Jim Michalak's Boat Designs

118 E Randall, Lebanon, IL 62254


A page of boat designs and essays.

(15September13) This issue will show how to rig a sharpie sprit sail. The 1 October issue will start a discussion about modifying the length of a boat.

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Left:

A Sowsear skipper's eye view of sunset on a Michigan Lake. Very nicely modified. He has uploaded a very nice video of a night on the water in this boat at http://www.youtube.com/watch?v=6Vsj402HXFU.


Contents:

 

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jim@jimsboats.com

Jim Michalak
118 E Randall,
Lebanon, IL 62254

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Rigging Sharpie Sprit Sails

BACKGROUND...

My first homebuilt boat, in 1981, was a Bolger Teal rigged with a 59 square foot sharpie sprit sail. Next boat was the Bolger Jinni with a 96 square foot main and small mizzen, both sharpie sprits. Later came Birdwatcher with a 126 square foot sharpie sprit. I've used the sharpie sprit on lots of my own designs thinking it about the best sailing cheap rig (although it has its disadvantages too). In this essay I'll pass along what I think I've learned about it.

THE BASIC ELEMENTS...

sharpie sprit sail

Figure 1 shows the basic elements of the sharpie sprit rig. We'll talk about them one by one. The basic elements are the MAST, the SAIL, the MAST/SAIL ATTACHMENTS, the SPRIT, the SPRIT ATTACHMENTS. Here we go...

THE MAST...

The sharpie sprit mast is actually one of its main disadvantages...the mast needs to be long compared to something like the mast of a balanced lug rig. For example my 12' Teal needed a 16' mast to set enough sail to be interesting, the Jinni needed a 21' mast on its 15' hull, and the Birdwatcher needed a 24' mast on its 24' hull. In general the mast needs to be longer than the boat, sometimes by a goodly amount. That causes problems in trailering and cartopping, especially with the smaller boats. It's at its worst with a small row/sail boat like Teal. If you have to row the boat after sailing, you need to leave the rig standing. Where are you going to put a 16' mast in a 12' boat? If there is any wind about, rowing the boat with the rig standing is very difficult. On Jinni I put a set of crutches fore and aft to stow the rig. The crutches were off centerline so I could launch and row the boat with the rig still stowed - very important. Never stow such a rig on centerline if you don't have to. Actually the mast length problem would be no different for any triangular sail rig.

As for mast material, low tech wood is the way to go. I've tried aluminum and other pieced together solutions and I'll report on them some issue. But the single straight stick seems to be the best. The three boats I mention all had masts with square cross sections (even though the Birdwatcher was supposed to be octagonal). The square masts are a lot easier to build than the octagonal or round masts. I suspect they work about as well. They are stiffer for the size and can easily be built hollow like a box if you want, although if you crank through the numbers you might find that a hollow mast in the size we are talking about saves very little weight. But I don't think a mast should ever be made of a single piece of wood, at least not the wood my sources carry. Always laminate from at least two layers to minimize warping.

Sharpie sprit masts are usually unstayed, that is they have no supporting guy wires. That means a heavier mast but a simple and easily assembled structure. I think a stayed mast would work as long as you were on the lookout for interference between the wires and the sprit as it projects forward.

I might add that from a practical standpoint the 24' Birdwatcher mast, which weighs perhaps 35 pounds, is about all one man can put up by himself with repeatable ease. Even then you must use care, practice and patience and be in control of the thing all the time. You must really rig the boat on shore. The small skiffs often don't have the stability needed to allow you to stand up in the boat trying to balance a 16' stick on end. In rough water it is not possible without good luck. And with the larger ones you may have the stability to try to raise the mast while afloat but any passing wave that rocks the boat as you stand a 24' mast on end will invite disaster.

THE SAIL...

Up until a month ago all the sharpie sprit sails I had made were of real Dacron sailcloth using instructions from SailRite books. As far as I'm concerned they all went quite well. The SailRite books contain all the information you need although the book I used, written 20 years ago, was a bit jumbled. But since then I think I've learned a few things needed to tweak the general instructions to sharpie spritdom.

For one thing, almost any sharpie sprit sail will benefit from having its leech (trailing edge) hollowed out. If you don't do that the leech will flutter with a loud motor boat sound in higher winds. Usually 2 or 3" on a 20' leech might be enough. I don't think there is any special number, but you do have to hollow it out.

