Jump to content

Recommended Posts

Another question regarding brigantine Leon, 1880, Norway. 302 tons.

 

What kind of mast step was she likely to have had?  I am learning that there is very little information on this subject.  There are three representations of mast steps that I have encountered - they all have a square tenon at the bottom of the mast:

1--  The first is that a square mortise in the keelson receives the tenon on the mast.

2--  The second says that they never cut the mortise directly in the keelson but rather in a thick block which is bolted to the keelson.  Sometimes an iron fixture might have been used.

3--  A much more complicated arrangement shown in the attached diagram is given as the most common arrangement designed to spread both the weight of the mast and the stresses over a larger area..

 

Considerations which make sense to me are that Leon being a relatively small ship might not have needed the complex arrangement.  And further when she carried coal it would make getting the coal out a little more bothersome.

 

Any thoughts would be very welcome.

 

Thanks,

 

Doug

 

PS the diagram comes from Crothers, American Built Packet and Freighters in the 1850s

Mast Step.jpeg

Share this post


Link to post
Share on other sites

I'm surprised that Underhill, who I don't doubt, found that Leon only had a block on the keelson. Given her size, I'd have expected that she'd have had a properly built up step as pictured above, for the mainmast, at least. I also note that the drawing above omits the limber holes in the knees and the bottom of the mortise. That tenon isn't something you want rotting away on you!

Share this post


Link to post
Share on other sites

Duff and Bob,

I think we are allowed to question Underhill on this detail because I do not believe he knew what the specific internal details were for Leon.  I believe he goes with usual practice or such.   I'll give an example,  we now know that Leon had four hooks forward (3 of wood and 1 of iron) and 2 aft (1 of wood and 1 of iron), which seems a lot for a relatively small ship, but Underhill only mentions one forward joining the beam shelves.   We now have a DNV survey from 1880 which is gradually being translated from Norwegian to English so for structural information we should be in pretty good shape.  Bob, it is interesting to me that you imply that Leon is a pretty good sized ship.  I've always thought of her as being small. Oh, btw, when you say mainmast, I assume you mean the square rigged foremast.  I don't quite know how to ask this, Bob, but can you give me any info on how you make the judgement that "given her size, I'd have expected that she'd have a properly built step."

Share this post


Link to post
Share on other sites

I am surprised that Underhill was as precise in his mast step mortise - going so far as to cut it at the mast slope angle.

Not much room for adjustment there.  I like the old technique of fixing a cut off nail tip into the bottom of the mast

so that minor adjustments can be made and the mast not move.  I would think that the actual mortise f&a would be over size

and wedges used to hold the tenon.  That would allow the captain to alter the mast rake as conditions change.

Share this post


Link to post
Share on other sites
Posted (edited)
On ‎10‎/‎4‎/‎2018 at 4:43 PM, Doug McKenzie said:

"...  Bob, it is interesting to me that you imply that Leon is a pretty good sized ship.  I've always thought of her as being small. Oh, btw, when you say mainmast, I assume you mean the square rigged foremast.  I don't quite know how to ask this, Bob, but can you give me any info on how you make the judgement that "given her size, I'd have expected that she'd have a properly built step."

I only referenced a comparison between Leon's size and what I would expect to be the scantlings and construction of a mainmast step of a vessel of her size, type, and "modern" build. Like a lot of things where "size matters," our assessments often differ because they are necessarily relative. Obviously, your mileage differs. :D 

 

In addressing the mainmast, I intended to signify nothing more than that it was presumably the largest mast step on the vessel. My reference to a "properly built step" wasn't artful. I meant to convey a "a proper built up step" without implying there was anything wrong with a mortise block on top a a keel or keelson in much smaller vessels than Leon.

 

My assessment was based on over fifty years of exposure to mast steps in full-sized wooden vessels of many types and the stresses mast steps are  designed to withstand.  In Leon's case, I'd expect to see something more than a mast simply stepped on a mortise block mounted on top of a keel or keelson.  Of course, if contemporary data on this specific vessel has become available since the time of Underhill's writing, that should resolve the question. I was being polite in giving Underhill the benefit of the doubt as to accuracy. In recent times, the historian's caveat that "scarce information isn't necessarily accurate information" has been proven time and time again. I think there are two factors at work in this respect. 1) In earlier times, the standards for accuracy and completeness probably weren't as high as now. A lot of blanks were filled in with assumptions and guesses. and 2) There were so few interested in recording and addressing the data that there was nobody to "proofread" their work product. For example, this is a big issue with the HAMMS data, much of which comprises of lines taken off or copied from earlier incomplete drafts by unemployed non-maritime surveyors and draftsmen in the course of a WPA "make-work" project the inaccuracies of which, at the time, were of far less interest, and certainly far less consequence, than now.

 

The original poster offers a drawing from Crothers' book, American Built Packet and Freighters in the 1850s,  noting that "A much more complicated arrangement shown in the attached diagram is given as the most common arrangement designed to spread both the weight of the mast and the stresses over a larger area."  I doubt that the fact that Crothers was addressing mid-Nineteenth Century American construction practices and that Leon was built in the late Nineteenth Century in Norway would make much difference. Crothers' report has been my observation as well, although my experience is negligibly authoritative compared to Mr. Crothers' academic research.

