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Thread: Bolger Otter question

  1. #1
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    Default Bolger Otter question

    Hello,
    As always, apologies if this is a dumb question:
    In Bolger's "Small Boats", I saw the Otter design. I read much (but don't really know anything) about boat building, so I wondered:
    Why does that build need all those temporary molds?
    Why can't it be built like so many of Bolger's smaller Instant Boats?
    I.e., assemble the sides, attach them to the main bulkhead, add transom and stem on one side, bend the sides together and connect transom and stem to the other side, then add the remaining bulkheads.
    Should this not give the proper hull shape? Surely, the molds don't stay in the boat (as they are "temporary")?
    Is it that those long sides would be too floppy to assemble them Instant-Boat-style?
    The 20-ft Zephyr in "Instant Boats" is built "like all the other instant boats", and does not seem to need the molds.
    Thank you.
    Matt

  2. #2
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    Default Re: Bolger Otter question

    For a bit more discussion see the older thread at http://forum.woodenboat.com/showthre...-single-hander

    The line of instant boats are very cleverly designed around how plywood bends with just three stress points. The shape of the Otter has very different curves. If you make a very accurate, properly squared, ladder frame strong back to support the molds, you'll find the planking perfectly straightforward.

  3. #3
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    Default Re: Bolger Otter question

    Yes, thank you, I have seen this thread a while ago already. Very interesting, all the suggestions made there...
    For Otter, I just wonder that even if one were to use all molds, then put the bulkheads, and removes the mold once "everything" is put together, the bulkhead will/should keep the boat in the shape desired. Without the molds. So why use the molds in the first place, when the bulkhead are supposed to hold the shape?
    Again, I don't know much about this, it just seems that when the molds are removed, the boat would take the shape that the remaining bulkhead dictate, independent of what it previously was.

  4. #4
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    Default Re: Bolger Otter question

    Because the boat's shape is held by the edges of the panels being glued together. Without the intermediate forms, it will be difficult to get the edges together.

  5. #5
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    Default Re: Bolger Otter question

    Quote Originally Posted by Mattokun View Post
    So why use the molds in the first place, when the bulkhead are supposed to hold the shape?
    Again, I don't know much about this, it just seems that when the molds are removed, the boat would take the shape that the remaining bulkhead dictate, independent of what it previously was.
    Easy enough to try it with a model.

  6. #6
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    Default Re: Bolger Otter question

    Once the hull seams are fastened, the shape won't change as the molds are taken out.

    Loft the plans 8:1 (1-1/2" = 1') and make a model with the same construction methods - ladder strong back, station molds firmly braced, and planking by modeler's balsa. You can hold the planks and bottom to the molds with push pins. Use strips of some fine fabric set with epoxy to fix the seams. Once it's cured, you will see how the seam itself holds shape with the planks. And it's a great exercise in being sure you understand the design. Every hour on the model will save a first time builder at least thirty hours on the final build.

  7. #7
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    Default Re: Bolger Otter question

    Yes, I'm already starting that. Of course, it's kinda hard to scale the material thicknesses... but yes, I want to see how this all works out. Also, I may do this twice, once with the molds and once without, to see how the whole thing behaves and shapes in the end. I even made myself a scale homunculus to see how much space there is in the boat, how accessible the cuddy is, etc. Fun stuff! Thanks!

  8. #8
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    Default Re: Bolger Otter question

    Quote Originally Posted by Mattokun View Post
    Yes, I'm already starting that. Of course, it's kinda hard to scale the material thicknesses... but yes, I want to see how this all works out. Also, I may do this twice, once with the molds and once without, to see how the whole thing behaves and shapes in the end. I even made myself a scale homunculus to see how much space there is in the boat, how accessible the cuddy is, etc. Fun stuff! Thanks!
    Instead of planking with balsa wood, use cardboard. Cardboard behaves more like plywood anyway.
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
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  9. #9
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    Default Re: Bolger Otter question

    Should have mentioned that... yes, I do use cardboard. Scaling to 1" = 1', so 1:12. Thanks!

  10. #10
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    Default Re: Bolger Otter question

    Well, of course you don't NEED all those molds. At all. Unless you want to make the shape the designer drew. The alternative is to use a few molds and let the material run as it may. It's how I built my last three skiffs, as I was "designing" them, so let the material itself do the work.

    A self jigging style boat can still come out twisted and skewed, whereas a boat built on a trued up jig will have a VERY hard time being anything but true.

    Basically, the more molds, the more accurately one can reproduce the designed shape, and the sturdier said molds are held in relation to one another, the more straight and true the finished hull will be.

    When making models, by the by, I only ever glue seams with plain glue. I use a flattened toothpick shape so I can build little "fillets" spanning the joint. It works a treat.

    Have fun, but be careful. I have dozens of models laying about...

    Peace,
    Robert

  11. #11
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    Default Re: Bolger Otter question

    Yes, I guess you're right... Building the boat with the molds forces everything into shape until the glue is dry, and then the shape will be permanent even without the molds. Should have thought about this before. I guess I was confused as to why Zephyr does not seem to require the molds, but that's a whole different shape.
    Yes, I use Elmer's white glue for my cardboard models. I make the fillets by just running down the tip of the bottle along the joint and squeezing out the glue, shaping it with the nozzle. It becomes a nice edge-filling "quarter-circle".
    Yes, I have multiple models as well, but I must say I do enjoy making them, it gives me a great idea not only about the build but about the final boat, esp. with a model figure to see how big everything is in relation to a person. Fun and educating!

