25' Double Eagle aluminum build (placing stringers)

Discussion in 'Metal Boat Building' started by Northeaster, Mar 10, 2014.

  1. Westfield 11
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    Westfield 11 Senior Member

    Not if they are Americans! More like 1.5..... Now that 27% of the general US population is obese, the FAA is revising their 170# standard weight for passengers. Even back in '06 the average American man was 195 lbs and the average woman 168 lbs, I doubt they are any lighter 7 years later.
     
  2. SukiSolo
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    SukiSolo Senior Member

    Interesting - I'm closer to the average American woman.... at 5'11" and I'm about 170lb. BTW - I'm fat! for many years the same height but 154lb! ;)
     
  3. Westfield 11
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    Westfield 11 Senior Member

    Me too: just like a cruising boat, the older I get the heavier I get.
     
  4. Northeaster
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    Northeaster Senior Member

    Thanks all for the advice! Not able to work on it this weekend.

    Kevin- The plans actually call for a 5/8" plywood deck, and the supports are on 8" centers, max. I had just planned on using one of the materials that I order in large sheets, ie what is used for hull bottom and/or sides.

    I did have a very experienced guy spend a few hours with me last weekend, and have lots to practice. He is a red-seal welder (and red seal machinist) with a min of 6 years welding alumium full time- spool gun and is a welding inspector.
    He started by laying down a few beautiful beads without changing my gun/welder settings much or at all - I had it at 23.5 V and wire speed to suit. One thing i noticed was that his tip to work distance was significantly shorter than mine. I think I had really went with too great a distance, after reading the necessity to do this.

    He did not have boat building experience. But, when i showed him the project and the plans for 1/8" hull material, or even upping it to 3/16", he said I would likely want to do most of this in short circuit transfer, instead of spray, partly due to heat, thin material and inexperience. He had me bring the volts down to about 18 (ws adjusted to suit) and we loaded the .035 wire in my other feederand gun, as I had always been practicing with .047/1.2mm. He mocked up a couple of 1/8" pieces, oriented as the hull bottom and side would meet at the chine, and then we practiced on those. He welded the inside first, mainly to get a good amount of material in there so the outside weld could be made to have lots of penetration, and not blow holes through. His welds looked great and he really thought that I should do most of my practicing, and most jobs on boat, with the .035 wire and short circuit transfer. Of course, he said spray transfer was great, on thicker materials.
    I hope to get up to the boat/shop and pratice in the next week or two.

    I am planning on working to align the shaft tube, strut, and keel/skeg in the next few weeks.
    I may put off the buying of the full size sheets until the fall, as:
    1. Spring sailbaot launch, putting docks in, mast raising are now juts around the corner
    2. Have large steel pipe materials on hand to build and install a mast crane / multi-purpose crane on my crib dock, before boat and dock launch
    3. Baby # 2 on way in September, and have to be realistic about how much time I will have to dedicate to boat project in the next few months. Spend all summer at cottage, 1.5 hour drive from boat shop, so hope to pick up steam in late fall.
    4. Have materials already for keel/skeg, so no cost to keep building these items.
     
  5. Kevin Morin
    Joined: May 2013
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    Kevin Morin Junior Member

    Building Double Eagle

    North,
    I'm glad you're changing to a metal deck and I don't think it will be regretted in the life of the boat.

    Good to hear you've had some one on one training and I agree for 1/8" or 0.125" or 3mm plate that 0.035" wire is a better choice and will be more controllable for a low hour welder.

    I personally don't care for the running gear design I've seen in Mr Witt's or Mr Hankonsen's designs. I find the plate keel idea old fashioned and weak compared to box keels and I've only built one plate keel and then repaired it for years. So the box method has been my 'go to' solution for all other inboard and shaft driven power boats. (about 11 over 30' ) I simply redesigned each boat (that was not my original design) to adapt the keel to the hollow box method and achieved more streamlined forms, less drag with no struts, higher overall stiffness and no cracking due to vibration.

