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Monday, July 21, 2008

Joiner success!

Just opened up the second carbon joiner and it's much better!

The tube is 12,5mm id and that takes 159 tows to fill completely so this time I cut 100 which is just over 60%. I also had an extra 20 in case this was too loose after coating with resin. As it turned out I used the extra 20 so my carbon content is just over 75%. It took all my weight on the joiner with the wire in the vice to get the tows through - very slowly!
My method for wetting out was to keep the wire hook in place and place the tows on a plastic sheeting covered bench, pour out about 80% of the resin and roll it with a ribbed roller. Turn over and add the rest of the resin and roll and roll and roll....
Evan just mentioned to me today that he dunks all of the carbon tows into the resin container (whilst keeping the looped end on the wire pull through) and squeezes out the excess which sounds much quicker!
New joiner is 65g, old one was 57 g, better fit and finish plus more strength!
On to the wings next time.

Wednesday, July 2, 2008

Time to do it again!

In the time honoured Jart tradition of learning new and fun stuff - sometimes you have to do it again!

The aluminium tube used to make the carbon wing joiner rod took a lot longer to dissolve in caustic soda than I had thought. Thanks Mike for the suggestion to put Dremel grooves on each side almost right though - even then it took two days to get through the grooves!

The calculation I used was 40% carbon 60% resin (very pessimistic) and when wet out it was way too easy to pull through the tube. I increased the carbon to 50% by area and it was much tighter so I left it at that.

Clearly not quite enough carbon as you can see - next time it's 60% carbon and if that isn't a really tight fit then add a bit more!

Just to make it a full house the motor I installed to power my vacuum pump had a faulty nameplate. It says it's S1 duty rated, i.e. continuous running but this was incorrect leading to massive heat build up and bad smells! It was set to run for half an hour then wait an hour as the vacuum regulator switch is giving problems. (It was not pressing foam but a wing mould so the very high vacuum was ok).

Oh well, the wing is next, just after the vacuum pump is re-built and a quick trip to the Berg next week!

Anyone know where to get a proper vacuum switch – Festo’s one is nearly R1000 while’s sells one for only $25 but won’t ship to South Africa!?