Axe Bow concept

Discussion in 'Boat Design' started by jmercer, Oct 2, 2009.

  1. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Richard, that huge pic has made the reading of the page 2 a bit difficult, as the page has become much bigger than my screen (I'm using a 17" laptop at home...).
    Is it possible for you to make it become an attachment instead of an image link? :)
     
  2. Leo Lazauskas
    Joined: Jan 2002
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    Leo Lazauskas Senior Member

    I must be missing something, because the axe bow looks like an old standard Wigley hull with a bit of a bulge at the forefoot. I am sure I have seen something similar from work published over 50 years ago. As they say, a patent is only as good as the money available to enforce it... and to fight claims of prior knowledge :)

    Cheers,
    Leo.
     
  3. apex1

    apex1 Guest

    I agree, it is hughe (I did not know that when linking it).
    But I have internet access via mobile phone, which makes me well aware of download / upload traffic. So, whenever possible I like to avoid paying one € and more for just showing a picture.

    Sorry for the inconvenience.

    Richard
     
  4. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Ok Richard, no problem.

    However, my post #30 has ended up in a pretty invisible part of the screen, so I would like you guys to give some comments on that one. It is an issue which interests me a lots. Thanks. :)
     
  5. Boston

    Boston Previous Member

    it looks like one major benefit lies in minimizing vertical acceleration

    if I ca remember it right any energy spent in motion other than forward motion is directly subtracted from the energy of that forward motion
    so by lengthening the hull and reducing vertical motion more energy can be applied to forward motion

    think of it like a race cars suspension. The F-1 cars set themselves up as stiff as possible for a given course sometime literally bouncing over certain segments, same principal

    if you dampen the speed change with a flair in the bow you increase the energy expense and speed of reaction of the vessel to motion, ends up this energy has to come from somewhere and in the case of a vehicle its from forward motion. Even roll energy would be subtracted from forward motion although I think there would be some adjustment because a lot of that is wave energy being imparted on the hull

    I was thinking of the same solution but then realized that you would halve the benifit of this kind of shape

    if anyone has one of those hull form and wave form dynamic interaction programs I'l be really curious to see how a 52' total axe bow behaves in various see states

    cheers
    B
     
  6. apex1

    apex1 Guest

    Not to get you upset Boston, but you are another example of a boat / builder / buyer fixed on a certain length of a boat.

    Assuming you are not going to be moored in a fancy and expensive marina anyway, the length of the vessel is really the last point to be afraid of.

    Draw all your accommodation and engine room space (plenty of the latter) and then add several meters to achieve a proper speed without following the midgets voice in your head to add another cabin, just plain empty hull. Or a bit more elbow room in the planned compartements. Especially the greasy saloon benefits about one Meter from every foot you add (thats a miracle not mathematics).

    Planned and executed well, the extra length of say 20% will cost far less than the paint for the boat!

    Regards
    Richard
     
  7. Boston

    Boston Previous Member

    no worries
    I saw there projections of cost for adding the extra length and it was minimal
    less than paint as you mentioned

    you are correct that I have no plans for being moored in a marina for any longer than it takes to get to the fuel dock and no I didn't do anything but add the extra hull length
    nothing else changed

    one reason I only added 5' instead of the actual 25% specified is that's all I had room for on the paper :) and it looked good

    [​IMG]

    or at least I thought it did
     
  8. apex1

    apex1 Guest

    I was´nt referring to the Damen paper, that rule is valid since 5000 years and no Axe Bow is required to gain some substantial speed lengthening a design.

    Regards
    Richard

    Your bow is´nt high enough! A tad more should be.
     
  9. Boston

    Boston Previous Member

    ya I was thinking of raising the whole forward deck a bit

    thats all for another thread though

    axe bow
    how do they behave in lengths under 100'
     
  10. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Boston, I would put a nice collision bulkhead behind that axe, because if you ever hit the ground with some part of the hull, you already know what part will that be... ;)
     
  11. Boston

    Boston Previous Member

    sure will
    its in the detail drawings somewhere
    actually there will end up two of them
    one where it was originally intended and another half way between the stem and that original

    Im all about waterproof bulkheads and positive flotation

    if you look at the stairs and ladder you will see that they bisect the bulkheads above the projected flood level and well above water line
    oops just looked and the forward compartment ladder needs some adjustment to meet that goal

    Im hoping I can separate each compartment completely with ho through bulk head holes

    that whole subject is for another thread but I even want my drive shaft to run above the flooded water line and down the port side storage compartment area of the aft cabin
    all other access and vent holes in the mechanical room go straight up through the cabinetry of the wheel house and out the top

    I really like this axe bow thing but it still has yet to be shown that its stable in smaller vessels
     
  12. dskira

    dskira Previous Member

    Don't be fool by a highly specialised design for a narrow spectrum of use.
    It works on their ship, with exatly the parameter they included for a very specific set of performances.
    Stick with what it's knowne, it's allready quite difficult to design it right.
    Daniel
     
  13. LyndonJ
    Joined: May 2008
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    Location: Australia

    LyndonJ Senior Member

    IMO
    It's only there to stop the energy loss associated with slamming, as the boat pitches the bow remains in the water.
    Downside in a smaller vessel is higher wetted surface, poor collision characteristics and a very dubious validity of concept.

    The boat will still slam since you cannot get the bow down far enough, and I suspect it will be tough to steer a small boat like that in quartering waves.
     
  14. Boston

    Boston Previous Member

    honestly I have no clue how it might act but I thought I'd draw it up just for fun and see how it looked

    I have another version, same boat, heavier displacement, deeper keel that just looks more sea worthy at least to me

    [​IMG]

    still with the elongated bow but maintaining the deeper v sections forward, aft it ends in a canoe style box keel but forward its a simple v morphing into a chine form body right at the water line

    hard to see in this drawing but thats the plan

    I think I am hearing enough warnings about potential issues with the specialized bow that unless someone comes up with something definitive I'll leave the experimenting to someone else

    Daniel thanks, always a healthy dose of reality

    B
     

  15. Easy Rider
    Joined: Oct 2009
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    Easy Rider Senior Member

    I don't think the AB is going to significantly reduce "slamming" with smaller boats as they ride on their midships bottom .. not their bow. I see where the AB would be of great benefit to a vessel that cruises w most of her bow in the water. The extremely deep forefoot is nothing new but employing it w hard chines may be so.

    Easy Rider
     
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