Downscale Riva plans. Will it cause problems?

Discussion in 'Boat Design' started by Toivo, Aug 22, 2017.

  1. Toivo
    Joined: Aug 2017
    Posts: 7
    Likes: 1, Points: 1
    Location: Norway

    Toivo Junior Member

    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
     
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,212
    Likes: 222, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    What form do the plans come in ? Not full size ?
     
  3. Toivo
    Joined: Aug 2017
    Posts: 7
    Likes: 1, Points: 1
    Location: Norway

    Toivo Junior Member

    They come in full size in PDF files
     
  4. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 144, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    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.
     
    Raffaele Frontera likes this.
  5. Toivo
    Joined: Aug 2017
    Posts: 7
    Likes: 1, Points: 1
    Location: Norway

    Toivo Junior Member

    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.
     
  6. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,212
    Likes: 222, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    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.
     
  7. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,212
    Likes: 222, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

  8. Toivo
    Joined: Aug 2017
    Posts: 7
    Likes: 1, Points: 1
    Location: Norway

    Toivo Junior Member

    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''?
     
  9. JSL
    Joined: Nov 2012
    Posts: 691
    Likes: 32, Points: 28, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    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
     
  10. gonzo
    Joined: Aug 2002
    Posts: 13,265
    Likes: 322, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    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.
     
  11. TANSL
    Joined: Sep 2011
    Posts: 5,490
    Likes: 152, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Why?
     
  12. gonzo
    Joined: Aug 2002
    Posts: 13,265
    Likes: 322, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Because the Riva designs are pretty much close to perfect.
     
  13. TANSL
    Joined: Sep 2011
    Posts: 5,490
    Likes: 152, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    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.
     
  14. gonzo
    Joined: Aug 2002
    Posts: 13,265
    Likes: 322, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    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.
     

  15. TANSL
    Joined: Sep 2011
    Posts: 5,490
    Likes: 152, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.