Grumman AA1A ZS-VYI

Welcome to Flysouth - Grumman with Chevrolet V6 - Build Log.

An Online Journal (not a blog - this is hand made!)

Yeah, we know the old one about building (or rebuilding) your own aircraft - "whatever length of time you think it will take, just double it!"

How about changing that to quadruple it (and the final multiple is not yet established!) starting in February 1994, we are now up to just over 15 (gulp!) years, and still not done! To be fair though there have been periods of 2 years or more when I have not laid hands on the aircraft - mea culpa!

After selling off my previous Yankee ZS-VYI in August 1993 - an AA1A modified with 150 hp up front, with which I enjoyed some great flying over 16 years and about 1800 hours, the withdrawal pangs were setting in. After considering various replacement aircraft, but not seeing anything in any sensible price range (read "cheap") that I wanted to regularly fly, I came across the fuselage and tail feathers of a 1972 AA1B. This aircraft had, in the far distant past been ditched in a lake near Witbank. The story goes that the pilot and a buddy were doing a buzz job on another friend's boat, misjudged things and smacked into the water! After the occupants swam to shore, the plane was dragged out and dumped behind a hangar, where it lay for many years. Coincidentally, during my pilot training at FALA in 1975 - 76, I recall being told of this incident and of the wreck lying at Witbank airfield, east of Johannesburg.

Eventually that wreck, minus various and substantial components ended up at Irene near Pretoria, with Marthinus "Weef" De Beer, past partner of the local Grumman importer, VIP Aircraft, who had intended to rebuild it - however I guess he saw me coming, and decided to take the money instead!

Tubular mainspar serves as maintank

My purchase included the stripped down fuselage, a damaged port wing, no starboard wing at all, the empennage, and engine mount, some damaged main gear legs and several cardboard boxes of cables, pulleys and sundry semi-identifiable bits and pieces, rumoured to fit somewhere on the airframe! Towing this lot home on a borrowed trailer, It did occur to me that I had taken leave of my senses, but I consoled myself that the re-assembly should not be too difficult, after all I knew the AA1 well and believed I could quickly obtain most of the bits that might be missing - how long can it take to put together what Grumman-American once touted as "the simple airplane" in it's advertising? Ha, Ha!

Next step was, of course to begin locating the missing major components, such as the all important missing wing, gear legs, instruments and an engine.

From the start of the project it was my intention to produce a different AA1 - one which would nor be powered by a Lycosaurus up front, but by a relatively efficient and powerful automotive engine. Now there's nothing wrong with a Lycosaurus if you really like rough running motors with a stunning 150 hp from a mere 5.7 litres! The other thing you have to favour is spares prices that are astronomical - one thing that always worried me about flying Lycosaurus's was the thought that every spin of the motor brings you closer to the day when you will have to mortgage your house to afford a major overhaul - and perish the thought that something like a camshaft may fail - at something like R14 000 ($1400) (excluding lifters and new cam bearings etc.) you just don't wanna know!

Seen at Cable, Wisonsin 1989

Having visited EAA's big gathering at Oshkosh many times, and taken steps to meet and talk with any owner flying an auto-conversion, I felt that I by now had a pretty good handle on what could work in the Grumman - and as time passed, and I talked to more owners flying behind auto engines, it became clear that the Chevrolet 262 CID V6 motor had potential. This motor was in use in a number of RV6 aircraft and others - and successfully it seemed. Studying the RV6, it seemed to me that here was an aircraft that was, in terms of it's configuration, size, weights etc., as close as one could find to the AA1B - if the motor could succeed in that aircraft it could surely succeed in mine!

AA1 Dorsal Fin

What about the extra weight of a V6 when compared to the Lycoming 0-320? Well, when I converted my previous AA1A from Lycoming 0-235 to 0-320, I added a total of 65 lbs. to the front end in doing so (a substantial part of which was in the bigger and heavier prop).

CG calcs at that time told me to add 16 lbs to the tail at station 200.4 ins, right under the vertical fin, to balance out the bigger motor. This seemed like a no-no to me, and instead I filled something like 20 small bags with sand - each weighed 4 lbs if my memory serves. On the first flight after the conversion work was finished, I placed these bags at the rear of the baggage compartment, to simulate the 16 lbs. of ballast in the tail. After each circuit of the airport, I landed, slid back the canopy and tossed out a couple of bags at the side of the taxiway, and off I went again. Well by the time I had ditched all the ballast, a bit at a time, the aircraft was handling better than ever and I figured that 16 lbs in the tail would not be needed. The subsequent 7 years and 800 hours of flying proved me right and I discovered that the AA1 flies better in all flight regimes with a bit of extra weight in the nose!

