New Jabiru Carbon Fibre Prop

[Guest brentc]

For those that have been waiting with baited breath, my new 3 blade Carbon Fibre prop was fitted on Saturday onto my 6 Cylinder J400.

 

I haven't done a lot of cruising as yet but the performance is very good.

 

A few things have changed which I shall try to elaborate on.

 

Cruise speed appears to be pretty much un-affected (as expected). Takeoff rpm is very similar, about 2,600rpm (increasing) and takeoff run is reduced somewhat (hard to put a figure on it). Where things start to happen is after takeoff as I build up to my climbout speed of 100 knots. The engine revs out harder than it used to and the extra power is quite noticeable (because of the higher rpm).

 

Climb on my own after fitting at a weight of around 555kg's at 25 degrees was around a solid 800-900 fpm (full fuel).

 

Today with me & GF @ 620kg's it was pulling a solid climb rate of 700 fpm @ 100 knots.

 

On a cruise from Tooradin to Torquay today I was sitting at 4,500 ft, indicating 115 knots at 2,800 rpm. Not bad. Didn't calculate TAS which was probably near 120.

 

I will do more testing next weekend when I go to Avalon and keep you updated.

 

General comments is that it sounds much more grunty from in the cabin and is sounds like the engine is revving harder, but it's not.

 

Sound from the outside appears to be reduced significantly. Probably half the volume of a J160 with timber prop on takeoff - quite impressed with that.

 

Lee Stanley - what are your comments after you saw me flying on Sat?

 

More to follow.

 

(Pic - second Jab with red in photo is the destributor's aircraft with same prop)

 

 

 

 

 

 

[leestanley]

Lee Stanley - what are your comments after you saw me flying on Sat?

Well, where do I start... I'm sure GF will be pleased that you have indicated her weight to us all :)

 

Apart from that, the most obvious improvement from the ground is the engine note - the Jab sounded fantastic climbing away. As you reported, she is now quite a stealthy beast - very quiet in the takeoff roll and as you passed overhead. Now, even more, a very different machine to the 160.

 

And, frankly, the 3 bladed prop looks good!

 

Lee

 

 

[Captain]

Looks fantastic Brent.

 

Thanks for the report. I assume that all of your temps are unaltered? ... please confirm ... and are how do those rates of climb compare with those that you achieved with your timber prop?

 

Very desirable for the looks alone.

 

Do you know if anyone is using one with a 230 wing?

 

Regards Geoff

 

 

[Guest brentc]

I'd have to check Geoff with Boyd about the prop on a 230 wing - I'm pretty sure it's been done already.

 

My temps don't appear to have been altered at all and I wasn't really expecting any changes.

 

I've probably gained up to 200 fpm in the climb, however I used to have those figures when the plane was brand new. Over time a bit of a loss in compression has resulted in some lost power and lost climb rate.

 

Boyd's is pitched at more degrees than mine as my engine has twice the hours and less power accordingly so it wouldn't drive the higher pitch as well and would probably bog down.

 

One of these days in the near future I'll rip the heads off and reseat my valves to get the compressions back up as a couple are down I suspect. A leakdown test will find that fairly quickly which is scheduled for next week. That should get her running like more of a rocketship although I'm pretty happy with the way it's running now.

 

What I am getting is a higher RPM. Straight and level it appears to be hitting 3,300 rpm (hard to tell - taco is bouncing), however I am running iridiums so perhaps 3,250 with normal plugs. My "missed" approaches are getting me a nice 140 knots at 2,900 rpm so I can't complain I guess.

 

I'd be interested to try a 2 blader and see if the speed increases, but it won't look nearly as good!

 

I made an ERROR in my first post of advantages - I don't get extra ground clearance as it's the same diameter as the original.

 

I guess the bits I like the most are the sound on the inside (louder but gruntier sounding) and quiet from the outside so when I'm zooming over suburbia at low level less complaints should hit the casa desk :-)

 

Boyd will be at Narromine if you want a ride in his. I'll be there on Sat lunch to Sun lunch and can give a ride or 2, however I'm not a representative so best speak to Boyd.

 

 

[rodknee]

Do you have anr headsets in the plane ?

 

 

[Guest brentc]

I use David Clarke ANR in my aircraft. They are ok, but not that brilliant.

 

I'll re-evaluate the prop when I fly to Avalon on the weekend as I only have a small amount of time behind it.

 

Believe me, on a Jab SP6 you'd fly like a rocket with one of these!

 

 

[Yenn]

I was under the impression that the Jab motors will quickly fail if tappet clearances are too tight, and from this I assumed that any valve leakage would need immediate rectification. Are you happy flying with known lower compression?

