a houseboat, beached in the Sausalito mudflats from 1934 until the late 1950s.  
 
The Berger plans include a note thanking J. Quinn as the last owner of the Galilee (as well as Ray Bowes) for assistance in the production of the plans. However, the plans show the ship as a brigantine, so he must have used the ship-as-houseboat mainly to confirm her overall dimensions and arrangement. His plans, which are now part of the HAMMS archive (and are copies of copies of copies ...) look very similar to C.G. Davis's Rudder magazine drawings from 1899, including the erroneous transom shape.

With the ship moored and/or in the mud, I'm not sure how Berger could have validated much of the keel configuration.
 
So, I think I will do the best I can to map out the rabbet assuming a more-or-less rectangular garboard strake that tapers from 6" to 3" thick in the vicinity of the bow and stern.
 
Terry

Hi all. After a hiatus of nearly six months, I have been able to get back to working out some of the details of Matthew Turner’s brigantine Galilee.
 
While attempting to clean up the rabbet along the keel, stem, and sternpost in DELFTship, I ran into some issues that call into question the original G.C. Berger plans I obtained from the Smithsonian. This isn't the first time this has happened. Check out my research and design log on this ship. So the following is a series of technical questions about rabbet lines and garboard strakes.
 
Let’s start with a description of the rabbet at the dead flat. The following diagram was created by the scientist-engineers at the Department of Terrestrial Magnetism, Carnegie Institution, Washington, D.C. (DTM) sometime around 1904–5, when they were planning the conversion of Galilee from a merchant ship in the Tahiti trade to a magnetic research vessel. They needed to know where all the ferrous hardware was located in the hull to figure out the magnetic constants for the ship. For that reason, they took fairly good measurements of the hull, though their drafting skills could have used some work … Note that the inner rabbet line lies at the point where the frame intersects the face of the keel. This is a key factor in the following discussion.
 
The back rabbet and rabbet as shown in the first diagram do not conform to the shape shown in many references. In most diagrams, the back rabbet line lies on the face of the frame, which intersects the rabbet at a right angle. Instead, in this diagram, the top surface of the garboard is beveled at the inner rabbet line, giving the inner edge of the garboard a point. The top surface of the garboard strake ends at the inner rabbet line, the “point” is at the back rabbet line, and the bottom corner is at the outer rabbet line. I’m not sure how the non-naval DTM engineers knew to draw the rabbet profile like this unless they obtained that detail from Matthew Turner himself.
 
According to the DTM drawing, the garboard is about 6” thick. However, the vertical dimension of the rabbet as seen in the side profile view from the outer to inner rabbet lines should vary as the angle of the frame increases or decreases along the keel. The flatter the frame, the closer the distance between the inner and outer rabbet lines should approach the thickness of the garboard. The steeper the frame (e.g., toward the bow or stern), the wider the outer to inner rabbet line distance should be. This diagram illustrates the geometry:

© Department of Terrestrial Magnetism, Carnegie Institution, Washington DC
Curiously, the Berger plans don’t indicate a significant divergence of the outer (solid) and inner (dashed) rabbet lines except at the extreme ends of the keel:

© Smithsonian Institution
Now, let’s consider the thickness of the garboard in the first diagram. As mentioned earlier, the garboard strake is 6 inches thick. The lower hull planking is 3 inches thick. This makes the garboard twice the thickness of the adjacent planking. According to Rules for the Construction and Classification of Wood Ships (ABS, 1921), garboards must have the full scantlings for at least three fifths of the length amidship. Granted these rules were promulgated thirty years after Galilee was built, they seem to agree more-or-less with other contemporary references I have found. So, if the garboard strake stays the same thickness along most of its length, the inner rabbet line is going to curve upward as the frame angle increases. Only if the garboard thins gradually as it approaches the stem and stern areas, will the inner rabbet line stay more or less parallel to the outer rabbet line.
 
Another factor is that several views of the Berger drawings show dashed lines inset at about 3 inches from the sides of the keel as shown below. These seem to indicate the depth of the back rabbet line. If the garboard strake’s thickness remains the same for most of the length of the ship as noted above, then the back rabbet line’s depth from the sides of the keel would also vary as the frame angle changes. (Another possibility is that the dashed lines show only the back rabbet line inset at the stem and stern, though they are visible in the plan view of the keel as well.)

© Smithsonian Institution
 
So, either Berger erred in drawing the inner rabbet line as a straight line for as long as he did along the keel, or the garboard changed in thickness as its angle to the keel changed to maintain that straight line. I'm in a quandary as to what the right answer is.
 
Does anyone have thoughts or critiques of this analysis?
 
A good resource for this question is this video of cutting a rabbet along the keel of a modern 150-foot wooden ship using traditional techniques. Also, check out the other links in the left margin of the video page!
 
Thanks for the assist.
 
Terry

Thanks, Bob.
 
I'm in complete agreement with your assessment of the DTM draftsmen. During the field assessment, the engineers may have been able to obtain some verbal description of the hull's construction to add to what could have been visually verified from inside the hull. But trying to put all that together into dimensional drawings may have included some guesses.
 
