Is "moving the stern drive" a bad idea ?

Discussion in 'Boat Design' started by Doodler 2, Jan 23, 2018.

  1. Doodler 2
    Joined: Jan 2018
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    Location: Oregon USA

    Doodler 2 Junior Member

    As asked in my recent thread, "Has anyone ever tried moving just the outdrive".

    It looks like no one has ever tried this and had it fail. At least no one has said so.

    This is just an idea, not trying to sell this idea to any one. just asking.

    Has this really never been tried?

    Isn't this an example of the "benign mania----boat noodling" as Dave Gerr might say ?

    Not asking for directions, just thoughts on the idea or concept.

    So what is it?

    Too crazy ? Not possible ? Not worth the trouble ? Why bother ?
    What's wrong with you? It might work, but would not try that myself ?
    Not worth answering ? Never heard of such a thing?

    As far as a goal as to why, I will reply with:
    Trying for a small increase in performance, while using low cost recycled parts, as well as the parts and equipment already on hand and in use, and my own time, labor, and experience.

    My wife is sold on the boat we built, does not want another, even if we could.
    What's left is making the most of what we have.

    Replies Requested. Thank You in Advance. kent r
     
  2. Doodler 2
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    Location: Oregon USA

    Doodler 2 Junior Member

    Just for reference, here is a pic of the weekender fishing boat, "Flotsam", july sunshine 036.jpg being considered for mods. Picture now 3 years old.
     
  3. Angélique
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    Angélique aka Angel (only by name)

    Hi Kent, also consider adding stern floatation pods, as deep as the hull, and outside as wide as the hull, and between the pods as narrow as is possible for the outdrive's movements, and a swim platform on top over the pods, about as high as the current swim platform or a bit higher, and this all stretching aft as long as is needed to get enough added volume below the waterline for the needed extra floatation.

    This would be far easier than a complete hull extension and moving the drive, while stern floatation pods also could do the trick, I believe.

    The outdrive would then be between the newly added floatation pods.

    Below an example on a smaller boat . . .

    [​IMG]

    Good luck !
     
    Last edited: Jan 24, 2018
  4. Angélique
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    Angélique aka Angel (only by name)

    If want to know how much added floatation is needed, then park the fully loaded boat in the water below a bridge, hoist the stern to the bridge with a scale till the required new aft waterline, read the scale, and add to the read weight the estimated weight of the yet to build stern floatation pods, or whatever stern adds on you decide to.

    Below another stern floatation pods example, here with an outboard which precludes a continuous abeam swim platform, which is possible above an outdrive...

    [​IMG]

    [​IMG]
     
    Last edited: Jan 23, 2018
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The steering swing of an outboard takes a whole lot less space, than an outdrive leg. It's simple enough to figure out, swing the drive from "lock to lock" and see how much area needs to be vacant. I think you'll find the trim cylinders will eat into the volume you have available, possibly enough to make the modification not worth considering. Only the swing test will determine how much of a notch you'll need.
     
  6. Angélique
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    Angélique aka Angel (only by name)

    If the stern floatation pods turn out to be not viable with the movements of the out drive leg, then we'll have to go back to the original question in post #1, I'll guess.

    P.S. - Here's the initial thread of this topic.
     
    Last edited: Jan 24, 2018
  7. Doodler 2
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    Location: Oregon USA

    Doodler 2 Junior Member

    The "Stern Flotation Pods" have a lot of points in their favor.
    Right at the top is cost, simple construction, and leaving the basic hull as it is. I would remove the "Doel Fins" I'm using, or make a bigger notch.

    I had given a passing thought to this idea, while adding the swim platform, but had not seen it done yet. Thanks for the pic's.

    Another benefit using these would be that the pods could be made, then installed later, with very little down time.

    As for finding out the final shape, and missing the outdrive, that's the kind of "shade tree engineering" I am used to.

    The starboard side will be easy, and could be lightly built. The narrow transom hole a Murcruser uses would leave more room for "pods".

    The port side will have some complications, needing to also support the trolling motor.

    When thinking about, and doodling around with moving the outdrive, I was planning on using a second transom, cut from some old unwanted
    hulk, that would resist the twisting from hanging the troll motor out in space, the load shared across the entire width of the old transom.