Next, the foot of the sail should be cut more or less as if the sail had a boom which is to say with some "round". I've always use the SailRite instructions for getting the round. I've seen Phil Bolger write that the foot should be cut straight. But I can't see that if you are looking for shaping in some camber. My feeling is that the tension in the foot of these sails is so high that the foot is going to straighten out due to the load no matter how you shape it, so it ends up as if you had laced it to a straight boom.

Next, the luff of the sail needs a lot of "round" mostly to allow for the backward bend of the unstayed mast, which can be considerable. Here again SailRite gives good guidance in suggesting the mast be supported at it ends, a weight equal to half the sail area suspended in the middle, and the resulting deflection "mapped" and applied to the luff. The "round" needed to allow for sail draft shaping is added to the deflection round but it is usually a lot smaller than the deflection round. You might be surprized how much round the luff may need - a 14' luff may need 5" or 6" of round, especially if the mast is limber!

As for allowance for draft, I think a camber of 7% to 10% is fine. I recall somewhere that Marchaj, who wrote the book on scientific testing of this sort, said there is no reason to ever give a sail more than 10% camber by any testing he has seen.

Lastly, I've been experimenting with a small polytarp sharpie sprit sail recently and should have a full report with "how to" within a few months.

MAST/SAIL ATTACHMENTS...

This is where the sharpie sprit sail starts to get interesting. Because the sprit must be attached to the mast well above the foot of the sail, the sharpie sprits of old could not use a regular halyard. If they did so, the sprit attachment would interfere with the normal sail attachments of the time - hoops or lacing. As the sail is lowered with the halyard, the hoops or lacings needed to pass over the sprit attachment and there is no simple way to do that. So traditional sharpie sprits had no halyards! The sail is tied to the mast head forever. You can never raise and lower sail in the usual way.

Once you accept that you have no halyard, some economies become apparent. Not only are the halyard and block eliminated, but the mast compression that results in the downward pull of the halyard is gone (as it is in high tech rigs where the halyard is secured over a stop at the top of the mast as with a Hobie cat). And the mast can be thinner up top for that. I think the top of the Birdwatcher mast, 24' long overall, is no more than 1" square.

Not needing a halyard allows for a very simple sail/mast connection, indeed. Bolger likes best simple ties every 18" or so around the mast. If one tie fails it is of little consequence. This is what the Birdwatcher used. The sail stays tied to the mast at all times. Bolger suggested a way to furl and stow such a rig.

Here is a photo of my Birdwatcher with mast and sail furled. The sprit has been stowed, the sail rolled up like a sausage and the roll secured to the mast with a bungee. (On a small boat you can actually roll the sprit up inside the furl.) Looks great and simple doesn't it.

birdwatcher

There were two problems with this method of stowing. One is that wind can get into the roll high above the tie and unroll the sail making for uncontrolled thrashing and noise and danger. It can undo you with its violence if you try to furl the rig say at the approach of a thunderstorm which later produces very strong wings. I found a nice easy solution. I tied a light line to the masthead which led down the side of the mast to a cleat near the deck. After I had the sail rolled up I would uncleat that light line and wrap it around the sail/mast working from the deck and spiraling the line around and around. Tug hard and recleat the line and the sail was secured from tip to toe. And that is how the rig was stowed for trailering too. Never came loose.

But I never solved the second problem with this furl. A sail rolled like this will eventually take a permanent curl at its trailing edge. It can't be good for the sail shape. The only thing I could think of to solve this was to roll the sail a different way each time.

Simple lacing works well too. There are lots of lacing schemes but here are two I tried with Jinni and both worked well. Actually these lacings can work with a halyard given some tricks which we'll look into next time.

lacing

I found the masthead lacing to be a special challange. The sail needs to be pulled up at the masthead and also pulled close to the mast. With simple ties, two separate ties will do the job. But with lacing you need to try to give a special extra loop around the mast at the top grommet so that the lacing pulls both up and into the mast. Be ready to tinker.

After I had tried all of the above with Jinni I went to the method the plans called for - standard sail track. I found an oldster in selling 20' of sailtrack for $20 in Messing About In Boats classifieds and scooped it up because now the stuff costs $5 a foot if you can find it at all. It worked perfectly, better than all the lacing schemes. But if I had to pay retail for the track, I would go back to lacing. I think in many ways that the old traditional ways of rigging boats are coming back because the materials, like sailtrack and Dacron sailcloth which made the traditional ways obsolete, are now getting too expensive to consider.

