Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[Andy M]

I really have to go with what I have in my stock of bits at the moment. I will have a small brushless in a plane somewhere, but didnt really want to decommission a plane just for the motor, not just now anyway.
The hydro is an attempt to make use of the motor setup from Rorqual.
As my usual boating area is a river which is fairly narrow, your mention of a wide turning circle isnt really good news. I have other stretches of water I can use it on, so not a disaster.
I appreciate the advice I get, brushless boat motors are a new venture for me, building an appropriate sized hull to match the power of my motor is my main aim, the Rorqual showed just how far of the mark my estimate of the power was. I am fairly confident of a decent boating experience with the hydro, I have 2 power options, 7.4v for initial tests and 11.1v if it needs more.

[Subculture]

Mono hull or catamaran are best for agility. Hydro's best for outright speed. The fact that hydroplanes have so little hull in the water is the reason for their poor turning circle- they don't have much to grip the water. Don't forget to add a turn fin on one of the sponsons, else it won't turn at all.

[Andy M]

I will add a fin, my robbe Proppy never had that feature and I remember it turning without any issues, but it was a long time ago, so I might not be remembering it right. Would one on each sponson be ok? To save it pulling to one side?

[Andy M]

Rorqual is 15 inches long, 4 and 3/4 inches wide and weighs 4.5 ounces with rudder, rudder servo and propshaft fitted.
 Proppy copy is 26 inches by 11.75 inches. Bare weight with no rudder or propshaft fitted but liteply reinforcing pieces fitted is 5.5 ounces. The weight will go up as I will be using a full sized servo and a pretty big rudder (borrowed from my 'four ways' cargo ship) but it should still be very light for its size. It is only one screw to return it to the cargo ship.
 I still have a fair bit to do, but it seems to be going well so far.

[Andy M]

This project had been sidelined for some time after the propshaft and coupling proved to be too flimsy for the task.
 I did think about trying to remove the flimsy propshaft and fit a decent one. I was worried it would wreck the boat during removal, so I thought I would try something else first.
 I always wanted a decent outboard, having tried some small cheap ones and even tuning them a bit. Proper model sized outboards are expensive.
 I thought I would try a 3d printed one.
 I have had to modify a few things and add reinforcements where I thought necessary, material is pla, reinforced with superglue, tissue paper, styrene sheet and ice cream tub plastic. I had to make up pipes for the watercooling, the original was fed by a pump, I want mine fed from the propwash.
 I have used a pump for cooling the speed control, the pickup for this is fed down through the empty rudder tube. It exits on left side of transom.
 The boat has had fairly extensive modifications as well, not just adding a transom and motor support, the sponsons, front edge of hull and front underside have had medium hard balsa sheeting added, not exactly tough, but better than bare depron.
 I ended up removing the old propshaft, I took out the plastic bush at the rear and put my soldering iron up the tube, a small amount of constant pressure and after a few minutes it eased away from the ply support quite easily, considering it was well epoxied on.
 I made up a custom battery pack, 7.4v to start with, I am using same motor and prop as the sea rover, which is much heavier, so IF it all holds together, it should be quite quick, with the option still available for 3s pack.
 I am a bit worried, it is printed horizontally so it could crack apart along a layer. I hope my reinforcements keep it together.
 Only one way to find out.........
 I am nearing testing time, but not just yet, few wee jobs to finish off first.