It's been a while since our last update. If it weren't for trivial things like work, we'd get a lot more done on this project. Since we last updated the build log, there has been sporadic work on the sentry. The last log ended with a shot of all the pieces. Now, we've been working on getting them all put together and made decent progress.
To start, we got the legs together. The knees were originally constructed with fiberglass pieces for all the curved surfaces with MDF as the flat side to give it some structure. We realized that this left us with nothing structural to attach the other leg parts to. We had decided we were going to fill the body with two part expanding foam to give the shell a strong backing, so we decided that we might as well do the knees while we were at it. We embedded a piece of angle aluminum into the foam connecting the bottom and top connections for the knee, then filled the whole thing with foam to hold everything in place.
This method ended up working well, so that finished off the legs until we start working on surface finish. Then we got started on the time consuming task of filling the body and pods with foam.
One of our other realizations about a month ago was that the fiberglass shell wasn't rigid enough. If we tried to sand it, we'd just end up cracking the paint as it deflected. We decided to pick up some two part expanding foam and fill the body and pods with it to give us a nice rigid backing that we can sand on. The net result is the following:
It oozed out at a couple seams, but overall it's a lot more rigid and because the foam is pretty airy, it doesn't add all that much weight. The above picture also shows off a couple other new features. The body is finally together. We bolted it together before foaming and glued the eye in place. Figuring out where to cut the body pieces to get it to match the eye was a bit of a pain, but I'm happy with the result. After filling the body, we moved on to the pods. All of these were done as a a series of small pours of foam. We discovered that when pouring into confined spaces with semi-rigid walls, that if we poured a little bit, it would expand into the open air, but if we poured a bunch in there, it would have to expand in all directions and cause bulges in the fiberglass. Here you can see several of the layers of foam pours in one of the pods:
It's ugly, but it will all be hidden anyway. While waiting for foam to set, we have also been working on the leg mounting system. We just took pipe couplers of the appropriate size, drilled holes into the structure of the body, and epoxied them in place. Here's an in-progress shot of the bottom of the body while we were doing the mounting:
After all the epoxy set up, we just had to put the body on and get a shot of the thing standing on its own three legs:
The back leg is hidden by the body in this picture. Up next on the agenda is finishing foaming the front and back of the body (we only did the top and bottom before), trimming the foam and putting the sheet of styrene on the inner surface of the pods, and a bunch of finish work. Once the styrene goes into the pods, they'll be mechanically complete.
Hopefully we'll have less time between updates from now on.