Well I finally got back to work on my poor Robin!! This work stuff keeps getting in the way!! I had originally been scheduled to travel to Charleston South Carolina for 3 weeks. I am (or was) an MRB engineer specializing on the Boeing 787. My company (Triumph/Vought Aerosystems) designed the aft portion of the 787. They call these sections 47 and 48. 47 is the last pressurized section and 48 is the first unpressurized section. during the design I was the lead engineer for all metal structure in section 48. Separating the sections is a huge composite pressure dome ironically built and designed by EADS the parent company of Airbus. I went to Charleston to help with an issue relating to some detail parts. I was working with a young woman MRB engineer on this same project. We were a day into the job when she got up from my desk and excused herself for a few minutes. She walked around the corner past a partition. I did not see her, but I hear a sound that sounded exactly like someone smashing a pumpkin. The next thing I heard were shouts for an ambulance and when I stood up, I saw her face down on the floor. She had had a mini maul seizure and fell directly and unprotected on to the concrete floor. The poor thing fractured her skull and had to have immediate emergency surgery to stop internal bleeding. Because of this unfortunate incident, I agreed to extend my trip an extra week to cover for Tracy.
Anyway, once I got back I started immediately on the lower cowl mold. before I left I had the plaster all prepared and waxed in preparation for the fiberglass tool. The surface of the plaster was sprayed with a mixture of 50/50 shellac and alcohol. This mixture will soak into the surface and seal the porous surface of the plaster. after the shellac was applied, I put 7 coats of Carnuba mold release wax. machined buffed between each coat. The final release agent is a product called Partall 10. This is a polyvinyl acetate water soluble film. because it is water soluble and hygroscopic (absorbs moisture) it is applied no more than 24 hours before the application of gel coat.
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| gel coat gun |
This is my newest toy, this is a commercial gel coat gun. The plastic cup is replaceable and is used to mix the gel coat and hardener. It clamps up to the handle assembly and dispenses gel coat through a huge nozzle (.080" dia.) The gun is held upright when it not spraying. Because the cup is disposable, clean up is a snap, although I am reusing my cup.
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| lower Master with Gel Coat |
This is what the master looks like coated with Gel Coat. The gel coat is laid on really heavy, I shoot a surface that is almost too thick to not run. I like a thick gel coat surface because it allows a lot of clean up sanding in areas off the tool surface.
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| fiberglass mat |
After the Gel coat is shot, you wait about 30 minutes until its very tacky. at this point raw resin is brushed onto the surface to ensure a good bond between the gel coat and the fiberglass and mat. I pre cut the mat into9' x 9" squares. The mat is set into the raw resin and then allowed to soak up. additional resin in brushed into the mat and allowed to soak up. I usually work in sections while the mat is soaking up resin. Non direction uni roving mat is a product produced in sheets. They use a starch binder that will dissolve eventually in the laminating resin. after the mat has wetted out, a mat roller is used to drive out the air bubbles.
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| another view of the curing mold |
After resin cures, the mold is released. Becaue the Partall 10 is water soluable, a small crease is created with a plastic wedge and then water is sprayed into the mold. its just a mater of minutes before the Partall dissolves and the mold releases
