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Thread: Ply or Coosa?

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    Ply or Coosa?

    The lower portion of my 27 sport's transom has rot. It was quite evident when I could scoop out pieces of wood with just my finger alone through the drain plug hole. Should there have been a protective sleeve? seems it would've been a prudent thing to do - nor - did I see any evidence that they protected the area with a resin. I'm leaning towards replacement of the transom with Marine ply with particular care in those before troubled area's, but even though Coosa is 3x's the cost it might be worth it in more ways than money. Any thoughts???
    1983 Cigarette 35' Mistress
    1976 Magnum 27' Sport
    1986 Donzi 18' Classic
    NEVER FORGET 9/11

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    Hey Scippy
    I had an hour conversation this week with one of the most respected boat builders ever about this exact thing in my 27 and he emphatically said marine grade plywood. That may create a stir from a few diehards here of "modern" materials but he uses some of the most high tech stuff out there and still does his trabsoms in wood He had lots of good reasons and he really does know what he'stalking about I'm redoing my whole transom and using wood
    Parnell
    Time forSweet Cheekz to find a new home

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    P, I've heard that before to a certain extent, but even better still when a experienced builder has many newer materials before him & still prefers marine ply for the transom. Coosa board does seem to be more forgiving then plywood especially if it were in the area of my drain hole plug.......lol - My total transom thickness is 2" (3/8" FG shell followed by 1-1/2" plywood followed by 1/8" FG...........the outter layup is amazingly thick, no wonder these boats are so heavy!
    1983 Cigarette 35' Mistress
    1976 Magnum 27' Sport
    1986 Donzi 18' Classic
    NEVER FORGET 9/11

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    My stringers and transom were done by a buddy who was the head glass guy at Hustler, plywood has superior adhesion to glass over the foams. He did go on to say that the real strength is in the laminate. When he did my transom he eliminated the KEY cause of rot, this was done by squaring off the bottom of the plywood then building up the plug area with solid glass. He said there was structural no reason what so ever to fill in the V area with wood, that all it did was make it liable to fail again, he also isolated the stringer wood from the transom wood. Reason being the moisture wicks from the transom into the stringers then slowly creeps forward, while you are at it check the stringers more than likely they are wet. Mine were wet up to just past the engine mounts, he cut them out about an other five feet until he got dry dust when cutting. Then installed doubled stringers, added bulkheads and transverses added maybe 100lbs of structural soundness to my 22.
    No matter what your beliefs are "GOD BLESS AMERICA"

    Semi retired marine tech over 50 years in the biz.

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    There may not be a reason to replace the entire transom.
    Why don't you start by moving upwards from the drain area and see if it gets solid?
    If the rot can be localized and removed, why replace the whole thing?
    When you start cutting replacement pieces, use a penetrating epoxy, like System Three Clear Coat, on all the exposed end grain and it'll never rot again.
    BTW, MOP's solution is very good.
    George Carter
    Central Florida
    gcarter763@aol.com
    http://kineticocentralfl.com/


    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

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    MOP's story is almost exactly what I heard from my guy escpecially the stringers and transom suggestion
    I like Georges idea too from a money, time and work standpoint if it can work My transom is so swisscheesed that there is no where left to drill any new holes. I have to replace the whole thing Scippy, do check it might be a nice suprise
    Parnell
    Time forSweet Cheekz to find a new home

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    Quote Originally Posted by scippy View Post
    P, I've heard that before to a certain extent, but even better still when a experienced builder has many newer materials before him & still prefers marine ply for the transom. Coosa board does seem to be more forgiving then plywood especially if it were in the area of my drain hole plug.......lol - My total transom thickness is 2" (3/8" FG shell followed by 1-1/2" plywood followed by 1/8" FG...........the outter layup is amazingly thick, no wonder these boats are so heavy!
    I just reread this. My guy said use two sheets 3/4" marine plywood with layers of glass on all three sides which jives with the thickness now Magnum did a really nice job of building boats back then. Just an observation that hopefully doesn't piss anyone off but they made their boats much more stout than Donzi at the time Course they were bigger also, just sayin
    Parnell
    Time forSweet Cheekz to find a new home

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    Quote Originally Posted by gcarter View Post
    There may not be a reason to replace the entire transom.
    Why don't you start by moving upwards from the drain area and see if it gets solid?
    If the rot can be localized and removed, why replace the whole thing?
    When you start cutting replacement pieces, use a penetrating epoxy, like System Three Clear Coat, on all the exposed end grain and it'll never rot again.
    BTW, MOP's solution is very good.
    I agree..

