Project

Having had many flying wings over the last six months of 2009 I thought maybe with the cold short days and long nights, time for a little project that's been on my mind for a while now.  The Superwing has been in bits in the "hangar" awaiting a new power pod made from grp for more impact resistance.

A member of the club, Dave Bright flew it last, blasting it at full bore down centre of airstrip before climbing vertical then power back and descend in a rush back along the airstrip with a scream and whistle of air.  A few days later I attempted a similar stunt and tipstalled it into the ground.

So, seeing it looking rather dejected in bits it was time for a new look and facelift.  And so the project begins.....

With the codename of "Marley Fighter", you will see why very shortly it was time to breathe life into the Superwing under a new cover.  For now I decided to keep the 200 watt outrunner with the 6 x 4 prop seeing as it pushed the wing along easily before.  Will also keep the 3S LiPo 11.1v and the 40amp ESC with bec.  The Superwing used the same set-up but in the forward bay a fair amount of ballast was needed to get the CG right.  The plan was to avoid doing this and use the hardware to balance the model.  To achieve this the battery pack needed to be way out front or at least past the nose's leading edge.

The Project

Using the pre-built EPP wing of the Superwing (based on Irvine X-IT) stripped off loose tape so I could recover it to make a little more presentable.

The forward bay really needed to be filled with something to act as a crash/crumple zone so I filled it with a piece of packaging foam and then sealed it off.  The bay behind is normally the receiver bay with access from the underside.  For this version because of the modification I sealed off the underside hatch too.  Using a craft knife cut away the top side above the receiver bay.  It doesn't require a hatch.  At this point I replaced critical glass fibre 2 inch tapes and recovered the wing in my chosen colour - white.

Why Marley Fighter?  Well the fuselage in the picture above is made from 2 inch Marley guttering downpipe.  I could only find black in my local DIY store but I expect white is available too.

After a few calculations and measurements I decided that the fuselage needs to be 13 inches long.  This will give a 4 inch nose not including the "rad-dome" on the front and approx 9 inches on the wing surface.  The nose cone or rad-dome was made from a slightly modded 2 inch spinner.

The Fuselage

I already had a profile template of the Irvine EPP wing root so this speeded up the process somewhat.  I wrapped a piece of A4 paper tight around the 13 inch (325mm) tube taping with tape and also taping it at one end to stop it sliding.  See photos.

Using the rolled paper edge as a guide I laid my template on to the tube with centre line parallel with paper edge.  Without moving the template I marked out with dots the profile on to the paper tube.  Join the dots up carefully with a pen to get a solid line.

Then using the other side of the template laying it parallel with the previous marked out profile measured where the front leading edge would be and moved the template until there was an inch and half between the curve points. Measuring down 2 and half inches from the curve points the lines should be half inch apart.

With the wing profile now marked out it was time to cut out the material  within the lines.  I used a power jigsaw fitted with a medium cut wood blade.  Too fine a blade and the plastic melts and gums up the blade - too coarse a blade and it will rip up the plastic in shreds.  Following on the outside of the lines I cut out the proflies.  Cleaned up the edges with sandpaper and craft knife.  Next was to push the fuselage on to the wing along the centre line to get an idea on how muck more needs to wittled away with a craft knife to get a reasonable fit.  See photos.

Next job was to glue in the nose cone made from 2 inch spinner.  the base section of the spinner is slightly bigger than two inches so some had to be cut off using a craft knife till it just slides into the tube and sits square.  Plastic waste pipe glue (plastic cement) stuck this firmly within minutes.  Putting the cone in now gives the front of the tube rigidity for the next job.

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Battery Hatch

Depending on your choice of battery this may differ - I am using a LiPo 3S 2200 which measures about four inches long (100mm).  Therefore the hatch access needs to a little longer by about 10mm and 30mm wide.  Sticking a piece of paper again on to the tube directly above the the wing cuts.  Measured 10mm back from edge of tube and made a mark.  Then another mark at 110mm.  Drew a line - this will be the centreline and should be directly above the wing cutout.  Using this centreline drew a box 30mm wide and 110 long.  Using an 8mm drill I made some starter holes for the jigsaw blade, then proceeded to cutout the box along the inside of the lines.  Keep a little bit of this plastic for use shortly.  Cleaned up around the edges and tested to see if the battery can be tilted and slid into the space.

To make a hatch  I laid some paper on to some more gutter pipe at the end.  Taped in temporarily in place. Now drew a box 5mm longer and wider than the fuselage's cutout.  That is 120m long and 40mm wide.  Cleaned up edges.  Using a bits of the waste plastic from the fuselage cutout I made a spigot 15mm wide and 25mm long.  I also made another similar but this time only 20mm long. At one end of the hatch cover i used plastic cement to glue the shorter spigot longways and butted up to the edge of the cover. once set i then glued the longer spigot on top making sure that 5mm sticks out proud of the hatch cover.  This will clip the hatch cover under the fuselage top for security.  In my version I am using an elastic band to hold down the other end but you could always use a rotating clip and long as it ensures the battery doesn't fall out in inverted manoeuvres.  See Photos.

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Final Stage

With the fuselage complete now with hatch and wing profile sorted it's time to put the two items together.  First of all I cut a piece of Correx 60mm wide and 100mm long - this will become the lower securing plate for the fuselage.

I had to nip off the tip of the wings nose by about 15mm to accommodate the battery and to ensure a snug fit for the fuselage.  Using the wing join as a centre line I pushed the fuselage on to the wing till it just touched the leading edge.  I left a little gap here to allow air to pass thorugh for ESC cooling which would be hidden in the fuselage tunnel.

Using 50mm fibre glass tape I secured the fuse on the underside of the wing across the little tab.  Now ensuring that the fuselage hasn't moved I measured back from the back edge 50m.  Now each side of tube in line with this mark I placed two pen points close to the fuse tube.  Drilled right through the wing at these points with 4mm bit.  Using the holes as a guide drilled through the Correx piece too.

I used 4mm wide cable tie passed through the correx, through wing, over tube and back under again.  Just for extra security I made a 5mm slot with a soldering iron at the top of the tube curve.  This will allow the tie to drop in a little stopping the chances of the fuselage sliding.  Now pull the tie reasonably tight and that's it done.

Now with all hardware installed time to check CG balance.  Compared with base Irvine the CG was little forward of 7 3/8 inches but being slightly nose heavy is better than tail.  Only a flight will tell.

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The test flight was made into a light 4mph cold northerly and the project soared away in to the blue sky.  A cfiar bit of trimming was needed but the original wing was like that anyway.  Flew fast and predictable and landing with power off was just like a dream.

The maiden was made a Stanpit Marsh which is a little restrictive but local to me.  Final trims and performance can be sorted out at Cashmoor.

This may be one of series which I will call "Star Fighters"  Let's see how far we can push it!

See also Blackbird article...