how about joining two aluminum runabouts at transom for faux "long boat"?

Discussion in 'Boat Design' started by Squidly-Diddly, Jun 14, 2013.

  1. Squidly-Diddly
    Joined: Sep 2007
    Posts: 1,823
    Likes: 143, Points: 63, Legacy Rep: 304
    Location: SF bay

    Squidly-Diddly Senior Member

    Hopefully two that don't narrow towards the stern but have gunnels going straight back.

    Idea would be easy, big, safe, durable row boat for casual use that would allow for 1-8 rowers and lots of gear, and row better than a single conventional aluminum fishing boat and be more practical to transport than a real 24'-32' foot long row boat.

    Mostly rowing short distance to fishing spot or 'picnic on the lake' for tourist resort.

    Maybe mount elec. trolling motor on "stern"(bow) of one half.

    Sun shade awning.

    Easy to 'mothball' during off season, or use both boats as designed for hunting and fishing.

    Instead of spending mega bucks on purpose built "proper" boat.

    For some reason I'd really like a big "long boat" but don't want to blow upwards of $10,000 on a boat that will also be a real hassle to store and transport.
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,401
    Likes: 1,033, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    You mean back-to-back, so the bow of one turns into the stern of the combined pair ? Damn nuisance that transoms are raked, and you can't just bolt the two faces together. Filling in that gap while maintaining lengthwise structural integrity would be a job. But you'd think it would row pretty good.
  3. messabout
    Joined: Jan 2006
    Posts: 3,217
    Likes: 368, Points: 83, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Intriguing idea there S-D. That would not make the best rowing boat but it might be well suited for partying and picnics.

    The tandem boat would have excess wet surface, and be difficult to turn, but not impossible. The biggest problem would be to invent a reliable joiner mechanism. Not too big a deal to make up a wedge shaped filler piece but to get it all bolted together so that it would stay together could be problematic.

    The joint would need to be very secure because it will be periodically exposed to cantilevered loads which could be pretty significant. If the joint failed and did not wreck either transom the now separate boats could row off into the sunset according to whim. Two piece, even three piece boats have been done with satisfactory result. Some of those Bolger oddities for example.

    My evil mind springs to a pair of purpose built, cheap and dirty, garveys with plumb transoms, parallel sided, about 36" wide at the chines. Such a boat could support 1400 pounds at about six inches of draft. It might row well enough to get some good fun even if lacking efficiency.
  4. MoePorter
    Joined: Nov 2012
    Posts: 41
    Likes: 2, Points: 0, Legacy Rep: 22
    Location: Oakland,CA

    MoePorter Junior Member

    Great idea. 24' length would be pretty reasonable to trailer, integrate a keelson/seating/platform structure to deal with the "cantilevered loads which could be pretty significant". If you could figure out a way to mount a 10hp on it (a well?) I think you might get a bit of speed out of it before it squats too much...or a 4hp off to the side would put-put you around ok for partying. Maybe too much windage for electric trolling depending on the conditions? But electric/rowing hybrid drive has possibilities... Don't think too much of the pure rowing idea - I think non-slave crew boredom would be the limiting factor - and you'd need a crew...but if they ran on cheap beer...
    Memories are the payoff & for the $$$ (well, one $...) and the time spent you'd get years of good ones...Only caveat is you need a big family or lots of friends to make it "pay". Moe
  5. keysdisease
    Joined: Mar 2006
    Posts: 794
    Likes: 43, Points: 28, Legacy Rep: 324
    Location: South Florida USA

    keysdisease Senior Member

  6. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 148, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    I like the idea, to make it strong enough you would want some fittings that go from where you bolt it together to the chines and gunwales to distribute the stress loads from the connecting hardware to the gunwales and chines.

    I would also think you would need a detachable skag or a fixed rudder to keep it pointed forward. Otherwise it will want to swap ends too easy I suspect.

    rather than taking two existing boats, it would be better to build them to the purpose of course, otherwise, as noted, the two shorter hulls will have very large loads introduced the structure designed for a much shorter hull. Otherwise using two existing boat hulls, and reinforcing them to make it strong enough, would result in a pretty heavy hull.

    I had designed and built a take apart skin-on-frame kayak, it had bulkheads where it comes apart and I used over-center buckles to hold it together. It was simple and assembled fast because there were no loose parts or fittings to install, and no nuts or bolts to drop in the harbor.

    There was some one on this forum that started a thread on building two transom canoes and attaching them at the transom to make it a longer traditional canoe.
  7. bajansailor
    Joined: Oct 2007
    Posts: 2,662
    Likes: 988, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

  8. Village_Idiot
    Joined: Oct 2007
    Posts: 382
    Likes: 16, Points: 18, Legacy Rep: 138
    Location: USA

    Village_Idiot Senior Member

    I had thought about doing this several years ago. I think the most elegant implementation would be a third piece that is custom built for the two (identical) boat transoms, with integrated shims. The piece would be large enough (2m? length) and designed such that outboard motors could stay attached to the transoms and merely lifted full-tilt to clear the connecting apparatus. Thus it can be converted from a longboat to two powerboats with little time or trouble. A design could even be fashioned whereby one motor could stay tilted down and provide midships propulsion for the joined craft.

    Now that I've disclosed this idea, I'm sure it will be snapped up and patented by someone. Just remember, you heard it here first! :D

  9. Squidly-Diddly
    Joined: Sep 2007
    Posts: 1,823
    Likes: 143, Points: 63, Legacy Rep: 304
    Location: SF bay

    Squidly-Diddly Senior Member

    Idiot and Petros

    Idiot and Petros.......

    yeah, I've thought about the "3 member" and outboard well, or just 3rd piece to fill in the gap of sloped transoms of typical alum boats.

    I've noticed on many alum boats that keel extrusions will be truncated just before the transom, so there is an inch or so of flat bottom and sides to work with, which might accept some sort of canvas fill piece. Drill one small hole into the keel extrusion to pull line tight from gunnel to gunnel and stretch a piece of canvas to get a bit of streamlining. Don't worry if the gap then fills with water, it will just be a little damping sloshing around in there.
    Then set an "H-frame" over the top of transomes and gunnels with the middle of the "H" on the transomes and the legs providing stiffness clamped to the gunnels. Add a fittings for mast for small sail or awning.

    I also think just a couple of heavy duty door hinges screwed to pads which would be in turn clamped the transoms near the gunnels would be fine for this application and it would be OK if the boat two halfs flexed with the waves or shifting passengers.
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.