Merlin 16 decks

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chris
Posts: 2474
Joined: Sat Sep 18, 2004 7:43 pm
Location: somerset

Merlin 16 decks

Post by chris »

I've at last been able to do a bit more work on Gently, Merlin 16 which was Jack Holt's own boat. So a bit of an update:

The stripping is done mostly and have taken the ply decks off. These will be returned to the boat and not renewed. It was known that he used ply surplus to the building of Mosquito aircraft in the war. It is 3/32" thick - that's 2.5mm and has hardly dergraded at all but there are a few bits of damage to repair, in particular where a hole was cut to convert from deck stepped to hog steped mast. The rig will be returned to a rotating deck stepped mast .
I gather the birch for the ply was sourced from Canada but the stamp is not too legible now. The numbers written in pencil also appear beside another similar stamp elsewhere.

Because of the incompatible top layer of varnish great tigerlike stripes opened up in the varnish and the ply is deeply stained. One picture shows a 'before and after'. The 'after' panel has been treated with oxalic and also a peroxide wood bleach. These marked have been improved but are still visible. I will try some chlorine bleach next but I do not expect them to disappear. It is part of the patina now.

The last picture is the rotating mast step which is from another merlin. The step had had two blocks brazed to it to stop rotation. It wasn't difficult to remove these and clean the bronze up. Note a no. 2 stamped on it. Was this originally for Merlin 2 I wonder
ply 5.JPG
(25.33 KiB) Not downloaded yet
stamp.JPG
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step2.JPG
(17.92 KiB) Not downloaded yet
Rupert
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Joined: Thu Sep 16, 2004 8:40 pm
Location: Cotswold Water Park

Re: Merlin 16 decks

Post by Rupert »

Fascinating project Chris - looking forward to seeing her.
Rupert
billytwiglet
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Joined: Sun Jan 10, 2010 5:56 pm

Re: Merlin 16 decks

Post by billytwiglet »

Chris,

James Latham sell (finnish) birch ply often referred to as aero ply:-

http://www.lathamtimber.co.uk/images/Pr ... /Panel.pdf
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chris
Posts: 2474
Joined: Sat Sep 18, 2004 7:43 pm
Location: somerset

Re: Merlin 16 decks

Post by chris »

There's a place near Bristol too but the whole point is to keep the original and its history. Not only is it war surplus, which modern ply obviously isn't but it also has some scribbled scetches on the back by Jack Holt working out how the get the pieces he needed from the panels he had. It's also a case of "Jack Holt sat'ere"!
Mungo
Posts: 133
Joined: Thu Oct 22, 2009 2:45 am
Location: Canada

Re: Merlin 16 decks

Post by Mungo »

That's interesting ply. Built from diagonal veneers much like a hull? It must have been a well treated boat for birch to last that long (at all). Why birch? surely at that time Canada had a lot of good trees to pillage. I would imagine big cedar sitka spruce and the like was available (maybe wrong side of the continent).

Can you explain how you get decks off without damaging them? Surely glued down. How do you manage to get them up? I regret some of the things I have done due to not being able to break the glue bond between certain delicate parts.

cool project .
chris
Posts: 2474
Joined: Sat Sep 18, 2004 7:43 pm
Location: somerset

Re: Merlin 16 decks

Post by chris »

This birch ply was originally used to build the Mosquito aircraft in the war. It was an all- (well mostly) wooden aircraft and I think the fuselarge was made using a double skin sandwich construction. I imagine the shortage of suitable metal in war was the main reason for designing a wooden bomber. It was a very successfull machine, over 7,000built. By coincidence my Uncle ran a plywood firm called Borst Bros near Hatfield during and after the war and was also involved with supplying plywood to de Havilands too. Sadly I never asked him to tell me about that and he died many years ago. It even possible the birch was imported just as veneer but I was told it wasn't. http://www.fleetairarmarchive.net/aircraft/mosquito.htm will tell you about the aicraft and has a good picture of a fuselarge being built.

The plywood differs from modern ply in that the veneer it is made from is not rotary cut, which produces sheets miles long (like peeling an apple) and shows an odd looking grain. The old method was simply to take slices through a log so none of the veneers are more than 12-14inches wide. Birch is soft to cut and close grained whereas spruce would not be so easy for this.
I would like to know what adhesive was used to bond it as it has not dergraded at all but I think the black stripes that are visible may partly be due to water reacting with the chemicals of the adhesive that penetrated the wood.
Yes the the ply has been cut to be diagonal, even on the rolled side decks unlike Iska Merlin 6 where it is all straight. Both Built by Jack Holt in the same year but Gently he built for himself so added that special touch.

