(near) Scale Size Propeller?

[hul]

I was considering to upgrade my FW190 to a more scale looking propeller. Scale prop is 16.2 inches diameter, 3 blades. There is enough clearance for that size prop.

It currently runs a 2 blade 13x10 APC-E at about 400W input power. That gives me about 59mph pitch speed at 6200rpm. Performance is good with this combo.

If I change the motor, I think I can run a 3 blade 13.9x14.1 Ramoser Varioprop (adjustable pitch) at the same 400W input power, the same 59mph pitch speed and 4400rpm.
Or a 15.0x16.5 at 3800rpm (available from Ramoser)
Or a 16.2x19.0 at 3250rpm (not available off the shelf)

Where is the limit to this?
Is there anything else I should consider?
Will the lower rpm reduce prop efficiency because of lower Reynolds number? Or will it improve because of reduced blade drag (due to lower blade velocity)?

Thanks, Hans

[vintage1]

Lower rpm unless geared will reduce motor efficiency.

Props? big props turning slow generally result in more thrust low down, unless the prop stalls.

But if you reckon powre demands are the same, and pitch speed is the same, then its likely that thrust is the same too.

I wouldn't go too much 'over square' (more pitch than diameter) as low speed performance may suffer.

[hul]

power demand for the 3 bladers is just calculated, 2 blade 13x10 is measured. The principle will still work even if the calcs are off.

I'm not worried about low speed performance for a fighter plane, it should spend little time at low speed. Take off run is short with the 13x10, a little loss here wouldn't hurt.

So there is nothing that keeps me from using these huge props (given the right choice of motor, prop and gearing)?

Hans

[vintage1]

Just the expense of a varioprop that might not work :D

I am very curious to see what gives.

How deep pitch will the Varios go? No one seems to know except you - its not on the website.

James Frolik has been having what I think are pitch problems with a 5 blader Vario. I am dreaming of a scale twin for 3 bladers, and came to the same point: Very steep pitch needed or a very light plane to keep scale diameters without insane power and concomitant huge thrust at low speeds.

I mean hovering a Blenheim? whatever next!

[hul]

Aircraft-World gives these pitch ranges for the different hubs:
hub 6A: 2.5 ... 6 inches www.aircraft-world.com/shopexd.asp?id=643
hub 8B: 3 ... 10 inches www.aircraft-world.com/shopexd.asp?id=2169
hub 12C: 4 ... 16 inches www.aircraft-world.com/shopexd.asp?id=2176

Hans