Rizon Posted September 30, 2015 Share Posted September 30, 2015 Let’s give this What If thing a try….. I am not a What If builder at all, so this is something new for me. However, my (late) entry is based on a study if it could be done – converting a Grumman Widgeon to turbine power. Most of Grumman’s amphibian models have been converted to turbine power; the Goose, Mallard and Albatross come to mind. The Widgeon being the smallest though makes a bit of a challenge, as Turbines in that power range are not all that common. On the low end of the spectrum are the PT6A and Walter 610 engines as options, that are usually used for that purpose. Both are about 3 times as powerful as the original piston engines installed. But then again, it is all about more power…. Converting an aircraft from piston to turbine is not all that simple as replacing the engine. Balance is an obvious problem, but there are control and power effect problems that need to be considered as well. The concept that I came up with is this: Stretch the fuselage ahead of the wing to make up for the slightly lighter engines, but also stretch the rear fuselage a bit – to increase control authority of the tail feathers. Or increase the “tail volume” as it is technically called. The trick is finding a balance between the two. Increasing the tail authority is required due to the increased power, to allow controlled flight with one engine out and to also counteract the now increased aerodynamic forces the extended nose will give. Also a fin root extension will be given for the latter reason to help in cross wind landings. The engine nacelles have to be extended a bit to fit the turbine engines. And also to keep the prop discs ahead of the flight crew stations in the now extended front fuselage. To start off with, first some calculations: I created a simple 3D numerical model of the fuselage that could be stretched at arbitrary points. The resulting moment generated by the new fuselage and relocated engines was calculated and compared to the original intended moment around the wing. I played around with these variables till I found a solution that I was happy with. See the picture below that compares the original (short) fuselage to the new extended one. Front extension is 1.00 metres and the rear extension is 0.4 metres. That together with the slightly lighter engines on an 0.65 metre extension give a balance around the original balance point. Then for the kit: I had this old Airfix kit lying around, built many, many Moons ago and in a sorry state. It was used as a paint test bed and then forgotten. First thing I did was give it the brake fluid treatment to get rid of the thick layers of paint and dissolve the glue joints. Here the parts after the treatment: Next up is cutting the fuselage on the stations where the extension pieces will fit. R 1 Link to comment Share on other sites More sharing options...
heloman1 Posted September 30, 2015 Share Posted September 30, 2015 Interesting concept R, I'll follow your build with interest. Colin Link to comment Share on other sites More sharing options...
Col. Posted September 30, 2015 Share Posted September 30, 2015 You're putting a good deal of thought into this one Rizon. It promises to be an interesting project 1 Link to comment Share on other sites More sharing options...
dpm1did1 Posted September 30, 2015 Share Posted September 30, 2015 So I'm not the only one planning on Wiffing a classic waterbird...jolly good show! Link to comment Share on other sites More sharing options...
Rizon Posted October 1, 2015 Author Share Posted October 1, 2015 Fuselage cut and extended. Front extension was first held into place with a bit of sprue. Then the skin was added. For the rear I only uses sheet styrene to form the extension. I also intend on converting the Widgeon to a tricycle undercarriage, just to make taxing easier. For this I moved the main gear wells backwards to just before the hull step. How feasible it is in real life to change the structure like that I do not know, but lets do that regardless. R 3 Link to comment Share on other sites More sharing options...
Rizon Posted October 2, 2015 Author Share Posted October 2, 2015 Next up was adding the side windows. Airfix somehow managed to sculpt the windows, including the windshield as something looking more like gun ports on a fortress, not like something to have a look see from... Very simple construction: a strip of clear styrene, some strip styrene glued around it, and presto the larger windows are done. One extra window added though for the front fuselage extension. Also tried out my home made rivet scriber for the first time. The cog wheel I recovered from a 40mm Fuze and had an approximately correct pitch for use in 1/72. I didn't re-scribe panel lines. Don't plan to either - some pictures of the real Widgeon show that it actually has RAISED panel lines. Guess maybe that is due to the joints being folded over or something like that to make them waterproof....? R 3 Link to comment Share on other sites More sharing options...
heloman1 Posted October 2, 2015 Share Posted October 2, 2015 Coming along nicely... Colin Link to comment Share on other sites More sharing options...
dpm1did1 Posted October 2, 2015 Share Posted October 2, 2015 Progressing well...and quicker than my Walrus. Didn't think about about a tricycle conversion although i don't plan a stretch so not sure it would fit a 'real' airframe. Link to comment Share on other sites More sharing options...
