Here are some pictures of the prototype of the ground station we built:
Very nice! How do you secure it to the ground?
secure the ground station
We can use anchors to fix it on the floor. If the ground is soft we can make a base on the ground and ballast it with concrete. Then we can anchor the base station on it.
Ground anchors are a well developed technology. They come in many types, and we’d probably want to use reversible/temporary ones during development (eg: http://www.spirafix.com/spirafix_30mm_a_type_&_fittings.htm).
IMHO, if the ground is soft, no problem, just use big anchors. It’s anchoring on hard or stony ground that concerns me. With firm exposed stone we could anchor with climbing equipment (there are various types, I’m not a climber so I don’t know the details). With hard ground with lots of loose stones (as is common around Matera) I think we would have to use ballast (baskets of stones and soil, perhaps) but I think a great deal may be needed.
Do we have an estimate for the maximum peak lift from the glider?
If you’ve ever done any shoreline protection/restoration, you’ll have come across the wire-frame baskets designed to be filled with rubble.
A cheaper option that my dad uses is to get fish-boxes from the local harbour, and fill them with stones, and lash them together with rope.
Yes, those big wire baskets full of stones are called Gabians. Good suggestion. Thanks. Fish (or other produce) boxes would be about right for our 30kgF wind power rig. We can fill baskets or boxes with 100kg of soil and stone easily enough by hand. Ballast will work fine.
I had been imagining a much bigger glider (or kite) and so needing much more ballast. I had not been looking forward to digging something like a ton of soil and stones.
For a test rig this will be fine, and when you start to work on the next version, we can work on designs for both portable-installation, and permanent sites.
A steel re-enforced concrete base would be the simplest, though not necessarily the cheapest, option.
maximum peak lift from the glider
The maximum peak lift from the glider will be 30 kg. This is really the maximum… and only in the very strong wind. I don’t know what waight will bear the kider. It may break before it could pull 30 kg.
What’s the breaking strain of the body of the glider?
I have Spectra
I have 1000m of Spectra braid in each of 0.8mm (68kg break) and 0.4mm (23kg break). I’m happy for us to use it. Shall I bring it with me?
Ok, this is a good idea!
kider breaking strain