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Old Feb 06, 2007, 05:42 PM
Jose A.
Vila Real, Portugal
Joined Nov 2004
147 Posts
Discussion
Electric wild thing

I just starting in boat RC (some experience in airplane RC) and decided to build a Wild Thing with 60cm long.
I am using a 700 bb turbo 9,6V motor with flex drive system, with 8 NiMh cells of 3300mha.
Would this combination work for this boat (more or less 1600g final weigth)? Would a 40Amp speed controler handle this withou overcharge?
Does the motor with this bateries need water refrigeration?
Do I need strakes?
Where should be the CG?
Any other sugestions are wellcome.


Josι Almeida
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Last edited by malmeida14; Feb 06, 2007 at 06:13 PM.
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Old Feb 07, 2007, 06:42 AM
Registered User
Joined Apr 2006
916 Posts
C.G as a rule of thumb should be 1/3 rd forward of the transom.
I don't know that a 40 amp would be ok.It depends on your prop size ultimately.
Perhaps try moto-calc or similar,for an amp estimate.
What prop size do you have?
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Old Feb 07, 2007, 08:08 AM
Jose A.
Vila Real, Portugal
Joined Nov 2004
147 Posts
It's a diameter 4cm prop.

In airplanes (I just arrived from airplanes) we also need to take in account the pitch of the prop to calculate the amp drown. But I don΄t know that data.

The battery came from a Junior 60 (oldtimer airplane that I have), replaced by a 3S1P 3200 LiPo (almost half the weight!!!).
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Old Feb 07, 2007, 02:52 PM
Registered User
Davenport Iowa
Joined Jan 2006
174 Posts
Wild Thing

Hi
Your boat looks good to me .Nice work. The motor size is good for this boat but, It will be dreadfully slow. The 9.6 700 isn't very fast anyway and on only 8 cells it may not even get on plane. If you want your boat to run fast ,you will need at least 12 cells with this motor.14 cells will be better. Using 12 cells and a good prop (Graupner CF K45) you could get about 40kph. If you installed a 8.4 700 and ran 12 cells 45kph or more could be possible. I build and race 700 powered boats like this and know what they will do. Please give this some consideration as I know you would be much happier with the results. n.h.schmidt
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Old Feb 07, 2007, 06:59 PM
Jose A.
Vila Real, Portugal
Joined Nov 2004
147 Posts
Thanks Schmidt,
I'm already convinced that I need an extra four elements for this boat, even though my first obejctive was simple building a boat that would be my first boat.
I have this vicious thing of building instead of buying airplanes RTF's and now boats RTR...
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Old Feb 08, 2007, 03:59 PM
Registered User
Davenport Iowa
Joined Jan 2006
174 Posts
Wild Thing

Hi Jose
I like to scrach build too. I make almost everything. If your ESC can work with 12 or more cells You will be ok. A 50 amp limit is good eneough for 700 motors. I have run a 50 amp Astro Flight Boat ESC for some time now. Your boat will work better with lifting strakes. Two on each side is good. The wild thing is a good ,fast boat. You should have a fast boat when you are done.
n.h.schmidt
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Old Feb 08, 2007, 05:49 PM
Jose A.
Vila Real, Portugal
Joined Nov 2004
147 Posts
My speed controler handled 40amp and 12 cells.
I have just finished soldering all the electronics and run the motor alone with the 8 cells. Everything gone wright.
I am living in a small town, and the near hobby shop is 100km away, so I will mount everithing with the 8 cells, run the boat and the then, if it runs well I will build the 12 elements battery.
I will build the two strakes.


Is out there any electric wildthing?
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Old Feb 14, 2007, 12:14 PM
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edmonds, wa.
Joined Aug 2003
37 Posts
Nice boat, But it looks like you have about 4 or 5 degrees of down thrust. Make the prop shaft even with the keel. Once she's on the water you can use the bats. and trim tabs to dial her in.

Brian.
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Old Feb 14, 2007, 05:15 PM
Jose A.
Vila Real, Portugal
Joined Nov 2004
147 Posts
OK, you are 200% right,

But the drive shaft is flexible so it can assume from -5° to 0° in the present configuration. Unscrewing the two screws (A) we can move the shaft downwards, fixing it in the optimal position. Also, since the shaft direction change with the ruder, there is no need to trim it with a small angle to the longitudinal axes.

The only problem is that the if the need for correction would be bigger then the possible physical correction.

Now I have a problem ahead, how would I build a system to the openings in the upper deck, to keep the interior dry. The system that I draw will work? (see the two images open and closed)
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Old Feb 14, 2007, 06:47 PM
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1,617 Posts
I use hockey tape to cover the gap between hatch and hull/deck.
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Old Feb 27, 2007, 03:33 AM
Jose A.
Vila Real, Portugal
Joined Nov 2004
147 Posts
Ok the building process is going (very slowly!!...)
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Old Mar 20, 2007, 11:19 PM
Registered User
North seattle
Joined Oct 2006
36 Posts
Nice boat!
I built a small (20in) electric foam version, and I think that it is a great design. Very stable and capable of decent speeds too.
Good luck with the rest of your build!
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Old Apr 09, 2007, 02:47 PM
Jose A.
Vila Real, Portugal
Joined Nov 2004
147 Posts
The building process is going slowly.

With a L shape plastic profile (10mmX10mm) I made a spray rail.
It might be bigger than it should since:
For the 123cm (48”) version we have a spray rail that goes down 6,35mm (0,25” - 1/4”) so for the 61,5cm (24”), well more correctly 66cm (26”) - my plans have grown in the printer... - version it should go down 3,43mm (0,135” ). In my case I have 4mm (0,157”) instead of 3,43” (0,135”) - A in the image and 10mm (0,393”) for B in the image. I hope that doesn't alter the boat riding.

The whole thing was fixed by epoxy glue and then covered with fiberglass.
This approach make my spray rails very resistant to impact and protect the upper side of the boat, which was built very light and more fragile with 1,5mm (0,381”) balsa cover.

I didn't make stracks because I have read that this model doesn't need them.

I also made a cockpit to close the boat. The windscreen must be cleaned...and the rear part finished, I know.

You can see the boat with all the electronics already installed.

I was thinking that the boat was very heavy and want float!!! (I'm a man from the airplanes remember?!). Well at this stage I made an experience putting it in the water and it floats!!! There isn't much more height to put in, almost just the painting job. Is the water line correct?

I also try the boat with the motor almost stopped and I could made 2 meter turn (6,5 foot turn) very easy.

I'm considering a system of water refrigeration of the motor and speed controller, does anyone have suggestions for me?
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Old Apr 09, 2007, 06:56 PM
I like boats
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Brisbane Qld Australia
Joined Jun 2006
573 Posts
Looking really good there, I have been following this thread from the start with great interest as I have a set of 26 inch plans ready to go, it will be my next project after the one I am just about to finish. Have you had it running yet??
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