    Using pods, the full weight will be one one side, like it is now, and the currant motor bracket is made from recycled aluminum truck bumper,
    1/4" thick, and built strong enough to handle a much bigger outboard than the 10 hp Honda.

    However, that bracket only holds the motor 17" out from the transom.
    I was planning on an extension of 24" to 30". Swim platform is now 21", and is "notched" at the troll motor.

    Here comes more compromise and or trade offs.
    Much smaller pods, to position the troll motor where it is, or an even bigger notch in the port pod, to allow room for turning.

    With the bottom planing surface already notched out for the outdrive, and then notched again for the troll motor, and reduced in length to keep
    the troll motor from being so far back as to tear off the pod while trailering , the overall benefit of adding the pods is reduced.

    I'm using the "welded" on hull extensions found on newer aluminum fishing boats as a reference. They are long, two to three feet, but strong enough
    to support two 300 hp outboards. A little trolling motor hanging out there, almost like an afterthought, looks safe.

    I am not so sure about having the same 10 horse hanging 20 or 30 inches out on a pod.

    Lots to consider before building anything.

    While I am hesitant to make assumptions, it does seem as if no one has ever tried moving just the outdrive back, never thought of it,
    or most think it is a bad idea, and not worth the time to refute.

    Special thanks to Angelique, Par, and Berry, for replying to my questions.

    kentr
     
  8. Angélique
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    Angélique aka Angel (only by name)

    It seems that's the case here.

    Another option could be to take a sawzall (reciprocating saw) at her, and saw her hull transverse through just before the engine, and put about 4' in between.

    This is also how the carrying capacity of cargo ships usually is enlarged.

    Flotsam.jpg

    Flotsam extension.jpg

    P.S. - - - - Oops sorry, forgot to move the port canopy pole backwards when extending the hull . . :oops:
     
    Last edited: Jan 24, 2018
  9. Angélique
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    Angélique aka Angel (only by name)

    I'm thinking about thick marine plywood here, that's connected to the hull by Payson Butt Joints, then this all should be epoxied and glassed over.

    Also frames abeam to the boat should be put over the joints I think. And a good number of fat longitudinal stringers should be put in, they should run far into the GRP hull on both sides of the extension. The stringers' pass should be notched out of the new frames, I believe.

    See PAR's website ---> Liquid Joinery - (see also Scarf Dimensions and Epoxy Tips & Tricks)

    Here's a Payson Butt Joint for plywood, think of one side being the GRP hull.​

    [​IMG]
     
    Last edited: Jan 24, 2018
  10. Angélique
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    Angélique aka Angel (only by name)

    The engine also moves backwards this way, but I'll think the extended hull has enough aft carrying capacity for that.
     
    Last edited: Jan 24, 2018
  11. Doodler 2
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    Location: Oregon USA

    Doodler 2 Junior Member

    That's a great pic. If only I could download the pic, print it out, and load it on the trailer, ready to fish.

    I have seen some of the stretching and beam building at local shipyards. Mostly steel fishing boats 50 to 80 feet, or 7 feet on each side.
    Just added on the sides, a bit more topside, and who would know, now it's a big boat.

    The stretching is not an option for me. Way too much time, effort, and money involved. But I like the look, and the performance would improve.
    Also,I used the stripped down hull as a building jig, the stringers were new, and two inches taller than original, would not cut them.

    The missed post is fine, but I'll need another axle, a lot more steel for the trailer, more money for the yearly license, and a bigger truck.

    Some kind of pods looks to be a viable option, even if smaller or shorter. They could directly replace the present swim platform, gain some
    performance, stay in budget, and not need to change any cables or hoses.

    A wild guess at price would be around $200 to $400 for wood/fiberglass. Using polyester resin, not epoxy.
    Or around $500 to $800 for aluminum. I have a welder for aluminum. First choice would be aluminum, to save weight, and avoid wood rot.

    The wood/fiberglass approach, possibly partly from an old boat, could be bolted on and braced with a fiberglass patch to the hull.

    The aluminum would need to rely on bolts, but I am using bolts for the swim platform and braces already.

