Messing About.

I've been messing about with the wind tunnel a bit more... the fundamental problem is that I need a wind tunnel to test the wind tunnel! If I dangle a thread down the tube I can see it is being pulled straight, but as I lower it further in it starts to waggle and then thrash around, further down it settles again, the implication is that there is maybe a standing wave or surface effect giving nodes and antinodes of smooth and turbulent flow. I remembered reading that in supersonic wind tunnels they have holes in the inner wall to stop the shock waves bouncing back off the walls, so I thought maybe a pattern of holes would allow some air to be sucked in at the walls breaking up any slow surface layer of air... you can see why I need a wind tunnel to test the wind tunnel!
Anyhow, another effect is that if I dangle my length of wooden arrow shaft in there it will be stable for a while and then after about 10 seconds oscillations will build and the end of the shaft will swing round just inside the wall. I noticed that the arm from which the shaft is suspended on its thread, is prone to waggle slightly sideways and this is probably helping to initiate the oscillation. I have ideas for a more stable arm, but I feel I'm in danger of getting sucked into a time consuming and fairly pointless exercise in trying to produce something better with very limited resources (and knowledge).
Another project, that's what I need... but then projects need to jump out and grab your attention, so I'll just fiddle about until something appears.


meanwhile the garage needs a really good tidy, however the council tip (or "recycling centre" in modern parlance) isn't open to the public yet due to Covid19 precautions, so I've a lot of scrap timber and garden rubbish lying about.
I'll probably glue up some billets and have a bit of a sort out to keep me busy... there's only so much, online bridge, youtube and harmonica practice a man can take!

Where I'd sliced the top of the flared wooden inlet for the wind tunnel it had left a nice ring of endgrain wood... hmmm, "that would make a nice target" I thought so I pinned it up on the boss and had a go from 10 yards hoping to stick an arrow in the ring. Better than that, it caught the edge and the wood exploded in a most satisfying manner!
Excellent, I had a short off cut of timber lying around so I glued it up and sliced it thinly to make some nice targets, I'll have some fun later today with my son trying to smash them.
I s'pose they could also be used as coasters, and once they get too dirty, they could then be come targets :-)