Jaager

This does not seem to be a hostile and defensive situation.  There is no obvious owner who is being protective.   I think asking for forgiveness for breaching copyright after publishing this, rather than asking permission before hand,  is the more efficient and productive course.  
In the fantasy situation where there is an actual copyright holder for this document,  it could smoke them out.  This occurring if  the probably 130+ year old owner actually cares.   This present stance is a pointless gesture to make an absolute statement.   It would be a better statement to add a footnote.  Just explain that we are willing to remove the document if the author comes forward and requests it.

The wise and economical way would be to wait until you get to a point where you need a tool and then buy the one that balances quality with how much you will use it in the future. 
Better for you would be to see if and how firmly the hook gets set with your interest in this hobby.   It has a unique advantage of being bounded enough not to be over whelming but broad enough that you could never cover it all.   Starting simple also allows you to explore tools and paint that you would never use again or use if you "knew then, what you know now".
 
This is neigh on to impossible for me, because I have an obsession about being as self sufficient as possible.  But then, I do not have to answer to anyone about how much I spend and on what.
A tool obsession can get expensive if you let it.  
 
I trust that you have looked at :   For Beginners - Cautionary Tale.

The wise and economical way would be to wait until you get to a point where you need a tool and then buy the one that balances quality with how much you will use it in the future. 
Better for you would be to see if and how firmly the hook gets set with your interest in this hobby.   It has a unique advantage of being bounded enough not to be over whelming but broad enough that you could never cover it all.   Starting simple also allows you to explore tools and paint that you would never use again or use if you "knew then, what you know now".
 
This is neigh on to impossible for me, because I have an obsession about being as self sufficient as possible.  But then, I do not have to answer to anyone about how much I spend and on what.
A tool obsession can get expensive if you let it.  
 
I trust that you have looked at :   For Beginners - Cautionary Tale.

The wise and economical way would be to wait until you get to a point where you need a tool and then buy the one that balances quality with how much you will use it in the future. 
Better for you would be to see if and how firmly the hook gets set with your interest in this hobby.   It has a unique advantage of being bounded enough not to be over whelming but broad enough that you could never cover it all.   Starting simple also allows you to explore tools and paint that you would never use again or use if you "knew then, what you know now".
 
This is neigh on to impossible for me, because I have an obsession about being as self sufficient as possible.  But then, I do not have to answer to anyone about how much I spend and on what.
A tool obsession can get expensive if you let it.  
 
I trust that you have looked at :   For Beginners - Cautionary Tale.

https://www.rarewoodsusa.com/species/holly/?_product_categories=holly&_paged=2
 
Best that I can come up with is Rare Woods.
 
Holly is a small yree that does not grow all that straight.

Bill,
 
To add to your stew of options:
 
Using a drill press to drive sanding drums
The motor being in your line of sight is the major negative.  In a thickness sander function - this is not a problem.  When shaping frames with a serious bevel, it can be.
If your drill press has a large steel table - a Carter magnetic fence is a quick and dirty but not low cost help to the thicknessing function.  Fine tuning the thickness gap will be difficult and tedious though.
 
There are sleeveless sanding drums that let you use off the shelf 9 x 11 sheets.
They not only come in standard 3" high with a variety of diameter variety,  but there is an additional 3" diameter drum that is 6" high and one that is 4.5" high.  The 6" is a big help for shaping frames if you favor the larger scales.
 
(Roger has covered the following - we were typing at the same time - me very slowly)
To speculate about your present machine:
The original version used a DC motor  - the  present version switched over to an AC motor.
I have no idea about physical size of  a DC motor vs an AC motor to get the same power output.
I also do not know if AC has any advantage over DC in efficiency, size and maximum possible force.
You may wish to determine the force/power difference and not replicate a possible under powered situation.

Thanks Allan,
 
Figure 7/5  on page 189
 
It is probably just the artist did not draw the ends of the outside planking as the planks lay on the face of the frame.  I misread the caption.  7/5 are all gunports, and not the alternate under the quarterdeck/poopdeck  "windows" that I had imagined..
In any case, the linings on the sides, sill, lintel allow for the use of "veneer"  to make them.  This is much easier.  
To be a bit self serving about my choice in framing above the wale:
For a model, it sort of makes it an unnecessary effort to shift top timbers so that they precisely frame a port - if complete outside and inside planking will be used.  I compound this further by having a solid wall topside.  No spaces.  It makes an otherwise fragile zone quite strong.   An advantage of POF is that the frames make it easy to locate the gunports.  The lining means that the rough opening does not need to be "pretty".

