Hi,
Dont be bogged down if the motor does not have water cooling. It is a fairly simple process to water cool motor and Esc.
First find the prop, as per standard design principles this should be done last. But since we do not have too many options of props... I suggest first select the prop then you can decide the motor and esc and then the size of the boat can be decided.

Shreekant

This brings up an interesting topic.  All the thrust and amps draw numbers for motors are based on operating with AIR as the medium, and it is obvious that when WATER is the medium, these numbers will not make sense.  The motor will have to do more work in water.  So is it common practice for people to just go with wattmeters, in order to decide what are the safe props to use etc ?

You must be very careful while dealing with (She/Sea/C- Language). Nobody ever understood any of these (Cs) completely. It is better to see all the Cs carefully before diving.

Let Ilango_slk start the build first, considering the consideration of weight & size, right kind of esc/ motor/ propeller can be selected very easily.

Hi,
I agree with Maharana, with boats., it is very difficult to calculate the prop size and then get the prop of the required dimension. It is apt that you start with the boat build . Any ways heres an ready made calculator for prop selection.
You need to feed the required parameters to get the appropriate prop dimensions.
http://www.rbbi.com/folders/prop/propcalc.htm

Also check out the Octura prop chart will give a lot of guidelines in prop selection.
http://www.funrcboats.com/prop_chart1.htm

Regards
Shreekant

I started looking for plans in the net and quickly found out that it is not going to be easy to find something that exactly matches my requirement!!! So started borrowing ideas from various models and developed my own for a single hull. This is just a prototype so I did some sketches and cut out the templates on a paper board (the board used for cartoons). so this is my first attempt of boat building...This template will be fine tuned when used for the actual boat..

Prototype on its way ....

Bottom..

Top..

Ok guys, before anyone starts trashing me let me explain that his is just a prototype to see if all the pieces work together. I have to make changes to keep this boat upright in the surf etc.,. Now that I have the template I will be able to work on wood or aluminum sheet .

Forgot to mention this prototype is 20" long and as I have the templates now I can scale to any size i want.

Try to make the hull like this....

Thanks for your input ANTA, the final version will be similar to that or else I will never be able to get my boat back from the surf. I want to make sure that I can make a boat first ... there will be a few more paperboard models before I start with wood or other materials. What do you think will be the best material ?? Thin Plywood, MDF , Cardboard (rough on one side and smooth on the other) , Aluminium sheets I also plan to do a fiberglass coat !!!

It is good to start up with cardboard prototype before getting on with the actual model.But I think scratch building a boat with a plan is advisable since it keeps out the worries of the dynamics of the boat.
My first scratch build had a weird problem as it moved ahead it dipped the nose down. I later realised that the transom was a little bigger.I do not intend to discourage you from scratch building your boat.. But changes to boat after built call in for too much of breaking.
Why dont you map your boat to some plans and then modify the plans a little to suit your requirement.

Shreekant

Shreekant, can you please check Reply 29 of this thread and see if the plan is ok??

Ok guys what is the best material for this type of job?? Balsa will not last long with the pounding of the waves.... any other suggestions ??

A rough idea of what Iam trying to replicate....

Aqua Cat Dinglehopper Turbo

Spec sheet
Dimensions: L 103cm, W 29cm, D 27cm (excl. antennae)
Weight: 14kg with batteries loaded
Radio System: 3 Channel 40MHz FM RC Set
Motor Transmission: Geared 1kw Brush-less Motor(fan cooled)
Speed Control: Electronic Speed Control
Battery Requirement: 2 X 9amp/hr 12v Lead Acid Gel Cells
Battery Operating Time:
- Power Propeller: 10min at full throttle, 12 – 14mins at 2/3 throttle
- Econo Prop: 14mins at full throttle , 15 – 20mins at 2/3 throttle
Maximum Distance:
- Power Prop: 1600m at full throttle (On one charge)1800m at 2/3 throttle
- Econo Prop: 1900m at full throttle (On one charge)2.2km at 2/3 throttle
Maximum Speed: 170m / min (Power Propeller)120m / min (Economy Propeller)
Battery Recharge Time: 2 – 10 hours (depending on battery condition)
Charging Requirements: 14.8v 2amp charger with automatic full charge turn-off

As mentioned in the above post, the Aqua Cat is using a single 1KW motor. Iam planning to use two smaller motors, what will be the best motor to use?? Any idea?

In the first video - I don’t think the weight of the boat is around 14 kgs (the way he was carrying it) something around 7~8 kgs utmost.  Now the specification sheet with 1 KW motor (unable to understand much of the information regarding Power Propeller / Econo propeller etc.) and now you want to alter it with dual propeller drive, but why?  Do you have a proper plan/sketch to do so ? 

Maharana, The video is for advertising and they naturally don't want to show that it is heavy... may be he was carrying without the batteries (two motorbike batteries can be heavy).

I was planning to change to two motors because I couldn't find much about the 1KW motor they were using I thought two smaller motors may do the same job.

As far as the Power and Econo prop they must be having two different props that can be replaced as per the requirement....

I have still not got any input on what material to use to make the boat, I have a feeling that only FG will be strong enough to survive the surf...what do you think??

I have got some plans for you which can be helpful to build this project (expecting little modification to suit your need) & let me know your email Id. Regarding fiber glassing, Sreekant can guide you better.

what is the min. price of a beginner electric boat?

Dear Maharana,

       Check your PM please.

Regards
ilango

Somewhere in the range of 50$ here in srilanka but very rare... why do you want to know??

I have a 12V DC motor with high torque... used in  normal cars. It takes pretty low current I tried my best to stop the motor by trying to hold the shaft by hand and it was impossible!! Tried with some cloth and measured the current when it was pretty slow and it read around 6A. Do I need an ESC to control this motor? if so what do you suggest.. by the way the motor is brushed.

Hey ilango_slk
You can use the following speed calculation and prop selection. It also gives you a lot of other selection parameters
such as current draw and speed based on motor KV selection.

http://www.offshoreelectrics.com/conversion.htm

Shreekant

Dear Shreekant,

        Thanks for the link. Iam still confused... If  Iam using a 12V 7AH battery and want a run time of around 60Mins what is the Motor size & Speed I will need

Ilango

I have a 12V DC brushed motor that was running my radiator fan removed from my car. It has pretty good torque and when I tried to stop it the amp meter showed around 6Amps. Will this ESC be ok for it

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160423930492&ssPageName=STRK:MEWAX:IT

Any suggestion for the Servo