4.3 ltr Chev V6

With this knowledge I was not concerned with the thought of the extra weight of a big 'ol cast iron lump up front - with 190 hp it will certainly fly, and we can always move the battery aft, if necessary. Of course things like a composite prop (11 lbs against a Sensenich at 42 lbs), lightweight (automotive) starter and alternator, will help strip a bit of weight off - and let's dump the soft furnishings in the cockpit, thus saving another 30 lbs.

So the choice of engine was made - and the next major modification was to plan to get some additional fuel capacity. In my previous Grumman I had a added an aux. tank in the baggage compartment, this tanks came from a Ford Escort Mk11, and fitted perfectly just behind the seat backs, strapped to the baggage floor panel, and feeding direct to the fuel line running from the fuel selector the the engine. It carried an additional 11 galls usable, and helped extend the range very usefully. However the idea of all that gas in close proximity in any accident was not a comforting thought. And the old axiom that you can never have enough fuel on board unless you're on fire definitely holds true in Africa, with avgas supplies diminishing as our smaller airports disappear!

Chev 262 Engine

This time around the gas had to be in the wings where it belongs, so 2 additional tubes were to be added to each wing to act as integral auxiliary tanks. These tubes would be located in the lightening holes on the wing ribs, which Grumman thoughtfully provided for the purpose it seems! This mod doubles the existing fuel capacity of the littlest Grumman, while putting the fuel where it can do little or no harm in the event of an accident.

Finally, in 1989 I had flown the RV6 with Dick Van Grunsven at Fond du Lac, Wisconsin. This aircraft was powered by an 0-320 of 160hp with a CS prop, and the performance of the aircraft was fantastic! This got me to thinking, why can't the AA1 perform as well? It's a little heavier, empty, but has almost identical dimensions. However when you look at the RV you notice the superb aerodynamics, which are worth a lot in terms of performance.

Some of the aerodynamic features cannot easily, or at all be replicated on the AA1, such as the lower and more streamlined canopy - but others can, such as the smaller flat-plate frontal area, smoothing airflow around the tail feathers, gear and wheels/brakes with sleek fillets and fairings etc. Plus of course cooling drag, one of the big speed killers! With a properly engineered water-cooled motor installation, this drag factor can be effectively reduced to the minimum.

Chev 262 Engine

To summarise my objectives for the AA1B here goes:

  • 1. Reliable auto engine power of at least 180 hp
  • 2. Additional fuel for extended range and endurance
  • 3. Improved aerodynamics and reduced cooling drag.

Sounds pretty simple, right! Oh, one thing I forgot - build the AA1 for less than R120 000 ($12 000)!


Having started with something less than a flyable aircraft, there was a lot of work on the airframe before we could even approach the exciting bit of sorting out an auto-engine power unit.

After thoroughly cleaning everything, including chemically cleaning the entire fuselage interior and checking thoroughly for any corrosion (none present, I am happy to say) and examining the famous glue joints which hold everything together on the AA1, we began in 1994 to start assembling.

Made these wingtips of fibreglass

The first task was to get the fus. standing on it's own three feet - so I ordered from Ken Blackman of AeroMods in Washington State, USA, a set of used main gear legs. Ken also supplied me a used engine instrument cluster. Also ordered a new nose leg, and once these had been collected by a friend, Trevor Trautmann who himself was touring the US hunting for parts for his own AA1B rebuild, we could get the kite standing.

Locally I sourced a set of Cleveland brakes and wheels, reputed to come from a Cessna 182 - looked identical to the Grumman stuff, except for larger bore caliper pistons - maybe we have better brakes now?

Once all this was installed it was time to strip the old wings, as the Alclad covering was beyond repair - having been battered in storage over the years. Since the wing skins are glued with epoxy adhesive to the ribs, it seemed that this job should be easy - just slip a scraper blade into the glue joint and pop the skin off - right?

WRONG! - I could not believe how the glue had, after 20 years of curing, set like steel - in fact my first attempts, before we got the smarts, resulted in tapping the scraper bade through the wing skin - in other words it was easier to cut the Alclad than to cut the glue!

Chev 262 V6 and Belt Drive on Cessna 172

Obviously this was not going to work, and the risk existed that I would end up hacking cuts through the wing ribs - not good. After a little thought I realised that judicious application of a heat gun should soften the glue enough to make it easy to get the scraper blade into the bond-line. The concern here was that the ribs are not only bonded to the skins, but also to the main spar, so it would be important that our heat gun method should not result in any damage to the adhesive holding the rib to the spar.

After some cautious experimentation we managed to get the skins separated from the ribs - although, even with application of heat, that epoxy did not easily give up! And after the wings were denuded of covering there was a big job left to remove the last traces of epoxy clinging to the rib-flange. This we did the hard way with sandpaper, figuring that we didn't want to put any more heat into the structure, particularly near the centre hole of the rib, where the spar was bonded.

Now of course we had to find some new covering - what a shock, local prices for .020 or .025 Alclad are fierce, so we left this in abeyance for now and carried on with other things.

