Not sure of this but I'm pretty sure, sailor weight, sail size, and buoyancy are straight percentages, ie 77 kg sailor is 10% heavier than a 70 Kg sailor, so he/she needs a 10% bigger sail and board, to be similarly powered, I think wind power/speed is logrithmic thou.

For your data base I'm 70kgs, use a 90l board from 12 to 15 knts with a 5.3. (I don't like using a big sail in surf, probably my technique, but I'm always getting the clew caught in the lip, plus the extra weight reduces manurverability) so I'm not planning, but can comfortably grovel upwind, and pick up waves early enough. below 12 knts, the sail becomes an airbrake, unless it's very side shore, or side off.
15 - 20 knts an 80l board and still the 5.3
above 20knts a 75l high rocker board, 4.7 to 3.7 sail depending how much over 20knts.

Yeah i think ability and preferences play a huge role in what size gear people use in the waves. Also i think the style of waves (ie dutchies vs margarets) play an equal role in gear selection. Apparently most of the top wavesailors at Hookipa will go out on 70litres in 15 knots even if there 80kg+ just for the extra manouverability on waves.

I would imagine it would be reasonably proportional but one thing you might have to factor in is that some brands vary board rockers/vee/tail width through the same line. Pretty sure the starboard acids are like this. The bigger models might have flatter rocker and wider tails for more lightwind performance.

I weigh 75kg, use an acid 70 with 4.2-5.4 and in fast waves will first go out in about 15knots and crappy waves maybe 18-20 knots. I really dislike using large gear, the biggest waveboard i've used succesfully was 83 litres

i read somewhere b4 this equation is a cubed squared relationship.
i think i recall power generated by the sail is proportional to the square of the winds velocity and the cube of the sail area. and there would be a very similar relationship (if not the same but with a different proportionality constant) for the drag produced by the board and the power required to get planing. (i'm no aeronautical engineer... yet anyway)

i think if u searched on google groups in the rec.windsurfing group you might find it.

But as decrepit said rider ability does play a part along with a comfort factor (i personally dont mind sailing with my board mostly underwater. as long as i can waterstart then its windy enough.
The big problem with ur database idea is that we cannot measure the windspeed or wave height with any real accuracy, and how do u determine successful? Too many variables in my opinion. U really need to work it out by guess and check.

just my 2cents worth.
Bertie

I wish lift went up with the cube of sail area changing from a 5 to 6m^2 would then provide 75% more lift in a given wind speed unfortunately its only linear and changing up gives me only a 20% boost.

Lift=0.5*density*C_L*velocity^2*Area
Drag=0.5*density*C_D*velocity^2*Area

But experience tells us the above is not the full truth, the problem is C_L (coefficient of lift) is not a constant even for a given sail, obviously it changes with out haul/down haul settings but also changes with velocity, eg sail twists off C_L and C_D go down. Also and this is just my guess, I think bigger size sails are designed with higher C_L so when I change up I not only change area but also C_L and hence do better than the 20%. There's no magic formula for C_L, its an experimentally determined number at best it can only be estimated.

im 65kg
75L F2 wave 250length 52wide 7.5kgs
5m ezzy
18-22knots
22+knots same board 4.2m ezzy

soon ill have
85L fish 235length 56wide 7kgs
5.8m ezzy
15-18knots

yeah sucks huh
i learn from the best bluejuice and that includes you too

Had a thought about Volume/planing area, and I think this is where heavier riders are disadvantaged.
Bertie was wrong about the square/cubed law relationship of wind/sailsize, but it does aply to planing area/volume. If length, width and thickness is doubled, planing area is squared but volume is cubed. so if we stick to the kg/l relationship between rider and board, the heavier riders are going to have less relative planing area.
Is this why big formula type boards look so thin?? They've increased the planing area but haven't cubed the volume.

Bluejuice,
Hardie's board is the one we were working on a few months ago. His original idea wasn't for a wave board, but a low wind ocean board, so it's not optimised for wave riding, but get's him out in the waves at very low wind speeds. It's 700mm at the widest point, and 8' 2" long (note the mix of imperial & metric), can't remember offhand what the 30cm tail measurment is, but it's very wide, Hardy converts it to a wave board by taking one of the rear foot straps off.
The tail rocker is slight but continuous, with almost wave rocker at the front. I saw it's wave potential while building it and made sure it had wave type rails, so it's not "snappy". But Hardie is getting the hang of throwing it around abit.

The 30cm width at back is 46cm, which is pretty wide, as it keeps flaring out from there.

The original brief of the board was light wind ocean and it excels in those conditions.

I thought that by building this design I could also dabble in the waves with it and have fun. But I have to admit in waves it's very technical, you have to be right back on the board to get it to turn. It turns from the rear footstrap leeward side, most rear position, very turny and loose but, a bit pivotty. When I put the foot straps in a more forward position it becomes harder to use in waves. I have to take my foot out of strap and onto rail as if in gybing, but is at much wider section of board and tends to bounce out on the bottom turn which is very frustrating.

What it does well, is cruise and speed in the ocean. It also jumps great and tacks easy. The rocker profile is perfect for this. It has a deep Vee and tracks like a train on tracks, doesn't bounce out until you wanna be on a much smaller board anyway., and planes in lightish winds. The width becomes very necessary in light winds with big sails, as you need as much leverage as possible, with the more inboard footstrap positions, you get pulled onto your toes all the time which is not relaxing sailing, but the most outboard strap positions make it sweet with big sails.

Starboard is releasing 2 light wind waves, called the Aero, 71 and 74 cm wide, 117, and 125 Lts. Apparently the hull is dead flat, which makes it loose, compared to my deep vee which makes it suck to the water. Rails on mine are pretty soft wavey rails, and the Aero has the EVO rails. Rocker profile will be interesting to note, and tail width also.

If I was to change the brief of the board and want more wave ridability, I would go flat bottom, thinner tail, and slightly more rocker, I think this would make it more wave friendly, however, it would lose some of it's early planing, straight line stracking at speed, and no longer feel comfortable carrying big sails.

There's no such thing as the perfect board, it's all costs and benefits.

One thing I forgot to mention was the idea of under the hull cut outs in the rear tail section of the board. I wonder how these might affect its turnability, I wonder if starboard will have them? Decrep and I didn't have a clue about these ideas so didn't even think about them, They may be necessary to get a wide tail board to turn??