lateen sail, lugsail and polytarp

[peterAustralia]

Hi all,

I built a lugsail for my 18' x 4' dory on Thursday and took it for it's first sail. Now the dory is narrow and thus cannot take much sail area. My lugsail was white polytarp. My lugsail is a 42 sqr feet and cut flat. It goes upwind but I am not certain as to exactly how well. I use a 9.5ft unstayed mast. It cost about $55 Australian to make.

I am thinking of making a slightly larger rig that goes better upwind.

Option 1
55 sqr foot lugsail out of 4 Oz Dacron. It seems hard to get small amounts of 4 Oz Dacron here in Australia. I know Duckworks Magazine in the US sells it and it would cost me about $120 for enough to make my sail. So I have that option. One sailmaker I phoned here in Melbourne was not able to supply 4 Oz Dacron, I think there are 2 others to try.

To make a lugsail I would need access to a sewing machine, proper sail twine, double sided tape. I know I need to cut the panels in a certain way to give the sail a curve, and not cut flat. It is a realistic option and I know it would make a very, very fine sail.


Option 2
Polytarp lateen sail.
I can retain my 9.5ft unstayed mast (same with a better lugsail). There is a 'super heavy duty' silver ploytarp for sale at K Mart for $40. It is 20ft x 12ft, which is plenty of area. It seems a better quality than the white stuff i used before.

I was hoping that an un-boomed lateen sail could be cut flat thus making manufacture easier. To make a lateen sail, all I would need is to make one large spar, and cut the polytarp to size and reinforce with some cloth tape and add some brass eyelets, so this is a realistic and easy option too. The lateen sail seems to have a lower center of effort that most lugsails, which would suit my tender dory.

I know that a lateen sail would require me to go forward every change of tack to move the mast about. So it seems that a larger lugsail would be a better sail that a polytarp lateen sail, but is much more work to make and could cost more.



Questions are

How does 'super heavy duty, 1000 denier laminated silver polytarp' compare to white polytarp?

Will there be any creases visible in the sail?

Is super heavy duty silver polytarp good for sails?

Is an un-boomed lateen sail cut flat?

Why have I never seen a lateen sail in a boat book anywhere?
Are they too much trouble for their worth?

Would a boomed lateen sail be better than an un-boomed lateen sail?

Can an un-boomed lateen sail be reefed? or brailed up?

Lateen sails go well upwind, yes? I mean the Arabs use them

If I can find a supplier of dacron here in Melbourne I am tempted to go down the lugsail route. For sail shape I think I will copy some nice sail shapes on Paul Gartside website.

n peter evans

[norseman]

Your sail seems small for the boat. I think it's a waste of time and money to use anything other than sailcloth.
Handseaming a sail like that is pure therapy, the easiest and most enjoyable part of sailmaking IMO. I didn't use tape either and made my own thread as described by Marino.

Here is the sail copied from Riff's sailplan (sorry Paul ;-))
4 oz dacron, 150 cm width cut in half
http://farm3.static.flickr.com/2248/2079357270_63a7902a0b_m.jpg

[Todd Bradshaw]

First of all - you REALLY need a good source of information about sail shaping and construction. Step #1 is most likely to delete any files you have on polytarp sailmaking techniques as most of the stuff on the web doesn't even make a good sail from polytarp and is not suitable for Dacron. Get a copy of "The Sailmaker's Apprentice or Jim Grant's (sailrite.com) booklet on mainsail construction.

The major sailcloth manufacturers like Challenge Sailcloth and Bainbridge International have Australian distributors and websites. They will not likely sell to you directly, but they can probably give you a few names of sailmakers and dealers who will. Four-ounce cloth should not be hard to find in any country where people sail dinghies.

The only sails which are cut flat are batwings and Chinese lugs, neither of which are known for being great for sailing to windward. Lateens of any sort are not cut flat and in addition to being shaped for draft, they also usually need some extra shape added to counteract, or account for, bending of the yard and boom in use (which tends to reduce or even eliminate your planned draft).

Norseman's hand-sewn sail is very nicely done, but for the record, most people (pros included) will end up with a stronger, smoother, aerodynamically better sail in hard, slick Dacron when sewn with a machine.