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    Quote Originally Posted by MOP View Post
    My stringers and transom were done by a buddy who was the head glass guy at Hustler, plywood has superior adhesion to glass over the foams. He did go on to say that the real strength is in the laminate. When he did my transom he eliminated the KEY cause of rot, this was done by squaring off the bottom of the plywood then building up the plug area with solid glass. He said there was structural no reason what so ever to fill in the V area with wood, that all it did was make it liable to fail again.
    MOP, Eliminating wood in this "KEY" area makes soooooooooo much sense now.............thanks for helping me not repeat a mistake!

    George, I also like your idea to just replace what's rotten in the lower transom by moving upward & away from the drain, but I have 2
    TRS cutouts and would likely replace with bravo's.........something I forgot didn't mention.
    Also, regarding the layup to the drain plug area.........should I use alternating schedules of CSM & WR until thickness is achieved?

    P, With the elimination of those "Gussets -or- tank stringers" I now can order tanks with a capacity of 70+ gallons each..........nice
    gain's with not too much fuss.


    Jamie, How's that TR running?
    1983 Cigarette 35' Mistress
    1976 Magnum 27' Sport
    1986 Donzi 18' Classic
    NEVER FORGET 9/11

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    [quote=scippy;573151]
    Also, regarding the layup to the drain plug area.........should I use alternating schedules of CSM & WR until thickness is achieved?[quote]

    You probably don't need to add more than 1/2" of 'glass.
    Using only 1708 Knytex alternating the orientation between +/- 45* and 0*/90*, it wouldn't take very many courses to get there.
    While you're at it, cut out the plywood in the area of the TRS cutouts. I think you could use a circular saw w/the blade very carefully positioned. Then it's easy to fill in the 'glass in the cutout area.
    Do you guys know about cutting a plug of glass (like in the area of the drive cutout) and burning it?
    If you do, when it burns out and cools, you can carefully take apart the various courses of glass and determine the original layup.
    Good luck.
    George Carter
    Central Florida
    gcarter763@aol.com
    http://kineticocentralfl.com/


    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

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    [quote=gcarter;573154][quote=scippy;573151]
    Also, regarding the layup to the drain plug area.........should I use alternating schedules of CSM & WR until thickness is achieved?

    You probably don't need to add more than 1/2" of 'glass.
    Using only 1708 Knytex alternating the orientation between +/- 45* and 0*/90*, it wouldn't take very many courses to get there.
    While you're at it, cut out the plywood in the area of the TRS cutouts. I think you could use a circular saw w/the blade very carefully positioned. Then it's easy to fill in the 'glass in the cutout area.
    Do you guys know about cutting a plug of glass (like in the area of the drive cutout) and burning it?
    If you do, when it burns out and cools, you can carefully take apart the various courses of glass and determine the original layup.
    Good luck.
    George, In regards to filling in the TRS cutouts..........I think I understand, but not completely sure. Are you saying? "make a perimeter cut (from the inside) to the TRS cutouts & fill in this area w/fiberglass as you would have with wood? if that's the case, would a smaller bravo cutout within this patched hole be strong enough and not crack in the future?
    1983 Cigarette 35' Mistress
    1976 Magnum 27' Sport
    1986 Donzi 18' Classic
    NEVER FORGET 9/11

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    [quote=scippy;573166][quote=gcarter;573154]
    Quote Originally Posted by scippy View Post
    Also, regarding the layup to the drain plug area.........should I use alternating schedules of CSM & WR until thickness is achieved?

