Good Mosquito Restoration Article

[tdracer]

The Jan/Feb 2022 issue of Popular Mechanics has a really fascinating article on the flight worthy restoration of a WWII vintage Mosquito.
It's also available on-line but is behind a paywall (which I can't seem to get past even though I subscribe to the dead tree version)
How I Restored a Legendary Wooden WWII Fighter Plane (popularmechanics.com) (https://www.popularmechanics.com/military/aviation/a37156438/restoring-wwii-mosquito-plane/)

I was particularly interested in the construction of the fuselage - 1/2" thick balsa sandwiched between two layers of 1/16 spruce plywood. Made me wonder how they sourced all that balsa during the war.

[sycamore]

Got it from the model shops....

[MAINJAFAD]

The Jan/Feb 2022 issue of Popular Mechanics has a really fascinating article on the flight worthy restoration of a WWII vintage Mosquito.
It's also available on-line but is behind a paywall (which I can't seem to get past even though I subscribe to the dead tree version)
How I Restored a Legendary Wooden WWII Fighter Plane (popularmechanics.com) (https://www.popularmechanics.com/military/aviation/a37156438/restoring-wwii-mosquito-plane/)

I was particularly interested in the construction of the fuselage - 1/2" thick balsa sandwiched between two layers of 1/16 spruce plywood. Made me wonder how they sourced all that balsa during the war.

From Ecuador mostly, plus most of the other wood used came from the Americas as well (Yellow Birch, Spruce and Douglas Fir). The only UK sourced wood used was Ash and Silver Birch for some parts of the aircraft.

[Chu Chu]

From Ecuador mostly, plus most of the other wood used came from the Americas as well (Yellow Birch, Spruce and Douglas Fir). The only UK sourced wood used was Ash and Silver Birch for some parts of the aircraft.

I imagine balsa was popular cargo, if you had to cross the Atlantic with it.

[treadigraph]

The late Glyn Powell - we DH fans owe him rather a lot! And when the Hornet is finished, can it please visit England?

[Herod]

One interesting fact is that balsa is actually classed as a hardwood. It's all to do with the cell structure.

[tartare]

As a reporter, I did two TV stories with Glyn on his original rebuild.
Not sure about the sourcing of the wood, but he told me some of the production of the Mosquito was outsourced to English furniture factories during the war.
He said they had to work to watchmaking tolerances in wood.
Lofting of complex curves and radii - all done by hand on paper - he said recreating it from the DH documents he was able to get copies of was an enormous task.
Concrete moulds were used to cast the steamed plywood/balsa sandwich fuselage halves, which were then glued together and covered in doped canvas.
I remember being struck by how thin the fuselage cross section was where it joined the empennage.
Beautiful aircraft.
https://www.youtube.com/watch?v=m81wEm1q824

[NutLoose]

They used concrete moulds because they were stable, two halves of the aircraft were built and fitted out then joined down the middle, there is a surviving Sea Hornet mould at the Mossie museum. Which was basically a single seat Mossie design wise.


https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/2000x1504/img_2410_cb4c2219265e6c747de71ea74f734928d1edfe58.jpg

[NutLoose]

You will find this interesting, it is Glen Powell the late father of the new Mosquito who built a set of wooden moulds. It shows the build process.

https://www.aussiemossie.asn.au/index_files/Page1052.htm

[Hydromet]

... but he told me some of the production of the Mosquito was outsourced to English furniture factories during the war.
He said they had to work to watchmaking tolerances in wood.
Lofting of complex curves and radii - all done by hand on paper - he said recreating it from the DH documents he was able to get copies of was an enormous task.

And after the war, English furniture designers and manufacturers used what they had learned to make whole new styles of furniture. They had the techniques down pat.

Interested in the structure of the fuselage. I looked at building a sailing boat which used a similar technique, except that the skins were fibreglass rather than wood veneer. However, the balsa was laid perpendicular to the outer veneers, ie, the grain ran from inside to out, rather than across, at right angles, to the skins. I couldn't see the structural advantage of doing it that way, and I've never seen it done that way anywhere else.

