|Aug 16, 2009, 03:02 PM|
A topsail schooner pond sailer
A pond yacht fore&main topsail schooner, based on Howard Chapelle's drawings of "Dos Amigos" in "The history of American sailing ships", 1935. The Dos Amigos was a slaver captured by the British in 1832. Her lines were taken off in Portsmouth when she was taken into British service as "Fair Rosamond". Chapelle shows the lines, a sailplan, and a couple deck drawings.
Until the advent of clippers in the 1850's, the quintessential American vessel, recognized and acknowledged the world over, was the topsail schooner. These vessels were weatherly coastal craft, due to the fore and aft sails, and yet also good for ocean passages due to the squaresails aloft. The tradewinds are mostly reaching winds for the ocean-going vessel. A schooner was always at risk for accidental gybes on a run or broad reach. A careening mainsail boom would sythe the shrouds and likely take down the mast. Squaresails are not as hazardous for these points of sailing, and were thus preferred for ocean crossings. Topsail schooners were the 18-wheelers of the era, shipping everything and traveling everywhere, including China. Some were even used as whalers.
The fore&aft fore sail was boomless due to the mainstay. At this time, the mainstay(s) (probably a pair of them) led from the main top down to the foot of the foremast. There was no way a foresail boom could swing across this stay, so the boom was omitted - for tacks, the sail was brailed up to it's standing gaff (and also along the foremast), then reset on the new tack. Since RC-ing such a brailing is beyond my modeling skill, I retain the boomless foresail, but run the mainstay to the chainplates port and starboard (not present in the photos). Marine artist Roy Cross shows topsail schooner privateer "Lynx" with foresail constrained by the mainstay - in this painting, the sail was not brailed up before tacking, but rather the leeward mainstay was slackened. This would be sufficient for a beat, where the sail is sheeted home, but would not work well for a reach, causing unacceptable distortion and wear to the sail.
The 4 channels will control: rudder, mainsail sheet, main squares, fore squares+jibs. This is similar to my running rigging tested on my barque and my bottle topsail schooner. The rudder uses the string&bungee design of DanL, thanks Dan! The squaresails use the sort-of parallogram method of the bottle schooner. It's not a pure parallelogram due to the 2:1 haul employed by the servo arms. I had to make this adjustment to give the fore gaff room to swing; with a pure parallogram, the braces would have constrained the gaff beyond my tolerance. With a 2:1 haul, I could move the braces out along the yard, giving a better set to the foresail. In the photos, you can see small bits of blue tape holding them temporarily in position.
With the RC controls tested, it's time to dismantle the whole rig for final hull painting - just black with white inner bulwarks and a light yellow (pine stained) deck. I'll sail her w/o scale deck details (including a single carronade) until I complete debugging. A ship is never done; after 3 weeks of steady work in the shipyard, I am more eager to get her sailing than make details *grin*.
My thanks to John Hartley for helping me with the hull construction; he cut the bread and butter lifts, and then used a router and a neat tool (chainsaw on a disk) to swamp out the inner wood.
|Aug 16, 2009, 11:01 PM|
Joined Sep 2006
This looks like a great project Brooks.
Perhaps a suitable project half way between fore/aft rigs and square sails, for those who have not the confidence to try a square rigged ship yet. Do you think she will be easier to sail than a square rigger?
|Aug 17, 2009, 12:29 AM|
Thanks, Tiger and Miller :-).
regarding ease of sail - based on my bottle topsail schooner, I'd say Amigos will be easy to sail under fore&aft only, but adding the foretopsails to the bottle boat did not make her harder to sail. In fact, since they help with tacking, the Amigos might even be easier to sail with the foremast's squares set. The bottle's topsails help tacks 2 ways: a) they are thrown aback once the bow passes through the eye of the wind, so the bow is driven around to the new tack even if you run out of speed and the rudder becomes useless, and b) topsails aback are easy to see when the craft is out to sea, so I don't have to depend on detecting when the small jibs are drawing on the new tack to know when the ship has passed the half-way point.
Adding the mainmast's squares to the Amigo may up the difficulty, however: it's possible to get yard-lock, if you brace the foreyards one way and the mainyards the other. The yards on this vessel are long, relative to the beam and relative to the distance between the masts. I have to watch out for yard lock on the Pamir barque, but it only occurs when the main course bentinck yard locks with the fore course's bentinck. That yard (on the bottom of the courses, only needed for simple RC ops) is longer than regular yards to keep it from entangling the backstays/shrouds of the Pamir. This schooner's yards, in contrast, are All long :-). btw, real ships have to watch out for yard lock, too.
