Frégate la Cornélie 1795

[JohnE]

One of the main problems with getting older is that when parts break they are not only out-of-warranty, but also discontinued/out-of-stock. Have been under the weather for a time, but am able to get about a bit better and can’t imagine a more therapeutic exercise than rescuing my darling Cornélie from the bitter dust of neglect.

 

Things were looking good for her a year or so ago, but I was constantly troubled by teensy, tiny, niggling little inconsistencies that didn’t quite reconcile in all three orthogonal views. I ended up doing quite a bit of ‘reconstruction’ a la Chapelle and Merrit Edson. Getting back into the flow, I decided to refresh myself by going back to the basics, so I reexamined all the devis to make sure I didn’t do something stupid somewhere. Needless to say, that is just what I had done.

 

Rechecking the contents, in the miscellaneous pile, I found a set of pages with off-set tables stuck in with the tables of scantlings, iron work, and sparring. The pages were titled ‘Errors’ and had lovely columns comparing off-set values from a devis with values from a master design plan. Wouldn’t you know it, an out of order page begins with “Erreurs du Devis et du Plan de la frigate la Justice, envoyé le 14 Mars par M. Sané” and includes all the column descriptions and explanations for the different measurement methods. Lovely things like “le devis donne … le plan donne ….”.

 

It puts a descriptive name to the 7th lisse (diagonal ribband), rentrée, relating to tumble home, something that was part of the old heartburn. Playing with it, in this context, I found that it represented the region where the frame outline running batten has an inflection point, going from convex to concave. Combining this epiphany with the corrected off-set values resulted in curves that were not only more correctly implemented, but also exquisitely elegant. The tumble home now looks like ‘la taille élégante incurvée d'une jeune fille’ as it should.

 

In another development, Gérard Delacroix let me know of a ‘design of the stern decoration of Cornélie’ available from Service Historique de la Marine. As soon as it arrives, I will have a plan of the stern to go along with the beautiful figurehead that David designed for her. Everything seems to be falling into place. It’s almost scary … I’m waiting for the other shoe to drop.

 

Here is a pic of the revised lines of the body plan. The corrected stuff is way more svelte and, yes, elegant. The left (aft) side is as it originally was and one can see the difference between the grace of the 1795 curves compared to the straighter, more utilitarian, shapes of the later classes (i.e., Pallas) formalized in the 1810 regulation. The corrected aft master is on the body plan (in green), so if one looks closely, one can see just what a better understanding of measurement point meaning gets you.

 

Working on design of the master couple, disposition of frame, and framing the bow, stern, keel, apron, deadwood, and bears, oh my! More to come; slowly, but it will come.

 

John

 

Edited July 31, 2017 by JohnE

[JohnE]

Ok, here she is. Boy, oh boy, those plan corrections sure made the afterbody look lovely. Obviously, going to have to do the John magic again and design in the last full frame IX and do the adaptation of the estain from faired buttocks. Fiddly bits. Current state is just right for the profile plan of the keel assembly, bow and stern assembly, and fore and aft massifs. That leads directly into the disposition of frame. Wonderful progress.

[CaptArmstrong]

Looking just wonderful!  Having a plan that is so clearly and accurately the standard lines of the class as they were meant to be is really a treasure!  

 

I do like what you've done with the decorations on your plan, but I'm really looking forward to seeing what the design of the stern was as ordered! Though if you've seen any other such carving plans for french vessels, I'm sure you're aware that it may turn out to be more of a guideline to be interpreted by the builders at the yard rather than an exact match to the dimensions of the ship. 

Edited August 5, 2017 by CaptArmstrong

[JohnE]

Hello, Capt and thank you.

 

I’m looking forward to it myself. All I originally had was just a few sentences of description in a general catalog listing. It was enough, barely, to suggest an approach for the figurehead. All it said was the figure ‘holding a vessel with the flamme sacrée’. So Hestia came immediately to mind and Cornelia, after all, was the epitome of family virtue and righteous Roman motherhood. David took the idea and ran with it. He even has ‘her hair bound in Roman fashion’. It’s gorgeous.

