Offset for Hull Thickness

[bigjimslade]

I have had requests to make patterns for laser cutting frames for a plank on bulkhead 1:192 battleship hull.  That comes out to about 4' 8" long. I am not experienced in building such ships. What I am wondering is how much of an offset should there be on the frames the hull thickness. I bought a NIP book on building a model of the Thunderer. Yet that topic is completely overlooked in the book. When I raise this issue, people seem to think I am just being obstructive.  I know if, I just do it, and the offset is 1/8" off from how it has to be planked, the end product will be a noticeable scale 4' off and I will get @#$@#.

 

I would like to be able to say:

1. Here is the pattern. Cut the frame out.

2. Go to {this store} and buy strips in "{this thickness]" {and maybe this thickness}
3. After assembling the frames put down {one layer of this thickness} {? A second layer of this thickness} 

 

Therefore, I ask of those who might have experience, how much of an offset should there be?

How many layers and of what thickness of wood should go over the hull?

Where can such material be purchased?

I can even add, what thickness plywood should be used to make the frames?

 

 

[mtaylor]

I believe as designer, you have the right and obligation to specify such parameters on the parts.  And they should be noted in the instructions.    As for how many layers?  That's your choice though convention seems to be 1 or 2 layers.  Usually the first layer is a non-premium wood like basswod.  The second layer is something nicer.  It does depend on your model era (wood or steel).

 

As for materials... look on front page of MSW for starters.  There's  a long list of suppliers of many things.   Also, there's various lumber companies that sell various woods.

 

As to your last question... yes, definitely.  I would consider a set plans incomplete without this info.

 

I also suggest you go up to the Kit Reviews and have a look there to get and idea of what's in them.   Also some build logs for the era you are interested in.  MSW is vast resource of knowledge that can be applied.

[Jaager]

2 hours ago, bigjimslade said:

laser cutting frames for a plank on bulkhead 1:192 battleship hull.

Your subject is steel navy?

The lines are the outside dimensions?

The hull would be steel plates, not wooden planks. A double layer of strakes of wood = not an authentic look.

If there are enough molds, one layer should be enough.  The plating can be 3x5 cards. A primer that soaks in and sets up hard = stiff enough to resemble steel?

In this case, the thickness may be adding so little that the outside lines can be used as is.

The actual ship plans should provide plate diameters. A riveted or welded seam would have a support behind it.

The thickness of the molds = how thick will your laser penetrate and not leave a wedge behind?

 

In the situation of a double layer of wooden planking and starting with outside lines, Once you decide on how thick you want each layer to be, the sum of the two is how much is subtracted.

If it is a kit that you manufacture, the species for each layer, the thickness that you can obtain, and be sure will be available for as long as the kit is being manufactured - the price -  your choice.

If it is just plans, and a builder must source materials,  the thickness is determined by what can be easily obtained.

 

A wooden sail vessel at 1:192,  This is miniature scale.  I would question POB being at all practical.

Edited November 14, 2022 by Jaager

[Bob Cleek]

1 hour ago, bigjimslade said:

What I am wondering is how much of an offset should there be on the frames the hull thickness.

It might sound like a smart aleck response, but, seriously, the offset on the frames has to be the thickness of the planking or plating if the body section lines are drawn to the outside of the planking or plating. If the frames are drawn to the inside of the planking or plating, you just have to make sure your model's planking or plating isn't any thicker than the scale of the section lines. If your planking or plating has to be thicker than scale for "engineering" purposes, then that additional thickness has to be factored into the equation. It all depends first on the thickness of the planking or plating. On most models of iron and steel hulled ships, the model's planking will be much thicker than its true scale because that will be required for sufficient strength. On models of ships with wooden hulls, the deviation from scale may be less so, depending on the scale. 

