Markdun

Bruce, the 'bluesmoke meltdown' was in a friend's plane I was delivering. It had a rather large and very heavy lead battery with the original Jabiru/Kubota voltage regulator. There was no fuse in either the AC side of the regulator nor the DC side. (And I might add, despite being previously VH registered there is no main battery fuse either) The aircraft had both an ammeter and voltmeter and a toggle switch that could open circuit the DC side of the alternator (ie. you could switch off battery charging). In my familiarisation flights I found the voltage was creeping up to 16V as indicated on an anologue gauge (auto quality). The aircraft had a good avionics panel, transponder artificial horizon, turn & bank etc..almost IFR, but no glass EFIS/EMS. Being worried about damaging the electronics & the battery I thought it wise to turn off the charging whenever the voltage increased to 16V and to turn it back on when the voltage dropped to below 12.5V. Not a big task as the battery was huge...maybe it needed about 5 minutes every hour. However, I have subsequently read a Jabiru advisory that it is possible to exceed the current capacity of the alternator at high rpm with a voltage regulator failure and a battery that will absorb a heavy charge current. Their advice on noticing a regulator failure is to isolate the charging circuit and land and replace the regulator. The approach we have now taken is to install the Powermate regulator which should limit the voltage to 14.2 and current to 8A and to install a 15A auto fuse on the AC side of the regulator (plus a lot of re-wiring as well). This means if the regulator fails, at most you are up for the cost of a new regulator plus a 50c fuse, and not have to contemplate rewinding the jab stator or buying a new one for $500. And more importantly you will not get molten copper dripping onto your carburettor. This is all a bit off topic though. My understanding is that the lithium batteries like the SSB are able to deliver heaps of current for little voltage drop, and so can crank an engine really well, right up to the point of total discharge. However, the electronic battery management system does not tolerate high charging currents...so if you do substantially discharge one, you can damage it by charging with a standard lead acid battery charger/regulator and particularly by 'jumper' connecting it to a charged lead battery or running car's battery. I'm no expert in this, but this is what the battery suppliers say. I think my Lithiumax 400 battery has a maximum charge current of 8A, but it easily delivers 60A plus to crank the Jabbie 2200...real fast. So the one downside of the Lithium batteries are no jump starting.

I'm not sure that problem is limited to lithium batteries. ...plenty of cases of melted alternator windings and escaping blue smoke (blue smoke is the thing that makes all electronics work) from Jabs with lead batteries. I'm now a firm believer in having a fuse/circuit bre a ker in the AC side of the Jab alternator after experiencing blue smoke in the cockpit and then a subsequent ground inspection showing molten copper dripping around the carb...with a lead battery - & the failure was the voltage regulator, not the battery, nor the alternator.

I've had one in my Jab powered aeroplane for 2 years. It weighs almost nothing. Still going well. Really cranks the engine fast even on minus 5C days. I did put in a Powermate regulator because of a negative voltage spike isdue that resulted in weird fuel flow numbers on my EFIS/EMS based on advice from the EFIS people who said they had a few issues with Jab regulators. Previously the bus voltage at cruise settled at 14.2V but now it's 13.7V. I can't tell the difference other than reading the voltage numbers onnthe EFIS. All works well.

Yes Bill. I ran an Bing 64/32 CV carb for 700 hours or so on my 1835VW which I scavanged off an old BMW R100 boxer, but replaced it with a Rotec 34mm diaphram carb (its not really an injector). The engine started easier with the Rotec (hand start) as it has a primer function, and I easily got another 100rpm on full throttle. And of course it had mixture control, though I never used it. ...I just left it at full rich. My set up used gravity feed. The Rotec also gave better EGT spread. I've now installed it on Jab motor. Cheers, Mark

It's actually a vapour return line from a header tank (about 2l) mounted on the aft side of the firewall... the VW installation was gravity fuel flow. But the line can be used as a fuel level check. ...my plane also has a translucent epoxy/glass window in the fuel tank and a sight tube on the tank....and a calibrated fuel flow meter for a computed fuel remaining. You can never be too sure on fuel reserves. Mark

