already said in my tool presentation see Point 1 page 6 wismerhell post and observe the drawings
Claudio
Claudio - I am not a bit confused.
In the very top photo of the “GOOD” position of the sail material - is the edge on the top of the adhesive supposed to follow the curvature of the metal plate and adhesive tape or not?
It “looks” like the sail panel is stuck to the metal bar/adhesive and is straight without any bend (the ends hang over the metal bar) - isn’t the entire leading edge of that panel supposed to take on the curve of the bar?
Look closely at the panel overhang directly next to either the left or right wedges. Please clarify for me. Thanks
I made a jig to reproduce Claudio’s 100mm strip experiment.I did a 200 mm strip(see picture) Mine is horizontal to simulate wind pressure(gravity) and I held the ends flat to simulate a tight outhaul. I took four pictures for Accumeasure.
- no seams
- one seam in the middle
- one more seam at the top
- three seams evenly placed top to botton.
The seams were all made the same using a .66mm wedge on a 200mm wide seam which should produce a 10% draft.
With test 1. I had top 2.7%, mid 3.1%, bottom 2%(flat sheet gravity only)All camber corrected with Lester’s speadsheet.
Test 2. top 4.9%, mid 7%, bot 4.4%
Test 3. top 8.1%, mid 8.2%, bot 5%
Test 4. top 7.3%, mid 9.2%, bot 7.2%
As you can see the camber is almost 10% in the last test. I think this confirms Claudio’s graph as long as you keep in mind that it is for completed sails. Add a little outhaul(and I don’t think I’ve ever run with none) and you would easily have 10% on most of the sail. Now comes the but. If you made a sail like Test 4 but wanted the top to have 10% camber(outhaul effect doesn’t reach that high) you would have to increase the wedge thickness on the top seam some percentage over what the graph suggests. Unfortunately that increase would probably have to be determined by trail and error. Comments please. I would also like to know if anyone other than myself, Mario and Claudio are getting anything out of this thread? Nobody is making any comments.
Don
Dick
The bend is introduced into the sailcloth when you pull the wedges. Then you tape the next panel on. When you peel both layers off you end up with TA-DA! Camber. It works quite well. Does that explain it? I’m not very good at this word stuff.
Don
Hi Don
Well, I’m cheering from the sidelines… (smile)
Hi Don
Terrific! Given that gravity introduces between 2% and 3% draft (call it an average 2.5%), and given that each seam when sewn-in registers between 7% and 8% (call it 7.5%), it seems that the “pure” sewn-in value is 7.5% - 2.5% = 5%. If you put a seam width of 200 mm (block chord and girth = 200) and a block height of 0.66 into my spreadsheet for sail blocks (remember bevel angle = 30 to take account of the fact you’re not using blocks), you get a prediction of sewn-in draft of 4.98% – call it 5%. Absolutely terrific!
The other thing we can now estimate is the effect of a near-by seam: A top seam added around 1% to the middle, a bottom seam added another 1%, and the middle seam added around 1% to top and bottom. How far away were top and bottom from the middle, please? And what weight of cloth were you using?
Lester
The seams are 200mm apart. Four equal sized panels 200x200mm. The material is drafting velum(not mylar) .002" thick. I just used what I had since it was just a trial. Glad to hear you might get something out of this.
Don
Dick,
the photo is by purpose exsagerated for imaging reason in order to obtain at the release a large and visible warp effect (photo 2). It is normal anyhow that when you fix a strait cut panel on a already bent bar , the extremes ends will overpass the bar.
In the photo the wedges used where of 3 mm that will never occurs under practical applications .
Under realistic conditions for a 300mm wide panel and required i.e. draft of 12 %, the wedge thickness will be : 300/100 x 0.38 = 1.14 mm which is 3 time less that the ones used for photographic purpose. Under these circumstancies the panel extremes will overpass the bar by about 1 mm and not 3mm as in the photo. If really one would search for Hi-precision, than the panel could be previously trimmed .
Claudio
I’m a bit dense here on this one.
Even though exagerated, there is a tiny bit of material hanging “over” the bent bar at each end. Where does this “extra” go, or is it trimmed off before pulling panel from the tape and bent bar, or is it loose when the other panel is taped in place? I can understand the “Ta-Da Camber” [grin] just not the little bit of extra material that is visibly overhanging the bent bar right next to the wedge in the photo.
Don,
one of my sails (type A) is composed at the top with wedges aiming at 12% draft , 8% draft at midle eight and 0% draft at the bottom.
The sail shape is chosen as fonction of many parameters that each one need to establish (wind force , boat dispacement, manouvrability, etc).
You are not obliged to have the same draft adjustment for all the panels.
What you have done is correct , actually you need to make a sail for trial.
My table is dictated by my personal statistical work and one should use it as a sort of “reasonable” guideline. +/- 5% tollerance could be considered because of the variables : tool precision, manipulations, tissu characteristic, number of panels and whatever.
Claudio
Dick:
Don’t mind the “extra” material, as it will be afixed to the other panel with the second layer of DS tape… Like Claudio said, nothing beats making a trial sail just to see how well it works…
PS this thread is so good from top to bottom that someody should make a digest out of it!!!
It’s left on. It will only be a fraction of a millimeter. It hardly even shows.
Don
OK - thanks. If I may put into “my” words …
The first sail panel is attached to the “bent” bar so the middle (and most) of the sail panel edge doesn’t extend over the bar.
The next sail panel is doubleside taped to the first sail panel with the overlap being only the width of the second piece of tape.
Finally both sail panels are released from the “bent” bar and Don’s “Taa-Daa” happens ! :icon_smil
This is repeated for all sail panels until the full height of the sail is reached. Then the leech and luff can be hot-knife cut, luff tape added, corner patches and grommets added, etc.
do I have that right?
hmmmm - for one of my big uni-rig multihull sails, that’s a lot of possible “Taa-Daa’s” 
Almost.
You stick the first panel to the bent bar.
Then you release the bar,clamp it straight and it puts a pucker in the first panel.
Then you stick on the second panel.
Then you release them both.
If you taped them together on the bent bar you would just have a curved tape joint on a flat panel.
Don
HI…
I have been watching this great thread for a few days and think I can make my own sails with the tool listed but I do have one question, "what is the distant of the of the % makes on the tool.
Thanks in advance
Stuart
Ballarat Australia
Stuart
You are going to have to re-phrase that, I don’t know what you are asking.
Don
Hi every body
English is not my mother laguage and I’m sorry if I don’t give brief and clear explanations or answers . There are also expressions that I do not knows ; for instance one of the last : Ta- Da or Taa-Daa what that’s mean ? Thanks
claudio
Try to imagine a trumpet playing a victure note…
I was labeled once as “eager than mustard”… that kept me worried for days…
it all depends on the mustard
Il n’y a que Maille qui m’aille
Claudio - the attached WAV file will better explain it. It is in zipped format and is virus safe. :nuts: