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Plank length for longboats


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I am working on the Chaloupe Armée (plans and booklet from M. Delacroix) and wonder what the standard plank length would be for the outer hull planks of this 42'8" longboat of 1834. The model builds that I have seen just place planks that are the full length of the boat, but at full scale I would have thought that 42ft would be too long. As far as I know, the normal plank length for larger ships would be 20-24', but would welcome any thoughts on how French longboats of that period would have been planked.

 

I have the book 'The Boats of Men of War' by W.E.May, but the scantlings given in that book don't seem to give plank lengths. I have also looked at Chuck's Medway Longboat build and there he does provide two planks for several strakes together with a butt shift which suggests to me that this might be normal practice.

 

As usual, I apologise if this question has already been dealt with but I couldn't find it in the forums so far.

 

Thanks

 

Tony

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Look in Mays book and you will see an original draft of a longboat with a planking expansion.  That is where I took my planking scheme from with a little adjustment to make it easier to plank in kit form.

 

You should start a build log for this......this is a great scratch project to watch as it develops. :D

 

Chuck

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Fincham: That's very interesting. I certainly had not expected that such lengths would be used. Thanks.

 

Chuck: Thanks very much for pointing that out. I had missed it as I just went straight for the scantlings and didn't take the draft into my consciousness. I'm having second thoughts about breaking the planking into lengths as it would mean I have to put the butt ends on 2mm frames. I'll continue to think about it though.

 

As for a build log, I've been hesitant. If I do one it'll be more for how a novice gets to grip with the trickier elements (much as I've done in my previous build logs). There are already some excellent build logs on the web for the Chaloupe, although only one goes into the details of the construction (and that's only in French). However there are enough puzzles to make a log interesting -- a notable one being the use of 2mm frames when the plans show something more complex.

 

I have reached the stage of putting the wales on the frames and am about to start planking (hence my interest in the lengths). Thanks for the encouragement, though, Chuck!

 

Tony

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12 minutes ago, MEDDO said:

Would also like to see a build log for this.  

 

Tony, are you going to rig this?  M. Delacroix also sells the sail and rigging plan for this on his site.

I do have the rigging plan, which came with the book of Le Rochefort by M. Delacroix. I'll make my mind up about that once I get to near the end of the basic build. As to the build log, well, I can see the interest, but if I do it'll be more about how to struggle through and all the choices that are made. It certainly won't be perfection!

 

Tony

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Thanks, Mark. I have seen those builds. Rob's (Decoyman) was indeed helpful. From my point of view (i.e. related to my needs as a learner), the very best is the one by Jean-Jacques Herault at http://modelisme-arsenal.hlt34.fr/journal_de_la_chaloupe_armee_007.htm.

 

I agree about the fact we're always learning, whatever the level, and that build logs allow constructive advice and criticism. Indeed my previous builds benefited enormously as a result. I'll gather up my thoughts and will probably go for it! Thanks for the push!

 

Tony

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34 minutes ago, tkay11 said:

Chuck said: Look in Mays book and you will see an original draft of a longboat with a planking expansion.  That is where I took my planking scheme from with a little adjustment to make it easier to plank in kit form.

 

Fincham states that the planks from foreign oak are up to 42 feet long. That are planks for ships bottom. Planks for boats have smaller thickness and width, so I think more length was also possible.

 

Fincham: That's very interesting. I certainly had not expected that such lengths would be used. Thanks.

 

Chuck: Thanks very much for pointing that out. I had missed it as I just went straight for the scantlings and didn't take the draft into my consciousness. I'm having second thoughts about breaking the planking into lengths as it would mean I have to put the butt ends on 2mm frames. I'll continue to think about it though.

 

 

Tony

 

While relatively thick oak planks over forty feet long may have been used to plank large vessels early on, they must have come from what would have been those rare specimens which were not only large, but also suitably shaped, domestic oak trees. The huge impact of England's shipyards on the forests of not only England, but of the world, is a fascinating study in itself. See: (http://www.wou.edu/history/files/2015/08/Melby-Patrick.pdf ) I would expect that England had probably consumed most of the available oak trees capable of yielding forty+ foot straight, vertical grain planking stock by 1700, if not before.  Such trees take 150 to 180 years to become harvestable. The Royal Dockyards were consuming oak faster than England could grow it. Britain was importing timber as early as the 13th Century and by the mid-Eighteenth Century was importing "deal" (planking stock up to eight inches wide and 20 feet long) from the Ukraine, Poland, and Norway, and by the end of the Eighteenth Century from her American Colonies which produced sufficient mast stock to permit abandonment of "built up" masts for a time.

 

At the time of these longboats, oak would be used primarily for structural timbers in small boats. They would be planked with softwoods, likely larch imported from the Baltic states. Long lengths would likely be reserved for spars, while second-choice timber would be sawn for deal, planks which rarely exceeded 20 or 24 feet in length.  In any event, the length of planking is limited by the shape of the plank. Small boat planks are necessarily curved to fit the shape of the hull. The more the curve, the wider the stock it's cut from must be. Getting a sufficiently curved exceptionally long plank from a single piece of stock requires that the stock be wide enough to be able to saw the curved plank out of it. The longer the curved plank, the more wood is wasted. Moreover, the more the curve, the weaker the plank becomes since there will generally be grain runout at either end. So also, the wider the stock, the more problem with cupping and the longer, the more problem with twist. My guess is a vessel the size of these longboats would be planked from 20 or 24 foot larch stock. 

 

While the practice in vessels with large frames may have been to butt planks on the frames, the practice with smaller boats with smaller frames would have been to employ butt blocks placed between the frames so as to avoid weakening the frame with the plank fasteners. Unless there is some reliable contemporary evidence to the contrary regarding their use, I'd consider properly placed butt blocks to be an essential detail in a model of this scale. I wouldn't necessarily rely upon a contemporary model for such a detail, however. The model could easily be planked without planking butts and the placement of butts was always at the builder's discretion, depending upon the planking stock they had available, so butt blocks would not have been a feature necessary to depict on a contemporary builder's or Admiralty model. I don't have the Mays book Chuck referenced, but from his description, I understand "planking expansion" to me a draft of the plank spacing, but not the specific placement of plank butts. (The standard schedule for butt separation is well documented, of course.)

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Thanks very much, Bob. A very logical analysis. Good point about the butt blocks.

 

I attach the illustration from May's book which is for a 23' longboat of 1758 and shows the shift of butts. It states that this was the size that became established for larger frigates in 1769.

 

Interestingly, even though it's only 23' long the planks shown are in the region of 12' long (according to my measurements of the scanned page, but also pretty obviously just from eye-balling).

 

Tony

Longboat planking - May.jpg

Edited by tkay11
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Looks like they fall on the frames too. In any case you can always plank with full length stock, and scribe in the butt joints as each plank is in place, but before the next is laid. If using butt blocks, they can be glued in opposite the scribed joint. Saves trying to do it with shorter lengths.

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16 minutes ago, thibaultron said:

Looks like they fall on the frames too. In any case you can always plank with full length stock, and scribe in the butt joints as each plank is in place, but before the next is laid. If using butt blocks, they can be glued in opposite the scribed joint. Saves trying to do it with shorter lengths.

That's funny, Ron, because last night I had exactly the same thought! I think that's the way to go.

I've just started my build log, by the way.

 

Tony

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