sail plans

[bilgepump]

Could anyone offer advice on square footage for a 15'x58" double ender? I am leaning towards a cat ketch rig or a yawl rig but if anyone can offer any insite I would be most obliged....Thank you

[TeddyDiver]

Can you give any additional information about your boat? Displacement, keel, ballast, VCG, drawings, photos..

[bilgepump]

Well its still mostly in my head but the closest I could get would be the CLC Skerry if that help any?

[TeddyDiver]

http://www.clcboats.com/shop/boats/rowboats/CLC-SKERRY.html In their pages in the picture of the sail package it's marked 56sqf

[Eric Sponberg]

B-P,

How much sail area depends on what your displacement is. You consider the Sail Area-to-Displacement ratio. Sail area is in square feet, and displacement is in cubic feet, and more correctly, this is called the "volume of displacement". It is the displacement in pounds divided by 64 to convert pounds of displacement to cubic feet of seawater. But you have to raise Volume of displacement to the 2/3rds power (i.e. 0.667), which can be done on most calculators. Specifically, the ratio is:

SA/Vol^2/3

Calculate this number, and it should be more than about 17, and probably not more than about 23. This is the average range. Others may have other opinions, but that is what I typically use, and my later designs have all been over 20.

I recommend that you get a book on boat design such as the following, which explain boat design ratios like the above more clearly:

Ted Brewer Explains Sailboat Design, by Ted Brewer

The Nature of Boats, by Dave Gerr

Cruising Sailboat Kinetics, by Danny Greene

I hope that helps,

Eric

[bilgepump]

Thank you Eric and Teddy its a little confusing but I will definatly research it more. As far as the Skerry plans go I'm aware of their recomandation for 56sqf but to convert that to a yawl rig how do I figure out the size of the mizzen? Also should the main be moved forward?

[timothy22]

I highly recommend the following
http://dan.pfeiffer.net/boat/ratios.htm
more information than you thought you wanted to know, and all in one place.

[bilgepump]

Thanks dude your right I thought it would be simple but as usual I'm wrong again thank the gods for this site!!!!!!!

[alan white]

Eric is right that displacement matters. My boat is 15' x 5' 6" and her sail area is 186 sq ft, which is a bit high even for my preferences (it's how I bought her). However, I have at least 600# of lead in the keel and the sail is a gaff type.
Sail area can vary wildly if length and beam are the only variables considered. Even at the same length and beam and displacement, overhangs vary, and bottom shapes run the gamut from flare-sided to Bolgeresque square-chine and everything in between.
Then there are the intended use, locale, ease of stowing spars, rig height, and on and on.
All of those factors affect sail area. And in addition to the aforementioned, there is also ease of reefing/furling, where a boat having a more easily struck rig is likely to carry a somewhat larger sailplan.
All of these considerations take into account the ease with which a boat can achieve her best average speed without too much fuss. When the wind is light, it's nice to have a big sail, but how often is the wind light in your locale, and in which months?
I personally like my boat over-canvassed (by typical standards, she should carry about 150 sq ft). Especially in August, around here, there's not as much breeze. If it does pipe up, I can reef or douse the jib, taking me down to maybe 100 sq ft. I'll be changing my rig to a yawl pretty soon too, which will be about 170 sq ft total, but with only about 110 in the main. The advantage is, I can sail with jib and mizzen alone, at about 60 sq ft, in perfect balance.

[bilgepump]

Thank you Alan do you have any pics of your rig? Just for a referance.

[alan white]

Here's Black Rose without the jib up. As you can see, it's a large rig, and tall too, at 20 ft from foot to peak. At the time this picture was taken, I hadn't yet received my new jib. I was using a smaller jib borrowed from my other boat (prob about 22 sq ft), and that day I had it stowed.

[bilgepump]

Absolutely gorgeous Alan BRAVO! What design? You made me miss the coast of Maine like you wouldnt believe!!! Thank you for your help!

[alan white]

Thanks! The design is a one-of-a-kind I'm sure. Interestingly, the hull is glass. There the plastic ends. The spars and everything else are wood.
When I bought her, she had no sprit. The boat was a cat with 155 sq ft.
I moved the mast back 14 inches (which helped the shroud angles), and added white oak coamings and a new foredeck, tiller, sheer clamps, etc. Basically, the whole boat is new above the glass.
So I guess she's partially my design.
One thing I'd like to do down the line is to build leeboards. She's got a shoal keel that draws only 2 ft, though the keel is long. I'd like to sail closer than 55-60 degrees off the wind, and I believe the leeboards will accomplish that.
I wouldn't ever give up the open cockpit, which is what makes this boat a keeper. It's at least as comfortable as a Herreshoff 12 1/2, but with longer and wider seats, which you can sleep on.

[PAR]

No offense intended Bilgepump, but your questions are so basic in nature, that you'll need considerable education, before expecting reasonable balance from a rig/hull form combination or selection. The books mentioned by Eric are easy to read and understand without all the math and head scratching stuff of the more involved texts.

