Aluminum boat rebuilding project - The Vonda Lynn

Discussion in 'Metal Boat Building' started by cthippo, Jun 22, 2020.

  1. KeithO
    Joined: Jul 2019
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    KeithO Senior Member

    Depending on the thickness, aircraft spruce may be able to send you a sheet of aluminum rolled up to save on shipping. Wing skins on aircraft go down to 0.016" and are tempered, not soft.

    My local supplier, Alro lists a 6061 T6 0.025" x 48" x 144" 17lb $393 + shipping and tax
     
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  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Aluminium is strong stuff - the ally roof on the cat in my avatar is 18 SWG (approx 1.5 mm) thick, with panel sizes of approx 1m x 0.5m, and I can happily walk on it - ok, it flexes a bit, but it is a very long way from breaking.
    What thickness plate are you looking for re the roof?

    Re that grating sole, is it going to be left 'as is'?
    If so, I presume that you will have easily removable sections so that you can fish out coins etc that will invariably get dropped into the bilge?
    Will you have any positive buoyancy compartments on this boat? If not, then it might be prudent to consider this option.
    And will you have a splash well on the transom for the outboard motor?
     
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  3. cthippo
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    cthippo Senior Member

    In order to do it in one piece I would need a piece that was 72"x84". My supplier can maybe get 72x120 in 5053 for $235 a sheet, but that is awfully expensive for one small piece, and I'm not sure about using 5xxx alloys in a marine environment.

    Good question. I am not well versed in sheet metal and so the closest I've been able to get is somewhere between soda can and road sign. I just don't have enough experience with the various gauges for them to mean much to me. I can get 1/8 PVC foam sheet plastic for $55 for a 4x8' sheet and that is what I plan to do the walls in

    The grating is held down by bolts into the subfloor and can easily be popped out to inspect things or recover dropped items. After seeing the mess under the original sole of this thing easy access has been a goal throughout the project. The gunwales will be plated over with flotation foam inside, and I'm considering an empty plastic bow tank as a buoyancy tank in the 4 feet of unusable space forward of the cabin. Foam is good, but air is better goes the thinking. I will probably also use 1" pink foam inside the cabin walls, but that is more about temperature insulation than flotation.

    The boat originally had a splash well and I kept it around, but I REALLY hope to not need it. Losing 2+ feet of deck space is painful if it becomes necessary. If it does go back in, I may try to keep it as narrow as possible so that I can put something useful like jump seats to the outboard of it. I guess that is one advantage of an I/O drive.
     
  4. KeithO
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    KeithO Senior Member

    5053, in fact most of the 5000 series aluminum is commonly referred to as marine grade aluminum. It is not tempered and contains magnesium which contributes towards it being weldable. As you know must hulls are welded. But your roof would be too thin to weld... No worries about its corrosion resistance. Find out what full sheet sizes are. If you order part of a sheet, you get charged for the full sheet + a cutting charge then they ship you just the piece you ask for and the remainder goes into the "misc" pile of material to be sold at a discount or as "drops". So just have them ship you the full sheet, cut what you need and keep the rest for another project...
     
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  5. cthippo
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    cthippo Senior Member

    Kind of a red letter day today!

    I would estimate the cabin frame is now 90-95% complete and the transom is in. I still need to add a couple of roof support pieces and figure out how to bend some aluminum brackets. On that front roof truss, which is probably the weakest structure on the whole vessel, I riveted it up, changed my mind on how I'm going to do it, and used the new design on the other side, leaving the first set of gussets in place. When I'm ready to skin it, I will drill out the rivets on the first set and then replace them over the skin for reinforcement. The interesting point was just how massively rigid the assembly was when gusseted on both sides. When the whole cabin gets reinforcing plates after skinning it is going to be wonderfully strong. I would estimate weight at less than 100 lbs, but it's hard to tell.

    With the transom in we should be able to leak test it next weekend. I should be able to get the skin and polycarbonate for the windows sometime this month be into serious testing by spring! The last significant structural bits are a transverse reinforcing member at the stern, and the seat bases. I found some nice suspension seats on Amazon that are not too expensive and look both comfortable and durable.

