Did invention of flaps kill Schneider Trophy races?

[RJM]

What an interesting forum. For a start, I'm not a pilot, so please excuse any obtuseness on my part. This is also my first post, so I hope I haven't broken any protocol by posting in this section as a non-flyer.

When I was at school, I asked the physics teacher why the absolute speed record in the 1930's was held by of all things a Schneider Trophy-winning float plane. What about the drag of the floats, I asked? Surely a land plane could have been made to go faster than the Schneider Trophy planes?

The physics teacher didn't know the answer.

I wondered for years, until I read that the problem was tyre technology - the tyres of the day could not handle the high landing speeds resulting from the low angle of attack required to reach the speeds achieved (the Schneider Trophy planes pre-dated flaps). Ergo, floats for water landings and damn the drag.

Then the invention of flaps, allowing a variable AoA and lower landing speeds meant that wheeled planes, free of the drag of floats, took over the absolute speed record.

Recently, I have been told that this tyres and flaps business is a crock of rubbish. That still doesn't explain why no-one put wheels on a Schneider Trophy winner, still without flaps, and went faster than the float version, albeit with a hot landing.

The tyre technology and flaps argument was a neat explanation, and I'm sorry to see it demolished - can anyone answer the original question - why did designers after the absolute speed record put up with the drag of floats?

RJM

[Kolibear]

The floats served at least three functions. Not only where they the landing gear, they were also the fuel tanks and coolant radiators.

Take away the floats and you have to increase the size of the wings to accomodate the fuel required. Then you have to add some sort of landing gear, either fixed or retractable. Fixed adds drag, but retractable adds weight with the associated plumbing etc. Also you'll need some sort of radiator which again, adds weight & drag.

So floats are probably a good compromise, added to the available of a runway of almost unlimited length.

[Checkboard]

Le Coupe d'Aviation Maritime Jacques Schneider (i.e. the Schneider trophy) was a race specifically designed for seaplanes, as they were seen as the only viable long range passenger option in the 1930's.

There wasn't really a comparable land plane race at the time - so the Schneider Trophy race planes improved to the point where they were setting the speed records - and they happened to use floats because the race rules required it.

So you see, it wasn't a case of "Let's go fast - hey we can use floats!" but more of a case of "We have to use floats on this plane, now how fast can we make it go?". Also floats aren't as draggy as you might assume, in flight they produce positive lift for not much more drag than an aerofoil section.

[Tinstaafl]

Another factor was the profound inefficiency of the fixed pitch propeller at low speeds ie take off. The prop had a massive pitch to suit the high speed flight of the race. That high pitch meant the prop was not very effective at producing thrust at low speed, leading to poor acceleration which, in turn, caused a very long distance needed to take off. Unlike now, there didn't exist 3, 4,5 or even 6 km long runways - except ready made ones on bodies of water.

[enicalyth]

G'day

The Schneider Trophy was only for seaplanes, yes, but wasn't it the case that it would be all over if the same racing outfit won three times in five years? The poms racked up three straight wins in a row ending in 1931. Game over. Winner keeps the cup. End of Schneider trophy then because them's the rules.

Also to make sure that the aircraft really was a seaplane with proper floats a stipulation was added after some skullduggery that the plane had to be moored for a certain period against a buoy and remain afloat without any assistance. [Obviously somebody designed some pretty skimpy floats!]

[RJM]

Thanks. ....well, that only took about 35 years. I wonder if that physics teacher has figured it out yet (or if he's ever thought about it again).

I work in much coarser engineering that aircraft design and construction, and it always amazes me what a complex of trade-offs a plane is.

[sedburgh]

But the Americans did get higher speeds from landplane versions of their Schneider Trophy racers, see the article on the Curtiss R3C on the Smithsonian web site at: www.nasm.si.edu/research/aero/aircraft/curtissr3c.htm
This airplane was the R3C-1/R3C-2 (the -1 is the landplane and the -2 the seaplane version). The R3C-1, piloted by Lt. Cyrus Bettis, won the Pulitzer Trophy Race on October 12, 1925, at a speed of 248.9 mph. On October 25, fitted with streamlined single-step wooden floats and redesignated the R3C-2, it was piloted to victory by Army Lt. James H. Jimmy Doolittle in the Schneider Cup Race held at Bay Shore Park, Baltimore. The average speed was 232.57 mph. On the day after the Schneider Race, Doolittle flew the R3C-2 over a straight course at a world record speed of 245.7 mph.