Claudio - this is excellent. Thanks!
Lester - it seems you will go down in history as the originator of “the Lester curve”.
Claudio - do not be fooled by my reference to “explicit photos”. In the English language, this term often means photos of, well, persons wearing very little clothing and engaged in adult activities. :watching_
I was having some gentle fun at your expense.
Once again, thanks so much. This has been a great thread.
Cutting the luff curve. This is certainly trickier than I had thought. Graham Bantoc makes it sound simple. He tells you that you can cut it with the panelled sail lying flat on the table. Larry Robinsn tells you to raise the clew. That is also shown on the sailmaking 101 site. That is really the only way to do it for a panelled sail.
I have found that the curve takes a slight S shape (on top of the basic smooth curve) with more cloth needed at the seams to prevent (cut down) on the sail distorting (wrinkling and becoming very flat) near the seams when the mast bends a little in the puffs. Worse at longer seams. Obviously that wrinkling is a sign that the luff curve is not correct. I hope this helps people.
The only time you see that S is when you lay the sail flat and compare the luff curve on the sail with a smooth curve. I made a template for sail size measuring purposes - with a smooth luff curve. When I laid my sail on top of it I found that the sails luff curve made the S compared with the smooth curve on the template. I think that is what I saw anyway. And it does make sense since the sails that I had made cutting the luff with the sail lying flat had the problems I mentioned.
Great fun, making sails.
You will find a s-shape luff curve also in big boat’s jibs and genoas, but I have never seen it for main sails …
Joachim,
The S curve in a jib luff is to adjust for jib stay sag I believe.
The S curve in the main that I am talking about is almost imperceptable, and it is not really an S curve. It is an S compared to the fair luff curve that you would expect to see on a main. Slight amount of added material - added to the fair luff curve - centered at the seams. And it happens naturally when you mark and cut the luff curve with the clew raised.
The address for sailmaking 101 I have posted before, but since I am posting here I will do it again.
Hi, Scot,
now I got it! It’s not a s-like curve but a wavy line, isn’t?
… no idea. Perhaps the cloth is not really fixed on the table? I found it always a little bit tricky to fix the cloth on the table without distorting it. When it moves a little bit under the template during cutting, the luff curve becomes unpredictable.
Just wanted to let everyone know that I have created a spreadsheet similar to Lester?s that takes values from AccuMeasure, and corrects them for camera angle. The main difference between my spreadsheet and Lester?s is that mine fits a forth order Bezier curve to the corrected values to find the entry and exit angles.
Being new to all this, I started a thread on another forum:
http://www.rcgroups.com/forums/showthread.php?t=481701
Would the idea be feasible?
Isn’t that the way how “they” make high performance sails in the real world?
AC comes in mind
Real World? Just because they play with bigger boats …
yeah bigger and a little bit more costy…
Ed’s links were interesting…
ok
got the sail block made.( in other words. i have the centerline marked) and I need to know how to attach the sail panels. I know we have a 90 degree cut line and we have a curved line. does the curved line come in at the top on panel 1, and a straight line at the bottom of panel 2. or a straight line at the top of panel 1 and the you match the curve line( bottom) of panel 2 to the striaght line in panel 1
cougar
:zbeer:
Okay, I’m new to this forum, so I may be repeating stuff that has been gone over multiple times.
For my first effort to make multipanel sails with built-in draft I made a full-scale “male mold” sail form from polystyrene insulation. I used nearly all of it for the Marblehead sail I had in mind when I made the form, and only the top of the form for a set of Victoria sails. It seems to me that such a form has got to be better than the usual broad-seaming block because it almost guarantees that the sail can take up the desired shape, properly adjusted. My sail form got Katrina-ed, however. The good news is that its loss led me to figure an easier way.
The only places the form is necessary are the seam locations. So I can make some airfoil-shaped polystyrene forms, probably two layers at each seam, and place them on top of a layout of the desired sail at the seam locations. I’m thinking of using double-sided package-wrapping tape to hold masking tape sticky-side up on top of the forms to hold the panels during construction.
