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Queen Elizabeth Build - Stuffing Tubes and Stringers
The next step was to install the stuffing tubes and gear boxes. I will be using 3D printed props from Clark (these are early-design.. the final ones are smoother and even brass-colored!) so I temporarily pushed a pair onto 1/8" brass drive shaft and inserted those each into a stuffing tube. Note: We actually have several clear flaws in the 3D printed prop design (no thrust). Plan to fix and reprint, but I went with some brass props from Battlers Connection that I had on-hand (until I have time to adjust the prop design)
The tubes have to be positioned correctly to fit the props (without their hitting the hull), so I taped a thin sliver of wood around the prop so that I can epoxy the stuffing tubes in place with them resting against the bottom (I use rubber bands wrapping around them and up over the hull to pull them flush against the bottom). Then after it sets I will remove the strip and the props will be as close as that sliver of wood (or you can use an index card) to the hull.
The next step was to position the other end of the tubes before final gluing in place. I slipped the 3D printed gear boxes (from Clark Ward) onto the end of each tube and then kept cutting the hull where the tube comes through until they were both even with each other and as low in the hull as desired (I left about 1/4" below each gearbox - I should probably have cut more until they were firmly on the bottom but this fit cosmetically in the mounts formed into the fiberglass beneath the hull - just for looks)
My method of sealing the tubes in place is to cut a hole in a a gun cleaning patch (or those wing-flap hinge material from the R/C plane hobby seems to work) and slip it down over the stuffing tube. I then mix epoxy and slather it over the patch (pressing it into the patch with the mixing stick) to effectively make a fiberglass patch). Once it hardens the tubes are firmly mounted and leak-proof.
The gear boxes (which will hold the heavy motors) cannot sit out in the air (too much vibration) the gear boxes have to be supported if they do not sit on the bottom of the hull. I sanded a piece of aircraft plywood until it just fit in the hull but rested against the bottom of the gearboxes. I glued the wood to the hull and the gearboxes to the scrap wood.
At left is a photo (taken much later) of the QE motor mounts with the motors in stalled
THEN IT WAS TIME FOR THE STRINGERS!
In order to give the balsa sheeting something to adhere to when there are bends, our hobby sometimes allows for 1/8" stringers to be left on the hull so that the shape will be held. On the Queen Elizabeth protrusions from the armor belt and the first bulge are allowed to be stringers (you can see I left those uncut when carving out the hull panels). Since some of the current cannons fire hard enough to chip away at the fiberglass (especially the thin stringers) it is a very good idea to reinforce them with a strong support behind them.
I used 1/8" x 1/4" basswood strips (1/8" edge against the stringer, obviously) and epoxied them behind the stringer using clamps to hold them in place while curing.
Hard to see in this photo, but (notice the white strips stuck behind the ribs and hanging off back of stringer) to strengthen the attachment of the basswood strip beyond just the epoxy, I cut strips of fibrous paper (gun cleaning patches) coated in epoxy to span the cut edge of the fiberglass window and the stringer, as also to run up the rib and up under the stringer - basically fiber-glassing the pieces together. I went back later and trimmed the excess overhanging material with a Dremmel.
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