All metal Mosquito ??
 

WI the Mosquito had been made out of aluminium instead of various types of wood? IIRC duraluminium is lighter/strong than wood, meaning an all-metal Mossi would have been even better, or am I overlooking something?

I do that an aluminium Mosquito wasn´t an option as there was not enough aluminium, so this is a purely theoretical question.

Re: All metal Mosquito ??
 

Theoretically, it would have been lighter. Practically, it would have depended upon the design team's experience with aluminium.

I don't think it was an actual shortage of the metal, though one would have been feared, but a willingness to use manufacturing sources outside of the already overstretched aircraft industry. You were better off using trained woodworkers than having to train new metal fitters.

Re: All metal Mosquito ??
 

Actually the average density of Balsa wood is 170 kg/m3 which is far less than Aluminium at 2700 kg/m3. Even when you take into account that Balsa is far weaker than Aluminium, The strength to weight ratio of Balsa is about 40% better. So an Aluminium Mosquito would have been heavier and slower.

Re: All metal Mosquito ??
 

No. Wooden aircraft are heavier than metal aircraft (and the main component of the Mosquito was not balsa but Spruce.) The main reason for this appears to be that the strength of the wood cannot be relied upon, so greater safety factors are required. Directly comparable cases are the wings of Soviet fighters, which changed from wooden spars to metal ones once the supplies of aluminium were sufficient. Attempts to create wooden versions of aircraft designed in metal end up heavier - see the Nakajima Ki.84 for an example.

One other advantage of metal is that it provides more internal space than the thick skins and internal structure of wooden aircraft.

Heavier aircraft are not necessarily slower, as weight has little effect on top speed. The wooden aircraft may be faster, because of a smoother external surface without steps and gaps between the panelling.

Re: All metal Mosquito ??
 

Sorry to disagree, but Mosquitos were not ordinary aircraft. They were the highest of high tech at the time. They were made from wood on purpose because it made them lighter. And they were pushing the limits on safety factors. Spruce was used where better bending strength was needed, the rest was Balsa and plywood. Spruce is also one of the lighter woods, 450 kg/m3. Its improved strength over Balsa retains the same 40% strength to weight advantage over Aluminium. These aircraft were built using the same principles as modern composite aircraft today. Assuming the same aerodynamics, weight is highly relevant to top speed and acceleration. The Mosquito could fly away from a Spitfire carrying the same payload as a B17.

Re: All metal Mosquito ??
 

You get a really good description of the construction of the Mosquito in:
De Havilland Mosquito: An Illistrated History By Ian Thirsk.

http://books.google.com/books?id=6nb...page&q&f=false

Page 39 onward.

Re: All metal Mosquito ??
 

Sorry, despite not being a structural engineer I will back my experience in the industry. Yes, the Mosquito was cutting-edge technology for the day. So were the Russian types. Metal construction is lighter than wooden. (Plywood is not a type of wood, but a treatment of it).

I was an aerodynamicist specialising in aircraft performance - weight is not "highly relevant" to top speed. Top speed is dominated by the zero-lift proportion of the total drag (mainly profile drag, skinfriction drag and excrescences), whereas weight only features in the lift-induced drag which is only 10-15% of the total at most - differences in weight therefore will be at most 5-10% of that, or 1-2% of total drag.

The Mosquito was not faster than the Spitfire, at least not comparing equivalent versions. Its normal payload was 2000lb of bombs. You are thinking of the overload payload of a single 4000lb - these aircraft were draggier and a ton heavier. The maximum payload of a B-17 was 8000lb.

Re: All metal Mosquito ??
 

