Stavanger, Friday

Gary P, have you treated or coated your battens with something?

I remember when I tried bamboo battens on a JR once and the mildew spread on them just in a few weeks. The wrapped sail bundle can be very moist in my area. Lately I have done a test with varnishing a bamboo stick with two-pot polyurethane varnish and this has held fine for about 3 years. The test I did before that was with one-pot varnish, and it only lasted for one summer. The bamboo stick I am talking about is the one sticking out of the end of Johanna’s yard, carrying little burgee/telltale/ribbon or whatever it is called, so it sits exposed to the elements 24-7. Btw, it is grown in our garden on 59deg North. Stavanger Bamboo, think of that!

Arne

David

It sounds like a nightmare.....  I hope that they work in the long term.... or least long enough for you consider plan B.

I must confess that my experience of building similar spars was in comparison painless, but time consuming and messy.

But I agree with you..... unless you have access to some prepreg and can make an oven, then use another material if at all possible.   On that note some of the prepreg manufacters sell off their out of date prepeg at a considerable discount.  An engineer at one of these companies told me that it was perfectly safe and reliable to use, but they were no longer able to use it in their products for ISO and insurance reasons. 

At least you can go for a sail now :-)

Peter

Peter Scandling wrote:

David

How did the carbon braid workout?  Easy to use?

Peter,

It's an uphill battle. It's easy to make a tube, much harder to make a long, straight, stiff, strong, light tube - or any acceptable combination thereof. I have made everything, and have sanded, coated and sanded again so that the spars are functional. If all's well, or at least, acceptable, I can fill, fair and paint later. I very soon reached the point where I wished I'd never started, and then reached the point where I was just hoping that it would all turn out OK in the end, and finally reached the point where I was happy to have made battens that look as though they may be OK (-ish). 

At first, I was convinced that it would be impossible to draw a batten off a 7m hard mandrel, so I was laying up on a mandrel consisting of a 28mm alloy tube, covered with pipe insulation with a diameter of 54mm. It was difficult to get a good, fair layup, and the newly made batten was hard to handle, being very flexible. It is essential to hang the batten vertical for the first stage of the cure. The first four battens I made this way are too big for my batten pockets, but luckily, we made Footprints' batten pockets bigger, so she now has replacements for her too-flexible wood battens.

Then I risked making a mandrel from pieces of 2" tube from my old battens. I found that if it was sprayed with silicon spray, covered with thin plastic sheeting, and sprayed again, withdrawing it was nothing that a big 4WD and a very large post in the ground couldn't handle. An irresistible force overcame an immovable object fairly easily.

The next problem is that epoxy takes a week at 20C to reach a full cure. With night temperatures dropping much lower, you can say two weeks. Until that time is up, the batten is at risk of sagging if laid horizontal to work on it, and so I have some interesting bends that have become permanent. Oh, well. Also, it is impossible to tell if the batten will be stiff enough until that time has elapsed. I had to make the early battens in stages, until I settled on a layup of 3 full-length braids, and one half-length braid at the after end, to ensure that the sail will be flat here.

For the yard and boom, I made mandrels of 80mm and 65mm plastic rainwater down-pipe, respectively. These proved to be too weak to pull out, so the yard and boom are heavier than they need to be, with the unproductive weight of the mandrel inside them. An alloy tube would have been a better way to go.

I could go on. If anyone asks me whether they should consider making CFRP battens they will get a one word answer:

don't

I'm back aboard, now, waiting for David Thatcher to bring down the sail bundle in the morning. I'm very grateful to him and his family for affording me living space and working space, and for the forbearance they showed whilst I struggled with this project for over four weeks.