Geodetics – good or bad?

I agree the bomb-load issue was probably a number of factors, and clearly it was possible to put cells in the wings and perhaps a fuselage bay. Anyoneone got verified data on any of that?

Your last posting with the drawing would seem to suggest that the geodetic structure couldn’t have worked if solely used, ie still required standard systems for structural integrity, and that it was for aerodynamic shaping and light construction that it was good for.

To be fair the wing is a more advanced (later) design, the fuselage being a development of the Type 253’s. Here’s the wing (Aeroplane again) and again, it does seem like a lot of bits to make the thing, although the geodetics are taking more of the loading, IMHO.

I’m still intrigued as to why you could cut a hole in the wing for a wheel when in the Wellesley, but not a bomb-bay, yet the Wellington got a bomb-bay. My suspicion is they just didn’t see internal armament as important initially.

Probably partly correct about lack of importance given to internal weapons load (which we have returned to on anything other than stealth), also seems a common idea at the time to either have very small bomb bays or to have them in shallow segmented compartments. The Wellington featured the last, but as did the Heyford and the monocoque Blenheim, Battle, Stirling, and even the early Halifax, all of which must have added to the contrast of the remarkable bomb capacity of the Lancaster.
I’ve never counted the amount of bomb doors on a Wellington, but certainly greater than two!
As for the Wellesley that was a light bomber, and the external wing pods housing the bomb bays may have actually seemed a good idea.
What I’m trying to say is maybe this concept wasn’t just down to limitations of geodetic designs.

Your last posting with the drawing would seem to suggest that the geodetic structure couldn’t have worked if solely used, ie still required standard systems for structural integrity, and that it was for aerodynamic shaping and light construction that it was good for.

My take on Geodetics… Great for large Airships…not much use for aircraft.
regards baz

just to elaborate a little on the above comment,a book I enjoy re reading every couple of years is the autobio ‘Slide Rule’ by Nevil Shute,he was part of the design team for the R100 and it is a fascinating insight into the evolution of geodetics – a very successful airship design.
VA could have and should have switched to a more conventional construction technique for large a/c – perhaps they were overawed by BW’s influence.
The Halifax was the best option for heavy glider towing because its fuselage was built like a brick ‘outhouse’ and did not stretch like most other types.

cheers baz

Galdri, from my records I can say that two Wellingtons (X3286 and HE731) and One Warwick (BV230) were coverted and tried as glider tugs, this compares badly with the Lancaster which numbered three converted (R5606 DS819 and LM451) Oh and one York (MW132)

The reasons for why they weren’t used in service is, of course the crucial point. The Avros were needed for higher priority tasks. The Wellington and I presume the Warwick were, as Galdri said, unsuitable, although one reference I have (Green/Swanborough) says the Wellington III was cleared for target towing, while a couple of others said it wasn’t a good idea at all!

Thanks Vega, some very good points there. My garden hose seems to have geodetic style reinforcement, too!

I think the issue with the Vickers-Armstrong/Wallis patent geodetic construction was that it was a complex hybrid. The attached illustration (from a 1938 Aeroplane magazine) of a critical joint in the Wellesley shows how it was in addition to fuselage frames and longerons. Wallis saw it as a good way of replacing the wood and fabric former over the metal frame (as per Hawker style construction) to make a load-bearing structure that was the streamline shape itself – well and good, but stressed skin construction and semi-monocoques were being developed and were more flexible in application and manufacture, IMHO. In other words an interim step, perhaps and another victim of the rapidity of 1930s development?

Galdri, from my records I can say that two Wellingtons (X3286 and HE731) and One Warwick (BV230) were coverted and tried as glider tugs, this compares badly with the Lancaster which numbered three converted (R5606 DS819 and LM451) Oh and one York (MW132)

Geodetic structure (Modern names- Lattice or ISO truss structure) is an extremely efficient way to combine low weight with high load carrying capacity.

Somewhat surprisingly it is still used today (although without fabric). Consider the following;-

Typical Modern Bypass casing on most high performance Military Gas Turbines (Example is EJ200)

http://en.wikipedia.org/wiki/Eurojet_EJ200

This inter-stage spacer and propellant tanks on the Russian Proton M rocket

http://www.mscsoftware.com/events/vpd2007/emea/presentations/EMEA_VPD2007_Khrunichev-eng_R_2007_12_14.pdf

And even this bike frame

http://cozybeehive.blogspot.com/2008/01/isotruss-open-lattice-structure-for.html

For a given geodetic structure the degree of stiffness (or its flexibility) is a function of the detail design of the cells and elements. As such it can be adjusted, within limits, to what ever is desired. The above examples prove this is still effective for demanding high stiffness application even today;- Hence I think the Windsor, rather than this being proof that Geodetic is incapable of producing stiff structure, is actually an example of the designers getting there overall structural optimisation sums wrong. What the Windsor did nicely illustrate was that if you got a few of the very initial sums wrong, the whole project would be toast because you had to change every single detail structural component in order to correct it ……a real bin everything & start again from scratch situation……. maybe the reason why Windsor was an expensive one off failure at a time of great need ?

