We got an update last week from “Mastachussettes” that the Composite Engineering team was pushing to complete the fabric braiding of our new mast around the aluminum wing-section mandrill. That was the cue to get on the airplane to go help with the fabrication work. I was resigned to, and kind of excited to see, the process of building the vacuum bag and infusing the epoxy resin. But the team worked hard Tues/Weds to get it done, and while I flew overnight SFO-Boston, the new mast spar was baking in the autoclave. What a relief to see this upon arrival…
The carbon fiber is hidden under all the vacuum bagging supplies. Red is the air-flow-enabling mesh. Green is the peel-ply that faces the carbon fabric. Orange is the actual vacuum bag film. It took five hours to remove all this stuff and get to the bare mast section.
While I was doing the stripping job, the CE guys began pulling the aluminum mandrill out from inside the new spar. It had been coated with Teflon prior to he fabric braiding, to enable separation. When we first opened the autoclave, for ten minutes we got the much welcomed cracking sounds of the epoxy separating from the aluminum. But there is a huge amount of surface tension in these things, and it takes a big chain-drive rig exerting somewhere in the 20,000+lb range of force to pull the aluminum section out. A plate that is just larger than the mandrill but smaller than the new carbon spar holds the carbon back while the mandrill is pulled against the big steel table.
Here’s a peek inside from the top of the mast; you can see the aluminum mandrill descending down the column.
Because the mast is tapered at the top, the first 8 feet or so pulled out nicely. That’s shown in this video where you can see it moving.
But after that, things slowed down and we spent all Friday taking turns operating the big machine, only getting a half inch of movement with each 10 second tug. After a half foot we have to let the machine motor rest / cool down. I’m writing this during one of those cooling cycles, and this crap will go on though tomorrow probably. Think slippery thoughts. Thx