Design for worst case scenario

Discussion in 'Boat Design' started by Mik the stick, Jan 11, 2013.

  1. tom28571
    Joined: Dec 2001
    Posts: 2,474
    Likes: 116, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    Ditto, but needs qualifiers. If you look at the majority of boats that do cross oceans, power and sail, you will see that most have transom sterns, not double ended or round sterns. There is much more to the question than that. Some boats founder in inlets on both coasts each year. No big storm needed. Some of it is aided by big wide immersed transoms but much is due to other reasons, notably poor seamanship.
     
    1 person likes this.
  2. SamSam
    Joined: Feb 2005
    Posts: 3,900
    Likes: 197, Points: 63, Legacy Rep: 971
    Location: Coastal Georgia

    SamSam Senior Member

    The question is 'will it handle really badly in a following sea.' Downwind is a different condition. A worst case scenario is in the title.

    The question is so broad and so vague things have to be assumed. So I assume a slow displacement (so probably narrow with a fine entry) boat with a big vertically and horizontally flat transom with sharp edges being overtaken by steep breaking waves.

    I haven't followed any of the OPs threads, so whether a 50 or 40' ocean cruiser is being contemplated, I don't know. Sailboat or motorboat, I don't know. It doesn't sound like owning a boat is even in the works, but just thinking about it and asking questions about design is the end plan.

    But a transom like I described being pushed around by following seas does not handle well, the rudder almost becomes a liability, and if the bow digs in and the stern is pushed aside, I would say that very soon things will be going very badly.

    And that type of transom is the easiest for that type of situation to develop or to have happen.

    The OP should supply more information for much better answers than I give.
     
  3. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    The alternative, a canoe stern, is attractive. They work but the shape of the stern affects its usability. Swim platforms, tenders.......

    A boat needs to perform many tasks.

    http://[​IMG]
     
  4. tom28571
    Joined: Dec 2001
    Posts: 2,474
    Likes: 116, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    Here is a video of two boats in a inlet that are barely making it through. Some real balls in these wheelhouses. Would not want to have the proverbial wide immersed transom in this kind of following sea. Don't know how much the round sterns helped but, on these particular boats, they certainly didn't hurt. One seemed to have some kind of anti roll thing out to port. Not sure if it helped or caused some of the apparent tendency to broach to port. Interesting case of what we are talking about though.

    http://www.youtube.com/embed/ByGSMmenPDM?rel=0
     
  5. Number4

    Number4 Previous Member

  6. tomas
    Joined: Nov 2012
    Posts: 281
    Likes: 16, Points: 0, Legacy Rep: 147
    Location: California

    tomas Senior Member

    I can understand why these threads are annoying to some but for a beginner like myself, I benefit by reading the responses from those with knowledge and experience.

    I have found that the majority of you are both patient and generous with your thoughtful responses, which in the aggregate, creates a forum with tremendous resources for anyone who wants to learn.


    P.S. I enjoy your posts SamSam. I picture you rolling your eyes at the screen while you read, shaking your head while you decide how to express your annoyance. It make me smile. Perhaps I will annoy you as well in the near future when I begin posting lots of questions regarding my dream project.
     
  7. WestVanHan
    Joined: Aug 2009
    Posts: 1,374
    Likes: 56, Points: 0, Legacy Rep: 746
    Location: Vancouver

    WestVanHan Not a Senior Member

    Thing is Tomas,almost all of the questions asked-the answer can be found by searching the forum. Or a quick look on google.

    My pet peeve is someone takes time to sign up,then asks and expects people to look it up and tell him (for example) how much an engine weighs.
    Typing 10 letters into google will tell him in 3 seconds....

    However there are more esoteric things that need refreshing,and I take the stand that if new rounds of people don't come in and everybody used the search-this forum would grind to a halt...and that would be a shame as there are many designers and builders and boat lovers on here wanting to help out.

