Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(15Mar09)This issue will rerun the lugsail rigging aritcle. The 1 April issue will take a look at a new design.
THE BOOK IS OUT!
BOATBUILDING FOR BEGINNERS (AND BEYOND)is out now, written by me and edited by Garth Battista of Breakaway Books. You might find it at your bookstore. If not check it out at the....
ON LINE CATALOG OF MY PLANS...
...which can now be found at Duckworks Magazine. You order with a shopping cart set up and pay with credit cards or by Paypal. Then Duckworks sends me an email about the order and then I send the plans right from me to you.
Wojtek Baginski again, shown here walking his Robote home through the streets of Warsaw after an early spring row on the Vistula.
Rigging A Lugsail
This applies to any sort of sail rig. For proper sailing the sail rig forces need to balance around the hull forces.
Look closely at Figure1 and see that the center of the sail area is placed right above the center of the leeboard's area. For boats like mine with shallow underbodies and deep narrow boards this is the way it has to be. You can't tinker very much with this if at all.
Here is what happens. In general you can think of the force of the wind as a giant finger pushing at the sail's center. Opposing that force is a giant finger pointing the other way at the center of the leeboard. The hull tends to rotate about that deep narrow board. So if those two forces are in vertical line the boat will not try to rotate and will in general maintain its heading.
If the center of sail area is moved aft of the leeboard, the boat will rotate into the wind if left on its own. To keep the boat on course the skipper needs to tug on the tiller as shown in the top of Figure 2. This is called "weather helm". Weather helm reduces the load on the leeboard and should result in a faster boat. If the skipper falls overboard the boat should rotate into the wind and stall and with luck wait for the skipper. A light weather helm is considered to be ideal.
Now take the case of the builder who modifies the rig so that the sail area centers forward of the leeboard. This might be by changing to a rig style with a jib, or perhaps by relocating the mast forward. Now the two opposing giant fingers on sail and leeboard are not in a vertical line and the boat will want to rotate around the leeboard bow going downwind. To hold the bow on course the skipper must correct by pushing the tiller as in the bottom of Figure 2. This is called "lee helm". Lee helm will increase the reaction load on the leeboard. If the skipper falls overboard the boat will turn downwind and take off without him. Lee helm is usually not considered to be good.
So the way I like to approach it is to keep the center of the sail area directly above the aft half of the leeboard. You might find lots of variations on the rules that hope to provide proper helm feel. Try them if you wish. But keep in mind that if you build the boat and it has lee helm, you need to move the sail area aft. If you have excessive weather helm, the sail area needs to be moved forward.
NOW, BACK TO THE RIGGING DETAILS.....
TYING ON THE SAIL...
I greatly prefer individual ties through the grommets although lacing looks neat. But the individual ties allow for last ditch sail shaping. If you think you needed more round in the head of the sail for example, you could make the ties in the center of the yard tighter than those on the ends. Also, a failure of a tie or two is of little consequence where a failure of a lacing line will be total.
One important note. The ties in the corners take most of the load. They should be tied as shown in the figure in two directions.
Let's look at the sail and halyard attachment in Figure 1:
As you see, the balanced lug sail pivots around the mast. I guess all sails do. But the balanced lug has the mast running through its middle somewhere, as do other Lugsails, junk sails and lateens. While the mast may interfere somewhat with the aerodynamics of the sail, great benefit is gained in proper "balance" of the sail areas that are in front of the mast. In particular if things are properly placed, the sail will twist less than similar sails that use the mast as a leading edge. As a result the lug is a low tech sail that can be more efficient to windward than you might expect.
One trick to rigging these efficiently is to get the "balance" correct. By my experience the yard should be hoisted about 40% aft on the yard. If you hoist farther forward than that you will get harmful sail twist when sailing to windward. Hoisting too far aft can make the sail uncontrollable. I have often seen in the older literature the advice to hoist at 33% aft. That will work OK but it has been my experience that all the stretches and sags in the system conspire to pull the sail aft with respect to the mast. So if you tie the halyard to the yard at 40%, in use the sail swings aft very close to that 33% value.
(You see the designer has little choice of mast placement once the sail has been chosen. The leeboard can only go at the hulls widest beam. The sail area must center right above it. The mast must cross the yard at a certain point. )
We need to rig the halyard so the sail stays near that 40% position by binding it somehow to the mast. This is especially important while reefed or while in rough water that will force the yard to pump back and forth on the mast. I know of three suggestions.
