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Post by elephantshampoo on Oct 26, 2014 8:48:31 GMT 12
So far I'm aware of Spit, K-4, Dora. What else?
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Post by davidd on Oct 26, 2014 11:20:02 GMT 12
Wooden props were particularly popular with RAF as they were probably cheaper and certain a lot lighter than equivalent metal props, and saved many an engine from being stripped down after a landing accident because with the prop taking the full shock of being stopped abruptly, the engine and reduction gear were spared the extra stress (usually!). So far as I know, Rotol manufactured all the wooden props (that is modern variable pitch and constant speed props with all-metal hubs and separate wooden blades) used by the RAF in WW2. All De Havilland props were all-metal and designed on Hamilton Standard principles, while Rotol also built quite a number of Curtiss Electric props with metal blades, with their other props being hydraulically operated. RAF British-built aircraft with De Havilland/Hamilton Standard counterweight or Hydromatic all-metal props included practically all Blenheims, Hampdens, Whitleys, Sunderlands, early Wellingtons, Stirlings, Mosquitos, Hornets, Beaufighters, Lancasters, Lincolns, Albemarles, Tempests, Typhoons, Whirlwinds, and early Spitfires and Hurricanes (once they had their original wooden two blade props replaced), with most other single-engine fighters having Rotol props with wooden blades, including most British-built FAA aircraft (Albacores, Barracudas, Sea Hurricanses and Seafires, Fireflys, etc). Some of the aforementiond types later progressed to Rotol hydraulic props with wooden bladess, including most Wellingtons, although some had electric props. Halifaxes also used a varity of props, including wooden-bladed Rotols, and HS Hydromatics. May be some ommissions and minors errors here, for which I aplogize. No doubt the Germans used wooden-bladed props during the war for exactly the same reasons. However the USA (USAAF and USN/USMC) only used metal props in all aircraft larger than primamry trainers and light observation types.
David D
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Post by elephantshampoo on Oct 27, 2014 9:39:48 GMT 12
US missed the boat, P-51 attempted hollow blades, but it sdidn't work as hoped. Yes, they do reduce wear & tear on gears & also reduce torque on takeoff issues. Increase speed also if the K-4 figures are accurate,( 452 & 459 mph), this would seem to be the case. It takes a bunch of weight off the nose and dampens the vibration so that the airplane definitely feels smoother and lighter on the controls. It also makes power faster -- it spins up right away. For what it's worth, there is one on Jim Richmond's personal Cub. www.supercub.org/forum/archive/index.php/t-23107.htmlIt is posited here the origins of all this are here..... something called Leichtholtz-Mantel AFAIK For it's wooden propellers Rotol used German manufacturing technique called Leichtholtz-Mantel. Patented by Gustav Schwartz Propellerwerk already before the war. At least in German propeller blades resin-impregnated (under high pressure) wood was used only on the middle, the sides being made of lighter wood strips (spruce IIRC) glued together and carved. This helped in keeping the balance of the blade, the "spar" in the middle being heavier than the leading and trailing parts. forum.12oclockhigh.net/showthread.php?t=10365&page=2 |
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Post by davidd on Oct 27, 2014 18:14:03 GMT 12
Yes, it would seem that the Germans led the way, and the British followed. The RAF was concerned about the increasing weight of metal propellers as engine powers were increasing in the mid/late 1930s, and particularly with respect to the new 2,000 HP-types then under development (Naper Sabre, Bristol Centaurus, RR Griffon and Vulture, etc.) It was noted that the Germans firms were very keen on developing lighter weight (composite wooden) props, although not necessarilly for more powerful engines, but apparently with good potential in that direction, so certain British firms purchased manufacturing rights for these. Both Bristol and Rolls-Royce had purchased rights to produce the Hele-Shaw - Beacham hydraulic propeller, which had been under development in the UK for some considerable time, and they joined forces in about 1937 to manufacture this prop in the UK, and formed a new company for the purpose named Rotol (by combining first and last parts of the names of the respective firms). Rotol was very keen to reduce the weight of their new prop and used an alloy of magnesium called Magnuminium, which was forged and supplied by High Duty Alloys of Slough. To further reduce weight, some of the early Rotol hydraulic props were also made of more-or-less pure magnesium. Also at this time, Rotol Airscrews purchased a manufacturing license to produce the Curtiss Electric propller (which also boasted feathering capability), although this did not appear in the UK for several years (about 1941?). Interestingly another British firm purchased a license to produce the German VDM (Vereinigte Deutsche Metallwerke) electric propeller with full feathering capability, but this arrangement never came to fruition.
