veneer racing shell restoration

Discussion in 'Wooden Boat Building and Restoration' started by Kiwi100, Jul 27, 2005.

  1. Kiwi100
    Joined: Jul 2005
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New Zealand

    Kiwi100 New Member

    I am starting to restore a 55 year old single racing shell and want to better understand the relationship between lwl and speed in such a rowing craft.
    It is a veneer shell measuring 8.5metres long. If such a craft was built longer could it travel faster? What is the theory?Any on-line info. that would clarify this?
     
  2. gonzo
    Joined: Aug 2002
    Posts: 11,926
    Likes: 174, Points: 63, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    It could travel faster, but would need more power.
     
  3. PAR
    Joined: Nov 2003
    Posts: 18,026
    Likes: 353, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Typical shells are what we call displacement forms. They, by their shape, available power or both are limited to a speed governed by their waterline length (LWL) They lack the shape, power or both to overcome the resistance and wave system they generate as they move through the water. Provided enough power they can partly or fully climb over this wave train system and travel at higher speeds. Generally they are not shaped very well for doing this and if were over driven would likely become unstable and capsize. Speeds over the theoretical max hull speed (the square root of the LWL times the speed to length ratio) are met with a dramatic increase in resistance, generated by her shape and the wave train she's dragging along with her. To over come this the craft will need more power and or a different shape.
     
  4. Kiwi100
    Joined: Jul 2005
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New Zealand

    Kiwi100 New Member

    ok - will a twin shell rowing catamaran of the same length(but narrower) as a single hull (8metres) be faster with the same power input?
     
  5. gonzo
    Joined: Aug 2002
    Posts: 11,926
    Likes: 174, Points: 63, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    No. It will have more wave and surface resistance.
     
  6. PAR
    Joined: Nov 2003
    Posts: 18,026
    Likes: 353, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Rather then a lengthy dissertation on the principles of hydrodynamics, one question at a time, how about telling us what you'd like to do and we can address the possible issues that may arise in your efforts?
     
  7. Kiwi100
    Joined: Jul 2005
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New Zealand

    Kiwi100 New Member

    While working on restoring my racing skiff,I began to question why are single racing skiffs generally constructed to the same proportions of length(roughly 8m) to beam(roughly 300mm) and have been for many decades.
    Why 8m long?Why not longer? Why not shorter?Is this dimension "traditional" due to a physical construction reason(in timber), or a physics law?
    Is the 330mm beam decided by the minimum width that will comfortably accomodate the rowers rear-end, or is their another reason?What is the most effective theoretical length and beam in a single racing shell?
    I am not a naval architect but am simply trying to understand "why".
     

  8. gonzo
    Joined: Aug 2002
    Posts: 11,926
    Likes: 174, Points: 63, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    I use to row a four. The hull shape is determined by the crew. A burly crew needs a beamy boat which requires more power to move. A skinny crew can have a narrower boat which needs less power. It ends up balancing out nicely.
     
Loading...
Similar Threads
  1. srimes
    Replies:
    1
    Views:
    906
  2. dinoa
    Replies:
    10
    Views:
    1,997
  3. fpjeepy05
    Replies:
    58
    Views:
    13,591
  4. mcm
    Replies:
    21
    Views:
    3,382
  5. mcm
    Replies:
    7
    Views:
    1,704
  6. Corley
    Replies:
    3
    Views:
    1,858
  7. JLIMA
    Replies:
    6
    Views:
    1,774
  8. mcm
    Replies:
    21
    Views:
    2,964
  9. David G
    Replies:
    6
    Views:
    2,736
  10. sieagel
    Replies:
    1
    Views:
    2,507
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.