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Old Dec 12, 2011, 04:18 PM
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United States, MA, Tyngsborough
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boat porpoising

YouTube shows examples of the Swamp Dog boat porpoising (Front bouncing up and down) both on flat water and ripple induced.

The short answer is ...

The 2 ways usually used to get rid of porpoising is to add bow weight or change the angle of the motor's thrust to pitch to or drive the boat's bow down. The later is better since the force increases with speed.

You can also use trim-tabs. They have the advantage of producing drag only when and as the bow rises up.

We also have the ability to pitch the engine so as to drive the bow down. Obiously you create more drag which slows the boat down.

Speed boats have water-spoilers like race cars to scoop a little water and keep the bow down.

For us I think a trim-tab ... rear deck piece of 1/16-1/8" aluminium bent down to just touch the water would be a good solution. It will however reduce the ability to "spin out" in a 180/360 turn.

PS: The related problem I am considering is how to keep a camera lens dry!
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Old Dec 12, 2011, 05:54 PM
More Motors, More Fun... :-)
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Keep something dry in a fast moving boat!
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Old Dec 18, 2011, 10:53 AM
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Power = Amps and Volts

Measured the HK's stock motor and prop:
Using a 3S lipo, it was 18 amps max at full charge (>12 volts).
About 200watts.

With a 2200mah, 3 cell lipo it ran about 8 minutes @ top-rpms until the lipo voltage started falling fast (~10.5 volts, 12amps).
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Old Dec 28, 2011, 07:50 AM
Row 0, Seat A
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Savannah, GA
Joined Jan 2008
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New Blood Here

Hi everyone. My SD came in the mail yesterday and I started the build last night. Found and reviewed this thread and appreciate all who have posted tips, etc. Here are a couple of things I have noticed so far.

Contrary to a previous post, I measured the motor shaft diameter as 2.3mm not 2.0mm.

Funky prop/collet/spinner on mine was also way out of balance. Can't balance it properly as I didn't want to possibly destroy it by attempting disassembly in order to put the prop on a balancer. I have a 2.3mm collet and a 6x5.5 APC that I may cut down to 5.5dia if I didn't get the balance of the stock prop to my liking. Anyone have good experience with a different prop on the stock motor?

Removed the deck plate/servo mount for more room, and made a mount for the servo on the starboard bulkhead.

Still considering different mounting options for the ESC.

I'll get some pictures up when I get everything sorted out.

Ted
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Old Dec 28, 2011, 12:10 PM
More Motors, More Fun... :-)
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Phoenix, AZ
Joined Jan 2008
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Hi Ted,

The stock prop is pretty flimsy. It would be a good thing to cut down an APC prop, there is also an APC 5x5 I want to try.

I mounted the ESC on the motor arms, that gave plenty of room in the battery compartment.

You can see what I did in my blog.

Good building, it's a fun little boat.
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Old Dec 28, 2011, 07:39 PM
Row 0, Seat A
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Quote:
Originally Posted by nioa View Post
Hi Ted,

The stock prop is pretty flimsy. It would be a good thing to cut down an APC prop, there is also an APC 5x5 I want to try.

I mounted the ESC on the motor arms, that gave plenty of room in the battery compartment.

You can see what I did in my blog.

Good building, it's a fun little boat.
Saw your build log and all was good . I'm trying a few things a bit different but still haven't decided on all of the details.

I plan to order an APC 5x5 as well. Also the 1:18 car ESC. I like the idea of having a reverse function and like it's small size.

Ted
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Old Dec 29, 2011, 09:37 AM
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Quote:
Originally Posted by nioa View Post
Hi Ted,

...
You can see what I did in my blog.

.....
Where did you put your 3S 1300 mAh Lipo?
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Old Dec 29, 2011, 11:13 AM
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Qwlpic, see image 8 in my blog. Notice that there is a piece of Velcro on the bottom of the battery compartment. That is where the battery goes.

I am going to remove your duplicate question from my blog, since it has been answered here.
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Old Dec 30, 2011, 06:27 PM
Row 0, Seat A
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Savannah, GA
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Finished the build today and played around with it on the front lawn. Great fun! Looking forward to getting it wet.

I did a couple of small mods just to open up room in the equipment bay.

Ted
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Old Dec 30, 2011, 08:23 PM
Heli and E-Plane
United States, FL, Ocala
Joined Nov 2010
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Originally Posted by G550Ted View Post
Finished the build today and played around with it on the front lawn. Great fun! Looking forward to getting it wet.

I did a couple of small mods just to open up room in the equipment bay.

Ted
Looking good Ted - nicely done!!!
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Old Dec 30, 2011, 08:58 PM
Row 0, Seat A
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Savannah, GA
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Originally Posted by jer291113 View Post
Looking good Ted - nicely done!!!
Thank you.

I sealed the ends of the ESC with silicone to hopefully make it water tight. Used a line of CA on the end opening of the RX for same. Probably should coat the servo shaft, pin end of Rx and bullet connectors with Vaseline. My hull to deck caulking is loose like every one else has noted but I'm not concerned with that for now. Gonna have to figure out something to seal the ESC wire through bulkhead fitting but don't want to use anything permanent like silicone (maybe some plumber's putty), and will rely on surface tension to minimize any water entry through the push rod fitting.

I use a micro coax heli to "exercise" the cats. I suppose the Swamp Dawg could do the same for the geese in the pond.

Ted
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Old Dec 31, 2011, 06:46 PM
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3S 2200mah battery

I am just able to fit a 3S 2200mah Lipo in diagonally, with the inside deck still on, and everything else below it. Since my ESC is a car-with-reverse type, it comes with an on/off switch. I am thinking about only bringing a charge plug out and caulk the hatch closed.

I live on the Piscataqua River in Maine and the water is salty on the rising tides. (The river rises/falls about 10feet 2 times per day)
I am going to soak everything in Corrosion-X ... it is amazing stuff.
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Old Jan 17, 2012, 06:54 PM
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United States, LA, Winnfield
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Hi folks,
Got my dog in today and have a question.Will this car esc work??
http://www.hobbypartz.com/ezrun-18a-...or-rc-car.html
I no its only 18a but I hopeing it will be ok.

Thanks
Tom
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Old Jan 17, 2012, 08:36 PM
Heli and E-Plane
United States, FL, Ocala
Joined Nov 2010
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Quote:
Originally Posted by deadaim57 View Post
Hi folks,
Got my dog in today and have a question.Will this car esc work??
http://www.hobbypartz.com/ezrun-18a-...or-rc-car.html
I no its only 18a but I hopeing it will be ok.

Thanks
Tom

Hi Tom
I wouldn't, the bec is 6V so not so good for the servo.

I used the HK Turnigy 18A esc and it works great!http://www.hobbyking.com/hobbyking/s..._Car_ESC_.html
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Old Jan 17, 2012, 08:51 PM
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United States, LA, Winnfield
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Well I didn't really want to order from HK,take's to long.Is there anywhere to get one here in the usa?
Do you have to use a car esc to have reverse?
Thanks
Tom
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