Zandvlei Trust

Another "bird has hatched" in Port Elizabeth.

Promoting the airplane homebuilding industry in South Africa.

Contact Gavin Lawson  if you are a homebuilder and require aircraft parts made or refurbished.

All photographs by Rego Burger. Read about his building a Cozy - Fish Eagle.


February 2010.

I am experimenting with a Q-tip on a prop. Many say the Q-tip does nothing but best test it myself. I am also adding carb cooling for the V8. In summer the hot air under the hood is too hot for the carbs, so a cool supply of air is a must.

photograph by Rego Burger

One of the tips has been bonded into place. Carefull balancing and shaping to match the tips has to take place. The weight calculation of each winglet (Q-tip) must be the same.

photograph by Rego Burger

The trimming and shaping still to be done.

photograph by Rego Burger

This view of the outside top cowling, shows one of the 2 new air ducts for cooling is being made.

photograph by Rego Burger

Inside of the cowling one can see the other duct and the directional scoops for the dashpots of the SU carbs. 

October 2010.

Well folks since I'm doing another stint of 40 hrs flying to appease my SACAA I thought it prudent to test something new instead of just flying circles.

So I purchased a MGL Extreme EFIS see image below, for less than the price of an old electric A/H.
I previously changed exhausts to 2 x 4 into1 homemade box to pipe units. Sound dropped by 2DB and the prop no longer gets soot on it.
I also installed 2 x EGT probes for fun.

photograph by Rego Burger

The new engine management system display.

I took an instructor with and we where shooting a few missed approaches at a remote grass field (wont land there unless the wind is 40kts on the nose) away from international traffic when on go around no. 3 the engine start to shake rattle and roll and I was glad i did not have false teeth.

The young intructor looked at me perplexed thinking the engine was coming off. I told him to fly the aeroplane while I quickly looked to see if the EMS could help me figure what the earthquake was about. 2 crew is a great help in managing these things.

Walla the EGT on the right side was ice cold only the left was producing combustion.
Quick analysis of the problem had me believe the right side carb was running rich. They are STD SU HIF carbs. To test my suspicion I briefed my #2 that I was going to apply the choke to see if it gets worse, we where still climing on 50% power, thank heavens. True the choke made it worse so that side was not lean.

I quickly explained to him the difference between SU carbs and std aircraft carbs.
In the explaination after gaining enough height, I told him to throttle back to half butterfly opening to reduce the inlet airflow to allow the needle piston in the carb to lower itself, and walla the heat came back. We then headed for home. Cowls off and my suspicion was confirmed, the damping oil in the dashpot on the right side had migrated out of it's place over 55hrs since I last checked them!

New routine - check carb damping oil more often, at least every 20hrs. Added the oil and fired it up, all perfect again.

Thanks to the EGT system and EMS for helping me diagnose ASAP and a cool insrtuctor who kept calm. It is all knowldge and experience gathering.

Mods in June - July 2010.

Made another 2 improvements;

  • The tensioner bolts on and off in less then 30min and makes tensioning the belt so much easier not requiring the removal of the lower cowling as before.

photograph by Rego Burger

Right hand side, prop hub on the left.

photograph by Rego Burger

Viewed from the centre of the shaft towards the engine.

The exhaust is my own design in rectangle tube to round conversion. Audibly it sounds like a symphony of pistons with the real V8 throb. No more crack through the propeller impact and no more soot on the propeller. The rectangle to round depressure chamber 1518cc each side seems to have lowered the noise a tad. I did not have my sound meter with me but the ear sense was much less stressful in the cockpit with head sets off and I could hear the radio speaker fitted in the back seat pretty well during run-up tests which was not easy before.

  • Performance; Now here is the funny part. Static rpm is up 200rpm from 3500rpm to 3700rpm on the same prop and the idle is up 200rpm which required me having to re adjust the idle stop to a lower rpm. 200 rpm is serious horse power.
  • Cost;  the entire exhaust system cost R550, the most expensive parts were the R350 for the lazer cut manifold flanges I welded the pipes onto.
  • Weight;  the pipes are 300grams heavier than the previous set, so I need to redo the mass and balance.

photograph by Rego Burger

Making up the exhaust stacks.

photograph by Rego Burger

Left hand side (from the rear looking forward) exhaust stack made. Just needs fitting.

photograph by Rego Burger

Left hand side (from the rear looking forward) exhaust stack in place.

photograph by Rego Burger

The right hand side done.

It is amazing what one discovers when you work out of the box, not all exhaust pipes need to be round, all of the time.

Why then the change?

Well firstly the exhuast port on the V8 is a rectangle 20 x 30mm, possibly the smallest exhaust port engine next to the mini engine. When I made the first pipe set, I had to beat the round pipe into a rectangle to fit, which I felt was a waste of time to please aesthetics. So I decided to stay with the existing shape. I made the interconnecting pipes as long as possible and all of the same length at 90mm into the expansion chamber. The expansion chamber allows the gasses to expand and cool in a split second. It then looks for an outlet which I have chosen to be 50mm round pipe, this is the part we see outside and should please most onlookers, but a 50mm square would have let out more are as the area of a square is larger than that of a round 50mm object thanks to pi.

I can't wait to test fly the extra 200rpm.

Test flying in May 2010.

photograph by Brett Routly

Since the rebuild the nose has been lengthened, colour added and wheel
spats installed.

photograph by Roger Thomas

In the original guise.

Take off.

At 13500 ft looking inland from the coast.

Glide back joining cct at 2650ft to the field in to PE from 36km out and at 13500ft.


I never had signs of a fuel leak during the first test flight phase
and thought my tanks where 100% sealed. So when I rebuilt
I opted to use polystyrene foam instead of urethane foam for the
transition faring shaping. 

A mistake, as the fuel disolved the foam and ran down the leading
edge of the wing and dripped into the cockpit when parked on the nose.

Fortunately pretty easy to fix without too much down time.


The aircraft's C of G being adjusted, lead balance weights
are being moved further back in small increments.


At 16075 ft.

Time to climb from 6000 ft - 16000 ft was 18min. I could maintain over
600 ft / min climb rate up to 14000 ft at half throttle, but then things started
fading and I had to apply full power.

The fuel consumption reduced hansomly to 22 l /hr indicating
that the SU carbs where doing their job well. It is nice to know
that the myth that car engines can't operate above 10000 ft has
been busted.
I have no need to fly that high and I am very happy at the 8000 ft
level for most trips but may push to 10000 ft from time to time.


Approaching the PE airport.

Back at the airfield.  All in all another great weekend of test flying.


Top of page  Back  Home