Help me design the Filling of my Transom

Discussion in 'Fiberglass and Composite Boat Building' started by Dnice, Feb 17, 2010.

  1. Dnice
    Joined: Mar 2007
    Posts: 3
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    Location: by the sea in SD

    Dnice New Member

    I need to raise my motor up about 1.5 to 2 inches to get the cav plate lined up with the keel. As you can see, the motor clamps and upper mounting bolts are already high and will be above or too close to the top of the transom in which I'm afraid may rip out. Should I:

    a) rebuild transom?- How? I was thinking of doweling into the existing transom and using two plates to make a mold about 2 inches above and the entire width of the notch and fill the mold with chopstrand resin, or do the whole wood and glass thing.

    b) would I be better off with a jack plate? Homemade as Im on a budget. But i might need to reroute the steering cable or modify transom for it.

    Any advice and suggestions on design are welcome. I have a few ideas but cant decide.

    Thanks, see pics below
  2. Guest62110524

    Guest62110524 Previous Member

    the best way me boy is to buy a big thick aluminum plate say 500mm wide say 16mm thick, and cover the transom mount area, the reason so thick is, you do not have welding gear to fabricate a hollow section, bolt it to the transom using c/s bolts and then pack it for thickness with a hardwood such as Kwila
    I am sure there are many solutions, but this is an easy one
    oh I see 50 hp 12mm is enough
  3. Itchy&Scratchy
    Joined: Jul 2008
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    Location: Oxford & South Africa

    Itchy&Scratchy Senior Member

    Hey Dnice
    Ive done a few the way you want to do it. Im not a fan of using bits of wood
    as fillets, so I normally use something like two pieces of masonite or melamine screw them to either side to form a temporary mould and cut long strips of chopped starnd matt , wet them out and lay them in until you reach the top which you have set at the height you want to extend by.
    It is advisable to not do it all in one go as the heat buildup can be quite high cause of the mass of you layup.If you leave it too long though in between layups remember to key up the existing surface with 40/60 grit paper before laminating the rest.
    Also remember to grind all the gel off around the area you want to extend. Somewhere else in the forum there is a thread dealing with 'whether it is advisable to grind all the gel off or not' but I would personally advise you to.
    Once done , and left overnight remove your temporary moulds and grind/sand to shape before regelling.
    I would also advocate adding a aluminium plate on the rear of the transom, to spread any load.
    Judging by your pics I would also consider some bigger plates under the bolts holding the motor on as those washers arent doing the job- you can see by the way the existing laminate is getting crushed.
    Have fun
  4. rozordermit
    Joined: Mar 2010
    Posts: 1
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    Location: london

    rozordermit New Member

    Yes, what he said is true. By using big thick aluminium plate we can cover the transom mount area.

    temporary hangar for planes
  5. mark775

    mark775 Guest

    I don't think I agree with any of the above. Itchy, what holds the new glass there against the weight of an outboard bouncing around and thrusting? I would consider mortising a heavy layup into the existing transom where someone has cut it down, glassing over and gel-coating but I'm afraid that there may be moisture in the transom. Aluminum panel, I like but I'd break it to form an ID to slide over the transom and hide the cut-away. I did this same thing once (below), and did both. This one holds a 225 for the last couple of years of hard use and no signs of problems. Don't have a pic with the aluminum but it looked sharp.
    Before; The owner needed to lose the stupid outboard bracket that made it 27 feet from the fisherman to the fish on a 25 foot boat.

    A genius nailed a bunch of boards up to keep from pooping the well. You won't see this in yachting

    I wasn't kidding

    The soundest part of the boat was the ply/glass on the sides of the well so we cut mortices and tenoned this eight inches and glassed inside across the transom to distribute the load.

    Stout tenon puckied in place. Overkill? Not too much with a 225 hangin' back there. If I could have somehow tied it into substantial stringers, I would have done that, too.

    After. The boat came out looking like a new penny and the guy grumbled about the cost. I should have just done "probably good enuf".

    You don't have to make the thing as expensive as what I have done to this one, but you should know that there is no rot in that transom and that your mod will not crack.
  6. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    I would lagscreww a 2X2 and then fiberglass over. You can do it in about an hour.

  7. jerseysportfish
    Joined: Feb 2010
    Posts: 7
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    Location: Peoples Republic of NJ

    jerseysportfish Junior Member

    mark, i'd almost swear thats an old master marine, except for the chines. Is that an old mako ?
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