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TOPIC: Lockheed U-2 Spy plane

Lockheed U-2 Spy plane 1 week 4 days ago #1540

  • rogersimmonds
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The successful Flights of Daniel Rackstraw's Veron Fouga Cyclone at this year's Peterborough Flying Aces and September's Old Warden was the first time (in the UK) I had seen this early Phil Smith Jetex design fly with a rocket motor, and not with a small EDF unit in its pod. This has made me think that a model of the U-2, which has a similar planform can be made to fly successfully.





Above: this early Jetex design (note the ribbed Jetex 50) has a reputation of being very tricky to trim. The high aspect ratio wings are perhaps too flexible and the butterfly tail, too, doesn't make things things any easier. I have seen Cyclones waft about with EDF, but not with authentic rocket power! :S
Daniel's success is probably a result of (a) a very calm day and (b) choosing the right power, in this case a rapier L-2 (100-110 mN).
There are a couple of old U-2 plans one from the late great Paul Del Gatto (one of his less ambitious designs, this!) and a later one by (I think) Allen Hunt.
PDG's design was for Jetex 150 (PAA Loader):







Above: Del Gatto (PDG) did take some liberties with his design, increasing the dihedral and moment arm and, less obviously, enlarged the fin and tailplane. Writing in 'Smoke Trials 5' (2008), I commented, 'Its looks are quite spoiled by the motor 'hanging in the breeze' (4).
Not knowing any better, I was perhaps a bit harsh about this design when I wrote about it in 2008 and, were one to reproduce it today, the relevant motor - a TSP L-3, say, - would still be where PDG put it, but be hidden in a 'weapons', or, more realistically, an 'instrument' pod. PDG's original article is also worth searching out, if only for its opening sentence: "Seldom has an airplane lent itself so well to dual purpose model design". Modern modellers have not found it so, and may be puzzled by the article's last paragraph, which takes an unproblematic performance for granted and ends: "If the model behaves similar to ours it will have a slight stalling tendency with power on. If this is the case it is easily remedied by adding down thrust to the engine". Hmmm .... yes, but how? you will note the 'engine' is on the CG, and there is no hint of that trimming aid so essential to modern profile designs --an adjustable thrust tab!

However, I think one can do better .... watch this space. :)

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Lockheed U-2 Spy plane 1 week 4 days ago #1541

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Some years ago, working from a 3-view, like this one, taken from my treasured copy of 'The World's Fighting Planes' by William Green published in 1964, uber-modeller Chris Strachan made a 'superscale' U-2 with a Rapier L-2 hidden in a trough.





Above: Chris Strachan's OD U-2 for Rapier L-2. It was, I think, made with few, if any any scale compromises and was, says Chris, 'directionally indeterminate'. It may be better, then, to base one's model on a little-known design published the during Powermax 'Jet-X revival of the 1980s. There is, however, a problem with the plan:



Above: I had only a very poor Nth copy of this plan of uncertain provenance. Without much evidence (Google was no use at all, can anybody help?) I reckon it was designed in the 1980s (the Jet-X 50 is a clue) by Allen Hunt (the electronic file had an 'AH' descriptor).

Like Paul Del Gatto, the designer (whoever he was) made some sensible compromises and enlarged the tail feathers, but that apart it is a pretty accurate rendition of the real thing.

Printing out a 'full size' copy of the digital file confirmed showed that many details of the structure are unclear and building from the plan would be more than a little difficult.:unsure:

As my draftsmanship is (too say the least) inadequate I contacted CADmeister Rob Smith who produced the cleaned up plan below:



Rob had to make many fine judgments and interpolations, and he says there are bound to be inaccuracies and inconsistencies still in the plan that would become apparent only in the building. :unsure:
I think it will make a splendid winter project for a bold and experienced Rocketeer who would likes a challenge. So, if you are happy to make corrections to the plan and make changes to the structure as you go along (the wing, for example, looks too flexible and the trough could be deepened to incorporate down thrust), please ask me for a copy. :cheer:
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