First for small simple boats that won't be reefed the best solution is to run the halyard through a simple hole in the top of the mast, tie it to the 40% position on the yard, and hoist solidly to the top of the mast. There must be a small amount of slack at the masthead of course to allow the yard to swing but that will appear automatically when you tension the sail with the tack line.
Second you can try the tightening noose system shown in Figure 3. Here the halyard runs in a loose loop around the mast before going to the masthead. It will stay loose until the yard is hauled up all the way. Then additional tension in the halyard constricts the noose (until it hits the stopper knot) and secures the yard to the mast. You will need rollers on the noose to keep the halyard from binding on the mast. I have a feeling that this is the most reliable system.
Third method works well with round and slippery masts. A loose slippery ring is simply dropped over the halyard and mast. I use this system on my Piccup Pram using a section of large PVC pipe as a ring.
THE TACK LINE....
Figure 5 shows the tack arrangement I prefer. As with the yard, the boom must be secured to the mast to prevent pumping in rough water. The actual location of the tack on the yard is not too important. In fact if it were at the very front of the boom you would have a standing lug. The standing lug is probably easier to rig and reef than the balanced lug but in my experience lacks the great manners of the balanced lug in sailing downwind.
The boom has a small cleat on it with a lanyard that wraps around the mast to locate the boom fore and aft. That loop should be fairly loose to allow easy up and down motion of the boom. This loop needs to be set up before the yard is hoisted to prevent the sail from blowing around and making a spectacular and dangerous kite during hoisting.
The actual tack line I prefer is a simple line that runs from the mast step over the boom and down to a cleat at the step. So with the boom loop attached, the yard is hoisted, then the tack line is passed over the boom, pulled very very tight, and cleated. In effect you have now a two to one tackle. All sail tensioning is done with the short and handy tack line and not with the halyard. On my Piccup I run the tack line through a cam cleat to allow for quick adjustment although I don't consider that to be as secure as the good old jamb cleat. In my opinion the tack should always secure to the hull and not to the mast. Securing the tack to the hull will secure the entire mast and rig to the hull in event of a capsize.
Here is some advice about how much to tension the tack line. It varies with wind strength. Look at the sail as you do it. See Figure 6. As you tension the sail with the force of the wind in the sail, stress folds called girts will appear in the sail. If the girt runs from throat to clew you need more tension. If the girt runs from head to tack you either have it right or can reduce the tension. A perfect setting will have no girts. Usually at the initial setup I put in a good girt from peak to tack. Then I watch it while sailing to see if that girt disappears. Then when convenient I trim as required. Remember that changing sailing conditions will change the tension requirements.
Nothing fancy needed here. Almost anything will work. Because the sail is balance already to a great degree the sheet forces are less than with other sail types. Because the tack is pulling down in the middle of the boom, the boom has less tendency to lift so downward pull of the sheet on the boom is of less importance. The location and lead directions of the sheet are of little importance also. It's another advantage of the balanced boom. By the was, if the boom is omitted to make the sail boomless, the sheet location is very critical and its needs change all the time. I think the boom is a great invention! The boom on a balanced lug can be quite light and still work.
Watch the leading edge of the sail for luffing, as with about any sail. You should be able to tack through about 100 degrees effectively, although if you are really interested in getting somewhere you might sail it more freely, say up to 120 degrees between tacks, especially if the wind is unsteady. While reaching or running a balanced lug sail, even a cheap polytarp one, will keep up with any conventional sail.
Also it should be mentioned that one of the most effective ways to trim the boat, helm-wise, is to rake the mast as required to move the sail are fore or aft. You can see that a small amount of rake will move the mast head quite a bit and the entire sail will go with the masthead. Old time boats had adjustable mast steps or partners. On my designs you can usually shim the mast partner on the bulkhead. It's one place where tinkering pays off. Making a mast a bit longer than shown on the plans is also almost always a good idea as it allows for this tinkering not to mention real life stretch of the rigging.