As for the Wimpy not towing, geodetic is very “single point optimised design” and hence if the load case has not be addressed in the original design then you have no chance of adaption. Hence if no tail hard point for the glider tug load was considered at design stage, then no adaption is possible for towing once in service…… Again I can’t see a good reason why airframe flexibility would allow good overall flying characteristics but prevent glider towing. (BTW the AF loads introduced by the mag mine ring were tiny in comparison)

Geodetic current application is limited by high production cost but as A/C & spacecraft operating costs are squeezed and new manufacturing methods become available, we will see more of it.

unwilling to flex in most directions.
Ben

Nasho – fascinating.

Guys, I know nothing about what you are talking about, BUT, would like to add my 2 p´s worth. As I´ve read, the Wimpy was unusable as a glider tug Because of excessive flexing of the fuselage! It is a long time since I read this, and this is purely from memory. But how many Wimpies have you seen as used as glider tugs? I´m willing to be proved wrong, as usual:eek::eek:

Nashio, maybe the balsa/glue combination in your experiment reacts different to alloy rivited/bolted together?? I just do not know, just a questionþ

There could be problems switching production between more conventional aircraft

Short Brothers refused to turn the Swindon works (making Stirling) over to Lancaster production and, in dispute with the Government, the company was nationalised.

Once the Government had charge they ordered 200 Lancasters to be built at Swindon (under Armstrong Whitworth) which was cancelled in Sept 43 and Stirling production reinstated because structures weren’t in place to switch . So the works carried on making an aircraft MAP didn’t really want.

Source – RAeS talk by Gordon Bruce last month.

…but a good engineer will point out that all structures have to deform under load to some degree! 🙂

Hah, caught by the caveat. Long time since I read my JE Gordon. Thanks. 😉

The problem with building geodetic aircraft in factories was simply speed, apparently, and that had nothing to do with turning out individual aircraft. (A good point that assembly could be undertaken with semi-skilled labour, could be repaired relatively easily, could be sub-contracted and built in sections well, etc.)

But, setting up the factories took an inordinately long time, and after then there was never time enough to lose during the war to switching them to ‘conventional’ construction, locking them into producing an obsolete system. While the Wellington was a great aircraft in 39-40, the Windsor cannot have been anything but a joke.

I’m still intrigued as to why you could cut a hole in the wing for a wheel when in the Wellesley, but not a bomb-bay, yet the Wellington got a bomb-bay. My suspicion is they just didn’t see internal armament as important initially.

As Pondskater says, interesting comments – and much more useful than I thought. Nasho – fascinating.

Any engineer will point out most structures have to deform under load to some degree…

…but a good engineer will point out that all structures have to deform under load to some degree! 🙂

I do remember watch a war time film of a Wellington being made in a day.

This one you mean?

http://www.youtube.com/watch?v=KVk1OP_LQH4

(There is a better quality version of this on YouTube but I can’t find it.)

Interestingly the geodetic construction seems to lend itself very well to construction from relatively small sub-assemblies.

Interesting comments.

I wonder if the individual parts were that specialised, how easy were they to make and how that played out in new factories where there would, typically, be very large percentages of unskilled workers learning their trade.

im not sure if this is relevant to your question, but my first year uni project, was to design and construct a wing 500mm in length from a limited supply of balsa wood, that was to be as light as possible, and then put through the following tests

1) once clamped to a workbench the wing was to be loaded up with a kilogram loading acting above the wingtip, and then below
2) the wing is to be then put into a jig where it is put then through a torsional test of +/- 10 degrees

if the wing passes both of these tests, it is then moved to the final test

3) the wing is moved back to the workbench clamp and then loaded up to destruction

the winning wing, is the one that achieves the highest performance ratio, which is the maximum mass achieved during loading (in grams) divided by the weight of the wing in grams

now onto my point, our design involved a simple ish geodetic lattice, and we found that from balsa wood, and glued with pva! that it was incredibly strong. though it barely passed the torsional test (took 4kg of load to move it through 10 degrees!!!) our final loading test resulted in us taking the record for the highest weight taken, at 10.5kg!!! giving a performance ratio 190.9 (our wing weighed 55g)

as it is, we encountered all the problems described above, it took our group twice as long as any other to finish our prototype, the carving of strips of balsa literally took hours and hours, as we’ve said the wing really did not want to twist at all, and did not show any signs of the load applied (ie beinding) until we had applied almost 8 kg. at the end of the day, we won, with our geodetic design, but it took us three prototype wings to perfect our design, the inital prototype was a catastrophic failure, it failed at only 2 kg of loading partly due to our building methods and an unforseen flaw in our design.

