Using LEXEL sealant to set the fins on the airframe.
It's been so long (4 months) since I attached the vacuform ABS corrugated body wrap to the airframe (see post #36), I forgot how fun it is to work with LEXEL. LEXEL spreads like soft butter, doesn't string, sag, or run, and remains flexible after cured. It is a 'gorilla glue' of sealants, so I successfully used it like glue between the ABS wrap and paper body tube, creating a flexible 100% surface bond.
In this recent pic, look at how the fin mount tabs (
furthest from the camera) actually got compressed toward the body tube as the LEXEL cured inside them. The tabs
closest to the camera are on an
unused corrugated roll from a second kit, held there for comparison. My theory is that if the LEXEL has filled all the air gaps between the ABS wrap and body tube, and I also glue the fins to the ABS wrap with LEXEL, filling all the air gaps, then there is a continuous 100% flexible surface bond between the body tube and a significant amount of surface area inside the fin roots, with a sandwiched layer of ABS. For the joint to fail, the LEXEL would have to fail.
Gluing the fins was a snap with the LEXEL.
First, trimmed some scrap styrene sheet to make little plugs for the big void inside each fin, as these spaces will be filled with LEXEL. Glued the plugs in with Plastuct Plastic Weld. In the pic below, the fin on the left was done, on right still waiting for a plug.
The are 4 voids at each fin root. I filled the bottom and upper middle void with LEXEL, then flattened it with a putty knife, making sure the void was completely filled for a 100% surface bond.
This is a bad photo taken of the third fin with bottom and mid-upper void filled with LEXEL, before the LEXEL was worked with a (messy) putty knife. The LEXEL is easy to work with. Lesson learned: next time clean the putty knife (with mineral spirits) after each fin.
The fins attached like they were born to do; used a thin rubber band for peace of mind. No drips. I love it. We'll see if I still love it in 40 more hours, if the LEXEL cured enough to endure a test flight.