Monday, January 7, 2008

to bring us up to speed

I bought the boat from a nice bloke in the northern territory at the beginning of 06. I'd never seen it in the flesh when i picked it up from the truck depot and was all round pretty stoked with it. The bare hull weighs about 15-18kg with fittings on. The wings are carbon (fibreglass?) sailboard masts. carbon stick, sail was almost dead. The boat is rock solid though, and as a first moth and a test platform for ideas it is very satisfactory.

Tacking out of the manly boat harbour the first time was interesting. And on my second sail i broke the wings; the middle of the aft bar and the port tip of the fore bar. I didnt realise that the aft wingtips needed to be tied together. after a pretty long swim some windsurfing dudes helped me get the boat up the rock wall of the marina. repaired:

also the t foil came off the rudder, i took the opportunity of saving myself about a kilo by doing away with the old gnarled rudder box, and re'built the rudder; the old blade as a one piece arrangement with a new T-foil made out of laminated balsa and a carbon tiller and tiller extension. this made the boat much easier to control. i also raked the rig back lots, and replaced all the ropes and most of the blocks, both changes were winners. how someone managed to get it around the course with the previous setup i dont know, but i take my hat off to them.

That all went ok for a couple of sails and I started looking into hydrofoils. Then my flash looking one piece rudder snapped while bearing away one day. another hour in the water, finally picked up a tow back to the harbour, and after that hydrofoils looked like a very good option.

My first hydrofoil mould.. was a work of art, but not so much of science or engineering. we wont go there. important lessons learned.

The second moulds used a thicker NACA 6-series strut section, rather than the NACA0012. This benefited from having a more rectangular shape, and being thicker, and hence a stiffer strut. the mould could be bolted together to form the complete foil. The lay-up took 2 days per foil - all the carbon in one hit (6x400g uni, 1x200g twill on the outside and 1x300g double bias on the inside) and peel ply. Then a 200kg/m3 foam core set with a wet Q-cells bog between the carbon bits, and the whole thing was bolted together and pre cured, before being baked at 80 degrees for 24 hours. The result was precise, with a nice finish, no bubbles, and very stiff, and tense. it resinated when you knocked it, like it should.

I made an adjustable fairing for the foil to fit into my existing centreboard case - a case within a case. all the control systems were very similar to what the prowlers were running at the time. i purposely made the foils a bit long, knowing i could move the rudder gudgeons and re-drill the centreboard to shorten it if need be. first test was in the manly boat harbour in 5-10 kts, and to my surprise all 45kg of boat and 75kg of skipper went rocketing out of the water on the first puff. i foiled around for 10 minutes and called it a day. the control systems really didnt work that well, but i really didnt care at that point. stoked.

Second time out it was a bit breezy and a bit choppy on the bay. The sideways force on the long rudder twisted the aluminium rudder gantry that was nicely built but clearly not designed for those loads. I had a scary ride into the harbour with the foils 10 degrees out of allignment.

At this point, it was about 3 days before the nationals at cootharaba and i knocked up a new gantry overnight which was crap, but lasted the nationals. just. and shortened the foils to 850mm, though didnt cut them off, as the lake was meant to be a tad shallow. and it was definitely fun foiling (some of the way at least) into the shore when everyone else was getting out in neck deep water.
the day before the regatta i went out on the lake and foiled around fine. need some practise. just before the invitation race i had a big crash and was not suprised to see the main foil in 3 bits. At the particular point when the boat is nosediving at 20 degrees doing 15kts, there is so much load on that foil from such a wrong direction that i couldn't see how all the others managed to stay together. in fact i couldn't see how mine had survived quite a few such crashes. I got to the shore with my few shredded bits of carbon hanging a bit limp off the bottom of the boat and it became apparent that all i had to do was tie the bottom plate to the top plate and strut. lots. then she'd be able to resist that negative load that i didnt really foresee. Sailed the regatta as a low-rider, (had to bite the bullet and do an overnight repair on the broken standard rudder) I found the boat to be fairly quick on the breeze but not downwind. maybe that was to do with my mast rake... or my lack of balance... did orrite in the end i was pretty happy. Brent ended up beating me, but i did finish the regatta with two DNFs.
anyway over the course of the regatta i broke:
2 sails. (one was emo's, i hope that fixed up alright)
1 hydrofoil.
1 dacron tramp. (stitching)
1 repaired t-foil rudder. (sheered off on the second last day in 25kts at the bottom gudgeon)
1 makeshift gantry. (didnt actually break, just elongated the holes where it attached to the boat)
So a year later im into it again, i have an opportunity to try some new ideas. i need a new foil, a new gantry, a new tramp, a new sail and the control system needs an overhaul. give me a month to psych myself up.

No comments: