KE>   I have a question that I have asked so many and everyone at the lo
KE>   flying field here has a different answer.  First, my question, is
KE>   there guide lines that a person could go by when trying to decide 
KE>   propeller to use with a particular size engine???  I have bought
KE>   several used engines and I cannot figure out what is the right pro
KE>   use and which is wrong.  I have the following types:  OS .10, TIGE
KE>   .40, K & B .61, and a .25 .......    If someone could tell me what
KE>   proper props are to use (and what makes one different from another
KE>   would greatly apprecaite it....
 
Ken-This is definitely NOT my field of expertise,
but I just gotta put my two cents worth in here.
 
Your problem is similiar to those of us in the
boating world who have the same problem, and I 
can give you definite answers to prop size in
boats, and most certainly the same rules hold
true in planes:
 
1-You must know the operating range of the
engine in question. ( maximum RPM's)
 
2-You need some way to measure the ACTUAL
rpms of the engine with a particular prop/
plane combination. (Full throttle).
 
If the engine does not achieve the full rated
rpm of the engine/plane/prop combo, then
the prop is too large, and should be replaced
with a smaller prop. (on boats, this is
usually done by using a prop with less pitch,
not a smaller diameter prop)
 
If the engine exceeds the full rated rpm, then
you need a larger prop. (increase the pitch).
 
Perhaps, on planes, changing the diameter of a
prop is the way to go, I really don't know, but
the above rules MUST be the same in both cars
and boats, physics being what they are.
 
 
Hope this helps....
 
Bob Cole-
--- TriToss (tm) Professional 1.0 - #68
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