Westland Whirlwind wing question.

[gingerbob]

11 hours ago, Graham Boak said:

Whirlwind enthusiasts should look across to the Flypast site.  In its Historic Forum they will find a discussion (perhaps a page or three down now) concerning the disappointing failure of production Whirlwinds to match the performance of the prototype above 20,000ft.  The main participant suggests the fault lay not in the aircraft's aerodynamics but in the propeller blades, and the contemporary understanding of compressibility effects.

 

For convenience (other than time spent reading more threads!):

https://forum.keypublishing.com/showthread.php?138012-Prop-Blades-Too-Thick-And-Peregrine-Blameless-On-Whirlwind&highlight=Whirlwind

 

and

 

https://forum.keypublishing.com/showthread.php?141907-More-proof-that-it-wasn-t-the-Whirlwind-s-engines-and-a-question&highlight=Whirlwind

 

(note: I haven't refreshed my memory, but they are here in chronological order.  I do remember some food for thought, at the very least.)

[Graham Boak]

Jerry:  In those days project offices could make all sorts of claims based on back-of-the envelope estimates, and I've no doubt they could (eventually) have produced something recognisably relating to the Whirlwind, but once reality bites and the detailed engineering comes into play, then early project estimates go out of the window.  As do timescales, particularly bearing in mind the low priority.  Given the delays in producing the Whirlwind itself, and the Welkin, how long would it have taken to produce a genuine Merlin-engined airframe, - what good would a Merlin XX engined fighter have been in 1943?  You want to consider a respectable fully thought through design then consider a Welkin without the high-altitude wing or pressurised cabin.  As for the arguments about RR's power egg, they were excellent for servicing, but offered lower performance than a dedicated design.  Witness the attempt to install them on the Mosquito.  They also meant more work/money for RR and less for the airframe manufacturer.  I don't see Petter or the Westland Board approving, though of course pressure could have been applied.

 

There are of course always design compromises between the ideal and what actually gets done.  They could have kept the centre-section and gone to low-diameter 4-blade props.  Extending the rear fuselage is no big deal.  Given the loss in performance from low-diameter props and the power eggs, I'm not convinced that the resulting design would have been any faster, flown any further, or carried any more, than the basic design.  That's not allowing for restressing and strengthening the fuselage for the more powerful engine and greater weight.  You would have got rid of the limited production Peregrines and perhaps got the aircraft above 20,000ft, but the RAF would still be better off with Mosquitoes.

 

Such a design could be refined by dedicated cowlings and retaining (but enlarging) the current cooling system.  You'd have got a little speed but less range.  By this time you'd be considering Merlin 45s rather than the longer but less impressive XXs.  (Given that the Merlin 45s never even got into production Hurricanes, what are the chances of Westland getting any?)  Drop tanks under wing rather than bombs.  But you'd still be better off with a wider centre-section for more fuel and central store carriage.  It would also allow you the larger cooling area, and bigger flaps to regain take-off distances.  Then you could put the bigger props on and work on that undercarriage - but what year are we at?  And just what operational need does the aircraft answer that has not already been met by cheaper types?

 

My point basically is that you can't just drop a bigger engine into what was already a notably (impressively) small aircraft without affecting a wide range of features.  Ah well, maybe there's some ideas there for What If modellers.  Even my fingers are twitching a bit. 

 

The two photos in post 25 illustrate interesting details.   Below the wing they look like raised pressings, judging from the light, but on the top they look more like strips laid on top.  However, I hadn't noticed the way the fuel tank sits proud of the wing, at least at the trailing edge.  Was this also true before the strengthening mods?

[JasonC]

2 hours ago, Graham Boak said:

 They could have kept the centre-section and gone to low-diameter 4-blade props.  Extending the rear fuselage is no big deal.  Given the loss in performance from low-diameter props ...

 

Another way of looking at it is that the Spitfire and other single-engine aircraft took exactly this approach. More power + limited ground clearance = more blades. It certainly seems to have given that airframe enough benefit to be worthwhile.

 

Not saying there weren't other factors at play with such an installation, but I don't think that adding more blades at a fixed airscrew diameter is as bad a solution as you imply.

 

regards,

Jason

[72modeler]

6 hours ago, Jamie @ Sovereign Hobbies said:

 

A tank this size I would honestly expect to be baffled with a normal set of ribs complete with mouseholes just as a wet wing would be designed.

 

Good photos, Jamie! I would think, for Bedepee's  purposes, if the one he's modeling had the stiffeners on the wings, that decal stock, automotive pinstriping tape cut to the desired shape, or masking tape applied to the model and then sprayed with primer to seal the edges, would look the part. I have used this technique many times and it looks very realistic; it works even better to simulate the rib tapes on control surfaces on the larger scale models. BTW, a prosperous New Year to you and all the Sovereign Hobbies crew!

Mike

[gingerbob]

Re Merlin power eggs,

Move the tail down and the cockpit forward and maybe it would look something like this:

 

 

Sorry, just having a bit of fun.

[Graham Boak]

1 hour ago, JasonC said:

 

Another way of looking at it is that the Spitfire and other single-engine aircraft took exactly this approach. More power + limited ground clearance = more blades. It certainly seems to have given that airframe enough benefit to be worthwhile.

 

Not saying there weren't other factors at play with such an installation, but I don't think that adding more blades at a fixed airscrew diameter is as bad a solution as you imply.

 

regards,

Jason

I don't think that adding more blades on a fixed diameter when you need to absorb more power is a bad solution, as indeed the Spitfire showed, although theoretically the fewer blades the more efficient the prop due to lack of mutual interference.   However, the Whirlwind already had smaller diameter props than the Spitfire, so it would be better off with greater diameter.  

[72modeler]

5 hours ago, gingerbob said:

Re Merlin power eggs,

Move the tail down and the cockpit forward and maybe it would look something like this:

 

 

Sorry, just having a bit of fun.

You, sir, are a knave! However, the Fw-187 was a sweet-looking airplane!

Mike

[brewerjerry]

6 hours ago, gingerbob said:

Re Merlin power eggs,

Move the tail down and the cockpit forward and maybe it would look something like this:

 

 

Sorry, just having a bit of fun.

Hi

    Wish someone did a model of this single seater version/s

   i have the two seat version but doesnt look quite the same  

   cheers

     jerry

[FinnAndersen]

13 hours ago, gingerbob said:

Re Merlin power eggs,

Move the tail down and the cockpit forward and maybe it would look something like this:

 

 

Sorry, just having a bit of fun.

Why has no-one mentioned the DH Hornet?