Bob Palmer's radial cowl 'Thunderbird'

One man's small part in the continuing saga of an historic model.

By 'Tubby' Day

After a time interval of nearly fifty years it is very difficult to track down details relating to models or events. Memory is far from reliable and published information may be ill-informed or (perish the thought) biased, while vital information may have been considered unimportant at the time. What follows is my own collation of what I have been able to discover, coupled with what I have learned from examining and restoring a historic model. Conclusions drawn are my own.


In 1957 Bob Palmer visited the UK with Howard Bonner as part of a world tour to promote model flying. I'm not sure of the origins of this trip, since it seemed to consist of a tour of South Africa and a single visit to England. Bob Palmer demonstrated C/L flying with a Veco 'Thunderbird' and Howard Bonner demonstrated R/C flying with his 'Smog Hog'. The trip to England featured demonstrations at Woburn Abbey. Here we have a mystery because I would have moved heaven and earth to be there had I known about it and my club ran their usual coach trip to the event. It was well advertised in 'Aeromodeller' so I have no excuse, or explanation.

Palmer & T'Bird

Picture from 'Model Aircraft', July 1957

Accounts of what actually happened on that day vary from witness to witness. Everyone was impressed by what they saw. Published versions talked about slow speed aerobatics and two-speed motor runs. My attempts in later years to obtain more detail produced only one useful account from a creditable witness. This was from Pete Fisher (founder of Performance Kits). When he saw Bob running up the motor before the flight, he was amazed how slow it was running and he thought that Bob was demonstrating how slowly the motor would run. The flight then went ahead with the model being kited around through downwind manoeuvres with only about two actual straight and level laps being flown. Pete's conclusion was that Bob did this because of the very strong wind. It was also raining some of the time. The picture above would appear to confirm the conditions.

I have never been able to trace the actual reference, but I and others have a clear recollection of being informed that this was the prototype 'Thunderbird'. Note that this was 1957 and the kit dates from 1955 or earlier. See later.

Bob left the model in England (with Ron Moulton) when he returned to the US later that day. I have just one second-hand account from the man that drove him to the airport that there was a second model in the car, but I have been unable to confirm this. Later that year (October), there was an account of the tour in 'Model Airplane News'. This was accompanied by a cover picture that showed Bonner with a 'Smog Hog' and Palmer with a trike-geared version of the 'Thunderbird'. My impression is that this was all that Bob had available at the time. There is no evidence that this model was taken on the tour. All of the pictures of the radial cowl model were taken in England.

MAN cover
Trike T'Bird

Included in the article was a small three view of a standard Thunderbird (as the Veco kit, but without a cowl). Nowhere is there any mention of a radial cowled model. The article talks about 'new models' being built and tested for the tour. They spent 30 days in Africa and 5 days in England, with the demo flights at Woburn on the last day. The African part of the trip was arranged by Monte Malherbe.

3 view

Perhaps I'm labouring the point, but there is very little information on the model we are interested in, or its history. Outside of the British press reports of the flights in England, there is no mention of this model anywhere. GMA once told me that the model had been flown in one US Nats (probably 1955, although other information suggests that this was the trike-geared version).

What I read at the time (I didn't see the MAN article until many years later), and the pictures, had a strong influence on me. I produced several stunt models with radial cowlings. I also built one or more examples of most of Bob's designs. All of my own models used Bob's set-up of 5:3 elevator/flap ratio.

In August 1981, at the Aeromodeller Vintage Day at Old Warden, I was approached by Ron Moulton who informed me that he had the model in his car and would I be prepared to restore it! Trying not to appear too eager I immediately said yes. The model had been residing in Ron's loft for many years and the silk covering had pulled apart in several places along with splits along the edge of the colour trim. At some time, the tailplane had been broken and repaired by inserting a ply splint.

Those original accounts of the model all reported a weight of 36 ounces, so the first thing I did was to weigh it. I made it 43 ounces. The model did not have any noticeably amount of fuel soakage so I assume that this is the 'real' figure.

As received As received As received As received As received As received
Click on the picture for a larger image.

My next move was to take a set of photos of the model as it was. I then started removing areas of the silk covering to assess what needed to be done. At this stage it was clear that the original fabric hinges (with neat pinked edges) were badly rotted by fuel and would have to be replaced. The biggest surprise was the discovery that the wing had been repaired at some time. It was very clear that the model was as it had been left here in 1957 and there had certainly been no work done on it other than the repair to the tail. Several of the ribs had been crushed and simply cemented back into shape. The tips were also damaged. The original 1/16" sheet core of the tip had been cut away as much as possible during construction making them quite weak. They too had been broken and repaired with cement. The repair had been reinforced with pieces of 1/16" sheet which were roughly broken from a sheet and not trimmed at all.

The point here was that the covering was completely intact, apart from the ravages of time, and this work must have been done before the fuselage was assembled to the wing. There was much use of a dope and (pink) talc powder mix to fill in holes. Some of this was under the silk covering and some over it. My conclusion here was that the wing had been part of an earlier model and had been repaired and used to produce the radial cowled model. The wing was unquestionably from a kit with die-cut ribs which had circular holes punched for the secondary spars. So much for the 'prototype' story. Which ever way you look, this wing was on its second fuselage.

