REFLECTOR: Prop Extension

[Al Gietzen]

Subject: REFLECTOR: Prop Extension

 

To those of you that have worked through this detail, what are your thoughts
on the relative merits/challenges of various prop extension lengths?  I have
heard that anything from 4 to 8 inches will work.  With a fixed pitch weight
and balance should not be an issue, but with an MT or Aero Composites does
the length become and W&B issue.  Does anyone have any data on propeller
efficiency improvement of one position or another?  What length seems to
best suited to the XL cowling with an IO540?

 

- jerry

XLRG N202VB barely started

Jerry;

 

You might want to wait on that decision until you have better handle on
weights.  I expect that there is an advantage to moving the prop back a bit
from the wings and cowl, but have no data to back it up.  I thought that
with a 17 lb. fixed pitch prop adding the weight of a 6" extension, and
moving the weight of the prop back was not an issue.  Now I find that light
weight of an all electronic panel (24.5 lbs), lighter weight batteries, and
no oil cooler up front moved the CG back enough that were I doing it over
I'd probably dis the extension; especially since my more powerful engine
installation is also a bit heavier than a stock Lyc 360.  It just makes for
more ballast in the nose.  The standard lofting for W&B is based on old
technology.

 

Al


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