Visibility is fantastic. Compared to a Tecnam Bravo, Jabiru or a low wing, Cessnas etc its just tickety boo. On the ground and in the air the visibility is good.....the nose and dash are low, so superb fwd and down. Side windows allow visibility above and under the wings. Bubble glasshouse means up and to the rear up is good. Only blind spots are directly down and down towards the rear. I've never found the shoulder wing an issue. Checking out landing areas doesn't require a roll like is needed in many low wing aeroplanes, and its not difficult to check for aircraft on finals when taking off (unlike many high wing aeroplanes). Handling is very docile; roll is not fast, and the long fuselage means its not twitchy on elevator. Friese ailerons means you don't need big input on the rudder. No flaps, but she sideslips super well for glidepath control. Also it has pIsitive stability. ..you can fly hands off and while a thermal may give you a bump, it settles back down. Matt, I find your fuel burn at cruise difficult to accept. Do you just divide your added fuel by your Hobbs hours, and therefore include climb, warm-up and descent? My numbers are from a calibrated fuel flow meter, and with the 1835 VW and with two people on board I was getting 16.5 lph @ 75-80kts and rpm say 3100 and this was with egts around 650C, so it wasn't running rich. Here's a pic of my planes.

Matt, I built and still own a Cygnet here in Australia. It first flew in 2000 and had about 750 hours, nearly all of that with an 1835VW engine with a shrink fit prop hub, a single vertex magneto and a Bing cv32mm carb removed from a bmw r100 motor bike. The prop i carved myself (58 x 32) and it was a tad smaller than Bert's suggestion to get the rpm over 3000 at my elevation. Hand start. My empty weight was 245kg and performance was pretty much as per Bert's, though climb with a full load on a hot day was probably around 200fpm. It now has a Jabiru 2200 and I now cruise at 92kts @ 15lph. Cheers, Mark

We came East in a Tecnam in Jan 2017. It was a delivery and we didn't have experience of the plane's fuel burn/speed. 100 litres fuel, 20lph @ 100-110kts. Northam-Kalgoolie-Forrest-Border Village-Ceduna-Port Augusta-Mildura-Hay-Goulburn. Most nervous leg fuel wise was Kal to Forrest. Lots of strips to land on next to the railway line, but you would need to wait a long time for fuel (maybe weeks). We had a fall back option if fuel burn was more than expected to cut across to the coast. In the end we laneat Forrest with 30 litres in the tanks. Most expensive fuel was at Border Village (and the roughest strip). Best and friendliest service by a very long shot was at Forrest. Plane hangered for the night, lunch delivered, and a fantastic evening with the hosts and some fellow aviators, well lubricated by wine. Forrest really is a must stop-over.

Here's my two bobs worth. I've been to 4 Narromine fly-ins and 2 at Temora, flying my Minimax, Cygnet or in a Thruster. I went for the flying there; to have a sticky at other planes, particularly homebuilts for ideas and to see how others had overcome tricky or not so tricky problems; to fly in different planes and to take people for a fly in my plane (obviously not the Minimax); to meet people and socialise and in the evening to tell and listen to lies, mostly about flying, over 1 maybe 2, 3 or 4 alcoholic drinks in evening. I didn't go to be hectored, berated and lectured at about safety (I'm from the tribe that reckon flying in small planes is bloody dangerous and its just pissing into the wind to think otherwise). And I didn't go to Narromine last year because it was unclear to me whether it was a fly-in or not...it was billed as an 'airshow' with heavy fast aircraft, there was no information about camping under the wing etc etc, and it was even unclear it was a RAA event. By the time i learnt otherwise i had made other plans. I'd be keen to fly in to Cessnock, but the interest pull is not that strong if it's just a bunch of commercial shops without lots of interesting (homebuilt or unique) planes. Jabs & Tecnams are great planes but I'm not that keen to look at 20 of them that are all much the same.

I too have built and flown a low wing Minimax, but with a 1/2VW engine. It had zero washout as per the plans and CoG was in the mid range. The aircraft was at the designed empty weight. The plane was easy and a joy to fly and was very forgiving, but being open cockpit it was bloody cold and one got wind burnt on any cross-country. My Minimax had over 30l in additional fuel in wing tanks (& when full made climbs kinda slow, or more accurately slower than the already slow climb rate), an 'Occy' strap trim on the control stick, and it cruised around 60 kts (65kts if you porpoised). It did climb like a rat up a drainpipe in a thermal. ...Stall speed around 20kts! It definitely fitted the bill of maximum fun, minimum cost (pity ra-aus didn't stick to this ethos).

Nope. I still fly homebuilts and don't trust planes that are built by hundreds of cheapest tenderers. Jeez, they are just engine failures that require an outlanding. What's the problem? It would be a while lot different for an aeroplane with say a stall speed over 50kts and a mass greater than a 1000kg (all that kinetic energy to dissipate), or an on board fire, control circuit or structural failure. What's a Lyc and Conty? I havnt seen those. Are they two strokes, or copies of Jabiru or VW conversions?

