|Oct 12, 2009, 07:42 AM|
1842 Brig-of-war US Somers
After the success with my Footy Brigantine HMS Larne i`m inclined to build a bigger more scale ship.
The size is to be the same as Brooks Aldebaran due to the same considerations for ease of transport / storage fully rigged and also due to the scope of work/money involved to actually build her!
The scale set for my build is: 1:51 which is a nice size... a little tops'l sloop will be measuring still a nicely build-able 40cm on deck and a stately frigate 84cm... so there is good possibilities that later on i`ll build some more ships to that size
The Subject to be built is one of the US Navy Brigs of war of 1842 as i got a nice lines plan and sail plan for these ships.
So the decission was to build USS Somers..
Length on deck: 620mm
hight overall: 625mm
Length overall: 950mm
The construction method is going to be something i have not tried yet so we will see if it works
i`m going to use the buttock lines for templates, and cut them from 9mm thick balsa plates. glued together, and shaped should give a hull like carved. The whole thing is then going to get an epoxy coat inside and out. the keel will be a piece of 4mm ply. At the bottom of teh ship thee will be a cutout platform which will have ply at the bottom to which a Aluminum U-profile will be attached which will in turn hold the external fin keel.
i`m not 100% sure as to how many servos i`ll use... but the best guess is to use 3 normal size for sails and 1 small for rudder, so to have 1each for the main and foremast square sails, respectively jibs on the foremast and stay sails with the mainmast and an extra servo for the spanker.
So far i have concluded the Delftship modeling of the hull... next i`ll have to start printing and cutting the templates for the hull.
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|Oct 12, 2009, 11:46 PM|
Boy, you are mastering Delftship. Are you contemplating a Career Change? Seriously, maybe there are other modelers who would like buttocks lines/plates for builds of their favorite ships.
Comments on the deadrise: The more deadrise, the less displacement. You might calculate displacement to the waterline and see how that compares with your RC gear and proposed ballast. Aldebaran could not float the scale waterline and have sufficient ballast. Your hull will be lighter than mine, though, so maybe this won't be a concern.
Also, deadrise reduces the space below decks for servos, eg the quarters of the Aldebaran & Berbice were too shallow for the rudder servos, and I had to move them forward.
Make sure your deadrise + bulwarks don't constrict the size of the brace servo arms. Aldebaran struck a happy balance, fortunately. But I did have to move the higher of the stacked servos up to just under the deck to get enough width for the lower brace servo. I did not actually carve away all the deadrise shown in the Chapelle lines, and that was fortunate. Berbice would have had trouble there if John had not decided to make a flush deck ship, I think.
I think the feeling of the forum is that epoxy coatings alone do not add much strength. You need to add mesh, fiberglass or some sort of fabric, to get the strength. The fiberglass cloth for aircraft construction is superior to the cloth available at US hobby stores (hobby glass has a lot of filler). Aircraft Spruce is a good source in the US. If the interior epoxy is for waterproofing, a lighter option would be 2-3 coats of varnish, as I used in Aldebaran....and she certainly has given it a workout, hoho. Glue your maststeps, deckbeams, and servo mounts to the raw wood hull before varnishing for best bond strength. I covered the maststep holes with tape before varnishing: if they get clogged with varnish, it would be a bear to clean them out and preserve the mast rake angle.
|Oct 13, 2009, 06:43 AM|
I like your thinking - go for it (always taking brooks wise advice as you do so )
This year I have made two footys by this method, more or less from Prolines output (similar to Delft), I used 6mm thick buttocks - because I had a lot of 6mm balsa sheet and I also used 2 coats of Epoxy to finish the hulls (because I wanted the wood to be on show)
The builds are at
You will be welcome to any help I can provide (although I think your skills are a long way beyone mine)
|Oct 13, 2009, 07:27 AM|
Well there Brooks, you caught me there... when i designed micro scale planes i usually even got away with scale size stabilizers due to the fact that i usually choose benign designs and proven fliers to start with.. now reading Chapelles Book on Somers and Bainbridge the sister ship it says the following:
I enlarged the delftship model to 1:1 scale size to get some meaningful numbers out of the hydrostatic sections as the displacement volume is pretty much only given in mģ and tonnes and not enough decimal points to give results for our model sizes.
