Create trim tabs from IPE or Cumaru wood

Discussion in 'Powerboats' started by sdowney717, Jul 16, 2014.

  1. sdowney717
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    sdowney717 Senior Member

    Both woods are very strong, I am sure I can make a wood panel that will function. Both woods are worm resistant, maybe worm proof.

    The issue is creating a hinge. Tabs move up to 20 degrees.

    I dont want a metal hinge unless it could be bronze.
    So was thinking a reinforced rubber hose, like used for water pressure applications sliced down the center.
    That creates a long flat section that can be the hinge.
    I have a section of 3 inch diameter red rubber reinforced thick hose that I think is pretty strong. That hose is about 5/16 inch thick material. It is not exhaust hose, it is water pressure hose as would be used in an engine coolant system.

    The rubber to be attached onto stern with a wood piece on top and also on the trim tab.

    Will such a hose survive as a hinge without tearing?

    My current 304 SS tabs are eaten by corrosion and are from 1970.

    Dimensions of current tab are 36 inch long and 12 inch chord width.
     
  2. gonzo
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    gonzo Senior Member

    A soft hinge like that will wobble and not be able to control trim properly. You need a hinge made of rigid materials. What is the problem with SS hinges that last 44 years?
     
  3. sdowney717
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    sdowney717 Senior Member

    Replacement cost for a whole set of new tabs is pricey and they are only 304 SS.
    and
    I like being creative and experimenting.

    Rubber will stretch some. It is a reinforced hose. I could make the tabs longer than 3 feet which would spread the force out.
    I could buy very thick walled heavily reinforced hose without metal insert, the kind used for packing glands.
    This type of wood is very stiff and strong. The wood tabs I make would be stronger than the original 304 SS.

    Zoro sells a 3 foot 316 SS hinge.
    http://www.zoro.com/i/G2249222/?category=5360

    How would 316 hold up versus 304 SS?
    And would this Zoro hinge be strong enough.
     
  4. gonzo
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    gonzo Senior Member

    316 is much more resistant to corrosion. As far as "stronger", what do you mean by it? A steel trim tab can get hit and will bend, while a wooden one will split along the grain.
     
  5. sdowney717
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    sdowney717 Senior Member

    Consider a panel of Cumaru or IPE one inch thick made of 1 by 1.5 inch strips edge glued and screwed together with perpendicular edge pieces glued and screwed to the grain, it will not split apart.
    The main panel boards to run same as the boat planks.
    I suppose with an extreme smashup it might. In that case likely the hull itself will be also damaged.

    The boat has a very strong teak platform made of 2 inch thick wood that extends beyond the underwater tabs by a good amount.

    Do you have experience with this wood? It is one of the strongest most dense wood you can get.

    For example
    http://www.wood-database.com/lumber-identification/hardwoods/cumaru/

    IPE is only a little bit stronger than Cumaru.

    I bought a plank of Cumaru for the worm shoe and it is nice wood.
     
  6. gonzo
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    gonzo Senior Member

    I do have experience with those species of wood. Fabricating something that is rigid and then attaching it with a sloppy hinge made out of a piece of hose is a bad plan. There is nothing wrong with SS tabs. Millions of them are in use with no problem. If you really want to spend the extra time and money on wooden ones as a hobby project, that's OK. At least attach them with sturdy metal hinges.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Bear in mind you can't allow any gap between a hinged plate and the transom, otherwise you will have a nice fountain effect as pressurized water squeezes through the gap.
     

  8. gonzo
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    gonzo Senior Member

    A pretty rooster tail
     
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