I have never read anything about the meredith effect that discussed the mosquito, I found a long discussion about the Hornet and the main concern was disturbing the airflow under the wing. Would it be more accurate to say they had the best low drag solutions to cooling water cooled engines
P 51 Mustang vs Mosquito?
- Thread starter Blitzrockie
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Back in high school I always hated having to do the extra work to stay on top of my wood prop and spars (7AC-65) while my buddy only had to look for corrosion (Luscombe 8a) occasionally (dammit, he was lazy!). I haven't bothered with wood anything since, although I wood be willing to try a vintage Aeroprop automatic propeller with wood blades ... those are really cool - i think, anyway.
FLYBOYJ
"THE GREAT GAZOO"
Read my first post - "Wood structures are hard to maintain and are susceptible to swelling and shrinkage depending on climate and environment," and I'll further elaborate, temperature - the cool humidity is actually good for wooden aircraft, don't move them to the desert.
You mention some combat exploits - agree, the Mosquito was a great aircraft.
The "poor maintenance" quote was taken from one article, I know there are other articles stating the maintenance challenges of the IAF operating the Mosquito.
In the bigger picture, if wood was so good to use for military aircraft construction, why did its use fade away after WW2?
More info:
"At Don Muang, they suffered a number of accidents on landing or in the circuit, and sadly encountered more serious structural problems with their aircraft, one of which broke up in bad weather on a long flight to Singapore, causing the Squadron's final losses of the Second World War."
and...
"Structural problems
The structural difficulties of the de Havilland Mosquito have been discussed in a number of places, most tellingly by Jefford in The Flying Camels (at Annex K).
It was eventually determined that the initial problems were the result of a combination of poor mate-up of some structural members, poor gluing practices and failure of glued joints, apparently most common among Far East aircraft after prolonged outdoor storage. It also appeared that swelling of the top skin could lead the securing screws to pull through.
Subsequent examination of European theatre aircraft found a much lower prevalence of joint defects, and no lifting of wing skins. Further investigation in India identified two main defects: the wing spar scarf joints, and the spar boom joints with the plywood skin and other ply members, leading to lifting of the upper surface plywood skin.
Consequently, Modification 638 was adopted: adding a spanwise plywood strip to seal the upper surface skin joint along the length of the front spar; along with application of protective aluminium dope overall (from February 1945). Despite these efforts, in the tropical conditions of the Far East the combination of heat and water soakage continued to give rise to swelling and shrinkage, resulting in spar defects until as late as 1954."
de Havilland Mosquito
Lee Atwood was describing the difficulty of designing the Mustang cooling duct and how they finally got that to work properly at a post-war engineer's convention where he also talked about how Supermarine and Messerschmitt failed and De Havilland got it right. According to him, having the coolers right on the leading edge made the rather tricky duct design much easier than when working with recessed coolers between the spars. I don't know if he had inside knowledge of a conscious attempt at achieving Meredith Effect at De Havilland or if he simply assumed they achieved it based on his own analysis of the Mossie's performance. The English always assumed the Mustang's speed was due entirely to its wing (until their experience with the Spiteful) because they failed with "Meredith" on the Spitfire but Lee acknowledged that the Mustang's laminar wing was unable to perform in the field as hoped while the cooling system performed beyond expectations.
From what I have read the later Me109s had a quite good use of the meredith effect the spitfire was so/so depending on which model. As far as I know the thrust from the P51s meredith effect merely compensated for the drag of the inlet duct. On the Mosquito the outlet of the cooling system was under the wing, it couldnt provide forward thrust but then the inlet was in the wing leading edge and so didnt cate drag either.
On the Hornet construction of a system to provide thrust by the Meredith effect was impossible due to the wing spar, the challenge was therefore to re introduce the airflow from the radiators without turbulence.
What you are saying is environments change and some materials are badly or well suited to them. Try using an RAF Harrier on a carrier and you will have similar problems to the Mosquito encountered. When you talk about the desert then you must understand deserts have many conditions. When I was in Saudi Arabia the humidity at night was frequently 99% your car was stood in a puddle every morning due to condensation, add in a sand storm when the sand is between 0.5 and 1% salt and you have a great environment for corrosion of aluminium. In two years in KSA I saw rain 3 times and despite that all cars there are rust buckets after 3 years.
I am not saying that the mosquito didnt have problems or that wood is a miracle material just that the Mosquiotos problems such as they were were minor compared to (for example) the Typhoons problems in winter getting it to start and in summer stopping the abrasive soil devouring the engine internals, similar situation in North Africa and Malta for Spitfires and Hurricanes
[QUOTE="pbehn, post: 1278340, member: As far as I know the thrust from the P51s meredith effect merely compensated for the drag of the inlet duct.[/QUOTE]
MERELY compensating for cooling drag is HUGE. For piston aircraft of just about any size, type, and performance class, cooling drag represents 30% to 40% of total airframe drag. Their's a lot more drag inside that little scoop than its frontal area would make you think. Cancel that with Meredith thrust, and you should more than compensate for a laminar wing that doesn't live up to its wind tunnel promise under field conditions.
