Author Topic: Nash, Karnak, DH Mosquito stuff  (Read 2281 times)

Offline Replicant

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Nash, Karnak, DH Mosquito stuff
« on: September 08, 2001, 03:00:00 PM »
Hi

I was fortunate to visit the RAF Museum at Hendon today and took a few pics of the Molins cannon on display there -  http://www.btinternet.com/~nexx/Molins1.jpg  &  http://www.btinternet.com/~nexx/Molins2.jpg .

   

I also visited the De Havilland Heritage Museum which is situated at London Colney near to the Hatfield plant, north of London.  The museum is the actual place where the prototypes were completed and flown, seperate to the main Hatfield plant mostly because of the concerns of Hatfield being bombed.  The buildings still remain, and even the Mosquito prototype is there -   http://www.btinternet.com/~nexx/Mosquito-prototype.jpg  

Well, this museum turned out to be something extra special because they had a Mosquito B35 'TA634' (built 1945) there and whilst trying to take a photo inside the hatch entrance underneath, the DH technician said I could climb up inside the cockpit!  He didn't have to offer it a second time and I was up there like a flash!  All I can say is that there is a lot more room than I ever imagined and it shows the WB2 Mossie view is truly inaccurate - the view around from the cockpit is exceptionally good, and even the pilot seat armour is only minimal making over shoulder looks easy too.  Although this is the bomber version, I can't imagine that the FB version being all that different.  Here are two photos I took from the navigators seat (big pics) -  http://www.btinternet.com/~nexx/Mosquito-cockpit1.jpg  &  http://www.btinternet.com/~nexx/Mosquito-cockpit2.jpg .  Perhaps we'll get the Bomber version too?

Oh, another thing was the flame arresters that were put over the exhausts as in 'Black Rufe'.  Although at the time the technical manual expected a loss in speed, I asked the DH Technician about this and he actually said that it wasn't found until after the war that the flame arrester tubes actually caused a jet like effect and could boost speed by up to 20mph!  It seems hard to believe but I wasn't going to argue with a DH technician who has been working for DH for 40 odd years!    :)

I also copied some information about Geoffrey de Havilland and R.E. Bishop:-

Geoffrey de Havilland

Geoffrey de Havilland was born on the 27th of July 1882 in a village near High Wycome. After his formal education, he attended the Crystal Palace School of Engineering. On completing his course he joined Willans and Robinson, a firm of steam engine engineers, as a student apprentice. He later left Willans and Robinson to take up a position at the Wolsely Tool and Motor Car Company. After one year, he moved on to a more interesting job; that of designer for Motor Omnibus Construction Company. It was during his time in this profession that he developed, in his own words, “an overwhelming desire to fly.”

In 1908, with financial support from his grandfather, de Havilland left paid employment and started to build his first plane. This attempt was unsuccessful; due to de Havilland’s complete lack of flying experience, the plane crashed. Undeterred, de Havilland started work on a second plane, which had its first flight on the 10th of September 1910. The design for this plane was purchased by the Government Balloon Factory (later renamed the Royal Aircraft Establishment), which also took de Havilland on as a pilot and designer. This position was later changed so that there was less design work involved, which led to de Havilland joining the Aircraft Manufacturing Company, the company which built his designs from 1914 to 1920, when the De Havilland Air Company was formed.

In 1909 de Havilland married Louie Thomas, and together they had three sons, though tragically two were killed in aviation accidents; Paul in 1942 in an airborne collision between two de Havilland Mosquitos, and Geoffrey (jnr) in 1946, while flight testing. Louie also passed away in 1946, and in 1951 de Havilland was remarried, this time to Joan Mordaunt, who shared his passion for natural history. In 1944 de Havilland received a knighthood, and membership to the order of merit was conferred upon him in 1962. He died on the 26th of May1965.

R. E. Bishop

When the Air Ministry requested designs for a new general purpose bomber, the last thing they envisaged was a wooden aircraft. De Havilland put forward designs for a 2-seat, twin-engined bomber with the capabilities of a fighter and the armament of a small bomber. In early 1940, the chief designer R. E. Bishop began work on the prototype. He had joined the De Havilland Air Company in 1921 as an apprentice, and had risen to the position of Design Director. 11 months after the initial design process, the all-yellow prototype (W4050) with twin Merlin engines, flown by Geoffrey de Havilland Jnr., took to the skies. The Mosquito, as it was known, was an immediate success. Trials at A&AEE Boscombe Down followed, and on the 15th of November 1941 the first Mosquito bomber joined 105 Squadron. Throughout World War 2 the Mosquito lived up to all expectations, creating havoc and mayhem whenever it was used in attacks on the enemy. Its contribution to the 1939-1945 conflict is now legendary.

