Sunday, 14 November 2010

Postcuring daggerboard and rudder

I thought it would be a good to idea to postcure the daggerboard and rudder parts for extra strength, as they are not going to be exposed to much  heat  when in position. It is not strictly neccessary, as I have not been using slow hardener on these parts. The beams on the otherhand I will have to postcure as I used slow hardener on the multiple layers of carbon UD.
 I am reasonably happy with the foil shape. although it has taken more filler/fairing mix than I had hoped for. I used a template CNC cut from the daggerboard DXF file  for the final shaping. Strictly speaking I think I should have postcured before filling and fairing. Hope all the filler does not shrink and crack off!

The heat source. 5 x 60W light bulbs plus dimmer switch. I  have found this to be very controllable.

Heat source under the board. The bottom edge of the board did get a bit hotter than the top, but on the whole the heat rising up from below was quite well distributed., about 5C difference between top and bottom. 

Rather crude cardboard oven. But it did the trick OK ( with a bit of additional room heating to cover the heat loss from the cardboard) . It is suprising how long a large piece like this takes to heat up. (and cool down!) You begin to think that you are not giving it enough heat, but in reality most of it it is being absorbed by the board for the first  few hours or so. After that you can begin to actual get the temp up a bit. As the board has a wooden core, I did not want to get it too hot. In the end it had about 24hours at about 45C. (Cure for the resin I am using is 50C for 16 hours.) Hopefully this will be about equivalent.

Oven No:2 for the rudder/sleeve/gudgeons/composite chainplates/bowpole/forestay backet fitting. A smaller volume to heat up, should be a bit quicker hopefully.

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