Ducted Fans on Rescue Boat

[wirenut67]

I was thinking of using dual ducted fans on a rescue boat. Is it possible to use these and have them actually reverse, so I could back up if need be?

I have limited experience with these so any help is appreciated.

I am planning on having no rudder, and controlling the boat much like a tank would, by energizing/de-energizing one side or the other. Is this possible?

I realize this requires 2 fans, and 2 esc's. I am planning on using an aircraft type transmitter and receiver for this project. Possibly a Spektrum dx6i, as I have one laying around here. Any issues with this?

I apologize for all the questions, but I am truly clueless when it comes to boats.


Thanks for any help,

Mike

[Diegoboy]

a rescue boat needs a lot of power to pull/push a downed boat. a prop that's not in the water (ducted fan) won't be able to do the job well at all.

[wirenut67]

http://www.youtube.com/watch?v=0o0JRuxilY0

This is the one that gave me the idea. It reverses, has no worry with weed, and is just generally pretty cool!

Here's one retrieving a boat:

http://www.youtube.com/watch?v=iLpHQi-456c

[Diegoboy]

That is pretty cool. He was rescuing a scale boat (runabout) which runs a much lower risk of flipping over, unlike FE boats. If that boat started to take on water through the drive line, then flipped and started to take on more water (without sinking due to all the flotation) then the boat will be much heavier to move. To count on a rescue boat, you need to be able to count on it's ability under the worst conditions. A ducted fan boat for rescue is only good under ideal conditions as shown in the video.
It's still cool though!

[wirenut67]

hmmmmmmmmm had not thought about that.....thats why I am glad this forum is around....I might have to have a contingency plan!

[ED66677]

sure twins will provide better low speed handling/manoeuvrability if used with combined forward/reverse, but not with ducted fan, the one on the video runs fine and fast though, ducted fans have thrust once at speed, air intake feeding the fan increasing efficiency, but imagine this boat pushing an upside down mono, speed would drop a lot and ducted fan efficiency too.. IMO too much!

[wirenut67]

So I found 2 DF's that are putting out about 4lbs of thrust each. They are Hoffmans, and rather expensive, but it would be an awesome build Idea. Cost of motors, about $200 each.


Woooooo Weeeeee

[Scott T]

http://www.youtube.com/watch?v=0o0JRuxilY0

This is the one that gave me the idea. It reverses, has no worry with weed, and is just generally pretty cool!

Here's one retrieving a boat:

http://www.youtube.com/watch?v=iLpHQi-456c

That's Paul's boat, he's a member here (785Boats), so he'll be able to give you any info you need.

[785boats]

Hi guys. Just noticed this thread. Thought I'd best do what Scott T suggests & make a few comments/observations.
Firstly It was originally built for salvaging scale boats at our club, as Diegoboy stated. But it has brought in my flipped 25"mono a couple of times, thankfully.
It started out with two 550 motors & underwater props. The EDFs were added as a bit of fun & to rescue boats stuck in the weeds.
As ED66677 pointed out the fans are very inefficient a these low speeds & the 50A ESCs get very hot as they are not air or water cooled. Batteries are drained very quickly too on the speed runs. They are reversing Brushless ESCs & do allow for great maneuverability. I use a 4 channel radio set up like tank steering. Adding the sponsons to the bottom & making the hull more like a cat certainly allowed for more speed.
But as a rescue boat it does OK.
Here's a build link to the evolution from stage one to stage three if you're interested.

http://www.rcgroups.com/forums/showthread.php?t=845000

Cheers.
Paul.

[wirenut67]

Paul,

Thanks again for posting here, and replying to my emails. I am still putting some thought into this project, but certainly value your input.


Mike

[Diegoboy]

So it does have a prop in the water as well. Good call!

[wirenut67]

No it used to have a prop in the water, it was originally built with props, then converted to fans.

[Diegoboy]

Oh.
Has it the capabilities to recover a boat that is "nose up" in the water? Just curious?

[785boats]

No worries mike.
Diegoboy
I've never tried it, but I think it would just run over it even at very low speed.