a question regarding fins.....
I can understand the relationship of CP with standard fins. but I was
thinking about a slightly different scenario which may be of use...
Imagine a "fin" which was actually two very thin fins placed parallel,
and reasonably close together. The roots of the two fins would be joined
via the body tube connection, and the tips, or other points could be
joined by the use of small tubes (viz 1/8" Launch lug materials) or
small flat braces to reduce the fins flexing, and to make up a sort of
The theory being that the airstream would flow around the outside of the
two fins, but also (probably a lesser amount) "through" the fin, adding
extra corrective effect.
In it's most bizzare format, you could picture this being modelled as a
series of tubefins glued between two planar fins.
Benefits of this idea (presuming it has aeodynamic benefit)....
Instead of upscaling fins on scale models, you could replace one
oversized fin with two thin fins, of the correct scale size, and get
increased, or the same, corrective force.
OR... Better yet. How about a scale delta fin, with bevels. Instead of
meticulously sanding the bevels, you could make the "fin" out of three
fins. One large one in the center, with two smaller ones (one each side)
with the edges were the bevels would have been. Optically this would
show a crisp edge where the bevel should be, but maybe simpler to make,
and with better CP.
Obviously the aerodynamic merits of this idea would need to be looked
at, but I figure there's plently of "smart cookies" on this ng who could
theorise, or test the concept and state the benefits.
I know that there will be reduced airflow effects "within" the fin, due
to the nature of the constriction, and double frictional drag.. but
perhaps this is an acceptable tradeoff for true scale size fins, or
reduced nose weight in scale models.
Queensland Rocketry Association
"Inner Child" be darned... I'm having WAY too much fun rediscovering
my "Inner ***ager"!!! dyb 11/2/99
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