    20210128_170053.jpg 20210128_170108.jpg 20210128_170128.jpg 20210128_170146.jpg 20210128_170215.jpg
     
  6. cthippo
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    cthippo Senior Member

    More progress and another change. I have been struggling with figuring out how to mount and secure the front assembly for the roof since it does not share any planes with the material it connects to. I ended up solving this by moving the support back to the vertical post and mounting gussets to those. This allowed me to support it on both sides and make it super rigid. The original plan was to have an angular "shelf" at the front of the roof structure, but instead I think I will bevel piece that comes down to the top of the windshields.
     

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  7. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I am trying to think of encouraging words to say here re your endeavours, but I am failing miserably. :(
    Please be careful, and keep a close eye on all the weight that is going on board with this re-build.
    Have you done a fairly accurate weight estimate of all the extra weight that you will be adding to the Starcraft hull, including the aluminium structure, outfit, essential supplies and the weight of her crew?
     
  8. cthippo
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    cthippo Senior Member

    I am watching it. It's awkward, but I can pick up the whole frame by myself, so I'm still under 100 lbs, and I'm getting close to being finished with it. I think i will be within the rated weight with a small margin of reserve. Also, take into account the weight removed, the original floors, back to back seats, plywood and carpet on the gunwales, etc. I am actually starting from a negative number and while what I am replacing it with may be heavier in some cases than what was there before, the total added weight isn't as great. There is also one fewer motor as i am not using the 10 HP kicker and will eventually replace the 90HP with something lighter.
     
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  9. cthippo
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    cthippo Senior Member

    With the snow gone and feeling a bit like myself again, plus a fresh cash infusion, progress is again being made. I have been assembling the wall and ceiling panels and will hopefully get them put in this weekend. Right now they are just hanging loose, but you can get a good idea how it should look when finished. The window frames are taking an inordinate amount of time and frustration, but I only have three more of them to do I think.
    photo_2021-03-04_00-18-50.jpg photo_2021-03-04_00-19-06.jpg photo_2021-03-04_00-19-14.jpg
     
  10. cthippo
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    cthippo Senior Member

  11. cthippo
    Joined: Sep 2010
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    cthippo Senior Member

    And we have a cabin!

    The last week has been a mad push to build the cabin wall sub assemblies and yesterday they call came together in a massive storm of rivets and caulk and, well, it's beginning to look a lot like a boat! Today we had a freak hailstorm and I went out to take a look and aside from some condensation, I don't see any leaks. I'm sure some will turn up over time, but for now I'm calling it a success. Next steps are windshields, controls, and reinstall the motor and associated systems before it gets splashed for the first time.
     

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  12. bajansailor
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    bajansailor Marine Surveyor

    She is certainly coming along!
    I am still a bit dubious though, as to what your stability will be like when you launch the boat, load her up with all your outfit items, and then finally you and your crew climb on board.
    I am also a bit worried by how the wheelhouse is enclosed, with a door on the aft side - I realise that you need this in your climate, but I think that you should carry out some stability trials when you launch before you set off on any journeys.
    At the very least, I think that the boat should be able to cope with you and your crew both sitting on the gunwhale (where the deck meets the hull) and not adopt an excessive angle of heel (excessive will be if you rapidly start to panic). It should also be able to cope with both of you moving from side to side in a cross wind.
     
  13. cthippo
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    cthippo Senior Member

    Plan is to take it down to a local lake and find a spot with just enough water to float it for stability tests, including the "Everybody rush to one side to look at the cool thing" test. Also, the "can we get the damn motor to run after rebuilding" test and a few more. As for excessive heel angle, there is a reason I plan to be wearing not just a PFD, but also a wetsuit for this.
     
  14. cthippo
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    cthippo Senior Member

    Haven't been posting as much now that the major structural work is done. None the less, work is continuing and I am tantalizingly close to launch. The engine and controls are in, with just a couple things left to hook up tomorrow. I built and installed the dash and wired in most of the circuits. Seats also came in, but will get installed just before first launch just becausr I have to remove them to clean out the bilges and I want that to be done last. Some stuff like running lights that isn't essential for her first time will wait until next month. The door got built because the materials for it were taking up too much space, but it too will not get installed until after first launch. Shooting for first of the month and should make that without much trouble. 20210414_193615.jpg 20210414_193511.jpg
     

  15. bajansailor
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    bajansailor Marine Surveyor

    She is coming along well - but what is the weight of that impressive dashboard that you have built?
    It is relatively high up, and every little bit of weight adds up fast.

    It also appears that you are not going to have any positive buoyancy compartments anywhere, with the floor being the grating from bow to stern?
     
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