Well I've had six. First was in a glider when the thermals stopped on the way back to our strip in NZ. At 400' i could see my chosen outlanding paddock had a fence, so then a fallback was a school oval (150m long and over power lines). Greased it in. Second was a head bolt failure in a 1/2vw powered single seater on takeoff at around 100'...landed straight ahead weaving between trees. No real time to do anything but fly the plane. Third and forth in the same plane (broken rocker bolt and the crankshaft) at altitude. Stall speed of that plane was around 20kts, so basically it could be landed on any cleared ground, of say 40m, as long as the approach was clear. If any long grass you had to stall just above the grass, and it would plonk down and not flip (tail dragger of-course). Last two were both prop bolt related in a homebuilt. Had to land in a rape seed paddock after shutting motor off due to vibration. Biggest issue was having to explain numerous times in the pub while we were waiting for a lift home why we had a prop with us. Last one the prop departed just after i joined base after i had pulled the motor to idle due to vibration. I made a bad decision to continue with my planned landing rather than land in a paddock straight ahead with fences, was far too low and was reconciled with having to land in a forested creek about 150m short of the runway. Somehow we got over the creek (due to wind gradient), one wing touched some leaves, i then held off about 10' above 3m high scrub, but stalled onto them a bit short of the strip. The plane came to a sudden stop...Definitely no skidding. Damage was: undercarriage ripped off and a few dings in the engine cowling; a bruise from the seat belt; nightmares for a few months; and $ and time to fix the plane. Main lesson is the benefit of staying current. ...i misjudged a no power circuit because i hadn't been doing a lot of flying, and i think our tendency to do larger circuits as if or aircraft have a l/d of better than 20/1 instead of tight ones you need with an l/d of 11/1.

Get some quotes. It will depend which State/Territory you are in. A few years back there was a lot of liability law reform intended to reduce insurance premiums. ...They didn't. But what they did do is make it very hard (almost impossible) to sue a medical doctor for negligence or someone engaged in recreational activities that are inherently dangerous such as flying light planes. Have a read of the NSW Civil Liability Act. Some law shops have published layman's summaries. You may find that showing these summaries to the landholder might do away with the need for insurance. Its not quite true that you can't hand over tort liability...you can agree with the landowner to indemnify him or her for any losses (this is what insurance companies agree to do) ..but of course the kicker is if you don't have enough money. As i said previously, unless you are running commercial flights (not just a flying school), the Civil Labor Act should be sufficient protection. It always annoys me with this liability stuff.....with the exception of the tort of nuisance (which is generally about environmental damage to another person's land), you have to do (or not do) something wrong or bad to be liable, that is you have to be negligent (such as breach a standard) for negligence, or do an positive act (such as tamper with an aircraft) for a trespass. Is just an insurance company scam.

We just crossed from Northam WA to Goulburn NSW last week in a Tecnam. I can strongly recommend staying a night at Forrest WA and refueling there. Friendly and keen aviators there. Nullabor Motel is a dump & a dive....we refueled there, but would have been better off to push on to Ceduna. From Northam we flew to Kalgoorlie via Southern Cross, then to Forrest direct, then cut across to the coast to Border Village....Nullabor Motel...Ceduna...Port Augusta. The only fuel planning issue we had was the long leg from Kal to Forrest with a 15kt head wind...but we still landed with 28l remaining (actual) vs 18 planned. There are lots of good strips to land on next to the railway if you carry extra fuel in jerry cans. ..but we didn't. The only problem we faced was at Mildura where the Mobil pump would not take the Mobil card issued to us a couple of weeks before and the agent wanted to charge us a $60 call out fee. ..We caught a taxi, bought a jerry can from Bunnings Aerospace and enough fuel at Caltex to get us to Hay to fill her up. Avgas at Nullabor motel was $3.30 a litre, which was the most expensive of the whole trip. If range is a problem, another option (going west) is to fly the coast to Caiguna and cut across inland to Rawalinna (no fuel there) and then follow the train track/road to Kalgoorlie. Have a great trip. ...ours coming east was fantastic.. 2 days of headwinds to Forrest, then 3 days of tailwinds to Goulburn.

