Welcome, Kent! Looks like you've got a couple of nice built-up wings there. Also looks like you're well on your way. Unless you somehow scare the begeebies out of him in the process, once you take him up, the rest will be history!
Yes, we proud de-facto acolytes of Vishnu (Hindu God of preservation & restoration) salute you for taking on the salvation of that bird! I wonder what engine you have? It looks air cooled. The airplane was originally designed for the Cuyuna snowmobile engine, I think. The majority of us (I think) fly behind the liquid-cooled Rotax 582 engine. Of course yours, being the A model, has the motor mount as an integral part of the fuselage frame. In later models it separates at the firewall, and is held on with through bolts. Looks like you're in for an adventure!
Man, that V4 is compact! Dunno how one would go about setting it up in a cowling: bring the air in between the V and then out and down? Plugs come in from the sides! Very interesting although, like you say, not too practical!
JimChuk, your point is well taken. My bird is light and apparently clean, as I can easily top 80 mph at 5000 rpm, at low altitudes. And I'm not tightly constrained economically, so I can afford the petrol, as well as the other stuff. I suppose my fixation with minimum power stems from a desire to understand my bird's aerodynamic properties. Hey, I'm a retired airplane aerodynamicist, what can I say? Even this simple little putt-putt airplane is an object both magical and fascinating to me. I also see it as a vehicle for a new class of adventures that I can share with my wife, that are exciting, yet not too strenuous for our old bodies. This is in addition to serving as a testbed for various minor experiments. True, I can't turn it into a map-gobbling rocketship, but that's o.k.. Its ability to fly is all the magic it needs, as far as I'm concerned. It's the magnificent journey, not the boring destination! I already live in my flavor of paradise. Your kind words are always appreciated.
From what I've read, castor oil's film strength can't be beat, even by the best synthetics, but it does eventually morph into a gummy residue. I understand that certain types of off-road motorcycle racers still use it, since they disassemble at least part of the engine between races anyway. Smells cool too!
I have no intention of operating the engine outside its specified operational parameters. Any temp wanders outside the limits and it's experiment over. Calculations so far indicate feasibility if the airframe (excluding prop, as a glider) has a best L/D of just over 8. I remember being quoted 7:1 for a Cessna 150, but that is with a windmilling prop. Take that prop out of the picture, and it's likely 10 or more. I have already demonstrated level flight at low altitude at 4000 rpm, to no ill effect, with the prop pitch where it is. Close to best L/D the power requirement is low, and the prop doesn't need to provide very much thrust. In short, this is not lugging. It's more like loafing. Without the IFA, I'd need to take off with the pitch somewhat higher than it is now. This means a longer takeoff roll and a flatter climb, at lower rate, but higher forward speed. I already do this. The feasibility can be estimated, and the goal approached incrementally, in recognition of the limitations inherent in my modelling of the prop's behavior with my code. In the pursuit of cruise economy, I intend to map the tradeoff against climb rate anyway. I am not proposing to fry my engine. I'm an old guy, so I do things cautiously. It's an experimental airplane. Experimentation is expected, one would think.
Tell you what, fellas. I'll only play this low-power game in the pattern or out in the flatlands, where the consequences of engine failure are mitigated. No trees in sight. Just harvested wheat fields. And like I said, I'll put her "on the bit" once in a while just to keep it clean. But first I'll see if I theoretically even have a big enough prop to make it work. Just a matter of a few well-thought-out runs thru my prop code.
Point taken. I live in a high-humidity area, so have made the decision not to go with the true synthetic oils, like Amsoil Interceptor, despite their excellent lubrication performance. My big concern is engine corrosion when the airplane is sitting, and from what I've read, in that regard I'm better off with more conventional "mineral" oils. Locally, I can get a relatively inexpensive TC-W3 oil that's also rated API-TC, and is hence ashless, so that's what I'm going with. Chris Bolkan reported good results with a similar oil type. I'm hopeful that the oil injection system throttling the oil back to 70:1 at idle will spare me some crudding-up there. On cool days I have been able to hold (low) altitude at 4000 rpm, but I see that engine thermal efficiency peak of 34% at 3500 rpm, so am curious as to what I can get away with. I suppose it's really more of an academic question, not particularly useful operationally. But you're saying the new synthetics do a better job with rust protection than earlier versions? Interesting. Best of luck with that Hirth!
I've got to believe this is very dependent on the type and size of the engine. Nobody else has contested the notion that these engines like to operate under load, and that their fuel efficiency is highest, and EGT lowest when loaded. At 3500 rpm we are out of the gear-train resonance; we're out of that regime by 2500 rpm. The 582 is liquid cooled, so kept warm by a thermostat, even if engine heat generation is way lower than the radiator can dissipate. Leni's right that cabin heating may be insufficient for comfort. Unless one's midrange needles are set up wrong, resulting in the engine running lean, I don't see anything damaging to the engine here, except perhaps in really cold conditions where even the thermostat can't keep the engine above the minimum coolant temp, causing crud to build up in the combustion chambers, and risking seisure. Except for the very cold OAT case, I see little harm potential here. I would think this would be very easy on the engine.
