Today we decided to install a shelf for the GRT magnetometer and chose to mount it on a shelf suspended from the longeron just under the upper skin in the bay behind the baggage bulkhead. (See image #2) We decided to use some aluminum sheet for a shelf but in order to make it more sturdy we would bend flanges which we did using the brake seen in Image #1. We fit it all together, disassembled it, primed it and then reassembled it and riveted it together. In Image #3 you can see that we have the shelf anchored to the longeron with #8 nut plates so that we can remove the shelf it the magnetometer needs attention later. We approximately 18 " from where the canopy frame will be and we hope that that will be far enough. Tomorrow, however, we will install 2 more nut plates further back in case we have to move it because of ferrous interference with the magnetometer. If we do have to move the shelf back further, it will be more difficult to remove it if necessary. I think that I read that one could check for interference with a cheap compass. I will try to find a Boy Scout one to give us a hint.
