The Ship Model Forum

My Problem I am used to stations being on the left, waterlines on the top listed plainly as feet, and then the offsets

here they are listed differently and no matter what I do I cannot seem to get the correct sequence.

is there anyone that knows enough about offset tables to help me figure out the correct sequences of numbers for the tables

Just remember that somewhere in all those numbers there is elevation data, length along the keel data and hull width information.

The "Stations" are ALWAYS the length along some imaginary "Base Line," but always the length from bow to stern for US ships, and from stern to bow on European (French, German) drawings. I'm not sure what direction the Brits used - probably bow to stern to be different from the French.

The "Fore Peak" (FP) is ALWAYS near the bow (forward or fore) and the "Aft Peak" is always near the stern. These are the points on the normal load waterline where the fore and aft most parts of the hull cut the water.

So for the entire table the "Stations" are the length information. The catch here is the table doesn't say what the distances are between stations - you have to look at the profile or plan view drawings to find this distance. Station to Station spacing is not the same for all ships!

Normally the length along the load water line (between Fore and Aft Peaks) is divided into equal spaces called "Stations." So the distances between stations from Station 0 (usually the fore or Aft Peak) to the highest integer numbered stations are equal. However, sometimes fractional stations (1/4, 1/2, etc.) are given. The distances between these are 1/4, 1/2 or whatever the distance between integer numbered stations. You sometimes see fractional stations at the bow and stern where hull curvature is greatest.

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"Waterlines" are ALWAYS horizontal planes that cut across the hull from port to starboard - perpendicular to the vertical. Think of them as the levels of water on the hull surface in a drydock as it is being flooded. They are elevations above the "Base line."

The "Base Line" can be anywhere - it doesn't matter. The elevations offsets from the "Base Line" tell the vertical position of the other numbers in the table. The "Base Line" may be the floor of a construction frame for boats, or it might be the top of one the keel plates on larger ships. It doesn't matter. All elevations are relative to one another so the actual "Base Line" is irrelevant. It should be shown on the profile drawings. Just use the Waterline elevations for your vertical coordinate for the points on the hull surface.

In the table you posted the "Half Breadths" portion (the top part) gives coordinates (distances from the center line) of points on the outside of the hull planking for distances along the length of the ship (Stations) and elevations (Waterlines).

If we let the length of the ship be on the X axis, the height on the Z axis and the width be on the Y axis, Stations are the X values (length), Waterlines are the Z values (vertical) and the Table of Half Breadths gives the Y values (horizontal) from the center line to the outside of the hull planking. The table defines only one side of the hull, the other side is a mirror image. That's why they are called "half-breadths."

NOTE: The text under the tables says "Offsets measured to outside of plank." This is common for small wooden boats. However, for larger steel hulled ships the half breadths are usually to the inside of the shell plating.

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The "Heights" part of the table gives elevations at "Buttock Lines" (Butt Lines). These are vertical slices through the hull parallel to the center line at specified distances from the center line. Elevations along these Butt Lines are given for various positions along the length of the ship at the specified "Stations."

Again, the distances from the center line to the Butt Lines is not specified in the table. You have to get this information from the plan drawings. But all points in each Butt Line are the same distance from the center line.

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The "Sheer" line is points along the top edge of the hull at each Station. The width offset from the center line varies with the curvature of the top edge of the hull, being at the center line for the fore and aft most Stations.

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The "Rabbet Line" is where the planking in a wooden ship/boat meets the keel from bow to stern. It is typically half the keel width from the center line.

A "rabbet joint" is a cut or groove into one board that another board fits into. Historically, in wooden ships a notch was carved into the keel beam for the first plank (Garboard Strake) to fit into. This was the "Rabbet" or "Rabbet Line." This terminology goes back many centuries and is still used.

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Finally, the numbers (such as 4-11-3) are feet-inches-eighths of an inch from the centerline outboard to the point on the hull. These are the distances (Y) at each Station (X) and each Waterline elevation (Z) from the centerline. So 4-11-3 is 4' 11-3/8".

Simple, isn't it?

Phil

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A collision at sea will ruin your entire day. Aristotle

I think I got them figured out. the stations are 6'-6" apart and a 1/2 distance between station 0 and 1 and 1/2 distance between station 9 and 10

Waterline 3B is 36" then each waterline above that is 1' between each

my problem was trying to organize them to be similar to the Fletcher which was easy to read here they mixed everything around. also the stations go backwards where 0 is the AP and 10 is the FP

I think I have the excel file rearranged will be testing it out shortly but still have to figure out the curve for the rabbet and the buttocks

http://www.proflooney.net/hullines-01.rar

well got the curves all in but man are they screwed up gonna take a while to adjust them

I have found two types of errors when working from the Table of Offsets. Most of the time I have typed in the wrong number - a 4 for a 5 and such. Occasionally I have found errors in the original table, and again they appear to be the substitution of one number for another. I guess most of the original numbers were calculated with a slide rule and every now and then the draftsman read the wrong number.

The result of these errors is a kink in the curves like you see in the picture you posted. But they are easily corrected because the error is always an increment of one foot, one inch or 1/8 inch.

