Desirable trim

Discussion in 'Hydrodynamics and Aerodynamics' started by muthubd14, Sep 6, 2014.

  1. muthubd14
    Joined: Mar 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: chennai

    muthubd14 Junior Member

    Hi all.. It is said that trim by aft is desirable for a vessel..But too much trim is undesirable too.

    Could some one help me out in determining the optimum trim fr 90 m vessel operating at Fr= 0.45....
     
  2. TANSL
    Joined: Sep 2011
    Posts: 6,818
    Likes: 500, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    If the vessel is designed with trim = 0, the optimal trim is zero.
     
  3. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yep, it's that time of year again . . .
     
  4. TANSL
    Joined: Sep 2011
    Posts: 6,818
    Likes: 500, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    It is very possible but I think that "that time" will take years for them.
     
    1 person likes this.
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Very valid point my friend . . . :)
     
  6. DCockey
    Joined: Oct 2009
    Posts: 5,030
    Likes: 515, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    So how should "optimum trim" be determined for a new design? What is meant by "optimum trim" - trim for lowest resistance?
     
  7. muthubd14
    Joined: Mar 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: chennai

    muthubd14 Junior Member

    yeah... The value of trim for which better speed could be achieved..??
     
  8. TANSL
    Joined: Sep 2011
    Posts: 6,818
    Likes: 500, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    The designer should calculate the boat with a trim that makes the boat run as smoothly as possible, when operating normally. That trim, whichever it is, is defined as zero trim.
    If the ship to operate in its normal form, acquires a non-zero trim, the designer has miscalculated the ship.
    This is my opinion and, like everything, is debatable.
    You talk of better speed. What does that mean, under what conditions will be reached?
     
    Last edited: Sep 10, 2014
  9. farjoe
    Joined: Oct 2003
    Posts: 163
    Likes: 1, Points: 18, Legacy Rep: 26
    Location: med

    farjoe Senior Member

    we have similar questions on a newly delivered new boat whose ratings indicate that we should be faster than what we are achieving now.

    For example his polar data indicates that the optimum VMG at 4 knots true is achieved at 2 degrees heel.

    Current techniques on most boats at this speed is to send the crew to leeward to heel the boat.

    Is the data given simply the result of were his VPP achieved balance with non movable weights or is it really the best heel (lowest hull resistance) at this wind speed?
     
  10. TANSL
    Joined: Sep 2011
    Posts: 6,818
    Likes: 500, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Hull resistance depends inter alia on the friction (wet surface) and the formation of waves. So the heel that makes minimal these two factors will produce the least resistance.
    I am not an expert in hydrodynamics but do not think the heel improves hull resistance. However, due to other factors, may be, I donĀ“t now, the boat heeled is faster than upright :?::?:
     
  11. Ike
    Joined: Apr 2006
    Posts: 2,542
    Likes: 377, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    You are talking apples and oranges here. The original question was for a powered vessel (I think). The quoted vessel is a sail boat. Yes it is often true that a sail boat will perform better at a specific heel angle, but not a powered vessel. So which is it?
     
  12. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I think the point is moot Peter, as it's probable his assignment is due and he's handed in his answers to his instructor by now. Ain't the net grand . . . The worst part is 10 years from now, this guy's going to pen up a 150' ferry for someplace in southeast Asia . . .
     
  13. Ike
    Joined: Apr 2006
    Posts: 2,542
    Likes: 377, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    most likely
     

  14. farjoe
    Joined: Oct 2003
    Posts: 163
    Likes: 1, Points: 18, Legacy Rep: 26
    Location: med

    farjoe Senior Member

    Rereading the original question, you are probably right. My question is however still a valid valid one. Maybe I should start up a separate thread.
     
Loading...
Similar Threads
  1. massandspace
    Replies:
    4
    Views:
    514
  2. nzl51
    Replies:
    5
    Views:
    764
  3. Surfer Naval Architect
    Replies:
    0
    Views:
    3,242
  4. Barry
    Replies:
    12
    Views:
    3,861
  5. surfbus
    Replies:
    44
    Views:
    8,956
  6. jlconger
    Replies:
    62
    Views:
    9,400
  7. steve.1326
    Replies:
    9
    Views:
    4,558
  8. Mr Efficiency
    Replies:
    3
    Views:
    1,926
  9. Anum
    Replies:
    1
    Views:
    2,217
  10. khabiran
    Replies:
    0
    Views:
    1,705
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.