 

When considering hull skin thickness, be it planking or plate, one must first consider whether the lines are drawn to the inside or the outside of the plank. This should be indicated on the plans, but plans for full scale construction may not indicate this by notation and the builder will have to determine that from comparing the construction and lines drawings. Details of the rabbet line may make it obvious. A section drawn to the inside of the frames should be obvious at the garboard seam where the deduction can be seen.  Plans drawn for modeling may differ from the full scale drawings of a given vessel as they are often simplified for modeling purposes. (This is frequently the case with solid carved block hulls and half-models which are usually drawn to the outside of the planking or plating.) 

 

In order to get the correct dimensions, a modeler has to 1) know whether the plans are drawn to the inside or outside of the planking or plating and 2) how thick (and likely out of scale) the planking or plating they will build is going to be. 

 

A modeler who has reached the level of accomplishment in their work to recognize the issue you have would find spending some time studying lofting practices a big help. There are many treatises on lofting. Alan Vaiteses' Lofting is one of the best.

 

Your question is addressed and explained at 5:25 in this video: 

 

[bigjimslade]

To answer questions:

 

I have a 3D model of the ship in the computer taken from original plans. I have collected images of over 2,000 original blueprints.

 

My 3D model is based on molded lines. The plating in the real world would zigzag across the molded lines. At the keel, it would go 2-inches outside the lines. At the sides, it would be at most an 1 1/2 inches outside the lines. So the real world plating thickness would be about 8 thousandths of an inch. The actual plating pattern is an absurd example of designers making things complicated for the sake of making them complicated. Strakes are lapped, rabbeted, and scarfed. The seam between strakes often reverses. The amount of machining just to make the shell was absurd. This kind of gold plated construction is why only four were able to be built during WWII. Even the famous hyper-detailed 1:48 Missouri model at the US Navy Museum shows a smooth hull without plating. I figure that I can do the same at 1:192.

 

Plus, in the real construction, the shell was built frame on shell. The actual hull form depended upon the accuracy of the mold loft, which ended up being off off by several inches in length in beam. 

 

* * * 

The reality is the shell thickness on any model is going to have to be substantially greater than the scale thickness on the actual ship. Therefore, I would have to reduce the frames to account for a thicker shell. It might be interesting to have the upper part of the shell made out of brass so that the extension of the sheer strake above the deck would not be massively overscale.

 

My computer and ship plan knowledge greatly exceeds my model shipbuilding knowledge. I don't have a place in my house where I can build things. I just have computers. I am trying to come up with a means for building  a model of a steel hulled ship.  What material? How thick? How many layers are needed?

 

One objective here is accuracy (while sacrificing precision). You can already get kits in this scale but the mass-produced kits are WAY off.

 

I had originally thought about having people CNC a glued up block of wood but all the vendors I have contacted have said this is impracticable for this size and that at least a 4-axis CNC machine is required. However, I see Bluejacket has carved hull kits of 510" "destroyers." 

 

I hope this clarifies.

 

[Roger Pellett]

The different plating thicknesses and plating seams that you see on whatever drawing that you are using shows how steel ships were actually built.  Different plating thicknesses reflect structural engineers using heavier thicknesses only where required by local hull stresses. This saved both weight and cost.  If you are building a battleship, armor plating was added only in certain areas.  The armor was so heavy that its extent was a major design factor.  In any case the moulded line is the actual shape of the frame.  The frame is not joggled ( shaped) to reflect different thicknesses of plating.  The hull of a real steel hulled ship is therefore not smooth.  There are steps in the hull reflecting different plate thicknesses.

 

Riveting of shell plating introduces more laps in the hull plating as the least expensive plating system was the “in and out method” where the joints in alternate plating strakes overlapped. Flush riveted construction requires heavy and expensive butt straps backing up all seams and except for some high end yachts was almost never used.  In riveted construction the frames were still formed to moulded lines and Where the “outer” strakes crossed a frame, a backing plate was sandwiched between the frame and inboard side of the strake and rivets were driven through all three thicknesses.  As late as the 1950’s even welded ships had some riveted joints.

 

The usual way to build a model with a plated hull is to build a smooth hull to moulded hull lines and to then plate the hull with material of your choice.  If you look on the scratch build logs (1901 and later) my Benjamin Noble Lake Freighter model features a plated hull.  For the plating, I used shellac saturated paper.

