A Second (and half) look at the i-Mocca

A few weeks back I promised to come back with a more extended test of the TMS i-Mocca.
Well, Dutch has been so quick at providing new corrected versions of the boat than I got lagged in my testing.
Part One: Preliminary checks
So we now stand at v.2.5. I will let you check the release notes to list all the corrections and modifications. What is for sure is that all that evolution has been positive regarding sailing the boat: better overall speed, better reactivity, and smoother sailing overall.
The i-Mocca is still a heavy big boat, far from the swift Star or the highly reactive Flying Shadow, but she is a very fine and complete boat which will keep you busy while you sail her, with or without crew.
After more extensive sailing, doing my long dry laps to map out the polars (see below), I start to get a better understanding of the beast.
Like other recent TMS boats, she is tricky to sail, with a steep learning curve to get the best of her. Yet, she becomes manageable relatively quickly, as the sailing is pretty straightforward and the boat relatively stable, as long as you don’t raise the code 0 or the spinnaker too early.
One thing to do right away as you get going is to extend the foils on both sides. That will not generate any drag apparently so the speed is not affected, and it simplifies greatly the skipper’s job. No need to switch back and forth as you tack or gybe.
There will be plenty to keep you busy anyway!
A major performance trigger is the keel angle, which will let you stabilise the boat on the best angle to get her foiling fast. Contrary to other similar SL boats (like the TMS OD65 or the WildWind Open60) and contrary to my first impressions, you shouldn’t get her to heel too much. I don’t know whether the modifications done since v1 did change the parameters regarding the optimum heel angle, the fact is that now, you need to keep the boat relatively flat on the water to get her to speed up. Her attitude in SL mimics more closely the real world foiling Imoca in that matter. Kudos to the creator again for such a nice job in replicating it. So, depending on the wind strength, the point of sail and the foresail used, you will need to adjust the keel from all out to windward (as when sailing upwind) to all out to leeward (as when running down away from the wind).
For easy sailing or when manoeuvring at slow speed, you may want to keep both rudders down, so that regardless of the boat’s heeling, you remain in control of the steering. However, keep in mind that the rudder to windward adds drag and slow the boat down a bit (maybe 0.5 to 1 knot) so when racing, you will want to add the rudder switch in your routine while tacking and gybing.
Part Two: Sailing Impressions
First of all, we complained and Dutch was listening: Most of the points I was critical of in v1 have disappeared. Early bugs have disappeared, animations are more fluid, and the boat’s speed profile has evolved to make her a more exciting racer. She is now faster close-hauled, which allows to point higher upwind. On the other hand, speed under spinnaker is lower, so she is no longer able to run in the lee of the wind as fast as before, in a (probably) more realistic behaviour. See all of the speed impressions summed up in the polars below:

Now that I have sailed her more, I can say that I really enjoy sailing the i-Mocca. She is an interesting piece, and to get to exploiting her to the maximum of her abilities proves to be quite challenging.
She is capable of exhilarating accelerations when set right (sails trim and keel setting) but also she can be kind of a pain and a source of frustration as top speed is elusive, and tricky to maintain. This stems from the dynamics of the boats: as you accelerate you need to tighten the sails progressively, but at some point, the balance is affected and you then need to adjust the keel setting, but often, the boat has already started to slow down a bit, and you need to let go the sails a bit to adapt to the change in apparent wind. Also, partly due to SL conditions, the boat sometimes reacts brutally, and it is hard to keep control. All of a sudden, sail trim and bearing are off, and you must react quickly to restore the right settings: True racer behaviour! She is a purebred and will take some time to be tamed :stuck_out_tongue:
For sure, precise sail trimming is especially important with the i-Mocca.
Regarding the weather helm, I think it is really moderate, especially as you manage to sail the boat relatively flat at most points of sail. It is interesting to note that playing with the keel and the balance of the boat makes her point slightly higher or lower depending which way you adjust the keel. If you push the keel to windward making the boat flatter, it will make her bear away slightly, while a keel move to leeward making her heel more will push her to luff up. Not a major thing, but enough to be mentioned I think.
I like the i-Mocca. She is a nice evolution after the OD65, like the FS turned out to be an exciting and welcome step beyond the Nacra. Easy to get started, but tricky to fully master, she should be a fun racing machine for all to enjoy.
Cheers & Bon Vent!


really great work Viv

Great Work , Thank You very much

well, v2.75 update changes the whole package with a drastic performance boost…
Gotta go back to the dry runs to map the new polars…

NB: all testing was done solo sailing with sails locked, by the way. I shall run some tests with unlocked sails at a later stage.

a picture being worth a thousand words…

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