Tip stall avoidance question.

[Colin Leighfield]

I was fascinated by the XF5U and sad that it never flew. Photos of the V173 in flight seem to show a considerable negative angle of incidence on the "elevators" in level flight and that interests me.

The abandonment of the Rotodyne always seemed to be a tragedy, it looked so promising. However, it was incredibly noisy and as I understand it that was the nail in the coffin for the inter-city use that it was intended for.

Progressive wash-out in a flying wing rather than elevon reflex seems to be the optimum approach to me. I like wash-out in a properly designed wing, I think the benefits might go beyond just controlling tip stalling tendencies. When Supermarine used research from the National Physical Laboratory to produce the type 371 wing used on the Spiteful, Seafang and Attacker, they eliminated the 2.5 degrees of wash-out built into the Spitfire wing in the belief that it would reduce drag. They finished up with a plane that had a limiting Mach number about 10% lower and worse low speed handling characteristics, there is a lesson in there somewhere!

[Former Member]

[This posting has been removed]

[Piers Bowlan]

That is crazy Peter, never seen that before. I bet the glide ratio is impressive too, like all those 'disc wings' (not!).

It's a flying wing Colin, so I guess the V173 had to get it's longitudinal stability from somewhere?

With four rotor-tip ramjets The Rotordyne must have been unbelievably noisy but 'noise pollution' is a modern concept I believe. In 1956 it was British and wonderful! It was also very safe and it also took a long time for helicopters to attain a similar performance and load carrying ability, it was ahead of it's time and killed off by politics (Westland) Was it any other way?

 

 

Edited By Piers Bowlan on 21/02/2017 20:10:26

[Former Member]

[This posting has been removed]

[Simon Chaddock]

Piers

The Rotordyne did not have ram jets but tip rockets. High pressure air from the Elands was ducted down the rotor blades. At the tip it was mixed with fuel in a combustion chamber. The resultant supersonic gas stream had like all rockets a thunderous crackle (I actually heard it!) but unlike a rocket it did not get any less until the Rotodyne had moved well away or it had gone into 'auto gyro' mode.

Actually no worse than a military jet (it was certainly not the loudest thing at the Farnborough display!) but as the Rotodyne was always going to make most noise at taking off and landing it was never going to be 'city friendly'. .

[onetenor]

Back in the 50 s I built a novelty plane called Arabian Knight which was basically a rectangle with a motor stuck on the front a fin at the back and a built in reflex section from f wallront to rear with no dihedral. Wether I was lucky or it was in the design but it just would not stall. It would wallow and mush then just dip it's nose and pick up again.. It was meant to represent a magic carpet which it looked like it was flapping when it " STALLED " which as I said never really became one. It was an Aeromodeller plan which is still available from the zone or Traplet or similar. Not sure which but I have seen it on one of them.A lot of fun F/F but some have been R.C 'd Not sure which way it has been done though No real glide though LOL

[Former Member]

[This posting has been removed]

[Piers Bowlan]

The Nutball looks great fun David for little time expenditure or financial outlay. Amazing what a super low wing loading and high power/weight ratio can do. Very similar is this 'W' wing Capricorn flying boat that I found on uTube some time ago. You can download the simple plan somewhere on the net but I never got around to it.

I stand corrected Simon, indeed tip rockets on the Rotodyne were the source of the horrendous noise. Must have been awesome to see it at Farnborough but sadly I missed it as I wasn't born! The Rotordyne did a night take off from Battersea heliport - no one complained. I think they were made of sterner stuff in post war Britain back in the fifties. BEA cancelled their order as they said it wasn't big enough. This was at a time when the state of the art helicopters were the likes of the five seat Westland Dragonfly (built under licence from Sikorski) and Bristol Sycamore. The Rotordyne could carry thirty commandos, a potential game changer on any battlefield. Sadly the UK was broke after WW2.

You are not alone Colin in thinking that the benefits of progressive washout on a flying wing go beyond controlling tip stalling tendencies. All the Horten wings had significant washout which was not only necessary to provide longitudinal stability but directional stability as well, plus oppose adverse yaw in roll. A tall order but Reimer Horten was passionate in believing that 'a wing was enough' and should be built without vertical surfaces (fins or rudders).