The airfoil-shaped forms are at least as easy to make as a broad-seaming block (granted that one must make new forms for each different set of sails, though), and it seems likely to me that there’d be virtually no learning curve, which is not the case with the broad-seaming block. At least, no learning curve in figuring out what the finished sail shape would be - what you see is what you get.
What do the old hands and experts think about this approach to sail-making?
Mike Biggs
I’m not entirely sure that I’ve understood the difference between what you are proposing and using sail blocks.
I presume that your airfoil formers will still angle away either side of the seem line? Without it, you will still be making sails without a built in shape. With it - it seems to me your approach is the same as using a sail block.
I do like the idea of using a material to build the former which is easier to work with than wood or fiberglass - so long as it has sufficient rigidity and accuracy in shape.
Just my 2 cents.
The reason for the angle on the broad-seaming block is to force curvature into the sail at right angles to the curvature along the seam. If you do not force that curvature, the two panels will indeed lie flat. But a full-scale form offers the opportunity to prescribe precisely the amount of curvature perpendicular to the seams. My idea of using formers only at the seams (the panels bridging the gaps, I forgot to mention in my original post - the panels don’t lie flat on the table between the formers) just means it’s a lot easier to make the full-scale “mold” for the sails.
started to make my first set of sails today. made my patterns using sailcut 4 and got my pannels 90 degree from the luff. now some instruction say i need the pannel cut at 90 degrees from the leech. i have a set of carr sails and they are seams are cut at 90 degrees from the leech. my other set of racing racing sails are cut at 90 degrees from the luff. just wonder what you all think?
Might be worth trying to visualize an “extreme” case to check if your idea would work. Let’s imagine you’d like a spinnaker pretty much in the shape of a hemisphere. If you had a mould shaped like a hemisphere, sure, you could lay your cloth over it and seam away and you’d get something of that shape in your resulting sail. Now let’s just focus on one seam, say the one over the greatest girth of the hemisphere, and replace the mould with the equivalent former for that seam. Drape the pieces of cloth over the former, and make a broad seam. The question is, would the resulting pair of panels now have a shape approaching the shape of a hemisphere…? AFAICS, no, not until you introduced some serious bevel into your former…
90 degrees from the LEECH!
[COLOR=Black][SIZE=2]Otherwise the cloth will stretch along the leech and go out of shape.:sleep1:
(Yea, I know the cloth is proberly mylar and has no warp and weft but that is the answer to cougars question) besides it looks so much better.:magnify:
[/COLOR][/SIZE]
Like Ian said,
If you are using Mylar (Dupont?s trademark name for polyester) film, the angle does not matter.
I use 90 degrees to the luff on mains, and 90 degrees to the leach on jibs, because I like the way it looks.
ian , dan. thanks for the help. both my wife and i have been trying to get my set started. i used sailcut 4 , to make the 4 panels for the main. and it can out as 90 degrees from the luff. now i have a set of sail from pj sails. and it seem to match up. but then i looked to rod carrs sails. and they are the excact oppposite. we got the atricle from marine modeling international. then november issure. and got no where. i have never used a sail block. and would like to start making sails. so what you guys are saying . is that i should have the panels set up like rodd cars. 90 degrees from the leech. this is a great help. does anybody know where i can download a sail pattern for a IOM. then i can work off that to get my own. basicly build 2 sets. one right from the pattern. and one i design myself
thanks agian for the fast response
there are good guys here. i think i will stay here
cougar:spin:
Hi,
I think it doesn’t matter wether 90 degrees from luff or leech as long as the orientation of the cloth is correct. The warp has to be parallel to the leech. Then the stretching will be minimal.
Using the classical cross cut, the seams will be 90 deg. from the leech and the panels can be cut more or less parallel to the weft.