Corner Chine Extrusion Aluminum??

Discussion in 'Metal Boat Building' started by G Anderson, Jan 18, 2015.

  1. yofish

    yofish Previous Member

    Thanks. My reason for asking is you offered this assembly as a possible solution to the OP's query:

    "Hello, I am going to build a 20' plane jane aluminum flat bottom boat and want to use 1/8" for the bottom and use .100" for the sides."

    The OP then goes on about opinions regarding using an extrusion for putting the sides to the bottom. I can't (or perhaps better said that I can) imagine what a mess your proposal would end up being made from said target materials, that's why I asked. Four welds around a rectangular bar bisecting (through) the chine? With .100" and .125" plating? You actually do this?

    Further, as far as achieving said requirement most of us small boat builders could not conceive of any other or more 'simple' and foolproof way to accomplish that other than to just weld the two bloody bits together!
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Yes, on far more Class approved boats than I can shake a stick at, to date. As well as some fast ferries and patrol boats too.

    You're a small boat builder, and I suspect not building to Class approved requirements. It is not just about a "simple" joining of 2 plates. There is a thing called quality control and longevity and warranty issues as well as the structural strength from the SOR to also address. Not to mention satisfying the surveyor too.

    Been doing this method, wherever appropriate, for decades. Never any issues. Not all yards like this (I have another solution in such cases), but most do.
     
  3. yofish

    yofish Previous Member

    Wow, you're quick.

    I HAVE to pin you down: again, tell me that you use this very assembly with said plate thickness, simple, OK? Yes or no, because I cannot imagine it in terms of utility and aesthetics in that application. Strength - maybe - but at unreasonable cost. Also, I have no idea what issue there can be with the 'quality control' of a properly joined edge-to-edge chine weld - two passes instead of four. I can see the value for impact but what Kevin says is quite true, a sacrificial angle is better, IMO, and will not (ugly) fold over.
     
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Well, it seems in your zeal to ignore the fact that others have no issues with this, you are not reading my replies correctly.

    Repeated below again for the hard of reading..

    I know, as your replies make that very clear. Yet you are choosing to dismiss this because you do not do it find easy or think its an overkill.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    I suppose it becomes a matter of whether mass market small boat builders are held to such stringent rules, and if they were, would the boats cost an arm and a leg to buy. And would it make any difference to how they stood up to the rigours of use.
     
  6. yofish

    yofish Previous Member

    I have no issue with the basic design at all other than putting a blade at the chine might look sexy but in the world I live in would be a horror as it would be for this chap, the OP, "bouncing off of rocks". In his case the chine bar could be .190" and after a time would look like lasagna after bouncing.

    My biggest issue is with you recommending that this fellow use it as a way to build his skiff because yes, in this case it is needless overkill, hardly simple and for a beginner (an admitted assumption) doing such (using stated materials) would more likely produce a pumpkin than what he's after, a handy river-fishing skiff.

    Please, I'd really like a picture of something that you have had built using such a nominal plating schedule employing this chine assembly, especially during construction.
     
  7. yofish

    yofish Previous Member

    Kevin has given you the best advice of all on this thread, period, this speaking as a guy that has like experiences to his. You will not go wrong following his advice and have an easier time of it.
     
  8. yofish

    yofish Previous Member

    The mass market aluminum boat builders are mostly in the 16-28 ft range. When you scrape the paint off or remove the deckboards one will see some of the most atrocious welding on the planet yet they more or less safely pack hundreds of thousands of people here and there year in and out. Take apart an Alumaweld boat, for example, and there is nothing that comes close to 'overkill' in terms of scantlings, plating, joint design etc. The idea of a self-bailing deck on most of these boats is unheard of or lots more $$. Plywood with pebble vinyl glued to it. I've removed deckboards on some of these that you could squeeze the water from and the AL frame that they landed on mostly gone. Aluminum is not a miracle material and needs lots of care, especially ventilation, in order to give long service.
     
  9. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Well, thats because perhaps you didn't appriacte the whole of the request from the OP. Noted below for ref:

    And that's what I gave him.

    You clearly don't like it, fine. But you didn't ask the question, he did.

    Why what would that prove...that it can be done and you are now suddenly going to change your mind and say geee whizzz..i'll do that too. I think not. Thus why ask....you have your own way of building small boats. Which are smaller than i work with and not to Class nor require the standards that I must adhere too as well, and it appears that you don't because that is not your bailiwick.

    Chlak and cheese
     
  10. yofish

    yofish Previous Member

    G Anderson, I've tried to find said extrusion myself with the same results. I don't think its a great idea for salt as several have said but it is clean and easy - that's why the Majors use it.

    I'll add an approach for you that is the simplest method by far; it relies on technique and process control more than design to achieve what you're after.

    Here are a series of pics of a test piece I did today using your target materials: .100" 5052 and .125" 5086. I didn't have anyone around to read the meters but I'm guessing the volts around 14-15 and a little more wire than you'd expect for that low of voltage. The wire is 3/64 5356, I didn't want to take the time to change out to .035 (probably .030 even better) but it gives the concept. Early in my career I made lots of skiffs with 1/8" sides using large wire, well, just because that's what I was taught.

