Building of Aluminium Boat . Mounting of hull framing structure

Discussion in 'Boat Design' started by an2reir, Feb 27, 2019.

  1. an2reir
    Joined: Sep 2001
    Posts: 566
    Likes: 80, Points: 38, Legacy Rep: 110
    Location: Chichester West Sussex UK

    an2reir fifty boat designs


    Well DCockey thats very good to hear because combined with the other methods of validaton and together with the correct welding sequence that means hull may be buildable "building may be feasible." The hull lines forward are slightly curved
     

    Attached Files:

  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,708
    Likes: 267, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Alloy boats have been sheeted that are not exactly developable, but with relatively thick tempered plate, it better be minimal.
     
  3. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,708
    Likes: 267, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    The aft half of the OP's boat is obviously a warped plane, and with dead straight sections, not developable. There is a reason we don't see this style of thing in the glut of alloy boats on the market.
     
  4. Ad Hoc
    Joined: Oct 2008
    Posts: 6,113
    Likes: 357, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Would suggest it needs more curvature in the fwd sections, and/or there needs to be more curvature in the stem line - either way, I never make them perfectly straight on fwd parts of a hull.

    Thanks for that.

    Im familiar with Gaussian quadrature integration within FE and its use for shape functions of elements.
     
    Last edited: Mar 1, 2019
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,708
    Likes: 267, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Seems quite a gap, as you would expect, of course it is buildable, just not with straight sections
     
  6. an2reir
    Joined: Sep 2001
    Posts: 566
    Likes: 80, Points: 38, Legacy Rep: 110
    Location: Chichester West Sussex UK

    an2reir fifty boat designs

    Thank you all for your feedback that has been extremely helpful to me. This is about starting a new aluminium boat company, the builder does not yet have in place all the optimal anddbest steps succession and full technology for the assembly of various components. I am doing my best to support the builder by providing must read list and documentation of how to assemble the hull panels on a setup and how and where to weld namely at the exterior of the hull bottom and on a fixed setup that would hold the hull bottom shape when welds are cooling. Probably the best useful thing is I will research more in regards what are the best techniques to make and weld the aluminium hull shell so that is does fit the separately made bottom framing grid( assuming both of the two are not disorted in the building process)
     

    Attached Files:

  7. Ad Hoc
    Joined: Oct 2008
    Posts: 6,113
    Likes: 357, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Have you read the article in Professional Boatbuilder magazine issue 151, Oct/Nov 2014, called Order of Assembly?
    It covers all these aspects.
     
  8. an2reir
    Joined: Sep 2001
    Posts: 566
    Likes: 80, Points: 38, Legacy Rep: 110
    Location: Chichester West Sussex UK

    an2reir fifty boat designs

    Hi AdHoc thanks for feedback I did just that now, and as well sent it to the builder. The new aluminium boatyard is a startup in the East of Europe; he has got a very long tradition of boating and boat building in the area - the Delta of the Danube River flowing into the Black Sea , he has got the brand new good equipment. I am inclined to think in this particular case of a small boat that is 5.6 meters long when welding the hull bottom the steps should be in such way as to minimise the distorsion caused be heat and the cooling of the weld. I would not weld the center on the inside but I would weld on the outside of the hull and yes I would do like the article writes; start at the center and move outwards toward FWD and Rear with weld on segments of 50 mm and leave a space of 500 mmthen another 50 mm weld.
     
  9. DCockey
    Joined: Oct 2009
    Posts: 4,349
    Likes: 195, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Andrei - let me know if you'd like some assistance in obtaining an "exact" developable surface from the keel and chine curves. You can send me a message using the system here if you'd like.
     
  10. an2reir
    Joined: Sep 2001
    Posts: 566
    Likes: 80, Points: 38, Legacy Rep: 110
    Location: Chichester West Sussex UK

    an2reir fifty boat designs

    Hi DCockey thank you for your feedback , I will certainly note your contact. I do understand your thought that might as well include a souggestion that I beleive is very true and good: In order to be sure better as well make an exact developable surface from the keel and chine curves. I am doing that right now. For the moment I think I can manage to do it myself did find this new plugin that is available
    D.LOFT https://www.food4rhino.com/app/dloft
    As well , I did already message some of the McNeel Rhino people , I told them what I did and ask them to let me know what their opinion is regarding the surface I already did.
    I do keep your contact, as I do work on various larger boats of various sizes.
     