One humerous discovery was that the silk covering was stamped on the inside in several places with a rubber stamp. This said, "Property of the Japanese Government" IN ENGLISH! I have visions of someone selling local silk as Jap silk and making a stamp to 'prove' it.

Several problems presented themselves. The model had very strange and asymmetric control throws. The elevator movement was from 50 degrees 'up' to 80 degrees 'down' (I measured this several times) and the flap movement was from 50 degrees 'up' to 30 degrees 'down'. It seemed to me that this must be preserved in order to preserve the original character of the model. This was even more important if the model was to be flown and anything learned from it.

Elevator movement

Some idea of the down elevator movement can be seen
in this photo from Ron Moulton's 'Control Line Manual'.

I was concerned about possible paint compatibility problems. I assumed that the model had been painted with butyrate dope, which was generally unavailable in the UK at that time. I did some tests on parts of the model and covering and found that the application of nitrate dope caused bubbling and cracking. The large wing fillets became very soft.

Because of the numerous levels of silk covering, fillets and dope/talc mix I decided that it would be far too difficult to recover the fuselage as the model might not survive. I stripped the rest of the model and left the fuselage alone for the time being. I replaced the fabric hinges, literally one at a time to preserve the alignment. I didn't have access to pinked tape or pinking scissors so left the edges straight. I used part of an old terylene shirt.

The undercarriage was of aluminium bolted to the bottom of the fuselage. This had aready been repaired at least once, presumably by Ron. The mounting was reinforced by cleaning up and covering with nylon. The cowl was also of aluminium. The cowl itself was a very thin spun item and this was fitted to an aluminium backplate machined from solid with integral cooling outlets. Both the U/C and the cowl had 'engine-turned' finishes and were anodised a dark red. The spun part of the cowl had numerous stress cracks which had been reinforced by rivetting plates over the crack. This was very neatly done. There was a large dent in the bottom of the cowl which I assume was Ron's doing.

The motor was a unique item. It was a prototype 'series 100' Veco 35 with a sandcast case. It was fitted with a Champion glowplug, very tall and similar in appearance to a spark plug. Although this plug would glow quite brightly, I found later that it could not keep the motor running due to oxidation. The prop was a 10x6 Top-Flite.

Cowl Cowl
Click on the picture for a larger image.

The tank was not in too good a shape. The solder had gone a pasty grey colour. Two fixing straps held the tank to the bearers via woodscrews. I was totally unsuccessful in removing these screws so the tank was left alone apart from resoldering the fixing nut for the cowl retaining bolt.

While all of this was going on, Ron passed on to me a letter from a gentleman in Australia. He had produced a plan of the 'Thunderbird' from a Veco kit and wanted me to modify a copy of the plan to incorporate details of the model. This was not too easy as the outlines and other details were different to both the kit and the published three-views of the model. I received at least one hint of the man's impatience with the delay in replying. I eventually finished the work and returned the plan to him. I have heard not one word from him to this day. However, at least one non-UK source claims to have plans available based on 'measurements taken from the model left in England'. I did supply details to Alan Walker here in England who produced an excellent plan. Alan reports that he has had no enquiries from abroad!

I mist sprayed clear dope over the fuselage, hoping that it would act as a barrier and recovered the model with heavyweight tissue. This received several coats of well-plasticised clear nitrate dope and the model was sprayed white, including a very thin dry coat over the fuselage. This seemed to work without reaction and I was able to spray the red trim over the whole model and add the blue trim. This left the problem of the white trim on the fuselage. I first gave the whole model a coat of 'Aerocote' fuelproofer. When this was dry I did the white on the fuselage with Humbrol enamel. After reinstalling the motor, cowl and undercarriage it weighed 45 ounces.

At this point there was a problem in that both of the wingtips had warped. They were warped when I received the model, presumably due to years spent in a loft. The structure of the wing changes dramatically at the point where the flaps end and there is nothing to hold things straight here apart from the 1/16" sheet centre of the tips. I eventually cured this by the application of heat and twisting in the opposite direction.

During all this time there was a lot of interest in the model and I was repeatedly being asked about progress. At one point I sent a personal letter to Ron Prentice, who was then the control-line columnist of the SAM 35 newsletter 'SAM Speaks' telling of my adventures. Unknown to me, Ron sent a copy of the letter to Bob Palmer and then published Bob's comments in his other regular column in 'Aeromodeller' magazine. These refuted, or denied, virtually everything that I had said. I had no warning of the publication and no opportunity to comment.

The model was taken to the Old Warden vintage meeting in 1991 in a covered but unpainted state and was seen by a handful of people who clearly saw less than they had expected. I finally finished the model on the eve of the 1992 Old Warden meeting and the model was again taken along. Unfortunately, it was very wet and only a handful of people saw the model. Late in that year (12/10/92), I had a single flight with the model at the field of my local radio club. The flight was very short and nothing was learned.