So my model displaces 2,058dmģ or 2,058kg at the scale waterline. So now i`m a bit stumped as to how much weight the ship will have and how much ballast i will need to actually sail her.
I was thinking along the lines of getting away hopefully with about 1200g for the ship and 800g for ballast to attain the scale waterline at 2050g displacement. The Hull will be plenty light even when glassed which i don`t think is actually necessary and if then mostly for "ding" resistance as the fiber is going to run lengthwise and spreaders like the holders for the masts and the servo platforms are going to take all the bending forces.
I read on your thread of Aldebaran that you are limited to 1lb (455g) of ballast on that hull due to high weight of the hull alone. Can you say what your ship now weights in sailing condition and how much of it is ballast ?
i`m right now in the progress of gluing together my full size sailplan so i can start calculating the Ce and area of the sails. I think we should end up with relatively comparable rig size on these 2 boats.
As to space constraints for the brace servos. I hope i`ll be able to get a 125mm (5in) length servo arm into there (thatīs what should be possible at 145mm beam. To get more sheet travel on it the idea is to make a disk instead of just an arm that works like a sail winch drum, so it`s not only the angular pull but the radial distance you get for travel.. So if i go with 160° of trevel for a streched servo i get a total brace travel of 175mm, should be sufficient ?
Andrew you don`t do yourself enough credit ! I got the idea to do this type of build from YOU And i really think you are an awesome footy builder!
|Oct 13, 2009, 08:13 AM|
I think my ship is about 5# (2.3kg) displacement, with 500g of pb. You can make any ship stiffer by making the fin keel longer, thus giving the pb a longer lever arm. The only disadvantage of a long keel is the need to wade out farther to launch her, and a slight? decrease in usuable pond area. I think your boat is doable at 2kg since your hull will be much less weight than mine (I had 1.5 kg in hull weight alone due to heavy wood and insufficient swamping out the interior wood, for contrast, Johns hull is only 0.5kg).
5" servo arms are great, no problem there :-) You won't need radial pull via a big disk, unless you want to try it anyway. If you rig your brig w/o the gaff trysail (the gaff sail shown on the drawing on the foremast), but with regular triangular staysails instead, there will be no interferance of braces and gaff (which is minimal anyway with 2:1 reeving and 5" servo arms on the Aldebaran). I have triangular staysails on Pamir, and she uses pure paralellogram at 1" centers from the hull centerline - the braces would only constrain the staysails on a reach, but since they are belayed for a beat only, the problem never comes up. Staysails, because they work in downwash, are sheeted almost on the centerline to keep them from backwinding. I don't know how useful they are, most of their lift would be heel only.
I would not worry too much about "critical hull" or low stability. Almost all real ships are that way. They have a critical heel angle, after which they will not self-right. This was more of a problem for fast sailing ships than for modern motor vessels since sailing ships are always heeled much more than motor vessels. The sailors handled the problem by reducing sail to reduce heel. I do the same with my squareriggers. The critical angle of HMS Endeavor was 46deg, I was told. We reached 44deg in a Bay of Biscay gale, and were in some danger, I later learned *grin*. She had a low deadrise hull, practically a bathtub :-).
We use fin keels, and our model ships are always self-righting (or can be built that way with a deep enough keel). So the critical angle is not a problem. The effect of deadrise is to give the hull a great deal of initial stability, if there is enough beam, and Somers looks good there. Think of a 2x4 floating. The 2x4 (=deadrise hull) has great recovery from a heel, up to the point its heeled 91deg, then it capsizes. Our fins & pb give us a critical angle of >90deg. so we should never have a problem (unless big waves flop us over, or the sails dip underwater to leeward on a knockdown, and the drift of the hull levers her and she turtles).
|Oct 13, 2009, 02:09 PM|
Neat rudder whipstaff that. I wonder who did it
Hang the overcanvassing, Mr. Meatbomber, shake out the reefs, add 50% nitro and da** the torpedoes*.
