Jami, you need to bear in mind that the lighter the cloth, the shorter the working life of the sail. You were on the right track with 190gsm Outguard - this is the right weight for your sail, if you want to do something more than short leisure sails or races.

Arne Kverneland wrote:

Jami
The sailcloth must be chosen to fit the size of the batten panels. You should rather aim for 100g/sqm (..and even 50...). Remember, each panel will only be about 2.1sqm. A 220g cloth will be reluctant to inflate in light winds.

I just spoke to Ketil Greve (Check his X-99, Marie G). His present 7-panel sail is 55sqm and he uses spinnaker-cloth, in the 100g category, ot thereabouts. That works fine.

Arne

Something like this, then?

Or rather this?

Edit: This is very interesting - hot air balloon cloth, and costs almost nothing. Too bad the weight is round 89g/m2.

Jami Jokinen wrote:

I'm going to use wide seatbelt-type webbing at the edges as suggested by Arne, which should be enough to keep flutter in control, I think.

I'm more worried about the cloth itself, being 190 g/m2 compared to e.g. 275g/m2 of Top Gun or 220g/m2 of Odyssey III and Weathermax 65.

190 gsm is absolutely fine for your size of boat. As it's 1.7m wide, and your sail is something a little under 3m wide, I would use vertical cloths, and use the excess width to form the tablings at luff and leech. Then, with the threadline parallel to the luff and leech, seatbelt webbing is entirely unnecessary. Seatbelt webbing is necessary when you make a panel out of one cloth, and the threadline is something like 10 degrees from the leech.

The breakdown of cloth that I'm referring to happens within the area up to 200 - 300 mm from the leech, and it's due more to slow speed gentle flapping when reefed. It depends on how many miles you sail, whether you'll see this effect, but it's just as well to guard against it, as you have enough width of material to do so.

Jami
The sailcloth must be chosen to fit the size of the batten panels. You should rather aim for 100g/sqm (..and even 50...). Remember, each panel will only be about 2.1sqm. A 220g cloth will be reluctant to inflate in light winds.

I just spoke to Ketil Greve (Check his X-99, Marie G). His present 7-panel sail is 55sqm and he uses spinnaker-cloth, in the 100g category, ot thereabouts. That works fine.

I know, I know, it takes a bit time for a JR first-timer to realize that the stress in a junksail's cloth is an order of magnitude lower than in a gaff- or lugsail of the same size. It took me 3-4 years before it dawned to me.

Arne

It's certainly reasonable to put doublers where they are needed - which is not necessarily the whole of the top panel. I've found it to be good value to add a wider doubler up the length of the leech, because that's where a junk sail can tend to flutter and flap and break down, and the extra stiffness and weight slows this process. 

The peak of the sail should have some extra patches, as this is where the vertical load is greatest. The throat should have some extra patches, as this is where there may be reversing loads across the bias of the cloth. It may be easier to do this by doubling the entire top panel, if you have spare cloth, but I wouldn't see it as essential.