Anyway, hope you enjoyed the pics!  

Regards

Nexx

[ 09-08-2001: Message edited by: Replicant ]
NEXX

Offline snafu

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« Reply #1 on: September 08, 2001, 05:16:00 PM »
Wow Nexx, You got to sit in a real mossie you jammy B, BTW nice post  :)

TTFN
snafu

Offline Karnak

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« Reply #2 on: September 08, 2001, 05:37:00 PM »
Great info.  Nice cockpit shots.

I'd love to find more on the effects of the flame damping equipment on speed. I was going on Nashwan's post and one of my books that states that there is a 14mph loss due to the equipment.

Thanks for the shots and info.  :D
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Offline Replicant

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« Reply #3 on: September 08, 2001, 06:13:00 PM »
Quote
Originally posted by snafu:
Wow Nexx, You got to sit in a real mossie you jammy B, BTW nice post   :)

TTFN
snafu

Well I couldn't believe how lucky I was either!  I was only supposed to go to the top of the ladder but I didn't realise that afterwards!  Ramjet was with me too and he was allowed in the Mosquito too.  You really should visit this museum as they allow you to sit inside a DH Venom, Sea Venom, and Sea Vixen too, as well as look inside some other aircraft.  My girlfriend Sarah enjoyed herself sitting in the Sea Vixen, and I didn't realise that there is actually a navigator position, but he has no canopy!  He sits slightly lower and just has a little window on the starboard side!   :)  http://www.btinternet.com/~nexx/Sarah-SeaVixen.jpg  

BTW  The Mosquito B35 is almost complete and within a few years should be fully airworthy but they doubt that they'll ever fly it incase they lose it!  With it being wood means that hardly anything would be left if it ever crashed!  The same Mossie is being used for a Channel 4 programme about the 'Oboe' system that was used in WW2.  Check your TV in the future!

Regards

Nexx
NEXX

Offline Nashwan

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« Reply #4 on: September 08, 2001, 07:00:00 PM »
I've read there was a speed loss with the ducted saxophone exhausts in several books, the titles of which escape me at the moment.
I am a little dubious about a speed increase with ducted exhaust. Multi stub ejectors were designed for their jet effect, and some effort seems to have gone into designing them. Spitfire: the History has photos of several different exhaust configs, including ducted ones, and lists several test carried out into their effectiveness. I find it hard to believe they wouldn't have realised that ducted exhausts were speeding planes up by 20mph rather than slowing them down.
Fantastic pics, especially the Mollins.

[ 09-08-2001: Message edited by: Nashwan ]

Offline Replicant

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« Reply #5 on: September 09, 2001, 05:24:00 AM »
Hi Nash

I understand how the ducted exhausts can reduce power output mostly because I learnt all about that when I was doing motor mechanics and engineering.  Basically on a normal exhaust they would have a manifold or direct exhaust pipe which would be designed so that the 'slugs' of exhaust gases didn't interfere with each other.  If they 'interfered' with each other it basically means that the slugs are colliding with other slugs therefore causing a back pressure because the gases cannot escape from the engine as quickly as they should.  By having a ducted exhaust it would mean that the gases would be colliding with eachother if it was simply a exhaust shroud which it appears the Mosquito used.  So, I can see where the loss of power is coming from because quite simply the engine cannot breathe properly - it has to make room for incoming air by dispelling the exhaust gases.

BUT, I don't know aircraft engineering so I can't comment on the DH technician who said that it would cause an increase in speed by producing a jet-effect, which in a way I could believe.  Obviously engine manufacturers have been using manifolds or direct exhausts to help the engine breathing process and all I can guess is that they'd have calculated a loss of Horse Power on an engine test bed and therefore worked out how much speed decrease it might cause.  BUT when actually flying it may have caused an actual increase of speed by causing a jet-pipe effect as the DH techy described.  

I find this hard to believe too, but perhaps at a certain altitude and speed, or most likely RPM, the out going exhaust gases might be escaping at the perfect rate without collisions and only then I could see a possible increase in speed.

Well, I think it makes sense!   :)

Regards

Nexx
NEXX

Offline Replicant

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« Reply #6 on: September 09, 2001, 01:01:00 PM »
Ah, forgot to post this too:-
 

Regards

Nexx
NEXX

Offline Busher

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« Reply #7 on: September 09, 2001, 01:07:00 PM »
Thank you Nexx!!

The Mossie is very dear to the history of our squadron - No. 418 RCAF.

The photos are great.

There is one Mosquito in the National Aerospace Museum in Ottawa Canada. I believe that the Canadian Warplane Heritage in Hamilton Canada would love to have it. They have the only operational Lanc in Canada. I suspect that the cost to restore the Mossie would be prohibitive for a privately sponsored Heritage though.

