23 Steiger Craft rebuild

Discussion in 'Boatbuilding' started by merch, Jan 6, 2013.

  1. merch
    Joined: Jan 2013
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    merch Junior Member

    HI everyone,

    My name is Tom and I have been using this website as a resource for a few months now and I thought it was time to finally chime in and ask or some advice. I am currently rebuilding a 1988, 23’ Stieger Craft Block Island. When I bought the boat it was not intended as a project, but shame on me, some major issues slipped right past me. Boat is pictured below.

    [​IMG]

    [​IMG]

    1988 was one of (if not the) the first years that Steiger built the Block Island Deep Vee models. For its age the boat was in very nice condition. Appeared sound, clean and well kept. The owner had frozen the head on his Yamaha OX66 250 at the beginning of the season and decided to sell the boat. I got it without the motor for a reasonable price (for a boat that was otherwise good to go).

    What I ultimately found was that the boat had already had the deck out once, and as a result the last owner took some drastic, horrific and scary methods to get rid of rot in the stringers/bulkheads and did a shotty job of the sole replacement. The result was a boat with inadequate, hacked up stringers and bulkheads with endless rot problems in the original structure. I’ve now removed all of it and besides a ton of grinding, I’m left with planning how to put it all back in. Some pictures below of what I ran into:

    Below is one from after all the foam was removed from both sides looking back toward the tank. Its amazing to see how much of the stringers were just cut out and left to rot.
    [​IMG]

    Forward of the tank just behind the helm. The last owner put blue foam like you’d find around foundations under the sole. Without it the rotted deck probably would have collapsed by now.
    [​IMG]

    There’s a lot more which I have been chronicling on another website, but wasn’t sure if I could post a link to it here so I didn’t. Below is a picture of where I’m at now.

    Looking aft
    [​IMG]

    Looking forward
    [​IMG]

    I have some questions now for everyone here regarding how to put it all back together. I’ll start that in the next post.
     
  2. merch
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    merch Junior Member

    This boat was originally laid out with a sparse layout of ¾ plywood stringers an bulkheads arranged into a grid. There are no full length solid stringers and the fuel tank area looked really under framed. Steiger does something different now with a solid fiberglass grid, but I’ve decided to look at various ways I can do this.

    First of all, I don’t think I can bring myself to put wood back in the boat. I’m investigating using Baltek PXc 24 for the transom and bulkheads. I’d really appreciate input from anyone here who has used it for these applications before too. I can get it locally (as opposed to Coosa).

    Second, the 3/4 inch stringers just don’t sit well with me. I’d be much more comfortable with foam core, fiberglass types. Not being sure how to approach it I got Dave Gerrs book (Elements of Boat Strength). I’m sure many of you are aware of it. He nicely outlines a process for determining what is necessary based on the size and purpose of the boat. I liked the approach and put together an initial concept based on it. I’d love feedback from anyone here who has actually implemented this Gerr-type design in their boats. It does venture away from where Steiger has gone now, but I think it will actually provide a more robust result with more functional under floor access and ventilation.

    The first diagram I wanted to show was what Steiger originally had in the boat.
    [​IMG]

    You can see the plywood stringer/bulkhead configuration. The fuel tank is only 84 gallons and sat right against the hull. All the plywood came tight up to the bottom of the cockpit sole. A first look led me to believe this thing was really under-framed. I haven’t ruled out going back in with this config, but I’m definitely leaning away from it.

    So after looking at the problem, I ran through Dave Gerr’s process of calculating this and that. The image below is what I came up with.

    [​IMG]

    It has a combination of what he calls engine bed stringers (orange) and non-engine bed stringers (blue). The engine bed stringers are of course intended for inboard design, but the dimensioning of them can be applied to the outboard boat. The non-engine bed stringers are much smaller, but higher in quantity. The fiberglass layup required for the small stringers is far less than the engine bed variants as well. Both types use non-structural foam cores. In this configuration all the stringers can run from the transom forward without interruption. Thats much better than what I had

    In the cross-section views you can get a better idea of what Im doing at the three positions I highlighted.

    At the transom I plan to bring the first inboard stringer either side of the keel up to the height of the engine bed stringers for additional transom support. Also, I don’t plan on tying them flush into the first bulkhead forward of them, rather, angle them in like the knees .

    At the fuel tank area I was still stuck with the size of the tank preventing the installation of properly located bulkheads. As an alternative, Gerr suggests ring frames. The ring frame is a transverse member that is the same height and width as the engine bed stringers. Unfortunately, I cannot accommodate the height required so I made them the height of the non-engine bed stringers and tightened up the spacing between the two. I’m still thinking about how to handle this particular area though. Below is a close up of that cross-section.

    [​IMG]

    Additionally, I plan to raise the floor 1.5 inches at the sides and add an inch of camber to the whole thing. I would also push the scuppers outboard to the transom corners as opposed to the inboard configuration the boat has now. I’m thinking the tops of the bulkheads will support the sole and have the camber in them. In the area over the fuel tank I will add additional deck supports. I may decide I need them in-between each bulkhead for additional stiffness as well. All I know is that the old deck sole was pretty springy even though it was 3/4 ply.