One word of warning on the silicone hose. I once saw a vw engine struggle to reach full power. The inlet manifold had the carbie under the engine with 1" steel tube going up and over to the inlet ports which are on the top of the heads. Like the Jab, the tube was joined by smooth rubber tube. However the tube was crossing a gap of about 80mm between the steel tube. We observed that at full throttle the tube was collapsing and restricting the inlet. ....i assume because of the high velocity of the air/fuel in the inlet manifold even though manifold pressure was nearly ambient pressure. You can get fuel resistive rubber hose with a strong steel wire embedded in it so it takes suction. .,.but it's a bastard to cut and install as it doesn't stretch much. Btw we fixed the problem with the vw with a steel tube 'stent' liberated from a bicycle frame.

On my set up (Jab 2200 in a Cygnet) I have the outlet from the airbox directly behind the carb....about 150mm gap between. I have a fibreglass tube about 50mm long with 3 flat flow straighteners (2 vertical, 1 horizontal) on the carb and a 'criss-cross' flow staightener in the glass tube that exits the airbox (it actually goes into the airbox by about 15mm). The glass tube from the airbox is attached to the glass tube on the carb are joined by about 100mm of scat hose. ..no bends. All this made almost no difference to egt spread. ...The only thing that did make a difference was the pressure at the inlet on the cowl and the length of scat from the cowl to the airbox.

Thanks Jabba. I'm sure we do. I think mine is sorted...at least good enough...all within specs now. I have two 'criss-crosses' upstream from the carbie....one at the carbie entrance and one at the airbox exit, no bends, just dead straight. No.4 goes hot (lean) on WOT and No.1 on cruise, so tilting the carbie make one or the other worse. Bigger difference is inlet air pressure - less pressure gives more even mixture but less power at WOT, and of-course at cruise (less air being sucked) and faster airspeed means higher pressure (depending on where one's inlet is).

Bruce, and I thought my starboard cylinders were hotter because they were further forward. The first question is whether the difference in CHTs is due to EGT differences or not. The way my CHTs go, I think that mostly the difference is EGT related, but there is still a residual that makes the stbd side hotter if EGTs are the same. I have thought it might be to do with the fuel pump, fuel hoses and gascolator (on firewall) which are on the stbd side that somehow interferes with the flow of air out of the heads in a different way to the scat hoses on the port side. I also have a stbd offset to counteract the engine/prop P factor and a 4.5 degree downthrust, but I wouldn't think that would make that much difference. Others have postulated that its the downsweep or upsweep of the prop, and have put little fences on the cowl inlets. But I reckon the big issue is the exit. The RV guys have found that modifying the bottom of the firewall edge makes a big difference, such as a curved sheet of aluminium attached to the bottom of the firewall coming fwd towards the engine and up and around back to the firewall to give a 200mm diameter curve to the fwd facing rear side of the exit. It could also be due to different compression ratios. Perhaps my crankshaft is a bit more to the starboard side, and yours is a bit to the port side? I don't know what the Jab tolerances are on that sort of thing. On the EGT side of things, I think it could be differences in the flow diverter (again we dont know what the tolerances are), or simply how the needle rests in the needle jet in the carbie. We all seem to think it sits centrally in the needle jet, but I think it tends to rest on the side of the needle jet and this effects how the fuel plume comes out of the jet, ie. if the needle tends to rest on the port side, more fuel will come out the stbd side. Of-course with the breeze in the carbie throat you would think the needle would be hard pressed to the front of the needle jet. And then there is the atomizer that the needle jet sits in. I have seen that the South Africans at one time were suggesting making the four holes in the side of the atomizer larger (more air?) and that this reduces EGT spread. But equally it could be more to do with the orientation of the holes. Anyway, lots of guesses. Maybe its just animal spirits....I know my wife seems to think its easier to start one of her Ducati motorcycle singles if another one is already running to avoid the shame of not running!

An exhaust augmentor was going to be my next project but as my temps are now OK, I'd rather save the weight. I am going to try wheel pants (and a general drag tidy up) to see if I can get my cruise speed from 90 to 95 kts. And here are my EGT & CHT for my last flight....35C OAT at 2400, most of flight at 4500 at OAT 30C. Note EGTs spread wide and increase on decent and throttle closed to 13lph.

I forgot to mention that while the cowl is a modified Jab cowl the distance from the top of my firewall to the bottom is probably around 150-200mm shorter than a Jab, and I have added to that around a 50mm 'tunnel', and of course no nose wheel undercarriage. This gave me some challenge in getting the cowl to fit as the vertical height at the firewall had to be shortened, but it also means I had lots of room for a large exit area with only the exhaust pipe obstructing the airflow out.