[Big Pistons Forever]

I would suggest that this airplane is not a “restoration” it is a re- creation. The only flying Mosquito that was restored is the Canadian F for Freddie. Almost all of the wood is original restored and repaired to airworthy condition along with the engines and mechanical bits.

A few lumps of metal from a wreck added to a totally new primary structure is not an original airplane. That being said the build quality is magnificent and the aviation world is better for having examples of such rare but important airplanes like the Mosquito.

[tdracer]

I would suggest that this airplane is not a “restoration” it is a re- creation. The only flying Mosquito that was restored is the Canadian F for Freddie. Almost all of the wood is original restored and repaired to airworthy condition along with the engines and mechanical bits.

While all the wood construction is new (apparently the issue isn't just rot, it's that the glue fails with age), most of the rest is original Mosquito parts (although from multiple aircraft). But point taken. It is a pretty soft line between 'restoration' and 'recreation' - there are a lot of 'restoration' WWII aircraft where precious little of the skin and structure are original.

I imagine balsa was popular cargo, if you had to cross the Atlantic with it.
Good point - probably one of the favorite cargos.

There has been something of a shortage of good quality balsa for model aircraft and rockets the last few years. Apparently large amounts of balsa is being used to form the cores of all those wind turbine blades. I would have thought some synthetic foam would be used but apparently balsa works better and/or is cheaper.

[GeeRam]

I would suggest that this airplane is not a “restoration” it is a re- creation. The only flying Mosquito that was restored is the Canadian F for Freddie. Almost all of the wood is original restored and repaired to airworthy condition along with the engines and mechanical bits.

A few lumps of metal from a wreck added to a totally new primary structure is not an original airplane. That being said the build quality is magnificent and the aviation world is better for having examples of such rare but important airplanes like the Mosquito.

Well, the Bob Jens B.35 is hardly a flyer, having flown only 2 or 3 times after it's restoration was finished, and has remained grounded ever since, with no intention of flying it again.
Given the information available from all the NDT survey's done on RR299 while it was operated by BAe, there is probably a good reason for this, especially with regard to the glue situation...certainly, from what I've gathered. The same holds for the Kermit Weeks example, which hasn't flown now for 30 years, and reports are there are some delamination issues visible, and would likely need an all new build wood structure for that to ever fly again.

Probably half of the Spitfires flying are 'all new build structure'......they are still Spitfires though.

[steamchicken]

It's possibly not widely appreciated that plywood itself was a new technology back then - there was a three-way race between British, German, and Scandinavian producers to get it right. You could even see the Mossie as the first aircraft to be built with composite materials - the combination of the different woods and the Aerolite glue, really a thermosetting plastic, especially when you remember that some of them were thermoset using RF energy like a big microwave oven.

Not a throwback to biplanes as everyone assumed (to be fair the British government's wartime propaganda helped push that idea) but a throwforward to the era of composite-built multi-role fighter/strike aircraft, especially as it was such an important electronic warfare platform.

[GeeRam]

It's possibly not widely appreciated that plywood itself was a new technology back then - there was a three-way race between British, German, and Scandinavian producers to get it right. You could even see the Mossie as the first aircraft to be built with composite materials - the combination of the different woods and the Aerolite glue, really a thermosetting plastic, especially when you remember that some of them were thermoset using RF energy like a big microwave oven.

Not a throwback to biplanes as everyone assumed (to be fair the British government's wartime propaganda helped push that idea) but a throwforward to the era of composite-built multi-role fighter/strike aircraft, especially as it was such an important electronic warfare platform.

Indeed.
The Mosquito was indeed the first composite construction, LO multi-role combat aircraft.

[pax britanica]

My grand parents lived at Croxley Green in Herts and I used to spend quite bit of the summer with them in the early 60s ,not sure exactly which year, and was privileged to see a whole gaggle of Mosquitos fly over just north of us and failry low ( One of the LHR SIDS which they didnt have back then butt he routing was much the same , passed over the Watford area ) on their way back to Bovingdon where much of 633 squadron was filmed . This went one for a week or more, a wonderful sight and even more wonderful sound !! .

