De Havilland Mosquito (Wood vs. Metal)

[cvairwerks]

Here's a list of things that I know come into play when selecting a skin thickness during the design process:
1. Material desired
2. Design profile
3. Design stress calculations
4. Placement on the airframe
5. Fatigue limits
6. Impact limits ( areas of the fuselage where there will probably be impacts during routine operations...ice, rocks, mud ect...)
7. Forming method
8. Attachment method
9. Thermal loading ( very important as you approach and exceed the transonic flow around locations on the airframe)
10. To a point, repairability and maintainability
11. Operational weight

Shortround6: You're thinking of "chem milling" of various parts. Resist is applied to areas that the operator does not want to remove material and then the part is either sprayed or submerged in an acid bath, for controlled time periods to chemically remove material in the uncoated areas. Compared to standard machining process, it's faster and much less prone to warping of the part due to internal stress relief that can and does happen during the mechanical material removal.

 

[Crimea_River]

6. Impact limits ( areas of the fuselage where there will probably be impacts during routine operations...ice, rocks, mud ect...)......

A interesting anecdote about our B/PR 35 RS700 that was used by Spartan Air Services in the late 50's. It ran photo mapping missions off gravel runways in northern Canada. When we got around to restoring the tail plane, we found that we had to strip a layer of fiberglass from the skin before inspecting the plywood, only to find several holes in the plywood skin. Inside the tailplane, we found bits of gravel that had been kicked up by the props that had obviously penetrated the skins.

Photo by Richard de Boer.

 

[MikeMeech]

Hi
Supermarine had quite a long experience with metal construction by WW2, the Southampton Mk. II has already been mentioned, and flying boats were produced with metal hulls (plus metal wings with fabric covering) from the late 1920s. The book 'Metal Aircraft Construction' by M. Langley, Pitman, 1937, has the following reference Supermarine:

The following text (not photos) apply to Supermarine:

The company also had experience with high speed metal aircraft with the Schneider Trophy racers with the S.5 of 1927, S.6 of 1929 and S.6B of 1931.

Mike

 

[MikeMeech]

I dont know, but Supermarine didnt have any experience of making planes out of Duralumin until the Spitfire was ordered. Neither did Hawkers, the Hurricane was mainly made from "dope" until 1940.

Hi
Nothing is made of "dope" so presumably a 'joke' or just a 'dopey' comment?

Mike

 

[Reluctant Poster]

Hi
Nothing is made of "dope" so presumably a 'joke' or just a 'dopey' comment?

Mike

Doped fabric

 

[pbehn]

Hi
Nothing is made of "dope" so presumably a 'joke' or just a 'dopey' comment?

Mike

I was talking about the surfaces, if you take the dope (or doped linen) off a 1939 Hurricane what sort of aeroplane do you have?

 

[Reluctant Poster]

I strongly agree with your recommendation of J.E. Gordon's book "The New Science of Strong Materials". He also wrote a book called "Structures, or why things don't fall down". Basically, it's more of the same. He had an interesting fascination with bias cut material in ladies dresses.

We need to distinguish between non-strategic materials, and non-exotic materials. The Germans, and to a lesser extent the Japanese, wanted to build wood aircraft. They had no access to balsa.

The Mosquito's fuselage and wing surfaces were something like 5/8" thick. It was a thick balsa core sandwiched between layers of spruce. This is a modern composite structure. Balsa still is used today as the matrix layer in composite structures. A lot of cross country skis are carbon or glass fibre enclosing a balsa core.

Google composite balsa panel

If you are building a tubular truss structure, steel, titanium, aluminium and magnesium are in a line, with the same ratios of elastic modulus versus mass. You should build using the cheapest, most easily fabricated material.

If you are building a cantilever structure loaded in bending, for a given weight, aluminium beams will be thicker and stiffer than steel ones. The stresses that will make this structure break, are several orders of magnitude more complicated to manage. On the de Havilland Hornets, the upper wing skin was spruce/balsa/spruce composite, and the bottom face was aluminium. The much thicker composite structure was more resistant to buckling, which is how most structures fail in compression.,

I have specified beryllium for some scanner mirrors. Beryllium is about half again the stiffness of steel, and the density of magnesium. It is also poisonous as all hell, and very few people are willing to machine it. The mirrors were about $10K each. If you were to try to eat one, the immediate threat to your health would be blunt trauma.