 

The description has the stern carving as Cornelia with both arms extended, one refusing the riches of Ptolemy, the other embracing her children (the Gracchi). Who knows what is shown on the carving detail, or what was done in actuality. Cynically, but realistically, it was probably something like what the Virginie ended up with, crossed flags and cannon, with a prominent phyrgian cap hanging off a spear or crossed fasces. Boring. The Directory was a bit too liberté, égalité, conformité for my taste. Things likely had a bit more flair in the Empire.

 

But then again, who’s to say, really? Even if the carving plan shows the usual Republican ‘stuff’, there is that listing in the catalog. I will take that as a historical grant of poetic license. Big grin!

 

Ciao. John

[JohnE]

Ok wood. This is exciting. Keel, keelson, bow assembly, stern post assembly, deadwood, and disposition of square frames, completed. What's left to do is loft the bow and bollard timbers, loft the fashion frame and filling transoms, and cut their mounting steps in the fore and aft deadwood. Positioning the square frames determined the placement of their steps on the keelson, so that's done. Things look very nice from VII forward to VIII aft.

 

Quick word on the bow construction pieces. Vial du Clairbois shows individual pieces comprising the bow on 4 separate large Plates. Each Plate shows a very different arrangement and orientation of the timbers. All I can conclude is that these elements (or many of them, at any rate) constitute fiddly-bits. He makes certain position recommendations in the text (which I follow) but the central, generally triangular, area seems to be a terra permisio, where just about anything goes depending on what's in the woodpile at the time. All the pieces are about where they are in at least one of the drawings.

 

It's getting really close to sawdust time. I can forsee starting a scratch build log in the not too distant future.

 

[CaptArmstrong]

If I remember what  boudriot wrote correctly, the decorations for frigates were officially standardized during the ancien regime about 1785. The decoration plan for this order is reprinted in history if the french frigate. It is structurally very chunky, without much thought to how the stern was actually framed. It seems that quite rightly no constructors followed it in this regard, but the influence of its  motifs and some of the layout can be seen on a number of frigates of the 1780s and 1790s, and I think this accounts for the standardized, slightly more austere look you describe. But there are enough examples of frigates from this era with proper figureheads (rather than the arms of France, or later a Phrygian cap)  that it seems quite plausible that the cornilie was built with the carvings described, and that the plan will show them

[JohnE]

More progress. The spine is pretty well settled in; keel, bow, stern, deadwood. To finalize things, I had to make an executive decision on the sided dimensions of frames/couples. Room and space is a simple calculation; station spacing is 101 pouces, there are three filling couples per station (except extreme forward and aft), so room and space is 25 pouces, 3 lignes. All I had to do was determine the frame siding.

 

The kinda, sorta, "rule" from the echantillon is 9 pouce 6 lignes. However, this does not correspond with measurements taken by the British off captured Sané frigates. The majority of frames measured out at 9 1/2" which converts to 9 pouces. At least one vessel, albeit built in Venice, had frames sided 9" which is a skoosh less than 8 pouces 6 lignes. Everyone agreed that the Venetian vessel was lightly built and notably departed from the French standard. So is typical frame siding 9 pouces, or 9 pouces 6 lignes? Well, I split the difference. Frame siding is 9 pouces 3 lignes, giving a couple siding of 18 pouces 6 lignes, and a spacing of 6 pouces 9 lignes. It is basically a 13.5mm departure from the "rule" at full scale.

 

Anyway, that's the story. Next on the do list is loft the hawse and bollard timbers. That will finish l'Etrave. Last is loft the stern assembly. I am marshaling all the curses I can find in every language I have ever heard of, since I know that the infamous compound curvatures of the fashion frame and filling transoms are waiting to bite me in the butt, again, and I need to be prepared.

