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Old Jun 14, 2012, 04:04 PM
Aggressive Lander
Joined Feb 2012
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cheap rc boat to high speed air boat :) (hopefully)

About two years back I got a cheap rc boat for my birthday. The boat was one of those $20 boats that you can buy at Walmart. The boat was severely underpowered and hard to steer but I still had lots of fun with it, like tying a hook and bobber on and going fishing. Last fall the electronics finally died and I decided to upgrade.

First I pulled out all of the electronics and the old propeller shaft. Then I filled the hole left by the shaft with hot glue and liquid electrical tape. Next I hooked a servo to the rudder. After that I mounted a 2200kv parkjet v3 motor on the back with a 5 inch prop. Then I sealed all of the electronics in a tupperware box.

I will be testing it this weekend and hopefully posting video.

Does anyone see any major problems, or know a way to improve it?
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Last edited by rcfoamer; Jun 14, 2012 at 04:16 PM.
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Old Jun 14, 2012, 04:36 PM
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I would do something with the rudder seems to small if you have alot of power and that small of a rudder it might not turn.The motor will over power the rudder...
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Old Jun 14, 2012, 04:42 PM
Aggressive Lander
Joined Feb 2012
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Any idea how to extend the rudder?
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Old Jun 14, 2012, 04:56 PM
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I'm sure the boat will need it's share of adjusting...run the boat first and see what happens rather than worry about the rudder...I doubt the boat will be fast enough to render the rudder useless. It's easy enough to buy a longer rudder if you think you need one later..

Have fun with it...that's what experiments like these are all about..

Good luck with the sea trials!

-Rich.
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Old Jun 14, 2012, 05:09 PM
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Stuttgart, Germany
Joined Oct 2004
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hot glue + piece of thin alu or stiff plastic sheet attached to existing rudder. I really think you might need an air rudder too behind the prop, but that shouldn't be too hard to rig up.

The prop has very high thrust compared to a water prop and its center of force is quite high above the center of pressure generated by the rudder in a turn, this will cause the boat to roll over when you try a sharp turn. I'm just guessing here but that might be why airboats always have very shallow or flat bottom hulls. with a v-hull the combination of water + air rudder might be just the ticket. again i have little experience with boats and zero with airboats, but it seems like a simple matter of vector addition. in a typical v-hull your rudder, thrust, and CG are fairly inline from rear to front, this means the prop and rudder act on the hull through relatively equal moment arms, whereas in your setup the rudder is acting on the hull from below and the propeller is providing thrust from much higher up. when the rudder tries to yaw the hull the rudder will instead induce roll perpendicularly about an axis between the center of gravity of the hull, and the center of the prop disc. in otherwords you should prepare your rc gear for a dip before trying this out.
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Old Jun 14, 2012, 05:10 PM
Aggressive Lander
Joined Feb 2012
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Is there anything major I should know about boats because I am into planes and have no experience with boats besides for this boat when it was not modified?
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Old Jun 14, 2012, 05:11 PM
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on second thought it might work fine, you have the prop really low on the hull
just give it a shot and post your results
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Old Jun 14, 2012, 05:12 PM
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Quote:
Originally Posted by rcfoamer View Post
Is there anything major I should know about boats because I am into planes and have no experience with boats besides for this boat when it was not modified?
Keep an eye out for gators, they'll gitcha!

Momma says alligators is ornery cos they got all them teeth, and no tooth brush.
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Old Jun 14, 2012, 05:16 PM
Aggressive Lander
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Where I live gators are nothing compared to Giant BULL FROGS and Killer sunfish!!
If I set up both kinds of rudders should I set up a mix between the two
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Old Jun 14, 2012, 05:17 PM
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Stuttgart, Germany
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I would just run both off one servo, or two with a y-harness, if its even necessary, give it a go as is!

btw, that setup you got there looks like lots of fun, please post a video!
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Old Jun 14, 2012, 05:19 PM
Aggressive Lander
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Thanks for all of the quick replies everyone.

I will be sure to post a video if I can figure out how to.
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Old Jun 14, 2012, 05:24 PM
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Have fun good job on the build by the way!!
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Old Jun 14, 2012, 06:30 PM
Aggressive Lander
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Isn't "Water Boy" Hilarious?
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Old Jun 15, 2012, 10:59 AM
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Stuttgart, Germany
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yeah sorry I had just watched water boy the night before I saw your thread, and I couldn't help it. Its one of my all time favorite movies.

I've always had the annoying habit of fitting lines from comedies into casual conversation, it was an entertaining game in the office when I lived in Chicago but over here my German colleagues never catch it. That still doesn't stop me having fun all by myself!
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Old Jun 15, 2012, 11:18 AM
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Joined May 2004
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Is it just me, or is the prop on the wrong way around?

Unless the boat is supposed to run backwards ofcourse...

Did you try the boat in the bath tub?
The CoG looks very high to me, with all the electronics on deck.

Keep us posted!

Regards, Jan.
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