    I've repaired more than two dozen 'cannery boats' with plate keels from Shore, Matsomoto, and others- all provided with plate keels and some strut arrangement. I found the struts to be a major pain in the stern-but I did make plenty repairing them for years..... so I gave them up in my designs for stressed forms and those are all still working fine.

    Also in a little skiff, I have to say I'm not willing to put in the running gear stern tube, pintle bearings and all without plating or skinning the hull first. That large group of welds will move the hull too much to trust the shaft to remain aligned in my experience. I simply won't do all the line up work before the hull is as stiff as I can make it.

    I put in shaft longs, rudder and pintle as well as the keel after as nearly the last part of the underwater hull, because I'd like the hull as rigid as I can get it prior to these additions.

    Cheers,
    Kevin Morin
    k.morin@kmmail.net
     
  6. Northeaster
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    Northeaster Senior Member

    Kevin - thanks one again. I must say that I have questioned the use of the flat 3/8" keel myself, but did not post about it, with so may other questions and priorities. I appreciate you bringing it up, and just in time.
    As the plans show the flat keel "sitting" 2 1/2" inside each frame, I had soon intended to drill large holes at approx 2 1/4\' and then cut out the lots for the keel plate.
    Although the keel plate would have been welded to the frames in the frames slots, on all 4 sides of the "cross" - I still had reservations about cutting away the frame slots at this point.
    Of course, this is an older plywood design, that was adapted (by the designer) for aluminum, likely a number of years ago. It was only 1 of 2 designs that I found that allowed for an inboard / shaft drive, which I preferred.
    Anyway, if I can make some changes now (with experienced advice...) I will gladly do so.

    You make some very good points about shaft alignment changing with welding heat, etc.
    I have seen pics of large box keels on sailboats, but am not that familiar with them on small boats.
    Can you give a rough estimate of the size or changes that you recommend. For example, can I just cut two pieces approx the size of the one piece in the plans, but then weld them both to the boat, say 3" or 4" off center (near the prop, tapering in to a point nearer the bow), and then plate in the bottom?
    As you mention you do them after the hull, I assume they are only welded to the hull sheet, and not cut / passing into the frame?

    If you have any pics of this, I would appreciate seeing them.

    Of course, if it is done after the hull, I don't require a final keel design now - it is enough that you have stopped me from cutting a single plate keel into the frames, and I guess now I should focus more on buying, cutting and installing hull sheet.
    The welder said he would definitely come back again, when I need help or start new large tasks, to make sure I am set up properly.
     
  7. Northeaster
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    Northeaster Senior Member

    Hi Folks - hoping to get some feedback after my attempt at correcting my improper running of longitudinal stringers, especially nearing the bow.
    For right or wrong, as I had numerous extra slots cut in my forward 4 frames, I decided to use 1 1/2" x 3/16"angle forward of midships and keep the flatbar in slots, aft of midships, as I believe it is Ok there.
    I beveled backsides of flatbar and angle and welded them back to back, overlapping about 18", which falls around midships, where there is little curvature.
    I cut 1 1/2" swaths for the angel to sit in and I am able to adjust the position of the stringers somewhat - but I am hoping the the experienced folks here will think that they look better than before..... Foward, they definitely don't sweep in nearly as much toward the stem / keel but rather ( I believe) follow more the lines of the chine and sheer.

    I have only done one side, so I am hoping for input, so here's a bunch of pics.
    I did not "correct" the wavy flatbar stringer nearest the keel/ stem yet!!!
    The chine flatbar is only temporary - just to see how the stringers look with the chine there as well.
     

    Attached Files:

  8. Ad Hoc
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    Ad Hoc Naval Architect

    Hmmmm….well, I’m afraid its 1 step forward and 2 steps back.

    There is still so much that is wrong….however, for an amateur build, it’s fine….it is what would be expected. But the longevity will be in doubt, owing to cracking. I won’t dwell on all but a few comments.

    The welds look cold and too much…the black soot reveals a multitude of sins too, ranging from possible poor stop/starts to a gas flow problem.

