Changing dimensions/effect on stability

Don,

Is there not an existing, proven plan in the dimensions you seek?
A design with proven stability and seaworthiness?
Wouldn't a replica be more authentic than a recreation?

Sorry to rock your boat but these questions I find pressing.

BB

 

Dave, thank you for all of this, very helpful to have!

 

There are 8 wherries still in use, 2 are cargo. The type died out around 1900 so unless someone took an interest in the early 20th century, the 3 0r 4 lines plans available on the internet might be all there is. There is a book Black Sailed Traders and a few others. The LOA might not have varied much, so a direct comparison to a 48 ft boat may not be an option.

The reason I brought up the bugeyes is that they had similar hull lines driven by similar physical circumstances but at a later time and there might be more information available, certainly more lines drawings. The bugeye was the stepchild of over fishing, local building traditions and regulations. Dredging was prohibited in the fishery until around 1880 when dredging under sail was permitted in waters over 15 feet deep. The growing scarcity of oysters drove an increase in vessel size and the need to make money hauling freight in shallower water in the off season drove the shallow draft. So we have convergent evolution of hull shape for hauling freight in shallow water under sail along with a range of LOA and beam to look at. The rig was driven by bridges in Norfolk, but not in the Chesapeake. The deeper water over the oyster beds made room for the centerboard. Granted it is an indirect comparison.

My only argument about beam is that a bunch of guys did something different with the beam under similar circumstances, and there might have been a good reason. It could be that 2 feet of beam made for a larger hold. The book I mentioned was first printed in 1941 and has a list of length, beam and depth of hold for about 600 bugeyes ranging from mostly 40 to 80 feet. The author was looking to find information on every bugeye ever built. There is a brief summary of size ranges, number of boats built and a graph showing length over time. The beam varied roughly linearly with the length, around 3.6 to 1. a 58 ft boat would have a roughly 15 foot beam and a 48 ft. boat about 13 feet. The builders in the Chesapeake would not have tended to go as low as 11 feet beam on a 48 ft boat. If they didn't do the stability calculations, at least they settled on something that was working. Average length was 50 ft from 1870 to 1885 then ramped up to over 65 ft. by 1900 while the number of boats built dropped off along with the catch. Most building stopped around 1905.

 

Thanks Dave. I've read Black Sailed Traders, and there are a couple other books about wherries which I also have. The LOA varied quite a bit with wherries, and a 48-footer would not have been unusual. In fact, most wherries were not nearly as large as the two cargo wherries that still exist. Unfortunately, we don't have the plans for any of the average-sized wherries, and those people who actually saw the wherries are hard to find these days! As you say, it's likely that they rarely had such a narrow beam, because they wanted to maximise cargo space. But some smaller ones had to go through a lock at Dilham and their dimensions would have been restricted to no more than 50 feet long with a beam of 12'4". I suspect they would have used every inch of that, but hard to say. Another wherry had a narrow beam to pass through Old Wayford Bridge, but I've been unable to find out how narrow that bridge was as it was torn down many, many years ago. I have spoken with several people over the last week, and the general consensus is that if I ballast her properly (when she isn't carrying cargo, that is) and ensure that the sail area is scaled down correctly, my design will be perfectly stable. I've run some calculations as well, checking COG with metacentres, and at a heel of 9 degress, the metacentre is still about three feet above the COG. So I think the design is fine. Much less stable than the original, but still very stable, because those original wherries were like rocks, they hardly heeled at all, even when unladen. I sail on one of the traders on the Broads, so I have first-hand knowledge of that! So I don't mind less stability, as long as she is still stable, which everything points to her being.