I have never seen a Mossie flying since then and perhaps never will but always thought it was a wonderful aircraft a sort of 1940s Tornado /F 18 multi role concept jack or all trades and pretty much master of them too. I suppose their rarity is due to the fact they longevity doesn't matter much in war time and the potential structural issues didn't matter as the aircraft wasnt going to be around for the life times of todays military aircraft. Also as far as I know from reading they didnt exactly have benign handling characteristics with an engine out and if you were unlucky and this happened at critical points on take off , approach or go around you were dead. So flyting aircraft that are in part 75 years seems quite high risk business just to show off an admittedly wonderful aircraft.

[Herod]

If you are anywhere near London, I can recommend the D.H. Museum. I was there a couple of months ago, and was most impressed. Quite an experience to stand in a hangar with three Mosquitoes.

[Fargo Boyle]

There are 2 current projects to restore and fly Mosquitos in the UK

Newsletter Signup - The People's Mosquito (peoplesmosquito.org.uk) (https://www.peoplesmosquito.org.uk/)

The Mosquito Pathfinder Trust - news (thewoodenwonder.org.uk) (https://thewoodenwonder.org.uk/)

Hopefully at least one of them will be successful. In a few years we could have an airshow with a Typhoon, Tempest and Mosquito!

[Self loading bear]

Interested in the structure of the fuselage. I looked at building a sailing boat which used a similar technique, except that the skins were fibreglass rather than wood veneer. However, the balsa was laid perpendicular to the outer veneers, ie, the grain ran from inside to out, rather than across, at right angles, to the skins. I couldn't see the structural advantage of doing it that way, and I've never seen it done that way anywhere else.

The balsa core does not add strength it keeps the outer and inner plywood or fiberglass at a fixed distance.
Same as the web of a H-beam keeps the lower and upper flange apart.
If you would replace the web by a massive fill with balsa it would be lighter but with same strength.
Putting the grain perpendicular to the outer layers makes the core more difficult to compress (dents) and the sheets of balsa can be more easily plied in the mould. And glue can penetrate into the pores reducing possible delamination.

[GeeRam]

There are 2 current projects to restore and fly Mosquitos in the UK

Newsletter Signup - The People's Mosquito (peoplesmosquito.org.uk) (https://www.peoplesmosquito.org.uk/)

The Mosquito Pathfinder Trust - news (thewoodenwonder.org.uk) (https://thewoodenwonder.org.uk/)

Hopefully at least one of them will be successful. In a few years we could have an airshow with a Typhoon, Tempest and Mosquito!

The Pathfinder Group is the most advanced, or at least likely has the most chance of coming to fruition, as they struck a deal to acquire Glyn Powell's Aussie built project, so gained a lot of parts Glyn had collected, including a lot of, if not most of the metal parts, which is a surprising amount.

It was a shame that having two competing groups couldn't combine resources to just one to stand a better chance of getting one flying here, but ego's got in the way as usual.

Its highly possible, that at some point in the near future the FHC/Paul Allen T.3 that was restored to fly by Avspecs (and used to hang up in the IWM Lambeth) will be sold when Paul Allen's sister starts to liquidate the airworthy contents of FHC at some point in the future...once they have sold all of the unfinished projects that are currently being sold off.
You'll need deep pockets though.

[JagRigger]

The Jan/Feb 2022 issue of Popular Mechanics has a really fascinating article on the flight worthy restoration of a WWII vintage Mosquito.
It's also available on-line but is behind a paywall (which I can't seem to get past even though I subscribe to the dead tree version)
How I Restored a Legendary Wooden WWII Fighter Plane (popularmechanics.com) (https://www.popularmechanics.com/military/aviation/a37156438/restoring-wwii-mosquito-plane/)

I was particularly interested in the construction of the fuselage - 1/2" thick balsa sandwiched between two layers of 1/16 spruce plywood. Made me wonder how they sourced all that balsa during the war.

