Mr. Francois Denhaut was a great French designer,he worked for many companies and also he had his own firm, he designed with Bellanger many projects;
1- single-engined four seat tourist biplane project of 1919.
2- twin-engined flying boat biplane project.
3- twin-engined Amphibian biplane project.
4- two seat glider biplane,actually built.
5- four-engined submersible biplane project,(I translate it by my self,but not sure).
Also in 1930,he designed a three engined torpedo bomber flying boat project, intended to compete in 1930 contest.
The aircraft actually built by Bellanger-Denhaut was the BD.22 flying boat.
Source; Francois Denhaut createur d'Hydravions