Deep V catamaran optimisation...

[Mr Efficiency]

Why emphasise speed for such a short hop ? Walking speed will cover 500 metres in 6 minutes.

 

[DCockey]

University project?

 

[upchurchmr]

And you want it to plane.
How big of an engine do you have?
How fast is fast enough? 6kts? 20kts?
Will you use a single outboard?
Will it ever carry people? 200KG could take 2 medium sized people.
To size the hulls you will need to know how heavy the boat will be by itself.
You seem to also say it will only operate in fair weather (30 cm)
Will it be controlled line of sight, or will someone have to dock it on the other side.
Will you put the cargo in the hulls or on a deck between them? Next question will be what kind of cargo - feathers or lead weights?
Do you want positive flotation or since you have not mentioned people will it be ok without?

You might look at Richard Woods Powercats.
http://sailingcatamarans.com/index.php/designs/6-powercats/262-skoota-20
Richard has some distinct opinions about efficient hull shapes - I've seen the discussion in his small trimarans section.

You might also look at the W-17 trimaran design, also with a flat bottomed hull - but this is a sailboat. http://www.smalltridesign.com/W17/greybox/W17-Trimaran.html

 

[CpDigriz]

Why emphasise speed for such a short hop ? Walking speed will cover 500 metres in 6 minutes.

It's a race, so it needs to be fast

 

[CpDigriz]

And you want it to plane.
How big of an engine do you have?
How fast is fast enough? 6kts? 20kts?
Will you use a single outboard?
Will it ever carry people? 200KG could take 2 medium sized people.
To size the hulls you will need to know how heavy the boat will be by itself.
You seem to also say it will only operate in fair weather (30 cm)
Will it be controlled line of sight, or will someone have to dock it on the other side.
Will you put the cargo in the hulls or on a deck between them? Next question will be what kind of cargo - feathers or lead weights?
Do you want positive flotation or since you have not mentioned people will it be ok without?

You might look at Richard Woods Powercats.
http://sailingcatamarans.com/index.php/designs/6-powercats/262-skoota-20
Richard has some distinct opinions about efficient hull shapes - I've seen the discussion in his small trimarans section.

You might also look at the W-17 trimaran design, also with a flat bottomed hull - but this is a sailboat. http://www.smalltridesign.com/W17/greybox/W17-Trimaran.html

The engine will be around 1.4kW with around 4Nm torque. ( i can give you more info if you need)

I am unsure as how to calculate the speed for it but i would like it to go around 10-15 knots maybe? The faster the better.

If i am interpretting correctly then yes, a single engine.

It wont carry people, only bricks weighting 200kg.

The boat shouldnt be heavier than 50kg without cargo.

It will be controlled at close range so yo will be able to see it.

The cargo will be seperated and placed in the hulls unless its better to place in between for some reason.

It will be ok without positive flotation.

 

[Mr Efficiency]

So it is now a remote controlled racing boat, that it is ordained must carry 200 kg of bricks, and be what, 2 or 2.5 metres long ? And it must be a catamaran of some sort ? I think you need to list the "official" rules governing this boat, and that way get some opinions on the practicality of it, but on the raw weights and dimensions you have provided, it will be a very slow race, perhaps relieved by fountains of foam and spray.

 

[Jimboat]

Hello. I have this task of designing a 2mx2mx2.5m dimension catamaran with deep v demi hulls...

Sounds like fun project, CpDigriz! Why do you want to use deep vee sponsons?

 

[CpDigriz]

Sounds like fun project, CpDigriz! Why do you want to use deep vee sponsons?

Deep v seemed like the best option for increased stability and maneuvering. Flat ones would be kinda bad i think...but im no expert, so...

 

[Jimboat]

Deep v seemed like the best option for increased stability and maneuvering. Flat ones would be kinda bad i think...but im no expert, so...

Lower deadrise sponsons would have better load-carrying capabilities.

 

[CpDigriz]

Lower deadrise sponsons would have better load-carrying capabilities.

what angle should i go for then?

 

[upchurchmr]

First figure out what shape will carry your 250kg (with motor?) in the 2 meter length.
I believe it will be quite fat, the deeper the V the fatter and/or deeper.
Deeper means it will not turn easy.

You ought to go for flat bottomed curved up on each end or a round bilged shape (won't carry as much weight for the same width and depth but it should have less drag).

A compromise would be to round the joint at the flat bottom to sides at the ends for less drag than a completely flat bottomed shape.

IMHO

Its never going to plane with as little of a motor as you have.

Again, IMHO.

 

[DCockey]

When does the hull design have to be completed?

 

[CpDigriz]

First figure out what shape will carry your 250kg (with motor?) in the 2 meter length.
I believe it will be quite fat, the deeper the V the fatter and/or deeper.
Deeper means it will not turn easy.

You ought to go for flat bottomed curved up on each end or a round bilged shape (won't carry as much weight for the same width and depth but it should have less drag).

A compromise would be to round the joint at the flat bottom to sides at the ends for less drag than a completely flat bottomed shape.

IMHO

Its never going to plane with as little of a motor as you have.

Again, IMHO.

Ok, what about a round bilged with a chine perhaps? Could it not go into semi-planing at least?

 

[CpDigriz]

When does the hull design have to be completed?

I have some time, but not enough to dilly dally =) if i could find some some of grip on this problem i would crunch the numbers and get myself a set of measurements for the dimensions, but i am so inexperienced I dont really want to create something too horrible

 

[upchurchmr]

What are the dimensions with a flat bottom for 250KG? If you don't know you don't have a clue if planing is in the cards at all.