Aluminum "Shoal Sailer"

Discussion in 'Sailboats' started by KVA, Aug 15, 2020.

  1. Barry
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    Barry Senior Member

    The small angle that the side makes with respect to the bottom will make it unlikely that the inside weld bead and the outside weld bead will turn into a completely welded joint with no voids. I understand that Dolfman has suggested skip welding the inside and only weld the outside bead continuously. I would suggest that you NEED to weld both sides continuously and that both the inside and outside beads connect/mix to avoid corrosion but more importantly gain as much strength as you can obtain from a proper joint.

    Both KyleA and Tansl have offered an option of including a flat bar at the transition
    My comment to hull panels being joint on a flat bar is that the protrusion outside the hull in the areas where the flat bar protrusion is not parallel to the direction of travel, ie most of length of the
    wetted surface of the boat, will act somewhat as an increased drag factor

    Better to weld the outside bead, back cut the inside bead area to the sound outside bead and weld the inside bead. Continuously. The weld bead will not be weaker than the surrounding hull paneling. Ie the heat created during welding will reduce the strength to an untempered/ unhardened aluminum alloy in any case.

    [​IMG]
    A picture of a high speed commuter aluminum boat where the impact forces exceeded
    the yield strength of the aluminum and deformed. The weld was fine and according to the owner, the boat continued service for the rest of the season. Ie no weld failure
     
    Last edited: Aug 29, 2020
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  2. A II
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    A II no senior member → youtu.be/oNjQXmoxiQ8 → I wish

    Elaborating on Dolfiman's post #39 sketch, the penetration of the outside weld bead can be improved by chamfering the thick bottom panel before welding.

    weld.jpg
     
    Last edited: Aug 28, 2020
  3. TANSL
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    TANSL Senior Member

    Absurd.
    Things can be much simpler and a good professional knows that in simplicity lies excellence.
     

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  4. A II
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    A II no senior member → youtu.be/oNjQXmoxiQ8 → I wish

    Quite an absurd statement when you don't explain why you think the suggested elaboration is absurd.
     
  5. TANSL
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    TANSL Senior Member

    You seem to need an explanation, which indicates the depth of your knowledge.
    Here I end my conversation with you. It has been a pleasure.
     
  6. A II
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    So after my reply in post #49 you've expanded the text in your post #48 and also added a sketch to the originally only one word ‘‘Absurd’’ post, here quoted is your later expanded version of the post:
    Difficult to achieve a full penetration of the outside bottom weld bead in your sketch with the shown bevel, and besides that, constructively the joint shown in post #47 is stronger* when following Barry's post #46 suggestion to also continuously weld the inside bead.

    * the on both sides completely welded and fully penetrated joint with no voids in post #47 is wider due to overlap of the side panel with the thick bottom panel, and the joint there is also better supported by the thick bottom panel, which makes the joint constructively much stronger than the proposal you came up with.

    And you need two bevels where I in post #47 suggested only one bevel for the same job, you call your suggested doubling of these preparatory activities simplicity, now that's absurd, this too exposes your lack of knowledge and insight in the matter at hand.

    Also your proposal needs a far more accurate alignment for a good result, that's just another reason why it's far from the unjustly claimed simplicity.
     
    Last edited: Aug 31, 2020
  7. Dolfiman
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    Dolfiman Senior Member

    I share these two suggestions #46 and #47 , it is better. To pay attention to the thickness involved, not to thin in order to resist without deformation to the heat of both welds, 8mm sole bottom combined with 4 mm chine panel may be a minimum (?) in my opinion. Anyway recommended to do some samples of the joint and weld procedure, with various angles between the 2 panels due to the hull geometry, to valid the process.
     
  8. KVA
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    KVA Junior Member

    Yes good point! I was thinking about it, and remember now that around the lake there are some small old wooden scows on shore, used as decorations (and landmarks)... leads me to think that people who have faced this problem in the past probably used scows as the natural solution for shallow draft. The scows I have seen there are small, maybe 3-4m in length. Up until now I did not consider that hull type (or indeed was even aware that is what it is called..). I think it is worth investigating a scow hull, along with the two panel versions recommended previously.

