Hmm, well you maybe guessed I'm riding a through concave
My main three boards are all designed by Parkes :
I tell him I want a big concave and what I want it for and then he does the r est:
The first is a slightly narrower fish quad with 14 mil concave and 'normal' rocker and 'normal' thickness (normal? ) 5 10 by 23 1/2. It's an all round board. It drives through bumps quite well. I've ridden it as a tri and you can feel yourself running on the panels during some turns - as if you are a skier turning on one ski.
One very flat rockered board slightly thicker under chest 15 mil concave. Rounded pin. 5'8 by 23 3/4 to get lots of planshape curve to ameliorate the lack of rocker. This is a board for three foot and under. It super fast but doesn't like it when it is really bumpy. It's the best board I have ever had. It's the second version of this design the first had double wings - but they limited the wave size I could ride it too - unless I rode it with big Mark Richards FCS fins.
One fat fish 14 mill concave 'bit' more rocker than normal? Good for running out on the shoulder on full days. It's a fun board. It's what I am riding mainly at the moment,
All the b oards have slight soft rails about 12 inch from nose - as the concave will make the boards c atch occasionally when coming off the top or when you do those really late take offs and you are goinging sideways while falling down the face and trying to get control (this is the worse case scenario for the big concave boards as it requires really good control (concentration) to not catch the rail.
The first two boards have what I call quad boost - especially the flat rockered one. (wether it's the fins or something else who knows) but after looking at it (the flat rockered one) closely I can see that if you put a straight edge on the bottom the bottom is perfectly flat between say the left hand front rail about 12 inches from the nose and the right hand fins (and off the rail)
And its precisley when this part of the board is engaged in the turn that the 'boost' occurs. Courtesy of the fact that it is a quad I think - as the quads for me seem to turn slightly flatter (ie not as much rail out of the water)
Anyway, what I'm getting at is that it's important to look at the angled contours of the rocker just as much (or more?) then the contours that are parrallel to the stringer.
EG so when someone says gee my board has 15 mil concave down the stringer, what they are really saying is that their rocker is perfectly flat - it just depends on the reference point,.
It's like Hart's spiral vee's if you look at then r ocker contours from an angle (I haven't) then I reckon there would be some interesting insights.
As far as tail lift.... hmm ? Tail vee etc - I think they make life easier but bleed power.
I rode traditional vee concave double concave tail vee until about year 2000. Last one I had (tri) I gave away because it just didn't come off the bottom like a big concave did . It did however ride foamballs in the tube really well (courtesy of t ail lift and vee). And it was very well behaved.
The thing I am finding with the bigger concave as I get older and if I have not been surfing so much it requires more effort to control. But hey, that's just me not surfing enough.
sorry for such a long post
I was going to tell you about the speed panel that albert made me (designed by parkes) in 87 with a step on the sides (the panel was concave in the front half of the board and a step in the back half) but maybe another time
a really interesting board - but in really hard cutties the step would sometimes 'break' contact with the water and spin out.worth while exploring though.
cheers from Oz
PS friend of mine named Ivan is over in Cornwell for a year to learn to make Clinker Boats - he talks funny, from SA originally. He's a kneelo so drag him along for a surf if you gate a chance!