As I noted in several posts in my Galilee thread, Berger's plans, or at least the subject, seem to predate the HAMMS project, which occurred in 1936–37. That idea may be in error. Berger's plans show her as a brigantine, but by the early-30s she was a an aging three-masted fishing schooner and had many alterations to support the fishing industry. According to her history documented in R.A. Stradford's Brigantine, Schooner, Houseboat: Journeys of the Galilee, the vessel was purchased by an ex-pat British captain named John Quinn, who with his wife used it as a houseboat, beached in the Sausalito mudflats from 1934 until the late 1950s.  
 
The Berger plans include a note thanking J. Quinn as the last owner of the Galilee (as well as Ray Bowes) for assistance in the production of the plans. However, the plans show the ship as a brigantine, so he must have used the ship-as-houseboat mainly to confirm her overall dimensions and arrangement. His plans, which are now part of the HAMMS archive (and are copies of copies of copies ...) look very similar to C.G. Davis's Rudder magazine drawings from 1899, including the erroneous transom shape.

With the ship moored and/or in the mud, I'm not sure how Berger could have validated much of the keel configuration.
 
So, I think I will do the best I can to map out the rabbet assuming a more-or-less rectangular garboard strake that tapers from 6" to 3" thick in the vicinity of the bow and stern.
 
Terry

Hi all. After a hiatus of nearly six months, I have been able to get back to working out some of the details of Matthew Turner’s brigantine Galilee.
 
While attempting to clean up the rabbet along the keel, stem, and sternpost in DELFTship, I ran into some issues that call into question the original G.C. Berger plans I obtained from the Smithsonian. This isn't the first time this has happened. Check out my research and design log on this ship. So the following is a series of technical questions about rabbet lines and garboard strakes.
 
Let’s start with a description of the rabbet at the dead flat. The following diagram was created by the scientist-engineers at the Department of Terrestrial Magnetism, Carnegie Institution, Washington, D.C. (DTM) sometime around 1904–5, when they were planning the conversion of Galilee from a merchant ship in the Tahiti trade to a magnetic research vessel. They needed to know where all the ferrous hardware was located in the hull to figure out the magnetic constants for the ship. For that reason, they took fairly good measurements of the hull, though their drafting skills could have used some work … Note that the inner rabbet line lies at the point where the frame intersects the face of the keel. This is a key factor in the following discussion.
 
The back rabbet and rabbet as shown in the first diagram do not conform to the shape shown in many references. In most diagrams, the back rabbet line lies on the face of the frame, which intersects the rabbet at a right angle. Instead, in this diagram, the top surface of the garboard is beveled at the inner rabbet line, giving the inner edge of the garboard a point. The top surface of the garboard strake ends at the inner rabbet line, the “point” is at the back rabbet line, and the bottom corner is at the outer rabbet line. I’m not sure how the non-naval DTM engineers knew to draw the rabbet profile like this unless they obtained that detail from Matthew Turner himself.
 
According to the DTM drawing, the garboard is about 6” thick. However, the vertical dimension of the rabbet as seen in the side profile view from the outer to inner rabbet lines should vary as the angle of the frame increases or decreases along the keel. The flatter the frame, the closer the distance between the inner and outer rabbet lines should approach the thickness of the garboard. The steeper the frame (e.g., toward the bow or stern), the wider the outer to inner rabbet line distance should be. This diagram illustrates the geometry:

© Department of Terrestrial Magnetism, Carnegie Institution, Washington DC
Curiously, the Berger plans don’t indicate a significant divergence of the outer (solid) and inner (dashed) rabbet lines except at the extreme ends of the keel:

© Smithsonian Institution
Now, let’s consider the thickness of the garboard in the first diagram. As mentioned earlier, the garboard strake is 6 inches thick. The lower hull planking is 3 inches thick. This makes the garboard twice the thickness of the adjacent planking. According to Rules for the Construction and Classification of Wood Ships (ABS, 1921), garboards must have the full scantlings for at least three fifths of the length amidship. Granted these rules were promulgated thirty years after Galilee was built, they seem to agree more-or-less with other contemporary references I have found. So, if the garboard strake stays the same thickness along most of its length, the inner rabbet line is going to curve upward as the frame angle increases. Only if the garboard thins gradually as it approaches the stem and stern areas, will the inner rabbet line stay more or less parallel to the outer rabbet line.
 
Another factor is that several views of the Berger drawings show dashed lines inset at about 3 inches from the sides of the keel as shown below. These seem to indicate the depth of the back rabbet line. If the garboard strake’s thickness remains the same for most of the length of the ship as noted above, then the back rabbet line’s depth from the sides of the keel would also vary as the frame angle changes. (Another possibility is that the dashed lines show only the back rabbet line inset at the stem and stern, though they are visible in the plan view of the keel as well.)

© Smithsonian Institution
 
So, either Berger erred in drawing the inner rabbet line as a straight line for as long as he did along the keel, or the garboard changed in thickness as its angle to the keel changed to maintain that straight line. I'm in a quandary as to what the right answer is.
 
Does anyone have thoughts or critiques of this analysis?
 
A good resource for this question is this video of cutting a rabbet along the keel of a modern 150-foot wooden ship using traditional techniques. Also, check out the other links in the left margin of the video page!
 
Thanks for the assist.
 
Terry