I once had reason to source some balsa to reline the collector tank bay on a Jaguar from a fairly local supplier to Coltishall ( Watton actually ) Walked in and said I need 1/2" planks x however many metres it was.
Q: " crikey what are you building ? "
A; " A Jaguar "
Q " what scale ?"
A " oh 1:1" ;)

[tdracer]

Its highly possible, that at some point in the near future the FHC/Paul Allen T.3 that was restored to fly by Avspecs (and used to hang up in the IWM Lambeth) will be sold when Paul Allen's sister starts to liquidate the airworthy contents of FHC at some point in the future...once they have sold all of the unfinished projects that are currently being sold off.
You'll need deep pockets though.

In all fairness, I'm really hoping Allen's sister doesn't break up the Flying Heritage collection. I live just a few miles from there, and it's an outstanding aviation and combat armor museum. My understanding is that admission fees were covering the operating expenses (at least pre-COVID) so it doesn't really cost anything to keep that fantastic collection together. Unfinished projects - OK, you need someone with a lot of determination to see those through, but the existing displays don't take much effort to maintain.

[Hydromet]

The balsa core does not add strength it keeps the outer and inner plywood or fiberglass at a fixed distance.
Same as the web of a H-beam keeps the lower and upper flange apart.
If you would replace the web by a massive fill with balsa it would be lighter but with same strength.
Putting the grain perpendicular to the outer layers makes the core more difficult to compress (dents) and the sheets of balsa can be more easily plied in the mould. And glue can penetrate into the pores reducing possible delamination.
Thanks SLB, that makes sense. Thinking about it later, I wondered whether it was about achieving better glue penetration through the end grain.

[megan]

Fuselages were of plywood construction, two layers of thin plywood strips were placed over a mold to form one half of a fuselage shell. The fuselage halves were then glued together, covered with a layer of fabric, and doped. Sounds just like the Mosquito, but no, this was 1915. The process was a patented invention of the Luft-Fahrzeug-Gesellschaft company which used the process on its Roland C.II, photo below. The German Pflaz fighters of WWI used the same construction method under license.

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1920x1253/lfg_roland_cii_4_37e75398f239aa67e31429adb90bc7542caafd69.jp g

[gimbal error]

The plywood moulding method was invented and used by German aircraft manufacturers as early as 1915 indeed. I doubt that they used balsawood as sandwich filler. There is a subtle but important difference to the Mossie construction technique however.

The Germans simply patched thin veneer onto a mold which bends nicely onto the curved contours. When it comes to plywood which itself is made of numerous veneer layers things become complicated. Plywood doesn't bend as nicely as veneer does. Bending it onto a compound surface is a challenge. Steam treatement helps to a certain degree but has its limits. Therefore the surface needs to be cut into numerous patches which can take the bending. This results in gigantic puzzle. To make things even more complicated the joints of every puzzle piece must be scarved at an exact angle to offer sufficient glueing surface. An enormous amount of work.

I pull my hat for the Mossie team.

Here's another project which faces similar challenges
www.projekt-arbalete.ch

[Rory57]

https://www.pressreader.com/uk/gloucestershire-echo/20210923/281973200797355

Brief article about the wartime production of plywood in the Forest of Dean. Spot the deliberate mistake…

[Allan Lupton]

https://www.pressreader.com/uk/gloucestershire-echo/20210923/281973200797355

Brief article about the wartime production of plywood in the Forest of Dean. Spot the deliberate mistake…
Lots of things one could take exception to but the idea of 125,000 Mosquitoes takes some swallowing!
The idea that the plywood for all of 'em (even for the corrected number of (I think) 7,761) came from Lydney is highly unlikely since the Canadian- and Australian-built examples would have used locally made plywood.

