TESTS - New tests: it works ... well if you like, because the slightest stress on the control surfaces causes the prototype to reverse. Mandatory stop. How to extend the control surfaces while keeping the possibility of closing the turbines? By sticking a piece of plastic bag on the lid. New tests: too short, it doesn't work, too long, doesn't work... And finally it works! Third tears of joy.
A fully charged battery, the terrace, and presto! ... more than a quarter of an hour of operation without big problem, just a small adjustment of positioning of the battery. It seems the number of holes under the skirt is good, the air circulates well. A small defect anyway: without propulsion, the machine backs up slowly.
I lend the handle to my son. As he does not know the small faults of the controls, he plays like crazy and causes a shift of the control surfaces. We stop everything, we re-adjust and we resume. Same default !! In fact, the lever arms on the servos are too generous. I solve the problem by limiting the stroke of the handle on the radio control. With experience, I realize that the flap should only rotate 160 ° / 170 ° and does not need a 180 °. Keep an eye on the following models, but the prototype works well.
DRESSING - With another white polypropylene plate, we dress Qoum 8. The sides are in raw "plastic cardboard", as well as the inlets of the propulsion turbines. The edges are not horizontal but slightly inclined to improve the aesthetics. The reverses are dressed first then the top, making the junction at the level of the lift turbine. We hide the connection lines with the decoration strips. The decorations are simple self-adhesive blue nets.
WATER TESTS - Then comes the big day. The weather is nice, a friend is there with his digital camera to capture the scene, the pond is without waves.
Radio contact, lift contact, launch.
First meters, first problem: poor front-rear balance. Back on bank, moving the battery and starting again, twice, but it works. We push the joysticks to the bottom: good directionality, a bit of speed, but disappointment: it does not take the water out. Back to the bank, the skirt is full of water. I forgot anti-scooping flaps (a small piece of skirt that closes the drain holes made on the rear segment of the skirt). I tinker a bit and put it back in the water. Same defect but we continue anyway as long as there is battery. Suddenly, Qoum8 takes a leaning look. Back to the bank, look under the skirt... the glue did not hold. I should have put the screws before testing!
Back at the workbench, I finish the skirt: peeling off and re-gluing the skirt with neoprene glue, and blocking with screws through small sticks of plastic cardboard.
Retry a few days later with a stronger battery: 8.2 v 3300 mA. Launched on the water, Qoum8 picks up speed, begins to climb on its bow wave, but refuses to overtake it. On land 5-7 km / h, on water half : disappointment ! Back to the test bench: we take a small scale, we pinch it in front of the machine and put it all the way down. Front thrust: 125 g for 1,450 kg, rear thrust: 100 g. It's not enough thrust for too much weight. If I compare with other machines, we must either double the thrust, or divide the weight by two !
Well ! I declare it suitable for indoors, when crossing puddles once launched, but no possible to take the water out of the skirt.
CONCLUSION - I have to rethink the prototype, make it simpler, without the reverses; lighter too, so change the lift. But this is for the next time.