I have a friend with a laser cutter and 6mm 316L.
The edge quality is very good, and I can get it
buffed very nicely. I’m looking into the
electro-polishing at the moment.
No-one I’ve spoken to has any experience of it. I
assume it’s simply a question of making the
workpiece the anode - no ?
For Zygote’s new boomkin stay c/plates, we had new c/plates laser cut (including the square carriage bolt holes and the round holes for the clevis pins) from 2507 plate. We gave Roger Olson’s drawing (in *pdf) form of the c/plates to the plate supplier who did the laser cutting. Beautiful work. We then took those plates to a fabricator for the bends and mechanical polishing, bringing the exposed surfaces to mirror #8.
Electropolishing is appropriate for 316L, likely superior to mechanical polishing (e/polishing apparently avoids the possibility of damage to the surface layer from m/polishing), and less expensive to boot.
E/polishing for 316L ss involves (1) some surface prep about which I know 0; (2) an electrolyte bath, held at 75 degrees C, of a 50-50 mix of 96% sulfuric acid and 85% orthophosphoric acid. The ss plates are the anodes. The cathodes are variously described as ss or copper or lead (Step 3 is to remove any surface deposits by rinsing in nitric acid or citric acid). Electric current is determined by the area of the plates to be electropolished (15 amps for every 1 square decimeter, which is the same as 15 amps per 0.01 square meter).
E/polishing is inexpensive if done by a firm doing routine e/polishing. Setting up for e/polishing (arranging a suitable vat, the electrolyte, etc) from scratch could be time consuming.
If you send me an e-mail address by the PM facility, I can send you a PDF describing e/polishing according to ASTM B912-02 of 2008.
I haven’t got the coach bolts yet - there is a
very good supplier at the place all the big boys
get hauled out.
We had carriage bolts made in 2507 duplex ss (immune from crevice corrosion) to ASME B18.5 standard by Sandvik. We needed to specify how long the bolts should be and where the thread should start - I have now forgotten how critical those dimensions were for the bolts for the boomkin stay c/plates. We were changing all the c/plates and had recorded which bolt came from which hole (the bolts for the shroud c/plates are messy because their lengths vary depending on what furniture is inboard of them; cutting to size without removing the furniture is nigh impossible in some locations).
As my earlier posts discuss, we used Bostik’s Simson ISR 70-03 to bed the plates. I found it easier to work with than 3M 5200. But I’ll only know in 7 or so years if it performs better than 5200 (I have been rebedding the amidships cleats every 5 to 7 years with 5200 - I suspect the heating by the sun of the cleats & deck degraded the 5200, but it could just be some other age-related thing). Solar heating is not an issue with the boomkin stay c/plates of course.
The racing Dhows are very light with hardly any
depth to the keels. They use light duty trailers.
The booms are double tapered carbon fibre these
days and were selling for 19,000 US$ last time I
looked !
What to say? Money to burn. I’m sure they’re as much fun as they look. And more disposable than a BCC.
Bil
