CTE

[Gray E Fowler]

Nat

I was gone last week....The CTE for balsa will change with the density of 
the balsa it self, but as you have noted, humidity plays a larger part 
here in expansion and contraction. This is not a factor with the composite 
pushrods. 

I am not as inclined as Jason was to read all those emails while I was 
gone, but in short CTE is not so much a problem as is the mis matched CTE, 
in this case the carbon fiber pushrod vs. the fiberglass fuselage. I have 
not run the calculations but anyone interested assume the CF rod to have a 
CTE of zero, then the fuselage to have a CTE of 6.5 X 10-6 in/in F.  I 
would imagine that if you set your trim at 100F then flew in December at 
50F you may have one or two clicks of trim to compensate.  The original 
post asked about storage down to zero F. In reality the servo arm or 
elevator would just move with the cold contraction.



Gray Fowler
Principal Chemical Engineer
Composites Engineering




"Nat Penton" <natpenton at centurytel.net>
Sent by: discussion-request at nsrca.org
11/24/2003 09:24 PM
Please respond to discussion

 
        To:     <discussion at nsrca.org>
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        Subject:        CTE


Gray what is the CTI for balsa ? I have carbon push rods / balsa fuse and 
my elev trim moves around considerably. I suppose it is because of 
humidity variation between the shop and outdoors ?? The pushrods are 50" 
long.      NatPenton
 
 
 

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