Friday, February 6, 2015

First Double Bias Layup on Second Aka

Here are a few shots of my evolving technique for laying heavy 12 ounce double bias carbon on an aka over wood and pultrusion.


Cut the cloth.  I was using about 4 foot sections.  On the first aka I used longer ones, but they were difficult to handle.  They also did not want to conform to the curve of the beam well.  They would trail off over the side make for uneven overlap points.




Prime the raw plywood on the beam.




Start wetting out the cloth.  This stuff soaks up crazy amounts of epoxy.  You need to use plenty and be very patient about getting it thoroughly wet and even.




I spread a wave of epoxy back and forth making sure to get all edges.  I have been using a very liberal amount.  Excess epoxy rolls off the cloth, but can be scavenged back to the middle.  After one side is wet I flip the cloth and start over.  Usually the other side of the cloth is only about 10% wet when turned.




Once both sides are quite wet, I fold the plastic over the cloth to create an envelope.




The envelope is squeegeed with heavy pressure.




The squeegee creates a wave of air and epoxy.  It is very difficult to see how wet the cloth is prior to this.  I pull the epoxy in about six directions (+-90 and +-45).  I flip the envelope and do it again on the other side. At this point, I'm pretty sure that it is wet all the way through.  I carefully peel back the envelope and the peel off the cloth.  This needs to be done with even pull as one does when removing tape.  Uneven peeling will distort the cloth and fray the edges.




The cloth is transported gingerly to the aka.  I have been overlapping about a half inch.  The wet cloth is firmly milked  across the beam with the gloved hand  I Want it tight and smooth.  

Later, the rise in the overlap will need to be carefully ground back smooth. I only want disturb the second layer and feather it in.



Peel ply is stretched across the surface.  It gets wetter than this picture as it is worked to get the air out smoothly.  The peel ply is a lot less compliant on the curves than the carbon and usually needs a few darts along the sides.


Task time: 4 hours
Total project time: 362 hours 

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