my conclusions really were that it is a lot of effort to design and build a geodetic lattice, as we found out at first, get the design wrong and the results are catastrophic.
once your design is right, again, the construction is incrediby laborious and difficult in assembly. generally the finished product is incredibly strong (as can be seen by our test conclusions) though was unwilling to flex in most directions.

Cheers

Ben

AK should be here soon!

Sooner than even I envisaged!

B.Wallis: ‘“the practical shop element of personnel (at Weybridge was) bitterly opposed to (my) geodetics”. (He) was persuaded to accept design changes in the interests of cheapening manufacture’ S.Ritchie,Industry & Air Power,Cass,1997,P83. When evaluating (to be V-Bomber) bids, T.660 (to be Valiant) was rejected in part because it was seen as too low/slow, but RAE took the chance to lecture Vickers generally on “over-ambitious” fabrication techniques (can’t retrieve my source for this). 1935 Warwick/1942 Windsor had failed: evidently perceived in 1947 by RAE/MoS to be because of, not despite geodetics. Air Ministry Agency Factories Broughton and Squire’s Gate were funded for the purpose of building the intended prime Heavy, Warwick; Wellington was put in as lead-in template with no intention of buying many, certainly not to 1945; V-A was awarded the site Supervisory contracts in 1938 because they persuaded A.M. that geodetics were too complex/beyond the management wit of new-entrants: Austin/English Electric/Harland/Metro-Vick/Rootes might cope with “normal” big structure, but not Wallis’ brainchild.

I take JDK’s “rugged” point – many Brit brick-dunnies were so. On “flexibility” have I not read of Warwick directional stability issues (“porpoising”)? Why did no-one else go with Wallis’ Eureka?

I’ve often wondered the same thing as you JDK, seems alot of bits and hard work to make.
I thought that geodetics were used by Vickers to make aircraft because the Air Ministry wanted a design technique better than steel tubes and formers, but more conservative than stressed monocoque system for the bomber designs. Eggs and baskets.
I think for the era of the Wellesley and early Wellington this system was fine, and possible slightly advanced in production types in service.
But why on earth did Vickers carry on with the technique for the Warwick and, more amazingly, the Windsor (this monstrosity made its first flight a whole year after the B-29!), just dosen’t seem to make sense apart from ease and knowledge of how to build that type of aircraft structure.
I think there is some argument for its flexibility, battle worthiness (was this considered at design stage though?), and its comparitively easy to repair nature, and I do think that is why the Wellington managed to still be well established at the end of the war when many of the types it entered service with were long gone. Indeed the Coastal Command versions were valuable machines.

I can’t see how geodetic construction is particularly favourable for high aspect ratio wing design, Consolidated managed with stressed skin ok.

In short, good idea for light streamline designs for the 1930s, but very quickly obsolete by the early 1940s.

AK should be here soon!

My suggestion was that the flexibility inherent in geodetic design was excessive.

A nice piece of understatement James 😀

My take on Geodetics… Great for large Airships…not much use for aircraft.

regards baz

My father has always wonderd if making all the geodetics was worth the time and effort, compared to a stressted skin aircraft. Which can be made more easy. I do remember watch a war time film of a Wellington being made in a day.

Dave

And as for airframe flexibility, some aircraft were designed to be flexible for example the Boeng B47/B52/707 line. I always believed it allows lower structural weight.

Good point! Any engineer will point out most structures have to deform under load to some degree – and we’ve all seen the airliner’s wingtip move up on takeoff. My suggestion was that the flexibility inherent in geodetic design was excessive.

It’s not the count, exactly, it’s the number of specialised pieces requiring significant work. Perhaps I should’ve been clearer.

In what way could a the flexibility be an essential good thing?

I accept the point regarding specialised pieces that probably each required a jig or tool to make, I know it was said that the Wellington could be repaired easily using ready made sections but that alone has a logistics issue.

And as for airframe flexibility, some aircraft were designed to be flexible for example the Boeng B47/B52/707 line. I always believed it allows lower structural weight.

Richard