  11. Barry
    Joined: Mar 2002
    Posts: 1,126
    Likes: 70, Points: 48, Legacy Rep: 158

    Barry Senior Member

    It would have been helpful to know that your plan was to build a number of boats. I assumed that it was a single boat that you were part way through the build with and trying to make
    your existing frame and bottom hull shell conform.

    If your goal then is to be able to produce a shell into which your separately built framing will fit repeatably, then I would take a different approach

    Obviously confirm that the surfaces are developable.

    Your goal will be to produce a shell that will repeat itself every time and that the frame component built separately will fit.

    Have your plasma/waterjet cutter make a set of frames and stringers out of 3/16 inch steel ( some members can be 1/8 inches) and build the entire hull frame out of steel to make a steel plug. Cross brace the heck out of it so it will not move during the fabrication process. (keeping in mind that you will want the ability to get underneath the inverted plug to tighten some bolts. More later

    So you have a plug, including the sides frames, gunnel in steel inverted on the floor. Now basically sheet it. Drop on the two bottom hull pieces. On the jig at the transom to hull sheet joint you will have added in a couple of 1/4 inch plate gussets with a 5/16 inch holes in them. Position the plate, drill a hole up through the gusset through the plate and bolt the plate down in the exact position. (Don't forget that you have to weld these holes up later)

    You will not be able to realistically bend the plate up at the bow at this time. Through a few more gussets welded along the keel and chine, add a few more bolts to stabilize the plate before
    the start of the bend toward the bow. At a couple of spots near the bow, where you have added some gussets, pull the plate to the jig and bolt it down. SEE A below
    Add in the chines, tacking only at this point as you do not want welding distortion to pull the plates around on the jig. Then add the sides, transom. SEE B below

    As all tacks point have been small, ie just to hold everything together for assembly of the sheets, go back and retack with substantial tacks to ensure that you do not have one snap when
    welding the shell. Then weld up the hull plate from the outside. I will give you some references to books on this subject as this post is getting quite big already. Boring most I am sure.

    Pull the one side welded shell off the jig. Either pull it off vertically and roll just the shell. OR flip the jig and shell as a unit, if you have the equipment, then pull the jig out of the shell.
    Stabilize the shell. At this point you will have some distortion at the bow due to welding and will have to push the hull near the bow outward as I mentioned in an earlier post. PM me on this.

    Now there are two choices here. Weld the entire inside shell or insert the pre made hull framing pieces. As our process was to install stringers first to ensure the hull bottom was straight, we welded the entire shell then installed the stringers. Ensure that the welder cuts back every weld termination before starting a new bead to sound metal as well as cutting the inside
    joints before welding to sound metal. There is a post in the forum that I explained the process. Don't just weld the inside welds without back cutting as more than likely you will have voids.

    I would reconsider the way that you are building the interior frame assembly. Ie you have made solid frames but have the longitudinal stringers in pieces. I would have all the stringers
    as one piece and make the transverse frames accommodate the one piece stringers as the stringers will have the exact shape as the hull shell and your frames are not touching the skin.

    The shell will not be perfectly straight when you pull it. But you know that it came off the jig that the support assembly will fit into, you will have to just push the plate up to the assembly
    before welding.

    I have been in maybe 8 of the aluminum boat builders shops in the Pacific Northwest and have not seen a method where they build complete assemblies and try to mate them together.
    Normally, they take the shell plates and just match up the corresponding points on a jig not to much unlike what your guy did. Weld the shell inside and outside and then install
    stringers individually. If they were to do 2 boats in a row, there would be slight variations in overall dimensions. The fitting of the stringers, transverse frames takes time and it sounds like you want to mitigate this time component by precutting to weld tolerances and building the components apart from each other