Apart from the glue within the plywood itself the whole boat is nailed, screwed or riveted together - no glue anywhere. This was 1946 and still the era of traditional methods. So it was painstaking to get all the screws and copper nails out of the decks but then you just lift them off. Many of the nails had started to lift and were easy to remove without damaging the ply, most of the brass screws had corroded and broke though. The only difficult place was on the top of the transom and I chopped through the soft copper by slipping a strong thin knife between the ply and the mahogany and tapping the back of the blade with a hammer. It cuts easily and the heads fall out - OK it leaves the rest of the nail in the transom to sort out later.

I'll put some more pictures up later as I progress.
jonathan
Posts: 178
Joined: Mon Sep 27, 2004 10:12 pm

Re: Merlin 16 decks

Post by jonathan »

Chris, don't be too original in choice of glue as the Mosquito suffered glue failure when used in the Far East theatre. Heat and humidity caused failure either through decomposition or microbe attack! Not that the UK climate has quite warmed up to Far East levels but one never knows what is in store.
chris
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Joined: Sat Sep 18, 2004 7:43 pm
Location: somerset

Re: Merlin 16 decks

Post by chris »

Hallo Jonathan. Indeed you are right. Apparently some of the wooden props that were used on aircraft failed from glue problems and they sent them off for analysis. The question came back " why have you glued them with cheese?" Some glues like cascamite are made from casein which is a milk derivative and it degraded back to something like cheese! I found a website from Australia where someone is building a replica Mosquito just about from scratch. Some very good pictures of the work in progress. Makes rebuilding a small dinghy look a piece of (cheese) cake!
mole
Posts: 47
Joined: Tue Sep 06, 2011 6:36 pm

Re: Merlin 16 decks

Post by mole »

Hi
Aerolite was specifically developed to build the Mosquito, but not to bond the ply veneers.
Aerolite, as I am sure you know was used in Mirror kits. Personally I prefer the modern epoxy adhesives.

Mole
never knowingly undersailed
chris
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Joined: Sat Sep 18, 2004 7:43 pm
Location: somerset

Re: Merlin 16 decks

Post by chris »

I quite agree about epoxy vs. any other marine glue, Of the old glues cascamite has the worst problems.
Mungo
Posts: 133
Joined: Thu Oct 22, 2009 2:45 am
Location: Canada

Re: Merlin 16 decks

Post by Mungo »

completely off topic.... but wood, mosquitos, should be under banter I guess.

Had an uncle that flew hurricanes and then mosquitos. All I have is a pic of him (quite a dashing very young man) and hurricane with the letters SDM. On the back "1939-1941 France/croydon/middle wallop". It left hard scars on him and he wouldn't even talk about it. I realize planes likely changed hands but there must be something there that would give me some leads to dig deeper. Any RAF knowledgeable people in CVRDA?.

He once took me up the houses of parliament tower to see the guts of Big Ben and a workman gave me a penny that he took off a pendulum. I remember him telling me it was used to calibrate the time (this all sounds extremely unlikely, I was pretty young, but I still have the penny and I like my memories...).
Bill-Conner
Posts: 126
Joined: Thu Sep 02, 2010 3:08 pm

Re: Merlin 16 decks

Post by Bill-Conner »

Off topic only to answer Mungo! The RAF Museum at Hendon wil be able to help and very helpful they are too!
Do you have his logbooks every pilot has them to this day.
BTW the RAF Museum also has a few Uffa Fox airborne lifeboats including a very larg aluminium one one of the wooden ones is on display even.
Michael Brigg
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Joined: Fri Jul 06, 2007 7:11 pm
Location: Gosport, UK

Re: Merlin 16 decks

Post by Michael Brigg »

Mungo wrote:
He once took me up the houses of parliament tower to see the guts of Big Ben and a workman gave me a penny that he took off a pendulum. I remember him telling me it was used to calibrate the time (this all sounds extremely unlikely, I was pretty young, but I still have the penny and I like my memories...).
The pennies are entirely correct,

See this...

http://www.last-word.com/content_handli ... /2057.html
Michael Brigg
Mungo
Posts: 133
Joined: Thu Oct 22, 2009 2:45 am
Location: Canada

Re: Merlin 16 decks

Post by Mungo »

Thank you all

I have had several replies by PM and I will dig around. I will treasure my penny.

maybe those who run the forum can delete the posts so they don't clog up the system

thanks again
Pat
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Re: Merlin 16 decks

Post by Pat »

More off topic but I used to live next door to Middle Wallop airfield (flying side -best viewpoint for an airshow) and they have the Museum of Army Flying there who may be able to give you more information. It's on the A343 between Andover and Salisbury and a pleasant day out if you like planes.
(Half Cut and What a Lark Removals Ltd)
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