    You should not lap the FB over the angle. The length of overlap is also prone to corrosion if moisture gets inside. Then the fact the joint is only transferring shear.

    The metal that has been removed, owing to the numerous slots, has hard corners too, and appears roughly cut etc.

    This is the problem….you are by your own admission inexperienced, nowt wrong with that. But you have decided to make additional changes and decisions without seeking proper advice prior to the changes you have done.
     
  9. Northeaster
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    Northeaster Senior Member

    Hi Adhoc - I do really appreciate your candid input and I do see your points re: the potential for moisture in the overlapping sections and not to have rough edges where material has been removed. I thought that mositure would be allowed to escape from the overlapped areas of flatbar and angle, as they are only skip welded. I thought it was only an issue if it was fully welded, and the moisture could not escape.

    re: the large welds and soot you are seeing - that is all welding that I did months ago, and admittedly I was practicing and adding way to much weld than required, as i felt it was safe to do so in those areas - not saying it was best to do it that way, but that I was comfortable with it.

    re: not seeking advice prior - I did not run some of these ideas by folks here, but have incorporated some methods used in other Glen-L designs (using angle or tee in large slots / swaths rather than the flatbar in slots only.)

    Can you comment specifically on whether or not the stringers appear to be better located, as this was the initial critque and I want to see if I have address that (acklowledging that I have made other mods not considered acceptable by professional standards)?
     
  10. Ad Hoc
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    Ad Hoc Naval Architect

    Well, yes and no.

    You can answer the basic question yourself, in this new 'set-up'. The stringers if you place a small tack weld from the stringer to the frame web, will it hold the stringer in place? That being the same small tack weld on each of the frame locations. If it springs back and breaks the tack weld, there is your answer.

    This simply means that the curvature is too great and any attempt to hold the stringer to allow you to weld it, will introduce many features which are problematic, notably the excessive residual stress you have built into the structure, amongst many others.

    Also, it looks like up fwd the spacing between stringers varies too much. What is the max distance between stringers in the original layout?....make sure you do not exceed that.

    The most common mistake is trying to force/place so many stringers up fwd where there is more curvature. Just simply add 1/2 frames or intermediate frames, (transversely) to break the panel aspect ratio and terminate the stringer onto that 1/2 frame....with the correct terminate method too. It's a lot easier to weld and fabricate a 1/2 frame!
     
  11. Northeaster
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    Northeaster Senior Member

    Adhoc - I do recall your earlier posts re: the preference of adding additional half frames / pieces that fit in, after the hull sheet is in place, and this is something that I will consider doing.
    I don't have the plans on me now, but know that I have not exceeded the bottom stringer spacing, where it was specified, but this was only on frames 1 and 4 of 8 (counting from the transom). There is an obvious gap in the aft bottom, where engine girders/ beds will be placed later and double as stringers / bottom stiffeners.
    re: spacing of topsides stringers, no specific measurments were given, but rather instructions in aft sections to keep relativley even spacing between cockpit sole and sheer, and nearing the bow, keep relatively even spacing between chine and sheer, for example.
     
  12. Northeaster
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    Northeaster Senior Member

    Keel seam tacked together.
    Topside panel on ground next to boat is upside down, in case you wonder how it will fit....
     

    Attached Files:

    Last edited: Feb 17, 2015
  13. Northeaster
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    Northeaster Senior Member

    Finished tacking most of the first topside, and removing straps. Still have to tack the aft end, and try to take out bends a bit near butt weld.... Butt weld on 2nd topside has much less warpage as used 4 temporary supports lengthwise instead of 2 on this one..
     

    Attached Files:

  14. Ad Hoc
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    Ad Hoc Naval Architect

    Just curious..what is going on here:

    DSCN2086.jpg
     

  15. Northeaster
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    Northeaster Senior Member

    I figured someone would notice that!
    It's just the reflection of the sectional gargage/ shop door, which is up to let in the light.

    It looks fair and there are no framing members there and I did not put any excessive amouts of heat int that panel - it wasn't warm to the touch more than a few inches from the weld, when joined..
     
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