Cad design drawing the steam frigate Mississippi

[Dave Stevens (Lumberyard)]

USS MISSISSIPPI 1841

 

[Dave Stevens (Lumberyard)]

Drawing plans and laying down lines in a mold loft for real ships is not the same as prepping drawings for building a model of a ship.
I have collected 126 images of drawings for the Mississippi and Steam frigates, out of all these drawings I will use only the very basic information to get the job at hand done.
What I need right now is the shape of all the hull frames so first I traced the bodyplan, the draftsmen took time and great care in getting these lines just right so I will use them as is.




from the profile drawing I traced only what I need right now. This includes the sheer line along the top of the bulkhead, the location of the decks, gun ports, station lines and over all shape of the hull. the two end blue lines are traced from the original drawing and they are the perpendiculars. I know the hull is 215 feet between these lines so I scaled the drawing to that. Next is to line up the bodyplan on a base line which is the rabbit line. The bodyplan was also scaled to the breadth which again are the blue lines, this measurement is 13 feet.

When I se up the drawing first thing I noticed was the bodyplan is drawn only to the deck level the upper works are not included. Perhaps because the line above the deck is straight up.

 

[Dave Stevens (Lumberyard)]

what you are looking at here are the frames the red frames are drawn in the bodyplan the black lines are a copy of the red lines. These black lines are not included in the bodyplan and they have to be added.

 

[Dave Stevens (Lumberyard)]

the set of black frames go between the set of red frames like this

 

[Dave Stevens (Lumberyard)]

zooming in you can see the frame spacing

this is also a prime example why model builders have problems with planking bulkhead hulls with the bulkheads so far apart. Real ships were almost a solid wall of frames so the planking had enough backing to conform to the shape of the hull.

 

[Dave Stevens (Lumberyard)]

now I need all the shapes of the black frames and that will take awhile
Before I do add the black frames I will check the bodyplan lines up close.

this is what they should look like all the lines are running the same distance apart and parallel to one another.



but in some cases they are running a bit wonky the line pointed to by the purple arrows started to run off at the bottom and by the time it got to the top it is off. the magenta arrows shows where the line should be.



here is another example of lines going bad. This happens because CAD is taking points along a spline and calculating a curve between points. It is not taking into the calculation the points in the lines next to it so the line your drawing is running parallel.
The purple arrows show the two lines that went off.

NOW consider you are looking very close to the drawing so close you could not see this if you were drawing with a pen by hand on paper. Measuring the lines they are .004 thousandths off really close and perhaps "good enough"

question is do I leave it along or take extra time to fix the lines?

 

[Dave Stevens (Lumberyard)]

no doubt about it every line has to be as perfect as I can get it just like the Princess Charlotte bodyplan

so yes if it is .004 thousandths off I will redo it, the reason is there will be errors all along the way of this build so if things start off with slight errors they will only add up.

 

[pebbleworm]

Excellent information! I found out about double checking lines the hard way when I just scaled up some Dutch Boeier lines from the interwebs. The bulkheads did not work out that well and I had to shift a few around and do some reshaping. When those crazy Russian Doctor Bob(?) videos showed up a while ago, he made a big point of checking the damn plans too. Measure twice, cut once is is always good advice. And your explanation is clear and concise. Plus, I have always had a soft spot for paddlewheel warships.
EDIT: I looked up the Russian videos- it is Doctor Mike and they are chock full of information delivered at a rapid fire pace. I have been Shanghaied away from home for the past year and a half and at a dead stop on ship models, so I am getting re-oriented. Well worth checking out, but I wish there were transcripts. My 2 years of Russian taken back in the Soviet era helps a little, but I really like his translator. You can find these on youtube at:
https://www.youtube.com/playlist?list=PL5wX2_PJGI8sxN_zzXNTWaZ9qi-U_9Zp7

 

[Dave Stevens (Lumberyard)]

Excellent information! I found out about double checking lines the hard way when I just scaled up some Dutch Boeier lines from the interwebs. The bulkheads did not work out that well and I had to shift a few around and do some reshaping. When those crazy Russian Doctor Bob(?) videos showed up a while ago, he made a big point of checking the damn plans too. Measure twice, cut once is is always good advice. And your explanation is clear and concise. Plus, I have always had a soft spot for paddlewheel warships.

There is so much time involved in creating a set of working plans and thousands of entries your adding to a drawing mistakes and errors are bound to happen. This is why at every step I go back and check and then check the checks to other sources or plans.

This ship to me is the ultimate modeling project because it is a wooden hull so there is that element of working with wood and a wooden structure, then there is a lot of iron work to model this adds the head scratching thinking " hum now how am I going to do that?" After the hull there is the steam engine and boilers that is a model engineering project all its own. I am thinking to kick it up a few notches and add a little air pump to the engine so it actually can move.

 

[Dave Stevens (Lumberyard)]

Back to the drawing, a question rarely asked by kit builders is how big were the frames and how far apart were they spaced? there is no need to know because kits are not built any where close to actual ship building if it is a plank on bulkhead model.

