Kenlsa

Tigershark,

how is your covering going. Have you selected a system yet?

Ken

Further to the above, I did try increasing the length of the plenum at the rear.......VERY bad. It increased the rear head temps by 15deg,

Spoke to Ian Bent about it and as it followed the 90degree bend at the rear it increased the drag slowing the air too much, making a stagnant air pocket.

Ken

Glen,

this is what I did after a heap of testing.

I ensured a gentle slope for the air transition instead of a “step”

Not shown are the gull wings underneath on the cylinders.

Note the rubber grommet— this was required to reduce the standard factory hole size (19mm-3/4in) to slightly increase the amount of air staying in the plenum 

Overall no lowering of the temps on the front heads but from memory a drop of 15 deg on the rear heads. 
better temps on climb as well, 85kts@3000rpm to 1500ft, then cruise climb at 250 to 300 fpm @ 2800

The only time you have too much excess power is...er.....never

2 or 4a

if you hang onto it you have saved plenty of cash.

4b E24 results in an orphan that will be hard to sell.

We are converting or club ROKO to E24 as it is close to 15yrs but only 900 hrs.

As a club we can absorb the potential loss coz being made of tin we will crash it (again, first was a heavy landing, big bucks to repair!) but write it off next time.(?) As E24 we can not train in it, only make it available to club members with their full certificate. This seems to be the best way out for us.

Ken

RF,

 I was wondering about the far cooler temps with the G4 may have caused a problem but have not followed it up.

With mogas, ensure that there aren’t any 90degree bends in any fuel line, or elbow, where you need a change of direction of the line. Under certain conditions (extreme heat) it MAY lead to a low pressure zone on the inside of the elbow causing a potential bubble at that point.

The Jab has gentle bends so is not a problem. This advice is mentioned on STCs for certified planes converting to mogas, for example my Colt. Any 90 deg elbows have to be replace with gentler ones.

Ken

RF,

latest leak down on the 100 hour engine is 78 and 79 /80 and these are cold readings! 
leak downs on the avgas went from 50 to 60 hot. So lap the valves and back to high 70’s. Hence our move to Mogas .

Detonation......starting to be an urban myth. Maybe before modern fuels but never heard of it with 95/98. It’s a different world to 30 years ago. The factory says it’s good.......so it’s good. As with anything, ensure the fire/heat sleeves are good.

I have never talked to anybody who had detonation. Starting to get tired of hearing it quite frankly.

Ken

Bruce,

the Gen 4 that has been on 98 since new has now had its 100 service. Camera inspection shows no/zero/zilch residue on piston or chamber.  L2 took a photo  and the rest of the fleet is now on 98 by now afaik.

Note——-the new fuel filter had plenty of muck inside and some was metal (magnetic test) we are loading from drums at the moment until a bowser goes in.

Ken

RF,
Yellow/whiteis result of avgas residue. All our club Jabs are on 98 now due to avgas residue forcing us to lap valve every 150 to 300 hours 

Wire brush it all off with a brass rotary brush on a drill- piston tops (you may scrape them with a small steel ruler to reach inside if the cylinder is still attached to the case) and combustion chamber- and the lower stems of the valves.( This will be very hard and may need machining -see below)

if you see small grey spots on the valve and/or face -that is lead.

use a factory go/no go gauge on the valve stem guides. It may be too tight. If so BEFORE deciding on new guides, ream out the hardened carbon with the factory reamer (I forget the size), you will be surprised what come out! then recheck the go no go gauge again. You almost never need new guides.

take the valves to get recut at an engineering shop.$10 per valve.

Then lap in the valve to the seat (again, you probably don’t need to cut the seat as well, just a lap will be ok)

Oil and reassemble , with same collets to valves DONOT mix them up. then torque to 24lbs.

fly for 5 hours and then re torque....

ring me if you want

Ken

I’ve done a few......engine crane strap onto the prop flange the jack it up till the nose wheel just touches the ground. This will put a force onto the rubber mounts giving you plenty of room

Ken

Unless your 230 is 19 reg, you will have to get permission from Jabiru to alter anything from the LSA specification build

Ken

My Colt has a 6lt capacity but has a running minimum of 2lts.

at a cruise rpm of 2300, mass of 110kg, sump of 6/2lts, compression in the 6’s,  no cooler (or filter) Lycoming has got the parameters right for this aircraft, speed and longevity.

But it takes many $ and time to get it right. Change just one thing, be that speed/cruise/ climb, weight, prop etc, it all starts again.

 I think Jab has it right for a 2200 @100kts in a slippery airframe and a 3300 @120kts.  All this with only a relatively few engines built compared to others.

