Exhausting work

It was satisfying to get the new Rotax 582 out of its box and sitting on the Shadow’s engine frame at last. 

But it was only there temporarily, as I took it off and put it on repeatedly while I did a series of jobs before it can be installed properly.

A small change in the 582 crankcase moulding necessitated grinding out two clearance scallops in the rear engine plate.

Next, I custom-made some exhaust mounts, taking care to have muffler tilted to the same angle as the rear bulkhead. The cylinder head mount neatly skirts around the spark plugs and features an access hole for the temperature sender. Stainless bands hold the muffler to its webbed mounting plate. Two LORD rubber mounts will help absorb vibration.  

Lastly, I wanted to align the pull-start cover and re-route the starter cord, so it didn’t rub on the rear hanger tubes. I added a ‘turning’ block to achieve this. 

Now it’s off to Leitch Motorsport, so Barry can weld on the 12 loops which take the 6 springs holding the manifold and elbow ball-joints together.

Sandwich anyone?

Sandwich construction allows microlight aircraft to have lightweight, stiff panels. But when they are damaged, the repair requires lots of patience and a light touch.

This tailplane (Horizontal Tail Unit) from a light sport aircraft had impact damage which required repair of the outer skin and foam core. In one place, the inner skin needed repair. All without being able to get inside the structure.

The tailplane was assessed externally, searching for any signs of deformity, delamination, etc. A borescope proved handy for a reassuring internal check. After carefully sanding the paint off the suspect areas, I could now see the structural damage. Mostly it was cracks in the outer skin, but in a few places the rigid foam core was dented or punctured. 

The damaged foam core was delicately removed without cutting the inner skin. Sculptured pieces of specialised 3mm PVC foam were bonded in. Each damaged area was then skinned with lightweight fibreglass to recreate the original sandwich construction. Last job was to carefully fair the repairs using ultra-lightweight filler. 

Very satisfying to get this tailplane back to rights. 

Canopy windows

new canopy windows for 1989 Shadow ZK-KLHOver the past few weeks, I’ve been able to return to re-building my 1989 CFM Shadow ZK-KLH.

The next task was to make new canopy windows. Unfortunately, I couldn’t source tinted 1.5mm polycarbonate in New Zealand, so had to settle for clear windows. The old windows made good patterns, not only giving me the correct outline shape, but also allowing me to pre-drill the rivet holes.

rear canopy window with twin latches on Shadow ZK-KLHEach rear window had a single central latch which resulted in bent lower tubes, so I opted to replace these with twin latches to securely hold the window closed. I machined new latch axles from solid alloy and filed two ‘flats’ to positively locate each inner lever (i.e. it no longer relies on friction to stop the inner lever from rotating out of alignment). Overall, these new latches are stronger and more secure, but only a few grams heavier.

machined axle of new rear canopy latch (Shadow ZK-KLH)

The rear windows also have a full-length lower tube (with a matching horizontal cut-out in the rear bulkhead), so that the lower rear corner of the window is not floppy. Where each latch is drilled, there is an alloy sleeve to strengthen the tube and reduce the tendency for the axle hole to wear.

PS: You can see the small side windows that were added to the canopy shroud. They will give the rear passenger a better forward view.

Re-build carbon cowlings

The top and bottom cowlings of a Rans S6 microlight needed quite a bit of re-building after a prop blade parted company with the hub just on take-off.  For a brief moment, the engine thrashed on its mountings and did lots of damage. The area behind the spinner was smashed and the cowling mounting holes where torn.

I carefully grafted in new carbon and repaired the cracks, taking care not to increase the laminate thickness.  The cowling mounting holes were reinforced with alloy inserts.  Since a different type of engine was being fitted a few changes were made to oil inspection flap, exhaust pipe cutaway, etc.

