User Tag List

Results 1 to 14 of 14
  1. #1
    Join Date
    Dec 2011
    Location
    Ludington michigan,on the shore
    Posts
    2,875
    Thanks (Given)
    50
    Thanks (Received)
    128
    Likes (Given)
    75
    Likes (Received)
    518
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)

    Weight&balance records

    Do any of you keep a weight&balance record for your boat.How many know where there static cg is? I'm thinking i'm going to start a weight&balance log,starting with the bare weight of the hull,and the bare center of gravity.Then weigh all parts that go into the boat,starting at the cg and asigning a station number every six inches for and aft of static cg.It would be similar to how we keep our aircraft within limits.Makes ajustments easier and to some degree safer,as well as keeping track of that ever increasing gross weight!!! Thoughts?

  2. #2
    Join Date
    Feb 2009
    Location
    Edgewater,B.C. CANADA
    Posts
    6,896
    Thanks (Given)
    78
    Thanks (Received)
    119
    Likes (Given)
    1310
    Likes (Received)
    501
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You need to get Jim Russell's Tunnel Boat Design Program, once you have all the weights and measurements you can make changes on the computer and see how it will effect performance.
    As far as the ever increasing gross weight goes, go to the gym.lol

    Dave
    1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
    1988 BAJA Sunsport 186, 96 225 Pro Max
    79 12' Auminum, 95 Merc 9.9
    RIP Stu
    "So many idiots, so few bullets"

  3. Thanks Jimboat thanked for this post
  4. #3
    Join Date
    Dec 2011
    Location
    Ludington michigan,on the shore
    Posts
    2,875
    Thanks (Given)
    50
    Thanks (Received)
    128
    Likes (Given)
    75
    Likes (Received)
    518
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    It would seem a "program"would be specific to a certain hull,in order to be accurate.As for the gym,no thanks my personal gross weight is down 147# from this time last year

  5. #4
    Join Date
    Feb 2009
    Location
    Edgewater,B.C. CANADA
    Posts
    6,896
    Thanks (Given)
    78
    Thanks (Received)
    119
    Likes (Given)
    1310
    Likes (Received)
    501
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by outasite View Post
    It would seem a "program"would be specific to a certain hull,in order to be accurate.As for the gym,no thanks my personal gross weight is down 147# from this time last year
    The program needs a ton of inputs and is very accurate. Ask Greg or Helmut, Jim is a Engineer and specializes in boat design. You need the program to really see how cool it is.

    Dave
    1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
    1988 BAJA Sunsport 186, 96 225 Pro Max
    79 12' Auminum, 95 Merc 9.9
    RIP Stu
    "So many idiots, so few bullets"

  6. Thanks Jimboat thanked for this post
  7. #5
    Join Date
    Dec 2011
    Location
    Ludington michigan,on the shore
    Posts
    2,875
    Thanks (Given)
    50
    Thanks (Received)
    128
    Likes (Given)
    75
    Likes (Received)
    518
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Dave Strong View Post
    The program needs a ton of inputs and is very accurate. Ask Greg or Helmut, Jim is a Engineer and specializes in boat design. You need the program to really see how cool it is.

    Dave
    Thanks for the info!

  8. #6
    Join Date
    Nov 2011
    Location
    East Wallyworld Vt
    Posts
    1,133
    Thanks (Given)
    1
    Thanks (Received)
    8
    Likes (Given)
    2
    Likes (Received)
    26
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I have a full W&B on my Glastron, I use the transom as the datum. I gathered my initial data weighing the trailer with and without the boat with a set of digital race car scales. This method allows me to be in the boat so I could determine where to place the jack pump and battery as I was rebuilding her.
    FWIW the boat with 5 gal fuel is 1622 pounds with the CG 51" forward of the transom.
    Regards,
    Charlie North
    If it ain't broke, modify it.
    87 Glastron CVX20 with Yamaha ProV 150 power
    80 21' Superboat to be powered with a turbocharged 4 stroke OB

  9. #7
    Join Date
    Feb 2009
    Location
    Edgewater,B.C. CANADA
    Posts
    6,896
    Thanks (Given)
    78
    Thanks (Received)
    119
    Likes (Given)
    1310
    Likes (Received)
    501
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    When I first got the program to use to build up my Cougar had accurate info for my altitude and 1400' lower. Had all the info dialed in and got sick and broke have not got the Cougar back together. Input the info from my BAJA and it predicts speed within 1% if you add weight of a passenger or 2.
    It is for real.

    Dave
    1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
    1988 BAJA Sunsport 186, 96 225 Pro Max
    79 12' Auminum, 95 Merc 9.9
    RIP Stu
    "So many idiots, so few bullets"

  10. #8
    Join Date
    Feb 2009
    Location
    Edgewater,B.C. CANADA
    Posts
    6,896
    Thanks (Given)
    78
    Thanks (Received)
    119
    Likes (Given)
    1310
    Likes (Received)
    501
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by CharlieN View Post
    I have a full W&B on my Glastron, I use the transom as the datum. I gathered my initial data weighing the trailer with and without the boat with a set of digital race car scales. This method allows me to be in the boat so I could determine where to place the jack pump and battery as I was rebuilding her.
    FWIW the boat with 5 gal fuel is 1622 pounds with the CG 51" forward of the transom.
    Static CG is one thing, tunnels really show how CG moves as speed, aero and hydrodynamic forces change as you go faster. 1deg in bow rise can make a big diff in dynamic CG.