 

Roger

Edited November 15, 2022 by Roger Pellett

[bigjimslade]

More clarification:

• The relationship of the plating to the molded lines varies widely by location. In places whether the strakes alternate the molded line is sometimes on the outer face of the inner strakes and inner face of the outer strakes. In most cases the inner faces of the inner strakes it at the molded line. In places where the each strake laps the one able, the plates zig-zag at the molded line. In some cases the inside face of a plate is within the molded line. There are some places where the inside face of a strake are 1 1/4" outside the molded line. There places where the outside faces are entirely within the molded line.  
• There are some tapered joggles where laps have to become flush.
• The frames were templated to the shell plating during construction. There are notches in the frames at the lap joints. The frames usually do not align with the molded lines. They do so only where strakes not lapped. 
• Some seams are welded. Most are not.
• Riveting is all flush.
• Where used, butt straps were used externally on the upper two strakes and internally on other strakes.
• Seam straps were used on some joints. They always occur in the inside.
• Plate thickness varies from 17 1/2# to 80#
• Plates were chamfered where the thickness changed.
• Three different types of steel are used.
• In some places doubler plates were riveted in the gaps between laps so that the joint appears flush.
• The armor is all internal so that is not a factor. However, I have 3d Models of every piece of armor.
• I have made diagrams identifying each plate, it's thickness, material, location, and the joint at each edge.

The plating is such an unnecessarily complicated tangle that I would just everything smooth along the molded lines. The maximum different between plate faces is about 0.004 inches in 192 scale.

 

Thus I need from people with experience an approach to creating the overscale shell so that I can determine its thickness and the amount I need to reduce the frames by.

 

 

[Jaager]

2 hours ago, Roger Pellett said:

The usual way to build a model with a plated hull is to build a smooth hull to moulded hull lines

In which case, a straight forward hull construction would be to use a version of POF for the smooth hull.

The hull would look like a loaf of sliced bread, upside down and hollowed out.

It can be as hollow as you wish.  It is easier if the moulded dimension is thick enough for dowels (bamboo skewers) to be used for alignment.  Clear Pine that is maximum thickness for a laser for the "frames".  The frames are more economical if they are three 'timbers" alternating with five "timbers".  No spaces.  The "frames"  first assembled as station sections.  The sections shaped and then joined.

Clamps and beams added later for the deck.

 

If Titebond III  and the plating bonded and coated to be waterproof, nothing major extra would be needed for an R/C version.

[Roger Pellett]

How about a photo of a part of the drawing that shows what you are trying to explain?

 

Jaager:  Or as I prefer, carve two half models from laminated lifts, plate each half and join together.

 

Roger

 

Edited November 15, 2022 by Roger Pellett

[Bob Cleek]

5 hours ago, bigjimslade said:

Even the famous hyper-detailed 1:48 Missouri model at the US Navy Museum shows a smooth hull without plating. I figure that I can do the same at 1:192.

Yes. the Gibbs and Cox model shop which built so many fine models in its time did that model of Missouri. I believe it was built to Naval Sea Systems Command's specifications for USN ship models which prohibit "plank on frame" models of metal ships:

 

Hulls shall be built up in lifts of clear, first-grade mahogany or basswood; doweled and glued together with water-resistant glue. The wood shall be completely free of knots, checks, and sap pockets and shall be thoroughly seasoned. Models over 12 inches beam must be hollowed for reduction of weight The hull shall be composed of the least number of parts necessary to achieve the proper shape. An excessive number of glue joints shall be avoided. On models less than 12 inches beam, hull lifts shall be cut to the full body shape: lifts shall not be cut in halves, thereby creating a glue seam along the vertical centerline of the model. The lifts shall conform accurately to lines of the vessel as shown by the plans. A stable, durable, flexible body putty may be used in moderation to fill gaps.   Nautical Research Guild - Article - Specifications for Construction of Exhibition Models of U.S. Naval Vessels (thenrg.org)

 

As can be seen, metal hulls are made from carved solid blocks or "bread and butter" lifts with hollow centers. The USN specifications are worth studying and attempting to emulate. The Navy knows what it takes to build a ship model that will last. Their models travel frequently, relatively speaking, and they want them to "take a licking and keep on ticking." 

