What if: Mosquito vs P-38

[drgondog]

Joe it was you and i that had that conversation. I agree with you. But people are trying to say that the Mosquito was also weak in the air. I dont believe that is the case, based on previous conversations that Ive had with people that flew the mosquito



In the air, the Mosquito was strong, incredibly strong. It was on the gtround that the problems arose

I just assumed that aircraft like the P-51 and Mosquito would be comparable in flying hours.....I suppose that a dangerous assumption......

Fatigue is the great killer of airframe structures - Knowledge of aeroelastic effects and fatigue due to reversible loads and high frequency inputs was in its infancy during WWII.

Have no idea what materials properties Mossies had relative to reversible loads. Would think to look to materials degradation due to moisture and bonding failures from glue decomposition as questionmarks?

[Maximowitz]

I'm not adding anything to the debate (I know diddly squat about either aircraft) but if any of you are in or visiting the UK you could do worse than go here:

Mosquito Museum

I never even knew it existed....

[Butters]

Fatigue is the great killer of airframe structures - Knowledge of aeroelastic effects and fatigue due to reversible loads and high frequency inputs was in its infancy during WWII.

Have no idea what materials properties Mossies had relative to reversible loads. Would think to look to materials degradation due to moisture and bonding failures from glue decomposition as questionmarks?

Wood excels at resisting fatigue. A mature tree is subject to literally millions of bending movements in its lifetime from wind forces. The cellular structure of wood has evolved to deal with this challenge by a complex composition of rigid and flexible components that give it tremendous resistance to the forces of compression, tension, and torsion along its longitidunal axis ( This varies of course,not only with species and individuals within the species, but also within the individual tree itself). that's why wooden boats and ships can handle the constant pounding of the seas for years on end.

Because wood is a structurally complex, and extremely variable(as opposed to metals), engineering with wood is inherently more complex than with metal structures. The strength of a wood component is dependent upon factors like grain. End grain, for example, is highly resistant to compression, but subject to fracture (splitting) Because wood is so variable, and because the properties of a component will differ depending on how it is milled, engineering something like a high-performance a/c from wood is a daunting task. Esp with the types of adhesives and glues that were available during the war.

Not to mention the problems with moisture...The first thing anyone who works with wood learns, is that wood MOVES. Something that has to be kept in mind all the time.

JL

[Colin1]

Wood excels at resisting fatigue. A mature tree is subject to literally millions of bending movements in its lifetime from wind forces. The cellular structure of wood has evolved to deal with this challenge by a complex composition of rigid and flexible components that give it tremendous resistance to the forces of compression, tension, and torsion along its longitidunal axis ( This varies of course,not only with species and individuals within the species, but also within the individual tree itself). that's why wooden boats and ships can handle the constant pounding of the seas for years on end.

Because wood is a structurally complex, and extremely variable(as opposed to metals), engineering with wood is inherently more complex than with metal structures

Just some observations
A mature tree is still alive and during its lifetime, can and does constantly repair itself, the moisture inherent within living wood will certainly lend itself to the ductile qualities of the tree whilst stresses in the form of bending movements are imposed upon it; seasoned wood on the other hand, can for the purposes of fatigue, be considered 'dead'.

Are not the bending movements of trees predictable to a large degree, trees normally bend to and fro subject to wind forces in a quasi-periodic manner. The forces subjected on a fighter engaged in manoevres would be more random in nature and could be considered more violent, if shorter in overall duration.

Would you consider that a valid argument?

[Butters]

Only the few mm's under the bark are actually alive. And I think you're confusing ductility with elasticity. Wood is not a ductile material. It is intrinsically elastic and durable along specific axis. At least the types selected for building a/c components

Even kiln-dried wood normally has a fair amount of moisture, and any exposed wood, esp end-grain, will absorb moisture, so unless the wood is encapsulated in a waterproof coating (Like epoxy), it will eventually reach an equilibrium with the environment.

It doesn't matter whether or not the movement is periodic. The drawing of a wooden bow is very slow compared to the release. All that matters is that the force on the wood does not exceed its strength. The various attachment points of the components are probably the most critical design factors in a well-engineered wooden a/c. Just like a metal one...

JL

[Maximowitz]

Would you consider that a valid argument?

No. Each tree has a unique cellular structure and the moment it is cut down other forces come into play. Unless wood is correctly dried (kiln or otherwise) it is prey to shinkage and splitting. I've spent the last thirty years of my life playing with wooden things and unless the correct precautions are taken wood is a very volatile building material.

[Waynos]

The fuselage of the Mosquito was extremely strong, possibly more so than a metal structure, because there was no internal frame. The fuselage was made as a laminated shell in two halves, rather like the fuselage of a plastic model kit, and the grain of the wood was arranged spirally, and the layers arranged with opposing spiral, this gave immense strength and, as the load was dispersed over the entire surface, a hole in it was less critical than if, say, a major load bearing structure was severed, as could happen with a metal airframe, as there was much more area available to take the strain.

As has been pointed out , its real weak spot was in hot humid conditions, such as the pacific theatre, where not only might the wood rot, but also the glue would literally come unstuck. In ETO however there was no such difficulty.