Plus, there is the dumb thumbs effect of needing to move 3 controls when tacking - rudder, foreyards, and mainyards. I've already gotten confused just tacking on the bench, hoho. This hull, with it's fine run, and with it's plethora of canvas, should be much faster than the Pamir, so all maneuvers will happen faster, and that will take some getting used to, I am sure. If I get too frustrated by dumb thumbs, I may temporarily remove the main yards and just set a main gaff topsail, like on the bottle schooner.
I don't think that the Pamir is particularly hard to sail. There was a learning curve to surmount, certainly, but she is not a difficult boat to maneuver. So, I would not say squaresail ships are impossibly difficult :-). As I mentioned over in DanL's "design details for squareriggers" thread, the topsail schooner may be a way to break into multimast sailing because with just the fore&afts set you can always claw off a lee shore, in any conditions that would allow a sloop to do the same. A squarerigger, on the other hand, can get trapped more easily since she can't point up as high. been there, waded out to retrieve her, *grin*.
From a building perspective, this boat has been harder to construct than the Pamir. There is not enough room below decks to make squeezing in the RC gear easy. I've had to try different layouts to fit all the junk in...and there is still a question of where the RX, servo extenders, and SportBec (lipo battery transformer) will go *smiles*. This is a solid wood hull, and the space-stealing thickness of the interior wood left uncarved is a factor that would not have been present if I had the skill to make a fiberglass hull (eg Andrew's brig). This hull is 25" long, compared to 36" for the Pamir. The hull size and scale (1:40) were chosen to make it possible to transport the Amigo in my car w/o striking the topmasts. Of course, there is Never enough room below decks, in Any model, so I should quit complaining *grin*.
|Aug 17, 2009, 09:22 AM|
For those interested in a contemporary account of sailing performance and cargos of topsail schooners (perishable food, oranges, for instance), I recommend Capt. George Howland's of account of his voyages on Amistad.
This can be found a little over 1/2 way down the webpage, under the heading "What Ever Happened to the Amistad?"
|Aug 17, 2009, 06:04 PM|
The neat chainsaw blade tool John used is a "Lancelot" blade for an angle grinder:
It worked, in John's hands, like a power gouge. In 15 minutes, John gouged out more wood from the hull interior than I'd removed with chisel and hammer in 2 hours :-). And the surface needed only a light to moderate sanding to ready it for varnish.
|Aug 17, 2009, 08:59 PM|
Hi George, there are 2 known unknowns right now, that is to say, 2 problems that I have ideas for solution, but have not tested yet:
a) stability - According to my calcs for buoyancy, I will be able to use 1# of ballast on the end of my fin keel. The barque used a 12" deep keel with about 2# of leadshot. I will try a 18" keel with the 1# for the schooner, and work from there. I can go deeper with the keel, if necessary, but it's a pain wading out that deep to launch, especially in the winter :-)
b) I am going to experiment with DAP caulk, hopefully ending up with a flexible gasket under the deck (1/16" plywood in 4 sections). The deck will screw down onto the gasket.
|Aug 18, 2009, 04:15 PM|
Stability, or how much Pb does the boat need in it's keel (and how deep should the Pb be located)? I used data from 2 RC sailboats to get a feel for what keel I should be constructing for the Amigos.
Method: The sails try to heel the boat, the keel tries to right the boat. If you compare the two forces in a boat similar to your proposed new boat, you can get, hopefully, a "universal" factor that should be useful for predicting design of your new boat.
It's easy to measure the righting force, it's simply Pb weight X keel depth. The sail heeling force is much more complicated, depending on aerodynamics. Instead of that, I will use sail area as a proxy for potential heeling force...but with a twist:
...Since sails up high have more heeling effect than sails down low, it is not sufficient to just look at sail area, but rather one should use moments (= sail area X distance above datum vs Pb weight X distance below datum). A tall Marconi rig will have more heeling force than a short gaff rig, even if they both have the same sail area. Models of the J's are notoriously tender, while models of gaff-rigged work boats are, gratefully, forgiving to skippers.
For the datum, I used the base of the hull; it really does not matter, mathematically, when comparing the sail heeling moment vs the keel righting moment for heel angles near 0 deg. Since my hulls are flat through the midsection, choosing the bottom simplified measurement.