In 1993 (20/6/93) the model was actually flown at the Bilston C/L meeting (two flights). The first surprise was the models extreme reluctance to take off from the fairly short mown grass. With the motor set at a four-stroke on the point of two-stroking, as usual, the power appeared marginal. Once airbourne it was fine but would only run for around 3 minutes. Investigation showed that one of the tank vents was blocked. No problem, simply stand the model on its nose and let the fuel vent from the venturi. This still gave a flight which was too short to fly a full schedule.

The model was taken to Old Warden in 1993 and was flown by several people (me, Alan Jupp, Ron Prentice and Tom Jolley). People kept coming out of the woodwork and imparting knowledge about the model to each other which I knew was rubbish. I had discovered at this point that the feed pipe in the tank terminated well in front of the tank rear and the tank could be filled completely by holding the model on its left side. Thus, Tom Jolley was able to fly out a full schedule with the model with Ron Moulton accompanying him in the circle. All told, the model had seven flights that day.

The model was flown using my standard handle which gave full use of the considerable elevator deflection. No-one found this gave any problems and the model turned equally in either direction.


By now, Bob had woken up to the fact that the model and, more importantly, the motor were still in existence. He told Ron Moulton that the motor was one of his favourite 29's and he wanted it back! I had measured the motor and knew it was a 35. Despite my protests, I was informed by Ron at the above meeting that we would have to remove the motor at the end of the day so that he could send it to Bob.

So, we had the remains of one day, during which we had already seen heavy rain, to fly the model and learn what we could. With both Mick Taylor and John Perry standing by for their turn, I set out on one more flight with the model now running properly for a full tank. Sad to say, when entering a wingover, I slipped on the wet ground and was unable to prevent the model from going straight overhead and into the ground.

That beautiful cowl was flattened and the wing covering was shattered. The undercarriage detached itself one more time. At least, there was no longer any justification for not returning the motor to Bob.

The story doesn't end there. George Aldrich told me that Bob Palmer returned the motor to him for refurbishing. Why I wonder? George was also told that the motor was a 29 and he also measured it and found that it was a 35. He then chromed the liner and set about honing it. He heard a regular clicking noise and examined it under a strong light. It had split from top to bottom! He then set about using a standard liner which he had in stock but found that it wouldn't fit the case. This was a prototype, remember? He then had to machine the case to fit the liner and finally returned a fully refurbished motor to Bob. In my view, a piece of history has been turned into just another motor.

Still not the end. The damaged model sat in my workshop and showed an astonishing degree of degredation. In a very short time the paintwork became badly crazed and began to break up. With Bob's return to health I am tempted to think of portraits and attics. I was constantly being asked by Ron Moulton whether I had made any progress on the repair. While I was doing the original restoration I was constantly being criticised by Ian Russell (now the manufacturer of Rustler-Merco engines) for 'not doing anything'. Who better, I thought, to take on the second restoration? Ron was very reluctant but, in a moment of weakness, agreed.

Imagine my surprise when I learned that Ian now has the 'original' motor from Bob Palmer. So, one day we may see a third generation model, fitted with a second generation motor. I am a very strong traditionalist, with a strong nostalgic streak, but I simply can't see this as anything other than a parody, however good a job Ian makes of it.

Given a choice, I would probably drive a stake through its heart!

Rereading the above, I can see that some people might get the impression that I am bitter, or at least cynical, about the whole situation. Not so. I feel that being asked to restore the model was a privilege and something that I would not have missed. It's a great pity that such an historic model (in the UK, anyway) was left to languish for so long and that things turned out so badly. It does seem, however, that the motor in the model is not the one that Bob Palmer thought it was and the whole mess could probably have been avoided. I do remember Ron telling me when he gave me the model that Bob had no regard for it at all.

So, my part of the saga consists of a ten year rebuild and a total of ten flights. I can console myself with the fact that I have taken far longer to build a model and that several have had shorter lives.

T'bird at Old Warden

Update (11 December 2003)

As a result of the above, I have received some interesting feedback.:

A long-time friend and associate of Bob Palmer, stateside, says that he does not believe that Bob would have asked for the motor back.

A fellow member of the West Bromwich club, back in 1957, emailed me to say that he was at Woburn and had always been mystified by the fact that, although he had seen Bob fly, he did not see a radial-cowled Thunderbird.

In conversation with Bill Morley (founder of Merco Engines) just a few days ago he informed me that he had seen Bob fly at Woburn and that he had seen a standard 'pointed-nose' Thunderbird (no Veco kit style cowling) with projecting upright motor. Bill has since retracted this statement(?).

Update (7 September 2004)

Ron Moulton recently 'phoned Alex McDonald. Alex was a commercial traveller for H J Nicholls and drove Bob from Woburn to the airport to catch his 'plane back to the US. He confirms that there was a second model which was never taken out of the car.

It appears that there was some haste about catching a particular flight, because Bob's job at Lockheed was in peril if he didn't make it.