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Good Mosquito Restoration Article

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Good Mosquito Restoration Article

Old 7th Jan 2022, 18:21
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Originally Posted by 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)

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"
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Old 7th Jan 2022, 18:36
  #22 (permalink)  
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Originally Posted by GeeRam
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.
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Old 7th Jan 2022, 20:00
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Originally Posted by Self loading bear
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.
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Old 8th Jan 2022, 03:37
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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.

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Old 8th Jan 2022, 08:28
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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

Last edited by gimbal error; 8th Jan 2022 at 22:32.
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Old 8th Jan 2022, 15:41
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Brief article about the wartime production of plywood in the Forest of Dean. Spot the deliberate mistake…
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Old 8th Jan 2022, 17:08
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Originally Posted by Rory57

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.
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Old 8th Jan 2022, 18:35
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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.

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Old 9th Jan 2022, 07:08
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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.
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Old 9th Jan 2022, 08:11
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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.
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Old 9th Jan 2022, 12:02
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Originally Posted by 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.

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.
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