Allen,
 
I am just too out of practice to draw .   I will use JPG and scans to try to show what I am asking about.  In doing this, I have found that there is a lot of confusing and ambiguous .......  between the contemporary models that you have provided and within Goodwin itself.
 

 
 

 
 

 
 

 
 
 

 
 
 

 
 
 

 
 
My interpretation is that old model makers, who were making models of specific ships ( as opposed to the very rare classroom instruction models )  were just as prone to use shortcuts as we later modelers for the minor parts.    This would answer why the single layer lids.  Going elaborate for 50-120 lids that few would even notice would extend the building time.
 
I wonder if the two layer tight plug ( plastic foam cooler lid type seal)  comes from  hulks.  Old survivor ships that in the late 19th century and early 20th century had become living quarters and office space could have had the gunports and lids "upgraded" to be more weather tight.    Something that a couple of generations later would be mistaken as being how the ships were when in actual service.

I did exactly what Roger suggested.  Except that I paid a woodworker with a lathe to turn my Maple drum.
I used the old NRG plans -  at the time, there was no model scale ready made alternative.
I made it 11" long with a 9" circumference-  The available media then was 9 x 11 sheets.    The diameter was OK, but I would make it 12" long
I also used / use contact cement.  It is a positive bear to undo and clean up.   I am fairly sure that Elmer's rubber cement would hold as well.  You can clean it up using your thumb and friction.
 
I enclose the motor at the bottom.  The bottom is an OK location.  the enclosed is a very bad idea.  Leave the ends open and cut a big hole in the base and raise the unit on large rubber corks for feet.
Maybe big holes in the sides.  The motor can get hot during a long session.
 
A tapered groove/ wedge cut for the leading edge can save tearing but it is tricky to do well.  
All and all,  my Byrnes machine is the much better option if you can afford it.

Bill,
I am not shilling for Jim Byrnes or anything.  I believe that quality and realistic prices should be acknowledged and praised,  with machines that match our needs.  As for budget,  I can't make any helpful guidance.
For media, I buy rolls directly from Klingspor.  They are just south of me in Tarheelia, but UPS is everywhere.   It is my thought that your general situation is not unique and the open decision points would apply to others, exploring this scratch build universe.
If you do replace, I hold a positive wish that you get a worthwhile return, should  you sell your present machine.
 
As for the Byrnes, be sure to get spare screws et al.    A small screw top plastic container,  a 1/4-1/2" thick scrap board with holes for the Allen wrenches,  heavy duty double stick tape to fix all this to the machine base deck,  and everything is to hand - as well as a place to park screws when you change media.  If you just place them on your bench,  small parts run away when you are not looking.

Bill,
I am not shilling for Jim Byrnes or anything.  I believe that quality and realistic prices should be acknowledged and praised,  with machines that match our needs.  As for budget,  I can't make any helpful guidance.
For media, I buy rolls directly from Klingspor.  They are just south of me in Tarheelia, but UPS is everywhere.   It is my thought that your general situation is not unique and the open decision points would apply to others, exploring this scratch build universe.
If you do replace, I hold a positive wish that you get a worthwhile return, should  you sell your present machine.
 
As for the Byrnes, be sure to get spare screws et al.    A small screw top plastic container,  a 1/4-1/2" thick scrap board with holes for the Allen wrenches,  heavy duty double stick tape to fix all this to the machine base deck,  and everything is to hand - as well as a place to park screws when you change media.  If you just place them on your bench,  small parts run away when you are not looking.

I tend to think in proportions, rather than absolute values in a situation like this. 
You are reinvesting about 50% of the total value in a used machine of inferior design.
For another 50% you could buy a a machine that is more reliable, better precision, and allows for a less expensive and wider variety of sanding media.

I did exactly what Roger suggested.  Except that I paid a woodworker with a lathe to turn my Maple drum.
I used the old NRG plans -  at the time, there was no model scale ready made alternative.
I made it 11" long with a 9" circumference-  The available media then was 9 x 11 sheets.    The diameter was OK, but I would make it 12" long
I also used / use contact cement.  It is a positive bear to undo and clean up.   I am fairly sure that Elmer's rubber cement would hold as well.  You can clean it up using your thumb and friction.
 
I enclose the motor at the bottom.  The bottom is an OK location.  the enclosed is a very bad idea.  Leave the ends open and cut a big hole in the base and raise the unit on large rubber corks for feet.
Maybe big holes in the sides.  The motor can get hot during a long session.
 
A tapered groove/ wedge cut for the leading edge can save tearing but it is tricky to do well.  
All and all,  my Byrnes machine is the much better option if you can afford it.

