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Mike Seibert
11-17-2016, 09:06 PM
This is a message to J. Madison, Senior Member.

I just ran across a thread from 2013 discussing Herreshoff lines and plans. In that thread, you indicated that your roommate had the plans for a BB 15 and was planning on building one. I was wondering if that has happened yet? If there is a build in progress, I would love to learn about that . . .

I too have the drawings and other materials that I got a couple of years ago from MIT, and dream about building one. It appears that each frame may have a series of measurements in a kind of workbook, but so far I haven't been able to break the code. I would appreciate guidance on how to understand the notations in the workbook.

Thanks, Mike

BBSebens
11-17-2016, 09:46 PM
You might be better served sending him a private message.

rbgarr
11-17-2016, 10:36 PM
Contact the Herreshoff Museum for guidance on reading the offset booklet, which may be what your 'workbook' is.

WI-Tom
11-18-2016, 07:51 AM
It appears that each frame may have a series of measurements in a kind of workbook, but so far I haven't been able to break the code. I would appreciate guidance on how to understand the notations in the workbook.

Thanks, Mike

Sounds like a table of offsets. HERE (http://bateau2.com/howto/foam4.php) is an example and basic explanation of how that works.

Basically, the table gives a set of coordinates for a number of "slices" through the hull--and each "slice" becomes a temporary building mold or frame giving the shape of the hull for planking. So every set of numbers in the table gives you either a height or a half breadth (half the width of the boat at that point). Half breadth is measured from the centerline. Heights are measured (in the example linked above) up starting from waterline 1 (WL1). Other designs might measure up from the keel--but there will be a reference point used to measure all heights.

Traditional offsets are given in feet-inches-eighths, with a + or - indicating an additional 1/16". So, 1-9-4 is 1' 9 1/2", etc.

Does that sound like what you have?

Tom

Mike Seibert
11-18-2016, 11:44 AM
In the materials I got from MIT, I don't have a table of offsets in the traditional sense. I have two pages of drawings that give me lots of info, but no offsets. However, the drawings include a ruler, and indicate that 1 inch is equal to 1 ft on the drawing, so I can get close to the offsets for the bottom and sheer from the profile, etc.

The drawings provide five waterlines for reference, with the load water line labeled Waterline # 3. They also provide three lines that appear to be diagonals, but that is just a guess because I haven't worked with diagonals in lofting yet.

And then there is the workbook. It is arranged with a set of notations that appear to correlate to the Frame numbers. For example, here is what the workbook looks like for # 14:

4.1.0 2.11.4 (I assumed this is the sheer)
4 2.11.4
3.6 2.11.0 1/2
3 2.9.0
2.7 2.6.7 1/2
2.6 2.3.4
2.2 1.9.7 1/2
2 1.1.6
1.9 0.3.7
1.8.0 1/2 0.1.0 1/2 (there is a letter "R" to the left of this notation)
1.7.6 0.0.0 (I assumed this is the bottom height at the CL)

Today I made an attempt to loft those notations, using the left column as the height and the right column as the half-breadth from the CL. It worked pretty well . . . the points I lofted gave me a general hull shape . . . In addition, four of the points landed on Waterlines 2-5, which was comforting. However, a couple of the points were off and I don't know why. But, when I skip the points that are obviously off, the hull shape looks very much like the drawings.

The BB 15 has 36 frames in the space of a 24'10" boat, which I assume will need to be lofted individually and then plotted together to get the overall hull shape. I am tempted to loft one out of every 4-5 frames and to plot the general shape of the boat from them. I am also beginning to think that I would like to cold mold this hull with a layer of strip planking inside of a couple of layers of cedar veneer. I understand that you don't need nearly as many frames for a cold molded hull, and wonder if 12 frames spaced about 2 ft apart would be enough?

Mike

Mike Seibert
11-18-2016, 11:53 AM
I tried to edit the above post . . . the notations in the workbook don't reflect the spacing that I tried to put in there . . .
The left column is: 4.1.0, 4, 3.6, 3, 2.9, 2.6, 2.2, 2, 1.9, 1.8.0 1/2, and 1.7.6. And I believe these are heights above the base line.
The right column goes: 2.11.4, 2.11.4, 2.11.0 1/2, etc.

Hope this helps,

Mike

J.Madison
11-18-2016, 12:28 PM
Saw your PM. I think you are on the right track. I do not remember if these are to the inside or outside of planking. I would probably loft a station every two feet or so and then add as many new stations as needed for making molds after the fact. Adding a station is easy once everything is lofted.

Are the offsets that do not work all together in the table? If so they may be diagonals. Don't be intimidated by diagonals, they are simple to use and very helpful.

Bob Cleek
11-18-2016, 03:53 PM
If you search on youtube, there are some videos by the Herreshoff Museum that describe N.G. Herreshoff's method for designing hulls from half-models and his technique for taking off the lines from the model. These techniques are also described, IIRC, in L.F. Herreshoff's Capt. Nat biography of his father and Commonsense of Yacht Design. N.G. Herreshoff's design technique did not include drawing lines plans. He designed a machine which enabled him to lift offsets directly from the half-model and these were kept in notebooks which were sent to the loftsmen directly. The lofting was done from these offsets. Each mold was lofted directly from offsets in the notebook and then set up on the building floor. Perhaps the literature, or the explanations given by N.G. Herreshoff's nephew, Halsey Herreshoff in the Herreshoff Museum videos will explain the notation that N.G. used in his notebooks. If not, somebody at the museum should be able to decipher them for you.

If all else fails, you can enroll in a three-week three-unit course at MIT which will teach you how to loft an N.G. Herreshoff hull from his offset notes: http://textbooksearch.mit.edu/class/2.708