Lightweight elevators

lightweight elevatorsThe Skyleader factory sent out a set of lightweight elevators for the GP One microlight. Made of carbon-fibre with a foam sandwich skin, they are torsionally-stiff and have a very smooth surface. The 6 hinge pins were very challenging to fit because of the narrow aperture along the hinge line. But with some ‘needle-nose plier’ ingenuity  and plenty of patience on my part, they went together nicely.

The new elevators, and last year’s vertical tail unit upgrade, mean that the GP One can avoid any possible flutter up to 195 knots (360 kmph). A lot faster than I’d want to go!

Carbon-fibre radiator louvres

cooling intake 2 - grilleTo help reduce the coolant temperature of the Rotax 912 UL engine on the Skyleader GP One light sport aircraft, I fitted a series of carbon-fibre louvres.to the cowling air intake. They proved to be very effective at scooping air and directing it through the side-mounted radiator, reducing the temperature by over 20 degrees C.
They work a treat and look great.

Wings on and start the engine

GP One @ Southern Wings flight school 2015-11-08 1500pxBack in June, two staff from the Skyleader factory traveled to NZ and updated SkyFreedom Aviation’s GP One to the latest specs. This included making significant changes to the exhaust, radiator and cowling layout.

As they left to fly back to the Czech Republic, they asked me to look after the assembly, engine run and initial flight. After completing some unfinished tasks and adding some extra features such as storage compartments, a friend and I transported the GP One to the Invercargill Airport where we assembled the light sport aircraft in the Southern Wings hangar.

On a miserably wet afternoon, I tied the GP One down and did an engine run. The temps and pressures came up OK.

I had to wait a couple of days for the weather to improve before flying the GP One.

More info at:  Assemble aircraft and run engine

Luggage space for LSA

GP One cockpit 2015-11-08 1500pxThe Skyleader GP One which is SkyFreedom Aviation’s NZ demonstrator only had a single storage compartment, so that it was a challenge to pack and access all the items required for long cross-country trips. I have designed and manufactured a series of additional storage spaces to make the GP One more user-friendly.

First up was a lightweight carbon tray in the centre console. This is handy for mobile phone, pens, sunglasses, etc.  The headset sockets are also recessed into this tray, so that the plugs are less likely to be bumped.

The second addition is a 50 litre luggage locker below the existing locker. It fits bulkier items such as jackets, daypack, lifejackets, etc. I used the hi-tech epoxy resin infusion process to manufacture it, which means that the new carbon/foam locker only weighs slightly more than the original fibreglass locker.

More info at: Luggage space

New exhaust, cowling and radiator for GP One

GP One radiator mount 2015-11-08 1500pxWhen the Skyleader factory staff returned to the Czech Republic in late June (after a very busy 10 day visit), there were a few unfinished tasks on SkyFreedom Aviation’s GP One demonstrator. Over the next few months, I worked steadily on completing these tasks.

Since the new exhaust has been re-located further aft, the under-slung radiator had to be shifted. It is now mounted vertically on the right side of the engine compartment, with ducting built into the lower cowling. It took some interesting welding and fabrication to align the radiator with the ducting and available mounting points.

More info and photos at: Exhaust and radiator changes

Pitching a Rans S6

Rans S-6 ZK-LDB (Rangiora)

I helped a Rans S-6 owner to adjust the propeller pitch on his microlight.  It was not going very fast in cruise mode, yet it would take off quite quickly. He figured something was not quite right.

He desperately wanted some more speed before he convoyed long distance to Rangiora with a Tecnam ‘Eaglet’ and my Skyleader ‘GP One’, both of which cruised easily at 100 knots.

We checked the blade pitch using a bubble protractor and found up to 1/2 degree difference between blades. Then we carefully adjusted it to have one degree more pitch. The result was pleasing – an increase of over 5 knots in cruise airspeed (now 85 knots at 5000rpm revs), but only a small decrease in take-off/climb performance.

Read about the trip http://www.skyfreedom.co.nz/news-blog/canterbury-foray