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Date:  6-10-2015
Number of Hours:  2.30
Manual Reference:  Step 6
Brief Description:  Inspecting Canard upper skin layup

Actually started heating the shed up to permit the injecting of resin into the bubbles, then had a closer look at the previous layup. When looking toward a strong light at an angle to the surface detected a considerable network of small bubbles deep in the layup, as previously encountered in layups where I had got too enthusiastic with the squeegee.

Even without the big bubbles previously noted these fail the inspection criteria by a wide margin. Particularly at the tips and leading edge the bubbles cover 20-30% of the area.

Picture one shoes the mess. The large bubbles on their own would be fixable. Small bubbles are not the bright shiny things you can see on the leading edge. they are bubbles between the layup and the peel ply, but the dull ones much deeper in the layup, the same color as the big bubbles. Some of these are micro bleeding through, but the eye, (but not the camera), can see the difference between dull micro and the more shiny bubbles.

I hit the archive for advice and find a couple of similar instances. Consensus of replies are belt sander or start again, with some finding a better result from their second attempt. I decide to try the belt sander option first, then make a clinical assessment whether to start again or not.

Not your fault Grant :)

I will either have to cut out the lift tabs and throw away the Canard and start again, or somehow remove the fully cured top skin. Have had luck previously with dry layups approx 24 hours old where I can apply heat with a heat gun and peel off the layup, and have heard of others using a belt sander, which I don't have.

Try the heat gun on the spar cutouts from the fuselage sides I kept and even when heated to the burning point it still destroys the foam when pulled off. A random orbit sander melts the foam underneath before removing the fibreglass, and when it does gouges huge divots out of the foam. Hmmmmm.
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Large bubbles are obvious. Small bubbles everywhere

Large bubbles are obvious. Small bubbles everywhere

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More disaster

More disaster

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Some of these are micro, but most are bubbles

Some of these are micro, but most are bubbles

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