Beryllium was banned from Formula 1 in 2001

Banned: Beryllium

The banning of beryllium and its alloys from F1 did not generate nearly as much controversy as other technologies which were banned.

www.racefans.net

 

[Howard Gibson]

Beryllium was banned from Formula 1 in 2001

Banned: Beryllium

The banning of beryllium and its alloys from F1 did not generate nearly as much controversy as other technologies which were banned.

www.racefans.net

If you were to try to eat a piston from a 2000 McLaren racer, I am sure you would be in danger of blunt force trauma.

 

[wuzak]

Beryllium was banned from Formula 1 in 2001

Banned in engines from 2001. Banned everywhere else from 1998 (some teams were using it in brake calipers).

 

[ThomasP]

At some point in the late-1950s or early-1960s it was realized that beryllium could play a similar part in solid rocket fuel that aluminum plays in explosives. I do not know about other countries, but the US started using beryllium in its battlefield missile systems. After many cases of beryllium poisoning and a number of deaths, beryllium use in solid rocket fuels for ground based rocket engines was discontinued in the late-1970s (I think) although it was still used in Air-Air missile rocket motors. The effect was sometimes likened to asbestosis (it was even called berylliosis) although it had a different progression to the end phase where it could lead to organ failure and/or where the lungs stopped being able to function. Unlike asbestosis, it is possible to develop berylliosis from a single exposure if enough of the right size particles are inhaled, leading to death in less than a week in the worst cases.

 

[Deleted member 68059]

Beryllium was banned from Formula 1 in 2001

Banned: Beryllium

The banning of beryllium and its alloys from F1 did not generate nearly as much controversy as other technologies which were banned.

www.racefans.net

Just an FYI, that they were actually testing for this stuff in WW2.

 

[ThomasP]

re the FMA I.Ae.30 Nancu

TOGW was about 19,300 lbs when it was operating in the same ballpark for range and load carrying as the Mosquito. The 16,755 lb was maybe the gross flying weight during tests? at the original designed operating weight?

 

[FLYBOYJ]

re the FMA I.Ae.30 Nancu

TOGW was about 19,300 lbs when it was operating in the same ballpark for range and load carrying as the Mosquito. The 16,755 lb was maybe the gross flying weight during tests? at the original designed operating weight?

If you want to make a structural weight comparison, I think it's better to use empty weight.

According to Mr. Wiki the Sea Hornet was 11292 empty

The Nancu was 13686 empty.

If my math is correct the Nancu was about 28% heavier, empty.

Going back to the OP - I would guess you would have a similar weight increase if you built a Mosquito entirely of metal products (mainly aluminum) in lieu of wood.

I was going to "wag" a number to say 30 - 40% heavier when I first saw this thread.

My 2 cents - use it for gas!

 

[cherry blossom]

Diverging even further from the subject, I can add that long ago, I used beryllium for windows because they were fairly transparent to X-rays (there are some notes on this application at Caring for the Beryllium Window of an X-ray Tube - X-Ray Technology Learning Centre- Oxford Instruments) but for mirrors naturally used gold (see Gold mirrors for X-ray astronomy - Gold Bulletin).

 

[Howard Gibson]

If you want to make a structural weight comparison, I think it's better to use empty weight.

According to Mr. Wiki the Sea Hornet was 11292 empty

The Nancu was 13686 empty.

If my math is correct the Nancu was about 28% heavier, empty.

Going back to the OP - I would guess you would have a similar weight increase if you built a Mosquito entirely of metal products (mainly aluminum) in lieu of wood.

I was going to "wag" a number to say 30 - 40% heavier when I first saw this thread.

My 2 cents - use it for gas!

When the Japanese converted their all-metal Ki.84 "Frank" into the wooden Ki.106, the mass went from 3900kg to 4200kg. The heavier wooden aircraft proved to be just as fast as the metal one due to its smooth, polished finish. For an interceptor and dogfighting aircraft, the increased mass is a problem. On a high-speed bomber...

My sources are not clear on exactly how the wooden structure worked. The Japanese lacked the experience de Havilland had with wooden airframes. It is a safe bet they did not have balsa wood.

 

[FLYBOYJ]

When the Japanese converted their all-metal Ki.84 "Frank" into the wooden Ki.106, the mass went from 3900kg to 4200kg. The heavier wooden aircraft proved to be just as fast as the metal one due to its smooth, polished finish. For an interceptor and dogfighting aircraft, the increased mass is a problem. On a high-speed bomber...

