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Author Topic: Westland Whirlwind (fighter).  (Read 5103 times)
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atesus
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« Reply #25 on: June 11, 2016, 02:41:13 PM »

I too love that flight with the meandering flight path, not to take anything away from the others. Very clever job with the nacelles, thank you for sharing!

--Ates
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Marco
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« Reply #26 on: June 11, 2016, 03:00:42 PM »

Stephen, if I could only have my simple models flying as well as your 'mockup'..... having so many 'tricks' (ailerons, nacelles, props) sorted out and working well together is a remarkable achievement. I am looking forward to seeing what the 'true' model will be !
Marco
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Don McLellan
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« Reply #27 on: June 11, 2016, 04:57:24 PM »

Great flights Stephen! 
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Prosper
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« Reply #28 on: June 12, 2016, 01:22:16 PM »

Well I don't know John and Pete - but I looked at the last video again and noticed that the dive commenced from quite high up. . .by which I'm hinting that if the mystery dive hadn't happened the flight ought to have been several seconds longer Cheesy. The thrustline was the same John. The rudder had been knocked on a previous flight and I hadn't quite got it back to where it was for left turns. I'm very pleased with the ailerons - they're crucial to the whole project really. They have to handle the surely considerable roll inertia of the combined nacelles/motors/prop units - can't remember how much each weighs, but it's a good old bit. Thanks Ates, Marco and Don. I'm going to enjoy the building, whenever it happens.

Stephen.
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cast_off_vortex
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« Reply #29 on: October 27, 2016, 04:57:53 AM »

Late to the party here, but I am most impressed with the lateral stability of your Whirlwind, given the scale appearance.  Cool I am guessing your pendulum actuates the up wing ailerons only, or are they linked? That must have been tough to sort out on this model unless you have done this on previous models.

Nice flights, thanks for the photos and good luck on your future scale build.
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Prosper
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« Reply #30 on: October 27, 2016, 02:00:21 PM »

Greetings cast_off_vortex, and thanks. I've had very little opportunity to fly this, but I've just uploaded its last video'd flight from way back in June - maybe just because the cloudscape is so summery Smiley. I have started on the scale version but I'm trying to push it along in parallel with several other builds - so it looks like instead of failing to finish several models in a row, I'll instead fail to finish several models concurrently Cheesy. The ailerons are linked; both go up/down and have differential movement (more up than down) - supposedly to help with adverse yaw but I'm not sure it's necessary. They were easy(ish) to sort out on this model but that's because I now have a clue, having made several pendulum models before.

The pic, to show that I really am attending to it, is of the scale tailplane - foam and balsa, to be covered in tissue. Simple idea but the number of operations required makes me think that a balsa/aliphatic sheet one would be as quick - and look better and weigh the same. . .

Stephen.
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OZPAF
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« Reply #31 on: October 27, 2016, 08:08:27 PM »

Good one Stephen. I'm waiting anxiously for reports on your other "concurrent" projects.
It did look nice up there and it handles the wind well.
John
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Sky9pilot
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« Reply #32 on: October 27, 2016, 11:16:00 PM »

Great looking model and the pictures of her up there in the air are fantastic!  I'd like you to give more info on you aileron setup sometime! Keep up the great work!
Tom
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« Reply #33 on: October 28, 2016, 05:36:30 AM »

The video flight was early July, not June. I knew I'd got something wrong - the weather all June was stinking.

Hi fellas. The things I'm trying to move along together are this, the 'scale finish' Martin Baker MB5, my unfinished Piper PA20 and Hawker Fury, plus a couple of new things. The PA20 in particular keeps looking up at me like a puppy dawg wanting to play. I won't mention the new stuff since I know by experience now that if I say "I'm definitely going to build a Quigley-Wilkes Skymonster Mk.IVc", I end up building a Bloggins Wombat instead. Perhaps I should use the modern politician's word "pledge", which would free me of all actual intent or responsibility?

Sky, I'll be posting on both the Whirlwind and MB5 as and when - I'll show the pendulum rig on one or both threads.

