Yesterday was another one of those days in the Garaggio. The day started out amazing with a breakfast flight in the Legacy up to Sedona. A classmate from the first airline I worked for, Ryan, was in town on a layover, so . During the project tours, Ryan asked if I ever had bad days in the workshop. Maybe he knew something about yesterday I didn’t.
The mission for the day was to layup and vacuum bag TCSN2. Friday evening, we had prepared all our plies, consumables, etc and ran out of time to do the actual layup and bagging. With everything ready and plenty of time, Kevin and I gave it a shot.
We got the first two plies of fiberglass and 3 mat stiffeners into the mold without any trouble. In fact it went really quickly. Then we put all the consumables into the mold. Peel ply, bleeder bag, bleeder ply, and finally it was time to put the bag film on.
Making a vacuum bag isn’t exactly simple. Because of the complex curves involved in the cowl mold, you need to “add extra bag material into the mold.” If you don’t do this, you will have areas of tight plastic that bridges across the features of the part. The technique to do this is called pleating. Basically you are adding extra perimeter to the bag over and above the flange perimeter to ensure there is enough bag material in the mold to pull down tight.
I have read and heard about pleating. I have also watched Youtube videos showing different methods. It is not exactly obvious how to pleat, where to do put them, or how many you need. Further, any pleat that is not done well is a wonderful place for a leak to be. But none the less, I did my best to put them where I thought they would be useful, in the areas with most curvature.
We then hooked up the vacuum pump and turned it on. We waited, and waited, and waited, no vacuum was being drawn. So we started trying to chase down leaks or places that weren’t sealed. We went around and around and around finding little areas where the pleats weren’t sealed, or the bag had a wrinkle, etc. There seemed to be no changes for everything that we fixed.
By that time we about an hour and a half went by trying to get the vacuum bag to seal with no luck. With the temperatures we have, the epoxy was well past the B stage at that point and vacuum bagging would do nothing for the part. We were only keeping after it in the interest of learning, and eventually causing more frustration. So we quit for the night, resigned to the fact we were unsuccessful with vacuum bagging but may have a useable wet layup part.
Today we de-molded the part. It is in fact a useable tool cowl. The surface of it looks very good for being wet layup, and I can’t wait to get some primer on it eventually to really be able to tell how the surface came out.
As for vacuum bagging, it is a skill I am going to need to learn. Luckily, I have friends that have been coaching me along with the process. I am going to try to vacuum bag an “empty mold,” that way I have all the time in the world to figure out how to pleat a bag and get it to seal. Once I’ve done a few then we will try for making a part with vacuum bagging.