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Old Nov 09, 2008, 09:22 PM
a.k.a Maltone
Australia, NSW, Goulburn
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Scratch-Build-Off 3: Avro 555 Bison

Since the build-off 3 start will occur while I am out of the country on holidays (yahoo!), I thought I'd share my deliberations now. The design is about 2 months old and is slowly maturing but a few questions still have to be resolved. Will it qualify for the ugliest model in this build-off? can anybody tell me what the airfoil section might be (Avro, 1923, Roy Chadwick...) why am I entering this stressful comp again etc...

The aircraft is the Avro 555 'Bison' - 1920s carrier-based spotter plane. As a model, 1/12 scale results in a 46" span, 36" long and over 14" high. I hope to use a Park 480 motor turning a 13" wooden prop. A weight of about 32-40 oz should be possible.

The finish is all silver with lots of aluminium panels around the nose and heaps of messy detail (ladders, big windows, Lion W12 engine etc). Red, black or white bands around the fuselage will provide a bit of colour.

After being caught out by a publisher wanting a plan for my Potez 621 from the last comp (plan still not completed) I decided to do it from the start this time and the progress is included here. I'm also drawing a scale 3-view to determine what detail goes where using the 1/2 dozen or so lo-res photos as reference. Anyone with hi-res photos I'd love to see them. I have the Air Enthusiast article from this forum plus a couple of other pictures from the 'net and two conflicting 3-views! At least the comp is 'sport scale'

Pat (ready for holidays)
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Old Nov 10, 2008, 02:14 AM
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Milhafre's Avatar
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I love ita wonderful choice!
What's next, a Blackburn Blackburn? They'd look great in formation.

Roly
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Old Nov 10, 2008, 02:52 AM
Light and floaty does it
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Pat, I can't say I'm surprised: it was only a question of whether you or Tim Hooper got there first.

Airfoil: how scale do you want to be? If going for maximum scale character, with functioning bracing I'd go with a normal scale pre-war biplane airfoil, probably RAF-15 (what a Moth uses). That will look right, with its slight undercamber. But it's very thin so you will need the bracing to earn a living.

However for ease of building I doubt anyone would criticise you for going with any thin glider-style flat-bottomed section in the 10% thickness range. That would give you greater cantilever strength too.

One scale feature I'd avoid is the very sharp-looking leading edge. It's never a good idea on a subsonic aeroplane.
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Old Nov 10, 2008, 06:38 AM
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Hello Pat,

That looks like a good plane to model, even if ugly. Good luck..

I tried to find the airfoil - could reach most of the Avro airfoils, not this one. As you may have already found out, most of the Avro designs use the NACA 23018 profile (http://www.ae.uiuc.edu/m-selig/ads/aircraft.html) - maybe this one also?

Bulent
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Old Nov 10, 2008, 06:42 AM
Light and floaty does it
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No, it's definitely not 23018. That's a fat-belly monoplane section. Lancaster wing, basically.
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Old Nov 10, 2008, 07:01 AM
North East England
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Definitely very 'Blackburn Blackburn' as Roly says... if it flies like Terry Manleys Blackburn, which I saw many years ago, it'll be a winner. Should knife-edge beautifully with that fuselage

Steve
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Old Nov 10, 2008, 12:33 PM
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Hi Pat,
I'll echo Roly's comment - what a wonderful choice - although only a mother could love the looks. There are quite a few pictures of this aircraft in its various states of modification, in 'British Flight Testing', the only reference that I could find it in!
It did not find much favour at Martlesham.. 'marginally acceptable' and a 'poor kite' were two comments - just the sort of comments to make it a 'must-build'
Paul W.
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Old Nov 10, 2008, 02:17 PM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
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Thanks for the interest folks - but really, it's not a patch on the Blackburn in the ugly stakes
I had seriously thought of just using a Rake-style flat bottom wing section but a thin Clark Y looks OK. I cant decide whether there is any undercamber or just flat - it's definitely not much as the underside rib tape look fairly straight. The 10% Clarke Y will do as a starter.

I'm sure Peter Rake wont mind but the only comparable model I had built before with identical upper/lower wings, no stagger etc was the B.A.T. Baboon. So I overlaid the Bison 3-view and the various incidence angles etc were very close so that determined the basics. The Baboon flew well so I'm not expecting problems there.

The Napier Lion engine has more of a history than I thought. As a W12 (3 banks of cylinders, it seemed to satisfy many 20's and 30's racing enthusiasts in cars boat etc. Only a few cylinder heads, exhausts and air intakes will be showing on this one though.

Pat
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Old Nov 10, 2008, 02:23 PM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
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Early British arrestor wires

Because the historical background of an aircraft interests me, does anyone have a description of the rather odd arrestor wire system used on early Bristish carriers? I believe it was called 'the trap' and had a grid of longitudinal and cross wires - the long ones keeping the plane straight and the cross to stop it. As it was abandoned, I guess it wasn't the best.

Any ideas anyone? Maybe a picture?