This would also apply to the rest of the design ( . . . it's still mostly in my" . . . ), which of course requires a fair understanding of the concepts, principles, dynamics and engineering associated with a vessel as complex as a 58' double ended sailing yacht.

The book store on this site has a good selection of design references, though all could be had from an on line seller or your local book store too. Build up your library and juice up your understanding of the various subjects you need a much better handle on.

[bilgepump]

No offense to you either but if you read what I had said I'm building a 15 foot(') by 58 inch ("), so pordon my lack of education in this feild. The only way to gain knowledge about anything is to ask questions and not let pride or arrogance keep your questions from being too "basic in nature" The whole reason I joined the site was to try and glean as much information and advice as I could.

[bilgepump]

Again Thank you Alan you have been very helpful.

[PAR]

My apologies Bilgepump, I read 15' x 58' instead of what you actually wrote.

Small cat ketches and yawls are reasonably plentiful. You'd be wise to look many over and study the "centers" relationships and general trends in these size and configurations. Staying close to existing designs will insure you don't make huge errors as you develop knowledge about design. Frankly, it's what all budding designers do.

The nice thing about small boats is, trim issues can usually be easily corrected on the water.

I have a number of designs of that size and several different rig configurations. If your sailing area tends to be on the light wind side, then error for a higher SA/D ratio, say 20, which I'm assuming for Akron. Also the CE/CLP lead will differ considerably depending on several factors. The hull type plays a role as does the rig type/arrangement and appendages. The last cat ketch I did was 18' and carried about an 11% lead with a small amount of balance in the rudder (10%). This was an unballasted, day boat, no cabin, just a covered foredeck. A cat ketch will be more forgiving in lead placement then a regular cat boat or sloop. A yawl is fairly forgiving, but not as much as the ketch. In short, the more sails you divide the area up into, the less the lead will move around in use, making a more forgiving design.

As far as sail area you can carry, much depends on the "power" of the hull's ability to resist being flipped onto it's side. Some shapes are easily tipped, others very stiff and difficult to roll. More information about the general shape and displacement would be helpful (as has been mentioned previously).

Again, my other half has swatted me in the back of the head for you . . .

[alan white]

You had asked about the relative size of the yawl mizzen sail. Generally, a yawl with a jib should balance the boat well if the mains'l is furled, and even if there isn't a jib, the mizzen might be a quarter the size of the main, but in any case, it is just big enough to be of value in balancing the helm by being eased or hardened up, in other words, acting a lot like the rudder of an airplane. Yawls are handy in this regard. As said, if they have jibs, they sail well with mains'l alone or with jib and mizzen with the main stowed.
I'm switching to a yawl (from the current sloop rig) for that reason and also because the yawl is very manueverable in tight spots, even able to back up, which is often an advantage when mooring or anchoring. They're also great for reefing the mains'l, holding the boat's head to the wind, or as a riding sail.
Besides, I like a lot of strings to pull and I also don't like to leave well enough alone.
When and where were you in Maine, Bilgepump?

[bilgepump]

Roughly 10 years ago I was around 18 or 19 at the time. I was on Mt. Dessert Isl. doing a roofing job and I fell in love with the entire landscape and the people. I grew up on the Raritan Bay in NJ and if I wasent swinging a hammer I was swinging a gaff on tuna and swordboats. Maine seemed like paradise to me people still live the "right way" hands on and "Downeast tough" I struck my first and unfortunately last bluefin in the gulf. But what you have said is exactly the reason behind my inquiry I want a boat that is not so geared to local winds as I plan to realy sail it from Cleveland out to Gulf of St. Lawrence. So I want to have self steering capabilities as well as light air and varying winds, and like you mentioned manuverability.

[bilgepump]

To Par: No worries but if I were to build from the skerry plans provided by CLC Boats there plans call for a 56sqf spirit or a sloop rig of 58sqf main and 18sqf jib what I'm trying to figure out is how to get the numbers on a mizzen. I'm sure its not as complicated as I think but more of a matter of reducing the mainsail area. The plans call for no ballast aside from the human type. As Alan had said it (the mizzen) should be roughly a quarter of the mains area but with all the replys talking about all these equations I'm more confused then when I started. I'm not building her to stay in Akron if you've ever been here you would understand,(LOL) but I'm trying to find the happy medium with the sails. I had planned on adding lead to the daggerboard as you mentioned in your 18 footer. In my simple way of thinking there must be an easier way to figure this all out given that I have the suggested sail ares from the plans.