A Mosquito carrying 2000 lb was at least 20 mph faster than a Spitfire. It was designed that way. Its defence against fighters was to fly away from them. I am a structural designer, among other things, and aluminium structures are not lighter than composite wood ones. That is why the Mosquito was made the way it was. The Hornet and the Vampire were of similar construction. I have a lot of experience with modern composites. Homogeneous metals do not even come close to competing with them. As I said, if the aerodynamics are the same, weight is important. They were doing everything they could to find an extra 5 mph. It is also a myth that the Mosquito was built of wood because a shortage or fear of shortage of aluminium. They had to go to Canada for the right woods. The Mosquito was structurally a much higher tech aircraft than any of the metal aircraft. It was so far out there that De Havilland had trouble selling it to RAF, until they started flying them, that is.

Re: All metal Mosquito ??
 

Not if we reference RAF performance trials. The maximum speeds in level flight were almost identical, going by test reports of Mosquito MP469 (408mph in January 1943) and Spitfire AB505 (409mph in April 1942). Both test aircraft had Merlin 61 engines.



I think he meant that you might have oversimplified the correlation between horsepower, weight, and aerodynamic efficiency.

In March 1944, RAF Mustang FZ107 was tested with a U.S. built Merlin 61 (Packard V-1650-3). The loaded weight of Spitfire AB505 was considerably less, but Mustang FZ107 was about 25mph faster at all throttle settings. I don't know if this Mustang had the standard underwing pylons installed, because that would have reduced top speed by at least 10 mph.

Re: All metal Mosquito ??
 

Better comparison would be against the prototype with 61s, as MP469 had a gun fairing slung underneath the fuselage.

AFDU report said the Mosquito IV was 4-5 mph faster than the Spitfire V, though the Spit was using emergency boost, the Mossie not.

Re: All metal Mosquito ??
 

I stand by my comments: given that metal replaced wood in all but a very small handful of designs, including ones originally designed in wood, the matter seems clear. Given that no-one will ever spend an equivalent amount of effort designing a metal version of the Mosquito, the point is probably unprovable.

It is not true that DH had trouble selling the Mosquito to the RAF: it was supported throughout its design, development and production phases. Do you seriously think an unapproved aircraft would have been allowed such a diversion of design effort and two precious Merlins? No doubt there were elements in the RAF that thought it the wrong choice, but the same comment can probably be made about every aircraft the service has ever had (including the Spitfire). The RAF, with the associated Ministries and Establishments, cannot be expected to speak with a single voice on such complex matters. Any manufacturer may understandably consider that (at certain times) it failed to get all the support it wanted - that's not the same as being unsupported at all.

A quick look gives me a max. speed for the Spitfire Mk.V of 374mph at 13.000ft. and the Mosquito B Mk.IV at 380mph at 17000ft. It is important to quote not just the top speed, but the altitude for which it is quoted. 6 mph is probably the penalty for the Spitfire's flat armoured windscreen as opposed to the Mosquito's V-screen, but is little more than the variation from one aircraft to another off the production lines. The Mk.V Spit had been in service a year before the Mosquito reached the squadrons, and the Mosquito was of course flying against the Fw190, which could reach over 400mph at similar altitudes.

Which might help to explain why the Mosquito day bomber loss rate was higher than that of the Blenheim it replaced, and why it was removed from service as an unarmed unescorted day bomber after use by only two squadrons. The pure bomber never did return - the fighter-bomber variant did, but served as a conventional light bomber under fighter escort, and only after the threat from the Luftwaffe had been considerably reduced.

The Mosquito was a wonderful design, with many fine features and a great service career. However, many of the stories are propaganda myths - particularly for the bombers - and a more measured judgement is needed. It couldn't "walk on water".

Re: All metal Mosquito ??
 

Follow up question.

Someone suggested making more Mosquitoes at the expense of heavy bombers. Someone else said this wasn´t possible as the Mosquito needed the work of expert carpenters and that all carpenters with the required skilles were already making Mosquitoes. True?

Re: All metal Mosquito ??
 

Markus, considering the number of women one sees in photos building Mossies, I wouldn't put much stock in that statement.

Re: All metal Mosquito ??
 

