115/105, volume puzzle

Hello, I sailed my 115/66cm width Rocket for a while now, but I am considering to trade it in for a 105 Rocket. (63cm width) I want to use this board for mainly 6.5 weather, 15-20 knots, and I have this idea that a 105 board is better suited for a 6.5 sail.

Would the 105 be an improvement or is it not worth the hassle? I weigh 80 kilos and sail mostly inland, most common winds here are 14-18 knots.... My 2nd board down will be an 86 FSW board. Would love to hear other opinions!

It is only one step down in size, so a fin change could probably achieve almost the same effect.

If you get the 105, then you have lost the lighter wind option so maybe just get a smaller fin for the 115?

Just thoughts......

I've got the 115 rocket. It's pretty versatile. Goes really well fully powered up with a 5.7 and the standard 38cm fin. Also about 80 kg. I sometimes think a 105 would be nice but you can have too many boards with too much overlap.

Can't see why you'd go for a smaller fin. A small fin on a wide board doesn't make sense (unless you move the footstraps in as well) . Maybe it's a myth perpetuated by fin manufacturers?

I'm 78kg and have the following:

115 / 68cm wide(7.5m -6.5m)
104 /63 cm wide (6.5m - 5.8m)
86 / 58cm wide (5.2m-4.5m)

I agree that 105 is an excellent board size for use in 6.5 weather - really nice. I have found a noticeable step down in size from 115 to 104 though and it definitely won't get going as well in lighter winds. I'd keep the 115 and add the 105. Everyone needs three boards.

Hey Guys and thanx SO much for all your thoughts, really helps me. Very interesting to read how you think about/handle these things.

In the end I want a 3 board quiver. I weigh 78-80 kilo, so I was thinking a 75-77 liter waveboard (in a couple of years?), a 86 liter FSW (soon) for my 5.6 and 4.7 sails and then above that a 105-115 lighter wind board for blasting with my 6.5 and 5.6. (still have to buy a 7.5)

Yes, a board change would be a fxcking big hassle, and I already bought a MFC Liquid Pro fin 32 fin, which I though I could use mith my 5.6 sail. Though it might be a weird size when I think about it. Too big for a 5.6, and too small for my 6.5 sail.... I didn't use it, yet. (I have a 5.6 and 6.5 sail) The wind here in the Netherlands is mostly between 14-18 knots. I bought and sold a couple of boards already since I am always doubting what is best for me. For example, I bought a 125 Rocket which at the time was too small for me because I sucked at windsurfing then. 20+ Sessions later, I improved so much that I sold the 125 and bought a 115. Exactly for that reason: wind here is mainly lighter wind. For hardcore days I am considering a RRD FSW 86...

Does this info make a difference on what I should do? I am afraid I might regret another change down, just like sideskirt though I weigh 7-8 kilo's less. It's just that the 6,5 sail is the sail I use the most by far, and then a 105 might be a better fit? ****, it probably is just all in my head!!!

Probably some truth in that, you hear it so many times. But I'm thinking a good percentage of it is the placebo effect, people get a bit sketchy overpowered, believe a small fin is going to solve all the problems, change down, go out again with more confidence, and bingo it happens.

I can't see why the standard fin suddenly develops too much lift? More speed? More angle of attack? You're not going that much faster?

Without any good explanation to the contrary I'm of the belief that the standard sized fin keeps the board balanced and better able to soak up the chop. Believe that and you can get by with one fin per board.

If you must use a smaller fin get a smaller board to go with it. A 95 litre ~ 58 cm wide one.

Well the sail can only exert the pressure that you can counter balance. Smaller sails may exert a little more force if they have the centre of effort less distance from the mast foot , that way you have more leverage over the sail and hence can hold a bit more sail force. But I don't think it's that much, the larger sails seem to have proportionally more shape down below and that may cancel the effect out. So I'd say for a given rider, sails pretty well develop the same force fully powered up regardless of size.

Using a board in the middle of it's intended wind range only, then yes you are right. However we don't do that, else we all need 3 boards. I disagree greatly on the placebo effect though, seriously if you use whatever board you have at the top end of it's range with standard fin, then change down a size it will be sooo much easier. Likewise at bottom end in barely planing territory.

Don't we have a variety of sail sizes? Using your logic we should all still have 2 sails and put up with them outside their intended range

All I am saying is that is he is regularly using his largest board in conditions that make him think about dropping 10L (not much of a drop). In that case he can save a lot of coin by using a smaller fin - we are talking a board used 2-3kn above its intended wind range here, 10L is not much difference, one fin size kinda difference. Then he still has the volume for the days that are not so windy.

And yes, too large a fin does cause railing up caused by too much lift - ridiculously so when on the limit

What is "railing up"?

The reason for this change down board/or fin idea was that once I was going really fast with my 115/6.5 and at pretty hard windgusts my board felt like it wanted to fly and I hard a hard time keeping it "on the ground". At other times that session when the wind dropped it sometimes was actually hard to (get into) plane.... Personally, when I read all these tips and so on, I feel like a smaller fin would indeed help... Though perhaps my 32 fin is too small for my 6.5 sail?

Agree with the smaller fin option...i use a 115 Rocket up to 25knts with a 6,4m sail and 38cm fin as soon
as the board starts to rail up or feels like only the tip of the fin is in the water..i change fin to a 34cm
and it makes the board sit back down on the water..but it doesn't make it go any faster!!