Reverse Engineering the Bugatti100
The following is a summary of my Reverse engineering approach to the model of the Bugatti 100.
Airframe and engine configurations
It would seem that, in the mid1930s, Ettore Bugatti and Louis de Monge decided to build a race plane to compete for the Coupe Deutsch de Meurthe trophy. The engine powers of competing aircraft obviously encouraged Bugatti who had auto engines which compared well power wise but were much smaller and lighter.
Morlock and others (http://morlock68.pagesperso-orange.fr/bugatti.htm) discuss the confusion of nomenclature. These investigations suggest:
It is quite possible that a race specification 4.7L T50B i engine in a lightweight aircraft could have been considered competitive in the mid 1930s. However, with the delays and development of competitors, more power would be needed, hence two T50B iii (3L) engines for the 1939 Coupe Deutsch contest.
Anecdotally, it has been suggested that the Bugatti concern was experiencing some financial difficulties and, since the Coupe Deutsch entry was self financed, the progress would have been slow and only progressing when there was no paying work. However, in August 1938, this situation changed. In effect, he was financed for an attempt on the World Speed Record, using unlimited engines.
The Bugatti was entered in the 1939 CD, with the number 7 allocated; therefore, at this stage (August/ September 1939) the intent must have been still to fit T50Biii engines, which were reported as being under test at Molsheim.
From the design point of view, this could be significant. The work in 1937 to 1938 would have been on the concept configuration developed specifically for the Coupe Deutsch. However, after the August 1938 contract, it would be logical to change the baseline such that the large engined ultra high speed version became the basis configuration and then to adopt derivatives to satisfy the Coupe Deutsch and long distance records. In this way by September 1938, at the latest, the original Coupe Deutsch concept had ceased to exist. That is the CD version would be the WR version with smaller engines plus long range fuel tanks. The difference is subtle, but it is easier to design for the extreme role and then remove items.
I suggest that this was Bugatti's logic and the new baseline concept became the 101p. Thus, there would be a need for several fuel capacity and engine set ups to satisfy the following competitions:
It is conjectured that since much work would have been done on the initial design, the additional engine increased both weight and space requirements, necessitating an increase in length and the centre of gravity moving forward. This latter would have had the consequence of needing the centre of lift (hence the wing) to also move a similar amount.
The image, a tracing, shows a preliminary construction which could be the original with a stretch between the cockpit and wing spar in order to accommodate the additional engine. (traces of the wing fairing can be seen in front of the cockpit bulkhead).
Almost all available information cab be found in some form or other on the internet.
These include photographs of the prototype, and the replica; several arrangement drawings and a 3D model, which seems to be the basis of CAD drawings. The majority of this data is undated and of unknown provenance.
Much of the available information has luckily been published in book form (J Horst; The Bugatti 100P record plane; Violaero.). This is an excellent collective source but again some caution is required in order to validate interpretations.
I had also been provided, by Scotty Wilson, with a set of fuselage drawings. He later provided drawings of the intake ducts in the empennage and fin.
Le Reve Bleu team have built a replica which has involved a tremendous amount of design work but this must be assumed to be an interpretation. (Note the use of the term reinterpretation is not intended as inferring that the best intentions were not involved.)