[Dr PR]

Jim,

 

The hull construction of the Cleveland class cruisers of the late 1930s and 1940s had the same complicated plating you described. Basically, the plating thickness (pounds per square foot) was thinnest high on the hull at the main deck and thickest at the keel, and thinner at bow and stern and thickest midships. To make it more interesting the bow had five vertical strakes! The plates were welded at bow and stern and riveted midships. And the overlapping pattern for strakes was very irregular. One difference is that the armor belts were bolted outside the hull plating.

 

I think you have answered your question already. At 1:192 the thickness differences between adjacent plates is insignificant. so I wouldn't worry about it.

 

Your design should just start with the Table of Offsets dimensions for the "molded breadth" for the inside of the plating. Then, if you have the plating blueprints that show plating weight (thickness) add this to the frame dimensions to get the external hull dimensions. This is your starting point.

 

Now you have to make a decision. What material and thickness will be used for the actual hull exterior surface (plating)? For simplicity in model building use the same material thickness over the entire hull. With this value, just generate a parallel line to the exterior frame/section lines and cut the bulkheads to these dimensions. That way, after the hull plating is added the hull will be the correct dimensions.

 

Because the differences in plating thickness between plates within strakes is insignificant as scale don't worry about it. A you said, where the thicknesses vary the edges of the thicker plates were ground down or beveled to reduce drag.

 

If you want to show plating overlaps between strakes on the model there is a very simple but effective way to do this. First just make the model hull with smooth surfaces (no plating). Then use masking tape to mask off the inside plates (yes this can be quite complex). Then spray a thick coat of primer over the hull. After it has dried remove the tape. This leaves very subtle thin edges between the outer and inner strakes that is good enough for modelling purposes. Where a strake may be overlapped on one edge and then overlap the opposite adjacent strake you may have to retape at the overlapped edge and apply another coat of primer.

 

I hope you can follow what I said, but it seems you are very familiar with the blueprints so it should make sense.

 

 Here is a link to an exquisite model of a plated hull using this technique - start at post #72:

 

https://modelshipworld.com/topic/19333-cruiser-varyag-1901-by-valeriy-v-scale-175/page/3/#comment-595525

 

Then go to the end of this thread to see some of the best modeling work you will ever see!

 

I ran into one major problem when trying to create my CAD model of the USS Oklahoma City hull. The plating blueprints show a "flat" pattern for the plating overlap pattern, but do not show the elevation on the curved hull surface for the strake edges.

 

After reading through hundreds of blueprints I came across the Table of Sight Edges in 81 blueprint pages titled "Mold Loft Offsets." These were the surveying instructions for locating the vertical position of hull plates in the framing of the ways. And the frames were added after the strakes were laid down.

 

To see how I used this information to model the plating look here

 

https://modelshipworld.com/topic/19321-uss-oklahoma-city-clg-5-1971-3d-cad-model/#comment-590610

 

or here:

 

https://www.okieboat.com/CAD hull.html

Edited November 15, 2022 by Dr PR

[bigjimslade]

Thanks,

I have the shell sight edges edges table and table of offsets. Got those into Excel, then into Rhino to create a 3D model of the plating locations. I did the same to get the hull form.

I have played around with an offset of 0.04-inches to get an idea of what could be down but I am thinking that might be too thin. 

I made all this stuff (except for the test frames) for structural analysis. People keep asking me for laser cut frame patterns without giving any direction beyond that as to how thick the shell would be. I have seen some really ugly models where the frames did not account for the shell thickness.

[Roger Pellett]

I believe that you are over thinking this.  If you have a set of mould loft offsets or  the actual lines drawing, either of these will yield the moulded hull.  In other words, the shape of the hull without its plating.  The hull of the Missouri that you mention has been built to these dimensions.