    Regarding windage, for sure. In the Polish lakes mentioned at the outset, there is now a tendency towards very high freeboard because people like to mimic larger yachts commonly sailed on the Baltic sea (this is what I've observed and in some cases been told by local sailors). Each year the boats seem to get larger and larger, 8-9m or more and the small marinas can barely fit them (They were developed for ~5-7m domestic designs like this ANDRZEJ SKRZAT - SASANKA 620 http://www.skrzat-design.pl/00sasanka620-pl.html). With a bit of a blow on, the necessity of keeping the centerboard almost or all the way up to avoid mooring lines mixed with the high freeboard.windage leads to some major drifting and often/usually outright chaos (very entertaining to observe). Anyways, considering that high winds through narrow channels is the norm away from the open water, a lower windage will only help.
     
  9. KVA
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    KVA Junior Member

    Interesting.. is the gap around the chine/rib for bilge flow ? I feel like some connection to the top of the rib would only help stabilize it from twisting, and help locate both parts.
    As for all of the other ideas, there's nothing really wrong with any idea if you analyze it to death to get to the real bottom of things and an informed decision/conclusion is the result.
    As usual, there will be pros and cons for anything.. impatience or rudeness is not an indication of objectivity, let's keep it civil and HAVE FUN ! Isn't that the point ? :)
     
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  10. TANSL
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    TANSL Senior Member

    Yes, it is, I agree with you in that.
    See attached another solution. Depending on the structure and actual dimensions of the frame, vertical keel, bottom plates, etc ... the final solution may vary slightly. In general, it is a matter of not putting more weldings than necessary, avoiding interference between weldings as much as possible and achieving the least possible distortion of the assembly, making things as simple as possible.
     

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  11. KyleA.
    Joined: May 2018
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    KyleA. Junior Member

    Cool, yes minimize welding and distortion.. welding the interior is bound to be unpleasant.
    The overlapping idea that Dolfiman shared made me think about using the overlap as a sort of one-way leeway resistance mechanism.. where in one direction lateral resistance is significantly greater than the other.

    This is probably not the first time it's been thought of.. not claiming invention.

    Quick sketch below, please do not bother tearing apart the weldment design, it's not the point.. main thing is that I think this would give quite a bit of lateral resistance drifting to the right vs. left. More complicated for sure.. that curved section could be cut from a piece of pipe, and also only used near the maximum beam/COE so it remains roughly aligned with everything else trying to resist leeway.

    upload_2020-8-30_16-52-32.png
     
  12. KyleA.
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    KyleA. Junior Member

    Same idea, simpler (than above) extension of Dolfiman's design.
    This would also permit tab-slot interlocking assembly; something I am going to work hard on using as much as possible..
    upload_2020-8-30_16-58-37.png
     
  13. A II
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    A II no senior member → youtu.be/oNjQXmoxiQ8 → I wish

    Re the sketches in post #56 and #57, that would indeed kinda act as chine runners I think.

    See the thread: Chine runners???

    example from post #21

    [​IMG]

    Quote from the above post #56: ‘‘ . . . only used near the maximum beam . . . ’’

    Yes, in this example they're to long I believe, it's just posted here to show the existing idea, not the perfect working-out of it.
     
    Last edited: Aug 30, 2020
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  14. KyleA.
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    KyleA. Junior Member

    Had a chance to play with the modeling tool and create a scow configuration.
    Also created some visualization of the displacement.
    The orientation for the images below are set as 1° pitch, 15° roll, 5° yaw, disp. 2700kg

    Will have to read up on considerations for the bow geometry for these things; seems to be a lot of neat options.. from what I understand the idea with the scow is to try to treat each edge as if it was a vee when heeled?
    upload_2020-8-30_18-55-16.png upload_2020-8-30_18-55-53.png upload_2020-8-30_18-57-11.png upload_2020-8-30_18-58-20.png
    Cheers!
     

  15. A II
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    A II no senior member → youtu.be/oNjQXmoxiQ8 → I wish

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