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  1. #11

    Re: Core decisions on 43 DCMY

    You glued it on the wrong side

    I like using 1208 and do more layers it wets out much quicker conforms nicer and I just use more layers boat builder taught me that one.
    Dan
    End Of The Line II
    1967 34C

    EOTL II Rebuild Web Page

    ><(((º>´¯`•.¸¸.•´¯`•.¸¸><((((º>`•.¸¸.•´¯`•.¸><(( (( º>¸¸.•´¯`•.¸¸¸><(((º>

  2. #12

    Re: Core decisions on 43 DCMY

    Dan,

    What resin are you using with the 1208 and is that the layup you used on the back decks?

    Jim
    Jim


    SALTY
    1973 38' AFT CABIN

  3. #13

    Re: Core decisions on 43 DCMY

    When I do a big layup like the replacement of Magic Hats deck I did polyester. The core on that one I use two layers of 1/2" coosa with a layer of 1 1/2 oz mat in between with 3 layers of 1208 then a layer of 1 1/2 oz mat on top. Some spots you land up adding a little more to come up even with the edge because its never the same thickness. I just add more glass to the low spots and roll it out with your metal roller to feather it in. After it drys I sand it down with a 8" wheel fill low spots with some gorilla hair then roll two layers of gel coat sand that smooth then I painted the complete cockpit.
    Last edited by 34Hatt; 11-03-2016 at 07:49 AM.
    Dan
    End Of The Line II
    1967 34C

    EOTL II Rebuild Web Page

    ><(((º>´¯`•.¸¸.•´¯`•.¸¸><((((º>`•.¸¸.•´¯`•.¸><(( (( º>¸¸.•´¯`•.¸¸¸><(((º>

  4. #14

    Re: Core decisions on 43 DCMY

    It has a layer of Matt and a few 1708 on the outside in that pic. It's as smooth as glass too. I have to finish the edges, prime and paint.

    I used epoxy as I was repairing an area that was already repaired and did not hold. The better adhesion and the improved strength were factors in that decision too.

    Coosa was a great choice as its never going to rot again. It was reasonably easy to shape and bonds well.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  5. #15

    Re: Core decisions on 43 DCMY

    Quote Originally Posted by 34Hatt View Post
    When I do a big layup like the replacement of Magic Hats deck I did polyester. The core on that one I use two layers of 1/2" coosa with a layer of 1 1/2 oz mat in between with 3 layers of 1208 then a layer of 1 1/2 oz mat on top. Some spots you land up adding a little more to come up even with the edge because its never the same thickness. I just add more glass to the low spots and roll it out with your metal roller to feather it in. After it drys I sand it down with a 8" wheel fill low spots with some gorilla hair then roll two layers of gel coat sand that smooth then I painted the complete cockpit.

    Ok, thanks. Looking for a roadmap, as my back deck is in need of attention.

    Jim
    Jim


    SALTY
    1973 38' AFT CABIN

  6. #16

    Re: Core decisions on 43 DCMY

    Quote Originally Posted by Boatsb View Post
    Coosa is defiantly strong and rot resistant.

    I just replaced a transom on a cc that will have an Armstrong bracket and that's what I used.

    I also used epoxy and 1708 biax for strength.
    Scott...In an older post (http://www.samsmarine.com/forums/sho...-You-Use/page3) you advised against replacing a rotted balsa core in the fore deck with composite core material (Coosa or Divinycell). You recommended plywood. Yet, here in this post you have chosen to repair a transom with Coosa? Have you changed your mind about choosing plywood over Coosa? Or do you see these (deck vs transom) as two different repairs. In the post sited above, you estimated the compression strength for three 1/4" layers of plywood saturated in epoxy to be 7500psi. With the exception of some absurdly rare load or stress can you really imagine a reason why one would need such strength on a boat? That is 75,000# over 10 sq. in. (twice the weight of my boat!). I can not imagine a situation where that would come into play. Based upon information posted on this forum, Coosa has a compression strength of 1000psi. Would that not be sufficient to handle the compression loads of bolting down the windlass and cleats with backing plates? As that I am working from the underside of the deck to replace the core in the foredeck and under the bow pulpit, laying up three layers of 1/4 ply with glass and epoxy is considerably more time and effort than laying in a single layer of 3/4 Coosa. As you seem to have much experience in these sorts of repairs, I would appreciate hearing any additional thoughts or insights you may now have on the subject.

