http://www.ebay.com.au/itm/4-pcs-1-75-fins-kiteboard-kitesurfing-kiteboarding-/200671345104?pt=AU_Sport_Surfing&hash=item2eb8f1b9d0
Has anybody got any experience with these fins. Are they cheap and nasty?, or just cheap?. would I be wasting my money buying these?
Haven't tried those fins yet, but you might want to look at Advection stuff. I just purchased a set of fsc type fins for my surfboard, and they are great. Superb service, good looking and great feeling fins, highly recommend the site and dealer.
That is a great price for fins you have shown, and at that price you can't really go wrong giving them a try. If you do go down that route, let us know how they are.
Have used polycarb fins in the past and they are ok for a cheap set of fins but best buy an extra set as they can snap off easily in the shallows.
I've done a bit of research on fins. It turns out that polycarbonate fins will flex and vibrate under stress. You learn something everyday. So g10 fins it is!
No it was about twin tip fins. But the same principle would apply to surfboard fins, only magnified. I guess that is the reason why companies sell boards with g10 fins not polycarbonate. The economics certainly don't add up, $5 for poly $20-30 for g10
I have used polycarbonate fins before without any problems (though they were only about 40mm high). Polycarb is quiet tough, you would have to be trying hard to break them. Although I'm not sure what range of 'grades' of polycarb are available. The fins I used were cut from a sheet of Lexan (brand name).
One thing I noticed; fins seem to be more rigid on the board if the surface that contacts the board is slightly more concave than the board.
That way, as the screws are tightened the 'tips' of the fin contact the board first, followed by the 'body' of the fin.
I have seen fins with a flat base that have a slight gap between the tip of the fin and the board even when the screws are tight. This leaves the tip of the fin free to flex a little. Hope this makes sense... 
A quick update.... I ordered some of these fins, they arrived 'as described' in less than a week. Quality seems ok, just need the wind/work planets to align so I can try to break them....