It seems that Rotol got interested in the German-developed composite wood prop blades also from a very early stage. There were at least three different patents involved, owned by Jablo, Schwarz, and another firm as yet unidentified. These, were, however all quite similar, and involved careful selection of wood and compressing and heating the layers which were all impregnated with adhesive. The weatherproof covering processes of the blades, which were first covered in fabric, were also patented, and leading edges were provided with suitable protection; one type even used rubber leading edges.
David D
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Post by elephantshampoo on Oct 28, 2014 8:15:13 GMT 12
Interesting how wood & metal swapped places in the 30's-40's timeline. Mossie, Yak 3 were ahead of the curve, but then some say the YAK 3 couldn't accept damage, either crash landings or battle damage. I read a few yrs ago of a modified Spit with wooden central fuselage, climb rate soared.
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Post by davidd on Oct 28, 2014 11:59:41 GMT 12
Cannot imagine why a Spitfire "modified" (why?, where?, when?) with a wooden central fuselage should have a dramatically improved climb rate. Did this source explain exactly why substituting wood for metal in a presumably more-or-less identical aerodynamic structure should have such a dramatic effect on performance (which suggests that weight may well be involved). However was this an operational aircraft with all normal equipment installed?
There have been several aircraft that I can think of (Harvard, Walrus, Lockheed Vega) which have had various components changed from metal to wood (or wood to metal in case of the Vega), but performance was never affected to any great degree. In the case of the Walrus, the entire fuselage of the Mk. II was all wood, whereas all the Mk. Is were entirely built in light alloy, but with fabric covered flying surfaces. During the latter part of WW2 in both Germany and Japan, as well as the USA to an extent, certain aircraft companies were required to substitute wood for metal in such componenets as tail groups, wings, etc. Improvements in performance were never really expected - if such was the case it would be a bonus.
A very few aircraft were built almost entirely in one material, then another, although this was to suit the demands of whoever was ordering the aircraft. One was a wooden version of the Brewster Buffalo built in Finland (only a prototype) while the little Airtourer side-by-side trainer designed by Henry Millicer (spelling?) in Australia in about 1953 for a competition, had the prototype built all-wood, but all production models were wrought in aluminium by the Victa Motor Mower company. Most of the improvement in performance of the production Airtourers was as a result of the greater horsepower of the power plant (115 versus a mere 65 of the prototype). The decision to produce this aircraft in metal was stated to be the greater longevity of a metal aircraft in a harsh climate where light aircraft were often left outside for long periods - keeping a wooden aircraft in tip-top shape for decades required constant hangarage, etc.
David D
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Post by elephantshampoo on Oct 29, 2014 6:58:15 GMT 12
Yes David, it was a weight issue. The 109 wood tail actually weighed MORE than it's metal predecessor, but had the fortunate effect of oscillating less, which produced better dive rate. I'll try & seek the modified Spit. No luck so far, but did find this.. www.airport-data.com/aircraft/photo/000111538.htmlAs to 109... 906 km/h is 562 mph Versuchs-Bericht Nr 109 05 E 43 - Date 15.4.43 This original German test document refers to dive tests of 109s with the tall tail. Result of this test was that the new tail reduced highspeed diving ozillations (which sometimes appeard with the old tail). More interesting is the fact, that in this tests, which had not the aim to estimate the highest mach number or to test the structure, they reached max. Mach 0,805@7.0km max. TAS 906km/h@5.8km max. IAS 737km/h@4.5km 109lair.hobbyvista.com/techref/structures/tails/109.05e43_report/05e43-p1.htmThere was an all wood Frank also, reduced 1000 pounds of weight, ( well, the KI 116 weighed less than the KI 106 for clarification). Nakajima modified the structure of the Ki-84-I so that aluminum could be saved by constructing some components of wood. This lead to the Ki-84-II having the rear fuselage, the wing tips, and other minor elements built of non-strategic material. This concept was taken one step further when the Tachikawa Hikoki K.K. company built an all-wood version of the Ki-84 that was designated the Ki-106. The Ki-106 program was a complete success, but the course of the war caused it to end before the results were fielded. The last variant of the Ki-84 was the Ki-116, which built by Mansyu using a different engine and a three-blade propeller from the Ki-46. This resulted in a reduction of 1000 pounds of weight, and though a successful design, the aircraft had not completed the testing phase when the war ended. www.daveswarbirds.com/Nippon/aircraft/Frank.htm |
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Post by elephantshampoo on Oct 29, 2014 7:34:00 GMT 12
Then we have ..