Phil

_________________
A collision at sea will ruin your entire day. Aristotle

yea I remember what you taught me on the fletcher. these offsets were almost all even numbers I need to take into account the rabbet location for the endings too. this is mainly a practice to keep figuring out these offset tables but this would be a nice radio control boat to do with my grandsons

another thing that is funny is you find a nice hull in delftship and export the curve files and even they turn out like crap. funny a ship program exports curve files that arent correct too or it is just giving extra dimensions

hey guys I finally came across some awesome drawings and the cool part is they have already been corrected of errors by the team that was going to restore one of the ships.

I am giving a link to all I have on the ship along with my excel sheet for the offsets and my curve files

here is my problem I got all the curves tested in solidworks and they indead have been fixed up however I am missing the info for a couple dimensions to enter into the curves for the stations to complete them.

I am missing the Half-Siding, the Deck Sheer and the Plank Sheer Dimensions to finish the curve files off properly

http://www.proflooney.net/Steamer-Schooner-Wapama.zip

it is The Steamer Schooner WAPAMA Circa 1915

above is zip file of everything I have its the drawings, an excell file I made of the offsets, and all the curve files I made for importing into Solidworks (unlike some other cad programs I have to make each curve file as a separate file

these are some really really nice plans and I want do do a good job on it as its one of the few sets of drawings where i can actually understand them as a newbie to ship modelling. I just am having some problems at the moment figuring out what those 3 missing dimensions come from so I can enter them in the proper space in my tables

thanks

Joe

Joe,

This is really cool! I visited the Wapama back in the 1972 while I was at Treasure Island for discharge from the Navy. It was at the San Francisco Maritime Museum. It was a lumber "schooner" - the steam powered version of the original sail powered lumber schooners that carried timber from the northwest to California. It also had a few passenger cabins in the after superstructure. It was immaculate in the passenger section, with some of the most beautiful woodwork I have ever seen in the passenger salon, Captains quarters and the main staircase descending from the weather decks.

Unfortunately it rotted away and was finally scrapped in 2013. What a shame!

Phil

_________________
A collision at sea will ruin your entire day. Aristotle

yes i thought it was really cool i dunno I came across site for it and said thats it I got to do it. the plans were redrawn to correct errors and everythings coming out great. the only problem I am having is with the stations.

the station offsets are Great they work fine.

however there are 3 dimensions for each station I cannot find or figure out where to get from. so my stations are incomplete.

one dimension is called a half-siding, the other 2 are the deck sheer and the plank sheer. if i can figure out where to get those 3 dimensions from ill be all set to go and start lofting up the hull

Drawing 00010a.tiff table of offsets has the deck sheer, plank sheer and half siding dimensions. Deck sheer and plank sheer are also shown in the drawings.

Half siding is the distance from the center line to the forward edge of the shell plating, or the distance from the center line to the bearding line.

The bearding line is the line of intersection of the plating and the stem or stern post.

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Where did you get the drawings of the Wapama? They are some of the best ship drawings I have ever seen!

Are there more ship drawings there? I would love to get plans like these for the C. A. Thayer - one of the original west coast lumber schooner sailing ships. It was a predecessor of the Wapama, and was also in San Francisco at the Maritime Museum.

Phil

_________________
A collision at sea will ruin your entire day. Aristotle

Phil it's top secret lol me I come across a museum type site for the wapama the other night saw the awesome drawings downloaded them and left the site as didn't have any other pictures lol so you have everything I found but the five or six I was able to find on google images. When I get off work in 2 hrs will try to figure the dimensions out. I used some that were shown but got bad results. The cool thing is everything limes up almost perfectly with the line drawings when using curve files. When get home will post the size to enlarge drawings to in CAD to make everything lone up perfectly

ok here are the dimensions

sheet 00006a i used for profile on the front plane and also for the stations on the right plane. I didnt cut the sheet I just used the wole sheet but the drawings are different scales thus the different szes.

for profile view:

Length: 3167.24720294in

Height: 2446.57474368in

For the Stations:

Length: 2111.33276274in

Height: 1630.92208528in

using those dimensions when you do the curve files in cad program with the offsets I have in the excel file they match up perfectly

as you can see here most of my curves are there just missing the top and bottoms thats where the sheer numbers etc go.

9 1/2 and 10 are off so I need to mess with them but the rest are spot on.

well still screwed up and not correct cause i couldnt figure out some of the dims but also some of the lines from the sketch wasnt sure on cause they blurred together but if I can tweak the transom area it will be really close and will look close enough

I think the rear is correct though looks like station 10 starts a knuckle around the transom

i found where got from heres some really good shipyard and other photos https://www.loc.gov/resource/hhh.wa0212.photos?st=gallery
and https://www.loc.gov/resource/hhh.ca1521.photos?st=gallery

Thanks. I looked at the site and found plans for the C. A. Thayer! Lots of good photos too.

Phil

_________________
A collision at sea will ruin your entire day. Aristotle

well after work this afternoon i am starting over lol I cant seem to get this offset file to work dunno if reading wrong or what but i keep getting the wrong numbers for those 3 i need for each station

Ok so now i started all over and got my main cirves now I will play around with numbers trying to get the top and bottom of the curves finished up.