The reason you haven't seen lateens in books is simply because you're not looking in the right books. Those listed above will fix that problem. If you want to see some, there are photos of several in this folder.

http://webpages.charter.net/tbradshaw/Sail%20photos/

A boomed lateen is generally easier to use on a small boat than one without a boom and yields better sailshape when sailing downwind. You do not need to go forward and change anything when you tack one. Lateens can be reefed. There is a photo of one in the folder above, though the configuration is a bit unusual as the sail has been kicked up aft to make room for a jib. You can see the line of reef points crossing the sail.

http://webpages.charter.net/tbradshaw/Sail%20photos/Michael%201.JPG

Lateens don't point as high as some other types of small boat sails with longer luffs and higher aspect ratios, but will go upwind and do it reasonably well.

Quote:
"If I can find a supplier of dacron here in Melbourne I am tempted to go down the lugsail route. For sail shape I think I will copy some nice sail shapes on Paul Gartside website."

You may be able to copy the profile, but you're not ready to copy the shape yet and to do so now without learning more about sailmaking and what is done to shape a sail properly, you would just be wasting money and materials. You can either build a sail, or a triangular tarp. At this point, your knowledge base limits you to the latter. Sailmaking isn't particularly difficult, but if you want a decent sail you're going to have to study a bit and the books will help with that. You can certainly build one that you'll be proud of, but only after a bit of homework first.

[ssor]

Todd , I used some Dacron dressmakers Taffeta for a small sail once and it appeared to work quite nicely. It was very soft but also a very tight weave so it didn't spill air through the cloth.
Do you see any reason why a stiffer cloth would be superior?

[Todd Bradshaw]

The big reason for stiffness with Dacron is that it increases stability - bias stability in particular. This helps keep the sail's shape as designed and the draft position and depth, entry angle and other aspects of the shape where they are supposed to be, rather than free to change or wander around in use. Granted, cloth manufacturers have in some cases gone a bit overboard in stabilizing some recreational fabrics and a few are backing down a bit for cruising cloth, but as long as a major aspect of sailing is being faster than the boat next to you (as it has been virtually forever) stiffness is here to stay.

Peter, I put up a couple small pdf files that show actual construction plans for a small lateen and a small lugsail. They show the profile drawing along with most of the calculated changes that need to be made to generate the actual final shape. They look more confusing and complex than they really are, but all these things need to get figured into the process at some point. You start from the beginning with a rough profile and step-by-step measure and calculate your way through the process to arrive at the final building plan. The books will take you through this entire design phase, but as you can see, trying to do it without that knowledge would be pretty difficult. After a while, you get to the point where you can do most of this in your head. These days, I make half-a dozen measurements to be sure the sail will fit the spars and then do all the shaping by eye, but I figured out the other day that I've been building sails of one form or another for 29 years now and it took most of them to get to that point. Until you do, a good book, a calculator and a tape measure are your best friends.

http://webpages.charter.net/tbradshaw/!LATEENB.PDF

http://webpages.charter.net/tbradshaw/!LUGPLAN.PDF

[ssor]

Thanks Todd.

[JimD]

I could start another thread but my question seems like it might belong here. What does everyone think of this sail, and especially how she is reefed?

http://home.triad.rr.com/lcruise/Graphics/parad4-0002r.jpg

You can see the roller furler/reefer on the boom:

http://home.triad.rr.com/lcruise/Graphics/parad6-0002r.jpg

http://www.microcruising.com/Graphics/pdx18.jpg

This is one of Matt Layden's boats, a fellow who has considerable experience and success with small craft design.

[peterAustralia]

Hi all

Thanks for the advice.

I found the link to Todd's library of sail designs, very worthwhile.
I will see what I can do about learning more about sail cut and sail shaping. I will also chase up a couple more sailmakers about 4 oz dacron.

I have an interest in proas and the proa people say a crab claw sail is cut flat (no curve built in) so I assumed that a lateen sail would be the same. I would prefer not to spend a small fortune, but may have to spend more than I would like.