 

The plating is added to this moulded shape.  In the case of the Missouri model, the plating is so thin in relation to the size of the ship to be insignificant.  If you want to add plating for realism pick a material and standard thickness.  At a scale of 1:200, 80# plate is still only .01in thick and 17.5# about .002in.  When you start worrying about the differences of .001in you’re in the realm of a coat of paint.

 

Roger

[bigjimslade]

Miscommunication here. I just want to get a smooth hull at the molded lines. "Real world" plating in scale would be way too thin for a scale model. I am trying to figure out what would be a realistic shell thickness for such a hull so that I can subtract that from the frames.

 

If I leave the frames at scale and someone has to add 1/8" of material to make a strong enough shell, the shape is going to look way off.

[Roger Pellett]

My models are carved from solid like Navy Specs posted above except I carve two half model so a center glue seam exists.  I would suggest this technique for your model.

 

I’ll leave necessary thickness of planking of a POB model to experts with that technique.

 

Roger

[bigjimslade]

Let me try this again.

Here I have a molded cross section in RED.

1" "real world" plating in scale is in Blue. In 1:192 real world plating is a paper thin 0.005 inches.

For someone to build something like this they would have to use something thicker. Here I have arbitrarily picked 1/8" (in blue). That much shell over the model lines visibly distorts the hull shape because it add a scale 4 feet to the beam.

Therefore. I need to offset the frames to allow for a shell thickness that sufficiently thick for a scale model (which would be something like green).

Because I lack experience I have no idea how thick that needs to be for a 4 1/2 foot long model.

 

So much do I need to reduce the frames to allow adequate thickness for the shell of a scale model?

[Jaager]

Perhaps you should back things up a step or two.

Although I admit to seeing POB as being too hideous to be used for much of anything,  in this situation I think the problems with it transcends my obvious prejudice.

It does not fit will with iron or steel construction.

A scale of 1:192 is beyond the capabilities of the technique.

Trying to fight Nature by over scaling the materials to try to force strength where it does not reasonably fit is why you are proposing an under size for mold surface area and overly thick shell material.

 

A POB wooden hull has a longitudinal shell (planking) that spans multiple molds.  The shell members butt on alternating and widely spaced molds.   You may have to use planking strakes to pull off what you propose. The problem is that your hull is 4-8 times longer that most wooden hulls. 

If the molds are close enough together, a single layer of planking should suffice. 

The length of the hull will have it wanting to bow and break.

 

 

 

The stress will probably require a total planking layer that is inappropriately thick.

That it is planking will make it difficult to get the flat planes that are desired.

The old wooden hull guys probably would have wanted to have a longer hull.  The physical properties of wood limited their possibilities. 

 

There is no answer in the back of the book for your question.  If you are determined to continue on your proposed path, the likely answer is that you will have to do the experiment yourself.  If you can find find a practical combination of spine thickness, mold thickness, shell thickness, then you can tell us

 

The real answer is to build a solid hull. A hull that is exactly the finished dimension and use as thin a material as can be had to cover it.

 

 

@Roger Pellett  both of our methods fail the Navy standards according to what @Bob Cleek presented.  Your two half hulls makes it easier to manage, but the Navy does not like the midline seam.  My method is beyond their imagination - probably because it is WWII era and PVA had not been developed.   The species of Mahogany that they want has been loved to death and is no longer available.   Boo - on the Basswood.

[bigjimslade]

Would you know of any sources that can mill a solid hull? I was not able to find any source that could cut the shape. I was told I need a four or five axis milling machine. I could only find people with 3 axes.

 

Plank of bulkhead is my third approach.

[Bob Cleek]

38 minutes ago, bigjimslade said:

Would you know of any sources that can mill a solid hull? I was not able to find any source that could cut the shape. I was told I need a four or five axis milling machine. I could only find people with 3 axes.

 

Plank of bulkhead is my third approach.