  7. #17

    Re: Core decisions on 43 DCMY

    3 thin layers are easier to get in and shape than a solid piece of coosa and the stress may not be carried by suck a large ares. A large washer may have 2 Sq inches of area.

    It's all about what works best for the job. The transom I'm doing is flat and coosa makes sense since there is a bracket bolted to it in 16 places.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  8. #18

    Re: Core decisions on 43 DCMY

    Have made some headway on the installation of new deck core. Decided to go with three layers of 1/4" marine plywood. Working from bottom (underside of deck). In hindsight, really stupid move. At first, I didn't think there would be so much rot based on sounding. However, once I got into it, I had to remove nearly all the balsa core forward of the bulkhead. Miserable awful job as I am sure many of you are aware. Initially, was hoping to avoid having to repaint the deck for a "small" repair. When all said and done, I may still be happy to have saved money not tearing out the top skin, but for now I hate it. Have installed the first layer of 1/4" plywood. Removed rot and cleaned up the bottom of the top skin fiberglass. Wetted the prepped fiberglass surface with epoxy. Then wetted fiberglass cloth and "glued" it to the wetted fiberglass top skin once both were tacky. Next, wetted out the first layer of 1/4" plywood and then let set up to tac, then coated with thickened (Cabosil) epoxy and "glued" the plywood layer to the tacky cloth. Plywood was pressed in and conformed to ceiling with 2x4s as braces along with bolts thru the bow pulpit holes in the deck.

    So...where I'm at now is deciding whether I should continue the plywood lamination with epoxy or polyester? I have read where others on this forum have used polyester for lamination with success, while others have stayed with epoxy. Reading Don Casey's book on boat fiberglassing, he recommends doing laminations with epoxy. Was wondering if anyone had any strong opinions on the subject or if it is just a case of "six, half-dozen of the other". If I use polyester, I was intending to put a layer of chopped mat between the plywood laminates for strength. I have read where polyester is not a good bonding agent without glass. With epoxy, I have some concerns about using chopped mat because I understand that the binders in mat can unfavorably impact the strength and chemical bond of epoxy. Thus if I go with epoxy, my plan is to bond the plywood layers together with thickened (cabosil or wood flour) epoxy. My primary concern with polyester is that once it sets it is hard, but brittle where as epoxy seems to be flexible. For a very thin laminate, I am concerned that polyester might crack and result in delamination later in time. Should this be a concern for a weight bearing load such as the fore deck? Would appreciate any input readers of the forum and contributors who are experienced in this area might have.

    (Sorry about the image...it is sideways and can't figure out how to turn it.)
    Attached Images

  9. #19

    Re: Core decisions on 43 DCMY

    Quote Originally Posted by Triskele View Post
    Have made some headway on the installation of new deck core. Decided to go with three layers of 1/4" marine plywood. Working from bottom (underside of deck). In hindsight, really stupid move. At first, I didn't think there would be so much rot based on sounding. However, once I got into it, I had to remove nearly all the balsa core forward of the bulkhead.....
    For those who will get into this repair in the future, remember the sounding hammer only shows you where the core is real bad. Instead use a moisture meter to find where water has penetrated and plan to remove just about all of the indicated area.

    Bobk

  10. #20

    Re: Core decisions on 43 DCMY

    I have no doubt you will be happy about the cash you saved doing this yourself. As far as bonding goes, I was under the impression that a layer of mat in between layers improved bonding. Good deal on the 1/4 inch. It's easy to bend into conformance.
    Regards
    Dan

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