Design of Self propelled Remote Operated Canoe boat

[manon]

Dear All,
This design is totally new for me and I have to do this. Can you help me on this?

Principal Particulars so far:

LOA = 2.42 m
B = 0.456 m
D = 0.255 m
Disp required = 160 kg.
Speed = 8 knots

Boat Building Mat = Plywood+fiber glass.

I am puzzled with propulsion. This boat will be powered by battery which will transmit power to motor. Motor will transmit power through drive shaft to the propeller. Following youtube link will help.
https://www.youtube.com/watch?v=3wwqxzHLw1U

I am trying to calculated the thrust and propulsion power required in traditional way (Holtrop excel and hydro comp software). It gives me some weird result (May be giving right results but I am not understanding). Three files attached with preliminary calculations.

Pardon me for the inconsistent question, I have even doubt whether I could make a valid question or not. At this stage it will be very helpful if you guys please give me the guideline and way of power prediction/calculation for canoe boat.

 

[kerosene]

I am no pro but here is my take.

Seems that you have bit unrealistic parameters unless you have so much power that it planes. 8 knots for a 2.4 meter long boat is not an efficient speed. When you say canoe do you mean doubled ended like canoa/kayak, as in narrow points in both ends?

That will not plane. You can use fraction of the power for displacement speeds but top speed will be probably more like 4 knots.

anyway - I am sure some more aware person will reply too.

 

[manon]

Dear Kerosene,
Thanks for your reply.

you correct in you assumption. The Froude No is around 0.86 which is too hign. I have talked with the owner, but it seems they need this speed!

Any suggestion about propulsion and power?
P.S Sample file attached of the canoe

 

[messabout]

At 2.4 meters the boat will be constrained to less than 4 knots if built for displacement mode. You will need to abandon the canoe shape and design a planing hull. A 2.4 meter hydroplane can be coaxed to 30 knots or more. Not likely that you will do 10 knots with a displacement type double ender absent 25 kw of power or so. With that power it will be rather thrilling and dangerous. The hydro could reach the target speed with about 5 to 8 Kw. depending on the load the boat is to carry

The client does not have realistic expectations.

 

[manon]

Dear Messabout,
Thanks for your valuable comment.

I have already told the client about the fact. I have suggested already to change the hull from displacement to planning. But he wants to get stick to that specific hull shape as provided before. He does not care about the extra power required. So, can you please tell me, how it can effect the stability or how it can be dangerous in running condition?

P.s: it would be remote operated. I will carry some electrical equipment. total displacement would be 150 kg.

 

[kerosene]

You need to re-evaluate the whole thing. Its electric powered drone of some kind made of plywood, needing to travel at 8 knotts.

your client of sorts has decided on the parameters and also the hull shape and construction method? which equals: rounded displacement hull, planing speed, plywood.

Something needs to be changed. The only sensible thing to change is the hull shape as that will solve the 2 other issues: speed and construction. You cannot practically make said hull from plywood.

And to approach the situation by compensating with power (on an electric boat with limited energy storage) is not at all practical or in the least bit smart.

So I think your biggest challenge is to talk some sense to your client.

 

[manon]

You need to re-evaluate the whole thing. Its electric powered drone of some kind made of plywood, needing to travel at 8 knotts.

your client of sorts has decided on the parameters and also the hull shape and construction method? which equals: rounded displacement hull, planing speed, plywood.

Something needs to be changed. The only sensible thing to change is the hull shape as that will solve the 2 other issues: speed and construction. You cannot practically make said hull from plywood.

And to approach the situation by compensating with power (on an electric boat with limited energy storage) is not at all practical or in the least bit smart.

So I think your biggest challenge is to talk some sense to your client.

I keep trying to convince him about the hull shape, but he will go for the displacement hull. His last comment was as following:

'I appreciate your input on the speed/form of the vessel but we need to stay with the current design. In doing so, can you please explain what exactly is the issue (other then the obvious power curve) with this hull & corresponding Fn?'

So it seems that he wants to stay with his provided model and do not care about the required power.

What can be said now? Do you think, at this speed the boat will be lifted on at bow to a considerable amount?

 

[kerosene]

I am not educated to comment further. Take my words with grain of salt anyway as I ma pure hobbyist.

 

[messabout]

Manon; The statement of requirements (SOR) are so contradictory that failure is a near certainty. The world is generously populated with stubborn people who actually believe that they can violate the laws of physics by wishing it so. That is not to question their intelligence but it does question their technical education.

Your drawings show a pretty boat that would move happily and smoothly at two knots. At four knots it will generate a huge wave train, and at eight knots it might just sink itself by the stern.

Such a boat would need to be strip built or possibly cold molded with very thin veneers. No way it could be done with sheet plywood while retaining those pretty classical curves.

I wish you well with this project and we will all be interested in the final result.

 

[ConnClark]

So is this for running drugs or sinking ships?

 

[manon]

Manon; The statement of requirements (SOR) are so contradictory that failure is a near certainty. The world is generously populated with stubborn people who actually believe that they can violate the laws of physics by wishing it so. That is not to question their intelligence but it does question their technical education.

Your drawings show a pretty boat that would move happily and smoothly at two knots. At four knots it will generate a huge wave train, and at eight knots it might just sink itself by the stern.

Such a boat would need to be strip built or possibly cold molded with very thin veneers. No way it could be done with sheet plywood while retaining those pretty classical curves.

I wish you well with this project and we will all be interested in the final result.

Thanks for your reply. You are right, owner is not the technical person, its a project for him. If he is successful, he can get a big contract.....etc. He hired me as an Naval Architect and I never dealt with such type of boat and propulsion system. I is my job to guide him properly.

So far we have agreed to make a model first (model of such small boat, but I think its necessary to show him some obvious result). Hope for the best and off course I am going to let all know the results and give update to you guys.

Thanks for your help and guide.

 

[Squidly-Diddly]

Here is guy selling plans for wooden version of "Grumman Sport Boat" which as you can see is cross between canoe and 'runabout'.

IIRC they used to be rated for 25hp before USCG rule change, and they only weigh about 125lbs.

Now rated for 10hp, and I think they might be your best bet a 8knots on small motor, as well as still being lake-worthy

http://www.robbwhite.com/sportboat.html

 

[Mike Graham]

Thanks for your reply. You are right, owner is not the technical person, its a project for him. If he is successful, he can get a big contract.....etc. He hired me as an Naval Architect and I never dealt with such type of boat and propulsion system. I is my job to guide him properly.

So far we have agreed to make a model first (model of such small boat, but I think its necessary to show him some obvious result). Hope for the best and off course I am going to let all know the results and give update to you guys.

You say that he has hired you to guide him, but also that he isn't listening to you. That doesn't sound like the kind of client I'd want to have.

Best of luck.

 

[JSL]

I second Mike Garaham's opinion.

 

[manon]

You say that he has hired you to guide him, but also that he isn't listening to you. That doesn't sound like the kind of client I'd want to have.

Best of luck.

So far I understand, he has some mind set up. A owner can send reference design but cant suggest to follow exactly the same. I asked him several times about the speed of the boat boat that he has sent to me, but did not get any suitable answer.

So far the best guide I could made to him is to make a model boat at scale. Off course I will provide all the data and design for model. He will make the model and test.

(I wish that I will be able the make him understand the scale effect also!! I am afraid that, he will probably want to go for 8 knot speed for the model boat as well !! Pray for me!!)