I read somewhere that the original Model Shipways company purchased surplus gunstock duplicating milling machinery after WWII and put it to use milling solid hulls for their ship models. Obviously, this was not CNC technology. There are custom gunstock makers who do such work, but they all seem to primarily use mechanical duplicating machinery, not CNC. This machinery will work fine for duplicating hulls, such as for kit production, but to do this a master pattern is required. If you only want a single hull, it will have to be hand-carved. If you wanted someone to produce a one-off carved hull for you, your best bet would probably be a old-school foundry patternmaker. 

 

For a model the size you are contemplating, a hollow "bread and butter" lift hull is the easiest, and best, method. I can't imagine why anybody would want to do it any other way, given the challenges involved in building a plank on frame model of that size. (It's not like you will be building an exposed-frame Admiralty Board style wooden ship model.) 

 

This three-part YouTube video gives a pretty good explanation of the "bread and butter" hull construction method. He stacks his lifts with the seams vertical. It can also be done by stacking the lifts with the seams running horizontally. The horizontal method employs the waterlines as patterns for each lift. The vertical method employs the buttock lines as patterns for each lift. 

 

 

Edited November 16, 2022 by Bob Cleek

[Roger Pellett]

If you don’t have a shop and can’t or don’t want to set one up try to find some sort of shared shop space where you live. Adult education comes to mind.  Go to your local lumberyard and buy a nice 1” straight grained pine board (actual thickness 13/16”).  With your CAD system lay out 13/16” longitudinal slices through the hull either vertical or longitudinal.  Print these and glue each to your pine board.  Bandsaw out each slice, and glue up a the stack.  Using hand tools and templates cut from the body plan, carve the hull.  This is exactly how professional model makers have built ship models for 100’s of years.

 

There are companies that machine carve custom gunstocks.  I don’t know of any specific ones.  You might try checking them out.  In the old days their machines duplicated a pattern.  Today ai would think that they use CNC.  Even these will require some final shaping.

 

Roger

OOPs. Bob Cleek said it better than I did. I didn’t read his post before writing mine.

Edited November 16, 2022 by Roger Pellett

[Jaager]

46 minutes ago, Bob Cleek said:

I can't imagine why anybody would want to do it any other way, given the challenges involved in building a plank on frame model of that size.

I can't get anyone else to eat the mushrooms or drink the Kool-Aid, but the Station Sandwich Method can be a fairly rapid way to construct a hull.  In this instance the troublesome factors are not a part of it. 

That would be worrying about the spaces - there are none 

and

making the individual timbers match the lengths of the prototype vessel - all that is needed is for the grain to be as straight as practical in each segment

and

making the moulded dimension match the original and the inside be faired - fatter is better since the alignment can be here and rough does not matter.  It might need some attention if a motor and radio equipment would live there.

 

The method that I am suggesting does not need a building board or alignment jigs.  The pieces internally align themselves.

The size of bread and butter or buttock layers makes for more hand chisel and hand power sanding.

A body station section of layers is small enough to take the work to a belt or drum sander. 

 

I was guessing that the OP was interested in multiple copies or providing a data file that would direct a laser cutter for customers.  Both of the other solid/hollow hull methods use stock that is too large for a laser cutter.  If a laser can cut 1/8" Pine, then each frame would be - what?  16 feet in scale?   It would be about 50 layers for a 850 foot hull?  With straight timber segments,  fairly efficient use of a board could be laid out.  I suspect that the laser could "paint" the sand-to lines and alignment hole drill points directly on a board. 

[Bob Cleek]

7 hours ago, Jaager said:

the Station Sandwich Method can be a fairly rapid way to construct a hull. 

It certainly can be. It's just another way to "slice the bread" in a "bread and butter" construction. That said, I'd expect that "slicing the loaf" along the waterlines or buttock lines would involve a lot less tricky scroll saw work than cutting sections and working down the  slices with a chisel, plane, or spokeshave with the grain rather than across the grain would be easier as well. No?