Hydrodynamically, it may matter where you measure from since the underwater body changes shape as the hull heels. For instance, a frigate laid over will float higher than when it's upright, a fact used by sailors to free their frigates from sandbars (they'd move all the weights to one side to induce a heel). However, I did not incorporate this refinement into my calculations. Mostly cause I don't know how to choose the hydrodynamically appropriate datum, but also because calculations will only get you so far...no sense being persnickity about them because there are too many conflicting factors to sort out to get the perfect answer.
When calculating righting force, it is necessary to account for the buoyancy of the keel (volume of the wood fin) and the buoyancy of the weight container (for Pb shot). For a custom cast weight, use the volume of the weight itself. For models, this buoyancy can be a significant factor. For instance, 40% of the weight of the Pb in my sandbagger's keel is used simply to sink the keel. This 40% does not contribute to righting force. If you measure in g and cm^3, you can easily figure out the buoyancy correction since 1cm^3 of water = 1 gram. Example: 1000g of Pb, hung from a keel with 400 cm^3 of wood + Pb shot container, yields a net righting weight of 600 g of Pb.
I have 2 boats that sail the way I like, namely they heel realistically in varying winds at my pond: my bottle sandbagger and my barque Pamir. I ran the numbers for both boats:
Proxy for heeling force=
Sail area x geometric center of effort, summed for the separate sails. The units will be cm^2 for area and cm for the CE, yielding cm^3 for the heeling moment.
Barque = 105,160 cm^3
This number is sort of hard for me to envision what it means, but fortunately, it gets swallowed up further down.
Direct calculation of righting force.
Net wt of Pb shot X keel depth=
Sandbagger= 6.11 cmkg
Barque = 31.7 cmkg
For the sandbagger, this means that she is can operate with 6 kg ballast with a 1 cm deep keel, 3.055 kg with a 2 cm deep keel, 0.611 kg with a 10 cm deep keel, etc. As built, she has 188g net ballast on a 33 cm fin. But I could shorten the keel if I was willing to add more lead shot. And the righting moment tells me how to adjust keel depth for different ballasts to achieve the same performance.
Note that the 3ft barque would need almost 32 kg of internal ballast to achieve the same stability as the actual fin of 33cm with 1kg of net ballast. The difficulty of using realistic internal ballast in models is highlighted....with 32kg, the barque would be a submarine (or boat anchor) :-)
Now for the universal factor = heeling force/righting force:
Sandbagger= 4930 cm^3/cmkg
Barque = 3220 cm^3/cmkg
For a given sail moment, the amount of righting force needed to match another model's performance is now known :-)
Specific to these 2 models, the above results mean that the sandbagger can support 1.5 times more sail (for a 1kg Pb keel weight) than the barque can support. I can speculate why: the sandbagger has about the lightest hull imaginable, just a PET bottle. Plus, the bottle is rectangular, forming what used to be called a "skimming hull". These hulls have a lot of initial stability; the bagger would float fine w/o any keel at all, and could probably even handle a gentle breeze w/o ballast on it's keel. So, the bagger's ballast does not have to work hard to keep the boat upright.
In contrast, the barque's hull is not stable, it won't even float upright (even without sails, masts, rc gear, etc.)w/o ballast. She started life as a "fire tramp", not as a sailing ship. The hull is built "upside down", with the weight at the top, not the bottom. That was because the original mission was to set her afire and put her out with our tugboat's fire monitors :-). The heavy wood is in the top to resist flames, while the light styrofoam is in the bottom, to provide buoyancy. Even as a dead boat, she needed a keel and ballast. The sailing barque's ballast has to work hard just to keep the hull upright, let alone resist the force of the wind on the sails. Maybe if I moved the sails to the bottom, and floated her upside down, I could reduce ballast :-).
Using the factors for the new schooner - I calculated the heeling moment of the Amigos, both with all sails set and with just the fore&aft set. Incidently, the schooner has a 20% bigger moment than the barque. Then, simply dividing the schooner moment by the factor(s) I solved for the righting moment needed if she were to perform on the water like the bagger, or like the barque.
Barque-like: All sails set 37.4 cmkg, F&A set 19 cmkg
Bagger-like: All sails 25 cmkg, F&A 12.8 cmkg.