Markus
To quote loss rates is meaningless as the missions were very different. True the loss rates of the Mosquito were at times higher than the Blenhiem particually in the early days. However the missions were often beyond the wildest dreams of a Blenhiem squadron or any other squadron of any airforce. Amongst the early missions were the unescorted daylight raids over Berlin, unthinkable in any other aircraft.

There were also many examples of Mosquito's running away from German Fighters but also some where they were caught. At a guess with the Maximum speeds being close, the amount of fuel carried may well have had something to do with it, plus of course the tactical situation. If the Mosquito has any kind of a lead then its going to take a lot of catching.

Again its true to say that the Mosuito bombers normally operated with an escort but sometimes these had to be Mosquito fighters as nothing else had the range/speed combination. Its also true that the PR Mosquitos operated on their own with considerable success.

A final observation, Mosquito's with bulged bomb bays wold normally carry 6 x 500lb bombs on racks made by Handly Page.

Re: All metal Mosquito ??
 

Sounds right. I did a few searches in that online book and "skill" comes up once, "carpenter" and "unskilled" never.

Re: All metal Mosquito ??
 

I see your point, and of course there were minor discrepancies from plane to plane when modified in various ways.

Spitifire N3297 was apparently the first to get retrofitted with a Merlin 61, and my source says this aircraft reached 414mph at 27,200ft in January 1942. Guns and ammo were removed and replaced with ballast. I cannot tell from the photos if this prototype had the same kind of windscreen and underwing air scoops like those on Spitfire AB505. Some versions of the Spitfire IX had clipped wingtips and this would also account for a slight change in maximum speed.

Re: All metal Mosquito ??
 

Can't women become skilled carpenters then?

Re: All metal Mosquito ??
 

I'm sure that deep in the bowels of the British National Archives there lies at least one prewar economic study that compared the estimated number of skilled carpenters with the estimated number of skilled metal workers in the United Kingdom.

The low wing aluminum monoplane was a relatively new technology in the 1930s. As a side note, nearly all wartime fast patrol boats and subchasers were mainly of wooden construction. Steel was too heavy and aluminum welding techniques were not refined enough for efficient mass production. In other words, the shipyards and the admiralty had to compete with other industries for the services of highly experienced carpenters.

Re: All metal Mosquito ??
 

As an aside, and from direct personal experience, the rivalry between HP and DH was so intense that I'm rather surprised that HP made any bombracks for DH, even under wartime conditions. As the bulged bombbay was no longer than the original, which could only take 4x500lb if the fins were shortened, are you describing some kind of triple rack? The usual carriage of 6x500lb would be with 2 underwing.

The later Mosquito day bombers were not escorted by Mosquito fighters - the Mosquito was not employed as a day or escort fighter, not least because of its inability to fight with single-engine fighters. The Mosquito made a superb night fighter, and heavy fighter for Coastal Command, but not where enemy fighter opposition could be expected. For longer-range missions, Mustangs were available which could comfortably exceed the range of the FB Mk.VI, but 2TAF did not fly deep daylight penetrations.

The Mosquitos were indeed flying missions with deeper penetration than the Blenheims, but they were employed as a direct replacement. The point is that such missions, however spectacular from the propaganda point of view, resulted in unacceptable losses. As indeed did similar US attempts with the B-26.

Re: All metal Mosquito ??
 

Only after several years in the trade.:) Actually the proper trade name would be cabinet makers. Do not ever call a cabinet maker a carpenter!

Re: All metal Mosquito ??
 

Briefly
Yes they were triple bomb racks and there were times when Mosquito's were used as the escort, normally they were Typhoons or Mustangs. It wasn't common but it did happen.

I will comment later on losses.

Re: All metal Mosquito ??
 

Even further aside, the Admiralty supplied the plans for wooden fast patrol boats to the Russians who in turn were supplying them to other countries at least into the 1980s. Vosper Thornicroft fitted out at least 6 fpts with modern weapon systems and a fibreglass skin on the hull.

