wow, you sure that's the same sail? it looks really really good, love the inset pipe design, should work really well.

Bill

David Thatcher wrote:

The remaining battens are carbon tube, but that is a whole different story.

Alright David, I can't help but bite.

Where can I read that whole different story?

Anonymous wrote:

I believe the current battens to be  single unidirectional fibreglass. May I ask how you set up yours? Did you have the cedar in the batten pocket and the unidrectionals on the outside? If so, how were they attached/bonded to the wood?

My sail was quite large at 53 square meters and with a batten length of 6.3 meters so it was difficult to find a suitable batten material of the required length and stiffness and of sufficiently light weight. The cedar seemed like the best option because I could get clear lengths and it is a very light timber, but well down on the stiffness requirement, and that was the reason for the addition of the fiberglass unidirectionals. I used 65 mm x 38 mm cedar with one layer of 200 gram per square meter unidirectionals laminated directly onto each side of the timber using epoxy resin, but a second layer of fiberglass on the aft third of each batten. The top most sheeted batten had two layers the whole length. By laminating the unidirectional fiberglass directly to either side of the timber a type of beam is created that has much greater strength than just the unidirectionals on their own. The completed battens were entirely within batten pockets. In light winds the battens were very straight, but in stronger winds they developed a bit of curvature which seemed to add some desired camber to the sail.

Knowing what I know now I would do things differently and have done so with the battens on my current cambered panel sail. The battens are now 6.5 meters in length. The three aluminium battens are 65mm x 3mm wall thickness T5 alloy tube with cedar extensions at the forward end to make up the required length and have proven very stiff with almost no bend. The remaining battens are carbon tube, but that is a whole different story.

Anonymous wrote:

David,

Thank you! If it's ok with you, I'll pop up the measurements tonight. My only concern is whether the batten pockets are large enough to take the required diameter, or whether an alternative (glassed wooden battens on each side of sail, bolted together through eyelets) is going to be in my future.

I get the feeling this is going to be an adventure - in a good way.

On the subject of glassed wooden battens I had good success on my previous junk sail with cedar battens with fiberglass unidirectionals on either side. Although the battens were still a bit bendy they were fine for the standard flat sail. I used cedar for the light weight. I still have the battens and recently removed the unidirectional fiberglass so as to reuse the cedar for another project and I was surprised at how bendy the timber became with the fiberglass removed.

Hello Stephen,

38mm dia is about right for this sail. Either 38mm x 1.6mm 6000 series aluminium, T6 temper; or 38mm x 34mm GRP tube (which I prefer), according to which material you prefer to work with. Both will be stiff. If there isn't room in the pockets, then 32mm x 3mm 6000 series aluminium, or 30mm x 27mm GRP tube, but the former will be a bit less than ideal in strength/stiffness to weight ratios, and the latter will be just a little bit more flexible than I like (though nowhere near as bad as your jelly battens!). If the budget permits, 30mm x 27mm carbon tube would be the ultimate - light, stiff and strong with the minimum diameter.

For a single sheet span, the minimum nett length is twice the distance between the battens, but if you have room, longer is always better.