  12. #12
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    Default Re: Bolger Otter question

    Quote Originally Posted by Mattokun View Post
    Yes, I guess you're right... Building the boat with the molds forces everything into shape until the glue is dry, and then the shape will be permanent even without the molds. Should have thought about this before. I guess I was confused as to why Zephyr does not seem to require the molds, but that's a whole different shape.
    Yes, I use Elmer's white glue for my cardboard models. I make the fillets by just running down the tip of the bottle along the joint and squeezing out the glue, shaping it with the nozzle. It becomes a nice edge-filling "quarter-circle".
    Yes, I have multiple models as well, but I must say I do enjoy making them, it gives me a great idea not only about the build but about the final boat, esp. with a model figure to see how big everything is in relation to a person. Fun and educating!
    I do hope I didn't sound brusque.

    Of course, I'm only guessing as to the reasons Phil had. He was a singular thinker, to be sure. I enjoy as much simple and blunt approaches to problems as sophisticated and fine ones, which helps explain the sheet ply skiffs and the by eye, to fit, sof kayaks. I mean, I've built more than a few full sized boats, too, so I'm not TOTALLY guessing as to how they go together, but I am far from an expert whose advice should be heeded.

    I hesitated to recommend the direct nozzle technique, but you are clearly an experienced modeler. I keep a small, child sized glue bottle for model work. It makes it easier to fit into model sized nooks and crannies. It's horrible getting the right sized "blorp" out of the gallon sized bottle to get the refills directly down the neck, though.

    Plywood is funny stuff, because you can sometimes fudge it into "unnatural" (for sheet goods) shapes, but only when firmly braced. My knowledge of complex plywood shapes came from ramps and was applied to boats in an inside out fashion. A combination of shaped panels and stout bracing can induce shapes in ply it won't take if simply bent. The inside corners of wooden pools come to mind. This may be why certain models of "instant" style boats call for strongbacks and others don't.

    I'm currently modeling a few boats and a new camping trailer. For exactly the reasons you mention, to see how things fit and relate one to another. Would I were computer literate, and I'd simply render them in electron mirages, but I'm straight Homo Habilis, and must need draw on paper and render in solid form from chip, foam, or thin wood board...

    Carry on. And keep having fun.

    Peace,
    Robert

  13. #13
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    Default Re: Bolger Otter question

    Huh?! Brusque? How so? No, not at all!
    Yes, I wish I had only 1% of Bolger's imagination...
    Yes, for the glue I use those bottles of Elmer's that they sell for school supplies, works really great for me. Only thing is that Elmer's shrinks upon drying, so esp. when doing thicker lines of glue, that may be an issue.
    As I mentioned further above, I actually use cardboard. It's so much easier, no sawing and filing, just plain old scissors do the trick. Of course, sometimes I'm not sure how close this gets to reality, as compared to (thin) wood.
    Yes, that whole computer CAD stuff is completely lost on me, I'm not necessarily computer-illiterate (computers are my main tool at work and I do have to code as well), but CAD, CFD, all those things, I'm way too old-fashioned. I guess that goes back to my RC airplane modeling days in the good ol' 80's and '90's, "we" did not have any CAD etc. back then and all was done by hand. I did learn a lot!!

  14. #14
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    Default Re: Bolger Otter question

    but I'm straight Homo Habilis, and must need draw on paper and render in solid form
    Bolger said something along those lines , and saying that he had an " obsession with pen and paper " .

  15. #15

    Default Re: Bolger Otter question

    Straight Homo Habilis. I know exactly where you're coming from......

  16. #16
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    Default Re: Bolger Otter question

    Quote Originally Posted by beam reach View Post
    Bolger said something along those lines , and saying that he had an " obsession with pen and paper " .
    More limitation than obsession, in my case.

    Peace,
    The Computer, He Hate Me

  17. #17
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    Default Re: Bolger Otter question

    Quote Originally Posted by gizmojoe View Post
    Straight Homo Habilis. I know exactly where you're coming from......
    Me hit stick with sharp rock, stick now two stick!

    Hoot! Hoot!

    Peace,
    Me Also Know Where Fruit Tree Is...

  18. #18
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    Default Re: Bolger Otter question

    For what it's worth, I've built three Bolger boats and didn't try to get clever with the plans. The two that were plywood fit together like they were cut with a CNC machine. His plywood plans tend to be pretty clever in ways you don't see until you're in the middle of it. Trust him, he's the last designer to willingly waste your time or materials. My 2 cents.

  19. #19
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    Default Re: Bolger Otter question

    Quote Originally Posted by earling2 View Post
    ...Trust him, he's the last designer to willingly waste your time or materials...
    Yes, that's true.

  20. #20
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    Default Re: Bolger Otter question

    Funny, we trust the designer's boat with our life, but do not trust the plans enough to simply follow them.

  21. #21
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    Default Re: Bolger Otter question

    Quote Originally Posted by Oldad View Post
    Funny, we trust the designer's boat with our life, but do not trust the plans enough to simply follow them.
    Haha, you have a point there!

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