    Anyway, it’s a start. Input and suggestions are more than welcome. I’m especially wondering if there are other methods to calculate the scantlings for building stringers and bulkheads that I should look into. Gerr’s implementation here looks to be a little overdone.
     
  3. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    Looks like you have thought this problem over very carefully. Sorry to hear it was a surprise to you but that happens. We never stop learning. Your stripping out looks like a fine job and I only can mention one thing. Do not be afraid to use wood for replacemat stringers, etc. Some woods, black locust, cypress, eastern and western red cedar are almost impervious to mosture and rot and the above are just a few that are prevelent in the US. Black locust in the best though the heaviest, hard to find and $$$.
    The ceders are the lightest and are sold most everywhere. Cypress is from the far south but used everywhere in flooring, roofing, etc. The most expensive cypress comes from sinker logs that have beem buried in mud for a 100 years. Gypress runs about $1.50 to $1.80 a board foor, the ceders just a little more and black locust can be priced from A to Z' Coating these woods with 3 coats of epoxy or fiberglassing them over and you can be sure the repacement woods will long outlast you. Just a thought for you to consider. Your doing a great job. Stan http://www.connectedlines.com/wood/wood13.htm
     
  4. merch
    Joined: Jan 2013
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    merch Junior Member

    Thanks Stan.

    Like I said, I haven't ruled out wood, but I'd love to do the job without it.

    My real question here is has anyone had experince using non-structural foam core to do the stringers in a boat, and if so have they followed any "rules" like Gerr or others?

    Is there any other reference I should consider when sizing the stringers, layup schedule, etc? I plan on doing it all with vynil ester or epoxy (mosst likely epoxy).

    Thnks again.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The problem with non-structural foams is they can't participate in load bearing, so the laminate has to be much thicker to compensate. You save money on foam but eat up these savings with additional fabric and goo. These types of foams are simply a form or mold, to lay the fabrics over. All the strength and stiffness comes from the laminate and once cured, the foam doesn't even need to be there.

    This is the reason wood is still used - it's cheap, easy to work and can participate in load bearing. Boats of this era have wooden structures that fail, simply because they short cutted the amount of resin and fabrics they applied, to the wood to save money. Since you're not as interested in production line costs, you can take special attention to getting these structures well covered and entombed in goo and fabrics, so this doesn't happen again.

    This is especially true with epoxy, as it actually seals the wood. The net result with epoxy and wood is, you'll save on resin and fabric, plus you'll be able to employ cheap wooden stringers. One look at the prices for Baltek panels and you'll see what I mean. The same is true of other, structural foams.
     
  6. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    A few things, neither related to your OP-sorry.

    First, with the hull gutted and weakened, make sure you don't lose the original shape of it before reassembly. http://www.boatdesign.net/forums/fi...ertram-carribian-stringers-transom-44587.html

    Second, aluminum fuel tanks have a life span of about 20 years if you're lucky. So, as far as your tank, that might be the first thing to deal with before even planning the structure you're going to put back in. If yours is bad, its replacement might be a different size.

    Third, this type thing has been covered a lot here so use the search functions and also scroll to the bottom of the pages for a list of 'similar threads'.

    Another thing to consider on the reassembly is to incorporate some pvc pipe under the deck for running wiring, cables etc. Make it oversize so as to be able to run extra lines in the future or replace old ones.
     
  7. merch
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    merch Junior Member

    I was concious of the hull twist before I started. The boat is on jack stands at each corner of the transom lifted off the bunks and the fwd section of the keel is supported by a single point. There is no warping on the bottom. It was never stored on a roller trailer either.

    And actually the fuel tank is what i was going in for in the begining. When I started digging, I found all the other stuff.

    Thanks for the input.
     
  8. merch
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    merch Junior Member

    Thanks PAR. A lot of folks have been trying to entice me back into the wood-core-build camp since I started this.

    From what you can tell, is the only disadvantage to all glass stringers the cost of the extra glass/resin? Is there any benefit/disadvantage to either method besides cost?
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    There's good and bad things to consider about all building methods. The goo factor is high on laminate dependent retorts, while wood has it's known issues too. Delamination is a common issue with cored laminates and this is often from the experience of the laminator. If you have good laminating skills, you may be better suited to this approach, of course if the costs don't kill you.
     
  10. merch
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    merch Junior Member

    Hi everyone. Been a while since I did anything meaningful on this build, but looks like I’ll have the time to start moving along again.

    Some decisions have been made on how I will move forward. Most importantly I will be closing the transom off and getting a bracket. Also, I will be going wood-less on the transom and stringer/bulkheads and I am 95% I will be going forward with vinylester.

    The bracket decision was pretty easy. I always kind of wanted it, but when I solicited my wife regarding the subject she nearly demanded it. The choice to go wood-less was a bit more difficult. The advice I’ve gotten from everyone regarding my options has been great, and although I’d say 75% of the folks recommend the plywood route, in the end I need to make the decision for myself.

