Tuesday, 29 December 2015

Glass Slipper (6)

Finishing it off..

The ailerons are rather thin in cross section and I was concerned that they would be susceptible to flutter. Rather than replace them, I simply trimmed the last 3mm and inserted spruce.

Hard points added and a razor saw used to separate the flap from the aileron.

There are 2 x 12.5mm thick wing ribs that are used to fair the fair the wing into the fuselage. These need to be carved and sanded to meet the complex double curve on the fuselage while still maintaining the correct facing angle to the wing. I almost got it right.

These ribs are faced with 1/16" ply which were glued into place before the carving started.

Alignment was carried out is 2 halves using my home made incidence jig to ensure that the wing was at +1.5 degrees

Elevator halves are braced with 14swg piano wire, inlaid into one half and then the other half sandwiched on top. The gaps filled with epoxy adhesive

The elevator Kevlar hinge is sandwiched into the two halves and clamped until the glue sets.Note that the elevator halves have not been separated yet.

The process was repeated for the rudder

The nose was produced by sandwiching some 6mm ply between balsa cheeks and sanded to shape. Still managing to maintain the design profile.

With the fuselage completed, the Fuselage and fin were glassed with 60gm/m2 glass cloth and then sanded back with wet and dry. A couple of coats of primary and finished off with Halfords 'Appliance White' rattle can paint.

The wings, tailplane and rudder were film covered and after a little work, the model looked like this.

And underneath..

The maiden took place on the 22nd November 2015.

Ian Jones and I went up onto Bosley Cloud (near Congleton). The wind was flat calm at the foot of the hill so we were anticipating a wasted journey.

As we approached the trig point, we could see a couple of models already in the air and we were greeted by a 15mph North North Westerly.

Ian went first - he had brought a couple of foamies.

I assembled the model and pondered... and pondered.. and pondered (as you do before you maiden a new model) when one of the other fliers present picked the model up and said he would launch it. 5 seconds later it was airborne.

It needed 2 clicks of right and 2 clicks of down and it was flying straight and level. A tentative waggle of the aileron control to test the responsiveness and they seem OK (the ailerons look rather small) and by now - within a minutes it was probably about 100 feet up and well out from the slope. One of the benefits of a light wing loading and clean lines.

So I whipped it round for a couple of low passes.


And thanks to Ian, a short video of the event:

Friday, 23 October 2015

Glass Slipper (5)

The wing. I spent quite a lot of time wondering how to build the wing. At first sight it looks quite straightforward, however, the curved LE and spars will generate lots of strange stresses. This means that the wing need to be assembled and sheeted while still pinned to the building board.

Before I start though, I need a full set of wing ribs. These were supplied by LaserCraft Services for a reasonable fee, cut from DXF files that I supplied

The only straight edge that I can work from is the hinge line for the ailerons or just in front of it.

To make sure that it stayed straight, a wooden straight edge was screwed to the building board and  the wing was assembled from that point.

So with the position of the false TE established, lines were drawn representing the rib positions.

A 1.5mm spruce false TE was cut and the ribs glued into place pushing back against the false TE. This was aligned to the upper edge of the ribs like this

Assemble the wing as you normally would

Note the false LE held in place by suitable weights and curving back as the ribs are fitted. It took a couple of sessions to get them all in place

The spar is laminated from 4 of 3mm square spruce strips at the root, tapering to 2 strips at the tip. A slight change from the plan. I originally intended to taper each spar backward - in the end, I used a stepped taper to get the correct fit, adjusting the spar slot in the rib until I get a nice snug fit.

This was the junction from 4 to 3 laminations with a slight taper on the outer spar

After the spar was fitted it looked like this, small 1.5mm gussets added at the rib/TE junction and then the wing was sheeted over - while the wing was still pinned down.

Left to dry/stabilise for 24 hours and then removed from the board and very quickly adding the lower spar and shear webs for the length of the panel

Don't forget to fit the servos. These are built in with  no hatches, if a servo fails it will be surgery to replace it.

The servo bearers are cut from 10mm square pine (B&Q) and simply glued to the upper sheet. The servos then are located in a lite-ply frame and glued and screwed into place. Align the arms before you proceed, there is no easy return path if you this wrong.

The wing joining tube is fitted and thoroughly glued into place.  The tube is glued against the webs - this makes a nice load transition from the aluminium tube to the spruce spars. The end stop is a 3mm off-cut of the joining tube epoxied into place

Finally, a small hardwood ply plate to hold the wing retaining screws

Add the lower sheeting (after removing the building tabs) and when dry, trim back to the false LE

The real LE comprises of a balsa laminate capped with a spruce laminate

and held in place with bands while the glue dries

The wing tips are laminated from 2 x 3/16 sheet balsa with a 1/32 ply core and glued into place

and the joint reinforced with a strip of Nylon - well soaked in PVA

The process was then repeated for the other wing half..

Glass Slipper (4)

The fuselage close to completion

Getting the last few planks in was quite tricky, just lots of patience required.