    So ask away,if it's dangerous or a bad idea you'll find out in a hurry. :)
     
  8. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

  9. tomas
    Joined: Nov 2012
    Posts: 281
    Likes: 16, Points: 0, Legacy Rep: 147
    Location: California

    tomas Senior Member

    Yes, I've noticed that. I agree that it is annoying, rude and selfish to just be lazy and ask others to do the work for them.

    My point was that the responses often are more than just a direct answer. Typically, there is also mention of important things that need to be considered that is beyond just a direct answer which may not occur to me.

    Sometimes, there are thread discussions that spin off into other informative themes where people with decades of experience informally share something of great interest to me. Then, there may also be links to other (for me, obscure) information I would never find on my own.

    Really great. I'm very appreciative.
     
  10. JRD
    Joined: May 2010
    Posts: 228
    Likes: 18, Points: 18, Legacy Rep: 192
    Location: New Zealand

    JRD Senior Member

    As I recall the Grey river was in record flood and running at about 6-7 knots at the mouth, along with the storm, this was causing the standing waves.
    Harbourmaster was waiting for them at the wharf for a dressing down..... but i bet the crews didnt have to pay for a single beer in the bar that night.

    I think more boats were lost coming into those west coast rivers in the 1800s than the rest of the country since. But as you say the "coast" is truly spectacular, at least when the rain stops :rolleyes:
     
  11. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 478, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I learned boat handling running inlets like this. They struggled a bit, but for the most part rode through under control. I'm not sure what gear was "hung up" to port on the one boat, but the skipper held tough and managed to keep the keel under him, most of the way. The boat further back seems to be in broaching situations more often, but his stern was flat and getting kicked around, while the one with the fouled gear (my assumption) was elliptical. I also think both boats where struggling to keep up with the sea, likely from loads aboard. A little more speed and they could have rode the back of one of those puppies, right through. I'm not sure it was foolish, so much as a days work, they wished had better weather.
     
  12. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 110, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    No question a round stern looks nautical, but I have never seen a yacht put it to actual use.

    Back the stern against a piling or a wall to turn the boat.

    Perhaps pretty yachty rub rail is too nice to actually put to use?
     
  13. tom28571
    Joined: Dec 2001
    Posts: 2,474
    Likes: 116, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    I have never been in an inlet over a bar quite this bad. Bad enough that I wished I had taken another route a few times though. Got caught in Murrell's Inlet, SC in breaking waves over the bar in a little 12 foot runabout once and managed to live to tell about it in my younger and more ignorant days. One thing that I noticed is that I am glad to have a good outboard on the stern to direct considerable steering force to counteract slewing of the stern in following waves. Of course an outboard would be useless for these boats.

    These guys had holds full of fish and running out of ice which made them take the chance.
     
  14. Number4

    Number4 Previous Member

    After watching the video posted before about Greymouth bar, I found this very interesting film about NZ river bars. It is an educational film for fishermen, mainly set at Greymouth and Westport, which is the next town up the coast.
    It is in 10 x 10 minute episodes.
    http://www.youtube.com/watch?v=0a44Zdp38iM
    There is an interesting piece in part 6 at about 4 minutes when John Harry describes very well what happens to a boat as it crosses the bar with use of a model.
    Favourite quote:-" I was watching the bar from the tip. This boat was having a hell of a time getting across it. When he finally made it through, and was motoring up the river, he came on deck in only a t shirt, waving his underpants. I think he was trying to tell us that he had shat himself."
    I hope you enjoy,
    Adam
     

  15. WestVanHan
    Joined: Aug 2009
    Posts: 1,374
    Likes: 56, Points: 0, Legacy Rep: 746
    Location: Vancouver

    WestVanHan Not a Senior Member

    If you want some terror,come to British Columbia...12-18 knot tidal runs in and out of inlets- 15 minutes of slack. Lots of standing waves,lots of inlets and narrows.

    I was involved in this,can't hear me as those parts were edited out.

    Don't know if they ever found his body.. i remember all these words like it was yesterday.

    http://www.youtube.com/watch?v=gNXDgFUzq8w

    So in my area, a design for worst case demands a capability for speed-which is what I have
     
Loading...
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.