After about 60 hours on my small  DHV 1 Bolero Plus I was ready to move up to a higher performance wing. Since I was fairly happy with the Bolero Plus, the obvious choice was another Gin wing, so I bought a small DHV 1-2 Zulu.. I've since logged 50 hours of airtime on the Zulu. 

Flying the Zulu required a bit of mental adjustment since its flying characteristics are subtly different from the Bolero Plus. Most of the differences seem attributable to the extra-thick center cell which Gin calls the Keel System.

The Keel System 

There seem to be two main benefits to the keel: increased pitch stability and increased collapse resistance. 

The increased pitch stability became very apparent the first time I fell out of a stronger thermal with the Zulu. I had become accustomed to the BP which required fairly quick, aggressive, and prolonged brake input to check the surge, but the Zulu surged much less than I was expecting, and required less brake input for a shorter period of time than the BP, which was a very welcome surprise. 

Gin also claims the increased pitch stability also iimproves the effective glide ratio of the wing when flying into a headwind. A glider which pitches fore/aft tends has an increased descent rate because it "spills air" every time it pitches, whereas a glider which pitches less descends slower and has a better effective glide ratio. I didn't notice a huge different in glide ratio over my BP since I wasn't doing any XC, but I did notice the flights were smoother than the BP with less twitching of the wing in active conditions. 

The keel also decreases the possibility of large collapses due to the increased rigidity in the larger center cell. When pulling an asymmetric collapse using using a single A-riser, it is difficult to pull a collapse larger than 50% because the riser pressure increases when the collapse hits the center keel. 

Another indirect benefit of the keel is an improved glide ratio. Normally, when a wing is made thinner, the brake input tends to deform the wing profile. With the keel, the wing deformation is reduced, which allows the wing to be thinner to reduce drag. 

The only disadvantage to the keel seems to be a decreased sensitivity to weight shift. The Zulu seems to enter spiral dives and other acro maneuvers less quickly than comparable non-keeled wings. 

Apparently Gin liked this feature enough to propagate it to the upcoming Bolero III, because the photos of the prototype show a similar bulge along the centerline. 

Brake design - line-through-ring 

A less visible feature of the wing is the brake arrangement on the wingtip which pulls a line through a metal ring. This feature (which is also on several other recent wings) allows the wing to turn flatter and tighter turns ("turn on a wingtip") by allowing the inside wingtip to fly slower. 

Square wingtips 

The Zulu has the square wingtips inherited from the Boomerang series. Gin claims this increases "aerodynamic efficiency" without being more specific.  

Brake travel 

The brake travel is extermely long on the Zulu and is fairly comparable to the BP. For me, a full flare in zero-wind conditions requires one and a half wraps, and a clean full stall requires two and a half wraps. 

Kiting 

The Zulu kites much easier than the Bolero Plus. The Bolero Plus, being a training wing, has a slow response to brake input and also very high brake pressure.. The Zulu responds much faster, and has lighter brake pressure which requires some acclimating. 

The Zulu has very light brake pressure in low wind conditions. The natural instinct to this is to kite with the hands below waist level to feel brake pressure, but usually this much brake isn't really necessary - it's possible to kite with hands above the waist once you develop more sensitivity to brake pressure. 

Overall 

So far, I like my Zulu. The wing seems to be very well behaved with very neutral characteristics.  The designers of the wing seem to have made good design choices, and have sacrificed a little bit of aerobatic ability in exchange for a very high level of passive safety. 

Thanks to Celia Pender for additional observations on wing characteristics, and Arnel Sanchez, Enleau O'Connor, and Ann O'Connor for various insights into wing construction and design.