UPDATE - see this plane fly;
See the other 'Tribewt' variations in the article - Build a Tribewt & GeeBee Sportster swappable
UPDATE 16/01/2015 here's the plans for this build; Tribewt
So, I had my Baby Blender and thought - what next? Well I loved the idea of swappables, and I did fancy something a bit more aesthetic, so I fiddled with the Baby blender plans - lost a wing, flattened the body and rounded off some of those harsh edges. Here's what it looked like on paper. Sorry about the image quality, it's a pencil drawing and the plan and elevation are a bit 'mingled' around the basic BB fuse drawing. I think you can just see the swappable insert. The body is basically the Baby Blender, with a slight nip at the front. All the basic 'uncurved' BB tail components are the same, but then they get shaped.
I followed the BB build sequence - fitting the swappable frame before folding and glueing the fuselage. I made the wingspan a bit longer - 70cm before adding the foam extensions. I could have made them longer, but I wanted to try and get this plane made from a single sheet of foamboard. I feel they're about right.
The turtledeck formers were the same in the middle as the BB, but I reduced the rear one to match the centre ones and reduced the front one to match the new width at the front. Because the depth of the fuselage was reduced I decided to add extra formers- one at mid point halfway back to the tail and another just before the tail to help stiffen that whole rear section.
Note the cereal pack cardboard used to make the turtledeck! I used the BB cockpit former, shortening it at the front and fiddling and fitting the front and rear panels to account for the new tapers. When I had the body all made up it was time to sort out the wings. All I could really do was go to real life and see what similar aircraft were doing with their wings and their relative positions on the fuselage. I took a lot of inspiration from the Ryan PT 22. Plus I decided to put a diahedral on the wing to make the plane a little more stable.
This construction involved a 300mm length of 2.3mm piano wire with a small bend in it and a couple of popsicle sticks (lolly sticks in the UK) set at right angle to the extremities of the wire to spread the 'end of the wire' force concentration across the wing. (I should have taken pictures!) Anyway the wing build is identical to the BB right up to and including the test folding of the top surface to get the aerofoil profile to form. I do use the folded internal spar, but added my wire diahedral element bedded and sandwiched into it. Once I had the shape forming easily over the whole length of the wing, I split the top of the wing and put a crease along the centreline on the bottom to allow it to fold. Working on one side at a time I glued up the wing with my wire stiffner running through the centre of the spar. Once one side was done I trimmed a little from the mating faces and rocked the wing over and glued and folded up the other side. To account for loss in strength from cutting the wing I added a pad onto the top surface that also helps align the fuselage.
Using a 'wing and a prayer' I sat the end of the wing against the fuselage, marked it with pencil and removed the profile from the side of the fuselage.
When it came to cutting out the ailerons, I realised I'd made a mistake and I had cut out too much from the fuselage. Luckily, I had an exact fitting piece of foam to insert at the back of the wing! (the aileron offcut). This was a handy mistake as it helped stiffen up this part of the fuselage. Also instead of skewering the swappable pod into place, I just packed it in place with the piece of polyfoam you can see protruding at the back there. Incidentally, to remove the swappable pod I have to remove the front wing-mount skewer - no big deal.
I made another mistake with the turtledeck and didn't check the 'grain' of the cardboard in the centre section with the cockpits - this resulted in a bit of distortion, but not so much to justify replacing it. Once I had the basic plane built I added a few cosmetic details. The foam extensions on the wingtips led to aesthetic shaping of the wing trailing edge, and a reduction in the size of the ailerons.
I thoroughly 'painted' the foam with PVA glue before spray painting. This stopped the foam from melting.
The nose detail was another little cosmetic addition in foam.
The windscreens are the ends from a bubble pack of screws - cut with scissors and then marked with indelible pen for the frame and glued down with superglue.
The headrests are cardboard - mini versions of the turtledeck detail on the BB. I added a cockpit edge made from round electrical wire with the core pulled out. That helped strengthen the 'wobbly' edge and hopefully makes it look better.
The black-on-top paintjob followed the natural line of the turtledeck, which made getting a straight line fairly simple, and also copies some 'real life' detail I saw on a number of similar aircraft. The black paint was fast drying water based satin varnish with some black watercolour from a tube to pigment it. I sprayed the inside of the fuselage with hairspray - a cheap alternative to fixative that artists use when painting with watercolours. This gives the paper a thin coat of waterproofing.
It's been great fun and amazingly fast to build using the foamboard and the power pod I already had. As Josh says, almost anything can fly if you throw enough power at it, but I've a feeling this won't need that much. The saving in weight by removing the second wing and a fair bit of fuselage is significant. Plus loss of drag compared to the BB's blunt nose, second wing and high headrest will make a difference. Now I just need to get competent enough to feel comfortable flying it! I'll do taxi-ing hop tests to set up the balance etc. but it seems to balance pretty well at around a quarter to a third way back from the wing's leading edge. Fine adjustment can be easily managed by shifting the battery position. Meanwhile, it's back to the Old Fogey and an RC flight sim on the PC to get my cofidence levels up. Havent thought of a name for this model yet - possibly a 'Ryan Tribute'? (Now the Tribewt!)