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Educate me please.

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  • Educate me please.

    Need some schooling here. I keep hearing about when folks glass in a bulkhead, (between stringers) keep a gap and create a fillet then lay up fiberglass to avoid “hard spots”. How does this gap stop from creating hard spots?wouldn’t fiberglass tabs create hard spots in itself? How does the fillet not create a hard spot? Does this only apply to plywood or any material? I’ve read different topics on this but I guess it just doesn’t make sense to me. I found a post that showed a 3/4” plywood bulkhead cut about 1” short on bottom and sides, then a piece of foam cut the same thickness as the ply on top and then maybe 1.5” on the bottom to go between the ply and the hull to create the fillet and roughly a 45 degree angle so the glass lays up nicely. How does this not create a hard spot? Thank you all in advance.
    BadMako.[br]

  • #2
    I've heard that as well, I tabbed reinforcements into my hull just for beginners practice.
    Peanut butter then tabbing, now I'm more curious!
    I'm waiting!
    BWP
    []Starcraft Bluewater 180, 1988[br]1996 Mercury 115 2+2 exlpto[br]Project Link: http://www.classicmako.com/forum/top...TOPIC_ID=46572

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    • #3
      I've heard this before as well. From what I understand the basic idea is that a long rigid core, such as a stringer, in contact with the hull cannot flex enough with the rest of the material/hull around it. Supposedly it can cause the glass to break. The stringers in my 241 didn't appear to be bedded in anything and were in contact a bit with the bottom of the hull, been that way for 30 years without failure. The new bulkheads I installed, which were PVC board so not exactly rigid, were pretty much butted right up to the hull/stringers and then glassed in heavily. My new Coosa Transom was done the same way, filled the gaps with high density filler of course. I've replaced transoms with pourable stuff before too, no way you're be able to add a buffer to that stuff. I'm not saying my hull was built right or what I did on my own hull was the best way to do it but I can offer a little bit of experience!
      1990 241 Mako Rebuild thread[br]http://www.classicmako.com/forum/topic.asp?TOPIC_ID=59709[br]Nicholas[br]Stuart, Florida

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      • #4
        Long ago Regulator had to repair a couple hundred of their hulls because they did not isolate the stringer from the hull. Modern technique is to lay a strip of some type of foam between the hull and stringer. I'm repeating this second hand so don't know the details. The warranty work on the Regulators was handled by a company in the Cape Coral Industrial park, across the street from Atlas Boat Works, if I remember correctly. Until my brother, who built custom wood boats told me about it, I had no idea stringers could not be hard to the hull.

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        • #5
          BadMako.[br]

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          • #6
            So in the pic above “I found on another site” shows what I’m talking about. I guess I’ll go about it this way to avoid hardspots. However, I’ve never done it this way and have never created hardspots that I know of anyway. Thanks guys for your responses.
            BadMako.[br]

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            • #7
              Hi Barry. Thanks for asking that question! Food for thought as I get ready to add bulkheads to my boat. Bill
              WILLIAM WEBER

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              • #8
                man I researched the hell out of this, with no conclusive outcome. I think the main thing to avoid is inconsistent contact, ie the stringer touches in some places but not others, and hard corners. If you've got the right balance of core vs laminate the glass is carrying the load either way. I can buy that a strip of foam might make sense between a relatively hard core, like plywood, with thinner glass but FWIW I think if you bed it thoroughly and tab it in with a generous fillet the stresses are spread enough that it won't be a problem.

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                • #9
                  Wolfie, I agree. After all the years of doing stringers and bulkheads as part of my career, “ been out of the game for a while” I’m starting to doubt my processes because of this. I never once had any issues with the stringers or bulkheads I’ve replaced but now, I’m wondering if I’ve been doing it wrong. The part I can’t get past, is the fiberglass tabbing, if the bulkhead causes a concentrated load, why wouldn’t the tabbing do the same thing? Is the concentrated load coming from the weight above the deck? Take for example a one piece stringer grid. It literally lays right against the hull and it’s either bonded or tabbed all the way around. How does that not cause a hard spot? I don’t know. Maybe I’m just over thinking it. Just gonna do it like I’ve always done and see how it goes. Thanks for the reply.
                  BadMako.[br]

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                  • #10
                    I'm curious, hoping more people smarter than I chime in!
                    I've used my skillset on 4 hulls now, and yes, it seems like tabbing would extend the load out, now I'm worried! Nah! Not really, calling all lamination engineers!
                    BWP
                    []Starcraft Bluewater 180, 1988[br]1996 Mercury 115 2+2 exlpto[br]Project Link: http://www.classicmako.com/forum/top...TOPIC_ID=46572

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                    • #11
                      My understanding is the stringers need to be able to flex and twist with the hull. You make them too solid and a weaker link will absorb that impact and crack. Like the frame in a car, yes it's the structure, but it also bends and twists with the vehicle. Keep in mind, when they built these boats and laid in the stringers and bulkheads, the plywood was just a form to give the stringers their shape. The plywood wasn't intended to be part of the structural support. like a transom core. Of course it is, to some degree, but wasn't the intent, just a cheap moisture resistant cedar to make a male mold.
                      [br]Michael R. Delgado[br]1972 Mako 22[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=15745[br]1976 Mako 25[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=18013&SearchTerms=mako,25[br]

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                      • #12
                        The good part about the old Mako's---the water under the wood stringer acts as a buffer like the foam in the pic. lol
                        Ryan[br]Parrish, FL[br]1977 17\' Mako Standard[br]2011 115 Opti[br]17\' Rebuild Thread: http://www.classicmako.com/forum/topic.asp?TOPIC_ID=18920[br]

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                        • #13
                          Originally posted by umachme View Post

                          The good part about the old Mako's---the water under the wood stringer acts as a buffer like the foam in the pic. lol
                          This got me good xD
                          Norwalk, CT
                          '79 19ft Mako - Project Thread

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