Ken

Annum,

having flown most types of jabs I have a bit of a “rule of thumb “

UL. Not flown one

SK -need more rudder and elevator 

SP - fast, sporty, land straight away, not bad in turbulence

160- good speed, land when you want them to even if you are a little fast, roomy, good in turbulence 

170 -roomy, need to watch landing speed or you will float, getting tubbier every year

200 top plane though 85 kts best glide can be an issue if having to land in a small paddock

230 good a/c with good speed, though working on 6 pots can drive you crazy if you need to remove the centre heads and barrels and having to use a crane lift to get enough space to removed the carb fuel bowl

hope this helps, others may have observations of their own

Ken

A mate spoke to Jabiru at length when they didn’t have a cooler as ours was overheating  (he was a person who did this for a living, think rocket propulsion and turbines) and tried to work out the size of internal finning required.

Long story short, fins inside absorb heat from the oil and this heat then travels to the coolest part of the structure (sump) which on the outside has a rough surface so any high temp travels to the tips of the casting and tries to equalise with the cooler atmosphere.

Same deal when making a heat sink from ally sheet; when you cut it with shears, don’t file or polish it as the very small rough edges bleed off the heat much quicker than a polished surface.

the maths didn’t work out and the factory had already worked thru that internal fin question and found a cooler was a better option.

All been done before!

Ken

Reading this topic confirms that I am the long lost fourth brother of the 3 stooges.

Ken

T88,

the fire was quite exciting with 170, FK and Grob 102 along with the hangar damaged or destroyed.

All our fleet are trickle charged when not in use. All the holes lined up that afternoon; the smart charger turned out to be not so smart, the battery cooked leading to a small fire and the fuel tap was left on so the heat destroyed the fuel line and the fire was fed by the gravity fed tanks. All over in a few minutes.

So solenoids fitted and taps off at the end of the flight.

only problem now is I get zapped on my watch band if I’m not careful when checking the air filter!

Ken

Skippy,  any battery that I can put in the Colt (sorry RF not a Jab) must be approved with an STC to make it legal.

I am out of my depth here with all this tech info.

I yearn for the days when we looked out the windows for traffic and we used to fly low and buzz our mates to let’s them know we had arrived.

Ken

Looking at weights for a rebuild, the EarthX (LifePO4) at 1.7kg beats my Colt lead battery at 12kg.

It comes with an STC but is spendy at $600 US. Still, I may have to install it if weight becomes a last minute fight.

The STC for a Hawker (Odyssey) will come in at 7kg.

I am updating the alternator and starter anyway so it has become an option 

Ken

While I don’t have a problem with the AD it is over a year old.

we all are aware of glaciers that move quicker than CASA.

Ken

I note that 760 is up for another consultation in the new year according to CASA.
 

So I spoke to RAAus 2 weeks ago about it and it was also confirmed to me that at 760 kg, a LAME will be the only one that can work on my Colt.

CASA will not budge on that requirement even after Part 149 comes through.

The Tech team suggested that I could go the LSA route with a max empty build of 413kg to fly at 600 kg, and I can conduct the maintenance myself.

I have started the rebuild and will/should be able to comply with the 413 rule. I will still get a LAME to sign off on my rebuild just in case I can’t make the weight and so will have to stay on the VH register.

So far have put have put it back to the basic option by making it day VFR by removing all of the lights. All the extra instruments (vacuum) and right tank will come out this week.

I have researched light weight alternator, starter, batteries (choice of. odyssey or earth x as both have STCs) and will get them in the new year. 

I have contacted Oratex and will apply for the STC for the Colt.

Projected weight is 405kg..........so far.....

Ken

Looks like I'm getting old, the 2000rpm should have read 1500, sorry for the confusion.

Found the original computation and this was further tested (still cant find the file though) in still air at 65kts that gave the best glide. 

You should be able to work it out and test for your own prop/plane combo.

Happy computing

ken

Best Glide RPM - Copy.docx

The nose leg is designed to collapse as it is the built in safety feature to minimise a tip over. All correct!

Ken

Old K.

mine has a 2.2. I will see if I can find the workings he used for my plane and prop numbers.

Ken

The true glide performance at mtow in my SP 500 is 65kts. By true I mean the prop is not providing any thrust or breaking force. At 1200rpm (settles at this rpm at 65-70 kts in the landing circuit) the prop is providing a breaking force and will not give you your actual performance so you can feel the true picture.

My ARDU mate did the calculations for zero thrust on my 60x44 prop at various speeds to ascertain best glide.

I gave the formulas somewhere but suffice to say after all the testing was done in still air, the maths gave us 2000 rpm for zero thrust and 65kts was best glide. Note that rpm varies at chosen speed for zero thrust.

Last couple of times I have done my BFR, I have throttled to 2k for my “engine failure” so as to simulate actual performance.

Ken