As for the tack attachment, like the masthead attachment it is best done with two separate lines, one around the mast to hold the sail close to the mast, and another pulling down on the sail. The one that pulls down is best done this way: Have a line tied through the base of a cleat near the bottom of the mast. Run the line up through the tack grommet and back to the cleat where you belay it. This way you will have a two-to-one advantage here (ignoring friction) and can really crank in some luff tension if you need it. If you see the luff of your sail starting to pucker between its luff grommets in higher winds, you can remove the puckers with more tension on the tack attachment. This way is a lot easier that trying to retension any halyard, if you have a halyard. In fact it might be worth setting the tack line to a spring loaded cam cleat instead of a regular cleat to allow for instant adjustments. Like this:

THE SPRIT...

In a lot of ways the sprit makes the rig into a bow-and -arrow affair and makes the sharpie sprit a high performer. The sprit itself is in compression and can usually be fairly light. I used a 1-1/2" square sprit for Jinni's 96 square foot main and a tapered 1-1/2" x 3-1/2" sprit for Birdwatcher's 16' sprit.

The sprit itself sort of floats free with its aft end tied to the sail's clew, and usually attached to the sheet there. The fore end is attached to the mast with a tackle called a "snotter" More on that later.

But if you put tension in the snotter you put compression in the sprit which forces the clew aft. That tensions the foot and leech which in turn pulls the masthead aft. Here is what happens.:

mast bending

By varying the tension in the snotter you can preload the mast bend to what you want and that varys the draft of the sail to something you want. It's actually quite adjustable although there are limits to it all. So this very simple rig can do things for which other boats need adjustable stays, etc. I always found the thing works very well. I have a feeling that, as with most "preloaded structures", the preloaded bendy mast retains the shape that you put into it until the wind force overcomes the preload. So the sail shape will stay constant until that wind force is attained, the sail shape does not change with the wind below that threshold. So I've always felt that the rig should almost always be preloaded to some degree. I never bought into the idea that one should set the snotter tension light for light winds and high for high winds. I kept the snotter tension high all the time and hoped for a constant sail draft and shape.

One major point about the sprit geometry is how high up the mast the snotter attachment should be. The higher up you go the greater the tension in the leech and foot and the more rigid in general the arrangement. I should mention now that another advantage of the sharpie sprit is that it is "self vanging" which is to say the clew does not lift up as sheet tension varies as with a normal sail. With a regular boomed sail, the sheet pulls downward on the sail and boom to resist the upward pull of the leech. When the boom is swung forward as when running downwind, the sheet usually no longer pulls downward and the boom usually lifts up. That allows the leech to go slack, the sail looses its shape and sometimes its control. So often regular boomed sails have a vang that runs from boom downward and forward to the mast to eliminate the lifting of the boom. The sharpie sprit doesn't need a vang because the sprit is always pushing the clew down. The greater the angle between the sprit and foot, the greater the affect. So sometimes you might see the snotter tackle attached up quite high to take full advantage. I suppose the optimum would be when the sprit sort of bisects the angle formed by the leech and foot.

But it can be overdone from a practical standpoint and here is why. On both Jinni and Birdwatcher I've had the snotter attachment break or rattle loose while underway. It only happens in bad conditions, course. You need to repair it quickly because you won't have control of anything until you do. If the snotter attachment is more than chest high, you will be in danger at repairing it. Having to stand on a deck to effect the snotter attachment is a total no no as far as I'm concerned. You won't be able to do it in the bad conditions that caused the failure to start with. So that's why I place my snotter tackles somewhat lower than some other designers and builders.

SPRIT ATTACHMENTS...

One thing to keep in mind about the sprit is that it sometimes must be rigged very quickly. Another thing to keep in mind is that if it comes loose you loose everything!

Here is how I like to connect the sheet and sail to the sprit's aft end. A simple open based cleat is attached to the sprit there. The sheet has a stopper knot about two feet from its end and is led through the base of the cleat until the stopper knot bears against the cleat, then through the sail's clew grommet, and the belayed back on the cleat. Be sure there is enough rope beyond the stopper knot to do all of this quickly. Variations on this are that on smaller boats it can be nice to leave the sheet permanent to the sprit, in which case a second stopper knot can be tied in above the cleat, capturing it. Another variation is to have a snap hook tied in to the end of the sheet so that instead of having to belay the sheet after looping it through the clew, you simply snap the hook into the clew.

