Carplane®’s twin hulls aren’t merely a design feature but, rather, a key element enabling real driving as opposed to „taxiing to the next airstrip“. Carplane® rejects poor driving performance as a „compromise“. This distinguishes Carplane® from most other concepts.
Carplane®’s specifications call for a two-person bimodal vehicle:
with 2 whole (i.e. not folded) wings (min. 5m² ea., to be easy to fly);
4 large roadwheels (min. 15”) with block (not balloon) tires (for road performance);
fits in a standard-size home garage (i.e. max. 6mL/3mW/2.4mH);
flies well (at least as good as a training aircraft) &
drives well (at least as good as a compact car).
Analysis of many possible layouts revealed that these specifications are best met when employing a twin-hull configuration. Here are two examples:
a). Fast, stable road travel depends on how the wings are stored:
if they’re stored underneath, they’re too small (=hard to fly) & the number of wheels is limited to only three;
if they’re stored above, they create lift in road mode and make the vehicle too high for most underground parking (max. allowed height 2.1m) or if stored behind a cabin they're too short (affecting safety and performance);
if they’re stored on the side, they limit the field of vision or create crosswind instability and, if they’re stored further aft, they make the vehicle too long and may lead to weathercocking.
Storing them between two hulls at a wedge-like angle to the ground creates aerodynamic downdraft, protects the wings from damage and enables high road speeds.
b). Two hulls provide the most drag-efficient housing for a wheelbase consisting of four large roadwheels.
Carplane® is fully aware that some recreational customers may initially question separate cabins (business customers already have cabins separate from their drivers/pilots). However, this layout provides the performance which Carplane® deems necessary for success. For Carplane®, the choice isn’t: „one or two hulls?“; but: „unsatisfatory performance or two hulls?“.
Separate cabins have advantages for recreational users, too. For example, they allow individual climate and music choices. And, unlike tandem seating, the occupants still sit next to each other. (Communication in light aircraft is usually via intercom anyway, even when sitting in the same cabin.)
Jokingly, Carplane® claims to have „solved the problem of couples fighting on long trips“! However, this joviality should not be interpreted as belittling the only real compromise Carplane® made to achieve all the performance benefits which discerning customers demand.