    (A) small problem may present itself here and that was one of the reasons from an earlier post asking if the Rhino program accommodated thickness of materials. Say the deadrise is 20 degrees at the stern but as you approach the bow the angle turns into 60 degrees or much more. There is a chance that your hull plates change the exterior measurement slightly.
    Normally this does not happen if the cut sheet is creating a concave/inside joint but if you have a convex outside joint, changes in outside measurements will occur unless the plates
    have been chamfered, at various degrees from the transom to the bow)

    (B) I am not sure how you are cutting the pieces but many cutting machines have the feature of marking the plate accurately, similar to scribe lines which can be added to adjacent sheets
    to ensure precise placement when you are matching edges

    Some books and in no particular order, each brings something to the table

    1) Boat Building in Aluminum Pollard
    2) Aluminum Boat Building Earnest Sims
    3) Complete Guide to Metal Boats Roberts-Goodson
    4) Boat Building with Steel Klingel (with a short section by Colvin on aluminum)

    If you or your welder has not built a lot of boats, it would be worth the cost to purchase your local Build Specification book. In the US, that would be the ABYC Standards for Technical Information Reports for Small Craft. Canada has a similar set of requirements but when you read both, I am sure that Canada just made arrangements to use the ABYC standards.
    The ABYC book provides in depth details on electrical, fuel tanks, corrosion, and every element of boat construction for small craft. With supplements the physical thickness of the manual
    is about 2 1/2 inches. Lots of info. I suspect you will have to specify as it is a business that the boat meets whatever standards that is required in your area. I suspect that this will have to be done to ensure that you customers can purchase insurance.
     
  12. DCockey
    Joined: Oct 2009
    Posts: 4,349
    Likes: 195, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Rhino can model thickness. Start with a surface representing one side, and then use the command OffsetSrf to create the other side. It is also possible to start with a mid-surface and create the outside and inside surfaces. Chamfering of the edges can then be modeled. Both the inside and outside surfaces can be unrolled to determine the shape the flat plate needed.
     
    Barry likes this.
  13. an2reir
    Joined: Sep 2001
    Posts: 566
    Likes: 80, Points: 38, Legacy Rep: 110
    Location: Chichester West Sussex UK

    an2reir fifty boat designs

    Hi Barry and David

    thank you for your feedbak wich is very helpful as were the previous. Yes, I do confirm it is to be a series production. I will read very carefully your above and certainly implement. I was now trying my best to simulate the hull bottom panel bending via FEA. I think given the fact that the bending of the hull bottom panel is done in sequences of attachements and forces applied ; think with enough work on the loadcase and by setting correctly the attachment points and the forces at work and their drections I might get a little close to the real behavior of the component in Real Life .
     

    Attached Files:

    • FEA.jpg
      FEA.jpg
      File size:
      351.1 KB
      Views:
      53
    Last edited: Mar 1, 2019
  14. Barry
    Joined: Mar 2002
    Posts: 1,126
    Likes: 70, Points: 48, Legacy Rep: 158

    Barry Senior Member

    b2.png b1.png b3.png b1.png b2.png b3.png

    This was a 36 by 12 1/2 foot custom build. Steel frame, reinforced, and then the roll. We decided to roll the entire structure only because we were a little apprehensive trying to only roll the shell if we pulled it off the jig inverted. Not sure why some of the pictures were duplicated. You will see the bolts that hold the sheet to the frame. The bottom was 1/4 inch and was a bear to get it to conform.
     

    Attached Files:

    • b4.png
      b4.png
      File size:
      118.9 KB
      Views:
      75
    • b5.png
      b5.png
      File size:
      182.5 KB
      Views:
      74
    • b6.png
      b6.png
      File size:
      160.5 KB
      Views:
      89
    • b7.png
      b7.png
      File size:
      118.2 KB
      Views:
      80
    • b8.png
      b8.png
      File size:
      130.9 KB
      Views:
      80
    • b9.png
      b9.png
      File size:
      100.5 KB
      Views:
      82
    3dig likes this.

  15. an2reir
    Joined: Sep 2001
    Posts: 566
    Likes: 80, Points: 38, Legacy Rep: 110
    Location: Chichester West Sussex UK

    an2reir fifty boat designs

    Hi Barry thank you for the photos they are indeed very helpful most kind of you to share knowledge . I am studying the photos and your above assembly related post
     
Loading...
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.