I got cheated out of 6mm! Anyway, I bought two sheets for the princely sum of $2.75 each. As this will be
a "stretched"version, I figured I would need two sheets, one for the actual frame, and one for the
assorted bits and pieces.
A virgin piece of 2mm coroplast. Actually, on the sticker it said 125x80mm, but the sheet was only 119x80.
I got cheated out of 6mm! Anyway, I bought two sheets for the princely sum of $2.75 each. As this will be
a "stretched"version, I figured I would need two sheets, one for the
actual frame, and one for the
assorted bits and pieces.
The main frame cut to size, the various lines drawn, and the various bits and pieces cut & ready. A word of
advice; check the flute direction before cutting out all the pieces! (don't ask...)
The nose doubler should be positioned about 8mm behind the nose, so I drew two guidelines.
Spread contact glue (Bisonkit Contact adhesive in my case), put in place, weigh down with some books, and wait for the glue to dry.
A small modification. I plan to have only one fin instead of the two as per plan. I will hold the fin in place
with two BBQ sticks. One in the bottom doubler, and one in this piece of coro. The fin will be held in
place during flight with some tape.
Servos in position. My standard treatment when using glue on servos is some masking tape around the servos,
and a piece of shrinkwrap. A small dot of contact glue on the shrinkwrap to keep them in place.
The recommended tiewraps are 4.5mm wide. Mine are somewhat narrower, so I used two on each servo.
As this is a 150% enlarged version, it was recommended to me to put a spar in. I epoxied this 4x4mm spruce spar in place.
The cutout for the pushrod.
Ready for the dreaded folding...
As I have never folded coroplast before I tried it out on a piece of scrap coro. I used a pizza cutter to
crush the walls. I found that, as long as you go slow, and keep the pizza cutter in line, it should be no
problem to get a nice straight line.
And than just fold...
And now on with the real stuff...
After some trial folding I traced 25mm along the TE and squirted a fair amount of glue along the TE. I spread
the glue with a piece of scrap coro, waited a minute or two, untill the glue started to look matt, and prepared
to fold and clamp the coro. Here I needed a third hand to keep the corner piece up, so that I could get the
pushrod in place. Other then that, no problem. I put a piece of wood over the TE and climped it down with three clamps.
After a few minutes I heard a loud *CRACK*, and found that one clamp had broken! That's what you get for
being cheap. While I rushed to get something else to weigh down the TE, another loud *CRACK* was heard!
So back to the low tech version of clamps. Heavy books...
Both sides folded & glued.
I had a bit of trouble getting the nose and spine doublers on. Till now, all curing of glue was done
either clamped or weighted down. Here there's no way I could put weight on the doublers to let the glue cure,
without bending the underlying coroplast out of shape! So after some trial and error(s) I realised that the
only way to get this done is go panel by panel, and apply pressure by hand. I did look a bit stupid holding
the Mugi in the same position for 20 minutes. But my family is used to that...
Here's a top view from the nose.
The spine doubler.
And the underside of the nose. You can see there's a gap from the nose doubler. I'll cover this with tape.
And the belly doubler.
To (hopefully) prevent any warping, I inserted a carbon rod into one of the elevon flutes. Attaching the
elevon was uneventfull, just some fibertape on the elevon, hold the elevon at a 45* angle downwards and press
the tape onto the TE with an old creditcard. And then attach the control horn. I like to use a Dubro EZ
connector for easy adjustment.
Just for some more peace of mind, some fibertape on the nose.
For some more peace of mind, I covered the tiewraps from the servos with some fibertape as well.
As I want only one (removable) fin, I made my own design. Some tape on the LE to increase aerodynamics, and
fibertape on the bottom for durability.
Two carbon rods were inserted, and CA'd in place. They fit in the belly doubler, and the extra piece
of coroplast I glued in previously. Initially I wanted to use BBQ bamboo sticks, but they are 3mm and
will not fit. As I still had CF rods lying around I used those.
You can see here the fin in place. It's kept there with some tape, so I can take it of for easy transportation.
I also added some blue tape, for ease of orientation. It's an arrow, so I know which way we're going...
All up weight is 570 grams.
So, with a 600mm root, zero mm wingtip, and 600mm wingsweep, the CG should be at 300mm from the nose.
Add a 1190mm wingspan and the calculated Wingarea is 3,570 cm2, which gives a wingloading of almost 16 g/dm2.
