Downscale Riva plans. Will it cause problems?

[Toivo]

Hi!
I'm new to boat building, and I'm planning to build a classic runabout in the coming years.
I've actually already ordered the plans for a Glen-l Tahoe, but when i saw the plans for the Riva Aquarama that classic wooden boat plans has, I'm thinking about ordering the Riva instead (since this is the boat I originally wanted). Only thing is that The Riva is 27'. My shop can only take a 23'.

Is there any problems with downscaling the 27' to 23'? I.e. 15%.
Will the balanse of the boat change? Handling?

Nicolay

 

[Mr Efficiency]

What form do the plans come in ? Not full size ?

 

[Toivo]

They come in full size in PDF files

 

[CDK]

You are going to see opinions here, but I doubt anyone can really predict how a 15% reduction works out.
There will of course be practical problems, like finding the scaled down materials, especially the hardware. You will probably end up with a boat that doesn't have the elegance of the original design.

 

[Toivo]

I don't think hardware will be a problem. I'm gonna make the wind shield myself. Other things like air intakes (half shells) bollards and so on, I'm not toing for original hardware, so I will just use standard sizes here.

 

[Mr Efficiency]

They come in full size in PDF files

Well, they won't be much use at full size, 27 feet. Your reduced boat, if uniformly scaled down, is volumetrically about 5/8 of the "real thing", so you need to take care. I think I'd prefer to have proportionally more beam, in a shorter version of it. It is not a simple exercise you are considering.

 

[Mr Efficiency]

An old, but possibly relevant thread:
Riva Aquarama https://www.boatdesign.net/threads/riva-aquarama.27795/

 

[Toivo]

Seems like this plan is full of potential pitfalls... My alternative is to make the free board taller on the glen-l Tahoe 23. I like the design of the boat, but I think the free board is too low, and the radius on the deck is too flat. I see that glen-l recommend not changing the plans, but are there any issues with changing the free board 2''?

 

[JSL]

If you "scale down" you should review and assess all aspects the new boat... as a new design.
I have seen some 'scale downs' go well (sort of) and others which were a disaster... in one case the boat was essentially a 'write-off'.
Not everything scales down to suit ... ie: people still weigh the same

 

[gonzo]

You will need proportionally less power, with an engine that is lighter to keep the same ratios. Also, the weight of the passengers will not decrease, so it will be a higher ratio of weight with all the stability problems it will entail. Modifying a Riva is insane. Even a qualified naval architect will have a hard time.

 

[TANSL]

Even a qualified naval architect will have a hard time.

Why?

 

[gonzo]

Because the Riva designs are pretty much close to perfect.

 

[TANSL]

It will be close to perfect or not, that's the least of it. I do not see why a qualified naval architect, as you say, may have any difficulty in undertaking that work or representing a hard work for him. That does not depend on the perfection of Riva's design but on the professionalism of the na.

 

[gonzo]

Not really. A Riva is a work of art. As such, the aesthetics are integral to the design. This would not be the same as modifying a barge. The NA would need to be an artist of the same level as the original designer.

 

[TANSL]

No one is speaking, in my opinion, of designing a new Riva.