    So here we have said weld. The low volts produces very little smut and a 'ropey' weld, this is done straight, no whipping or backstep or anything but straight ahead with a little more forward lean on the gun angle than you might read as 'proper'.

    The second pic shows the root penetration and subsequent pics shows a 1" wide slice beat over on itself then back again. The 100 thousandths 5052 material naturally shows all the bending as opposed to the thicker and stiffer 5086. It breaks at the HAZ (heat affected zone). This would be the case if it was welded both sides, the only difference would be that it would be a little higher up the side because of the fillet face. What I'm suggesting is that if you practice the technique to the point of comfort, have good fit up and good tacks that you could do your side to bottom connection in one pass. Aesthetics might dictate grinding the hickies (root penetration) out. One of the obvious benefits is that one pass causes less distortion than multiples. That's my issue with Hoc's offering: four welds along the chine on 100 thousandths material is crazy. Some people call this sort arc, but after debating this is or isn't too many times on other threads I will refrain.

    This was a quickie and with more tuning to lower the penetration it would appear better.
     

    Attached Files:

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  11. yofish

    yofish Previous Member

    What do I know about whatever constitutes a 'class' boat? So, I'm ears. Are you saying that a 'class' welded boat can't have an edge to edge chine connection to meet a standard? I would really be interested in as to why, if in the affirmative. Pardon my ignorance but exactly what is the 'class standard' that you work to?
     
  12. Ad Hoc
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    Ad Hoc Naval Architect

    Nope, not saying that.

    To meet Class requirements requires a yard to have a fully implements QA system. If you don't then the surveyor checks every little weld everywhere. Since an edge to edge on a main structural boundary requires a high quality weld. This is confirmed by NDT....dye-pen, or x-rays where possible. In additional to that a welded joint between frames, especially where the angle of joint exceeds 150 degrees it no longer constitutes a structural support.

    What this does is between the frames, as the hull plate is flexing under slamming loads it "works" on that welded joint. Why, because there is sufficient support for that welded joint. The solution is to have a stringer running very close to that welded joint for stiffness along the length of the hull/joint, or have a stringer bisecting that joint. Either way, it is still 4 welds that must be perform. Many yards prefer the bisecting because it ensures a full-pen weld from both sides and is easier to access than a stringer that is some 50mm form the joint; the outboard side gets tricky to access on the stringer side.

    Not building to Class, such trivial matters as structural strength and continuity of stiffness coupled with warranty issues and QA standards to be satisfied for weld integrity, are or little concern to such yards. To the point of....why bother, its a waste of time and effort.

    As previously noted, its chalk and cheese.
     
  13. FishStretcher
    Joined: Oct 2011
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    FishStretcher Junior Member

    A few notes:

    You can extrude many alloys of aluminum. Some of it with the mechanical properties of cheese, some much better. So if there is a concern about 6000 series, you can get something else. That said, the grain of an extrusion might not be oriented the way you want.

    For a 20 foot skiff alloy and grain direction this might not matter, especially if it is trailered, as has been noted.

    If you do anything with 5083 or 5086, then get the correct filler material to help retain the strength. After all, those alloys aren't free, so the correct wire is worth it. I don't believe it is 5356. 5183 comes to mind, but check.

    The older aluminum skiffs I have have some extrusions and rivets and sealants. They work great if you don't let water freeze in the lap joints!
     
  14. yofish

    yofish Previous Member

    Yes, of course you can extrude different alloys of AL, it's just that 6061-63 is the one most commonly encountered. Alaskan Copper & Brass offers a nice selection of angles, tees and bars in 5086 but one gasps at their cost. Anyone can have a die made up and for a minimum of XX lbs get an extrusion made, the cost of which is obscene unless somehow otherwise worth it.

    5356 is the alloy of choice to join 5052 and 5086, 6061 too although you will find old data (Miller) that says otherwise. I have a chart from Miller back in the day that puts 6061 only weldable with 4043. What do they know?

    From Lincoln:

    "5356 wire has become the most commonly used of all aluminum filler alloys because of its good strength and its good feed-ability when used as a MIG electrode wire. It is designed to weld 5xxx series structural alloys and 6xxx series extrusions, basically anything other than castings, because castings are high in silicon. Its one limitation is that 5356 is not suitable for service temperatures exceeding 150 degrees Fahrenheit (65 degrees Celsius). The formation of Al2Mg at elevated temperatures at the grain boundaries makes the alloys prone to stress corrosion."

    My experience with 6061 underwater is that if it is anodically protected and better yet painted it gives good service. If not, not. It will probably never happen that us little non-class, hell, even larger builders will not put 6061-63 underwater. NOBODY is going to NOT use a 6061 rec. bar of XX thickness on a keel shoe in the world I deal in, anyway. There really is not a reasonable alternative.
     

  15. FishStretcher
    Joined: Oct 2011
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    FishStretcher Junior Member

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