Stephen.
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3view
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« Reply #34 on: October 28, 2016, 01:03:29 PM »

The ailerons are linked; both go up/down and have differential movement (more up than down) - supposedly to help with adverse yaw but I'm not sure it's necessary.

Hello Stephen,

A balanced turn is the enemy of pendulum control and adverse yaw might be a good thing!

Steve
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Sky9pilot
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« Reply #35 on: October 28, 2016, 03:02:48 PM »

Great stuff Stephen...I look forward to following both builds in the near future!
Tom
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« Reply #36 on: October 28, 2016, 05:50:16 PM »

Thanks for the update Stephen. Hopefully you will have enough flyable weather before winter to sort out the tech problems on the experimental models and finish off the begging "Pup" Smiley

John
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Prosper
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« Reply #37 on: November 25, 2016, 02:34:25 PM »

I've made the first nacelle for this kite. In a last-minute reversal I decided to make it from cyano-coated balsa instead of aliphatic-coated. There's a hefty amount of double-curvature in the shape and I doubted slightly the pre-prepared balsa/aliphatic sheet's ability to take it. There's a cost in time and effort to prepare the balsa/ali sheets, and I hate to waste it! The cyano method involves shaping raw balsa sheet then adding the coating afterwards, so if the initial moulding process fails you're just rejecting a plain sheet of wood not the whole coated caboodle. I chose medium C-grain but this sheet was pretty stiff and brittle. I hope it doesn't explode into splinters when it hits the ground. . .

I can't finish it completely until the wing panels are ready too, but as seen it weighs 4.3g - It'll go over 4.5g when the final bits and bobs are added. However the nacelles on the mockup weighed 5.5g so I think I'll save some weight. I really need a lighter model than the mockup to get some good flights.

Quote from: OZPAF
. . .and finish off the begging "Pup" Smiley
Nope, still not finished - its only accomplishment to date is to serve as a size comparison for the Whrlwind nacelle Cheesy.

Now to make the other nacelle - I'll take pictures of each stage and post 'em.

Stephen.
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strat-o
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« Reply #38 on: November 25, 2016, 03:59:25 PM »

Since there is a risk of failure involved, would there be a way to make the ali/balsa the same way as the cyano/balsa?  Coating it afterwards?  (It's been a long while since I read about the ali/balsa process, so please excuse my ignorance)

Marlin
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OZPAF
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« Reply #39 on: November 25, 2016, 04:36:15 PM »

It's either a small pup or large nacelle or both Smiley I'll need to re read about both processes again as well. The double curvature is quite pronounced - impressive. It should be quite rigid.

John
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calgoddard
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« Reply #40 on: November 25, 2016, 05:38:58 PM »

Stephen -

Maybe this has already been covered as I have not read the entire thread in detail.

Have you thought of using a wobbly motor peg to solve the motor bunching problem?

As I recall, Tom Arnold is an expert at packing a ton of turns into a twin and I think he uses this technique.

Essentially one tubular motor peg with flared outer ends fits loosely around an inner motor peg that is rigidly locked to the fuselage, or to the walls of the nacelle in the case of a twin.

Maybe Tom can explain it, but some how, some way, the wobbly motor peg alleviates all sorts of mischief that would otherwise occur at the back end of the rubber motor during unwinding. It helps prevent motor bunching and the resultant shifting in CG.

I had a rubber motor lock up on my Jabberwock due to bunching, resulting in a violent jerk that pulled the LE of the stab out of its platform, onto the top of a stop.  The resulting positive stab incidence caused my model to nose into a steep dive, right into the ground.  By some miracle, there was no damage to the airplane as the soil had recently been tilled and was very soft. I think I will use a wobbly motor peg on that model the next time I fly it.  
    
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Prosper
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« Reply #41 on: November 26, 2016, 12:02:59 PM »

Hi Cal, I think a sliding sleeve on the motor peg can help prevent jamming at the back of a motor in a suitable fuselage but in this case the gap between the peg mounts is about 9mm and the width of the rubber looped around the peg is about 5mm so there's no room for any 'wobbling'. The mockup model used motors of about 3x the hook-to-peg distance. In more roomy situations more rubber (4x HtP or more) can be used but this nacelle shape tapers quickly at the back, hence the risk of jamming.