Re: All metal Mosquito ??
 

Weight of a 24" x 60" panel:

Aluminum alloy - 0.91lb (0.063" #26 and #27)

Balsa sandwich - 10.2lb (2 x 1/8" plywood + 1/4" balsa @ 8lb/cf)

Australian propaganda video
http://www.youtube.com/watch?v=c7cVvYdLeek

Re: All metal Mosquito ??
 

The weight of the balsa sandwich is about right, but the aluminium calculation is 10x out. Should be 9.1lb. And you are not calculating like with like or calculating what was available in 1940. Aluminium composites were not in use. Wood composites were. An unstiffened sheet of aluminium that size 1/16" thick would weigh 9.5 lb by itself.
The ratio also changes if you make the plywood thinner and the balsa thicker. For example 1/16" ply and 1/2" balsa comes out to about 8lb and is probably stronger.
Today, if you want to go really light, you use epoxy graphite with a protective surface of Kevlar against impact damage.

Re: All metal Mosquito ??
 

Right, I messed up. :o:o:o

A 0.0641" sheet (2'x5') of aluminum weighs 9.3lbs according to the Machinery's Hand Book.

Sure it is like with like, as that is the skin of the a/c.

More research has turned up, 1/16" and 5/64" plywood and 7/16" balsa.
http://users.skynet.be/BAMRS/dh103/f...nstruction.htm

So as you say 8lb or a little less.

Re: All metal Mosquito ??
 

Sorry, but it is clearly not like with like. An aluminum skin of that thickness needs lots of frames and stringers behind it for stiffness and out of plane loads, the wood composite needs much less back up structure, and no mechanical fasteners. Besides the weight of the frames and stringers, there is considerable time required for assembly, and many chances for error in installing the fasteners - these become crack starters and shorten the fatigue life considerably. That is one of the big advantages of composites (wood or otherwise) over fabricated metal.

I'm surprised that no one has mentioned one of the biggest draw backs to wooden structures - environmental deterioration of the wood and glue. The RCAF learned this the hard way, watching the Oxfords, Ansons and Cranes in the BCATP literally dissolve in the Canadian winters when they were not meticulously maintained. It is interesting to note that when the RCAF established several reserve light bomber squadrons right after the war they could choose between two light bomber fleets already paid for and stored in Canada: several hundred brand new or nearly completed Mosquitoes at Downsview, and about 50 well used B-25s left over from 5 OTU on the west coast. The Mosquitoes were all sold or scrapped within a few years, the B-25s carried on in RCAF service until the early 1960s.

I'm also surprised nobody has mentioned a more direct comparison: the wooden fuselage Spitfire tested during the war, using Mosquito fabrication techniques. Maybe somebody could dig up some figures on that project?

Re: All metal Mosquito ??
 

Check out the claims for this wooden Spitfire! I want one, but my wife won't let me!

http://www.spitfirebuilder.4t.com/catalog.html

Quote from the site:

"The use of both classic construction methods and the wood sandwich skins result in an aircraft that is a ton lighter than the original Spitfire Mk, IX, yet is stressed to 10G ultimate load. At 2,000 pounds lighter with the 1200 horsepower Allison V-12, the SAC Spitfire will easily outperform any original MkIX. Acceleration and rate of climb, will be nothing short of breath taking. Turning performance, maneuverability, low speed handling, and balanced field length will be noticeably better than an original metal Spitfire."

Re: All metal Mosquito ??
 

Another quote from the site:

"The beautifully rounded shape of the Spitfire's fuselage is built with the same "balsa-ply-balsa" sandwich construction technique as used on the famous De Havilland Mosquito, giving tremendous stiffness and strength, but a lot less weight than metal."

I rest my case.

Re: All metal Mosquito ??
 

So this wooden Spitfire IX has a tare weight of 3800lb.

Re: All metal Mosquito ??
 

The aeronautical equivalent of vapourware.