[TeddyDiver]

PAR pretty much said it in the post #17.. There's no simple answer nor any right sail area.. instead there's multiple choices each having pros and cons.
BUT to give a starter you can have the CLC original mains 56sqf and ad a 18sqf mizzen and, if you like, jib same size... lot to play with :D

[bilgepump]

Thanks man that was an easy answer to follow, I suppose its going to be a matter of a little experimentation on a local lake before beating acroos Lake Erie

[alan white]

Bilgepump: You'll find that there are many boat plans showing both sloop and yawl versions. A study of those similar to your proposal would be worthwhile to examine. In looking at several of those designs, see how things are shifted around. Note how the main was cut down to compensate for the additional sail area in changing to a yawl. If you can, get a book that shows how to find the CE of any sail plan. You should see, even on simple drawings others have made of boats with both sloop and yawl versions, where the centers of each sail are, what the areas are, and what relative areas were chosen to maintain the same overall CE.
I'm 45 minutes from Mt Desert Isle. Beautiful area, though too crowded during the Summer. I love this area too, though it's no place to get rich! I have sailed the coast a lot over the years, but I have discovered that a boat on a salt water mooring doesn't work for me these days.
I have a pond across the street that's perfect for my needs----- I'm ten minutes from my front door to actual sailing even without rushing things.
I can still occaionally trailer the boat to the coast for a day's sail.
Are you planning on doing the Erie canal?

[bilgepump]

Yeah I'm going to give it a shot although I've been told its a pain in the you know what! I know exactly what you mean about the mooring my last boat was a 67 Whaler Montauk that I had moored about 200yrds (high tide) from shore and no dinghy! Needless to say I'm a hell of a swimmer!!! Yeah the island seemed like a touristy place but still the scenery is like no other on the east coast a lot like Oregon or Wash. As far as the trip goes though I have nothing else to do being that there is no work here so what the hell right!

[PAR]

A reasonable rule of thumb is to take a sloop rig, cut 10 to 15% off the length on the end of the boom and find a place to fit the mizzen. It was common practice to convert CCA style yachts to yawl rig (favorable rating under the racing rules) by this very method.

On your little boat, it might be much simpler to use scale drawings of the sail plan and see how much the CE moves as you shorten the boom. The CE can be pulled back, to balance the yacht with a mizzen. You'll find the CE isn't especially hard to figure out with some drafting tricks or you can use simple geometry.

You can also change balance a fair amount with appendage alterations. I've installed more then one skeg (or enlarged the existing one) to relieve helm pressure, rather then install a bow sprit and new headsails. I've also hacked off the end of centerboards to change balance.

Settle on a hull from. Calculate the CLP with the centerboard fully deployed and the rudder all the way down (a pin and the cardboard cut out trick works fine). If the rudder has a balanced blade then only use 50% of it's area for CLP calculations. For a Bermudian yawl rig of normal proportions 12% lead will be a good starting point.

To get you started on looking at other designs, this is one of mine.

http://www.boatdesign.net/forums/boat-design/ricellis-aluminum-gift-10388.html

It's actually a sloop, but carries a mizzen because of rapidly changing weather patterns in the area which it's sailed. On any given day you can start out in the morning with fluky 2 knot zephyrs, then build to a nice easy 8 knot mid morning, then a thunderstorm rolls through with wind strengths over 25 knots, leaving you with zephyrs to ghost back to the loading ramp. Under these conditions you'll want multiple hoist options, so in the zephyrs you'll fly jib, main, mizzen and mule. As the winds come up the mule and eventually the mizzen come down, then your first earnest reefing begins.

As far a proportions, it's a ketch, but the CE is well aft. The skeg is now an 1.5" deeper and the full length of the bottom, so the mizzen can stay up longer (weather helm). The CE is low and far enough forward, with the mizzen doused, that she can carry on as a sloop for a long time, before needing a serious reefing. This was the point, a design that could move in very light air, tolerate heavy air and have a broad range of usefulness in the "average" wind strengths they'd encounter. As a ketch, she carries about 6% lead, which is "soft" but intentional, because of wind strength. As a sloop about 14% and under jib and jigger around 17%. Notice how the lead move progressively forward as the sail plan is reduced down? This accommodates building helm pressure with increased wind strengths.

[bilgepump]

THANK YOU that is exactly what I needed to know, so a little math and I think I'll have it you guys have been more then helpful Happy New Year by the way!!! the Gift is beautiful!

[bistros]

THANK YOU that is exactly what I needed to know, so a little math and I think I'll have it you guys have been more then helpful Happy New Year by the way!!! the Gift is beautiful!

Having done the Erie Canal (in a power boat) and also out the St. Lawrence, I'd opt for the trip up the river. In the Canal you will be under power 98% of the time, and waiting 70% (for various reasons) of the time traveled. The Canal is slow, narrow, shallow in places and can be crowded. Needless to say the lower reaches of the Hudson are busy at best and dangerous at times.

Going up the St. Lawrence can be a trip back into time, and almost to another world. The Gaspe Peninsula in Quebec is spectacular, remote and beautiful. Some of the Canadian National Parks (Farillon, Fundy etc.) are places most never see in a lifetime. Plus, you can sail all the way. It's kind of cool to be in a "foriegn" land (province of Quebec) where French is spoken as a first language (although almost everyone speaks English as well).

Just my opinion.