What's wrong with this jib?

[GordMay]

Greetings and welcome aboard the CF, Bully.

[colemj]

Originally Posted by barnakiel

In our case, the sailmaker selected wrong cloth technology for the cut.

Not the case here, as the OP stated the cloth is Dimension-Polyant Proradial, which is specifically designed for radial construction.

Mark

[duefocena]

Originally Posted by Ostinato

This may be nothing but I just had a new main and jib made with Dimension-Polyant Proradial cloth. The cloth looks good but the pictures attached show what appears to be "cupping" between the seams. There has only been light wind so we haven't been able to give them a real work out but I am concerned enough to ask if anyone has had this experience and what it might mean?

Showed your pictures to my sailmaker ( Just had new sails made for my cat, you inquired about my prior set) and his assessment was that it is the material. It may be an end roll. He said it is possible that bobbin tension was improper but either way he said the sail is defective and the maker should take it back.

[barnakiel]

You sure it is Proradial cloth?

When I blow up the image the cloth seems something else. Then again it is a small image and it may be moire or any other digital imaging artefact.

Materialien | TOMMY Sails GmbH & Co. KG

(I am not related) and there are fine images showing which DP cloth has which look, in the above.

A very poor workmanship from a sailmaker another possible culprit. But it would be a pretty odd mess up on a dacron cloth that is not at all very stretchy. Normally, you spread the sail before you sew it - the panels being held just by the stickyback. So at this stage such a problem would be immediately discovered.

Cheers,
b.

[dgz3]

I bought new sails from a well regarded local sail maker. (Mack in Stuart, Fl).
When I put them on at the dock they looked perfect.
When I set them in a 5 knot breeze they looked perfect.
When I set them in a 15 knot breeze they looked perfect.
Five years later they still look perfect.
I'd be asking for a refund. Not excuses or promises, or explanations like, "we always make them like that so that they shape up just right in a gale."
The longer they put you off, the closer to the end of your warranty you get.

[Ostinato]

Yes it is Proradial - no question about it. I finally I had a chance to sail in 20 knots + yesterday. The cupping diminished but was still present. I have written Dimension-Polyant to get their take on it. With the language barrier (Turkish) this is not going to be easy.

[Kestrahl]

It can probably be fixed by unpicking all the radial seams and if needed unsticking and flattening on the floor before re-sewing.
A Turkish sailmaker who doesn't speak English? You have to wonder how did he learn to become a sailmaker?

[Ostinato]

Speaking to anyone outside of their native tongue is always subject to more error than normal. It's when you get to the finer or more contentious points that things get interesting.


BTW Dimension-Polyant has responded that it may be a thread tension issue as several have suggested. They also think it may resolve itself as the sail is used more.

[colemj]

Originally Posted by Ostinato

BTW Dimension-Polyant has responded that it may be a thread tension issue as several have suggested. They also think it may resolve itself as the sail is used more.

But why? You paid a lot of money and do not have a suitable product. Why hope for self-resolution of a manufacturer's mistake? Take it back and demand it be fixed or your money returned. If you paid by credit card, stop/reverse the payment. At least demand partial compensation for it if you do "let it resolve itself".

Mark

[gonesail]

Originally Posted by dgz3

When I set them in a 5 knot breeze they looked perfect.
When I set them in a 15 knot breeze they looked perfect.
Five years later they still look perfect

if it doesn't look perfect now think about what that jib is going to look like in 5 or 10 years.

[impi]

Originally Posted by Ostinato

This may be nothing but I just had a new main and jib made with Dimension-Polyant Proradial cloth. The cloth looks good but the pictures attached show what appears to be "cupping" between the seams. There has only been light wind so we haven't been able to give them a real work out but I am concerned enough to ask if anyone has had this experience and what it might mean?

Shows how tired I am - here's me looking at the problems with the main sail - LOL - and then seeing the word Jib afterwards. But for now I guess I'm gonna just leave my comments here ... and see what reactions we get ... assuming you are happy with the tensioning line in the leech of the jib?

MAIN SAIL

Difficult to see exactly what is going on there but do you have a 'leach tensioning line' in the leech of the sail - if so make sure that is relaxed.

Can't see your topping lift but assuming that is relaxed ...

Boom vang is ok? Looks to me the end of the boom wants to come down some more?

Also check out the strop going around the boom. That strop should be more verticle not pulled aft and should bring the sail closer to the boom. Another line should be tensioning the foot of the sail. I know we are taking cm here but it all makes a difference

Also cannot see mast bend in this photo - excessive mast bend will also cause this effect.

[svTOTEM]

The cupping problem is clearly stitching: #1 there is too much tension. #2 radial seams should have 1 row of stiching only. Also, the smaller bumps suggest a poor job of sticking panels together. If the wrong cloth type was used (fill oriented on a radial sail) the cloth would distort badly after use in moderate/heavy wind. Hopefull this is the correct cloth, though I suspect that the sail maybe a bit stretchy anyway because the radial panels appear too wide. To few radial panels per section means greater bias loading on the diagonal side of each panel - not ideal.

[redsky49]

Originally Posted by svTOTEM

The cupping problem is clearly stitching: #1 there is too much tension. #2 radial seams should have 1 row of stiching only. Also, the smaller bumps suggest a poor job of sticking panels together. If the wrong cloth type was used (fill oriented on a radial sail) the cloth would distort badly after use in moderate/heavy wind. Hopefull this is the correct cloth, though I suspect that the sail maybe a bit stretchy anyway because the radial panels appear too wide. To few radial panels per section means greater bias loading on the diagonal side of each panel - not ideal.

"radial seams should have 1 row of stiching only."

Is this correct? My run-of-the-mill crosscut sails are all double or triple stitched. Isn't there still pressure on the sail to pull the panels apart, same as crosscut? What makes radial construction so different? Not contradicting, just curious.

[svTOTEM]

Redsky49 - yes true. Load paths in a sail run between the corners. The highest loads run from clew to head - paralleling the leech, then bending further and further into the sail.
So the idea of radial sails is that panels are oriented to align with the load paths. The long edge of the panels are parallel to load. Of course load paths are not static and change constantly, but still 1 row of stiching on the long edges is plenty strong for the relatively low loads. Horizontal seams cross the load paths so must be wide and joined with multiple rows.

Crosscut sail seams run purpendicular to an imaginary straight line between the clew/head. They cross the highest loads so require multiple rows.

The biggest sail I ever designed/built was from kevlar with a luff length of 160' and weighed 900 pounds - Radial panels were joined with 1 rows of stitching; and the horizontal seams had 9 rows.

I can think of only 1 reason to have 2 rows on the radial seams - and that is if going cheap on the construction by using very wide radial corner panels, there is a point where the seam bias loads may need a 2nd row. This creates a big problem because the panels carry to much bias load and will quickly distort.

Hope that makes sense - I'm still groggy after just finishing a boisterous 1000 mile passage to Seychelles.

[Kestrahl]

I had a look at the photo again with a associate sailmaker who used to own a big company with 12 staff. He said:
"Some fabric does that and it has nothing to do with thread tension.It just doesn't like being sewn. If it's real bad you trash it and use the fabric for tapes or patching"
And thinking back I had a couple of batches of Dimension Polyant Tanbark dacron which did it many years ago. I tried everything to get it to sew flat.

It would be a simple test of taping two off cuts together, backing the machine tension right off and sewing them to see if its machine tension or fabric.