Baby Blender and build evolution!

by alibopo | March 17, 2013 | (12) Posted in Projects

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!) 

COMMENTS

mattplaneflyer on March 22, 2013
Sweet! it looks a lot like a slow poke.
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cloud9photos on March 22, 2013
Looks like a PT-19 very cool!

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sailorJohn on March 26, 2013
More great ideas thanks
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alibopo on March 29, 2013
Hi, I'm fiddling about with a method for 'pinching' the foamboard edge together to form a sharper edge. I used to make seat cushions for boats and to get a rounded 'bull-nose' on the foam we just smeared the end with contact glue, let it set and then folded the top and bottom edges in towards the middle. The end shape was a very neat curve. I'm running a skewer down the middle of the edge to pre-compress the foam inside the foamboard then brushing Copydex into the gap. Once the glue has dried properly - about twenty minutes, it pinches and stays pinched giving a nice rounded edge. Only problem I've had with the copydex is that it seems to be able to be completely pulled out again if you start picking at any glue 'blobs' that are sticking out - completely emptying the join. To be completely sure of the join, I need a contact glue with a bit more hold that won't 'eat' the foam.
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alibopo on March 29, 2013
More on the edge detail - I've found that the formed edge adds a fair bit of additional rigidity to the foambaoard.
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WizzyWiggs on March 23, 2013
Are you going to post a video of it flying? I wouldn't mind knowing how it flies. It looks awesome!
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alibopo on June 3, 2013
Hi, video now up!
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Flyin SpYder on March 28, 2013
Beautiful! Awesome job man!
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Rc Mania Cyprus on March 24, 2013
Is that the turnigy 2211 1700 brushless motor.What prop and esc are you using?
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alibopo on March 29, 2013
Hi, Yes, I just went with the early pod package suggested by Josh. Hopefully it'll be enough. I've a more powerful motor available which I'll build into a new pod just in case. Checking the weight against the old fogey, I don't think there will be any problem - proof is in the pudding though! It's been windy for about two weeks now, with no signs of it letting up. As soon as I can, I'll get out and give it a maiden - see how it goes.
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Rc Mania Cyprus on March 29, 2013
Thanks.Please post a video on the maiden.I hope it goes well.And if you do please reply to this comment with the link.I want to see how this baby flys.Thanks for sharing!
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alibopo on June 3, 2013
Hi, video now posted.
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Rc Mania Cyprus on June 4, 2013
Great video!And that take off!
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Skipp2Maloo on March 20, 2013
That looks great!
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Nmackey on March 22, 2013
This looks awesome! If you ever come up with any plans or dimensions, I would love to build this. I could see making the wing with the technique used for the ft3d.
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alibopo on March 29, 2013
Hi, I'll put together a build sequence for my wing and post it soon - basically it's just a reinforced Armin wing.
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Baby Blender and build evolution!