Re: All metal Mosquito ??
 

Have you considered termites, beetles, worms, fungus?

Maybe the RAF could save some coin by building a fleet of Eurofighter Typhoons made of less expensive stealthy materials, like balsa-wood.

Re: All metal Mosquito ??
 

Do you want to build a plane from them or are you worried about them eating the structure? ;) Seriously, today you can protect the wood from all bugs and fungus completely.

The other problem with wood or any composite aircraft is surface heating at high speed. You need a heat shield or sacrificial surface to protect the temperature sensitive structure. Aluminium is not much better which is why Titanium is used a lot.

Re: All metal Mosquito ??
 

Let's remember also about the US contribution in Mosquito. That aircraft was skinned with the American plasticized birch veneer manufactured by the Pluswood Inc., which in fact was a consortium of three companies -- the Northern Hardwood Veneers Inc., Lullabye Furniture Corp. and Algoma Forest Products Ltd. The Pluswood skin (called during WWII the "wood alloy") was far lighter than duraluminum, highly resistant to fire and abrasion, and had very good weight-strength ratio.

Re: All metal Mosquito ??
 

I thought Roddis did the plywood?

Re: All metal Mosquito ??
 

The Americans were consultants at Mosquito manufacturing process although the British not necessarily want to remember about it today. Three Mosquitos were tested throughout the war in the USAAF R&D center at Wright Field.

What is mentioned above is a special veneer for aviation industry, not a plywood. The forumers many times do not differentiate plywood from veneer in airframe construction. In interwar period and during WWII the Americans were the world's leaders in plasticized veneers, molding technologies (Duramold process) and the autoclaves for an airframe construction -- pioneer autoclaves as known today for the GRP- or carbon-made airframes. For example, there was a feasibility study done during WWII to manufacture all-wood P-39 fighter. As it was counted then all-wood P-39 would be close to 10mph faster than its all-metal counterpart. There was also a plan to manufacture all-wood SBD Dauntless dive bombers. In period American opinion properly built wooden aircraft has a longer cruising range, is faster and can carry a heavier payload.

When it comes to Mosquito -- the best materials on its manufacturing were published during WWII. I recommend to read an interesting and well-illustrated article "It's The Skin" by Professor Nicholas J. Hoff -- the Air Progress monthly, Vol. 3 No. 3, September 1943.

Re: All metal Mosquito ??
 

That's great info - many thanks, will try to find that article.

Re: All metal Mosquito ??
 

The WWII era American professional aviation press is full of extremely interesting articles on wooden technologies applied in the airframe structures written by the engineers, researchers, CEOs of various companies etc.

Writing his article on Mosquito Professor Nicholas J. Hoff foresaw very well such discussions as can be seen over here. He wrote among others:

"That wood construction can compete with and even surpass metal construction may seem strange to the nonspecialist in aircraft engineering."

Re: All metal Mosquito ??
 

Graham - its hard to say as rivets are an often unaccounted for component of weight for metal fabrication.

Having said this I have long been out of the industry and my only experience with non-metal fabrication components was with 1960-70's composites and never wood construction.

It is intriguing to me to visualize re-designing an existing conventional airframe to employ spruce versus 2024 or 7075, especially in the case of shear load transfer for both panels and beams, where the adhesives replace rivets and fasteners.

Re: All metal Mosquito ??
 

Re: post #31 and strange wording "balsa-ply-balsa".

We do have misunderstanding in this case. For the Mosquito airframe it was "ply-balsa-ply". Below you can see one of illustrations of Professor Nicholas J. Hoff's article mentioned.

http://img143.imageshack.us/img143/6770/11875863.jpg
Uploaded with ImageShack.us

Re: All metal Mosquito ??
 

You did good job in this thread. You are absolutely right. The Mosquito was neither better nor worse than all-metal planes of that era. But in the field of wooden airframes it was high-tech aircraft in the 1940s circumstances.