 

 

[Guest brentc]

All engines will suffer from a lack of compression over time.

 

This comes from rings and valves.

 

My tappets are perfect and adjusted every 25 hours (takes about 30-45 mintues) but it's more of a valve seating issue that will cause a loss in compression.

 

Come rebuild time for the top-end, say 800-1,000 hours compression may be quite low and will require some new rings and valve re-seating.

 

Pretty normal stuff.

 

Totally unrelated though, the number of Rotax 912/s/914 service bulletins at the moment is quite scary. I used to think flying behind a Jab engine was scary but not any more!

 

 

[Guest jabgrl]

Who's the GF?

 

 

[Guest Roger]

Today with me & GF @ 620kg's it was pulling a solid climb rate of 700 fpm @ 100 knots.

LOL you are sooooo dead! Quick hide!

 

 

[pylon500]

So tell us, what type/brand of prop is it?

 

Hey, if I had a 620kg girl friend, I'd hide too!!!

 

 

[Guest brentc]

Very funny, ha ha. The prop is a Revolution Prop, made in Bundaberg and sold in Vic by Boyd May. I spoke to Rod Stiff about it on the weekend and he has personally flown behind the 2 and 3 blade models. He said it didn't do enough to get him excited over it, but admitted that it's nice and smoooth etc. I can give you more details if required.

 

 

[pylon500]

Does this mean he will accept them for a certified jabiru?

 

 

[Guest brentc]

Not yet nope and I don't know when if at all.

 

 

[Guest AusDarren]

only likely to happen if the prop manufacturer is prepared to invest the $$ to do the certification tests I'd reckon. Jabiru has no compelling business case to do the testing.

 

 

[Ultralights]

to be honest, the do look a LOT better than the timber props, almost gives it a Real Serious aircraft look! and would look the part in a hangar full of Bonanzas and Mooney's etc.

 

though i HATE the tail shape of all jabirus! needs a bit of work there i think! :)

 

 

[Guest AusDarren]

Does the Carbon fibre prop need to be kept out of showers/rain in the same way as the timber one?

 

Regards,

 

AusDarren

 

 

[Guest brentc]

Nope, apparently it is impervious to the rain. Time will tell.

 

 

[Alan]

It would be good to know about rain errosion resistance. Then there is the problem of qualification for LSA.

 

Up here - we are having our first dry day for at least four weeks? The mould is now getting mouldy. Ho-hum the joys of the tropics.

 

Alan

 

 

[Captain]

What's your view on the prop now BC?

 

G'day BC

 

What's the latest on the cf prop? Are you still wrapped ... and have any issues arisen?

 

Regards Geoff

 

 

[Guest brentc]

Hi Captain, long time no hear. Prop is still going well. I got some black 3m prop-tape from Spruce for it and that has protected it nicely. Until I got that it did get a couple of little chips in the back, so it's nicely protected now. It still flies well, is perfectly balanced and looks like the day it did when I got it. I think I've clocked only around 30 hours on it thus far (I've been a bit slack on the flying front).

 

This weekend we are doing a leak-down test inspecting a cylinder that could be a little down on compression so when that gets fixed (probably an exhaust valve) I'll re-pitch the prop to accommodate the higher horsepower and she will be back to rocket-status like when it was new. Right now (with the lesser horsepower) I'm getting performance similar or slightly better to when the aircraft was brand new. I'll also re-jet to the new richer (23 lph) needle which will apparently give me a knot or 2 at the top end.

 

 

[vk3auu]

I'll also re-jet to the new richer (23 lph) needle which will apparently give me a knot or 2 at the top end.

 

That's what I like to hear.

 

Do you notice the difference in the frequency of the noise with the three blade against the two. I flew to Narromine with a two blade and after flying with a three blade for several years, it sounded strange.

 

 

[Guest brentc]

Yes, there's definitely a different sound in the cabin, probably a louder one actually. I'd describe it as more of a 'growl' compared to what I am used to. Yet, from the outside, I've been told that it sounds quieter, but when I listen from the outside I hear a distinctive extra blade sound.

 

 

[kfowler]

just a question on the prop tape did you put it on the back of the prop. if so did it stay there and has it protected it thank you

 

 

[Guest brentc]

I was told by the dealer to fit it only around 1/4 inch of tape on the front of the blade and the remainder of the 2 inches on the rear. Originally I had it 50/50 over the leading edge. I didn't notice a difference in performance. I prefer more on the back of the blade to protect it from stones, rather than the front which usually gets away unscathed.

 

With the larger part of the tape on the rear, the stones do have a habbit of 'tearing' a hole in the tape so next time I will fit it 50/50 from front to back.

 

It hasn't come unstuck yet.