seabreezer said..
Btw - figured out PD's lack of drive comment - and it is true - IF - you chop the tail (literally saw 8-10cm off) but keep everything the same .... I did it on one of my boards - and the board lost alot of drive .... If you chop the tail - you have to get some drive back somehow - either widening tail , or concaves - or fin setups ....
Yes, I agree. And basically you cant get the drive back in another way but moving the straps forward. Time and again I notice people dont realise how important strap position is and/or they have the wrong idea of what result moving straps has.
Ola H said..
Widening the tail is typically not a good idea, at least not the first one to go for. The absolute major thing with a shorter tail is that produces much less drag in a tight turning radius and hence can be more easily turned tighter. The natural "compensator", if you want it, is less tail rocker. In some senses, a short tail is like have a huge amount of tail rocker, but without the drag.
That is only the case if you are driving off the sail so the sail delivers mast foot pressure and thus keeps the board flat. The thing is that if you go DTL, you lose a lot of wind in the sail. If you have 20 knots of wind and you go with 20 knots of speed (when perfect side shore), you have no wind in the sail at all, so no MFP. In order to keep drive, the straps need to be more forward and with the straps forward, in order to turn, you need rocker. And when turning on the rail, rocker actually has less drag. With my flex tail, you actually feel the acceleration in a tight turn because the pressure of the water on the tail is pointing more forward. A bit like swim fins that provide forward propulsion because they bend.
There are 3 factors at play to make a board turn:
1. Outline curvature or tail taper. (a bigger difference between max width and tail width). This is especially helpful in initiating a turn but can also make a board twitchy, which is not what you want in bigger waves. A board with more tail taper has a bigger wind range as you have a wider part that helps getting planing when winds are lighter but a narrower tail offers more control when powered up at speed.
2. Rocker. Once on the rail, the more rocker gives less drag and turns better whilst keeping control. The downside is a narrower wind range, you need more wind to get going and once at speed there is less longitudinal stability. Rocker creates that there is more water pressure under the board in the front shoulder than in the tail, causing the board to turn, the nose gets pushed into the turn (front wheel turning like a car) and lets the tail slip out (back wheel turning like a fork lift).
3. Force/weight. The more you place your weight to the back, the more you will push the tail out hence the tighter you will turn but you are forcing the board and when having a lot of rail in the water, this will cause drag and in DTL conditions with less MFP, it gets more tecnical to keep drive. On a surf board, to keep speed you move forward but on a wave board you are stuck to the straps.
A shaper can use a mix of these 3 factors in order to create a board for different conditions.
Ola H said..
What I think is the most serious downside of a short tail design is pumping onto a plane in ultralight offshore conditions with bigger waves. It seems here, an extended tail kind of helps lift the board up behind you slightly, which give a subtle advantage.
I think that the main benefit of a longer tail is the drive on the wave. It helps to get on a wave earlier and to keep speed as well when there is less or no MFP.
Ola H said..
For superlight wind short period stuff I think a short tail is so much better though, exactly because you get ultra quick acceleration due to being able to use low drag designs, but still very tight turning.By the way, regarding an earlier comment in the thread. It is completely meaningless to measure tail width by one foot off or by "looks". You should just look at the width at the back strap. On stubbies, the tail tends to look wide and have a huge ofo measurement, but often the tail is in fact narrower than on typical pintail boards. It also makes no sense to think in terms of "how close is the back strap to the tail", like if the strap has been moved back. What instead makes huge sense it to think about the tail length behind the strap. When you already have a rather fast tailed board, tail length in this sense is a super effective tuning variable when shaping, that you can use with no other compensation to just tighten the turn up a bit.
Yes, agree with all that.
