Outboard bracket Vs hull extension

Discussion in 'Boat Design' started by Bigtalljv, Aug 9, 2019.

  1. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    hi,

    I’m new but have been reading some other boat building forums for years. I rebuilt my zodiac with help from them and recently picked up another big project. Radon boats are a Santa Barbara California made boat that have a strong regional following. The 24x8 that I picked up is a classic and generally a benchmark for the area.

    Short story is the transom was a little rotten so I decided to fix it right and then decided that I’m going to full redesign/rebuild mode with outboards. The big question is how to decide between an outboard bracket and a hull extension? The biggest issue is that with these boats you can do anything you want. They were made in all various sizes and people have modified them every way possible and they all work great. So I can go anyway I want which is totally confusing.

    The manufacturer generally puts a bracket on them when they repower, used to use Armstrong’s and now in house built fiberglass like a hermco was, most boats came with IO decades ago but everyone is generally going OB now. Another local builder usually does hull extensions with about half being full width and half being about half width, allows for the trim tabs to be “recessed”. A friend just had that guy finish a half width extensions and it’s beautiful and performs great.

    I think some of it has to do with cost. For a repower on a functional good looking boat that needs a new engine the bracket is lots “cheaper”. If you’re tearing the boat down to bare hull and re-doing from stringers up a hull extension seems more popular. Could that be the deciding factor I’m missing? I’m tearing it all the way apart, fingers crossed the stringers are good.

    Sorry for the long winded first post. I’ve obviously been thinking about this too much and have succeeded in only confusing myself.

    The ugly boat is mine, the pretty boat is the model.

    Jason
     

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  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I would do as little as possible for as cheap as possible.
    However, if the transom and stringers are suspect...
    You'll have to open it up to see, and go from there, no?
     
  3. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    No, I’m going big on this. I do the work myself so that’s a cheap as possible but I’m going to make it as nice as I can. My time and effort is free so I want it done right.

    Transom is torn out and waiting for replacement. The stringers should be ok, the manufacturer did some work on it years ago but then the PO put some holes that he didn’t seal in a bulkhead so that needs to go. All the decks are coming out and getting lowered and the cabin will be several feet longer.
     
  4. Barry
    Joined: Mar 2002
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    Barry Senior Member

    My recommendation is to extended the hull with a motor well. I don't see a reason to recess the tabs.
    The further the tabs are back, the "better" they work. "better" being a given vertical lift force with a lower resistance. Ie less trim down angle of the tabs, for more lift
    The extra full width hull extension will provide a bit more aft buoyancy to handle the weight of the outboards. A full chine hull extension will provide a better lift pressure distribution at the back off the hull as compared to a partial hull extension.
     
    Last edited: Aug 9, 2019
  5. Magnus W
    Joined: Nov 2017
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    Location: Sweden

    Magnus W Senior Member

    If these various mods are indeed common I’d look around for the one that would fit your needs better.

    That said, bolt on bracket seems easiest and, to the untrained eye, seems to go best with the i/o setup as far as cg goes. Assuming they got it right to begin with.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    It seems you have answered your own question, and replicating that conversion would be the way to go.
     
  7. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    I also have a friend that has the same boat with an Armstrong bracket and the two boats before and the one after the boat pictured above had full width extensions. They all seem to work well so I’m totally confused on which way to go. Everyone is happy and I have no way to determine if any one way is “better” than another empirically.

    Jason
     
  8. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    You might need to have some at-sea experience with the various boats, to make your own judgement. ( Assuming all the same original hull). One thing I notice about the boat, the freeboard isn't overly generous, is that why you are lowering the floor ? Were they self-drainers ? How do you propose to deal with shipped water if not self-draining ?
     
  9. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    Water line is just below the highest edge. You can see on the green boat there are scuppers just above the water line. They are a good 6” below mine. This boat was going to be used urchin diving by the PO so they had low edges/high decks to crane stuff on to.

    Yeah it would be nice to get some rides. The green boat is 2x200 and the bracketed boat is 2x150. Although they are Honda’s so probably weight as much as the 200 Suzuki’s.
     
  10. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Since you’ve already got the transom torn out, I’d think it a no brainer to extend the hull full width, whether you incorporate it as a swim step or additional deck space is your option.
    Deck space may be needed if you extend the cabin.
    Radon’s are very parallel hulls so extending it is pretty easy, just sister on the existing stringers with generous overlap for strength.
     
  11. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    I fully agree with kapnD. If you really intend to tear out the transom, then extending the hull is a no-brainer. Figure out how much extension would counteract the weigh of the outboards as a guide for the minimum extension length.

    Why do you need trim tabs with outboards?
     
  12. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    If something has been proven to work well, the best course is to duplicate it. Some boats are less tolerant than others, to modifications, but if there is a spread of different, successful conversions, it suggests it isn't that sensitive a hull.
     
  13. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    I’ve spent quite some time both working from, and on Radon’s.
    Among the tradesmen, they’re known as “dump trucks”, very capable of carrying tremendous loads, and handling the horsepower necessary to move them. Not necessarily pretty, but beautifully functional!
    Extending the hulls to increase load capacity is probably the most common mod that is done to them, and with parallel stern sections and constant deadrise is relatively easy whether it’s a plywood hull or a glass one.
    To the OP, contact Don Radon, you may be able to purchase a molded hull piece that will fit your vessel, further simplifying your project.
     

  14. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    Thanks guys. Yeah it’s a brick. Or as the poster said later on a dump truck, that’s dead on. The 24’ has been made and customized in several feet in either direction. They can be made pretty enough and are just kind of perfect for out here.

    I have actually talked to don several times but before my current plans have developed. Perhaps I will check again about a molded section, that’s a great idea. His prices are kind of out of my league or as other have done I’d just drop it off and have him call me when it was done.

    Without getting too technical there is nothing magical about extending the hull is there?

    Jason
     
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