Yak 3 Empty weight: 2,105 kg (4,640 lb)
Yak 9 Empty weight: 2,350 kg (5,170 lb)
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Post by baz62 on Oct 29, 2014 11:52:55 GMT 12
That looks like the airworthy all wood full scale replica of the prototype Spitfire that now resides in the Museum at Southhampton. (Unless there is more than one?) |
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Post by elephantshampoo on Oct 30, 2014 9:22:27 GMT 12
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Post by nuuumannn on Oct 31, 2014 14:27:17 GMT 12
Things have come full circle in modern times as Dowty Rotol no longer build wooden props. Warbird restorers wanting accurate reproduction Rotol props turn to Hoffman Propeller GmbH of Germany and you'll find almost all the Spitfires flying today, including the ones here in New Zealand have Hoffman props. www.hoffmann-prop.com/en/13/Propeller_Vintage_AircraftHoffman also manufacture hovercraft props; the rescue craft at AKL have Hoffman props. www.hoffmann-prop.com/en/15/HovercraftIt's also worth noting that Rotol wooden props were intended as much to reduce strain on the engine if the aircraft suffered a prop strike by shattering. This prevented internal damage to the engine if the props were struck or the aircraft came down without its gear down. Rotol props were made of mahogany and covered with a variety of different coatings depending on their application. These were Rotoloid, Jablo and other names and the props were classified as such. Regarding lessening impact damage, the Merlin was designed so the reduction gear box would break off and absorb punishment in a crash, thus saving the internals of the engine. I got told that by a member of the Roll-Royce Heritage Trust once. Interesting story. I can't find any info on a wooden Spitfire fuselage (new to me), but a bakelite fuselage was constructed, two, in fact and structural trials were carried out at Farnborough - it was called the Aerolite Spitfire. There's a couple of pages on it in Morgan and Shacklady's book Spitfire the history. Many German instrument panels were made of wood, Also interesting to note the Me 163 Komet's wings were wooden and its control surfaces were fabric covered. Unusual in light of the high speeds the aircraft reached. See here. rnzaf.proboards.com/thread/19747/messerschmitt-me-163-komet-detailThe Heinkel He 162 also had wooden wings, the Germans increasingly turning to wood due to wartime expediency in the latter years of the war. |
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Post by elephantshampoo on Nov 1, 2014 7:41:19 GMT 12
very interesting point...
It's also worth noting that Rotol wooden props were intended as much to reduce strain on the engine if the aircraft suffered a prop strike by shattering
The He 162 according to Eric brown had the best roll rate of any WW 2 ETO fighter. Jet in center vs in wings.
The lightweight 109's will likely forever be a mystery as what parts were wood, what other lightening methods were employed, we do know they existed via Kurt Buhligen, but no official weight measurements etc unfortunately.
Some call them Erla "clean" K-4s
clean fighters for freijäger Erla G-10, then Erla/clean K-4
reported as the fastest, cleanest, lightest Messers of the late war, Erla lightened and cleaned up their airframes and are different to those produced elsewhere, an Erla G-10 is as fast at 5000 metres that a Mustang is at 6500 metres
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Post by Mustang51 on Nov 6, 2014 12:42:15 GMT 12
Strangely enough, The Wackett Trainer had wooden wings but the modified Cropmaster had metal wings although apart from the slots and rounded tips, they were the same as the Wackett yet much lighter. John Gallagher on this side of the Ditch is restoring a Wackett but is having the best of both worlds using a Cropmaster wing but fitted with the rounded tips and fixed slots. However, to add to the weirdness factor, is removing the metal skin from the Cropmaster wing internal structure and bonding plywood to the metal. All engineered and approved ! When finished it shall be indistinguishable from the original but have the added benefit of the metal wing which is lighter. And John is a perfectionist and wood craftsman amongest the best there is !
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Post by nuuumannn on Nov 6, 2014 13:43:18 GMT 12
Good luck to him and his restoration; strange looking bird, the Wackett. Had a look at Morabbin's many years ago.
And then there is the Anson I with metal wings, which many enthusiasts scorn as not being 'authentic', even though Avro released a mod - can't remember what number - that stipulated the modification of the Anson I with metal wings for operations in Australia. There's one with wooden wings on display in Australia somewhere, isn't there? I think there's one in Canada too.