Maybe that's the problem. I taught myself to sail before the wide boards showed up. I even had a speed needle for a while. Not quite red-shift relativistic fast, but it was still scary fast, and lots of fun. But that was before I moved to the Gorge and learned what fast really is. Seriously, though, I get the obvious benefits of a wide-track gear, especially to be able to not damage your wings in a bad groundloop, but I am now convinced that it's the way the LG pivots about their attachment to the fuselage sides, with initially more outward motion of the tires than vertical motion, that is the major contributor to the narrower gear feeling squirrely. Ironically, this same motion should make a tricycle-gear setup feel more benign and stable, but in either case, hard landings are sure to chew up your tires!
C.D., I b'lieve you're onto something! Based on my prop calculations, and the factory data, with my light, clean little bird, the shaft power required to fly level at low altitude is less than what the engine can produce at 3500 rpm. Of course, I would need the IFA to pull it off. And hopefully the prop efficiency won't tank at the higher pitch! But the words of experience say I'd better not try to do it for long, or my engine will crud up. Got to put the bit in her teeth at least every so often. O.k. then!
Interesting that the low-speed, skidding turn (too much rudder) is the dangerous one. It must be the wonked fuselage's wake that helps the underpriveleged, higher-AOA Inside wing to let go first. Accelerated stalls happen above rectilinear stall speed, and turns involve centripital acceleration, and pulling some Gs, as we all know. This is the classic spin entry that seems to kill so many pilots when maneuvering for landing. Slips, on the other hand, are relatively safe. This is good, especially when landing in crosswinds. Cool that you can bank, yet stop the turn with rudder, allowing you to slide sideways without actually pointing in the direction you're going! Then, you're even safe to stall this way! Aren't airplanes cool?
Maybe it's the combo of the two. As a swerve initiates, weight shifts to the tire on the outside of the swerve. The gear leg on that side squats in response to the increased load, shoving the tire on that side outward. Since that tire now is carrying more load, its firmer grip on the pavement makes this really manifest as shoving the airplane in the direction of the initial swerve, exacerbating the swerve. A wider track lessens the weight transfer. A suspension that does not shove the tire outboard when it squats might not have this problem at all. Hmmmmm... Thoughts, guys? The guy who sold me my bird advocated for 10 psi for the Carlisles. I see that this, in addition to the mercy of a little lateral squishiness, makes the tires a more significant part of the suspension. Of course tight new bungees have got to help too.
Interesting! For sure that's a lot more rotational inertia! Definitely something to consider. One thing some folks are saying that mystifies me is the degree to which wider gear stabilizes the airplane on the ground. Other than less roll to the outside of a ground turn, and less sideways movement of the tires when the gear squats on hard landings, I don't get it at all! The CG is still behind the mains, so the propensity to groundloop can't be that different. What physics tidbit am I missing?
Thanks, JimChuk. I guess even an L/D of, say, 1/2 is a whole lot better than zero! Lots of guys favor those monster tires, bigger than our golf-cart Carlisles! These have got to be draggier, but even the Carlisles are draggy. So I guess Leni is saying that he sees little benefit for the IFA prop, outside of floatplane ops.
Es buen consejo. That's exactly where I'm at. Just putting around, visiting friends, making new ones, enjoying the scenery. Tailwind? Fly slow and let God do the work. Headwind? Crank up that overstuffed chainsaw, and scream your way along. These engines are generally regarded as robust, if flown right. But sure, ya gotta know how to not murder them, as it may decide to take you along with it. As Allen pointed out, even lycosaurs are vulnerable to being murdered. My bird has the bellyrad, wheel pants, and an IVO prop. The bellyrad partially shields the unfaired LG struts just behind, tucked up against the belly. According to my prop code, the IVO in cruise produces no thrust at all from the inner 1/3 to 1/2 of the blade radius. In fact, the inboard sections act as an inefficient windmill to help turn the prop so the outboard sections can produce thrust. This may sound bad, but also doesn't add propwash to magnify the drags of excresences near the fuselage, in fact those contributions to drag might even be diminished. The bird feels slippery to me, and I know I can improve it. This is a great toy to play with, both in the shop and in the sky. We are so lucky to have such fine toys! Gotta love it!