But for a framed model it is a question needing an answer. Just about all ship plans do not contain construction information or the sizes of planking and timbering, this information is common knowledge among shipwrights or it is written down in either contracts, personal books of a master shipwright or as published specification establishments of scantlings. This information is out there in museum archives, historical collections or in private hands.

here are some examples of construction details

 

[Dave Stevens (Lumberyard)]

Joshua Humphreys father of Samuel Humphreys who actually designed the Mississippi, kept a day book of everything he did and all the sips he built. Lucky for us his book is still with us and here is an example of specifications on building wooden ships.

 

[Dave Stevens (Lumberyard)]

You may wonder but how does this information help in the building of the Steam Frigate Mississippi?

it doesn't but it does show the information is out there for most any ship you want to model.

for the Mississippi the first pieces of information you need to know is who designed and built the Mississippi and in what shipyard was it built.

the three men were Humpherys, Hartt and Lenthall and the Mississippi was built in the Naval shipyard in Philadelphia PA.

so from this info you follow the historical path and BAM! here are the construction details

 

[Dave Stevens (Lumberyard)]

got lost in detail there

the question was why did I use the size and spacing of the frames?

I made it up is the short answer,

I pulled a Harold Hahn and he got a lot of bashing for the framing on his models because according to some they are not historical correct. But those pointing a finger were so totally wrong Hahn was correct he just tweaked the specs so the model looked good.
That is what I did with the Mississippi if I were to use the specs the hull would look like a solid mass of timber I wanted a little space between frames so when the model is viewed you can see the individual frames and the space gives the hull an openness. It comes down to an artistic balance of form and space. HOWEVER I did stay within the parameters specified for framing of such a hull.

That is another thing these guys bent on absolute historical accuracy. It can not be done unless you are building a model direct from wreck data. All these specifications are "parameters" no less than and no bigger than and anything works if it fall between the specified dimensions. From shipwreck data I collected over years frames varied from 2 to 4 inches in dimensions and spacing seems to have been random. This everything being exact sizes and spacing is a model thing and not actually how ships were built.

 

[Dave Stevens (Lumberyard)]

a progress report on drafting the bodyplan here you can see I am adding the missing frames between the red frames. This is a long and tedious operation but it has to be done. a small section toward mid ship still needs the black frames added.
you can see at mid ship it looks like the lines all run together as one big blur. Actually



looking very close you can see why this can not be done on paper with a pen, in CAD I can zoom way in until the lines are separated now I can see the spaces between lines and draw in the missing frames.

if your interested in how I draw in the missing frames you can go here.

http://modelshipbuilder.com/e107_plugins/forum/forum_viewtopic.php?4506.60

 

[Dave Stevens (Lumberyard)]

here is the final bodyplan with all the frames drawn in. I used different colors for each frame shape so I can tell them apart and also identify each one and its place in the hull.

 

[Dave Stevens (Lumberyard)]

to draw the frames the steps are as follows

first the bodyplan is lined up with the profile the top 2 green lines are the lower line is the deck the top line is the sheer the very bottom line is the rabbit line




a copy is made of the center frame and moved to the right, the short blue lines are the molded dimensions and the green lines is the width of the keel.



the outer line is copied and moved to line up with the blue lines. Notice it does not touch the line at the keel.



the inner line is broken at the turn of the bilge so now the lower part is a separate line. it has been selected and is a dotted line.



the dotted line is then rotated so it touches the top of the blue line and reattached to the rest of the line



next is the green line (deck line) is selected and is now a dotted line.



the frame lines are trimmed to the deck line




the bulwark lines are now drawn in



the frame shape is mirrored





down at the bottom the lines are trimmed and a notch is added




finally the frame is drawn it takes 12 steps to draw one frame. There are 86 frames in the hull so it requires 1,032 moves to complete a set of frames not counting the bow and stern frames. This is going to take some time.

 

[Dave Stevens (Lumberyard)]

This is a project that can be broken down into various smaller model x sections. My approach to the model is first build the center blue section this includes the steam engine, boilers and paddle wheels. Once this section is built I will then continue onward to the bow and stern. Anyone interested in the Mississippi can build any one of the colored sections.





what makes X sections of this hull interesting is the iron work. The hull was strapped on the outside


this was a common method to stiffen up a hull and you can see the strapping drawn on a number of plans



on this shipwreck you can see the strapping is set into the face of the frame.




doing a X section of the bow would be interesting because of the 120lb cannon set on a sled and iron circles plus all the gun ports



and the gator figurehead



the gun carriage and sled

 

[Dave Stevens (Lumberyard)]

The navy got a lot a negative feed back from the press with the first 2 steamers they built calling them down right ugly. So the stern cabin was all Mahogany paneled and done up to be real pretty. so a stern x section is another possible model.

here is the mid section in a large scale and if I can do it I will make a model of the steam engine so it will actually move from an air pump.

 

[Uwek]

Great idea and a big task....I am following your explanation and information with big interest

 

[mrshanks]

Serious research!!! Very impressive!!!