Cheers

Pat (packing holiday bags)
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Old Nov 10, 2008, 03:08 PM
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This plane brings to mind the saying , beauty is only skin deep , but ugly goes all the way through !
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Old Nov 10, 2008, 03:36 PM
a.k.a Maltone
Australia, NSW, Goulburn
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LF - your comments cut me to the core. Hey, it can't be all bad - they even made a float plane of it (even more ugly?)

Pat
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Old Nov 10, 2008, 03:44 PM
a.k.a Maltone
Australia, NSW, Goulburn
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Does anyone recognise the prop style in the first post pictures? My notes say nothing of the prop manufacturer.

Manzano has a 13" in 'Sopwith' or pre-war Hurricane wooden style that may be adaptable.

Pat
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Old Nov 10, 2008, 04:01 PM
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Quote:
Originally Posted by maltone
Because the historical background of an aircraft interests me, does anyone have a description of the rather odd arrestor wire system used on early Bristish carriers?
This is from "Pictorial History of the RAF" by John W.R. Taylor:

Quote:
The pioneering tradition of the old R.N.A.S. did not lapse with the formation of the R.A.F. On the contrary, almost all of the basic techniques of modern carrier design and deck flying were worked out during the first post-war decade.
Deck landing facilities installed on H.M.S. Furious during the first World War had been primitive. Fore-and-aft arrester wires, a few inches apart, were supported six inches above the deck, which measured 284 ft. long by 70 ft. wide. Furious's aircraft had skids instead of wheels and the idea was that the horns on these skids would engage under the wires to bring the aircraft to a halt. If they overran the wires, they were stopped by a rope crash barrier, at considerable cost in broken propellers and buckled wings.
A worse hazard was that the midships funnel and superstructure produced dangerous air currents over the rear deck. So when the war ended, the Navy and R.A.F. engaged in an extensive programme of carrier research with H.M.S. Argus.
By then, this ship had been bestowed with the somewhat uncomplimentary nickname of the 'Flat Iron', which is what she looked like, because the air current troubles of the Furious had been taken to heart and the Argus had been rebuilt with a completely unobstructed flight deck, 550 ft. long by 68 ft. wide. Even the smoke from her funnels was exhausted at the stem.
Pilots found the result much more attractive than did sailors, for one series of 500 landings on that long, flat deck resulted in only 40 crashes, plus minor damage in 90 of the other touch-downs, which was considered remarkably good at the time.
Most of the trouble was caused by the fore-and-aft wires, because once an aircraft had touched down it was anchored firmly to the deck. If it had too much drift or came in one wing low, so that the wires were engaged by the horns on only one skid, its pilot had no hope of taking off for a second attempt.
In an effort to ensure that both skids would engage, the lift which took aircraft from the Argus's deck to the hangar beneath was left nine inches below deck level during operations. The aircraft touched down in this 'pit' and were then braked by running up a slight slope with a narrowing gap between wires and deck.
Use of the lift was superseded later by a recessed pit right across the flight deck and when the new carrier Eagle entered service she had also a succession of hinged wooden flaps across her deck, supported by the fore-and-aft wires, so that the aircraft were slowed progressively by knocking down the flaps. Unfortunately, this tended also to remove their undercarriages.
Not until H.M.S. Courageous and Glorious (sister-ships of the Furious) entered service was a completely satisfactory solution found. Instead of fore-and-aft wires and a pit, these carriers were equipped with palisades to catch aircraft that would otherwise have drifted off the side of the deck into the sea, plus transverse 'spring-loaded' arrester wires on the rear part of the deck.
Wheels had already replaced skids: now the horns also gave way to a deck-hook, first tried on a Fairey IIIF, and the modern type of arrester gear was born.
In fact, these ships set the pattern for future carriers, for they introduced also the now-familiar 'island' superstructure on the starboard side of their flight decks. Tests with mobile dummy bridge structures on Argus had shown that such an island offered a good bridge position, caused no dangerous air currents, and would not get in the way of pilots, who invariably turned to port if they decided to go round again after a baulked landing.
Since then, the basic deck operating techniques have changed only insofar as they have had to be streamlined and speeded up to cater for ever-increasing aircraft performance.
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Old Nov 10, 2008, 05:00 PM
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Pat -- you may recall from a response of mine to an earlier thread of yours that I have long been awaiting a model of this one, ever since seeing a peanut sized masterpiece by Bill Noonan. Some reference info was posted here:

http://www.rcgroups.com/forums/showt...ighlight=bison

Scroll down to post 116

That was in response to a Peter Rake inquiry about future projects, before he got wrapped up in "downsizing" many of his planes to IPS size:

I will eagerly follow this effort. The Bison is so ugly, yet has so much 'character' that it looks like a Tim Hooper project!

Pete G
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Old Nov 10, 2008, 06:43 PM
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Quote:
Originally Posted by maltone
Does anyone recognise the prop style in the first post pictures? My notes say nothing of the prop manufacturer.

Manzano has a 13" in 'Sopwith' or pre-war Hurricane wooden style that may be adaptable.

Pat
Happy to do you a prop if we can work out what.

Have a look at the FE8 11" 4 blader I did.

That might be close

The 2 blader looks horribly like an early 'watts ' type. But simple enough to do.
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