Saturday, November 7, 2020

VIRGIN MOJITO 650

On a small cruising boat, more than on a bigger one, it makes sense to maximize hull form stability and interior living space and that's what Mojito 650 is about. But its hull is not only designed to maximize space but also to offer maximum performance downwind. It is the one of the Maxi 650, the mini-racer that is a winner in the mini-class races.

There are differences, starting on the displacement, 950kg on the racer, 1200kg on the Mojito and on the sail area that is (upwind) respectively 44sqm and 38sqm. The keels are different too, a torpedo one on the racer and a swing one, with all the ballast on the keel, on the cruising boat even if this one can also have the racing keel.

It has a 1.60m draft on the fixed keel and 0.80/1.85m on the swing one. The superior area upwind on the racing boat, on a lighter boat, indicates a bigger B/D but both boats are certified as class C boats. That is not a good reference in what regards final and safety stability. Unfortunately, neither IDB neither David Raison, the designer, disclose the ballast in any of the boats.

It is very difficult to reunite on such a small boat the qualifications to have it certified as a class A boat, but not impossible as the Mini-racer Pogo3 demonstrates. I find odd the Virgin Mojito 650 not to be certified on at least Class B and certainly if I was interested in buying one I would certainly want to know more about the boat stability, particularly about RM at 90º, final stability, AVS and downflooding angle.

I have no doubt that the overall stability, due to the huge beam (3.0m) and the shape of the hull, with its rounded bow, will be a good one for a hull with 6.50m length, and I have no doubt that it will have an excellent performance downwind, a  very good one while beam reaching and even a satisfactory one upwind with the deep swinging keel (1.85m) help, at least on a flat sea.

The relatively good performance upwind may sound strange but the truth is that the racer, on a flat sea has an upwind performance as good as the one of a racer with a normal bow, or even slightly better due to more stability and the ability to carry more sail.

Of course, due to a lesser B/D the cruiser will not have such a good performance but I believe that even so, it would not be a bad one if we take into account the boat's large beam and understand that performance will degrade rapidly if waves are to be met, especially short-period waves, like the ones that are common on the Med or on the Baltic.

On such a small boat I find these trade-offs perfectly acceptable (with a reserve for the final stability) and the Virgin Mojito 650 has the potential to have a surprisingly good cruising interior, the layout showing an innovative galley solution and lots of storage. 

We will see if they manage to materialize that potential on the prototype that has already the hull and the cabin built, and it looks good!

About the way it is built, that at the IDB shipyard is normally a good one, I cannot say much because they don't use the habitual core material but they say this boat is"eco-innovative" and use a core made with linen, PET and cork. 

I know about cores made of cork but I have no idea about what they are talking about mixing linen, PET (plastic used on water bottles) and cork.

The rest seems pretty much the usual building techniques they use, for instance on the 650 racer, infusion, a polyester resin, with a boat structure made of contremouled frames, bonded, and stratified to the hull.

The IDB boats are not cheap, quality having a price, and this one is not an exception at 64 723 euros for a boat on the shipyard, without taxes, without an engine, without sails, without salon table, mini-galley, chemical toilet or interior lights. 

All those items are options as well as the engine that can be an interior one or an outboard. You can download here the list of options that is substantial:
https://idbmarine.com/fr/mojito/650/virginmojito650.php

Here you can see the racing version at speed. The cruising one will not sail as fast but on the right conditions, I am sure it will sail at double-digit speeds downwind.

4 comments:

  1. The year that the storm in the Bay of Biscay forced the Mini fleet to stop in Northern Spain demonstrated that the scow design is plenty fast upwind in waves. Giancarlo Pedote was leading the fleet in Raison's proto 747 when he was instructed to seek shelter in Gijon, and sea conditions were dreadful.

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    1. I don't have access to the tracker anymore and I cannot verify the wind conditions on the first part of the 2013 Transat, but in 2019 where there was also some upwind sailing we can see that on those conditions the boat that was faster had a normal bow (Lombard) even if the 2nd was a David Raison design, with a rounded bow, not losing much.
      https://minitransat.geovoile.com/2019/tracker/?leg=1

      On the 2nd part of the race, all downwind sailing, the David Raison design went away easily.
      https://minitransat.geovoile.com/2019/tracker/?leg=2

      When David Raison won the first Transat on a boat of that type at certain point he got some upwind sailing with waves and I remember him saying that it was incredibly uncomfortable to the point he was afraid of breakage. That means a lot of pounding and that has to take speed to the boat.

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  2. Interesting to compare the Mojito 650 with the Sarch S7 (https://www.voileetmoteur.com/essai/voiliers/essai-sarch-s7-un-voilier-atypique-et-presque-parfait/97494) one must confess the interior layout for the sarch looks really cozy even if one could doubt about the numbers given (lighter than the mojito?).

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  3. They are very different boats due to a different hull design. For being able to be trailerable the Sarch S7 has a 2.49 beam while the 650 Mojito has a 3.00m beam, a huge difference.

    They don't say the ballast on the 650 Mojito but it is certified in Class C while the Sarch 7 can be certified in class B and that indicates that probably the Sarch has a bigger B/D and a better AVS.

    It is not surprising the Sarch to be lighter, not only because it has less volume (less beam) but because it is built with better materials that allow to the same strength with less weight, namely epoxy resin instead of polyester resin and carbon (even if other fibers are used too).

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