Bill,
 
I agree with Jaager.  I still don’t understand why MM would market a 12v. Machine.  If you buy the more powerful Jim Byrnes machine I believe that you will be pleased at the additional power it provides,
 
If you don’t feel that you can spend the money why not build one.  The only purchased parts in my thickness sander are a pair of pillow block bearings, belt,and pulleys.   In my case, whenever I get rid of something, I save the motor.  Also, our local landfill segregates that sort of thing and allows visitors to take stuff for free.  You might also be able to buy a used motor, or something used with a motor for a fraction of the new cost.
 
I turned the drum for mine from Maple using the sander itself as a lathe.  Once the maple block and its shaft are mounted in the pillow blocks, set up a tool rest and spin block with the motor.  An ordinary bench chisel works fine. I glue the sanding medium, hardware store belt sander belt to the drum with contact cement.
 
The NRG used to sell a plan set for the tool and are photos of my sander here on the forum.
 
Roger

Bill,
I am not shilling for Jim Byrnes or anything.  I believe that quality and realistic prices should be acknowledged and praised,  with machines that match our needs.  As for budget,  I can't make any helpful guidance.
For media, I buy rolls directly from Klingspor.  They are just south of me in Tarheelia, but UPS is everywhere.   It is my thought that your general situation is not unique and the open decision points would apply to others, exploring this scratch build universe.
If you do replace, I hold a positive wish that you get a worthwhile return, should  you sell your present machine.
 
As for the Byrnes, be sure to get spare screws et al.    A small screw top plastic container,  a 1/4-1/2" thick scrap board with holes for the Allen wrenches,  heavy duty double stick tape to fix all this to the machine base deck,  and everything is to hand - as well as a place to park screws when you change media.  If you just place them on your bench,  small parts run away when you are not looking.

I tend to think in proportions, rather than absolute values in a situation like this. 
You are reinvesting about 50% of the total value in a used machine of inferior design.
For another 50% you could buy a a machine that is more reliable, better precision, and allows for a less expensive and wider variety of sanding media.

Allan,
 
It is the inside the port  - of the sill - at frame level  - raised - not flush with the outside planking level -  (shown with your JPEG model) that I am asking about.  
The Goodwin cover art also shows it like this, but the inner layer of the lid is reduced to fit inside the sill and sides - the outside layer being as thick as the outside planking it closes into.
The Goodwin text does not seem to address this, or I am not seeing it if he does.
 
If I leave the lids closed,  the question of flush or raised will be moot.  One point for that option.
 
Another part - I think English style was for interior planking to cover the inside edge of the sill.  The French seem to have had the sill extend over the interior planking and have a lip that was farther inside - like a picture frame.

Jaager
Not sure exactly what you mean.  A drawing would help.   In the meantime 😀................
The lid is two layers, one horizontal, one vertical. Total thickness of the two layers matches the thickness of the outboard planking so when it is closed and rests against the stops on the sides and bottom of the port the outside of the lid is flush with the surrounding planking. Unless the side of the hull is perfectly vertical  the bottom of the lid has a slight bevel to  match up the opening.   The top of the bottom sills are not visible whether the lid is open or closed as there is a stopper piece.  The bottom of the upper sill can be seen as there is no stopper piece.  The outboard sides of all the sills are covered with the hull planking.  Hope the following photo of a contemporary model in the Rogers collection will help a bit.     TFFM Volume II has excellent drawings and description of the port lids &c.   
Allan

Thanks John,
 
That does make it much easier to fabricate.  I just checked Goodwin - and the cover art shows lids with a mortise on all four sides, but the text affirms your observation.   The figure with the text shows a bevel at the top and bottom, but no provision for a hermetic type plug for a lid.   They are just two layer plywood.  The outer layer is a continuation of the planking that it interrupts - with a goal to make it invisible when closed.  The inner layer is 1.5" thick vertical boards - 4 of them.  The two middle ones are equal and the same stock width and the two outer boards trimmed to fit the width.  
 
Because wood only changes dimension across wood fibers and not along them, the simple design would avoid jamming if the lid environment had a higher water concentration than that of its construction environment.  The inner layer is too thin to pose a problem if swollen.
 

I am cutting the rough openings for the Gundeck  ports. of HMS Centurion.
I use a standard 4" for the port sill and 3" for the lintel.  This is my standard for all decks.  Most of their bulk will be planked over, so any difference from prototype thickness does not matter.
How much if any of the top outer edge of the sill and bottom lower edge of the intel shows when planked?  Is there a mortise for the port lid at the top and bottom? Or is the planking flush there?
 
The sides:  rather than try to sand a flat plane at each side and try to make the width exact for the frames at each side, I plan to frame the sides with veneer.   For determining a minimum thickness for this veneer,  the question is = what is the mortise at each side?  How far short does the planking fall?  What is the width of the lid mortise at each side?
 