Yes I am aware that to make a good lugsail I need more that 1 picture in sideview to work from, the individual panels need to be cut to a specific shape to give the sail a curve.

For some pictures of my first sail last Thursday please see here. Yes I know it is not high tech nor high performance, however it was cheap and allows me to go sailing as a change from 18 months of rowing. It also shows that my dory is tender and cannot take a huge amount of sail area.

http://www.geocities.com/peterevans_33/photos3.html

thanks
peter

[JimD]

http://www.geocities.com/peterevans_33/dory8.JPG

[Todd Bradshaw]

The test would be seeing him turn back upwind. Just about anything will drag a boat downwind, as you can see from the photos. On the other hand, if the reefed sail can't keep you from ending up on the rocks of a lee shore in relatively unfriendly weather and wind conditions (which I suspect this one won't) it's not worth much. Some sort of simple stormsail like a Swedish mainsail would probably be a much more effective choice when things get ugly out there.

[JimD]

The test would be seeing him turn back upwind. Just about anything will drag a boat downwind, as you can see from the photos. On the other hand, if the reefed sail can't keep you from ending up on the rocks of a lee shore in relatively unfriendly weather and wind conditions (which I suspect this one won't) it's not worth much. Some sort of simple stormsail like a Swedish mainsail would probably be a much more effective choice when things get ugly out there.

Todd, have you ever heard of anyone experimenting with a junk sail, Hasler style or similar with a definite triange at the top, that was basically flat cut except for the upper triangle being cut with some camber so that when you reefed down to the triangle you'd have something closer to an efficient little storm sail? Think it could work? I can't be the first guy to think of it.

[ken connors]

The last sail I made for my Vacationer was made from a used, larger sail I got from marine consignment. I got a good quality sail material in decent shape for cheap money and cut it down to the size I needed. Good luck

[Todd Bradshaw]

Jim, I haven't seen it done, though it might be possible.

[peterAustralia]

Hi

yes I was able to make some progress to windward,

It was hard to tell how much. I found I really needed tell tales to work out where the wind was coming from. I have an off center daggerboard, so no doubt that is a good thing.

Mostly I row, though I would like to sail when the wind is appropriate. Yes I know that my dory is more optimised for rowing that sailing, but is a bit hard to change now. I think I need a bit of water ballast in the bow to lower windage, that is my normal practice when rowing. You can see that I could do with a slightly larger and better shaped sail. With some more weight in it that would add lateral resistance as well and reduce hull windage, this in theory would make it sail a fraction better.

I hope you are not going to be too harsh. Is the first sail that i made, I feel at least I am having a go... By the way it is a great rowing boat when the wind is slight to moderate (rowing in strong winds is hard hard work!)

peter

[JimD]

Jim, I haven't seen it done, though it might be possible.

That give me an idear! :D

[paladin]

You might bounce some ideas off Mike Tasker at Rolly Tasker Sails in Phuket Thailand,,,he's close to you and a damn good sailmaker.......

[Todd Bradshaw]

More than anything else, I think the current lug just needs some shape and draft, especially the bottom third or so as it represents a good deal of your sail area, yet it's awfully flat and not working very hard for you.

http://www.geocities.com/peterevans_33/dory9.JPG

This would normally be added through a combination of a bit of round on the foot to add some fabric and a broadseam or two to move the belly caused by this excess fabric up away from the boom and into the proper position on the sail. On a big, solid hunk of material like the tarp, this would be done by splitting the sail into three pieces and then putting it back together with new seams with planned variance in the panel-to-panel overlaps.

The first cut is a diagonal - perpendicular to the leech edge and terminating up front at the tack corner. Once reassembled, this is called a "tack seam".

http://webpages.charter.net/tbradshaw/CUTS%20copy.jpg

The second cut is vertical, roughly 90 degrees to the first cut and about 45% of the way aft of the tack corner when measured along the foot (note that a couple inches of round has been added to the foot with it's maximum depth also about 45% of the way aft of the tack corner).

