ballasting with integral tanks

I remember having once seen on 'Soaring' an article
about a clever (albeit complicate) ballasting system
designed for an LS6, where water came from the mains
supply, but with a vertical spill pipe of a precise
length inserted between the supply and the glider,
to avoid exceedingly high pressure and wing shell bursting.
Anyone using this system for integral tanks with bottom
filling (LS8 style)? What's the advisable spill pipe
height for a quick but safe fill?
Thanks in advance,
cheers
Flavio

Flavio Formosa wrote in message ...
I remember having once seen on 'Soaring' an article
about a clever (albeit complicate) ballasting system
designed for an LS6, where water came from the mains
supply, but with a vertical spill pipe of a precise
length inserted between the supply and the glider,
to avoid exceedingly high pressure and wing shell bursting.
Anyone using this system for integral tanks with bottom
filling (LS8 style)? What's the advisable spill pipe
height for a quick but safe fill?
Thanks in advance,
cheers
Flavio

We have a system of this type built into our hanger. There is a 2m
high breather pipe between the tap and outlet. You plug the garden
hose directly into the glider from the system and open the tap until
you see the water rise up in the breather pipe (which is transparent).
You can't over-stress the wings as the water will overflow from the
breather pipe when the pressure exceeds 0.2 bar (2m head - you can
adjust the height of the top of the breather pipe to lower the maximum
pressure). I measured a flow rate of 6.7 litre/minute when filling my
LAK's tanks - thus it takes 30 minutes to fill the 200 litre tanks.

Clinton
LAK 12

Based on Neil Green, my friend and fellow LS8 owner's work with brass
tubing, I built one from 3/4" PVC tubes. It is portable and comes
apart with a quick disconnect to fit into the back of a well loaded
SUV.
Mounted on a 16" square plywood platform is a vertical, about 1.5
meter tall PVC tube, with a faucet controlled, standard hose (T)
connection near the bottom. Above the hose intake is the another T
connection dimensioned such that the Rolladen supplied clear tubing
can be connected. The hight of this T connection is about the same as
the hight of the wing. The vertical PVC tube extends a little over
one meter above the wing through a quick disconnect for ease of
transport.
It's a two handed operation, one hand holds the Rolladen provided hose
to the wing water opening, the other controls water flow via the
faucet. For proper pressure there should be no water coming out at
the top of the PVC tube a little over one meter above the wing. Of
course I must pull the bird to a location where a water hose is
available.
All parts were purchased at a Home Depot with the help of a friendly
sales person, had the Rolladen tube with me to find the correct size
for the T connection for the outlet.
I could take a photo of it if my description is not enough.
Bela

We have a system of this type built into our hanger. There is a 2m
high breather pipe between the tap and outlet. You plug the garden
hose directly into the glider from the system and open the tap until
you see the water rise up in the breather pipe (which is transparent).
You can't over-stress the wings as the water will overflow from the
breather pipe when the pressure exceeds 0.2 bar (2m head - you can
adjust the height of the top of the breather pipe to lower the maximum
pressure). I measured a flow rate of 6.7 litre/minute when filling my
LAK's tanks - thus it takes 30 minutes to fill the 200 litre tanks.

Clinton
LAK 12

Be very careful with these devices, they work great, if built
correctly, but they can do alot of damage if improperly designed.
Things to think about,

1. The height of the "breather tube" ( called a stand pipe in
engineering parlance) is very important, the 2 meter tube referenced
above will allow the wing to experiance a pressure of ~ 3 PSI if the
base of the tube is at the same level as the wing. 3psi may very well
damage or destroy the wing, it is nearly a quarter of a ton of force
per square foot. I would not allow the tube to be more than about .5
meters above the wing if it were mine.

2. The diameter of the Standpipe must be several times the diameter
of the input hose from the mains, because it has the job of
discharging any flow greater than allowable. Bigger in this case is
safer.


Jim (GB)