Help with Rescue Minor supersized to 9x3m

[yodani]

Help with Rescue Minor supersized to 9x3m

Hi there,

I have a few questions about Rescue Minor and the possibility to supersize it. Please help me

The plan:

Length: 9m
Width: 3m
Material: Aluminium 4mm plate
Engine: 60hp diesel (350 kg aprox)
Fuel tank: 200 liters
Capacity: 20 persons

Can anyone help me calculate and estimate the following:

1: Draft loaded and unloaded
2: Prop diameter ? A bit superficial I know...
3. Cruise speed loaded and empty
4. Would it work just like the Minor? Or it will be hard to predict the behavior?*

What is your advice?

The boat will be used in fresh water on the channels of the Danube Delta.

Hope someone can help with this.*

Thank you*

[PAR]

You can't double the size of this craft an expect it to perform properly. You need a bigger inverted V, boxed keel design and Atkins has several. Boats don't scale up or down very well and certainly not when you take huge swings at it.

After selecting the new design, you'll have to have it converted to your aluminum build. I'd recommend "Nanuk III. It's 28' 7" on deck, it'll run 10 knots or so, but judging by the depth of her hook, you're not going to get her much faster then this.

[yodani]

Thanks Par,
I was not aware of the other tunnel stern designs of Atkin but after a good look on his website I found several plans, one of them is River Belle. I think I will buy the plans and see how it can be build from aluminium or even fiber glas. Any sugestions about that?

Thanks again,

Daniel

[Squidly-Diddly]

do much good?

Doesn't the whole wave action physics more or less scale (besides surface tension)?

Besides some major "human element" such as paddling ergometrics, what is the problem?

Is it a whole different game for planing VS displacement boat scaling?

PS-I can't help but notice a kayak can have the same hull form as a 20,000 ton armored cruiser.

[PAR]

It's the law of mechanical similitude and simple physics really. For example if Rescue Minor was doubled in size (very nearly the request above) it's weight wouldn't double it would go up by a factor of 8! It's wetted surface wouldn't double it would rise by a factor 4! Your observation of a kayak and an armored cruiser aren't remotely close to each other, though to the untrained eye, they might look similar.

This isn't meant as a dig at you. The question comes up a lot with designers. "Can I have this hull, just bigger?" "How about this hull, just half as big?" It's probably the most common request of designers and hugely difficult set of variables, that aren't easily over come. The usual reply is "Yes, but it will be a whole new design, that looks like what you want, though if carefully compared, there will be major deviations from the base line".