Edited by Bob Cleek

Share this post


Link to post
Share on other sites
Posted (edited)

Bob,

 

When I asked my question I never dreamed that I would get so much information and perspective in return.  My thanks are hearty and I would love your impression of a two part proposal of mine based largely on your response.  As you most likely know I am am exposing the interior of Leon in my model.  Accuracy is of course the major issue.  but where certainty is not possible, informed judgement is next best so part one of my two part proposal is that the square rigged foremast gets the built up step based on your informed judgement.  Regarding the fore-aft rigged mainmast - if we cannot make a judgement that it also should get a built up step (either because it's stresses would warrant one or because it was common practice (?) to make all mast steps in one vessel the same type) then I would vote (i.e. the second part of the proposal) for using the simple step for the reason of displaying variety to the viewer.  Speaking for myself before embarking on this research effort I had no idea that a built up step was ever used.  Seeing the two types in one ship would drive this point home beautifully to every viewer I think.

 

Thanks again,

 

Doug

 

PS I don't know if you've seen Leon's blog in the scratch built forum but if not it might be of interest to put this specific question into a larger context.

Edited by Doug McKenzie
add reference to blog in scratch built forum

Share this post


Link to post
Share on other sites

Doug, I'd hazard to guess that the odds of the two masts on Leon, or any other vessel her size, having differently designed steps is probably very slim unless we are talking about a vessel carrying masts of very different sizes, such as a yawl.  Once a vessel gets to a certain size, its heavier scantlings dictate certain construction conventions and Leon is certainly of that "certain size." (She's just over 100', IIRC.) As Leon was designed by Colin Archer, and intended to serve as a North Sea and Baltic cargo vessel, one would probably be safer presuming that the vessel was on the heavier built side than otherwise. Archer's design portfolio is relatively well-documented, I believe.  I'm familiar with his famous lifeboats and their derivatives, but not his larger designs. Naval architects being what they are, it's to be expected that their body of work will exhibit similarities in certain engineering features and mast steps would likely be one such feature. As a naval architect and ship builder rolled into one, Archer designed and built Leon in his own shipyard, so the likelihood of certain engineering features like mast steps being "stock features" repeated from build to build becomes even greater. However, the catch is that in the case of his smaller vessels, at least, there never were any construction details drawn. These were worked out on the loft floor and determined in situ, as it were. To make matters worse, reportedly, his draftsmanship is notoriously sloppy. Since he was running the yard, he didn't need to communicate with the shipwrights on paper as much as a naval architect whose drawings were going to have to be followed by a separately-managed and often remotely located yard would have. Copies of Archer's original drawings, such as they are, can be obtained from the Norwegian Maritime Museum's library in Oslo: Norsk Sjofartsmuseum, Bygdonesveien.  https://marmuseum.no/en/ 

 

A quick google search for plans of Archer's larger vessels on line turned up nothing, but I did come across one "for sale" listing of a yacht fairly recently built to Archer's plans as a replica of the original design. There were two photos of the mast step of this 23' Archer-designed sloop on line which clearly show what, for a boat that size, was quite a solid mast step designed to spread the load across the floors and frames as well as the keel itself. It appears to be of composite construction, with some of the knee structure of metal plate. Many other designers would opt for a mast step made of a mortised block fastened to the keel alone in a small sloop like this one.  Until you can finds the construction drawings for Leon, or at least for Fram, I'd say you'd be safest opting for the more complex, but more strongly engineered, type of mast step.  I wasn't able to copy the photos, which seem to be encrypted, but they can be found at https://www.woodenships.co.uk/sailing-yachts/colin-archer-yacht/  Conveniently, for our purposes, the mast step structure pictured is painted white.

 

 

 

Share this post


Link to post
Share on other sites

Well Bob, clearly two built-up steps are in order.  Particularly convincing is the yacht's built up step - if any designer/builder creates that step for a yacht there is little chance that a large fore-aft mast would get less.  I think that built-up steps scaled to the mast's diameter seems like a reasonable way to go.  Thanks for fascinating insight.

 

Doug

Share this post


Link to post
Share on other sites


An Outline of Ship Building , Theodore D. Wilson ,  1873

STEPS OF THE MAST ----  Steps of the mast are for stepping the heels o the masts in. At the present time, the fore and main masts, are stepped in cast iron mast steps,made to fit down over the main keelson, with a broad flange on the sister keelsons, to which they are secured. The Mizzen mast steps in a piece of live oak timber scored down over the berth or orlop-deck beams to which it is secured.
.......The foremast in the above-named, and nearly all vessels built up to that time, stepped in wooden steps, built up on the main ans sister keelsons.

 

A simple piece of timber just on the keelson does not seem adequate.

For the coal cargo.  The top of the knees could have been roofed over with relatively thin planking to keep the coal out.

It would not have required a major overhaul to alter the mast steps over the life of a ship. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

About us

Modelshipworld - Advancing Ship Modeling through Research

SSL Secured

Your security is important for us so this Website is SSL-Secured

NRG Mailing Address

Nautical Research Guild
237 South Lincoln Street
Westmont IL, 60559-1917

About the NRG

If you enjoy building ship models that are historically accurate as well as beautiful, then The Nautical Research Guild (NRG) is just right for you.

The Guild is a non-profit educational organization whose mission is to provide support to our members in their efforts to raise the quality of their model shipcraft.

The Nautical Research Guild puts on ship modeling seminars, yearly conferences, and juried competitions. We publish books on ship modeling techniques as well as our world-renowned quarterly magazine, The Nautical Research Journal, whose pages are full of articles by master ship modelers who show you how they build those exquisite details on their models, and by maritime historians who show you what details to build.

Our Emblem

Modelshipworld - Advancing Ship Modeling through Research
×