On 05/31/2011 02:39 PM, MalcolmH wrote:
> Fran, Like David I have the monowheel and although the two blade
> version would be attractive, would the smaller blade performance be
> acceptable in the two blade version.
I'm not sure so I suggest to ask Jiri from Woodcomp about this before
you order.
My feeling is that it should work. I have an intercooled 914 to drive
the prop, you have a smaller engine and want to have a smaller diameter
prop, which sounds reasonable to me.
If possible, I would go for the two blade version. It saves weight, has
less gyroscopic effects, is more economic in fuel and allows a higher
speed. And allows easier removal of the lower cowling as well.
It is just a bit more important to keep the carbs balanced, I feel it is
a good thing that any carb problem reveals itself immediately as
vibration. Others prefer a three blade as it runs smoother in all
situations, even when one carb takes up the slack.
I'm not sure if it has any practical meaning for you, but I went through
the dreaded noise tests and paperwork to get a noise certificate for my
installation. But probably any deviation from my specific setup makes it
non-transferable although logic predicts that a smaller engine and a
smaller diameter prop won't produce more noise. BTW it came out at 63dB.
(Couldn't believe it first because on the ground the prop is quite
noisy, probably because the inner part with the large twist is stalled
out while the forward speed is zero, but once flying it climbs like a
rocket and it brought me very high above the sound measuring spot :-) Oh
and this was with the exhaust augmenter and this might cut down a bit on
exhaust noise as well).
> All that I have read would suggest that the
> Smart Avionics controller is well suited for the job.
Yes it is. I have the prop with the feather option, it comes with a
faster motor, and in fact it reacts so fast that it behaves like a
conventional CS prop. Anything I do with the throttle, it never leaves
the target 5000 RPM.
> Would either of
> you recommend their Manifold Pressure transducer or did you go for
> something else.
If I recall correctly this pressure transducer is optional. It only
serves two purposes: to display the % power and/or MAP, and to use the
"Throttle" function. (This allows the controller to sense when you
suddenly close the throttle in a faster than normal way, like when you
want to descend, and it then keeps the prop in coarse pitch rather than
trying to keep the target RPM. The idea is that you can subsequently
slam the throttle wide open without risk of overspeeding the prop). I
found it hard to utilize this function as I have learned to be slow on
the throttle anyway so the "throttle" function rarely kicks in and in
the case of a go around I would still throttle up slowly, giving the
controller enough time to cycle the prop to coarse.
I have a 914 which has a constant high airbox pressure regardless of
altitude, I recall there was a different recommendation for the specific
MAP transducer for the non-turbo engines.
In hindsight I found the need for this transducer minimal. I have it,
and it now serves mainly as a backup display for the MAP.
Frans
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