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  1. #1
    Cadet
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    Default Transom core options - fiberglass

    Transom has rotted on fiberglass shell outboard boat. :'( Boat is an Ebbtide Dynatrak fish & ski w/ 150 HP outboard. I have removed the rear top cap and gutted transom wood to the outer fiberglass hull. I have heard that newer boats have a poly type transom core rather than wood.

    What are my options as to different types of material to use?

    Any suggestions would be appreciated - I would like to fix it right the first time. Thanks, Matt

  2. #2
    Fleet Admiral Mark42's Avatar
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    Default Re: Transom core options - fiberglass

    Sounds like you might be interested in Sea Cast. It's a good option if you want a solid polyester core. Check out this link: http://www.fiberglassics.com/mfg/transom.htm

    1985 Bayliner 1600 Capri Cuddy, 1965 MFG Niagara Custom. >> MFG Video<<. >> MFG Project<< >>Bayliner Hard Top Project<< >>Bayliner Repower Project<<


  3. #3
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    Default Re: Transom core options - fiberglass

    I have read about "Seacast" in archives. I have already gutted the inside to the outside glass shell and do not have a "mold" to pour into. I am looking more for a potential material that comes in sheets that may be better than wood?? - to epoxy back in, then glass over. If wood is my only option, from archives I have read, some seem to prefer treated plywood over marine grade? It seems treated is hard to find "fully dried"??

    Thanks

  4. #4
    Fleet Admiral Mark42's Avatar
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    Default Re: Transom core options - fiberglass

    Personally, I would use treated plywood. Just make sure it sits in a garage or shed until it dries well. If you can tack it to a wall with nails so it doesn't warp while drying out.

    One good technique to prevent water from seeping into the ply is to identify where the outboard mounting bolts will pass throught the plywood. Test fit the ply, then mark the bolt holes. Remove and 2" holes using a hole saw where the bolt marks are. Filll these holes with epoxy and install transom using epoxy. Then when you drill the bolt holes,they will pass through solid epoxy and not wood. If there is ever a leak around the mounting bolts, the water will not get to the wood.

    If you build the transom as describe above, it will probably outlive the rest of the boat.

    1985 Bayliner 1600 Capri Cuddy, 1965 MFG Niagara Custom. >> MFG Video<<. >> MFG Project<< >>Bayliner Hard Top Project<< >>Bayliner Repower Project<<


  5. #5
    Petty Officer 1st Class
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    Default Re: Transom core options - fiberglass

    I was looking into using a molded, 20 lb core polyurethane sheet as my transom. The company that makes this material doesn't recommend it however in a 1 to 1 swap - wood to foam. I went and bought a sheet of 3/4" marined A/B ply for my transom.

    TG

  6. #6
    Moderator Bondo's Avatar
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    Default Re: Transom core options - fiberglass

    Ayuh,.... I'll 2nd the P/T Plywood...............

    Ya don't say where you live,....
    But, if it's Heating Season where you are,....
    If you can find the right Spot,.....
    Sitting your Plywood where there's some Heat,+/ or Air Flow,...... It'll Dry real Fast......
    If Space is a Premium,... Pre-cut it,... It'll be Much Smaller then......

    Glued/ Epoxied,+ Screwed,.....It'll probably Outlast even You............d
    Any Grease is Better,..... Than No Grease at All.......

  7. #7
    Admiral
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    Default Re: Transom core options - fiberglass

    rcr - - Keep lookin. While plywood will work just fine there are alternatives. Unfortunately I don't remember the name of the stuff that was used on mine in a rebuild about five years ago. It came in 4X8' sheete and was 2" thick. It was made of a composition of chopped fiberglass/foam and was much lighter than you would expect. It was light green in color and more expensive than ply. I was told it is the material currently used in the transom of off shore unlimited racing boats.

    It was used on my 23' CC with twin 110s hanging on the back. I don't even think about rot.

  8. #8
    Fleet Admiral Mark42's Avatar
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    Default Re: Transom core options - fiberglass

    I knew a guy who was able to get reject blem Formica sheets for free. He glued them together to make a 2" thick slab that surved as his work bench. Was reportedly near indestructable.

    So how much does Formica go for now?
    1985 Bayliner 1600 Capri Cuddy, 1965 MFG Niagara Custom. >> MFG Video<<. >> MFG Project<< >>Bayliner Hard Top Project<< >>Bayliner Repower Project<<


  9. #9
    Lieutenant Commander
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    Default Re: Transom core options - fiberglass

    Quote Originally Posted by Solittle
    rcr - - Keep lookin. While plywood will work just fine there are alternatives. Unfortunately I don't remember the name of the stuff that was used on mine in a rebuild about five years ago. It came in 4X8' sheete and was 2" thick. It was made of a composition of chopped fiberglass/foam and was much lighter than you would expect. It was light green in color and more expensive than ply
    Was it Coosa board?

  10. #10
    Cadet
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    Default Re: Transom core options - fiberglass

    Thank you all for the input. Also kudos to the moderators, etc for this forum. 8)
    I found Coosa Composites on the internet, that sounds something like what I was looking for. I will write them to see on pricing & availability in my area. The formica is an interesting option, likely very heavy & may not drill too well?? Also screwing the ply to a wall - cool - I wondered how to fully dry ply w/o warping if I go that route.

    Happy New Year! Matt

  11. #11
    Admiral
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    Default Re: Transom core options - fiberglass

    Coosa Composites - That was the stuff they used on my boat.

  12. #12
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    Exclamation Re: Transom core options - fiberglass

    Hello Everyone;

    I am a representative of Seacast. Seacast is three times stronger and lighter than marine plywood, also it will NEVER rot so there is no need to EVER replace your transom again after using Seacast. It comes in 1/2, 1, 2, and 5 gallon buckets, also with a self leveling option. After you gut out the old wood simply mix, pour and let harden. Then just cap it off. It's that easy. We have a Seacast Calculator on our site to help you determine just how much you will need. Seacast will hold screws or nails with no problem. If you need to replace your transom I suggest checking out our website.

    edit emails not allowed.

  13. #13
    Captain
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    Default Re: Transom core options - fiberglass

    I'll 3rd the use of CCA pt ply. It will never rot (even if it gets wet), is easy to work with, resins stick to it and it can be air dried for complete success. I dried it in my garage with weights on top to keep warps away...and I turned it over a couple times to make sure it stayed flat. It was used for stringers, floors, transom and bunks. Using PT ply with epoxy resin was about 1/3 the cost of seacast and about 1/5 the cost of a high tech marine foam sheet using polyester resin.

    bp

  14. #14
    Petty Officer 1st Class
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    Default Re: Transom core options - fiberglass

    i don't know where you live but if you do a search on craigs list minneapolis you will find a place selling blank resin transoms for $50-60. the company supplied them to boat manufactureres and since boat sales are down they are trying to sell them. i wanted to use one but they were too thick for my use. i think the thinest they have is 1 1/2 in and they have 2 in thick also. if they ship it could be a cheap solution. they run their add about once a week under "boats"

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