    Vinylester vs. epoxy has been another tough decision for me. Although I love the idea of epoxy, ultimately moving forward with vinylester is likely just due to the local availability of the product. I can get epoxies locally, but at nearly twice the price of the vinylester. My initial calcs/estimates put the whole job in the 25-30 gallon range for resins (I’m sure it won’t be less anyway). The best source for price and quality have come from online sources, mostly in florida, but at ~$50 per 5gal bucket for shipping, I’m not sure the extra cost is worth it especially considering that “locally available” options are really convenient with a job like this.

    I have a lot of thoughts on how to move forward with the whole thing and I will be posting and soliciting advice as I go forward here, but the first tree in the forest is the transom coring and closure (decided to use a 1-1/2” sheet of Airex PXc due to local availability). I’ve dug around quite a bit online regarding this one and it seems as though my options are nearly limitless. So, instead of asking everything, I have a very specific question regarding the approach I’d like to post here to get started.

    Really what it boils down to is what’s the most practical approach for closing it up in both time and effort. Does it make the most sense to bond the new core in as the transom exists and fair in the old notch with glass and filler? Or, is it better to cut the majority of the transom out leaving a narrow frame to bond the new core in? (shown in the picture below with the red line indicating the possible cut)

    [​IMG][/URL]

    My thoughts are that cutting it out might alleviate some of the challenges associated with clamping the new core in thoroughly to assure a good bond to the old material. Also, if I cut the transom out and leave only a frame it seems like a much simpler process could be used to bond and clamp (aka temporarily screw) the new core to the remaining outer edge of the old transom. I’d also get to avoid filling in a fairing all those big holes that are already in the transom.

    The only disadvantage I can see to cutting it out is that it would require more glass and goo to build it back up. Conversely, it seems like laying up the new outer skin evenly like this might be more straightforward than patching in the notch and fairing it all in. Same goes if I decide to add a camber to the top of the transom. Building in a camber off the old stuff would result in a slightly taller new transom core which I can't imagine would be very pleasant to lay up.

    Looking for some experienced advice on this one I guess.

    Here’s the link to a nice example of what I’m talking about with regards to cutting it out first.

    http://www.greatgrady.com/forum/viewtopic.php?f=3&t=17817
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Don't cut out what you already have, you'll just have to make new or rebond it back in. Simply put, don't make any more work for yourself, it's a big enough project. You'll want a good bond to the existing structure (transom skin, tabbing, hull shell, etc.). Adding a cutout filler now would have some advantages, as you'll be able to get to the back side of it. Adding it afterward isn't much more difficult, so a coin flip maybe.

    Think about the process, making a cutout patch, bonding in the core, the materials and techniques, etc. and most of these decisions will become obvious. I might consider making a partial new skin on a work bench, where you can bag it or at least work on the flat. This patch can then get bonded in, so all you have to do is deal with the perimeter seams on the cut out. Other then this, it's just lots of laminate work, getting enough tabbing and laminate bulk to hold the bracket.
     
  12. merch
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    merch Junior Member

    Thanks PAR.

    Your advice makes sense and is consistent with others I've asked.

    I guess my biggest fear here is the bond between the new core and the old transom since this is where it went bad on the original transom. Any advice regarding the vinylester/airex bond? Never used either before. I'm much more familiar with epoxy for bonding dissimilar materials.
     
  13. merch
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    merch Junior Member

    Been getting some feedback regarding my last question about cutting the old transom out. The responses have been overwhelmingly “don’t do it”. I guess that answers my question.

    So, I will continue over-thinking this one to death starting with the transom layup.

    I will be purchasing my first batch of supplies this week so I’d like to “loosely” nail down the layup for the transom since it will happen first. I sketched up the plan in the pic below based on a few guiding philosophies:

    1.) Try to obtain close-to-even thickness on the outer and inner fiberglass skins
    2.) Get something close to the original thickness for the finish transom
    3.) The plan seems sane compared to the many other transom builds I’ve seen on various sites

    [​IMG]

    This plan meets most of my entrance criteria (with some wiggle room anyway). If I tried to even out the thickness between the inner and outer skins including the new material between the core and the outer skin, I would end up with an inner skin almost ½” thick which seems excessive at first glance. Most folks end up throwing 4 layers of 1708 on the inner skin and call it a day. I went with 5 plus some mat for the inner-most skin.

    Also, some guesses were made here especially with respect to the thickness of the putty bonding layer between the outer skin and the new core.

    Looking for some feedback if anyone cares to weigh in.

    Thanks,
    Tom
     
  14. gonzo
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    gonzo Senior Member

    Chris Craft made stringers with polyester laminate over cardboard tubes for many years. Eventually the cardboard would rot, but it was only used as a form.
     

  15. merch
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    merch Junior Member

    Thanks for the info gonzo. I have a plan to pour the stringers in using 4 or 8lb foam then laying the glass over them. The idea is the foam will conform to the hull rather than me having to use putty to fill all the voids.

    Ever seen anyone take this approach of pouring the stringers with foam in a form then laying glass over them after shaping them?
     
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