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Drawing and cutting arcs (possibly a repost?)




I tried to post this already, but it didn't appear on my news
server. I am sorry if it's unnecessary repost.


"Jaco" dividers (pair of compasses)
-----------------------------------

Curved shapes are very popular in kites today. Not only 
for decorative purposes, but e.g. in trailing edge of 
single or dual line deltas to reduce unwanted flutter. 

One technique to draw wide arcs is to use a bent spar as 
ruler. This works very well unless a certain radius of 
curve is wanted. A calculator and some knowledge of 
geometry is needed to determine the amount of bend 
corresponding to the wanted radius. 

More straightforward way is to use dividers.

Because dividers of useful size ( > 1 meter) are not 
available, or are very expensive and clumsy, we have to 
make one by our selves. 

The key components are the same we use to build sport 
kites: leading edge connectors and a carbon spar. I used 
T-shaped Jaco Pro connectors - because they are good, and 
I had them on the shelf. I inserted a nail in one of the 
connectors. Actually I glued a nail inside of a piece of 
carbon spar, which fits nicely in the connector. To the 
other connector I put a pencil, I had to use sand paper 
to make it fit. 

Now, take a full lenght of spar, put the connectors with 
nail and pencil on it, adjust the distance and start 
drawing your templates. The nail should keep one end in 
place when you draw your arcs. 

Some additional tips.

I use heavy metal pieces to keep templates, fabrics etc. 
in place when I work on them. (Actually they are old, 
damaged loudspeakers, tweeters. The cone is removed). I 
drilled a hole for the nail in one of the weigths, now 
the center of the arc can be outside of the template 
material. 

I also made a knife acessory for the Jaco dividers; I cut 
a slot in a connector through one wall, inserted a piece 
of Stanley cutter blades, tightened with a cable tie in 
place. With the knife I can cut curved panels from fabric 
directly, without a template:-)) 

Hot cutting accessory is still unsolved.

Disclaimer: I am just a customer of Jaco Engineering...

Smooth Winds
Simo.Salanne@csc.fi

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