What is a Predicted Log Contest?

This is a contest where each skipper attempts to most accurately predict the time it will take to navigate a specified course. Before the commencement of the contest, each skipper must turn in predicted logs with the course they are following and the time which they expect to arrive at each waypoint along the course. There will be Observers at each waypoint to accurately log the time each boat arrives. At completion, the Race Committee computes the percentage error between the predictions and actual for each boat. The skipper with the lowest error is the winner.

Anyone is capable of winning a Predicted Log contest
You do not have to be a navigation wizard and even the novice navigator can stand an even chance of winning. All you need is some simple speed data and a basic understanding of the procedure for calculating your log.

  1. Choosing a speed.
    You do not have to go faster than the other boats. You can cruise at a speed that is comfortable for you and your boat. You must know how fast your boat goes at the RPMs that you are cruising at. That should remain constant no matter what the sea conditions to achieve your goal.
  2. Running the mile.
    You should be able to calculate you speed at set RPMs by running a measured nautical mile. Set your throttles carefully and use a stopwatch to measure the time it takes you to run the distance. You should run it several times to ensure each run is consistent. If you have done this before, you should do it again close to the contest because other factors, such as bottom growth or dirty props, will degrade your calculations. You should also factor in sharp turns on the course where speed will be lost.
  3. Calculating Average Speed.
    Now you will want to determine the average speed of your boat in seconds per nautical mile. Take the average of your test runs and convert into seconds. (ex: 4 min 25 sec = 256 seconds) Later you will use this average to figure the time needed to travel a given distance by simply multiplying it times the distance.
  4. Plotting the Course.
    Next you need to plot the contest course. The instructions will list the start, intermediate and finish points. Once you have identified the points on your chart, draw the lines and measure the distance for each leg. Make sure you plot accurately. Use current charts as deviations from your course dramatically impact your predictions.
  5. Calculating Leg Times
    Calculate each leg of the points by taking the measurement from your line and multiplying your Average Speed Seconds by that distance. You will need to adjust a bit to allow your boat to come up to speed, or to make sharp turns. A table is provided here to help adjust for turn times. (A turn angle is the number of degrees your compass will swing when going from one heading to another.)

    TURN ANGLE   ADD
    0 to 60 Degrees0 seconds
    60 to 90 Degrees5 seconds
    90 to 110 Degrees10 seconds
    110 to 125 Degrees15 seconds
    125 to 140 Degrees20 seconds
    140 to 150 Degrees25 seconds
    150 to 165 Degrees30 seconds
    165 to 175 Degrees35 seconds
    Always add the turn-time allowance to the travel time of the leg following the turn.

  6. Converting Your Time.
    Now you have the total times you will predict for each leg. To convert the seconds into usable time: If the leg time exceeds 3600 seconds, subtract 3,600 for each hour in the leg. Now divide the result by 60. The digits to the left of the decimal point are the minutes in the leg. Subtract the minutes from the result so that the number to the left of the decimal point is zero and multiply the decimal value by 60 to find the seconds.
    Example: assume leg time is 4317 sec,
    4317-3600 (1 hour) = 717,
    717/60 =11.95,
    11.95-11 (11 min) = .95,
    .95 x 60 = 57 sec.
    Result : 1.11.57
  7. Filling Out the Log.
    As you fill out your form, you will need to use your converted time to apply to actual clock time. You will need to fill in the clock time you expect to arrive at each waypoint and the finish point.
  8. Finishing the Contest
    You must remember to keep you speed constant, stick to your predicted route, allow for wind conditions which may alter your predicted average speed. Most of all, have fun and you will have learned more about your boat.

*This information was condensed from http://www.predictedlog.org/Education/enjoy.html