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Post by davidd on Nov 8, 2014 11:47:35 GMT 12
Grant,
I guess the modification of wooden-winged Ansons to have all-metal wings (and probably also the complete all-metal tailplane/elevator assembly) was a desperate/pragmatic attempt to keep alive commercial Anson operations in Australia after the wooden wings fell totally from favour in the early/mid 1960s (and would have been the same here if we had had any airworthy on this side of the ditch). Perhaps Avro also marketed this concept themselves in other areas of the world - after all the aircraft owners would have to use Avro-approved parts, although there cannot have been too many of the early wooden-winged examples still flying then (perhaps most were in Canada and Australia, where the later metal-winged aircraft were a rarity). I think it was the fact that the main fuselage pick-up points for the mainplanes (and tailplane) were basically identical when the metal items were introduced in production, so it would have been a fairly simple matter (relatively speaking) to upgrade your old wooden-winged "Annie" (as was done at Wigram, and by Bill Reid in Nelson). Although metal-winged Mark Ones use all authentic Avro parts, it can hardly be argued that they are still the kind of Mark Ones as used by Commonwealth forces prior to and during WW2. I remember one of the older guides (Davey Jones I think) at the RNZAF Museum in the early days (late 1980s) being very confused by the Anson on display - he was fairly certain the ones he was familiar with in the UK in 1940/41 had wooden wings, concluded that his memory was playing tricks with him. I was able to advise that in fact there was really nothing wrong with his memory.
David D
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Post by nuuumannn on Nov 8, 2014 13:01:53 GMT 12
Dave, pretty much from what I've read. Found more info. The Australia Department of Civil Aviation introduced restrictions on Anson I operations in July 1961 and at the beginning of 1962 over water flights were banned, also owing to the aircraft's poor single engine performance, then on 1 July that year, Anson Is were grounded. After a number of incidents, inspections of wooden wings had revealed delamination and deterioration. The C of A of wooden winged Ansons was removed world wide that year too. The operators of VH-BAF - Bill's Anson sidestepped the grounding by fitting a metal wing to the aircraft, so when Bill bought it, it already had its metal wing. It came from a spare in RAAF stores. Makes more sense to have it owing to structural strength, ease of operation etc. Bill told me in an interview before MH120 (its original serial) flew at Nelson that the Avro mod was numbered 603 and metal winged Anson Is became Series II aircraft from then on. The fairings aft of the engine firewalls were still made of wood and covered in fabric on metal winged Anson Is.
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Post by davidd on Nov 9, 2014 9:08:37 GMT 12
Grant,
Thanks for that additional information re metal-wing conversions. Come to think of it, I have the Air Britain Anson monograph (The Anson File), although this series tends to be rather shallow (actually very shallow) on technical development, being aimed more at the general story and individual aircraft histories, civil as well as military. Whilst on the subject of Anson modifications, does anybody have the modification number and date of introduction of the new windscreen setup, which must have been introduced into production in late 1938/early 1939 or thereabouts. This was when the original "streamlined" windscreen with no wipers (supposed to be self-clearing, but wasn't) was replaced by the more upright arrangement with very prominent externally mounted windscreen wipers. The Anson File implies that this was a feature of new "trainer" version of the Anson, along with landing flaps (all previous production had been flapless), but I am not entirely convinced on this point and believe that these were more likely to be general modifications which would have been introduced regardless as being highly desirable, not only in the original coastal reconnaissance role, but would prove just as useful on training duties.
And as to delamaination of the wooden wings and general deterioration caused by the ingress of water, damp, etc, the RNZAF had this problem arise in its 1942/43-vintage Mk. Is in 1946/47, which casued great distress, as it was hoped to get a few more years work out of these rather obsolete aircraft due to government reluctance to spend scarce money on new aircraft at this juncture. Various problems with the electrical wiring as well as our Ansons having two different radio standards (1942-built aircraft NZ401 - 414 had 1082/1083 sets, 1943 aircraft had 1154/1155) tended to favour the later aircraft, as the earlier radio equipment was definitely very obsolete, whereas our Mosquitos and Sunderland IIIs were fitted with the later sets.
David D
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Post by nuuumannn on Nov 9, 2014 13:50:13 GMT 12
Dave, I don't know if the less raked windscreens were an actual 'mod' as such or whether it was just retrofitted, as I've seen images of Australian Anson Is together after delivery and they have both types fitted. Images taken of Aussie ones during 1938/1939 seem to be of both types. Some of the earlier windscreens were still visible on Aussie Ansons in 1945. Bill Reid was saying that the earlier windscreen could easily be removed and the later style fitted, VH-BAF had the later style fitted when Bill bought it. According to one account I've read, one of the reasons behind the raked windscreen being removed was that it introduced too much glare in the pilot's visibility and so it was replaced, as well as the wiperless idea, which didn't work as well as hoped.
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