Now we tape the sail back together with simple, overlapped seams, but first, we need to determine our "standard" seam width. For a bit of extra strength, lets make it 1". We will tape cut #2 back together first, starting at the top and working down toward the foot edge. We will actually make this seam a broadseam or taper so we will start with our 1" standard overlap at the top, but slowly and smoothly increase the overlap as we head toward the bottom. The books have charts that suggest various amounts of overlap for different situations and fabric types, but I'm going to save us some time and just make a decision. Lets try to increase the panel overlap by an additional amount of about 3/8" by the time we get to the bottom - so at the foot edge, our seam overlap will now be 1&3/8". Once done, we now have a foot panel and it is no longer flat. The broadseam will give us a little bit of a cup-shaped bottom on our sail.

It's time to tape cut #1, the tack seam, back together. It will have a broadseaming increase at both ends and be our standard 1" overlap for a portion in the middle. Lets start at the leech edge and work toward the tack corner. The broadseam at the leech will be very slight. We will start at the edge with an overlap of about 1&1/8" and we want it to taper out to our 1" standard seam overlap after about 18". Leech broadseams, though slight, help keep the leech snug and prevent leech flap as the sail ages. As long as we're making a seam that strikes the leech, we might as well put one in.

After this 18" long taper is done and we are down to our normal 1" seam width, we can move forward, continuing our 1" overlap until we get to the spot (fore-and-aft) where we want the most draft - and that happens to be about 45% of the way aft of the luff - in this case, it will also be the junction with our previously installed foot broadseam. Now we start the tack broadseam. This section of this seam, from here to the tack corner, is the most powerful shaping tool on the entire sail and it will be a fairly substantial broadening by the time we get to the corner. Let's shoot for a long smooth taper that nearly doubles our seam overlap by the time we get there, say 1&3/4". Lets also do one more thing. As we near the corner, maybe the last six inches or so, lets boost the overlap increase rate even a bit more, flaring it to about 2" by the time we hit the edge. It would take a lot of space to explain well, but this flare gives us a slightly rounder entry on our airfoil than a full-length, even taper would. This in turn makes it easier to keep the sail trimmed properly and generally makes both the sail trimmer's job and the helmsman's job easier as the sail is less fussy about sailing perfect angles to the wind. You can also flare the foot broadseam on cut #2 a bit if desired, but these need to be done carefully as too much flare on the foot will tend to make the bottom edge want to curl.

Our finished seams will look something like this. And suddenly our sail has some draft down low.

http://webpages.charter.net/tbradshaw/!BROADSE%20copy.jpg

Since we did use up some fabric making the seams, it's best to rough-cut the sail's perimeter a bit oversized, then make the seams and then cut it to the final shape and size. Retro-fitting broadseams is possible, but it will slightly reduce edge lengths due to the overlaps.

The top of a lugsail will also normally get a little bit of round along the yard and even some slight broadseaming. On a polytarp sail, it's worth adding the round, but probably not worth making cuts for such small broadseams. The excess created by the round will find it's way to where it needs to be to create a little draft up top pretty well without the tapers cut in. A good sailmaking book will walk you through this type of shaping/seaming process in greater detail and the formulas needed to account for different variables will be provided.

Interesting side note: Computers reverse this process. We just made curved seams using straight panels and changing the seam overlaps to do it. That's traditional sailmaking. Modern, computer-plotters cut the panels with curved edges and keep the same seam overlap along the entire length of the seam (easier to sew in a production loft). The resulting shape of the finished sail is the same.

[peterAustralia]

Thanks once again to Todd Bradshaw,

Is 9.30 pm here (summer) and I have come back from a couple of hours on the river. i sailed about 1 hour upstream (downwind) then rowed back. Sailing upstream went well and the dory was fast. I was sailing downwind and reaching a little. all the time learning a bit here, a bit there.

Before doing that 2 of us tried sailing, tacking back and forth trying to make progress to windward. We did made a little but not much. Later I realized that one of the lacings at the front of the bottom spar was loose, thus the luff was loose as was the foot, no wonder we had problems!

This resulted in bad sail shape. I also realise that with a large boat and a small sail I am never going to make fantastic progress upwind. Nevertheless the sail has it's use.