    Please note one more attempt at humor. I have built this boat to 100% using the 85--15 plan. Aim for 85% of perfect, and to last for 15 years.

    Seriously, we need to use flossie when we're still able, that means now, not leave a perfect, finely finished legacy for grandkids to sell.

    kent r
     
  12. Angélique
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    Angélique aka Angel (only by name)

    Wise words Kent, I'll think the below vid shows an example of the latter, and Dr. John also lost a foot in the process (a foot, not meaning 12") . . :(


    Magnificent boat though, I have to salute him for that . . :)
     
  13. Angélique
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    Angélique aka Angel (only by name)

    Polyester resin doesn't stick well to cured polyester, little holding power, best check this first.
     
  14. Doodler 2
    Joined: Jan 2018
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    Location: Oregon USA

    Doodler 2 Junior Member

    Not only a magnificent boat, but a magnificent story as well. There is a legacy worth leaving. Not just the boat, but the true story as well.

    My life and story have been, and are still very different.
    First off, my time and resources have been very divided, and spread out thin. Too many irons in the fire. Not enough time spent on one heading.
    But that's OK, and it's too late to relive it.

    There is another quick story as to how I came up with the 85--15 plan.
    About ten years ago, I was walking the docks in Florence, Oregon, and taking pictures. There was one 40' power boat there, and the owner was on board.
    Got invited in to see the inside, and hear the boats story.
    The inside was, and still is, over the top. Stunning. Nautical themes, hand carved features, more than 1,000words can tell. The outside is unique as well.
    All hand built, with obvious love and dedication to detail. It took the man over 10 years to complete the inside. All in his backyard, up in the hills,
    30 or so miles from the NW water front. Then, just before launch time, he had a heart attack, and passed. There was no one in the family who wanted to
    finish off and keep this boat. The currant owner, who had spent years rebuilding and rigging boats down in SF, picked it up for next to nothing.
    He had it launched, motored down to Florence, was living aboard, and finishing off the outside and flying bridge.

    That's when I started thinking about being able to use what I had, when i had it.

    i was 64 when we started planning and building Flotsam. And this was more out of need, than a dream.

    When fishing a local coastal lake one fine summer day, after 14 hours on the water, I say to my wife, "That's enough, I'm done, let's head to the dock."
    And she replies with, " But I've still got some worms left." Did I mention she likes to fish? She looses all sense of time.

    This was when using our old converted ski boat, a 1986 Invader, with a walk thru and bow rider. A better fishing boat than what we now use,
    because of the better access to the water, but no real room to spend the night.
    The next day i started the noodling and doodling that led to Flotsam.

    using the 85---15 plan, things can happen fast.

    As far as using polyester resin, i would not rely on it for complete strength if used for add ons. Just for part structure, and fairing in.
    When used this way, i have ground rough into any surface to give it a chance, and made scarf joints similar to the "Payson Butt Joint" you
    posted before. This method has proved itself for this build, at all the topside seams made piecing together the fiberglass panels used to "assemble"
    what looks like, and acts like a boat. Flotsam is a fitting name.

    What were you asking me to "check first" ? "Motherland"?
    Beautiful voice. Music is one of the "other" directions my life has taken. I can and do appreciate a good voice. And a soulful, moving song.

    Guitar and banjo have been my instruments. The last 30 years mostly banjo. Some bluegrass, but also folk, country, blues, and gospel, mostly gospel.
    Not really into rock any more, went back to country in the early 70's. Freedom to choose is a good thing. And taking a banjo along when fishing gives
    me something else to do, while she is so focused on fishing for hours at a time.

    Thanks again for your replies. kentr

    PS. side note. The "b" in the e-mail address stands for "banjo'
     

  15. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    Hi Kent, ‘‘best check this first’’ was about the foregoing line, meaning when you want to apply polyester resin to glue something to cured polyester, then best first check whether it has enough holding power for what you want to attach firmly with it, because expecting firm structural values would be a mistake.

    Although to check on ‘‘Motherland’’ by Natalie Merchant isn't a bad idea either . . :cool:

    Good luck with Flossie's mods, and keep us posted please . . :)
     
    Last edited: Jan 26, 2018
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