    George, In regards to filling in the TRS cutouts..........I think I understand, but not completely sure. Are you saying? "make a perimeter cut (from the inside) to the TRS cutouts & fill in this area w/fiberglass as you would have with wood? if that's the case, would a smaller bravo cutout within this patched hole be strong enough and not crack in the future?
    Sorry I wasn't clearer. I meant cut away the wood around the TRS cutouts, and cut one large hole in the glass per drive. Actually, I think all you would have to do is remove the glass between the larger lower hole and the upper tiller slot. Grind and taper the perimeter of the drive hole to a ratio of 12:1 on the inside of the transom. Buy some melamine paneling from your favorite big box store, cut a piece slightly larger than the drive cutout including the ground tapered area, and screw the smooth side of the paneling to the outside of the transom. Use some #6 machine screws, or a similar size for through bolting the panel on. Use lots of screws, maybe 2" apart as you don't want anything to move. The resin will not stick to the paneling, and the paneling gives a very smooth surface to your patch.
    This is where burning a sample becomes important. After you determine the original layup schedule from your burnt sample, starting w/a couple of layers of mat, make some patch pieces of glass that are slightly larger than the opening. Then each succeeding piece is to be slightly larger until the inside piece is the same size as the outside perimeter of the ground area.
    After all these pieces are cut, you're almost ready to start. This method works so well you can even use matched, tinted gel for your first course. At least use a couple of coats of resin, if not gel. As soon as it starts to kick, start w/the mat. what ever you do, don't stop until you're finished. This whole layup process shouldn't take more than 5 minutes from start when the gel/resin kicks.
    After the patch is cured (it'll get hot too since all the courses go on at once), carefully grind the inside so that the inside of the transom is level and smooth.
    After this, you can patch the wood w/the new ply,
    Coosa, or whatever.
    Hope this helps to clarify.
    George Carter
    Central Florida
    gcarter763@aol.com
    http://kineticocentralfl.com/


    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

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    [quote=gcarter;573169][quote=scippy;573166]
    Quote Originally Posted by gcarter View Post

    Sorry I wasn't clearer. I meant cut away the wood around the TRS cutouts, and cut one large hole in the glass per drive. Actually, I think all you would have to do is remove the glass between the larger lower hole and the upper tiller slot. Grind and taper the perimeter of the drive hole to a ratio of 12:1 on the inside of the transom. Buy some melamine paneling from your favorite big box store, cut a piece slightly larger than the drive cutout including the ground tapered area, and screw the smooth side of the paneling to the outside of the transom. Use some #6 machine screws, or a similar size for through bolting the panel on. Use lots of screws, maybe 2" apart as you don't want anything to move. The resin will not stick to the paneling, and the paneling gives a very smooth surface to your patch.
    This is where burning a sample becomes important. After you determine the original layup schedule from your burnt sample, starting w/a couple of layers of mat, make some patch pieces of glass that are slightly larger than the opening. Then each succeeding piece is to be slightly larger until the inside piece is the same size as the outside perimeter of the ground area.
    After all these pieces are cut, you're almost ready to start. This method works so well you can even use matched, tinted gel for your first course. At least use a couple of coats of resin, if not gel. As soon as it starts to kick, start w/the mat. what ever you do, don't stop until you're finished. This whole layup process shouldn't take more than 5 minutes from start when the gel/resin kicks.
    After the patch is cured (it'll get hot too since all the courses go on at once), carefully grind the inside so that the inside of the transom is level and smooth.
    After this, you can patch the wood w/the new ply,
    Coosa, or whatever.
    Hope this helps to clarify.
    George, Thanks for taking me through it step by step, it's very clear now. Tomorrow or Monday I'll determine just how high the rot extends upward in the transom, hopefully I dodged a bullet.
    Now to this other matter of burning a sample piece of (transom hull) fiberglass to determine the actual layup schedule?............I'm "almost" there on the visual end, but need a little help. Could
    you take me through it one time..................................Thanks
    1983 Cigarette 35' Mistress
    1976 Magnum 27' Sport
    1986 Donzi 18' Classic
    NEVER FORGET 9/11

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    [quote=scippy;573175][quote=gcarter;573169]
    Quote Originally Posted by scippy View Post

    George, Thanks for taking me through it step by step, it's very clear now. Tomorrow or Monday I'll determine just how high the rot extends upward in the transom, hopefully I dodged a bullet.
    Now to this other matter of burning a sample piece of (transom hull) fiberglass to determine the actual layup schedule?............I'm "almost" there on the visual end, but need a little help. Could
    you take me through it one time..................................Thanks
    It's impossible to determine an existing layup schedule by looking at a piece of glass, so you have to do something to make it discernable.
    Glass won't burn, but the resin will, so take a scrap (you need several square inches) of the existing glass and burn it. The resin will be consumed, leaving the glass layup schedule in plain view. It will smoke and stink.
    Carefully take apart the layered glass w/tweezers or other useful tool. You'll be able to see mat, bidirectional stitchmat, roving, and cloth.
    Write down what you find, something similar to your findings will be your new schedule.
    George Carter
    Central Florida
    gcarter763@aol.com
    http://kineticocentralfl.com/


    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

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    Quote Originally Posted by scippy View Post
    Jamie, How's that TR running?
    It's not this year. I have been slowly taking it apart & freshening many things.. Hopefully I will get to enjoy it next summer.. Jamie

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