IMRESBOAT, DOUBLE PADDLE CANOE, 15.5' X 26", 50 POUNDS EMPTY
Imresboat is a slimmed up version of Larsboat which was designed for Lars Hasselgren to replace a Folboat that had finally met its end. Lars wanted capacity for two, plus decking, as with his old Folboat. But Imre wanted something more slender and lower in the same length. The result is 26" wide instead of 30" wide. And the result of that is that Imresboat is a single seater because the capacity has been reduced with the width. Imre wanted it even narrower but I hoped to stay within the tippyness bounds of most folks. Not sure yet how narrow something like this can get before the normal guy can't sit upright in it. I do know that you apparently can get used to about anything in that respect as experienced kayakers do.
The deck opening is smaller to sit just one man but I think it is longer than the usual kayak because us older folks have trouble fitting our legs through the hole in a performance kayak. Something like putting on a pair of pants without standing up.
(Here is a photo of Paul Moffitt's Larsboat with two aboard.)
Another change I made with Imresboat is to go to thinner plywood to save weight. In this case I suggest 1/8" ply for everything except the bottom which is still 1/4". Not sure where the 1/8" plywood comes from but it used to be what they skinned doors with. Be sure to boil a sample and hope it is waterproof. Anyway, Chuck Leinweber brought a Toto to our messabout with 1/8" ply sides and 1/4" bottom and it struck me as being fine for stiffness and strength. Like Toto and Larsboat, Imresboat is taped seam construction. I'm guessing at the 50 pound weight but for example Larsboats built of 1/4" plywood have weighed between 60 and 80 pounds depending on who built them.
Well, Chuck Leinweber also built the prototype Imresboat. He has used it for a while now and wrote this essay and sent these photos:
"I guess after three major expeditions with Imresboat, I should give you a report. The trips were: The Colorado Canyon just upstream of Big Bend National Park, a week long, 50 mile sojourn with Jim Thayer's Kokopelli group on Lake Powell, and finally an 80 mile paddle on the Rio Grande with my friend Skip Johnson - from Santa Elena Canyon on the west end of Big Bend National Park to Boquillas Canyon on the east.
The 80 mile Rio Grande trip was magnificent! Imresboat made it possible. Here the Sierra Del Carmen mountains in Old Mexico glow in the sunset. Skip Johnson's boat is in the foreground-more about that later.
I had some nice marine plywood ready to build the boat with (I still have it) but chickened out at the last minute when I found some nice Luan at Home Depot for 12 bucks a sheet. I built the boat with that and put a layer of 6 oz fiberglass cloth on the bottom and added a couple of layers of epoxy/graphite over that. I can't say enough about the graphite - I now use it on the bottoms of all my boats. It does a great job of deflecting rocks so that you mostly avoid gouges. Sharp objects like Oyster shells seem to skitter off the bottom leaving only superficial scratches. You do need to renew the stuff every so often as it is essentially sacrificial.
Sandra on our first Rio Grande trip. There were a lot of rapids on this one and she punched a hole in the starboard bilge panel and turned the boat over one time. It was a great trip!
I tend to like sailing, but Sandra really prefers paddling. That is Ok with me as I like paddling too. We have a couple of sailboats but in the past few years, we have begun to paddle local rivers here in Texas. Several years ago we built a Toto and it is a great boat but has a few shortcomings. For one thing, you have to sit about 16 inches ahead of the aft cockpit bulkhead. I assume it is back there to enable sleeping in the boat, but we never do that anyway. Also, as drawn, Toto has no deck forward which is a shortcoming if you are paddling down rivers. So I started looking at Imresboat as a substitute. What I found is that this boat, while great in other ways is a little too long for river running. But it is good for other things.
We were so unsure about the design that we took it to a local lake as soon as it would float. We were delighted to find that even with no gear at all, the boat, although initially a bit tiddley, hardened up once it leaned a bit and was not a problem to get used to. Also it proved to be very fast and easy to paddle!
Imresboat is a fast boat with a huge capacity for load carrying. On the most recent Rio Grande trip, I carried all my camping gear, as well as food and water for a week, I am not sure what it weighed but it had to be in the neighborhood of 150 pounds (the water was half of that). Add me and you are up to 300 easy and the boat handled it just fine. Well, not quite. What I found was that once the upper chine was under water, the boat tended to be hard nosed at speeds over 4 mph. What happened is that it would head off slightly to one side or the other and be very difficult to correct. At the beginning of the trip, I was loaded, but as I ate the food and drank the water, the boat floated higher and higher - and handled better and better.
Can you believe all this gear came out of that boat? Skip surveys all the camping stuff that came out of the bowels of my Imresboat so we could pull it onto the sandbar for field repairs in Mariscal Canyon.