[megan]

The original I snapped a couple of years ago ge. I wasn't so much referring to the balsa/ply sandwich, but the molding over a former and joining the two halves, de Havilland merely introduced an innovation by separating the ply layers with balsa.


https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/2000x1504/norway_trip_036_ebfbdcceaa49c4b247ab535e85cf4cc19e8f04b9.jpg
https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/2000x1504/norway_trip_037_e1839a8618c3b71e322a8949b4369020e34645b0.jpg

[tramontana]

No doubt that the Mosquito was an amazing aircraft both in its construction and the many roles it took on which it was not initially designed for, the glue problem became evident early on when the aircraft where flown to warmer climates along with the speedier deterioration of rubber components, I have seen a photograph of glue stricken Mosquitoes at an MU in Egypt placed in a circle (tails inward) where the Merlins and Engine Bearers had been previously chopped out with an axe, their fuel tanks chopped open and a Flare fired into them making a huge bonfire.
Post bonfire the locals would move in and recover any metal lying around.
In regards to the furniture manufacturers involvement the method of construction certainly went into Post War furniture construction especially when it came to dining tables and sideboards.
When I married around 60years ago and was putting a home together there was a number of choices when it came to furniture ranging from cheaper second hand Wartime utility with the unforgettable mark stamped on the "Orange boxwood" to the very expensive virgin wood G Plan whose tables and sideboards warped badly when they sniffed out any heat, in the middle was a make called Lebus which benefited from the experience of constructing Mosquitoes halves using plywood and along with a highly varnished finish made decent looking tables and sideboards which did not warp at all and were of course a bit cheaper than GPlan.

[blind pew]

My 17m 1967 Phoebus C had balsa cored epoxy sandwiched GRP wings. Built by one of the ATAFLIEGS..iirc Stuttgart. Gave it an interesting polar as wing had a marker lower under camber profile which meant that at low speeds it was in laminar whilst upper wasn’t and high speeds vice-versa.
Some bright spark suggested that I took core samples to check for rot .obviously didn’t understand the implications of the hardwood nor its purpose in the construction.
My father built MTBs in the war and in the 60s commissioned a high speed hull mould ..both used formers with triple veneers glued to form the complex curves.
I designed a caravan using end grain balsa sheets for the infilling but there was a problem with adhesion using polyester resins during the moulding process…our competitors..Eric Birch,who moulded Prout catamarans for a while and made Jaguar yachts, went over to a special foam with appropriate glues which cured the problem 20 years later. Apologies for the pun.

[tramontana]

My grand parents lived at Croxley Green in Herts and I used to spend quite bit of the summer with them in the early 60s ,not sure exactly which year, and was privileged to see a whole gaggle of Mosquitos fly over just north of us and failry low ( One of the LHR SIDS which they didnt have back then butt he routing was much the same , passed over the Watford area ) on their way back to Bovingdon where much of 633 squadron was filmed . This went one for a week or more, a wonderful sight and even more wonderful sound !! .

I have never seen a Mossie flying since then and perhaps never will but always thought it was a wonderful aircraft a sort of 1940s Tornado /F 18 multi role concept jack or all trades and pretty much master of them too. I suppose their rarity is due to the fact they longevity doesn't matter much in war time and the potential structural issues didn't matter as the aircraft wasnt going to be around for the life times of todays military aircraft. Also as far as I know from reading they didnt exactly have benign handling characteristics with an engine out and if you were unlucky and this happened at critical points on take off , approach or go around you were dead. So flyting aircraft that are in part 75 years seems quite high risk business just to show off an admittedly wonderful aircraft.


The Mosquito had a number of other issues besides delamination and Glue problems it was indeed difficult to fly if one of these issues cropped up inflight especially those learning at OTU's, looking at 13(not a good number) OTU based at what is now Teesside Airport just after War ended the accident rate is quite high (mind you not as high as flying the Meteor out of the same Airfield), an earlier accident with a Mosquito is highlighted in the Graveyard at the little Church to the South of the Airfield Perimeter Fence where a F/L lies buried, the Son of the local Coalmerchant but Instructing in Canada at the time flew his Mosquito into one of the few clouds and the tail snapped off.