Flying-Boat V0.2

A small experiment with foils to evaluate the feasibility of a flying boat with U shaped hydrofoils.

This is a pure Fablab creation we started to have the idea to test this with Ricardo at 20h00 one evening @ the Artilect Fablab in Toulouse and at midnight all the part where designed & cut ready for assembly.

The end idea could be to modify a hobbiecat or similar boat. But for now it is to have fun with the understanding of hydrofoils.

Concept to demonstrate:

U shaped foil which have to following interesting advantages:
- Reduced induced drag due to the presence of sidewalls
- No stress concentration a the root of the wing requiring costly carbon fibers
- Connected to the bot by a pivot axis allowing easy angle of attack control and to put the foil out of water for ditching.

Things not included in this design:

A decent hull
lateral control & stability
Pitch & altitude control & stability
Hydrofoil polar calculation

Hydrofoil design:

Chord widith 74mm
Speed 5kph -> 1.4m/s
Water kinematic viscosity @ 10degC = 1.267E-6m^2/s
Reynolds (in water) Re = 8.0X10^4
Lifting surface 0.03m^2
Initial idea was to use an Eppler 818 profile it is good at those low Reynolds numbers. More details can be found there http://airfoiltools.com/airfoil/details?airfoil=e818-il
However making such a small profile with styrofoam was an issue.
Since at those very low reynolds a flat plate works well. a 1 mm plastic plate was used with some camber.

First test:

Very crude just pulled by a truing at the end of a stick on the local river
She managed to take off at fast walking pace even loaded up to 3.5kg
The hull shape is extremely crude & the bow create an incidence effect to the front foil requiring a bit more incidence to take off.

What is next:

Upgrade the prototype to have a better hull shape
Integrate lateral and vertical control
integrate a propulsion system making similar effort as sails.
generate a polar for the foils.

Pictures Courtesy of Ricardo.

Made in Fablab Artilect: https://artilect.fr/