Thank you again

<S>
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Offline Creamo

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« Reply #8 on: September 09, 2001, 07:34:00 PM »
According to my source, the exhaust shrouds slowed it down 10mph (16km/hr). I can't see how someone could reason a exterior addition to the exhaust pipes could produce thrust. It would be quite a physics lesson indeed.


What was worse was a RDM.2 night camo paint, that slowed the fighter down another 16mph (26km/hr)! so they painted them flat black. Every little thing seemed to effct the aerodynamics of this plane. Even paint, and addition of various guns. (even today, that's exactly why AA has only stripes on the jets. Less drag =fuel savings/speed.)
Initially, they wanted a top turret, but that slowed it way down again. I thought this thing could really haul the mail, but it doesn't seem fast in a late war role at all. I don't care, where are the AI supply ships to blast away at?!

They also mentioned that the flash from the MG's totally destroyed the pilots night vision. Never thought about that.

[ 09-09-2001: Message edited by: Creamo ]

Offline Blue Mako

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« Reply #9 on: September 09, 2001, 09:00:00 PM »
Quote
Originally posted by Replicant:
BUT, I don't know aircraft engineering so I can't comment on the DH technician who said that it would cause an increase in speed by producing a jet-effect, which in a way I could believe.  Obviously engine manufacturers have been using manifolds or direct exhausts to help the engine breathing process and all I can guess is that they'd have calculated a loss of Horse Power on an engine test bed and therefore worked out how much speed decrease it might cause.  BUT when actually flying it may have caused an actual increase of speed by causing a jet-pipe effect as the DH techy described.  
I find this hard to believe too, but perhaps at a certain altitude and speed, or most likely RPM, the out going exhaust gases might be escaping at the perfect rate without collisions and only then I could see a possible increase in speed.

Nexx,

The effect is called exhaust augmentation.  They have used it on many planes (even by design on occasion, see Piper Aztec).  It is very noisy but does give an increase in thrust (only a small overall %age compared to the propeller thrust).  Can't remember the physics well enough to explain it but it works...  It is a different method to a straight jet engine though, I do recall that.

Love the mossie.  Can we get the one with the huge cannon too?  Take out the cv's by strafing 'em...    :D

[edit because I can't spell]

[ 09-09-2001: Message edited by: Blue Mako ]

Offline Grimm

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« Reply #10 on: September 09, 2001, 09:54:00 PM »
I just wanted to toss this out also.  Engine Exhausts can be tuned.  

On Automotive engines, exhaust headers are often used to increase power, everyone knows that one.

Less know is adding short lengths of pipe after the header.  This can Tune the exhaust even more.  The length and diameter can help at specific RPMs.  A well tuned exhaust will create negetive back pressures and add horsepower.

The only reason to mention this, it maybe possible to add something to the system and increase its horsepower.  I dont know if this would apply here. Just something to consider.

As for Mosquitos, Im really excited to fly one again.  

I wish now I had made it to the DeHaviline museum when I was at Hendon last year.  Well maybe someday.  Id have loved to add those to my list of A/C that Iv gotten in.  Iv done well so far.  Iv been in alot of A/C, Everyting from Bocks Car to the SR-71.

Offline Creamo

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« Reply #11 on: September 09, 2001, 10:18:00 PM »
Yeah Grim, noone is arguing tuning exhaust gases for max hp, but what this tech is talking about is putting something OVER the pipes as I understood the question. All that would do is add weight, slow it down a tad, and arrest the flames as intended. (Oh, and my book said they wore out very quickly)

 

[ 09-09-2001: Message edited by: Creamo ]

Offline juzz

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« Reply #12 on: September 09, 2001, 10:32:00 PM »
I have heard that the radiator outlets on the Mossie could produce thrust under "certain conditions".

Offline Creamo

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« Reply #13 on: September 09, 2001, 10:35:00 PM »
Another look at the cowl. HO guns as well.  :)

 

Offline Blue Mako

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« Reply #14 on: September 10, 2001, 12:13:00 AM »
Quote
Originally posted by Creamo:
Yeah Grim, noone is arguing tuning exhaust gases for max hp, but what this tech is talking about is putting something OVER the pipes as I understood the question. All that would do is add weight, slow it down a tad, and arrest the flames as intended.

Read the first paragraph from the link below for a simple explanation of how exhaust augmentation works (It is written about jets but the principle is exactly the same for piston engines).  This effect can work even with a simple cover as fitted to the Mossie shown here.  Won't be as effective as a well designed duct over the exhausts but that doesn't mean it wouldn't work at all...

exhaust augmentation

[ 09-10-2001: Message edited by: Blue Mako ]