IBob

As I recall, he also kept a small camp stove under his hat, complete with warm hamburger.......

Also know as the 'Wimpy', after the character J Wellington Wimpy in the Popeye comic strips.

Okay. There have certainly been efficiency improvements in things like big industrial fans in recent years (though traditionally many of those were horribly crude in design). So I can entertain the idea of improved/more efficient prop design. What I am struggling with is JG's tests which, simply put, suggest that for a given engine power output, there is very little difference in the performance from various (same diameter) props. Assuming, that is, that I am understanding him correctly.

So, you're saying that aircraft are climbing faster/flying faster etc without any increase in fuel consumption?

If that is the case, Mark, there would seem to be two possible explanations (or a a combination of the two): 1. The Eprop is more efficient in converting engine power into thrust. 2. The engine is working harder, delivering increased power at a given RPM, when fitted with the Eprop. It ought to be possible to determine if it's #2 by comparing before and after fuel consumption?

Ah, I think I've got it: forward thrust generated by the blade would tend to tilt the blade forward on the hub...but this is offset by the counterweight, which will tend to track around a max possible diameter, which is the plane perpendicular to the hub. That suggests that, in flight, the blade is tilted a little forward of the hub, rotating as a sort of cone shape, rather than a flat disk......

You raise an interesting question, Skippy. It does seem, from tests carried out, that a whole variety of blade shapes will give much the same result for a given engine power setting. (Which is not the same as saying they give a similar result at the same RPM, a point that JG here tries very hard to get across.) However, discussions round this generally seem to devolve into 'well I took off prop Y and put on prop Z and it works better, so prop Z must be better'. Which doesn't line up with test results. So I guess you take your pick: free lunch or no free lunch???

Would not the rotating centre of thrust impart a corkscrew motion to the nose of the engine/aircraft (requiring reinforcement of bearings and mounts)?

Just a detail: The Savannah VG was introduced in 2004. The XL (rework from cockpit forward, larger cockpit, longer nose etc) in 2009. The S (rework of the rear fuselage, from slab sided to more rounded) in 2010. Having said that, agents tend to buy kits in batches, and there is a variable period between the kit being boxed up in Italy, and the final customer receiving it. Eg My S kit was boxed up Dec 2014, I received it (in NZ, from Australia) Nov 2015. The kit date will be on the Statement of Compliance, which should be in the front of the manual. Also: are you able to get a Savannah builder to look it over, to get some idea of the quality of the build? Hope it works out for you, it's a great little aircraft. Be sure to post pics!

The kit comes with a pneumatic rivet gun, OME. And a belt driven compressor (rather than a direct-drive screamer) is definitely the way to go..........)

Etc.............

OME the Savannah is put together with pop or blind rivets, not solid rivets. There are some solid rivets (at cockpit sides and main spar) but that is all done at the factory.

There's been lots of discussion around this on other threads. While countersinking into thin sheet is not ideal, it is what the Savannah manual calls for. 1. As I see it, the reason it is acceptable in this case is that the there are very few countersink holes, and they are not 'structural': they are mostly used for holding things like nutplates in place, where the final load will be taken by the nutplate at the rear of the sheet, not by the countersunk rivet. Consider also that, while dimpling may produce a nice countersink, your nutplate will not then sit flush to the back of the sheet. As it needs to do to be properly tightened. 2. However, countersinking with an ordinary drill often does not always produce a tidy result: the bit tends to wander in the hole. As noted by Kasper above, you really need a proper countersink drill, which has a central spigot that holds the drill centered. 3. The angle required to match the rivets is 120deg. I have several drill sets that are not 120degree, but my Bosch set is. 4. If I was building again, I would cut, not dimple, but I would source the correct countersink tool from AircraftSpruce. They are expensive in sets, but you don't need the set, you just need the ones for the A4 and A5 rivets. Just be sure you specify 120deg. Finally, consider that thousands of Savannahs have been built according to the instructions in the manual, and are flying just fine. That suggests to me that the instructions in the manual may be followed with confidence. There is a huge amount of Savannah info on this site to help you. All the best, and don't forget to post pics of your progress for us to enjoy!

Further to the above, I just came across the part number for the large red flashing LEDs I used for my low fuel indicators. I have them on L and R of the panel (connected in parallel) and they work well. For anyone who may be interested, they are RS Components, RS Stock No: 209-119 NZ$8 each

There's a SA outfit with a lot of SAV and 701 experience, have posted some interesting comparative stuff. And I believe their 701 guy ended up putting Sav stab/elevator on his 701.