clew attachment

Here is how I like to connect the snotter tackle. In my opinion all snotter tackles should be at least 2:1 to allow power to easily preload the mast. So a small sail, say less that 100 square feet, should have something like in Figure A. Again an open based cleat is attached to the fore end of the sprit. A snotter line is prepared with a stopper knot and passed through the base of the cleat, around the mast and back to the cleat where it is belayed. Some sort of eyepad will be needed on the mast to keep the snotter located on the mast. For larger boats, the multi part tackle shown in Figure B is suggested. It can be put on in an instant with the snap hook. The end of the sprit is slotted to take the loop holding the block and the slot needs to be just the right width to allow a press fit of the loop rope. This is the rig I use on Birdwatcher. The snotter lead is then lead down to a belaying pin near the base of the mast.

snotter tackles

Contents


Philsboat

PHILSBOAT, SAILBOAT, 15' X 5.5', 550 POUNDS EMPTY

Philsboat is essentially an IMB with the nose extended to a pointy bow. The width and multichine configuration are the same as IMB's. The cabin is 3" deeper because Phil is at least 3" taller than most of us. In a boat with a Birdwatcher cabin like this one added depth to the cabin makes it safer in that the righting forces in a knockdown are greater. That would be true of any boat if the center of gravity did not move with the cabin roof but with the normal cruiser adding depth to the cabin also means raising the crew deck up so the folks can see over the raised cabin. And that means the CG is elevated too, and then all bets are off concerning self righting. But with a boat like Philsboat eveyone rides down low inside looking out through the windows.

Here is a photo of Bob Williams' IMB:

In addition to the pointy bow and added headroom I added what I hope is a serious motor mount. Probably 3hp will drive it as fast as it will ever go and that at part throttle. But the motor well gets to looking pretty large even for such a small motor. For one thing it must be deep to put a short shaft motor on a deep stern like this so I ran it straight down to the boat's bottom. Working on the motor down it its well will be about impossible and you might need to keep an eye on your knuckles when you pull the starting rope. And the well must be surprisingly wide to allow the motor to swivel in steering although the usual case here will be to keep the motor locked straight ahead and steer with the tiller. The wide well pushed the rudder off center and you need a crooked tiller or rudder linkage to make it all work. I opted for a simple but crooked tiller.

I also added low seats like those I saw added to the two IMB's that came to the Lake Conroe Messabout. Pretty much the same as what I have in Scram Pram where the seats do double duty as water ballast tanks. Philsboat seats could easily be converted into water ballast tanks also but the IMB capsize tests imply the ballast isn't needed.

The sail rig uses a balanced lug, 113 square feet and the same as that of a Bolger Windsprint.

Philsboat uses taped seam construction. Five sheets of 1/4" plywood, five sheets of 3/8" and three sheets of 1/2" plywood.

Actually the size and material list for Philsboat are about the same as that of Scram Pram. So which boat would be better? Take Philsboat if you are a pointy bow guy. It should be better in really rough water. On the other hand Scram is wider and roomier. It has a flat step through bow that will splash and spit in rough water but makes beaching a very nice experience.

Update, 2007. Chris Feller completed his Philsboat, probably the first prototype completed, and brought it to the 2007 Rend Lake Messabout. Very well made and to plans except he used the 91 sq ft lugsail he had on hand for his AF3, with some mast rake changes he calculated with his "sail area math". Sailed correctly rigtht off the drawing board, so to speak. We had a chance to use it for a few really nice days. In a good sailing breeze, say 10 to 15 knots with occasional whitecaps, our gps bobbed between 5.5 and 6mph for two hours of reaching as we crossed back and forth on the big lake. When I used the Philsboat I thought it was probably just as easy to enter from a beach as the blunt bowed Scram. The front deck is about 2' high so you can sit on it and swing you legs around onto the deck and then into the cabin.

Chris is a big boy but there was plenty of room inside for the two of us and more. Rumor has it that at the campsite the night before Chris slept in the Philsboat on the trailer with an airconditioner in the front hatch plugged into the campsite power. So the boat is plenty big in the way most people would use it.

The stern layout has the motor in a small well to one side and the rudder offset to the other side to give the motor room to swing. There is no linkage to the tiller, the tiller is simply "unstraight" so that is falls on centerline at the skipper's hand. Seems to work well and is quite simple. Chris uses a 2hp Honda which has a fairly large cowling for its size and must be rotated 180 degrees to grab reverse. He said the motor well size is a bit too small for that. Karl James had the same problem with his Jewelbox a long time ago and simply cut away the side of the hull in top of the motor well region - after all it is just there for looks. Chris said he tried the boat under power and found it went 6 mph max, just like under sail. No surprize to me. My Birdwatcher also maxes out at 6mph under 3hp and under 5.5 hp. This sort of hull will only go so fast. Add more power and you just dig a deeper hole and make a bigger wake - you won't go faster. But sometimes more power is nice on a windy day.

