ZU-AMR, serial 001, was built in Secunda. A Taildragger Speedwing, it is powered by a Rotax 912, this aircraft was the demonstrator of our company, Kitplanes for Africa.

Left: ZU-AMR, serial 001 of Secunda, now has an updated fuselage.

The fuselage was damaged during a very rough field landing, and it was decided to replace the fuselage with an updated version, making it capable of tricycle configuration if so desired. ZU-ANI, serial 002, was built in Kimberley by Pieter Viljoen with a STOL wing. It is a Taildragger powered by a Rotax 532 of 64 Hp. The aircraft flew extremely well with this engine. It was later bought by Les Carlisle and moved to a nature reserve in Northern Zululand. The aircraft was used extensively on the reserve for fence patrols, species counts, anti-poaching operations and other uses. It was then sold to Jean Crous of Cape Town, who is busy refurbishing the aircraft. He is also developing a VW motor to replace the Rotax two-stroke. Some folks, it seems, like the sound of a four-stroke. We will feature more builder profiles in the next edition.

Fabric sealants and paints An Old formula updated in SA

The Bushbaby is covered with a locally manufactured polyester fabric, lightweight at 2.2 oz and performing well compared to imported materials. It is cheaper per running meter. The biggest decision for a builder was what paint system to use on his newly covered pride and joy. There are three options. There are the imported systems, of which poly-fibre is the best known, the locally pigmented butyrate system, and the automotive paint route.

In keeping with our policy of only using local materials, the poly-fibre and the Classic aero. system were obviously out. Although both are FAA approved and have been in use for many years, the costs are high and if colours are to be matched the sample first has to he sent to the USA. The automotive 2K system works well, but is inure prone to cracking over a period of time. Due to the flexing of the fabric, the norm is to add an elastic additive, but the problem is that the elastic leaches out with rime, leaving the paint brittle and causing flakes.
Owners, trying to get that extra glossy finish and applying too thick a coat of paint, further aggravate the problem of cracking paint. From experience we know that the thinner the coat, the less prone to cracking it is.
Technical advice by the automotive paint manufacturers regarding the amount of elastic additive, differ vastly from 15% to 50% being quoted. Too much, and the paint does not cure, staying tacky.
The pigmented butyrate system is proven over many years. It is slightly more labour intensive, but has many benefits, the main one being that there are many aircraft around that were covered fifteen to 25 years ago, still looking immaculate without cracks or flakes.
The other important factor is that the system is easily repairable. The butyrate can be sanded, or wiped down to the fabric, thus allowing repairs to be easily repainted.

Remember that for most Bushbaby builders, this is their first building project and first try at covering and painting. Butyrate allows most problems such as runs and pinholes to be easily corrected.
Automotive paint does not allow that and the builder has to live with his blemishes or recover and repaint the aircraft. The elastic in the paint makes it near impossible to sand, leaving pinholes and runs very hard to fix.
The imported nitrates and butyrates are freely available, but the problem comes in with the pigmenting, or colouring. The norm has been to take the butyrate to an automotive paint shop and let them colour the lot. They would double up the mixture, returning ten liters of coloured butyrate for five liters of butyrate.
I had a problem with the idea. It is pointless going for a highly flexible system and then adding a paint with 50% unknown additives in. The suppliers would not let us in on what they had added and we had no way of knowing if the flexibility or strength of the butyrate had been affected.
Also, we had no track record of the paints so we had no idea as to what the paints would do in the long term.

Enter the locally manufactured Kitplanes range of nitrates and butyrates. After years of searching we found a small chemical company that specialises in high performance coatings and adhesives. They were confident that they could manufacture high quality nitrate and butyrate to meet international standards set for aircraft use.
The US military specifications were used as the formulation guidelines, after examining and comparing the British defence and FAA specifications. The US mil spec was more stringent.
The results are a nitrate base coat dope that will exhibit less cracking with ageing than US
Military or British defence dope, that sacrificed a fraction of strength in favour of wider compatibility with colour pigments but is still mechanically superior to imported butyrates.
Take into account that the formula for dopes are more than fifty years old, and it is easy to see that by using modem chemicals and additives the original specs can be exceeded. Of course, the dope system is no longer in military use, with tin planes having replaced those beautiful tube and fabric constructions, and there was no need to update the original formulas.
As for the coloured butyrate, the local company mills the most colour-fast (UV resistant) pigment into the clear butyrate, ensuring that none of the elasticity or strength is lost.
Note that this system is not FAA approved and is only suitable for experimental aircraft. In the next issue we will have the whole painting procedure with photos.