making a daggerboard longer

Discussion in 'Multihulls' started by seandepagnier, May 7, 2021.

  1. seandepagnier
    Joined: Oct 2020
    Posts: 13
    Likes: 2, Points: 3
    Location: the sea

    seandepagnier Junior Member

    I am interested possibly changing my trimaran daggerboard to only be 18" rather than 22" wide, and increasing the 38" in length somewhat to compensate for any lost area.

    The reason is, at 22" the dagger is stopped by the aka under the mast so it cannot fully retract which means the boat cannot careen.

    My understanding is the amount of daggerboard area needed varies with speed. It's more complicated than this I know, but assuming flat sea, from what I can understand few if any boats have enough surface area for the lightest possible winds making me consider adding another foot or so in length to use in the lightest air.

    The other consideration is, the angle of 45 degrees means that as the board is lowered, the position also is moving backwards. My concern here is that isn't this the opposite of what you want in lighter wind, or am I mistaken? Would a different angle be better?
     
  2. Scuff
    Joined: Nov 2016
    Posts: 127
    Likes: 15, Points: 18, Legacy Rep: 10
    Location: Richmond VA

    Scuff Senior Member

    Are you saying the daggerboard can't be removed from the case? Is the boat demountable?
     
  3. seandepagnier
    Joined: Oct 2020
    Posts: 13
    Likes: 2, Points: 3
    Location: the sea

    seandepagnier Junior Member

    Currently, the board can only be removed from the bottom which is hard to do if the boat is in the water since the board floats.

    If I narrow it to 18" instead of 22", it will be able to come out through the deck as well as be longer and have more contact in the box when fully deployed.
     
  4. Scuff
    Joined: Nov 2016
    Posts: 127
    Likes: 15, Points: 18, Legacy Rep: 10
    Location: Richmond VA

    Scuff Senior Member

    Is the case rectangular or shaped like the board?
     
  5. seandepagnier
    Joined: Oct 2020
    Posts: 13
    Likes: 2, Points: 3
    Location: the sea

    seandepagnier Junior Member

    The case is rectangular.

    So I am debating inserting foam and plastic to reduce the case by 4 inches, or to cut the case and rebuild it 4 inches smaller which is difficult to glass on the inside again.

    If I can use foam and starboard (to slide on) perhaps it can also compress the foam in a crash?
     
  6. Scuff
    Joined: Nov 2016
    Posts: 127
    Likes: 15, Points: 18, Legacy Rep: 10
    Location: Richmond VA

    Scuff Senior Member

    How often do you need to careen? If it had to be attempted I would try the insert approach. Does the board need to move forward out aft to accommodate removal?
     
  7. seandepagnier
    Joined: Oct 2020
    Posts: 13
    Likes: 2, Points: 3
    Location: the sea

    seandepagnier Junior Member

    It is not only to careen but fully retracting the board gives me a 2ft draft. Currently the board sticks out 8 inches fully retracted. If I make it higher aspect (from 22 down to 18) which is not a huge change, I can cut a hole in the deck forward of the mast it can exit through.

    My biggest concern is how a higher aspect board will affect sail balance in different conditions. The board can be partially retracted at higher speeds, but it moves forward doing so, since it is at a 45 degree angle. From my limited experience the boat has more weather helm with more wind and boat speed which is exactly the opposite.
     
  8. Scuff
    Joined: Nov 2016
    Posts: 127
    Likes: 15, Points: 18, Legacy Rep: 10
    Location: Richmond VA

    Scuff Senior Member

    The weather helm issue could also be rig related couldn't it?
     

  9. catsketcher
    Joined: Mar 2006
    Posts: 1,306
    Likes: 148, Points: 63, Legacy Rep: 790
    Location: Australia

    catsketcher Senior Member

    Hi Sean

    That sounds like a lot of rake for a board. Farrier tris usually cut a portion of the board to get it to come up further. Would it be possible to cut a section of the board out? Say the aft edge up top. Then you can pull the board up and leave the underwater section the same. A photo would help me understand the situation.
     
    redreuben likes this.
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