 

Ciao. John

 

[JohnE]

The stern lofting of Cornélie is pretty well finished and golly, does she have lovely looking buttocks.  Fashion frame(s) and filling transoms fair in nicely and the surface differentials, for defining the wood’s shape and curve, are complete. The remaining step is to position it all on the massif and define the pieces of the deadwood, and their curvatures. Whew! That was hard! Well, not so much hard as incredibly painstaking.

 

I got inspired by the 3D work done for the Swan Group by their European mystery guest. I am trying some of the same techniques to get rabbets looking right and get good plots of cutting-down lines, etc.. The goal is to have the plan set that includes a synthesis of benchmark lines representing both French and British practice. Much of what people are used to seeing on British plans seems to be missing somehow from the French equivalent. However, it is probably better to say that certain information is not necessarily missing, but is rather presented in a completely different manner. So why not combine the two? CAD is so cool!

[JohnE]

Thanks for the likes. I was a bit remiss and forgot to put up some pics. Here's some of the guidelines for the lofting. This part makes sure that the lines are ok in all three views and everything checks against the Devis. There are a (very) few places where the Devis is inconsistent by a (very) small amount, but they are all in the fiddly-bits category. All things considered, she's coming along beautifully; everything is falling right into place. That means it's time to be extra careful so I don't get bit in the Coulomb.

[dak4482]

Hi John,

 

New to the forum. Please be patient as I'm also new to this hobby though have read extensively but not put it to practical use. Looking over Boudriot's drawings of the head it appears that the gammoning holes are much higher on the knee of the head in his French vessel that what I see in Steel and other British and American drawings that put them between the cheeks??? (Am I describing those correctly)??? Are the rails positioned differently in the French vessel? Or is Boudriot's Illustration just not absolutely horizontal and is distorting the picture to make them look much higher?

 

Thx in advance.

 

Dan

[JohnE]

Hello Dan,

 

French gammoning hole positions are often different from British practice. Boudriot mostly places his in the fill piece (garniture) between the cheek curves (courbes de jottereau) as you note. There is no 'rule' per se, and I have seen different designers position them in different places. Vial du Clairbois just says "make sure there is good purchase". It's no surprise that the French rig out different since their bowsprit steeve is 30 some degrees rather than the British 22 or so degrees, at least for frigates.

 

Hope this helps.

 

John

[dak4482]

John,

 

Thx. Flipping between Boudriot and Steel is sometimes very confusing. Steel gives very good narratives but his diagrams leave alot to be desired. Boudriot has great diagrams that help you understand the narratives, but his narratives are not very detailed. Even though completely different styles of architecture I'm still using both just for understanding some of the technical aspects. Gonna try and start with Rhino to give a very rudimentary try at diagramming a ship hull. I'm not looking for great accuracy, just trying to understand the miriod of lines and terms in the various diagrams. Also Rhino allows tracing to shape out the beginning of the design. Steel's Naval architecture and the Shipbuilder's Repository are so deep I figure if I try drawing out the descriptions little by little, even if not very accurate it will help understand them so when I am looking for accuracy I'll make fewer mistakes. Thx again. The forums here are a HUGE help also. Thx to all you "experts" out there that contribute these great narratives that help so much in understanding ship design.

PS. Any other good French Naval architecture sources that have been translated to English?

 

Dan

Edited October 7, 2017 by dak4482

[JohnE]

19 hours ago, dak4482 said:

John,

PS. Any other good French Naval architecture sources that have been translated to English?

Dan

Unfortunately, no. The Mungo Murray treatise includes an abridgement of parts of Elemens de l'architectue navale by Duhamel du Monceau, but I think that's about it. So far as I know, Olivier, Ozanne, Morineau, Monceau, Forfait, Clairbois, Lescallier, even de Freminville, have not been translated except privately.

 

John

[druxey]

There is an English translation of Ollivier by the late David Roberts, published by Jean Boudriot Publications, ISBN0-948864-11-7. You may be able to locate copy on abebooks.com but it will be pricey!

[JohnE]

Thanks Druxey, that's nice to know. Speaking of translations ... had to do quite a bit of Vial du Clairbois for the lovely Cornélie.

