Which prop?

[Gadget]

Hi.
Ok, so I have spoken to three different people who should know and all three came back with different answers. Now I ask my question here in the hope to eventually figure out what would be the correct propeller for my plane. My problem is that I cannot figure out or get a definitive answer on what diameter prop to get. The suggestions have been from 68" to 72" with a 70" in between. I would appreciate some info from those who have faced this dilemma and found a solution.

I have a Bushbaby Explorer with a 912 UL 80 HP engine with a 2.27 gearbox. I cannot find out if my gearbox can be changed to 2.43 ( I was told this would make a major difference) as it is very old, I think 1994. In any case, the cost to change the gearbox is quite high. I currently have an old taper tip warp drive and want to replace the 3 blades with new square tip blades.

[Duck Rogers]

It's a no-brainer Gadget.
Ask Piet de Necker....

[Gadget]

Thanks Duck. I just feel ashamed calling him because his props don't work on my gearbox which means I am not worthy!

[Aerosan]

Thanks Duck. I just feel ashamed calling him because his props don't work on my gearbox which means I am not worthy!

Hoe nou why would his props not work on your box am I missing something. Oom Gadget, I am very sure that you will get a happy ending with oom Piet and Tannie Bets.

Cheers Sanna

P.s. please I really dont know what Im missing, you know Im not too bright, soos die hoof gese het, "mevrou jou seun is nou nie akademies aangele nie"

[Jean Crous]

2.27 gearbox = 1x P-prop of 72 inch diameter x 47 inch pitch. Static RPM should be 5100-5300. This should give a nice climb-cruise combination.

[Gadget]

Hi.

Aerosan. I haven't spoken to prop piet yet but everyone is telling me he is not fond of the 2.27 due to a harmonics issue. That is now if I understand the singing story correctly. No use pissing of the oracle by not having my facts straight. So I thought to first come here and ask he's trusty followers for advice. I have heard only good things about he's props and would love to have one. However, I already have the warp hub etc., but I am keeping my options open.

Jeantree. Thanks for the info. That static sound a bit low. my engine is rated at 5800 for three minutes and then 5500 all day long. Does that compute? Maybe explain a bit as I am not knowledgeable about that thing which keeps me cool.

[Aerosan]

Hi.

Aerosan. I haven't spoken to prop piet yet but everyone is telling me he is not fond of the 2.27 due to a harmonics issue. That is now if I understand the singing story correctly. No use pissing of the oracle by not having my facts straight. So I thought to first come here and ask he's trusty followers for advice. I have heard only good things about he's props and would love to have one. However, I already have the warp hub etc., but I am keeping my options open.

Jeantree. Thanks for the info. That static sound a bit low. my engine is rated at 5800 for three minutes and then 5500 all day long. Does that compute? Maybe explain a bit as I am not knowledgeable about that thing which keeps me cool.

Mmmmm I see I understand but I have to say Piet is a great guy and I doubt very much that hell be pissed off just call him round 8 in the morning he is then normally available

I have a very similar ratio, 2.2:1 and have no harmonics issues. If I were you Ill just get a loan prop and try it out.

Cheers
Sanna

[Gadget]

Ok. I mailed Peter and asked him to comment as well. Weird that this discussion hasn't come up on microlighters before. I did some searches but couldn't find one. I would have thought there must have been a couple of guys before me having the same issue.

[Jean Crous]

Static RPM is always lower than when you start moving foreward and the prop "Unloads". In flight you will find the RPM to be near exactly what top of yellow range will be , 5400 rpm. Most engines will only operate at peak permissible RPM at take off , with a VP prop, and then as the pitch is set to cruise pitch, the rpm will come down and one will adjust throttle accordingly
Jean.

[Gadget]

yes. with this engine i set the static to 5600 which gives me 5800 on the climb.

[KFA]

I would go for 5200-5300 on static like Jean said. That will give you a cruise of around 95-100 in your plane and a top speed of about 115mph. The take off and climb will still be respectable at 600-800 ft/min.

I would still spend the bucks and change the gears as well as get a p prop.

I have a Explorer here in the hanger that had that exct same problem and the performance was crap compared to the new setup.

[German]

I would still spend the bucks and change the gears as well as get a p prop.

What price are you talking about?

[KFA]

Not sure abou the gears but a prop should be about 8500. I think the gears are About 5500

[KFA]

Remember there are 2 types of gear sets. Open the gearbox first and measure the width of the gears.

[Gadget]

I am waiting for Pieter to get back on to me on my last email. But thus far it seems the best would be to save little longer and go for the p-prop and the gears. I will take your advise and start with a static at
5200 and see what it does. The one problem I still have is that my engine is very old, apparently some of the older models cannot be upgraded and I need to check with Rotax first. I will email them today and find out. KFA, does that bushbaby also have a 912 UL 80hp?