John, the nacelle is very rigid at the front, and that's not necessarily a good thing - flexible and resilient might be better because these nacelles are fully exposed and take all the landing shocks, also there's often a great deal of leverage exerted on them as the model swings around the ground contact. At least being a separate item it's replaceable.

Marlin that's a good question. I'm not saying coating a balsa shell with aliphatic is not possible, and I haven't tried it, but the two immediate problems to be overcome are first the tendency of ali to sit in globules on a surface, and second its un-sandability. On a flat balsa sheet I apply a dose of aliphatic + filler mixture then lay a plastic sheet on top and squeegee the mixture out across the balsa sheet. The result after two-three applications is a smooth sheet that needs no sanding except where there might be small localised blemishes. I find sanding large areas of this material near impossible - the rubbery aliphatic dust soon rolls into balls under the sanding block and these balls push grooves into the sheet's surface. Also the abrasive clogs very quickly and is likewise near impossible to unclog. CA can be smeared onto a pre-formed balsa shell very quickly - it dries immediately and being hard and brittle in nature sands very readily.

Stephen.
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« Reply #42 on: November 26, 2016, 12:18:17 PM »

A bit about the Westland Whirlwind, which was a mystery ship from the late '30s. The authorities kept it secret because they had high hopes for it, but apparently the cat had exited the bag anyway, at least as far as foreign powers were concerned. The Whirlwind was a 'state of the art' aircraft. I don't know if it actually pioneered one single thing, but the 1936 design brought together much that was new. I've counted:-
   Fully retractable tailwheel; mag alloy rear fuselage; flush rivetting; stressed-skin control surfaces; Fowler flaps; all-round vision canopy; leading-edge radiator intakes; thin wing; cannon armament concentrated on centreline; bullet fairings. . .well, bullet fairings are a 'fix' rather than a positive attribute - but many a/c since have needed them too!

When the design flew, it was faster than the Spitfire low down and was a genuinely capable fighter - not to be confused with the Messerschmitt 110 zerstorer type of concept that was quite fast but which couldn't fight its way out of trouble. The Whirlwind was a pretty small aeroplane for a twin: it looks odd in the one or two photos I've seen of it sitting next to other familiar aircraft. It had a span not much greater than a Hurricane's, and was more lean and slender. I suppose one could argue that it looks odd full stop, but I find it beautiful - spoilt perhaps by the thick, blunt tail. To model, I've chosen two Whirlwinds but between them I cannot decide. One is a 263 Sqn example, P6985 "HE-J" from 1940, and the other an earlier squadron evaluation machine P6967, which had an interesting and yet rather gloomy camo scheme - I didn't know the RAF used 'wraparound' camouflage until Buccaneers, Vulcans and what have you in the (?) 1980s.

The Whirlwind was only slowly developed after first flying in 1938, because the small Westland company was coping with Lysander-building, and because the new Peregrine engines needed development which Rolls Royce wasn't willing to undertake. There seem to have been various other reasons why the project didn't live up to early promise - political, personal, economical - the usual, really. Thus it missed its chance to shine - the Battle of Britain - and ever after was a misfit. The aeroplane was used for ground-attack because of the limitations of its 'orphan' Peregrine engines, and its heavy accurate firepower. Ground-attack being a (the?) most dangerous mode of air warfare, and yet grubbing work lacking the glamour of air combat, the Whirlwind never really achieved any glory.

Stephen.
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« Reply #43 on: November 26, 2016, 12:23:03 PM »

The first picture shows sanding 1/32 C-grain sheet to a nominal 0.4mm (1/64") thickness. outdoor working or dust-extraction is essential I think. The transistor is there so that I could listen to our brave lads give their wickets away tamely in the second Test Match - buffoons! Anyway, I chose considerably lighter balsa than I used on the other nacelle, to see how it stacks up in terms of ease of moulding more than in quest of a lighter result (tho' that would be nice). . .

