Hull/deck Joint Debate

Discussion in 'Fiberglass and Composite Boat Building' started by Southern Cross, Aug 12, 2013.

  1. Southern Cross
    Joined: Mar 2013
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    Location: So. CA

    Southern Cross Senior Member

    I've removed all the deck hardware on my Olson 30 including the alloy toe rail. In the process of sanding, grinding and filling existing holes with epoxy etc, then paint 2 part poly and a non skid, redrill new hardware holes and rebed. The usual.

    The plan is to race and cruise offshore and so I want a stiff and dry boat.

    For those that don't know the O 30, they have been crossing oceans regularly and in winning fashion. I believe one finished the single handed transpac in 11 days. Not bad for a 30 year old boat.

    The O30 class as one design racing is pretty much dead. 7 boats at the nationals. However, as a single handed offshore racer, there is renewed interest. Lately some pros have been snatching them up and investing in interesting mods. One of these is glassing over the hull/deck joint on the top and underneath. The other is stripping the boat of excess weight.

    Over the years the O30 has had issues with hull flexing, partly due to the extreme weight on the rails - up to seven crew at one time (rules changed). So, the debate amongst owners and reputable mod shops is ..... Does the toe rail add any structural integrity? Does it help keep the hull from flexing? Or will glassing over the joint provide enough stiffness (if done right)?

    I inspected my hull deck joint and it is solid. No leaks. No separation. The adhesive is almost impossible to remove. There were upward of 50 holes drilled for the fasteners and these were the second set drilled.

    The toe rails run the length of the boat. Mine are pretty dinged up. I never used them. New ones will cost $3k. I could anodize or powder coat but I would really prefer just to keep them off and glass in some g10 for a toe rail at the bow between stanchions. Also, the boat just looks so much better without them.

    Thoughts? Thanks in advance.
     

    Attached Files:

  2. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Im sure that the L shaped profile adds stiffness to the sheer clamp. Do you need it ?

    Dont know.

    How is the deck bonded to the hull ? Were the mechanical fasteners part of the sheer clamp structure ?

    When in doubt you should structurally glass both inside and outside of the sheer clamp.

    I like alloy toe rail. Very practicle....Beer cans, winch handles and Maglight flashlights dont roll off the deck, they offer many outboard sheet , mooring line combos, safety harness clip in points and they ruggedize the sheer clamp.
     
  3. TeddyDiver
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    TeddyDiver Gollywobbler

    Seriously?
     
  4. michael pierzga
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    michael pierzga Senior Member

    Sure...anything in sight when the going get tough
     
  5. Southern Cross
    Joined: Mar 2013
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    Southern Cross Senior Member

    Yes, the fasteners did hold the joint together. So many. So many holes. Cored deck.

    I am going to glass the joint top and bottom. Probably will add fasteners every so many inches. Thinking about glassing over the fasteners if I don't add the toe rail.

    By glassing I mean 1", 2", 4" and maybe larger tape with epoxy. I imagine this will keep the joint from separating.

    But will this alone reduce flexing and stiffen the boat or will the toe rail make a big difference?

    Or what about something fastened in below deck?
     
  6. michael pierzga
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    michael pierzga Senior Member

    structural eglass would be 45 45 biax fabric.

    outside is easy...inside, overhead glass and grinder work is a nightmare,

    ss fasteners burried under a laminate is poor design.
     
  7. Yobarnacle
    Joined: Nov 2011
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    Yobarnacle Senior Member holding true course

    I'm doing many modifications to my little boat.

    I'll do a blog with photos when I'm done, if ever.

    Rather than mechanical fasteners for fiberglass joins, I'm stiching parts together with Kevlar parachute cord. Then epoxy. Then glass and epoxy.

    Besides strong and tiny stich holes, a great advantage is undoing it all with a grinder when I change my plans.
    also No metal buried.
     
  8. Southern Cross
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    Southern Cross Senior Member

    Interesting. Different. Please post pictures when you can.
     
  9. Southern Cross
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    Southern Cross Senior Member

    Really? Why is glassing over stainless fasteners bad design?
     
  10. Petros
    Joined: Oct 2007
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    Petros Senior Member

    if the hull is known to be a flexy flyer anyway, I would think any metal added to the structure would assist in stiffness. Fiberglass has about half the stiffness to weight ratio as wood and aluminum, so adding metal into the structure would give a large benefit. It would be required however that the metal be fastened to the structure in such a way to both take and transmit loads to the composite hull uniformly and without stress concentrations, or else it will shorten the life of the hull as the fasteners work their way out of the hull material each time the hull flexes.

    It is a very complex calculation to determine the number of fasteners required to prevent premature failure if the stiffer material is actually going to be carrying some of the structural loads.
     
  11. Southern Cross
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    Southern Cross Senior Member

    Here is a sketch of the joint ...
     

    Attached Files:

  12. tunnels

    tunnels Previous Member

    Why you worried about the boat flexing???

    Don't know why you worried about the boat flexing !! flex and twist is the next new thing and there lots of research going on how to make boats flex more and move and become more sea worthy and smoother riding !!!
    just grind out the join and back fill with glass across the join and use epoxy resin will all take a lot of time but what's time for anyway !!!!!:p:D:p
     
  13. Southern Cross
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    Southern Cross Senior Member

    I spelled "adhesive" wrong!
     
  14. Southern Cross
    Joined: Mar 2013
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    Southern Cross Senior Member

    Any creative ideas about glassing underneath where that void is under the hull lip?
     

  15. tunnels

    tunnels Previous Member

    Remember glass does not like to go over sharp corners so the surface needs to be well rounded ground if need be and sanded so you get a really good bond !! foe what it is this is a perfect case to use a good grade of epoxy and a triaxle glass cloth so all the strands run across the join! Triaxle is 45/45/0/ so cut into strips the right width and length remember the less joins the better and stagger the joins !! 50mm is the recommended over lap of any glass layers !! working upside down will be a challenge but cut to length first, pre wet out , then wet the surface its going onto and then attach the wet layer starting at one end and gently but firmly roll on with a narrow paint roller that you use for wetting with . After the two layers have been applied then use a hard roller and again gently but firmly roll smooth and neat , any excess resin can be mopped up with the squeezed out paint roller !! I would also recommend using peel ply over the top as its easier to roll out and get any air bubbles out of the glass , the peel ply gets peeled off when the resin has hardened and you get a smooth clean surface to lightly sand and paint over !! The same glass should be used outside and laid over the join ,same resin ,same glass ,same method !! Keep the whole excise simple straight forward and easy :D!!
     
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