French Protected Cruiser COSMAO 1889

[setori]

On COSMAO1889C015.TIF you can see that D is C shaped girder.
Concerning A B C you may be right, the cover can be metallic

[taylormade]

More work on the bow searchlight platform. Anchor cranes roughed in. Thanks to all for the feedback and to setori for the suggestions and comments.

[DrPR]

Was the companionway actually on the center line? Or was it to one side of the searchlight platform?

Looking at your profile drawing the aft searchlight platform supports (C and below) might not be a part of the companionway.

Also, these things were on the bow, where they would be subjected to significant waves in heavy seas. Either they would be very substantial, or they would be removed when at sea. Especially the companionway cover.

The rectangular thing around the searchlight was probably a circular shield/bulwark to protect the searchlight.

Those are my guesses.

This is an interesting project.

Phil

[taylormade]

I agree that the searchlight platform seems a bit flimsy as designed. The front pole supports don't look all that substantial in the plans. The companionway was definitely on the center line as you can see in this cross-section of the plans.

If you look closely at these two drawings you can see angle iron supports on the companionway cover that support the rear of the platform. There is no other support shown in the plans.

In this top view you can see the rear of the platform is against the companionway structure. There is some problems in the plans, as the top view and side views don't match up. At the moment, I have to add a rear extension to the platform to get it to agree with the side view - but that extension doesn't appear in the top view. Still noodling on that problem.

[setori]

I have transfered the plan view on the side wiew, and I think they match

[taylormade]

I've come to realize that these plans, although valuable for the wealth of information they do provide, have some serious problems when it comes to accuracy. Here are three side views of the bow area taken from different plans sheets. In black, blue and red you can see many discrepancies in scale, position and shape in the drawings. In the end, I suppose you just have to make an educated guess as to what was really there.

And here's another conundrum - which view correctly shows the pattern of the planks on the searchlight platform? I think I'll go with the more complicated version as it comes from a more detailed plans sheet. I'll have to change what I have, but I hope the revisions portray a more accurate picture of the Cosmao.

[taylormade]

I think this is about as close as I can get. I'll start on the crane details tomorrow.

[DrPR]

Looks like you have figured it out pretty well.

Phil

[taylormade]

I need some help with the configuration of the anchor cranes. In the view below A is the top of the pulley area. There are three pulley wheels inside as can be seen from the top view from the plans. So this is a typical block and tackle setup.

I assume this used heavy rope with the crew and a steam capstan pulling the anchor up. Was chain ever used in this setup?

Arrow B points to a device on the crane. Any idea what this was used for? Possibly a pulley to guide the rope and deliver more of a straight shot off the crane?

Arrow C points to the shaft for the three pulleys. Are the two loops on the ends for a rope to rotate the crane and pull it into position?

And, finally, any clue as to what arrow D is pointing at?

I've searched for pictures that might show this type of setup. but I'm having no luck.

[taylormade]

Finished the crane with the exception of the lower tackle. Added handrails. Things are starting to look a bit more busy.

[taylormade]

[DrPR]

The things with the "pulleys" are called blocks. The rotating parts the rope goes over are sheaves. A collection of blocks and ropes is called a tackle or purchase.

I wouldn't call the image you posted of the tackle a "typical" arrangement. The standing (fixed) end of the line seems to run though a hole in the lower block and is secured by a knot through the black plastic piece. I have never seen this arrangement before. One of the three sheaves in the lower block is not used, sacrificing mechanical advantage. My guess is that the photo was made by some advertising type who had no idea how to rig tackle and was too dumb to look it up.

Normally the standing end would be attached to the upper block and run directly to the lower block and through a sheave on one side of the block. Then the rope would lead up to the same sheave on the upper block, down to the middle sheave on the lower block, up to the middle sheave the upper block, down to the third sheave on the lower block, up to the third sheave on the upper block and from there the fall (loose end) would run out to be pulled upon. All three sheaves on both blocks would be used.

An alternate method is to rotate the two blocks 90 degrees to one another as in this triple purchase image:

The important point here is that the fixed end of the rope is attached to the upper block, or to the crane, and then immediately run through a sheave on the lower block. All sheaves are used in both blocks. And none of the running parts (lines between sheaves) cross or rub against another part of the line.

In your case the sheaves in the end of the crane serve the purpose of the upper block. The standing part of the line would be attached to the crane. The red arrow to C passes in front of something on the bottom of the crane that looks like a ring where the standing part of the rope could be attached.

It looks like the thing at B in the drawing is a single sheave mounted in flanges on the boom. It offers no gain in mechanical advantage but allows the direction of pull to be redirected to a capstan elsewhere on deck.

The thing at D could be a cleat to fasten the fall from the tackle to.

The rings at C are where "vangs" (ropes or tackle) attached to pull the crane around it's vertical rotation axis. The rings you have drawn look too large to me. All you need is a small ring that a rope or shackle can be passed through. Often the rope end would be bent back upon itself and lashings added (or a splice) to form a "eye" in the end of the rope. Then a shackle would be used to connect the rope eye to the ring on the crane. However, instead of using the shackle the free end of the rope could be passed through the ring on the crane and secured with a knot.

Chains can be used with blocks and sheaves designed for chains. But in this case I think rope would be used because it is difficult to get chain to wrap around a capstan or winch without it slipping. Rope gets a better grip on smooth metal surfaces.

Phil

[taylormade]

Thank you for the detailed information. Obviously my knowledge nautical terminology is limited and is not helped by these plans being in French. I seem to have, by pure luck, figured out the basic operations of the anchor crane and you have nicely filled in the rest of the information. I also thought the vang rings looked too large, giving sort of a Mickey Mouse ears effect, although I sized them directly off the plans. As usual, in another view they are smaller, so I'm going to reduce the size. The information on the block and sheves was very useful, but modelling the ropes will be a real pain. Thanks again for the help.

[DrPR]

"Real pain" is an understatement! My CAD program has no tools for modeling ropes, etc., except extrusion along a curve. It takes a lot of trial and error - and patience - to get it right. Knots are the most challenging!

Phil

[taylormade]

Done for the day. As I feared, the ropes were very difficult. I'm looking forward to the simplicity of the deckhouses.

[wefalck]

On the anchor crane:

- a typical heavy-duty arrangement seems to have been to have three sheaves on the crane and a two-sheave block with large hook; the rope would be shackled to a ring on the iron strap of the block, from there it runs up to the first sheave of the crane, down to the first sheave of the block, back up to the second sheave of the crane, down again to the second sheave of the block, up again through the third sheave of the crane and finally down the back of crane over the guiding pulley; it would be belayed on a cleat there. This is the arrangement in your case.

- a lighter duty arrangement would be two sheaves in the crane and a two-sheave block; in this case the rope would be shackled to a ring near the sheaves of the crane.

Nice 3D-modelling, btw.

[taylormade]

Thanks, my first foray into a nautical subject so a lot to learn.

[taylormade]

The Foredeck is coming along. Just roughing in the bridge which is currently floating on its own. I've read that the ships in the Mediterranean had black hulls with buff topsides. I assume this would be the deckhouses, vents, funnels and skylights. Any thoughts or ideas? Oh, that floating searchlight will end up on the soon to come gun sponson that juts out from the hull.

[taylormade]

More work on the deck. Bridge near completion. Was there a second wheel in the pilothouse? It must have been a bit cold out on the bridge in the North Atlantic.

[wefalck]

It wasn't colder than on the sailing ships of old, where there were no wheelhouses whatsoever - it's just that the seamen have become more whimpish

One should be able to see, where steering wheels may have been placed from the run of the rudder-chains and -rods, if these have been drawn.