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SportAir Wrap Up

May 16, 2011

Well we finished the workshop.  It was pretty quick, actually.  We were done by about 11:00am.  The instructor had us finish our projects from the day before by removing the peel-n-ply (used to prep fiberglass for painting) and then sawing the board in half.  One of the halves was then setup perpendicular to the other and then we learned about laying up an inside corner.

Here’s Gayle working on the first project.  It consisted of a flat piece of foam which we glassed on one side and let cure over night.  There are several class sessions where the instructor goes over unidirectional and bi directional weave, micro balloons, flox and epoxy.  Like anything else, this is as much art as anything.  We certainly weren’t going to win any contests.  Next we worked on our canard cross section.  You start with a big blue block of foam.

Big blue block of foam

You then lay templates on two sides  and using a hot wire, you and a partner melt through the foam to create the rough shape of what you’re building.  We next laid down the “spar” of the canard.  The spar needs to withstand forces that only stress it in one direction so we used unidirectional glass weave, or uni for short.  Below, the uni sits in the channel we cut with the wire.

After laying on the uni we worked on the Bi-Directional, or bid.  Bid is woven in a very common loose weave pattern.  The bid covers the canard and adds a tremendous amount of strength to the whole things.  Of course the bonding agent is epoxy.  This is the best material for aircraft work.  Its only drawback is heat.  You’ll never see a fiberglass plane painted anything other than white because high temperature does bad things to the glass.  You can heat cure it, but this only adds about another 40deg to the heat.  A fully heat treated fiberglass plane can withstand tempertures no greater than 160-180 degrees.  Certainly hotter than a ramp in Phoenix in August, but what about the hangar?

This was about as far as we progressed on day 1.  The composite class is a slave to time.  Everything we did requires a cure time that is measured in hours.  In metal you just need to cut, rivet, measue etc.  When you get to the end of a task you just move on.  With Fiberglass you have to wait for stuff to dry.

On the second day we got a demonstration of vacuum bagging.  This is cool.  I’ll try to describe it, but you really have to see it.  You start out with something you want to fiberglass.  Next you lay on your cloth and epoxy.  Then you place it on successive layers of material (plastic, varoius types of cloth) all meant to wick away or absord the excess epoxy in a part.  You seal everything into a plastic bag, which we attached to the table we were working on.  The vacuum is left on the part for several hours.  You then turn the vacuum off and let the part cure overnight.  What you are left with is a nearly perfect part with just the right amount of epoxy evenly distributed throughout the piece.

Our instructor, John, putting the vacuum bag together.

After this we got to work on our projects.  We took the first piece we had done, the flat piece of foam, and cut it in half.  We then placed the one half on top of the other half perpendicular.  We then practiced filling in the corners with micro and laying on 3 successive layers of glass until we had something that looked like this.

Not pretty, but we got the point.

The second project, the canard section, was next.  It was pretty much the same as the day before.  Lay on the uni, then the bid and epoxy it together.  The finished product of that, looks like this:

No beauty contests will be won here.

Even though the core of this thing is foam this is how strong it is.

super strength

This canard section doesn’t even weigh close to a pound.  It is very light.

And that was it.  We were done by noon Sunday.  The only sorry thing that happened to us came on Sunday.  Gayle and I were packing up and she couldn’t find her T section project.  After looking high and low we determined that some scumbag in our composite class stole it and left the classroom.  I got an email from the EAA guys later.  Turned out one of the participants left early and didn’t turn in his evaluation sheet or get his certificate.  For whatever reason he decided to steal Gayle’s project as well.  The instructor told us if we come by the SportAir tent in Oshkosh this summer, he’ll help Gayle make another one.  Pretty cool of them.

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