My battens are aluminium and have hinges. This gives seems to give  much more power to a flat cut sail and I would suggest that it possibly puts less strain on the battens as the lengths are less with two hinges per batten. The hinges allow for more bend on the lower battens getting progressively flatter as yo go higher.

aluminium tubing is much easier to source in Europe.

In addition to Johan's recommendation, you might also have noticed a recent post, giving the following website for Guadua bamboo. 

https://www.ukbamboo.com/product/guadua-poles-80100mm-x-5-85m/

Maybe we need a new thread, on the subject of bamboo battens.

 I wish we could get this stuff in New Zealand.

Does anyone in NZ know of a source for some equivalent, suitable for battens?

Mark , 

I had to replace a batten because I cut one too short , and got me a 4 meter long and approx 5 cm diameter Guadua pole , cost €26,70 . In comparison with aluminium it's at least €10,- cheaper (4m x 4,2 cm  cost €37,80 ) . But if you order it online you'll pay as much per batten than you pay for alluminium . 

For me is it worthwhile to drive up and down to the bamboo chandler (120 km's)

Cheers , Johan 

Hello Karl .

I recently converted my boat to a junk and I used bamboo for battens . I have a sail area of  23 m2 and I used bamboo from 3 until 5 cm diameter . Which is on the sturdy side , but they're not heavy , though , and they barely bend .

Since I'm rather new to junk sailing , time will tell how it works out for me , but I think , since you have not such big a sail 3 cm in diameter would be good . If you can lay your hands on it , try to get Guadua bamboo , it barely tapers and is unbelievable strong .

I drilled holes at the fore and aft end where I put a bolt and a piece of chain and afterwards I put on a whipping to prefend that it splits , but I guess that a hoseclamp would do the trick as well .

If you're going for bamboo , go to a bamboo chandler and handpick your battens because no bamboo pole is equal ( don't know in which part of the world you live , but in the Netherlands there is a bamboo import company , but that'my luck )

If you have still questions , feel free to ask

Good luck , Johan Uil

I've got around 10.9m² of sail area and use 25mm / 1" diameter batterns. I just used the thinnest tube I could buy - 18swg. Since mine is a split junk rig the batterns smack into the mast but have been fine - I was going to add padding but haven't so far. No visible distortion in 30 knot winds (heavily reefed - this is on a 14'/4.3m dinghy).

In the UK, aluminium tube is sold in inch units and 6m lengths. Note the diameter can vary 1mm or so depending on the wear of the die when it was made.

Also, it tends to come in 6m lengths. You may want to reduce the lengths of batterns to 3m and add wooden end plugs so you can get two out of one length. My batterns are a bit longer than 3m so I have lots of useful offcuts :-)