I am limited to 0.5kg ballast due to the heavy hull (I should have made the lifts out of light white pine, instead of heavy yellow pine...live and learn, sigh). Running those numbers yields keel depths rangeing from 10" (bagger-like F&A) to 30" (barque-like all sails set). Hmmmm....well, I chose a 20" keel depth, a compromise between my aversion to wading out farther to launch and recover her, and my desire to set squares in light breezes. I am pretty sure the hull of the schooner will not capsize w/o ballast, unlike the barque, so hopefully the bagger's universal factor will be more relevent than the barque's factor.Time will tell if I made the right decision....
|Aug 22, 2009, 06:55 PM|
Looks like a nice ship Brooks! I realy like the topmasted schooners (like Lynx). what do you happen to be using for sails? It looks like paper .
|Aug 22, 2009, 10:16 PM|
Hi YB, it's Tyvek, same as I used for my barque, and for all the rest of my sailboats. I really like it, easy to work with, and seems to be sturdy - The barque is 3 summers old, and one of my freesailers is probably 10 years old. Just taping the corners with 3M clear packing tape has proved sufficient to prevent thread (which I use for outhaul, sheets, etc.) from pulling out. On the big sails, or at high stress points, I use a double layer of tape. I make the 2nd layer smaller than the first, to make a tapered tabling, just like real sails.
|Aug 23, 2009, 03:20 AM|
Joined Aug 2005
Thanks for the link to the Lancelot!!!
|Aug 24, 2009, 01:26 PM|
After a month of work, she's starting to look like a ship. Some construction photos and comments:
Once I had completed painting, I floated the hull with Pb weight equal to the RC gear and the ballast. She floated on her design waterline, a relief (and shock? heehee). The model boat floats about 1/2" lower than the scale hull would have floated. To achieve the scale waterline, I'd have had to reduce the hull (via hogging out more wood) to about 50% of its current weight. So, maybe a lighter pine, or another construction method entirely, would be advisable for anyone comtemplating making this vessel.
The rudder servo is wired to it's mount, a platform and half box of 1/8" plywood.
A nice spiderweb of lines is developing aloft :-). The blocks are 6/0 black beads. The spar jaw parrels are seed beads. Three kinds of line: 20# Berkley Fireline for standing rigging, polyester thread for running rigging (slippery), cotton-wrapped polyester thread for rigging needing knot-holding ability.
Dolphin striker silver soldered from brass rod and brass plate. Beakhead/cutwater from 1/8" plywood.
Deadeyes are Walmart buttons, dyed black with powder-version Rit dye. This was more cumbersome than I expected: the buttons precipitated the dye in the hot bath, and would glom together forming a big concretion. I'd break them up, in the interest of even dyeing, but they'd reglom as I stirred the pot. I had to spend 45min prying them apart and scraping/poking/washing off the dye granules after they cooled. No idea why they did that, I'd read that using Rit to dye buttons was perfectly feasible.
Except for the replacement of the Matthew Walker knot with a Figure 8 loop, the rigging of the deadeyes mostly authentic. Real deadeyes have only 3 holes; one of the button's holes is unused. The model's deadeyes are staggered because I did not leave enough space for mounting 3 abreast - originally I was just going to use button-bowsies, but decided to play with deadeyes after I had already made the chainplates.
Blue tape is securing the braces and other running rigging coming up thru the deck. The thru-deck tubing is Teflon tube from McMaster-Carr. I don't know if it will hold in place with the CA glue; I have used this tubing before, for pull-pull controls in an RC biplane, but I can't remember what glue I used then to keep the tubing in place.
I wanted to be able to remove the deck pieces to get at the RC gear for servicing if needed. My plan was to use a house caulk to form a releasable seal. The deck-2-hull seal for this experiment is DAP Dynaflex 230 caulking. I brushed heated and liquified palm-oil shortening (organic version of Crisco) on the bottom and edges of the deck as a mold release. Then I laid down a bead of caulk on the deck supports (beams and ledge). I screwed the deck down, and waited 30 hours for the caulk to set. The deck came up with no sticking, as it had done with test pieces earlier. The shortening washed off the varnished deck plywood with hot soapy water. I wiped the caulk, but did not use any more agressive measures to remove grease that may have stuck to the caulk (I did not find any to speak of on the tissue paper wiper). I should have laid down a bigger bead on the starboard side - I pulled the caulk gun on the port side, and laid down a nice bead. Getting worried that I was putting too much down, I pushed the gun on the starboard side. Pulling worked better. The caulk does not adhere tightly to the varnished ledge&beams. I may pull it all off and recaulk this winter (or sooner if I get a lot of water seeping past the caulk on the starboard side). This is an experiment, I won't know if it's successful until I sail, of course.
|Aug 24, 2009, 10:17 PM|
Looking good! I never would have thought to use buttons as blocks.
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