Pic 2 shows the EPS mould which I already had from the mockup build, but reshaped somewhat from information more recently obtained. The thick markings on the mould are an ongoing attempt to find a way to transfer markings to the inside of the balsa shell. If this could be made to work it would make assembly of the nacelle or fuselage or whatever much simpler and quicker. A paper template is visible too. I lay paper on the mould and slowly manipulate it, cut it, re-fit it and so on until a useful template emerges (often after throwing away several previous iterations). This template is used to cut the balsa blanks (pic 3). The blanks are cut at the same time, one balsa sheet on top of the other, and the stress-relief holes are likewise twizzled out using a sharpened al. tube. A blank is then soaked for 10-15 minutes in water then propped up to drain somewhat before the binding. Pic 4 shows the binding half-way through (the whole process might take 20 min or so). It's normal to have to cut extra relief slits as binding progresses, each balsa sheet being slightly different in behaviour. I prefer binding with long strips of tissue but the egg-shape of this nacelle makes this impossible so I've used individual strips of paper. The binding is not straightforward: often firming down one area causes a bump or wrinkle to rise in another location so there's a bit of reworking and improvisation going on. I used also to like a neat job involving long strips of tissue and a bit of sticky tape; now I've let standards slip and use anything to get the thing done - sticky tape, cardboard strips, rubber bands - even pins, fer cryin' out loud. In this case there was one bad wrinkle I'm aware of - that must be smoothed out or cut out and patched later on.

The last pic is 'the Mummy', and with a fervent prayer to the great goddess Osiris this is placed reverently in a warm place to dry.

Stephen.
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Re: Westland Whirlwind (fighter).
Re: Westland Whirlwind (fighter).
Re: Westland Whirlwind (fighter).
Re: Westland Whirlwind (fighter).
Re: Westland Whirlwind (fighter).
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strat-o
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« Reply #44 on: November 26, 2016, 01:38:46 PM »

I think it's interesting how you make your slits for enabling the compound curvature, especially the drill-stop technique to prevent splitting along the grain further down the line.  That's something I've not seen in a model before (aside from your previous builds).
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« Reply #45 on: November 26, 2016, 04:28:04 PM »

Thanks for all that info Stephen. I'm surprised that the tissue has enough strength to wrap the balsa - however it is only 0.4mm. I guess cloth would possibly leave marks.

Fascinating as usual and thanks for the history of the Whirlwind - lots of writing there.

John
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« Reply #46 on: November 27, 2016, 03:18:57 AM »

... the new Peregrine engines needed development which Rolls Royce wasn't willing to undertake....
Developing the Merlin was a higher priority, and I believe the Whirlwind was too small for two Merlins.
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« Reply #47 on: November 27, 2016, 04:21:04 AM »

The Peregrine engines were a development of the Kestral and were clearly of a lower priority than the Merlin. Also Rolls were trying to sort out the very troublesome Vulture at this time so I gueas they had their hands very full. Also the prototype Whirlwind had the exhausts ducted internally initially and that was a source of delay before they were rerouted.
As you stated Stephen it was very advanced for its time and if the engines had been sorted it would have been very effective at low level against tip and run raids as the aerodynamics were capable of development. The design was under Teddy Petter of SE5, and Canberra fame. It is interesting that some designers understood the need for thin wings much earlier than others.
The moulding techniques are realy interesting being done cold and using low forces to hold the sheet in place. I hope the rest of the build progresses smoothly.
Ricky
 
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« Reply #48 on: November 27, 2016, 06:08:45 AM »

Watching with the usual interest and awe Stephen,

Those pictures of the Whirlwind are really reminiscent of the early jets don't you think?

Cheers

Andrew
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« Reply #49 on: November 27, 2016, 07:42:58 AM »

Stephen, that is an excellent low down on the Whirlwind. I have been interested in this aircraft since elementary school. The concentrated firepower of 4 x 20 mm cannon must have been nothing short of impressive. I don't know why it wasn't developed further as an interceptor. It had better range than either the Spitfire or Hurricane, impressive speed, and a powerful punch. Probably would have proven very effective intercepting the V-1.

I am guessing the competition from the Beaufighters and Mosquitoes, combined with Peregrine development ruled it out for further development/production. OTOH, you only need to train / sustain one operator for each Whirlwind, compared to two or more for the other aircraft. Training costs seldom seem accounted for, or were considered insignificant.

Kelly
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