The canopy was acquired from Vortex Vacforms - CN39 Glider canopy - and extensively cut down to size. I am really pleased how well it fits and importantly how the fuselage lines have been maintained. Rather better than I could have hoped for.

The fin and tailplane came next.

The fin is a thick sheet balsa outline with a support for the tailplane

All very straightforward and all using very soft/lightweight wood.

It was simply glued into place checking for vertical - using the joiner tube as a datum in this case.

The area between the fin and the rear fuselage is simply blocked in using light 12mm sheet balsa.

Finally, the tailplane was added - laminated from 2 sheets of 3/16" balsa to get the desired thickness

Extensively carved, planed and sanded before it gets glued into place

Now with the rear block carved and sanded, it's hopefully getting its elegance back again

The tailplane is sandwiched between 2 x 12mm blocks and then sheeted in - not forgetting to fit the elevator and rudder push-rods first!

Like this

Which completes the fuselage assembly and we can start on the wing

Flair Meteor

I bought this 35 year old kit at a recent UKCAA event with strict instructions that it had be be built not stored. I remember the kit from a long time ago although I was (and still am) having problems dating it. Estimates are that it was produced from the late 1970's into the early 80's

The kit is a  fairly basic constructional specification, foam wing and a very distinctively shaped glass fibre fuselage. It's quite a small aeroplane - about 52" span and originally designed for a 40. The planned modern 46 will make it very fast flying.

 The original box was rather large and was cluttering up my workshop so this was a big incentive to get started. Additionally, I had spare moments available during the Glass Slipper build and the opportunity was too great to ignore it.

 The photo on the front - it looks very 1970ish

I was quite fortunate that the previous owner had bought some new foam wing cores. The rest of the materials were as original with some beautiful quality balsa - which was very dry.

One of the earlier owners had made a start - and a bit of a mess gluing the bulkhead in place. The surplus resin was removed with a Dremel and sanding drum and the former re-drilled to suit an engine mount that fitted my chosen power plant  - an SC46 from my recently departed Gangster 63. You can also see the ply shim added to provide a little right thrust.

 The engine has recently been serviced with new main bearings, has good compression and has so far been very reliable.

The engine mount held in place with cap head bolts and blind star nuts. The quality of the piano wire was excellent - black - high carbon steel - far better than the rubbish we get nowadays

The tailplane was fitted - it was very simple to align as there is no real option - the moulded slot simply fitted and then I added the full length elevator hinge blocks, using Kevlar cloth as the hinge material. The only critical part was getting it centred and also triangulated to the centre at the nose to make sure it wasn't skewed.

Likewise, the fin, rudder and rudder post simply slotted in and was almost guaranteed to be vertical. Slow setting epoxy was used to hold it all together. By modern standards, the rudder is quite small but I resisted the temptation to increase its size. (For the time being).

 The wings were glued together using Gorilla Glue  before 170gm fibre glass cloth was used as the bandage. Slots for  the U/C bearers were carefully cut and the blocks inserted and glued using Gorilla Glue.

The ailerons were cut out using a band saw with the wing jigged to make sure that the cuts were vertical. The middle piece was removed as this is where the hinge blocks will be fitted.

Sanded down ready for glassing

The wing retaining bolt platform is from the kit and comprises of a small length of TE stock and a plywood face. I have replaced the original 2 x M4 plastic bolts with a single M5 steel cap headed bolt

Min servos fitted into the wing and slightly recessed. This may cause some consternation, but the power output of these small servos is far higher than standard servos of the 1980's. 3kg/cm should be more than enough for a single aileron.

Once again, Gorilla Glue was used to assemble the ailerons, hinge blocks and wing. The ailerons and wing were capped with lite-ply  to keep a nice sharp edge.

Fitting the belly pan was the only real tricky part of the build. I eventually hand drew a symmetrical hour glass shaped waist  and carefully removed the excess on the bandsaw. I was either a very good judge or very lucky because very little additional fitting was required.

It took a couple of evenings to cover the model, A mix of film from different manufacturers was used - basically, what I had in stock.

I didn't bother with the outline canopy, I prefer its nakedness and raw elegance.

Underneath a different scheme was used - similar to that I used on the Concept. I hope this model lasts a bit longer.

The covering has also been sealed using SolarLac - it helps prevent fuel/oil ingress under the film and keeps it properly adhered. This is quite important around the Glass Fibre to film junctions. In my experience, film does adhere particularly well to Glass Fibre or resin.

AUW - Dry 2.35kg. About 200g less than suggested in the manufacturers instruction leaflet.

Additional parts I had to supply:

1. 3 x Wheels (2.25")
2. 10oz SLEC square fuel tank (Yellow)
3. 10x8 prop. I would normally fit an 11" prop but there isn't much ground clearance. Hopefully the 8" pitch will keep the revs (and noise) down.
4. Snakes' clevises, saddle clamps etc,
5. Servos - Futaba S148 for Ruder and Elevator and E-max E5363 for the ailerons
6. FrSky X6R Receiver with telemetry

Looking forward to seeing this fly.