Date:	Thu, 10 Jun 1993 00:20:00 -1000
From:	pat@cs.strath.ac.uk (Patrick Prosser)
Message-Id: <1v71sh$4lp@kelvin-02.cs.strath.ac.uk>
Organization: Comp. Sci. Dept., Strathclyde Univ., Glasgow, Scotland.
Subject: big flow form

I have just completed a large Sutton flow form (FF). The kite is 4m by 3m.
That is, approx 130 sq feet. It is all red. The plans come from Jim Rowlands 
book on kites and windsocks. I took his plans and scaled them up (no bother).
Some details follow.

1. Ripstop. 
I bought 100 quids worth of ripstop. The material is 1.6m wide, and
it cost me 1 quid a linear yard. It is the best quality ripstop I've
bought to date, and the cheapest. I think I used about 40m length of
it for the FF

2. Bridle
I anticipated approx 10lb per sq foot loading (way on the safe side)
during the launch (worst case scenario). This equates to 1,300 lbs
(half a ton load). The FF has 5 keels, each with 2 bridle lines.
Therefore, 10 shroud lines in total. I used 200lb line, again erring
on side of caution. The shroud lines are all about 9.5m long each,
therefore approx 100m of shroud line. I anticipated that this amount
of line, close to the canopy, would generate a large amount of drag,
and tend to encourage the canopy to "over fly" the tow point. So ...
being an extravagant bugger, I used spectra, each end sleeved (20
ends in total). The shroud lines are gathered onto 2 steel rings,
then onto 2,000 lb sleeved spectra (bought at the yacht chandlers at
a quid a meter), then onto a 650kg carb. The whole thing looks neat
and tidy, nothing looks too big, and I know that it is definitely
strong enough.


3, Anchoring
I am now using a new technique to anchor the large soft kites that I
have. I use 2 ground anchors, at least 60 feet apart. I then connect
about 200 or 300 feet of line to them, one end to each. The kite is
then cliped onto the line, so that it can "float" left to right.
There are a number of benefits to this method.
(a) There is always an even load distribution between the 2 anchors.
(b) I can use a line that is not so highly rated
(c) I can use twist (cheap) rather than braid (expensive) as the line
    can't untwist and screw up the shroud lines
(d) When the kite wants to swing across the sky it "floats" along the
    line (decelerating), rather than "swinging" across the sky (accelerating).
(e) There is a gearing effect. When I walk the kite down on 1 leg of
    the line I am subjected to only half of the loading, but it takes twice as
    long.

4. Launch
I use a ladder launch. Stand behind the FF, filling it up with air,
then raise 1 corner. Quickly walk along the back, raising the other
cells.

5. Flight
The FF will actually fly quite well off its bridle! The canopy will
be 30' in the air, and that's quite enough if you want people to be
able to walk around and underneath the kite, and appreciate the scale
of things (and when its on the ground you can actually get inside the
cells). I have only flown it in light to medium winds. It will get
off the ground in a breeze, so the low wind performance is fabulous
(as good as a good delta). In the moderate wind the FF did not pull
as strongly as I expected. I was delighted about that, as I now have
too many kites that I can't fly because they are too demanding/vicious.
I flew it off approx 300' of 1,000lb twist, so I never had it over
about 100' up. Adjustment of the bridle is dead easy as it is
essentially a 2 leg affair (mmm :-). 

6. Drouge
I have attached a drouge to the centre of the central riser, so that 
the drouge comes right out of the centre (x and y axis) of the back of the 
canopy. The drouge is 1.6m long (same width as rip stop), and 2m in 
circumference (at opening). The distance from drouge to FF is approx 30 feet.


7. Enhancements
I think that the 2 largest openings on the back of the kite are too
large. I would like to put a screen across each one. I will make this
screen out of mesh material that is used for making petty-coats. It
comes in fluorescent colours!!

8. Effort
Elapsed time, from when I started was about 1 month. I worked off and
on ... one evening make templates for risers and keels. Next evening
cut cloth, next evening hem keels, next evening hem risers, then hem
top/bottom panels, hot cut holes, ..... on and on. When it gets down
to it, I think I hate building kites, its so damn boring. It's also
frustrating because I always make a mistake, and it takes me ages
until I can look at the kite and not see the mistakes! Anyway, when I
build the perfect kite it will be my last.

Patrick Big-Red-FF Prosser