It’s about 15 years since I learned to use a lathe at school. Now we got a vintage 1949 Schaublin lathe to the workshop, so I will have to re-learn the art of making all things round again. The lathe will be handy to have around for many projects, both work and play.
Veikko Rihu from Provoke has produced these two 1:17-scale radio controlled yachts modeled after Volvo Open 70 boats.
The boats are moulded in carbon and feature a 45-degree canting ballast. Length is 1339mm and beam 350mm. The displacement is 6.3kg with about 4.7kg in the keel, fin, and canting-electronics.
10 boats, including two guest sailors from Russia with Naviga one-metres, completed 12 races in varying no1 rig conditions.
The pictures show some cnc-milled aluminium fittings by Jari Immanen, and Oleg Konka’s RUS-32, a Naviga one-metre built by Janus Walicki. Note the rudder. The forward section has an airfoil shape while the aft half of the rudder is a very thin and flexible carbon sheet.
Started out this evening with a 1 mm sagitta on the 240 mm mirror.
Started with no60 carborundum and ca. 20 + 30 min of grinding, which got us down to a 1.9-2.0 mm sagitta. The picture shows a 2.0mm drill bit under a steel ruler used for measuring the sagitta. The surface of the mirror is quite rough and appears white when dry.
Switched to no80 carborundum. Grinding is now much smoother with the mirror gliding easily across the tool with less sticking events. After about 30+30 min of grinding we are down to a 2.3 mm sagitta. A quick-and-dirty test shows around a 3 m radius of curvature. Surface now smoother to the touch, still white when dry.
Next stop: build a Focault-test/Ronchi-test jig to properly measure the focal length and the shape of the mirror (see for example plans here). Think about moving down to no150 carborundum.
Update: Thanks to everyone who replied! It’s a Grey Heron, Ardea cinerea.
Ilkka (who runs kiteile.com) decided to make a kite-board by infusion moulding. He made 3-4 trials first, and this is the first full-size real kite-board. It’s now cured and out of the bag and it looks like everything worked fine.
En motorbåt körde på Skåldö färjans vajer ca 19:30 tiden. Alla ombord verkade ha klarat sig utan större skador och fördes bort med ambulans. Motorbåten satt fast i vajern och brandkår + färj-kapten försökte först få loss båten, men det slutade med att färjan togs loss från vajern och båt+vajer sjönk till bottnen! Färj trafiken löpte normalt igen ca 20:45.
Här en animation där man ser båten sjunka: farjan_animation2 (5 Mb AVI-fil)
As I’m very much an amateur programmer with not too much time to learn new stuff I’ve decided my CAM-algorithms are going to be written in Python (don’t hold your breath, they’ll be online when they’ll be online…). The benefits of rapid development will more than outweigh the performance issues of Python at this stage.
But then I found Mark Dufour’s project shedskin (see also blog here and Mark’s MSc thesis here), a Python to C++ compiler! Can you have the best of both worlds? Develop and debug your code interactively with Python and then, when you’re happy with it, translate it automagically over to C++ and have it run as fast as native code?
Well, shedskin doesn’t support any and all python constructs (yet?), and only a limited number of modules from the standard library are supported. But still I think it’s a pretty cool tool. For someone who doesn’t look forward to learning C++ from the ground up typing ‘shedskin -e myprog.py‘ followed by ‘make‘ is just a very simple way to create fast python extensions! As a test, I ran shedskin on the pystone benchmark and called both the python and c++ version from my multiprocessing test-code:
Python version
Processes Pystones Wall time pystones/s Speedup 1 50000 0.7 76171 1.0X 2 100000 0.7 143808 1.9X 3 150000 0.7 208695 2.7X 4 200000 0.8 264410 3.5X 5 250000 1.0 244635 3.2X 6 300000 1.2 259643 3.4X
’shedskinned’ C++ version
Processes Pystones Wall time pystones/s Speedup 1 5000000 2.9 1696625 1.0X 2 10000000 3.1 3234625 1.9X 3 15000000 3.1 4901829 2.9X 4 20000000 3.4 5968676 3.5X 5 25000000 4.4 5714151 3.4X 6 30000000 5.1 5890737 3.5X
A speedup of around 20x.
