Epic Performance v. Ultra Layup

Is there a quantifiable speed difference on flat water between these two layups? I'm moving up to Ultra next year and was wondering what others have experienced.

I talked to a guy a couple of weeks ago that said he gains 1.5 kph when switching between Performance and Ultra, but that seems hard to believe.

My limited experience suggests that while acceleration is faster in a lighter, identical boat, overall top speed is pretty much the same in flat water. However, I also think that the faster acceleration is critical in a lot of my races because many of us are such evenly matched paddlers that a 1-2 boat length jump would be huge.

We had a big thread going on this several months back. Mathematically you can predict that all else being equal, a lighter boat should be faster (less boat volume in the water, etc.). The question is: is it enough to notice? Some of us haven't found any significant difference on longer flat-water races, others seem to feel they gained a bit. I think all of us agree that the lighter boat will probably accelerate slightly faster (may be more important when trying to catch and surf waves) and feel a bit more lively (on the flip side, a slightly heavier boat will dampen some of the motions of the boat and possibly give you a greater sense of stability, which can allow you to put the power down more effectively). Depending on the length of your race and your stability skills (and the boat itself), you might gain a boat length or so by going with a lighter layup. As a side note, we're talking about weight differences of no more than 10 lbs on 21' skis.

I'm just consider what ski should I buy, the selected 18 footer are the s18s or the v8, in the ~18kg or ~13 kg range.
The advantages of a lower mass during acceleration is obvious, but if I assume, lightweight advanced composite ski are also more stiffer and have less flex.
How does the flex characteristics influence speed or/and handling in head wind chops, and how much effecting flex picking up runners when downwinding?
I am not sure, is the stiffness/flex in a short 18 footer noticeable at all, or only in the longer 6m+ classes ??

Chances are good to excellent you won't notice any flex in any layup for the two boats you mentioned. A top level paddler may notice some difference in the responsiveness of similar skis with different layups, but most probably won't, particularly in boats from companies like Epic and Stellar. Some boat stiffness comes from materials used in the layup, some comes from the construction techniques used to build the boat, and some comes from the design itself (which is why you'll sometimes see ridges, bulges, etc. in deck areas - it's a stiffening technique as well as a decorative item). These companies have excellent designs and solid construction techniques, so material choice is typically not easily detectable from a stiffness standpoint. You'll more likely notice the difference in the distributed mass.

Here is a interesting link earlier published on Fenn´s website www.fennkayaks.co.nz/weight.htm
My own reflections after paddling V10 Performance and V10 Ultra a lot is that the Ultra responds/ accelerates faster and when talking about flat water that could be the difference between leaving a paddler behind or still have him on your wash when pushing hard during a race.

In the Fenn article a weight saving of 5kg gains you 13 seconds over 25 minutes. So the question is whether the 5kg difference between a vacuum glass ski and a carbon ski is worth the extra $$$. About R1500 per kg here in SA or R575 per second over 25 min! (Last time I checked pricing)

Will your buddy and arch rival beat you if he gets a lighter ski? The thing is that he and you will know that it may have been because he has a faster ski rather than because he’s a better paddler. And of course if you beat him you’re laughing.