(As an update, Chris has brought his Philsboat to several more Rend Lake meets. In 2008 the meet was very windy and Philsboat got a full windows wet knockdown with Chris and Tom Hamernik on board. She self righted with no issues and they kept right on sailing, but Chris confessed he has 100 pounds of lead shot under the seats. Also he is using a 3hp vintage Johnson which he says is quieter and smoother than the Honda.)

You might recall from the Prototypes section recently that there was another Philsboat being built in California. That one last I heard was about to be launched. Has more changes from blueprint than Chris's boat but still is pretty true to form. Seems to be known as Bumble and made by Rex Meach.

And in New Zealand Rob Kellock has been sailing his with a junk rig. He has been knocked down a couple of times and self righted as planned:

Plans for Philsboat are $45.

Contents


Prototype News

Some of you may know that in addition to the one buck catalog which now contains 20 "done" boats, I offer another catalog of 20 unbuilt prototypes. The buck catalog has on its last page a list and brief description of the boats currently in the Catalog of Prototypes. That catalog also contains some articles that I wrote for Messing About In Boats and Boatbuilder magazines. The Catalog of Prototypes costs $3. The both together amount to 50 pages for $4, an offer you may have seen in Woodenboat ads. Payment must be in US funds. The banks here won't accept anything else. (I've got a little stash of foreign currency that I can admire but not spend.) I'm way too small for credit cards.

I think David Hahn's Out West Picara is the winner of the Picara race. Shown here on its first sail except there was no wind. Hopefully more later. (Not sure if a polytarp sail is suitable for a boat this heavy.

Here is a Musicbox2 out West.

This is Ted Arkey's Jukebox2 down in Sydney. Shown with the "ketchooner" rig, featuring his own polytarp sails, that is shown on the plans. Should have a sailing report soon.

And the Vole in New York is Garth Battista's of www.breakawaybooks.com, printer of my book and Max's old outboard book and many other fine sports books. Beautiful job! Garth is using a small lug rig for sail, not the sharpie sprit sail shown on the plans, so I will continue to carry the design as a prototype boat. But he has used it extensively on his Bahamas trip towed behind his Cormorant. Sort of like having a compact car towed behind an RV.

And a Deansbox seen in Texas:

Another prototype Twister is well along:

And the first D'arcy Bryn is taped and bottom painted. You can follow the builder's progress at http://moffitt1.wordpress.com/ ....

Contents


AN INDEX OF PAST ISSUES

THE WAY BACK ISSUES RETURN!

MANY THANKS TO CANADIAN READER GAETAN JETTE WHO NOT ONLY SAVED THEM FROM THE 1997 BEGINNING BUT ALSO PUT TOGETHER AN EXCELLENT INDEX PAGE TO SORT THEM OUT....

THE WAY BACK ISSUES

1oct12, Figuring Sails 1, Larsboat

15oct12, SailOK 2012, Jonsboat

1nov12, Capsize Lessons, Piccup Pram

15nov12, Figuring Sails 2, Caroline

1dec12, Figuring Sails 3, Ladybug

15dec12, Hull Shaping, Sportdory

1jan13, Bulkhead Bevels, OliveOyl

15jan13, Drawing Boats 1, HC Skiff

1feb13, Drawing Boats 2, Shanteuse

15feb13, Drawing Boats 3, IMB

1mar13, Figuring Displacement, Paddleplank

15mar13, Drawing Boats 4, Frolic2

1apr13, Drawing Boats 5, RiverRunner

15apr13, Drawing Boats 6, Picara

1may13, Two Letters About Keels, Blobster

15may13, Drawing Boats 7, Roar2

1jun13, Drawing Boats 8, Polepunt

15jun13, Rend Lake 2013, Toto

1jul13, Drawing Boats 9, AF4 Grande

15jul13, Taped Seams, Mikesboat

1aug13, Plywood Butt Joints, Paulsboat

15aug13, Sink Weights, Cormorant

1sep13, Lugsail Rigging, Hapscut

SOME LINKS

Mother of All Boat Links

Cheap Pages

Duckworks Magazine

The Boatbuilding Community

Kilburn's Power Skiff

Bruce Builds Roar

Dave Carnell

Rich builds AF2

JB Builds AF4

JB Builds Sportdory

Hullform Download

Puddle Duck Website

Brian builds Roar2

Herb builds AF3

Herb builds RB42

Barry Builds Toto



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