MERELY compensating for cooling drag is HUGE. For piston aircraft of just about any size, type, and performance class, cooling drag represents 30% to 40% of total airframe drag. Their's a lot more drag inside that little scoop than its frontal area would make you think. Cancel that with Meredith thrust, and you should more than compensate for a laminar wing that doesn't live up to its wind tunnel promise under field conditions.
FLYBOYJ
"THE GREAT GAZOO"
Comparing Harrier ops to this is like comparing apples to a unicorn. Although aluminum can corrode, you can control it. When wood structures expand and contract, they weaken and split.
You're not getting it - changes in heat AND humidity or just one of will do in a wood aircraft. The humidity could be 99% in Saudi - if the aircraft was originally being operated in mild temps and it now sits in temps over 100F, the structure will shrink. Take it to a place that is zero humidity and still has high temps it will shrink even more. I worked on a Pitts brought to Southern California from Seattle. As soon as the temperatures rose, every metal fitting connected to wood structure loosened up, some of the wood screws were removable just by pulling on the heads. I've seen this on Mooneys and Bellancas as well. This will happen to ANY wood aircraft in time.
The fact that the IAF operated their Mosquitoes until 1957 is a miracle.
Thorlifter
Captain
Question about the restored Mosquitos, especially the ones that are (or will be) flying.......
Are they being restored with wooden structures or are they using aluminum?
Are they being restored with wooden structures or are they using aluminum?
FLYBOYJ
"THE GREAT GAZOO"
AFAIK they're using wood
Thorlifter
Captain
I certainly would have thought they would use aluminum in the flying ones. To me, and I'm certainly not an aviation expert, restoring something with a material that has a shorter life span would be like putting the Jumo 004 engines back in the new ME-262's. And doing it just for historical accuracy certainly isn't the answer (at least to me). Now if you are restoring a static Mossy, that would be fine.
Repair techniques on aircraft structures are required to use materials and methods identical or extremely similar to the original. How would you interface wood structure and metal repair in a way that's approved and proven to be as strong as the original? Metal structures are held together by point contact fasteners such as rivets or screws, which are acceptable because the sheet metal is strong enough to withstand the concentration of stress around the fasteners without their tearing through. Plywood construction a la Mosquito is fastened by adhesives which spread the stress along the entire joint rather than concentrating it at each fastener. Point contact fasteners are the weak points in wood structures.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
As long as the laminate can tolerate the stress.
This was the problem the Germans ran into with their Tego film for their laminates and cost them a great deal, in the way of delays and setbacks: especially with the Ta154, which was a victim of the delaminating wood composites.
I do "get it" what I dont get is that people always quote conditions in the far east, heat and humidity. The temperature change from a summers day at ground level in England to that at 40,000 ft is about 60C. In the radiator area the temperature on a winters day could change from minus 20C to plus 100C in minutes. The airframe of any mosquito anywhere in temperate England survived massive temperature and humidity variation yet everyone discusses the humidity in the far east.
You control the corrosion on Harrier ops by building a Sea Harrier.
MERELY compensating for cooling drag is HUGE. For piston aircraft of just about any size, type, and performance class, cooling drag represents 30% to 40% of total airframe drag. Their's a lot more drag inside that little scoop than its frontal area would make you think. Cancel that with Meredith thrust, and you should more than compensate for a laminar wing that doesn't live up to its wind tunnel promise under field conditions.[/QUOTE]
Maybe a bad choice of words, not saying it wasnt important just that the P51 didnt have a secret rocket pushing it along.
FLYBOYJ
"THE GREAT GAZOO"
Those temperature variations you talk about are seasonal - what is the aircraft being exposed to when it rests at the end of the day? What is the AVERAGE ambient temperatures and humidity it will see?
The link I posted proves my point and I know the RAAF wasn't the only post war operator who had maintenance issues with the Mosquitoes that eventually led to its retirement. Again, I've worked with wood aircraft and seen these issues - if you have information experience that proves me wrong, I'm all ears!
"Its wood construction provided it's greatest strength during the war, but was also its Achilles' heel. While metal aircraft endured after the war, Mosquitos rotted away, between the wood decomposing and the loss of adhesion of the animal-based glues that held the plywood together, few Mosquitos survived long and very few remained airworthy to display on the air show circuits of the world, which caused the plane to fall to an undeserved level of obscurity."
Airworthy de Havilland Mosquito Restoration Approaches Completion in Canada
Ok - now we're talking metal planes...
I could tell you that structurally both aircraft are about the same, some dissimilar metal parts were changed to avoid bimetallic corrosion, the Sea Harrier uses different corrosion coatings and inhibitors, but these are EXTERNAL treatments and little to do with this discussion.
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Good info FBJ, my point is, the fact that the Mosquito is an aeroplane going from ground level to 40,000 ft in summer and winter is what makes the structure vulnerable. Talk of mildew in the far east being a problem makes me laugh, as if a plane parked outside in the UK wouldnt get mildew. If water is allowed to get into the wood it will fall apart very quickly I would think, because it will freeze at altitude. Its the thing about humidity in the far east being a particular and chronic problem that I disagree with.
FBJ post number 37 was not made by me
FLYBOYJ
"THE GREAT GAZOO"
Mildew will build up if you have no air movement around the wood structure. Around 71F with 30% humidity is the perfect environment for dry rot.
I'm trying to figure that one out.
