Rebuilding Repco30 - need core advice

Discussion in 'Fiberglass and Composite Boat Building' started by tuna_fan, Aug 21, 2020.

  1. tuna_fan
    Joined: Jan 2015
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    Location: United States

    tuna_fan New Member

    I am starting a rebuild of a 1972 Repco30 lobster boat. As you can see from the photo, I am working with a blank slate more or less. Old boat had an inboard, I am converting to an outboard.

    I am open to NON wood alternatives (coosa, divinycell, plasticore, etc etc) and will use some in the rebuild. I am trying to balance cost vs performance in the cores I you all know, those cores can add up quick. Using GP polyester resin throughout the rebuilt.

    So, with that in mind, couple questions:

    Stringers - current ones look ok, I am going to seal the holes and reglass. I will cut out the bad sections midship foward and replace. As well as add 2 more. Thinking COOSA or WOOD here... coosa just so darn expensive. Thoughts? If wood, what kind - some kind of hardwood?

    Bulkheads - PLY or FOAM. Maybe a lower cost foam core (Carbon Core makes a reasonably priced PU) or marine ply.

    Gunwale - PLY, FOAM or HONEYCOMB - I am going to raise the gunwale, which makes me think a good foam (on edge) would get me the 6" or so raised wall, then create a "box" and glass the whole thing.

    Deck Support - GRID SYSTEM or PULTRUDED SUPPORTS - In the shallow areas of the hull, I will rest the deck on the bulkheads and stringers. On the deeper parts, I will either continue the stringer and bulkheads UP to meet the deck, OR use pultruded fiberglass square tubing to support cross members (also of pultruded fiberglass tubing).

    Deck - HONEYCOMB, COOSA or PLY - I like the idea of spending a little money on the honeycomb vs the ply...mainly to save weight.

    Transom - COOSA or similar. I need to reinforce transome to carry the outboard...plan is to make it 2" thick min, buy building up 1/2" coosa and glassing. 1/2" so I can follow the crown in the transome, bend / glue / laminate repeat.

    I am open to whatever advise you all want to throw my way - on material selection, build suggestions, and CORE SUPPLIERS that won't break the bank. I am in Massachusetts.


    Attached Files:

    Last edited: Aug 21, 2020
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    When you mention that you are starting with a clean slate, you certainly mean it, re an empty hull!

    Ref your stringers, do you really need to have a core in them?
    The strength will be from the 'top hat' section created by the fibreglass overlaminations.
    Maybe you could just add some extra laminations where required, assuming that the existing lams are in reasonable condition?
  3. tuna_fan
    Joined: Jan 2015
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    Location: United States

    tuna_fan New Member

    LOL yup - she's pressure washed and ready for mods!
    RE: Stringers - currently have been a little hacked up, with exposed wood and penetrations...I will try and clean them up, let them dry and relam them. BUT, since I am in here, and everything is exposed, Im thinking why not add a little stiffness NOW.
    Noted on the top hat - yes I agree that will of course help as well...but im no navel engineer
    thanks for feedback! keep it coming!
    Joined: Nov 2018
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    My Hand Layup Experience is Molding 22 Foot Zodiacs . West System Vinyl Ester , we had a 25 Foot Rotating Mold , Slung on AXLES Bow and Stern .
    These were Fiberglass Re Inforced Poured Resin Hulls , Very Strong , I would say Quite Similar to your 1972 REPCO 30 .
    The Core Material in the 22 ZODIAC is 1 Inch BALSA Wood .
    Since the Invention of RESIN VACUUM MOLDING , Resin Hull ( Pour Shops ) , are realizing stuff the early shops missed .
    First - Balsa Wood is very good at FLOATING , which may be why it was Chosen as a Hull Core , but it has Disadvantages when it's an INTERIOR
    Integral Piece in a SANDWICH CORE FIBERGLASS Hull.
    It tends to Soak Up Resin , lots .

    Both the Big Name Resins - WEST SYSTEM and SYSTEM 3 , start life in a Bucket , Thick ( Low Viscosity ) ' Viscous ' Liquid , which only starts to turn into
    a SOLID after a Chemical Reaction ( POLYMERIZATION ) Takes Place .
    Straight Wood Hull Material , is ( Usually a HARDWOOD ) , Only a Model Boat Builder would use BALSA , it has no Structural Strength , and is
    TOO POROUS , when combined ( as a Sandwich Core ) with Polyester ( Fiberglass ) Resin .

    At the ZODIAC SHOP , it wouldn't be at all UNCOMMON to use an entire 205 Litre ( 45 Gallon ) Drum , per boat hull .
    At $2700.00 each .

    It Doesn't Look Like this 30 needs much work , to me ...
  5. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Fred, I am a bit baffled as to what your point is?

    Tuna, it is more than 2 months now since you posted - are you making good progress?

    Can you post any more photos of your boat please?

  6. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Wow. How did this get missed by everyone?

    transom all depends on power plan

    typically 3/4" coosa laminated together with a lot of glass each side is good

    I'll wait to see if OP is still around to go further
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