>In a recent posting Marty Sasaky told us he uses Skyshark spars.
>I know these are very lights (11, 13 and 15 g.). I would like to ask what about
>stiffness compared with other spars and how does Marty interconnect them
>because their outer diameter is not constant. Where can we obtain tube, ferule
>adapted for these spars, preferably in Europe (Vlieger-op has the spars but not
>the associated material to the best of my knowledge).
I've promised the data to Simo and I will post it here when I
remember, but I've forgotten the bast few days.
However, here is some rough data to use until I remember...
As a point of comparison, an Advantage 250/2 weighs 14 grams for a
32.5 inch length. The Sky Shark 3p is 11 grams, the 5p is 13 grams,
and the 7p is 15 grams. The "p" stands for ply. Sky Shark claims that
they use thin plies of graphite and another material to give the spar
toughness and stiffness.
The 3p is roughly the same stiffness as the Advantage 250/2. The 5p is
a little more flexible than the Advantage 250/3. The 7p is somewhere
between the 250/3 and 250/4.
Remember these are just from memory.
There are two ways to connect them, one is the recommended way, and
the other is the way that I connect some tubes.
The tubes are reinforced on the outside. The reinforcing is then
ground down. The outside diameter near the ends are the same for all
of the rods. An anodized aluminum tube is used to join the tubes
together. This is the recommended way.
The inside diameter of all of the tubes is the same. I'm not sure what
the exact diameter is, but a Beman 6.3mm rod will slide into the
center of the tube nicely. Since the tubing is reinforced near the
ends, a short length of 6.3mm can be used as an internal ferrule. I
wouldn't use this in high stress situations, but it works quite nicely
in other applications.
One nice thing about these tubes is that the 6.3mm rods slide easily
into them. This past weekend in Wildwood, I slipped 6.3 rods into the
Sky Sharks to increase the weight of the kites. This made stopping
much easier and strengthened the wing tips which gave me much more
confidence for doing tip stands and such.
Remember too, that I'm biased. Health Sciences Technology Group
sponsors Storm Front...
Marty Sasaki Harvard University Sasaki Kite Fabrications
617-496-4320 10 Ware Street Jamaica Plain, MA 02130
Cambridge, MA 02138-4002 phone/fax: 617-522-8546