 

The compound curvatures of the fashion frame (estain) and the filling transoms have always been quite painful to get right. The main reason is no one has done those for a Sané design before, so there is nothing to use as a guide or make intelligent judgments from. The British didn't take off enough lines in the right places to provide a suitable guide, and even the lines in the Chaumont Papers are way too few and far-between, besides being completely unidentified. Woof! Everything was a guestimate, and wrong, as it turns out. I had to go back to the well.

 

Vial has a section on this. Very informative, but superficial, and lacking in the very details that I needed for a proper understanding. Then I just happened to open Vol II. I had previously assumed Tome II was simply an 1805 retitling and reprint of Tome I with some additions. Wrogn again! I was fooled by the totally similar table of contents. Turns out that Tome II begins where Tome I leaves off. Seems that Tome I is the undergrad book having all the basics and sufficient gloss to get one started. Tome II, however, is the graduate level "design and construction theory" course book. Every section begins with the assumption you have Tome I open to the appropriate place and the Tome I drawings are at hand. Then it launches into detail ... thought I would have a heart attack! Woof!

 

All right! Design the darn things from scratch! This is better than buttermilk pancakes! So I did. And it worked. And it didn't just work, the lines flowed directly into those of the well documented sections from Sané's devis. My estain was a bit off in body plan and profile views, and the waterlines and buttock/bow lines behind the estain needed considerable adjustment. Before, they were smooth, but arbitrary. Always subject to tweaking back-and-forth depending on which curve I started with - body, waterline, diagonal, ...

 

Finally, after much sturm, drang und todesangst, I really think I have an understanding of French stern construction. Some pics. Waterlines (level lines) just flat look good. Not just that, but they grid out such that each level-line point projects right smack dab where it is supposed to on the profile buttocks and body plan, and arsey-versey.

 

All this was the basis of the loft of the filling transoms. Easy peasy once the surface was completely defined.

[JohnE]

Something else that happened is I was able to import quarter-beam and mid-beam lines into the MATLAB hydro program and evaluate the curves for performance. Turns out that Jacques-Noël knew exactly what he was doing. They fall within acceptable modern parameters. Howard Chapelle and Merritt Edson would approve.

 

It also becomes apparent why French ships (although can only speak to Sané types) were so sensitive to trim in order to get most out of their performance regime. The lines purty near say outright that if they have a bit too much load drag, or sailed with a squat, they will suffer and become sluggish, like a lovely lady on the arm of a boor.

 

The kicker comes from Sané's famous 6 inch stretch after Villemaurin's sail trials in the historical Cornélie. Villemaurin noted stern trim sensitivity in great detail, load trimming both up and down, altering mast rake, and the sail suite. It told a lot to Sané. All of the stretch was put from Frame VII aft. Frame VII stayed where it was in the Venus (Hébé) and Virginie series. Frame VIII moved 3 inches farther aft from Frame VII and the aft perpendicular moved 3 inches farther back from Frame VIII. This centers the majority of the stretch smack dab in the region where the quarter buttock crosses the load waterline and stretches out the buttock lines in this area so they are considerably straighter.

 

I was amazed at what a simple 6 inches could do, until I realized that the difference between the "right" design curves and my "wrong" ones were the matter one inch or less, back and forth, up or down. Whoda thunk?

 

Wonder what Jacques-Noël would have done with access to a CAD program. I shiver to think.

 

Ciao. John

[druxey]

Those lines look sweet and lovely, John. Your description of getting there is laugh-out-loud funny! I guess not so much for you, though. Well done.

[JohnE]

Thanks all. Have to admit that I had some frustrating periods, but once the lights came on the journey became a lot of fun. Only wish I had known this sooner when poor Mark was having such problems with the stern of his Licorne.

 

Herask and Bava are both encouraging me to get up to speed in Blender so I can do visualizations in 3D. They are really helping me focus the learning curve. The ability to see a complex piece of wood and how it fits with the other pieces, before I pull out the saw, will be I think invaluable.

 

Ciao. John