[Jaager]

5 hours ago, Bob Cleek said:

would involve a lot less tricky scroll saw work

I use a 9" bandsaw with a 1/4" blade and a Carter Stabilizer.  The blade swings on its back edge like  a screen door. 

What I am suggesting here allows for a more refined cut for the outside face.  There are no alignment pins outside the body of the frames, so the actual frame shape can be got at.  

 

For real POF the stack of frames between each station is thick.  For the station intervals other than the dead flat - the curve of the hull has almost no areas where a perpendicular thru the stack would be inside the body of the frame.  The alignment pins must be outside the frames.  The scroll cut is then sort of close enough not to be toooo fat - but not slice into the pin sites.  The timbers are mostly sort of rectangles. The cut goes quickly.  When a stack of frames is glued up, what you do with hand tools, I do using a belt sander or drum sander with 80 grit medium.  The identical pattern is on both faces of the stack so I can get fairly close and have an accurate bevel.  The fine work is 220 grit on the drum.   Now, at the two or three stations at the bow and stern, the bevel is impressive.  The amount of extra wood to remove takes time  and the volume of dust makes for a good desert sand storm.   I had M-95 masks on hand when SARS-2 hit.  The outside is never all that difficult to shape.  It is the inside that is challenging.  At the ends, especially the stern, where the slope gets acute,  getting at the area of the keelson requires hand tools.  It takes time and gets frustrating.  Because I am working with segments, I can take the work to the tools.  I can manipulate the work at a stationary tool.

 

 

For this project, the stern is not like that and the inside is mostly not needing much work.  It can be most anything - since it will be hidden.  Only if RC was the goal, would the inside need any attention.  The inside can be left fat enough for the alignment pins to be inside and be inside all the frames in a section.  I would even use bamboo skewers inside of steel quilters pins and glue them in.

 

One factor with the Station Sandwich Method is that it is power tool heavy.  Because the frame thicknesses must be precise and uniform,  because there are so many frames,  it requires a lot of wood.  It almost makes it necessary to be your own sawmill.  But I guess any sort of scratch POF requires that.

[Roger Pellett]

20 years ago, I decided to experiment with a simple 2D CAD system (Generic CAD) to see if I could a model of a Passaic Class Monitor.  The body plan is included in a GPO booklet.

 

After drawing and printing a complete  lines drawing , I cut out a section of hull for each body plan section and formed a stack-  Jaager’s stack system.  I then shaped the hull.  Doing this was easier than the horizontal or vertical lift method.  I simulated plating with paint; masking alternate strakes.  

 

All went well well until late in the build  tiny cracks began to appear between sections.  Had the model been plated over the carved with some sort of material this would not have been a problem.

 

Moral of the story:  This system works well, but make sure that you have sound glue joints between sections.

 

Roger

[Jaager]

I use the HF 4" ratchet clamps with the large grey wing nut - and as many as possible - because they can apply significant pressure.  This for the frames within a section.

A book press and plate press to join sections - helps but is not perfect - The surfaces at the FP and AP are often not directly opposite so the force lines do not play nice for final assembly sometimes.  But then, there are many areas on any ship model where significant clamping pressure is difficult.

 

I can use a basic raster drawing program to get my patterns.  The curves are line segments instead of smooth curves,  They look like curves and the sanding makes them smooth curves.  The process is hands-on with very few commands - only the basic - DRAW, CUT, PASTE. An almost flat learning curve.

Edited November 16, 2022 by Jaager

[bigjimslade]

16 hours ago, Jaager said:

I was guessing that the OP was interested in multiple copies or providing a data file that would direct a laser cutter for customers.  

Actually, I was planning to just post the files to help people out. But I don't want to post one that will bring the wrath of the internet down on me. 😞

[Jaager]

6 hours ago, bigjimslade said:

But I don't want to post one that will bring the wrath of the internet down on me.

Well, should you be mad enough to do it using the Station Sandwich Method, the likely response would not be wrath, it would be ....crickets.

Edited November 17, 2022 by Jaager