My sources are not clear on exactly how the wooden structure worked. The Japanese lacked the experience de Havilland had with wooden airframes. It is a safe bet they did not have balsa wood.

When you say "mass," speak in operational terms, "empty weight" as that's the weight it would roll out of the factory with no external operational equipment or liquids added. 5,864 lb for the Ki.84, 6505/ 6,499lb lbs for the Ki.106, according to Mr. Wiki and various internet sources and I've seen, some of those sources show various speeds, including some slower than the production Ki.84. If it was the same speed or slightly slower, there could be a number of reasons why (change of C/G, different internal equipment, etc.) Smooth surfaces don't last long during operational situations and in general maintainers would worry more about getting the plane in the air first, especially if you're on the ropes.

 

[Glider]

A lot of the conversation in the thread is around the possible weight gain/loss of one material over another. There was I believe one advantage of wood over metal and that was aerodynamics.
The mosquito was very clean with no rivets which can generate a fair amount of drag, which obviously would help the performance

 

[Zipper730]

I think 2024 (Back then it was 24T) and 6061was found on most British and US aircraft. 7075 was adopted by the US towards the end of WW2 IIRC. The Japanese id use a lot of 7075 but the alloy was known by other countries

Fascinating, I didn't think we were using it until the early 1950's.

If my math is correct the Nancu was about 28% heavier, empty. . . . Going back to the OP - I would guess you would have a similar weight increase if you built a Mosquito entirely of metal products (mainly aluminum) in lieu of wood.

How much does the B.IV weigh empty? Also, what's the most common Bomber and Fighter-Bomber variants?

I had looked into a thread which touched upon a metal-mosquito design. It was stated here that with metal construction the plane would have been 40% heavier (WAG's often are where most guesses start lol), however I was also told that the 40% weight gain didn't factor in the landing-gear (would increase to some degree), the weight of the systems (no change), crew (no change), fuel/oil (would go up if needed to meet fuel fraction), and armament (no change).

At some point in the late-1950s or early-1960s it was realized that beryllium could play a similar part in solid rocket fuel that aluminum plays in explosives.

I didn't know that, but it sounds like a terrible idea.

 

[Howard Gibson]

When you say "mass," speak in operational terms, "empty weight" as that's the weight it would roll out of the factory with no external operational equipment or liquids added. 5,864 lb for the Ki.84, 6505/ 6,499lb lbs for the Ki.106, according to Mr. Wiki and various internet sources and I've seen, some of those sources show various speeds, including some slower than the production Ki.84. If it was the same speed or slightly slower, there could be a number of reasons why (change of C/G, different internal equipment, etc.) Smooth surfaces don't last long during operational situations and in general maintainers would worry more about getting the plane in the air first, especially if you're on the ropes.

When I say "mass", I am being pedantic. Mass is an amount of material, and the units are kilograms and slugs. Weight, the force we all exert due to gravity, ought to be quoted in Newtons and pounds. I work in engineering and I need to know where to insert G in calculations. I weigh 210lb. I have a mass of 95kg.

Having said that, my reference used kilograms. The information we need either is DeltaM (300kg) or DeltaW (660lb). This is an excellent argument to not bring up at your neighbourhood butcher shop. They have too many sharp implements lying around.

 

[wuzak]

Fascinating, I didn't think we were using it until the early 1950's.
How much does the B.IV weigh empty? Also, what's the most common Bomber and Fighter-Bomber variants?

I had looked into a thread which touched upon a metal-mosquito design. It was stated here that with metal construction the plane would have been 40% heavier (WAG's often are where most guesses start lol), however I was also told that the 40% weight gain didn't factor in the landing-gear (would increase to some degree), the weight of the systems (no change), crew (no change), fuel/oil (would go up if needed to meet fuel fraction), and armament (no change).


I didn't know that, but it sounds like a terrible idea.

The FB.VI was the most common fighter-bomber variant, and the most produced Mosquito variant (~2,300). Apart from a few specialist versions (FB.XVIII Tsetse), other fighter-bomber variants were the Canadian (FB.21, FB.26) and Australian (FB.40) built versions of the FB.VI.

The most produced single bomber type was the B.XVI, with 400 built. However, the Canadian built B.VII, B.XX and B.25 were all versions of the B.IV, but with different Packard supplied engines. There were 273 B.IV, 25 B.VII, 245 B.XX and 400 B.25 built.