The following letter & pictures were submitted by Roger during November 2003.
From: Roger Isackson
Sent: November 2003
I Thought you would find the attached photo [of safe canopy storage] interesting in light of one of your recent posts.
[About fiberglass and resin fabrication,] I attempt to make all of my thicker lay-ups a semi-continuous process. I lay out most of my reinforcements on vacuum bagging film on which I draw the outline of the reinforcement. I put the marker side down so as not to get ink in with the sticky stuff and I use masking tape to keep everything from sliding around on the bench. I lay the glass on the resin painted surface of the film then stipple with a chip brush of appropriate size. I have found trimming the first 1/8 " off the end of the brush with a very sharp scissor makes the process go a lot better. I use no rollers as I hate the way they pick up glass strands along the edge of the cloth. This is especially bad when the orientation is 0-90. I limit the thickness to 4 or 5 plies, any more than that and I find myself losing the shape of the lay-up while chasing bubbles and working resin either in or out of the pack, whatever is necessary. So I put it in place and mix up another batch. Usually by the time I am ready for the next 4 or 5 plies, the previous ones have set up enough so I don't have to worry about moving them around. I know if I can dent the resin with my fingernail I am going to get a good bond.
Actually according to Dows' literature a chemical bond is capable a long time after you are unable to dent the resin. Up to 24 hours I believe. I don't like to let it go that long though.
I use acetone for cleaning brushes mostly. I like to give the surface an initial wipe with a clean cloth and good acetone. But that is where it ends. I then sand with 150 grit and vacuum... twice! I am very careful about contaminates around the shop however. I also like to prefabricate parts on the bench where I have more control of the quality. Whenever I know it is going on a fully cured area that is.
Remember the fix for the fragile balance horns Mike Bowes' shop recommended? I made the fix and am going to send you a sequence of photos. [Included below.]
Composite bulkheads cut for elevator horn
Foam and one side of fiberglass tapered to expose the inner plies for bonding.
Edges of inner plies cleaned and exposed for bonding. Special tool made from spent saber saw blade.
Bulkheads ready for installation into the elevator horn.
Clean-area type fiberglass storage and cutting table. Bonding strips cut and ready for use.
Single ply bulkhead removed and elevator interface BH reinforced prior to installing new BH.
New BH temporarily held with hot glue prior to installing inner tapes.
Tapes installed to bond inner surface to edges. Note the correct wet-out of the fiberglass without any excess of resin. Also note the uniform width of plies.
Fillet and tapes installed to bond outer surface.
Completed BH installation.
MLG Hydraulic actuator anchor.
Safe canopy storage.
Skew chisel fabricated for trimming and cutting.