Large Model Association Forum

Hi all. Not sure if I'm on the right forum but here goes:- I'm ex-Fleet Air Arm (engineering) and would like to attempt an advanced Westland Wyvern project. Main design preferences to include a working turbo-prop unit (with contra-props), double wing-fold, full retracts, lowering deck hook and torpedo release.

Most likely prototype would be the S4 variant (Python turbine /Suez Campaign), but, others also considered if more appropriate. Questions arise over scale size - 1/4 or 1/5 to accommodate a suitable turbine unit. Also, the wing folding - what would be the best way to power it. Variable pitch props - a bridge too far ? I think the retracts, deck hook and torpedo drop should be fairly straight-forward to engineer with existing methods.

Any helpful tips re plans, proven technical solutions etc would be well received. Timescales: 3 to 5 years ?

Hi Dave

Most of what your looking for is possible, I think a guy in the States has built one at that scale(1/5th i think). It's a big aeroplane, I think 1/4 would really do it justice. The engine isn't a problem, retracts, hook, torpedo all fine. Vairable pitch prop, unlikely, contra rotating not sure.
Arthur Bentley may be a good source for the drawings.

If your not aready in the LMA then I would recommend you join as this model will be over 20kg, you'll also get a lot of help and advice too.


Stewart

Thanks for the advice and encouragement Stewart. The thinking on the props was that as they would need a reduction gearbox anyway, I could add a (reversing) co-axial shaft drive plus some fly-weights to operate the pitch change. There is, of course, the problem of the dreaded inter-shaft bearing to cope with ! (we had some serious wear problems with these on the FAA Gannets). Any ideas on how best to contact Arthur Bentley ? Another forum perhaps. Once the project looks like a 'goer', I'll certainly be joining the Association...ps forgot to mention the Youngman flaps requirement for the in-board mainplane (the outer is a more simple split-flap arrangement).

Hi Dave, check this out for a previous build, not using a turboprop,
http://www.modelairplanenews.com/blog/2 ... nd-wyvern/
gives an idea of the size etc.
Barrie

Thanks Barrie - I found a video of this one on Youtube but it's nice to have some tech' as well from the magazine source. A very impressive model indeed. I see he's neatly 'side-stepped' the contra-prop drive issue by making on of them a free-wheeling unit. I suspect he's not bothered with variable pitch (VP) either ! I spent this morning on some planetary gear designs and a simple VP unit based on helicopter principles. The challenge will be in making it light enough whilst still being able to constrain the inertial loads.

Dave, it may be worth having a word with Mike Murphy at Wren Turbines, he does build one off turboprops based on the 44 Gold engine, he is currently doing a heavy duty one for Steve Bishop to use at the shows.
Barrie

There was a superb scratchbuilt Bearcat bought by a member, if I recall correctly, and it appears in the WWII part of our gallery. That had a variable pitch constant speed airscrew. Perhaps some research on that one would provide some of the information you need? Good luck. Chris

Thanks Barrie and Chris. I will pursue these contacts when time permits. (I've just had a request for a painting of Jim Clark's Lotus 33 for a birthday present, so, will have to do some research on that asap !). Yes, the Bearcat is indeed a magnificent piece of model engineering. I think the designer/builder may have been Dutch. Coincidentally, I'm practicing with a Bearcat on my RC flight sim' at present - it's the nearest I can get to a Wyvern with the current version of the software...

If you'd like to get in touch with Dave Wigley, the builder of the 1/5 Wyvern mentioned above, let me know.......I've been in contact with him over the last few years as I've supplied parts for his current project.

e-mail me at - phil@fighteraces.co.uk

Phil

Hi Phil - thanks. I may well need to talk to him at some point. I think I saw an ad' for his plan somewhere ? Been discussing powertrain ideas with Wren Turbines this week. Am currently working on design ideas for the contra-prop gearbox and variable pitch units. If I were to go for 1/4 scale would you be able to supply any suitable parts ? Will email a 'wish-list' to you when things are a bit more advanced...

Hi dave

Drop me an e-mail to phil@fighteraces.co.uk and I'll pass on Dave Wigley's contact details.

Yes, there is a plan available via Model Airplane News in the US....as well as basic 3-views for the retracts

http://www.modelairplanenews.com/blog/2008/11/12/custom-made-retractable-landing-gear-for-the-westland-wyvern-s-4/

Regarding bits.....nothing specific to the Wyvern, but I'm sure we can help with various building & finishing materials (glass cloth, resin, paints etc...), wing tubes, retract air system accessories, control linkage items etc etc.

Cheers

Phil

All - thanks for the many contributions to this. My conclusion is that the project is feasible at 1/4 scale but will be very demanding of time, resources etc. and, I think a 3-5 year timescale may be necessary to sort out the detailed engineering issues. Progress so far includes an in-depth look at contra-gearboxes and variable pitch units. Today, I finished some first trials on a pair of (small-scale) o/d contra-props running co-axially in plain bearings. Next will be a mock-up of the planetary geartrain and the two prop control units (these will probably be in wood /plastic at this stage). There is some turbo-prop engine discussion on the "Jet" forum and I will add to this as appropriate. The hunt is now on for generating a set of 1/4 scale plans and drawings. Next move will be to join the LMA and get the project registered in the over 20Kg category !