Yes it is a modified Jab cowl. I've also tweaked the oil cooler a bit by moving the bottom of the cooler forward so it sits more directly across the inlet, and I have flexible baffling between the inlet and the oil cooler to ensure no air leaks under the cooler.

Yep....fantastic visibility. It's the third plane I've built and when I was deciding it was going to be the Jodel sovereign or the Cygnet. The low wing on the Jodel and my experience with a low wing Minimax swung me to the Cygnet. A few people are put off by the Cygent's geodesic wooden wing structure but it was really easy to build....definitely easier than the Minimax, Karatoo or the Carbon Dragon wings I've built. The plane still puts a smile on my face after 17 years of operation. The Jab engine had put 15-20kts increased cruise speed and 400fpm extra climb rate compared to the old 1835VW engine.

And here is a pic of the previous cowl with 50mm lip. Exit area is about the same on both versions.

Here are some shots of my latest cowl, sans lip. Had a big headache last week. Bushfire started by a windfarm came to 150m from my hanger......my 750m airstrip was used by the RFS as a major control line and now has a rough bulldozer track up one side. Close call! The guys on the ground said the DC10 waterbomber was what stopped the fire. Anyway after the fire and in over 30C OAT my max CHT was a tad over 150C on climb at 65-70kts, and on cruise 138C; starboard side still hottest. Oil temp now (Shell W100plus) maxed at 82C. EGTs are still a work in progress.....spread is OK 650 - 715 on cruise (No.1 hottest, No.4 coldest) and 620-700 on climb (No.4 hottest, No.2 coldest). Oil drip on front seal has stopped after balancing the spinner, but it really wasn't that much out of balance. Now I have to upgrade my oil vapour recovery system as I'm dripping a bit of oil from some of my leaky aluminium welding. Mark

Guys, I've been following this thread as I've just installed a Jab2200 rollercam in my Cygnet which previously had an 1835VW, and I've had the usual issues sorting out cooling. I've now got about 23 hours with the Jab motor. My CHT temps at cruise with 25C OAT and at 90kts are 140, 122, 135, 120 & EGTs at around 15.5lph are 695, 650, 690, 645 at between 4000asl and 5000asl. Rpm 2900. They max if I throttle back to 14lph and 80kt and 2750rpm at 720, 660, 720, 645. No matter what I do I can't get the stb cylinders cooler. No 1 & 2 were my hottest cht wise, but baffles in the pressure ducts were adjusted to get rear cylinders chts as close as possible to the front. I originally had over 120C egt spread and that was mostly fixed by putting a fence of about 2cm high in front of the air inlet (which is simply a hole in the side of the cowl). This makes sure there is no ram air. Drawing cowl air made no difference. I also have flow straighteners in the airbox outlet and carb inlet. I do not have a simple cross because, if placed in the nsew orientation, the bottom interferes with the emulsion tube air inlet on the Bing and minute changes produce crazy results. When I installed the fence on my air intake my egt spread dropped and the average egts dropped so I've gone one size smaller on main and needle jets (230 & 2.8 if my memory is ok). I was getting over 140C CHT on no.1 in cruise and oil temps over 90C so I ditched the 50mm lip on the cowl outlet and replaced it with a ramp for more suction. Result was a 5-10C drop on all CHTs and oil temps now mid 70s...so my next step is to put in a plate to exhaust the oil cooler air separately from the cylinders and adjust for mid 80C OT.....I'm worried about winter. Downside is higher Chts on 3&4 when taxiing (+135C). My problem is on climb. When I go WOT, no.4 goes lean and the egt will, if allowed, runaway over 720C. So I throttle back to 3050 rpm where my egts are 650, 670, 645, 690 (Fuel flow somewhere around 25lph). CHTs on climb at 70-75kts don't go above 150C so far. If I rotate the carb to even mixture on cruise, it makes it much worse on WOT. And yes, the butterfly throttle is limited to 80 degrees open. By throttling back I lose about 50 to 100 revs on climb. So now I'm reasonably happy and thinking there is just some tweaking on the cowl outlet with perhaps a bit of exhaust augmentation. I'm thinking my right bank is running hotter because that side is leaner and that may be because the inlet plenum diffuser is not exactly centre, or because of the orientation of the 4 horizontal holes in the emulsion tube/ atomizer which the needle jet sits in, or how the needle lays in the needle jet, eg it might lie against the stb side causing the fuel spray/plume to favour the port side? I get a small drop of oil at the front crankshaft oil seal. Is this normal? Motor runs very smooth.