The things included installing all controls, pulleys and cables, carrying out some minor repairs to the firewall area, installing all the tail feathers, the canopy and windshield and the instrument panel and a set of the basic VFR instruments. With the help of Trevor, the airplane, less the wings, was also painted.

After this the project languished for a long time - about 2 years, although during that period I located the engine I intended to use. This is a Chevrolet (GM) 262 CID V6 as used in the Chev Blazer and some other US models. The engine was purchased from American Parts Warehouse in Marshal Street, Johannesburg, "as is" - take a look at the pic and you'll see what I mean! After stripping, the block, heads, rods and crank were sent off to the machine shop for boring grinding, revalving and checking for straightness in the case of the rods.

Click to enlarge

In 1998, I was due to travel to Oshkosh and figured that I might pick up some suitable sheets of Alclad there. What an eye opener when I obtained 2 x 10 ft sheets of .025 and 2 x 8 ft sheets of .025 for one quarter of the price in South Africa - and managed to get it all rolled and boxed up for $10, and took it along as hand-luggage on the Lufthansa flight home! These wing-skins are slightly thicker than the original, which were .020 in alclad.

This purchase allowed me to proceed with installing new wing skins, but first to install the aux. tanks. These had previously been welded up using farmer's irrigation tube from local manufacturer Hulett aluminium. With a 101.6mm dia. and 0.9mm wall thickness, these welded seam aluminium tubes are identical to those offered in an AeroMods STC for the little Grumman, which adds either 10 (one additional tube per wing) or 20 gallons (two additional tubes per wing) of additional fuel in the wings. The tubes are slid through the existing wing-rib lightening holes, fore and aft of the tubular wing-spar, which also serves as the main tank. The great advantage of this arrangement over an auxiliary baggage tank is that there is no fuel travelling with you in the cockpit and the additional weight of fuel is so close to the existing CG that whether your tanks are full or empty the balance of the aircraft is maintained.

Each tank in my set up ( there are four, two in each wing) has it's own baffles welded in to avoid fuel surging along the tank during sharp manoeuvres and carries 5 galls - giving a total of 20 galls additional gas - that doubles the standard capacity. In each wing the two tanks are linked to be common and fuel is pumped from the auxiliary tank set, using a single wing-root mounted Facet electronic fuel pump on each side, to the main tank. In flight one would need to empty the main on that side by at least half before beginning to pump auxiliary fuel - but we now have "in-flight refuelling" - and can get a "fill-up" anytime - handy! Total weight of the tanks, piping and pumps - 16 lbs, seems worth it.

Click to enlarge

Once the tanks had been installed, it was time to tackle the skinning of the wings - where to start? Best place, thought I was to consult the experts and get a price for them to do the job! Shock, horror, the prices I was quoted seemed to take no account of the fact that I was to supply the materials, other than rivets! Crazy money, telephone numbers again - no go! Just going to have to go the DIY route yet again.

Started by making the mistake of trying to tackle the job single-handed. Not the way to go with 10 ft long and 4 ft wide sheets of thin and very easily damaged Alclad. Also made the error of using solid rivets, when the Grumman wing was never designed with these in mind, with the result that it is really tough to get a bucking bar in to some areas, even impossible in some instances.

Setting the job aside and giving some consideration to these newly identified difficulties led me to changing over to blind rivets and getting another pair of hands in to help. The rivets are the Avex type (locally available), and metallurgically exhibit similar strength to the solids, but are so much simpler to place. Once we had rearranged things along these lines, we were ready to proceed once more, and with assistance the job came together well. I also used epoxy adhesive on the rib flanges, where the sheets would contact the wing structure, but I wasn't prepared to rely totally on the adhesive method, thus the rivets. When Grumman made wings, they had all the jigs, cradles and clamps to hold the skins on nicely, while everything cured under heat in a big oven, which is how they achieved excellent results - doing the same job in the less than perfect conditions of my garage at home was not going to give the same result, to my way of thinking, therefore the "belt and braces" approach.

Grumman ready to roll

One of the biggest parts of the riveting job on the wings was the dimpling of each hole, to allow for flush rivets - and this has to be done on the wing skin and the flange of the rib where the attachment is made - but well worth it I think, as after lightly milling each rivet to ensure a flush fit, then epoxy-filling each rivet-head as necessary, the wing looks like the original with not a rivet in sight! - and that's gotta be worth a little speed. Once completed the wings were painted to match the fuselage - fortunately I still had enough 2K paint from the previous painting job, which of course matched perfectly. After all this extended effort, and having moved the aircraft from my home, where it was taking up too much space, to Baragwanath Airport, SW of Johannesburg, we took a break - a long break of about 2 years again - we'll get to the recent triumphs and tragedies in the next instalment!

> Next - Part 2

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