I should add that this makes for a very unsophisticated leaning system, in that any change in throttle setting alters the manifold suction, which then alters and upsets the fuel leaning, resulting in rough running and possibly even stoppages. Manufacturers of one such system I saw state that the mixture must be set (back) to full rich before any changes in throttle setting.

Correction to my statement above: On further reading it seems the carburettor vents do also provide a drain function in the event that the floats fail, reducing carburettor flooding and allowing the engine to continue running (albeit very roughly) rather than stopping the engine. The Sav has the vents plumbed to the airbox, after the air filter, with a separate drain line from the bottom of the airbox venting to atmosphere below the cowling. Where there is no airbox, common practise seems to be to attach short hoses to the carb vents, and tuck these under the float bowl clips.

FWIW, I believe it is the pressure on those vent lines that is lowered when a fuel leaning system is added to this engine...and that is done by introducing a small amount of vacuum taken from the balance pipe after the carbs (but before the engine).

I may have this wrong, but: I'm pretty sure his problems started with his assumption those are drain tubes (and he's still thinking that and calling them drain tubes). My understanding is they are nothing of the sort: They should be connected to wherever the carb is drawing it's air from, their function being to ensure that the float chamber is at the same pressure as the incoming air. (So, for instance, if you have an airbox with a filter, they are connected to the airbox but after the filter.) Put them anywhere else and you'll get exactly the sort of behaviour he's talking about, as the float chamber is then running at a pressure higher or lower than the carb air, resulting in rich or lean mixture. Feel free to straighten me out if I haven't got this right.

Yep, Marty. I tried a brush, then a little speed brush, and of course they push the black stuff through the rivet holes. Then I switched to a sprayed primer, but if I was building again, I would definitely reconsider the black stuff (that comes with the Sav kit) and one of those rollers. I don't think they're available at this end of the globe now, but they still seem to be available in the UK, and would definitely be worth getting. Having said that, the black stuff is a water based primer, and so not fast drying on brushes or rollers. It seems to me a roller setup would probably go hard pretty quick with spirit based primers...

Roller for the black stuff: Paint Buddy Roller

I didn't use the black stuff, I sprayed a primer. However, for another build I would definitely reconsider the black stuff. The Australians apply it with a small self-wetting roller (can't remember the name, but there will be references to it here somewhere, the black stuff goes in the handle) which gives an even application and perhaps also limits buildup in the rivet holes.

Rmorton, my experience of the Savannah build was that 99.99% of it went together as per the manual and diagrams, and for the other 0.01% I never reached for the drill: when you open holes with a drill, you risk shifting the alignment of the parts and also weakening the join. As suggested earlier, you do however need properly fitted, polished, tapered podgers, and where a part needs working into place, you usually need at least 2 of them (so that you can walk them along or round a series of holes). They need to fit properly to align the holes without damaging them, and they need to be polished so that they do not bind in the hole. They are easily bought as awls, or made from cheap pin punches, sanded to a taper then polished with fine emery. There is also an order of podgering/clekoing for some parts: try to attach them in one order, they will not go, try them from the opposite side or end and they come together. So where something will not come together, it is worth trying different orders of podgering/clekoing. Where I trimmed metal (and there was almost none of this) it was only where it could be done without weakening the part or the join. So, for instance, any internal corners were made with a drill to reduce the possibility of cracking. .................................................................................................. My main suggestion to you is to resist the urge to change the design when faced with a problem: So, don't move the holes mounting the steel undercarriage and strut brackets; instead, find out why they won't fit and how that can be remedied. And now, don't move the two shims between the brackets and the channel (which are also riveted into the channel, and so are more than shims): keep working at it to get them where the design calls for them to be.

And PS to the above. Why it is a really bad idea to be moving holes, effectively moving the steel part at this location: 1. It houses and mounts the undercarriage, and so defines the angle of the undercarriage sits at. 2. It is the attachment point for the wing struts, so any small movement will affect wing dihedral.

Rmorton, I have a suggestion for you before you start moving holes at such a critical location: Take an accurate pattern of the holes from the steel part: to do this you will need stiff paper/thin card, cut into a 'C' to fit round the part. Then see how the holes of this pattern line up with the holes in the fuse side. I suggest this because my own initial difficulty with these parts had nothing to do with the position of the bolt and rivet holes (which, like yours, would not line up). The reason was that the steel part was fouling the sides of the rectangular hole in the fuse side. Once I remedied that (as per the pics) the parts fitted quite easily.