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Old 23-06-2015, 23:04   #31
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Re: What's wrong with this jib?

On the double thread row issue for the panels, before ordering the sails I talked to several lofts, some used two rows, others one. Is there a disadvantage to using two rows?

I have a couple of more pictures that may be better than what I originally posted.
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Old 23-06-2015, 23:18   #32
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Re: What's wrong with this jib?

On radial panel seams, 2 rows can cause tension issues (that may or may not stretch out ok) and put many more holes in the cloth (not so much an issue for Dacron as for laminates). It takes more time, adding cost without any benefit (except, as mentioned, oversizing the panel widths causing more bias loading - but this is not a good way to make radial sails).

The mainsail pic looks more like a cloth issue or cloth and thread. Really tough to tell to much without seeing in person.

s/v Totem
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Old 24-06-2015, 01:03   #33
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Re: What's wrong with this jib?

I don't think 2 rows on the radials are the cause of the problem, but they make it worse than it would have been with 1 row. If it is the fabric its still the sailmakers problem, he would have seen it on the floor after sewing one section that there was a problem and shouldn't have continued.

Triple step stitching on the headsail UV cover as shown in the photo is another no-no. More holes and makes it a lot more time consuming to replace the UV cover.

I would be asking for your money back at this point and starting again with a different sailmaker.
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Old 24-06-2015, 09:01   #34
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Re: What's wrong with this jib?

Originally Posted by svTOTEM View Post
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.
Yep. And you may chime in on the different cloth technology used for cross vs. radial sails. Even though it is technically viable to build a radial sail in 'cross-cut-technology' cloth (by cutting the longer radial panels in sections and then stitching up each radial panel prior to adding the pannels up together to make up the sail). In fact this 'primitive' radial sail technique was applied before special purpose radial cut cloth got into the picture. At times we can see such older radial sails (made out of cross-cut-technology cloth) on bigger older cruising boats with very deep sail lockers.


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