I can take the motor as a reserve (use if for ballast) and go rowing and sailing on the bay. When wind direction is good I can reach and go downwind. For short periods I can row (I have been rowing for 18 months and am starting to get quite OK at it). If I am tired at the end of the day I can motor home, thus the sail has some uses. the mast comes down and fits inside the boat for rowing.

Yes it will function better if I lace the sail properly.

I will have a go at making these broadseams as suggested and try and give my sail more camber.

Chances are this small lugsail will mostly be used on my friends 9ft x 4ft pram, where it ought to do better due to smaller windage of that small boat. My dory will be converted to a mulithull and use a much larger rig.

Everything is a learning experience, yes performance to date as been average but am learning things and performance will improve. I feel I have enough information now to make some good improvements and make the best of a pretty average situation.

peter evans

[norseman]

Todd, you're an artist. Most excellent drawings and advise.
I also realize that I made a mistake or two since my sail has a straight luff, 1" round and no broadseams in the head curve. However I think I broadseamed the Gaff sail there ;).
Anyhow, I recommend Todd's excellent book and Marino's Sailmakers Apprentice.
My point regarding tarp sails is that drawing, lofting and laying out the sail (at least twice) is so much work that it seems pointless to use inferior materials. I ordered from Kayospruce UK, they also have hard-to-find spur grommets, handseaming needles etc.

[Boatmik]

Howdy

Todd gives great information above, but I was interested in just how far it was possible to simplify and get a sail that works.

I would accept Todd's criticism immediately that the sail is too flat and the draft is too far forward - but the boats still sail well - as they have other things going for them too - like good foils and a mast that matches the luff round for good gust response.

While a mix of broadseaming and edge round gives you the best possible shape .. it is possible to compromise strongly on the side of simplicity and just use edge round. For a first time amateur sail Broadseams (shaped panels) can be eliminated - Just use edge round. You can cheat and just do a simple hem around 40mm wide - worked fine. Todd suggests less ... which we might use next time round - we were guessing a bit.

The sails look quite acceptable. I come from a competitive racing background so was very doubtful about how far we could go in simplification - we made them as best as we could and ... wow ... they worked fine.

http://farm1.static.flickr.com/204/459817053_f153402877.jpg

These are an approximate 3oz (maybe more - my memory is not clear - certainly no more than 5oz) equivalent polytarp. It is an off white/grey colour and is available from Duck Flat in Adelaide
http://www.duckflatwoodenboats.com . They even get it sewn to the full width so you don't need to join it up - just cut it out. Cost for the boats shown is around $30

Corner patching is important - would suggest three patches per corner each larger than the last. Hold together with double sided tape and sew on a conventional sewing machine with standard sized polyester thread (black deals best with UV). Patching for eyelets up the luff is two layers - little triangles - one bigger than the other.

Put all the patching on BEFORE you do the "hems".

We found with the lighter 1.5oz polytarp (blue sails below) lasted quite OK, but didn't set as smooth because of distortion and stretching.

http://farm1.static.flickr.com/34/121228903_e3b9eea21e.jpg

BUT it lasted very well. The blue sails were used for a year. In the first month and a bit the boats were being sailed almost every day by different people - so they had around 30 outings in that time and another 15 after that. Also they were rigged on the grass by the water for the same number of days for the whole day - so at least 30 days of sun exposure.

This probably represents two or more years of sailing for most people.

So the cheap and nasty blue polytarp was OK in terms of longevity - the off-white one is much, much better - it feels the right weight and sets much more nicely with much less distortion. I would expect it to last double the time at least judging by what has happened with this set over the last year.

Total cost $50 (double sided tape and an eyelet kit - make sure they are brass and not plated steel) and about 2 hours to cut and another hour to sew.

The one on the yellow boat ... it was pretty breezy that day. Goolwa wooden boat show and most were not game to go out on the river. Gusting 25kn. Boat, mast (hollow box section) all doing well.

Best wishes
Michael Storer

[Boatmik]

Actually on sleeping on it ... I can't now recall what weight the off white polytarp was - I am thinking it might have been a bit heavier than 3oz - maybe closer to 5oz. You don't want it too heavy or the sail will be very dull and lifeless .... and heavy!

MIK