We have lots of tricks unavailable to fullsize including very deep keels, lead and in the very worst case, removing the highest sails.
As an aside: I do LOVE the raked masts of US (and Cannadien) vessels - they look to be creaming along even on the stand.
*And this is a forum where many people will know what a torpedo meant when that was uttered
Did you ever come across the Aeronutz when you were doing micro scale planes, MB?
Exciting times! I could never bring myself to build planes that would win or were well documented, so I had fun and maintained my personal interest level.
|Oct 13, 2009, 04:38 PM|
Just calculated the sail area for the Brig
All sails set Sail area is 33dmē or 511sqin. pretty good, i still have to get teh center of effort to start with any keel depth calculations.
|Oct 13, 2009, 05:25 PM|
Keel depth calc - Post #9 of my topsail schooner thread shows how I went about it. Aldebaran ended up with about 25cmkg of keel righting moment. Since that has worked fine for all 3 rigs tested, I bet it would work with Somers, too. You can get that with 0.5kg x 20" keel (Aldebaran), or 1kg x 10" keel, etc. All you need to know is how much spare buoyancy (available after accounting for RC gear weight, spars&sails, scale details) your ship has for ballast. Then divide that ballast into 25 to get your keel depth in cm. If you have lots of spare buoyancy, you could make a stiffer ship than mine, say 1 kg on a 20" keel (50cmkg moment) for 2x the sail carrying ability.
Knowing the CE is not necessary for keel calcs - good thing for me because I don't know how to calculate the heeling moment (= CE x sailforce, but what is the force on a set of sails and how does it change with bracing & sailing course?).
Over-canvasing is more a problem with f&a models than squareriggers. We squarerigger skippers can easily reduce canvas to match the wind conditions; striking royals and topgallants takes me no more than 2min on the water, I bet - I'd need that long to just find the reefing lacing for a f&a, let alone trying to actually do the sewing :-). By starting with the "excessive" sail area, matching the scale sail plan, we are prepared for drifter voyages, just like the real ships. And by striking sails as necessary to control excessive heel, we can pretty speedily adjust for a wide range of wind velocities.
Bottom line - the amount of ballast is set by your spare buoyancy, the minimum depth of keel is set by your desired keel righting moment.
|Oct 18, 2009, 02:11 PM|
So the whole parts of the Somers project, plans, materials, rc stuff and tools have been packed in my traveling workshop... i`m going to fly out to portugal day after tomorrow really early and there building Somers will serve as the evening entertainment programme (not much else to do on Beja airbase).
unfortunately i`ll not have internet most of the stay so there will be no progress update in the next 3 weeks unless i can find connection at some internet caffee.. which usually means slow updates especially for pics.
At least i`m hoping to get the hull shaped and preliminary finished so i can start rc installation and hopefully there will be some liquid water left when i come back to maiden the ship !
|Oct 27, 2009, 08:37 AM|
well a quick update as i was able to get some internet on the road.. i`ve so far accomplished next to nothing i built the plywood keel and now i need to start cutting the hull pieces. unfortunately my fretsaw blade broke and i found out i forgot to bring spares ... so i got myselfe a power tool jigsaw that i`ll try next.. but that will be pretty hard on the balsa i guess. We will see but i still hope to have the raw hull shaped by end of this week.
|Nov 02, 2009, 05:38 AM|
so finaly some progress to show
I finally cut all the buttock pieces (i found that after slowing the saw down a bit the cut lines where pretty decent), glued them together for raw halves, sanded the raw halves, hollowed them out (that was a huge job...) and then glued to the keel. I also attached the aluminum U-profile where the fin keel will be attached.
The Deck has been cut out (raw) and i have cut out the bullwarks but now attached yet. First i`ll install the RC, and the mast foots into the hull than the deck can be fixed mounted and the hatches cut out and then the bulwarks attached. but all in all the shape starts to come out
Please excuse the quality of the pics i only had my phone cam available as i forgot my digi cam at home
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