Here by way of a recap the tried-and-trusted fix for tube-inserts, except for the upper posts a single rivet will do because these are going to bear the load of the flight-deck and I've no plans to be flying inverted at this stage. The undercarriage legs a different matter however as they're subject to loads in various directions during flight operation and road transport.
Incidentally there are of course proprietary adhesive-fillers much like silicone, though these are a one-way street whereas using silicone (and once the rivets are drilled out) you don't have to be King Arthur and his Excalibur if it comes to re-jigging prototypes. For instance we always have the option prior to flight-testing to alter the dimensions of these corner-pieces, and in fact for a beta-product I like the idea if them ALL being the same length of only to reduce the parts-count.
After a little to and from in the head however I have elected here to use whatever I've left in the 'shop in the way of off-cuts and this has resulted in posts of 4" length and legs of 7". This is quite nice as it makes (including the depth of the tube-connectors) for a basic airframe that is exactly five feet by one. The Europhiles will be wondering if ever I am likely to publish in millimetres, but propellers are the starting point here and the Western world still uses inches for these... so start as you mean to go on.
(This is not exclusively so, for 25mm and 1-in parts are broadly interchangeable for our purposes here.)
Note too that the undercarriage legs are braced laterally by kitchen-cabinet brackets. (Always ask your local shop for aviation-grade brackets, along with a long weight and a sky-hook if you're new to the project.)
Finally all aircraft have at the outset to consider the logistics of ground operations, for which the key here is my one- by two-metre flatbed trailer. We could go smaller on the frame with 36" propellers, but this would mean it wouldn't clear my wheel-arches. At the same time it's looking like the motors are going to be top-mounted as it makes trailering altogether simpler, beside upping the ground-clearance that we looked at in the previous post.
On the other hand nothing in life is for free, and that does mean that the flight-deck may yet need to be raised a little higher on those corner-posts as there is just an inch of clearance at present, which is tight even for those carbon-fibre freaks amongst us.
