Monday, February 07, 2011

Bagging and Baking Neil's Frame

With all the joints wrapped in Carbon it was time to "bag'n bake".  First step was to close the frame openings with the UHMW plugs.  The plugs also serve to keep the BB and head tube "round" under heat and vaccum.  The UHMW actually expands in the oven and are tight when hot.
Next step was to carefully cover the carbon wrapped joints in release cloth.  I use an Airtech product that has a very fine weave.  I try to make it smooth and wrinkle free but it turns out it does not matter that much.
After that it's time to cover each joint in bleeder material which serves to distribute the vacuum over the joints and soak up excess resin pulled out of the prepreg under vacuum during cure cycle.
The final step before baking it to apply the vacuum bag.  I choose to enclose the frame with a fold between the stay.  It's a bit more work to get the bag sealed but does not apply extra side load to the stays.
Here it is post cure in the oven.  It was hung from the top of the oven but it fell down during cure.  Note to self, get a right angle air fitting for the vacuum seal.  I think the bend in the air hose pushed the frame off when the door closed.  Next oven will have a window!
In the above photo you can see the heat dissipating plate I installed after the first test frame stays failed under vacuum due to localized overheating.  This time there were no issues.

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