Thanks for that advice, Leni. I do have a leaning setup on my engine, basically a copy of Cowlove's approach, using a small, 12V diaphragm vacuum pump to lower float-bowl pressure. I have a rheostat knob on my dash labelled "chemtrails", that energizes the tiny vac pump. Pump-off, it reverts to ambient. So far I have not done anything but pattern flying, trying to wire my landings before my highly critical wife climbs aboard. I have only used the leaning circuit to shut the engine down, and to smooth the idle in summer when DA is high.. Regarding the IFA, any extra weight on the schnozz is to be avoided, as I'm clear my bird is noseheavy already. And I just reinstalled the OI system & oil tank. $1000 more in my pocket is good too. Like I mentioned earlier, my next step will be to investigate what might be the best prop pitch for how I fly the bird, which currently is verrry conservatively, and mostly from tarmac. If you don't use IFA, maybe it's due to the skis' drag hit? I would, however, assume that floats are draggy too, and that both argue against the IFA, since lower L/D tends to require the engine to work harder at a given flight speed. But I get it: water takeoffs were a bitch without it! I have only the single, 14 gal tank, and am, in my old age bladder-limited, so I think I have the right setup. Not trying to re-invent the wheel; just trying to work things out for what I think will be my kind of flying.
So, what's the weak link here in this non-screaming-meemie scenario? Would I be lugging the engine? Overstressing the conrod bearings? Or would I just be running it so cold that it would crud up in short order? Or have a seisure? Clearly if I'm trying to actually go someplace I'd need to spin it up a bit more. Spun up, it sounds cool, like a turbine engine. I'm just thought-exploring the max endurance scenario. The IFA, behind a 4-stroke, I agree, is more the provence of the faster bird. The sensitivity of this 2-stroke to oversped, low-throttle conditions, not to mention the hit in fuel consumption, seems to change the rules a bit. A class-3 medical is $100 and a pair of glasses away. Glasses are on order. Booga-booga! Note that at least two of our most experienced members fly with the IFA. Just sayin'
Thanks, Chris. Here I can get an API-TCW3 oil that's also rated API-TC relatively cheaply. Since it is devoid of solids, and apparently they are not needed since our engines are liquid cooled and don't seem to run that hot anyway, I think I will go that route. Did you find it necessary to pull the pistons in order to clean out the ring grooves? If so I'll eventually need to get the roller keeper tool. I'm really contemplating getting the pistons ceramic coated on top first opportunity. Has anyone used an ultrasonic cleaner for the pistons?
Such a deal! Doesn't that engine have a different cylinder material that grows/shrinks closer to the aluminum piston thermally? Is this similar to the kind of silicon alloy aluminum used on the Chevy Vega? After they worked out the metallurgy my understanding is that it proved quite durable. It'll be interesting to see how things go for you, departing the golden path as is were. And no coolant to leak!
For sure, that nosebleed climb could save a fool's life getting out of a box canyon some day! Now I'm wondering if with an IFA on front it might be possible to float about the sky at the 582's efficiency peak at 3500 rpm! With my fixed-pitch where it is, my prop calculation estimates that the prop's absorbing about 20 hp at somewhere close to 80 mph in level flight. Just a thought. I also think Leni makes a good point regarding keeping things clean in the upper cylinder, piston tops, and especially rings. I just installed a fuel totalizer, and I'm keen to find out where the airplane is happiest, and what altitudes & airspeeds to shoot for to maximize range. Then there's the issue of headwinds/tailwinds. Please pardon me for waxing nerdy here, it goes with the territory! Hey, let's hear it for lunch money!
For what It's worth, I translated the brochure Rotax data into a form perhaps more understandable to those of us who are not fully into the metric system as yet. The power vs. RPM curve labelled "Propeller Curve" was initially a bit of a mystery to me, but ultimately seeing how it differed substantially from certain of my prop calculations, for conditions I have flown, I have decided it represents the maximum power available from the engine at a given RPM. The thermal efficiency plot is interesting. Many years ago in engineering school we were told that car engines are only about 25% efficient overall. Although I'm sure that number has improved substantially since then, I was surprised that the 582, a lowly 2-stroke, did so well. So here they are. Enjoy!
Great points! You Alaskans impress the hell out of me! Down here at 46 deg N, I'm not flying. Too cold! Maybe after I finish installing a heating system... One thing that I forgot to include in my long-winded discourse is the issue of ignition timing. 4-strokes, at least the more sophisticated ones, feature some combination of vacuum and centrifugal spark advance. Both are aimed at advancing the start of the combustion event as the engine speeds up, and/or intake manifold absolute pressure is reduced. With the 2-stroke, things get complicated, and exhaust- system scavenging tends to drive the advance curve, often actually retarding the spark under these same conditions. With the 582 the exhaust system is de-tuned for a more even power band, and the engine has no spark advance mechanism at all! In either case, with a 2-stroke, we're stuck with essentially the same problem with high-speed, part-throttle operation.
Allen, Having four cylinders vs. the two of the 582 should provide a little mercy, but I would agree: the principles are the same. I wonder if 4-strokes see any EGT rise under part-throttle overspeed conditions? One would think this could be hard on exhaust valves! Perhaps it's effectively masked (or overwhelmed) by continued cylinder cooling prior to and during the exhaust stroke.