    Dave
    1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
    1988 BAJA Sunsport 186, 96 225 Pro Max
    79 12' Auminum, 95 Merc 9.9
    RIP Stu
    "So many idiots, so few bullets"

  11. Likes Jimboat liked this post
  12. #9
    Join Date
    Apr 2001
    Location
    Ontario, Canada
    Posts
    696
    Thanks (Given)
    37
    Thanks (Received)
    14
    Likes (Given)
    145
    Likes (Received)
    57
    Mentioned
    1 Post(s)
    Tagged
    3 Thread(s)
    Quote Originally Posted by Dave Strong View Post
    Static CG is one thing, tunnels really show how CG moves as speed, aero and hydrodynamic forces change as you go faster. 1deg in bow rise can make a big diff in dynamic CG.
    Dave
    This article on Dynamic Stability might be of interest: http://www.aeromarineresearch.com/dy...stability.html
    Last edited by Jimboat; 08-17-2015 at 07:38 AM.

  13. Likes Dave Strong liked this post
  14. #10
    Join Date
    Nov 2011
    Location
    East Wallyworld Vt
    Posts
    1,133
    Thanks (Given)
    1
    Thanks (Received)
    8
    Likes (Given)
    2
    Likes (Received)
    26
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Dave Strong View Post
    Static CG is one thing, tunnels really show how CG moves as speed, aero and hydrodynamic forces change as you go faster. 1deg in bow rise can make a big diff in dynamic CG.

    Dave
    I want to clarify something here, the CG does not move. The center of pressure and the center of lift are what develop and in cases, move. These are what act on the center of gravity.
    Regards,
    Charlie North
    If it ain't broke, modify it.
    87 Glastron CVX20 with Yamaha ProV 150 power
    80 21' Superboat to be powered with a turbocharged 4 stroke OB

  15. #11
    Join Date
    Jun 2007
    Location
    Singapore/Melbourne
    Posts
    4,318
    Thanks (Given)
    219
    Thanks (Received)
    63
    Likes (Given)
    603
    Likes (Received)
    259
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    how do you work out where the centre of lift is and is that with or without the prop effect?

  16. #12
    Join Date
    Nov 2011
    Location
    East Wallyworld Vt
    Posts
    1,133
    Thanks (Given)
    1
    Thanks (Received)
    8
    Likes (Given)
    2
    Likes (Received)
    26
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I can calculate COL on an aircraft but have no clue on a boat.
    The lift on a boat comprises the hydrodynamic lift, aerodynamic lift and the propeller forces. That is all beyond me mate.
    Jimboat sure can do the hydrodynamic part, not sure how one can accurately get the rest though.
    Regards,
    Charlie North
    If it ain't broke, modify it.
    87 Glastron CVX20 with Yamaha ProV 150 power
    80 21' Superboat to be powered with a turbocharged 4 stroke OB

  17. #13
    Join Date
    Apr 2001
    Location
    Ontario, Canada
    Posts
    696
    Thanks (Given)
    37
    Thanks (Received)
    14
    Likes (Given)
    145
    Likes (Received)
    57
    Mentioned
    1 Post(s)
    Tagged
    3 Thread(s)
    Quote Originally Posted by powerabout View Post
    how do you work out where the centre of lift is and is that with or without the prop effect?
    Quote Originally Posted by CharlieN View Post
    I can calculate COL on an aircraft but have no clue on a boat. The lift on a boat comprises the hydrodynamic lift, aerodynamic lift and the propeller forces. That is all beyond me mate. Jimboat sure can do the hydrodynamic part, not sure how one can accurately get the rest though.
    Location and values of forces of hydrodynamic lift/drag of lifting surfaces change throughout velocity range; aerodynamic lift/drag values and locations (center of Lift) change with several factors that include aerofoil shape (type), thickness, aspect ratio and height (above water surface); center of force for lower unit & propeller is significant but location is generally stable. All these factors change (some very significantly) throughout the velocity range based on several design, setup and operating factors. All can be calculated accurately, and have a significant effect on dynamic stability of hull. Static CG is the only force acting that remains in the same location, represents the deadweight of hull only (this is why you can't dynamically balance your boat on the trailer).

    Here's another article that discusses "How Weight and Weight Distribution is Important to Performance"

    More detailed articles here: http://www.aeromarineresearch.com/pe..._articles.html
    Last edited by Jimboat; 07-10-2016 at 05:24 PM.

  18. Likes Dave Strong, AZMIDLYF, powerabout liked this post
  19. #14
    Join Date
    Jun 2015
    Location
    Arizona
    Posts
    4,134
    Thanks (Given)
    7
    Thanks (Received)
    134
    Likes (Given)
    1250
    Likes (Received)
    2451
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    subbed

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Aeromarine Research