Rizon Posted October 8, 2015 Author Share Posted October 8, 2015 Work continuing on the fuselage; I removed the rudder and the elevators. Simply for the fact that removing them and gluing them on again makes for a convincing hinge line.... And then the engine cowlings. These were made from the original cowlings as a base. A bit of styrene tubing, flattened at one end, forms the intake which is added to the bottom side of the cowling. And the extension is made from a suitable diameter tubing, with part of the old cowling attached to the bottom to give the elliptical cross-section. And it all assembled, with final shaping still to be completed. R 2 Link to comment Share on other sites More sharing options...
Rizon Posted October 16, 2015 Author Share Posted October 16, 2015 Brief update: Engine cowlings are done. Also applied some primer to them to check for surface imperfections etc... Small bits and pieces done on the other parts, but nothing yet worthwhile of reporting. R 4 Link to comment Share on other sites More sharing options...
heloman1 Posted October 16, 2015 Share Posted October 16, 2015 Nice work on the engines. Colin Link to comment Share on other sites More sharing options...
Rizon Posted November 5, 2015 Author Share Posted November 5, 2015 To date I have done a vacuform of the windscreen - using the original parts as the master. Came out quite well. That was then positioned on the fuselage and held in place using cyno. The still open cabin helped to reduce fogging and the little bit that did occur could be easily removed. And then the wings. I removed the ailerons and flaps - the flaps themselves will be modified a bit. And added winglets/rakelets. The objective here is to increase the effective aspect ratio of the wing. The real Widgeon seems to have the wings removable from the engines outboard - so it could be quite plausible the to have the entire outboard wings replaced, if metal fatigue is an issue on the donor airframe. Also that allows the application of a potentially more efficient airfoil and the inclusion of wing fuel tanks. From what I gather, the net volume of the Widgeon's fuel tanks is a bit small, so this might indeed be a necessary modification.... And then temporarily holding everything together. The aircraft is taking shape: R 5 Link to comment Share on other sites More sharing options...
Dermo245 Posted November 7, 2015 Share Posted November 7, 2015 This looks more 'When' than 'What if' - great stuff and love the work on the engines. Dermot 1 Link to comment Share on other sites More sharing options...
Rizon Posted November 23, 2015 Author Share Posted November 23, 2015 With the deadlines coming down like a tonne of bricks.... ....not just for the Group Build, but also at work.... this is all I managed lately: adding the flaps and ailerons to the wing: R 1 Link to comment Share on other sites More sharing options...
JOCKNEY Posted November 24, 2015 Share Posted November 24, 2015 Amazing work, especially the attention to detail, keep going ! Cheers Pat Link to comment Share on other sites More sharing options...
Rizon Posted November 30, 2015 Author Share Posted November 30, 2015 Yet another deadline that came woooshing past... Anyway, this is where I was when I closed up shop last night: Fuselage mostly done and masked. First it got a layer of primer, bit of refining and lastly the first coat of white. All from a rattle can bought at the hardware store. This is a bit of an experiment if it is useful to use normal commercial rattle can paint. Still in two minds about it. So here the fuselage in white. I promise it is white, not grey, white balance is just off... When and if I ever finish this one, I'll post some pictures in the RFI section of the Aircraft Modeling section. One day.... R 3 Link to comment Share on other sites More sharing options...
Col. Posted November 30, 2015 Share Posted November 30, 2015 Please finish this one. It looks great already and will be fantastic once completed. Link to comment Share on other sites More sharing options...
davecov Posted November 30, 2015 Share Posted November 30, 2015 Coming on nicely. Hope you have replacement main u/c legs as those supplied in the kit can't take the weight of themselves, let along the rest of the plane. Dave Link to comment Share on other sites More sharing options...
Recommended Posts