3 Blade Prop

[Outback]

I am in the process of building a J430 (up to the painting stage) and would be interested to learn if any J430 owner has installed a 3 blade metal prop in place of the 2 blade timber prop supplied with the kit.

 

I'm told that the 3 blader is smoother (less vibration), much more acceleration at take off & climb out and increases cruise speed by about 5%.

 

Any thoughts?

 

Garry

 

 

[jetjr]

A few guys have played with three blades and largely gone back to 2

 

Cant use metal as they are too heavy, there are some 3 blade carbon fibre.

 

New wooden Sensinich?? from Jab seem to be the latest approach @ $1200 they had better be good

 

JR

 

 

[Guest brentc]

We've had a big thread on this before. I operate a J400 with 3 blade carbon and swear by it. I'm not aware of any metal ones that go on a Jab though. I'm not aware of any of my contacts trying 3 blades and going back to 2 as to date there has been only one 3 blade carbon prop on the market for a Jab that is even remotely approved and everyone that has one swears by them. The Sensinich prop is no holy grail, it's still wooden and has a very stone intolerant fibreglass leading edge and you still can't use it in heavy rain. Jabiru's rubber insert was probably a better design, however the US counterpart does appear to be a little more consistent in terms of build quality and pitch.

 

I would not part with my Carbon prop for any reason at this time. It is smooth, doesn't need repainting to re-balance, it climbs far better, accelerates quicker, is adjustable for when you are down on compression after your valves start to burn out and it's SUPER quiet from outside the aircraft. From people's observation it's considered only half as noisy as a timber propped Jabiru equivalent. Some comments suggest that it sounds like a mini-turbine when taxiing past. Inside the aircraft it's possibly ever-so slightly louder than the timber prop, but it sounds 'gruntier' which probably explains that.

 

I would not expect a 5% increase in cruise speed, however I would expect the same cruise speed as the 2 blade timber, but better climb and acceleration.

 

There are 2 other members on here with the 3 blade carbons too that I know of.

 

If you want to know more or where to get one, please let me know!

 

 

[Guest Michael Coates]

Note Michael Coates has been banned from this site

 

 

[Guest brentc]

It's called a Revolution and the agent in Vic is on this forum where I got mine from. It's made near Bundy, but I'm not sure where (there'a another agent in QLD). The manufacturer used to make timber props for Jabiru's.

 

 

[slartibartfast]

With a direct drive like the Jabs, you do have to take into consideration the loads transmitted to the engine. With a wooden prop, harmonic vibration is absorbed better than carbon, but the main concern is prop strike.

 

When my nose gear folded sideways, I had a total prop disintegration. Every potentially damaged component in the engine has been tested and passed. It survived the strike.

 

With a carbon fibre prop, I think a much lesser strike would damage the crankshaft or something else because the loads would be transmitted much more directly.

 

On the other hand, you need to dismantle and check the engine anyway, so why not go for the performance and durability (rain and stones)? I'm considering it.

 

Note: The above is my current understanding of the situation. Feel free to educate me further.

 

 

[Geoff]

How is the rebuild going Ross?

 

 

[Guest brentc]

You could say that on a Jab, the prop IS the flywheel. The flywheel falling-off problems were mostly because of poorly tensioned props, but not necessarily because of a bad mechanic, but rather weather conditions expanding and contracting the prop with moisture etc. Modifying the flywheel attachment with dowels was merely an effort to remove the chance of the bolts breaking by a poorly attached prop - ie, it doesn't remove the root cause.

 

 

[Guest Michael Coates]

Note Michael Coates has been banned from this site

 

 

[hfrensch]

I fly a SP500 6 cyl fitted with the 3 blade carbon fibre prop and am also very pleased with the performance and durability . I have only done 55hours weith this prop but all I have to do is clean it. With the wooden props I had before I would have to fix stone chips every 25 hours and if I flew in rain I would have to repair the leading edge.

 

I am helping my brother build a lightning to which we have also fitted the evolution carbon fibre prop.

 

Cheers Helmut.

 

 

[slartibartfast]

The vast majority of carbon fibre propellers are hollow and when they have a prop strike they disintegrate into 10,000 pieces.

Thanks for that Michael. I didn't know. That being the case, I'll certainly consider one for my next prop.

Geoff - should be finished this week. The weather doesn't look good enough to bring it back from Taree yet though. In the end I trailered it up there to be done right. Just as well too - more damage was found which I might have missed.

 

 

[Guest Michael Coates]

Note Michael Coates has been banned from this site

 

 

[Modest Pilot]

I go along with most of what Brentc says in his early post. However not the comments on the Sensinich Prop. It's better balanced and less flexable than original Jab wooden one. I thought the rubber leading edge on the Jab prop might be better; sadly this is not the case; it's hopeless in even light rain, I speak from bitter experience, also for some reason they get a lot of stone damage on the back of the prop. The Sensinich seems to tolerate moderate rain (2200rpm)

 

 

[Outback]

Firstly, many thanks to everyone for your great response to my original question. This Forum REALLY works.

 

A couple of questions...Brentc, when fitting the carbon prop rather than the Jab timber unit, did you require any special adaptors etc. or could it be just fitted on directly. Also, you mentioned that your carbon prop was "remotely approved"...pehaps you could expand on this.

 

Modest Pilot, I take your point about rain and the timber Jab prop. What sort of problems did you have?

 

Again, thank you everyone for your input.

 

Garry

 

 

[Guest brentc]

The prop bolted straight on and came with all of the required fittings, bolts and spinner etc. The only tricky bit required is pitching it and you'll need a protractor for that. Some clearance was required between the prop and the cowl. Mine was a tight fit between the existing timber prop / spinner but mine is tighter than most I've seen (no comments please).

 

Remotely approved means that they were to become a Jabiru optional accessory however an arrangement wasn't finalised between the two parties. These props were tested by Jabiru. Rod told me he wasn't 'blown away' with the performance, however it went well.

 

 

[Modest Pilot]

First the rubber leading edge showed a very thin flakey layered look then a section about 25mm flew off in light rain. The prop man that repaired it (Licenced Guy) noted that the pitch varied 1-2 deg. on the same radius side to side. It required 35 gram on the spinner to balance (dynamic); may have been the repair. Interestly the prop pitch check varied with use, the guy figured the wood was to soft and the blades to thin at the ends. I might add it is LSA and this was the third prop fitted before Jabiru were satisfied it was acceptable.