Here is a photo which shows another aspect of the Mossies survivability. This aircraft of 464Sqn not only had a huge chunk of wing missing, but also only had one engine and few hydraulics, yet made it back to base and a successful landing. Testament to both plane and pilot I'd say.

[FLYBOYJ]

I've spent the last thirty years of my life playing with wooden things and unless the correct precautions are taken wood is a very volatile building material.

BINGO!

[drgondog]

The fuselage of the Mosquito was extremely strong, possibly more so than a metal structure, because there was no internal frame. The fuselage was made as a laminated shell in two halves, rather like the fuselage of a plastic model kit, and the grain of the wood was arranged spirally, and the layers arranged with opposing spiral, this gave immense strength and, as the load was dispersed over the entire surface, a hole in it was less critical than if, say, a major load bearing structure was severed, as could happen with a metal airframe, as there was much more area available to take the strain.

As has been pointed out , its real weak spot was in hot humid conditions, such as the pacific theatre, where not only might the wood rot, but also the glue would literally come unstuck. In ETO however there was no such difficulty.

Here is a photo which shows another aspect of the Mossies survivability. This aircraft of 464Sqn not only had a huge chunk of wing missing, but also only had one engine and few hydraulics, yet made it back to base and a successful landing. Testament to both plane and pilot I'd say.

I agree strength of Mossie.

Suspec that what is hidden in that picture is a forward spar and what appears to be an aft spar, which combined with ribs and skin would make a very durableand strong design.

If I were to guess on the design the spars are constant thickness beams rather than typical beam cap/shear web/beam cap designs of aluminum construction

[Waynos]

Thats right. The front and rear spars were built up from 1/2 inch thick laminated spruce planks, with spruce and birch ribs and stringers and then the laminated wing skin was double thickness on the top surface, single below.

[Butters]

The fuselage of the Mosquito was extremely strong, possibly more so than a metal structure, because there was no internal frame. The fuselage was made as a laminated shell in two halves, rather like the fuselage of a plastic model kit, and the grain of the wood was arranged spirally, and the layers arranged with opposing spiral, this gave immense strength and, as the load was dispersed over the entire surface, a hole in it was less critical than if, say, a major load bearing structure was severed, as could happen with a metal airframe, as there was much more area available to take the strain.

As has been pointed out , its real weak spot was in hot humid conditions, such as the pacific theatre, where not only might the wood rot, but also the glue would literally come unstuck. In ETO however there was no such difficulty.

Here is a photo which shows another aspect of the Mossies survivability. This aircraft of 464Sqn not only had a huge chunk of wing missing, but also only had one engine and few hydraulics, yet made it back to base and a successful landing. Testament to both plane and pilot I'd say.

The method of fuselage construction that you describe is very similar to a method used in building modern wood-epoxy boats. The double diagonal cold-moulded technique results in strong, resiliant and lightweight hulls that are easily a match for fiberglas or metal boats. The method also makes it much easier to form complex compound curves than other techniques.

BTW, I'm a professional home builder/cabinet maker, and have also put in a few years as a boat builder. Unfortunately, I'm now very sensitive to epoxies, so I can only use them on an occassional basis.

JL

[drgondog]

The method of fuselage construction that you describe is very similar to a method used in building modern wood-epoxy boats. The double diagonal cold-moulded technique results in strong, resiliant and lightweight hulls that are easily a match for fiberglas or metal boats. The method also makes it much easier to form complex compound curves than other techniques.

BTW, I'm a professional home builder/cabinet maker, and have also put in a few years as a boat builder. Unfortunately, I'm now very sensitive to epoxies, so I can only use them on an occassional basis.

JL

epoxy can be nasty stuff - hopefully 'being sensitive' was the only damage?

I have fooled around with the stuff on boats, gunstocks, car bodies and R/C aircraft - have a healthy respect for it!

[drgondog]

Thats right. The front and rear spars were built up from 1/2 inch thick laminated spruce planks, with spruce and birch ribs and stringers and then the laminated wing skin was double thickness on the top surface, single below.

The double thickness on top was a recognition that the major bending due to lift loads were taken out as compression in top skin/beam cap, whereas the bottom skin was in tension. (in general)

[fastmongrel]

A small test for those people who think a plywood airframe is weaker than an aluminium one.

take 2 sheets both the same size and weight 1 of duralium 1 of quality plywood support both sheets around the edge.

Pick up 2 lb 6 oz ball pein hammer and take turns in hitting both sheets with the ball end. I got through the duralium in 11 hits, after 11 hits on the ply it was delaminating and bulging on the underside and it had split from side to side but it was still in one piece. It took 2 more hefty blows to penetrate the ply basically I just punched a big piece of chewed up ply through the sheet.

A rubbish test that proves that I dont want anyone firing bullets at me no matter what the aircraft is built of but its fun smashing things up

[Colin1]

A small test...

I got through the duralium in 11 hits,

after 11 hits on the ply it was delaminating and bulging on the underside and it had split from side to side but it was still in one piece

So the alum perforated, the plywood split

If it's split from side to side then it's not in one piece. Now add load forces from an aircraft engaging in violent evasive manoeuvres.

I think some useful points have been made here concerning the viability of wood for airframes construction, I don't think that this was one of them.