My intent is to dye the sill, lintel, and side fillers red - the shade is yet to be determined.  A color chart from the first generation ANCRE monographs only has one real red : vermilion.   I am thinking that like most colors, the stark, prismatic, pure colors had to wait about 200 years for the German chemical industry to develop.  The pigment would be a natural mineral.  The interior of a ship is a large surface area so the mineral pigment would need to be an economical one. 
The red that is the aniline dye red is probably too pure a red.  Toning it down is going to be work.  My past experience is that a little added black goes a long, long way.  A grey would be easier, but there are no white dyes to add to the black.

I built my vertical drum sander around a Dayton motor from Grainger.
General Purpose Motor, 1/3 HP, Capacitor-Start, Nameplate RPM 1,725, Voltage 115/208-230V AC   It is TEFC  and CW-CCW   It seems to be top quality.
It is also large, heavy and relatively expensive.   The reversing function is of no use for a thickness sander, so this is not the motor for your machine.   Grainger motors tend to be expensive and finding an appropriate one as your replacement -  a major headache at the least.  For my machine, the motor is everything I could want.   but I wonder if the Grainger customer base is corporate buyers or university grants - a base where a premium level cost is no barrier.  Given your task and the value of what you are repairing, you might should be ruthless in how much you spend on a new motor and avoid gilding the lily.

I built my vertical drum sander around a Dayton motor from Grainger.
General Purpose Motor, 1/3 HP, Capacitor-Start, Nameplate RPM 1,725, Voltage 115/208-230V AC   It is TEFC  and CW-CCW   It seems to be top quality.
It is also large, heavy and relatively expensive.   The reversing function is of no use for a thickness sander, so this is not the motor for your machine.   Grainger motors tend to be expensive and finding an appropriate one as your replacement -  a major headache at the least.  For my machine, the motor is everything I could want.   but I wonder if the Grainger customer base is corporate buyers or university grants - a base where a premium level cost is no barrier.  Given your task and the value of what you are repairing, you might should be ruthless in how much you spend on a new motor and avoid gilding the lily.

I built my vertical drum sander around a Dayton motor from Grainger.
General Purpose Motor, 1/3 HP, Capacitor-Start, Nameplate RPM 1,725, Voltage 115/208-230V AC   It is TEFC  and CW-CCW   It seems to be top quality.
It is also large, heavy and relatively expensive.   The reversing function is of no use for a thickness sander, so this is not the motor for your machine.   Grainger motors tend to be expensive and finding an appropriate one as your replacement -  a major headache at the least.  For my machine, the motor is everything I could want.   but I wonder if the Grainger customer base is corporate buyers or university grants - a base where a premium level cost is no barrier.  Given your task and the value of what you are repairing, you might should be ruthless in how much you spend on a new motor and avoid gilding the lily.

The advertising copy has the motor as 1/3 HP AC and drum speed 5800 rpm.
 
MM re-brands a manufacturer product, often from China or Taiwan,  so sometimes it is possible to skip the middleman and source a new motor from the mfg - who is a middleman for the actual motor mfg.
 
The design as it appears looks to offer some options, if you are willing to do custom mounting of a new motor.
The diameter of the pulleys can affect the ultimate drum rpm.
The enclosed and vented box for the motor is a bad design for motor life.  More air flow - more surface area - means a cooler running motor.  Hot motor = decaying motor.
 
I have been thinking that the sweet spot for sanding is a 1700 rpm motor.  Too fast a drum and there is danger of burning wood.
Any motor worth having may cost you ~$200 US.  Which is a significant fraction of a whole new unit.
 
Consider offering your old machine for sale for parts on Ebay or similat and buying a Brynes machine?

The advertising copy has the motor as 1/3 HP AC and drum speed 5800 rpm.
 
MM re-brands a manufacturer product, often from China or Taiwan,  so sometimes it is possible to skip the middleman and source a new motor from the mfg - who is a middleman for the actual motor mfg.
 
The design as it appears looks to offer some options, if you are willing to do custom mounting of a new motor.
The diameter of the pulleys can affect the ultimate drum rpm.
The enclosed and vented box for the motor is a bad design for motor life.  More air flow - more surface area - means a cooler running motor.  Hot motor = decaying motor.
 
I have been thinking that the sweet spot for sanding is a 1700 rpm motor.  Too fast a drum and there is danger of burning wood.
Any motor worth having may cost you ~$200 US.  Which is a significant fraction of a whole new unit.
 
Consider offering your old machine for sale for parts on Ebay or similat and buying a Brynes machine?