Since it is a wood boat and since the Rio Grande was a bit low, I had to stop quite often in shallow water to avoid punching holes in the boat (I did get one leak and had to make a field repair). Then I had to paddle hard to catch up with the rest of the plastic boats which were able to bounce over the rocks with impunity. That was doubly hard as it would head off in one direction or the other once I got over a certain speed. But as I got used to the rocks, I was able to make the boat slow down enough that the bumps were not hard enough to cause damage. Thank goodness it is a wood boat as the one tiny crack I did get was easily fixed with a bit of epoxy and fiberglass right in the middle of Mariscal Canyon.
We pulled the boat up on the gravel bar we camped on that night and did a field repair. Nothing to it.
Really, though, Imresboat is not the best choice for a white water river trip - not the Rio Grande, anyway. It was perfect for Lake Powell, but for the River, a shorter version would be better - something more maneuverable. In any case, the next one we build will have a layer of Kevlar on the inside of the boat and heavier fiberglass on the outside. This was what my friend Skip Johnson did on his canoe (see photo above) and he was able to bang over the rocks just like the rotomolded boats that some of our fellow travelers paddled.
Sandra took this picture on Lake Powell. It was a calm morning of our last day on the lake. You can see that the boat is down almost to the second chine, but this only made the boat more stable and did not hurt the performance. At the start of the 80 mile Rio Grande Trip, this chine was just under water and that made all the difference.
In summation, we are delighted with Imresboat. It is an easy to build, potentially cheap, fast touring boat with room for lots of gear. I think it could be modified for a spray skirt if you wanted to get into that kind of touring. It is not unstable at all compared to other double paddle boats and the stability increases dramatically as gear is added - In my opinion, cruising is where Imresboat really shines. Our plan is to build another one of these for cruising and then build a couple of shorter boats for river trips. Thanks Jim for designing such a great boat!"
...And many thanks to Chuck for doing the prototype!
Taped seam construction from four sheets of 1/8" plywood and one sheet of 1/4" plywood.
Imresboat plans are $30.
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 I heard about through the grapevine.
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 Batista's of www.breakawaybooks.com, printer of my book and Max's book and many other fine sports books. Boat is done, shown here off Cape Cod with mothership Cormorant in background, Garth's girls are one year older. Beautiful job! I think 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.
And a new Down Under Blobster, now rightside up for final finish. Looks like another beautiful job....
A view of the Caroline prototype showing a lot of the inside, crew on fore deck. Beautiful color:
I gotta tell you that on the Caroline bilge panels I made an error in layout and they are about 1" too narrow in places on the prototype plans. I have them corrected but it always pays, even with a proven design, to cut those oversized and check for fit before final cutting.
AN INDEX OF PAST ISSUES
THE WAY BACK ISSUE ARCHIVES
1apr08, Flipper Powered Roar2, Frolic2
15apr08, Rigging Sharpie Sails, Sportdory
1may08, AF4Bottom1, Robbsboat
15may08, Rowing Gear, Roar2
1jun08, AF4 Bottom 2, Ozarkian
15jun08, Rend Messabout 2008, Vector
1jul08, Rowboat Setup, Mikesboat
15jul08, AF4 Bottom 3, Wooboto
1aug08, Sail Area Math, Polepunt
15aug08, Materials And Tools, Cormorant
1sep08, Taped Seams, Rogue
15sep08, Rainwater Damage, Mayfly14
1oct08, Bevels, Larsboat
15oct08, Transom Height, Jonsboat
1nov08, Polytarp Lugsails 1, Piccup Pram
15nov08, Polytarp Lugsails 2, Caprice
1dec08, Weight Problems, Dockbox
15dec08, Knockdown Recovery, Raider
1jan09, Knockdown Recovery 2, Caroline
15jan09, Knockdown Aspect Ratio 1, JB Jr
1feb09, Aspect Ratio 2, Mayfly16
15feb09, IMB Capsize, IMB
1mar09, Mizzens, Blobster
Mother of All Boat Links
The Boatbuilding Community
Kilburn's Power Skiff
Bruce Builds Roar
Rich builds AF2
JB Builds AF4
JB Builds Sportdory
Plyboats Demo Download
Brian builds Roar2
Herb builds AF3
Herb builds RB42
Barry Builds Toto
Table of Contents