Chine angle on edge of hull

Discussion in 'Boat Design' started by aaronhl, Mar 8, 2014.

  1. aaronhl
    Joined: Aug 2012
    Posts: 194
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Central Connecticut

    aaronhl Senior Member

    I am wondering on a hard chine hull, what characteristics does the angle outwards of the chine edge have on a V speedboat? As far as handling, speed, planing, etc.- just overall design? Should this change from transom to bow? Also height of the side of the boat? What are these areas of the hull called?

    [​IMG]
     
  2. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    You are referring to the amount of flair to the sides . Other than to give a little more interior space and help to direct spray, I cant see that it would add any thing, In fact flair would increase resistance.
     
  3. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,759
    Likes: 272, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    You mean the angle to the vertical formed by the topsides ? Most boats have some degree of flare to make ingress of water from waves splashing against the sides, less likely. Reason for that is water will pretty much shoot off parallel to what the angle of the sides is. Give the sides some outward flare, and the spray etc will go more outward than into the boat. Wind, of course, will alter the trajectory. At speed in a vee-d planing hull, it is really only the topsides forward that come into play, intermittently encountering waves, and once again the more vertical the surfaces the water meets, the more likely water will be sent vertically, and make the boat wet. Hence raked stems or flared bows. Devices such as spray rails have the effect of intercepting water climbing upwards, and deflecting it outward, away from the boat, which may also be advantageous in reducing drag by lessening the wetted area.
     
  4. aaronhl
    Joined: Aug 2012
    Posts: 194
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Central Connecticut

    aaronhl Senior Member

    Awesome those are the exact responses I needed. I am going to be building a model hull (about 4 foot in length) and I don't see this aspect being as important as other since nobody will be in the boat. Of course a small flare angle wouldn't hurt
     
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,759
    Likes: 272, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Naturally there is more to it than how much air-borne water is generated, and whether it impacts the boat, the topsides forward interact with the water significantly when running down-sea, and fast boats generally have significant rake in the bow area, both above and below the chines, to better manage such conditions.
     
  6. aaronhl
    Joined: Aug 2012
    Posts: 194
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Central Connecticut

    aaronhl Senior Member

    Can you elaborate on significant rake in the bow area? I am planing 16 dead rise at transom and I've seen Hydrostream hulls with curved sides up to the top of the bow...does that trap air and create lift?
     
  7. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,759
    Likes: 272, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    I assume your model boat is designed never to be used as a template for a full-size boat, in which case the considerations are entirely different, as a RC racer you have just to worry about maximising speed, and the thing staying right-way-up, even if you flip it, it is not serious business. In a full size boat where life and limb could be at stake, it is wholly different thinking. So, copying or comparing to full size boats may be irrelevant. You should be looking more at specialist RC designs, and less at "real" boats, to garner some clues.
     
  8. Westfield 11
    Joined: Apr 2008
    Posts: 215
    Likes: 8, Points: 0, Legacy Rep: 95
    Location: Los Angeles

    Westfield 11 Senior Member

    Flare has a lot to do with seaworthiness such as in a dory hull. The hull getting wider as it rises gives reserve buoyancy and as long as the wider hull is not in the water it will not affect the drag or resistance. This reserve of buoyancy also comes into play as the hull rolls. However since you are not building a real boat who cares? Plus a slab side is easier to build.
     
  9. messabout
    Joined: Jan 2006
    Posts: 2,985
    Likes: 191, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Aaron, is the RC boat to be a speed boat, a sailboat, a displacement type cruiser? The design characteristics of each type are different and important for the favorable operation of the boat.
     
  10. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,759
    Likes: 272, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    He speaks of " V speedboat" in the opening text.
     
  11. aaronhl
    Joined: Aug 2012
    Posts: 194
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Central Connecticut

    aaronhl Senior Member

    Yes it's a speedboat will be 48" long and have a 6hp engine to go 60mph oval racing but always in some choppy water.

    I have been told in previous threads I should be looking at strong performing Rc boat hulls, which I am, but I'm also looking to build something people haven't built before..thinking outside the box.. If these Rc boat hulls were all the same than we would be running one hull

    The boats I have just have a slight flare and the bow is not extreme, it has the same flare angle from rear to front.
     
  12. messabout
    Joined: Jan 2006
    Posts: 2,985
    Likes: 191, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    I have watched a few regattas where boats of that description compete. For me, they're the most sensible of the various classes because they have a clutch and run on gasoline and not nitro. Almost all of them are using Zenoah engines and almost all of them are of fairly conventional design.

    There seem to be flat water designs and rough water designs all of which are pretty straight forward layouts aimed at the particular conditions. The flat water ones have more nearly flat afterplanes while the rough water types are deep vees. The flatter ones are almost always faster but they do not fare as well in rough stuff.

    A slick design feature should be incorporated into the topsides, because at the speeds they go, aero drag needs to be dealt with. As for the chine features, you will do well to design in an effort to keep the water under the boat. That is to say that a lot of spray climbing the sides will slow the boat enough to matter in competition.
     
  13. aaronhl
    Joined: Aug 2012
    Posts: 194
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Central Connecticut

    aaronhl Senior Member

    Yea thats exactly what we race- all zenoahs...rc boat racing is very popular in FL, I actually have many customers there, specificaly in Bartow...do you race?

    I agree as far as deadrise, I dont want to design a deep v so if its shallow what types of features would improve rough water handling? A flat sleek top is a great mention too

    So that brings me to a reverse chine towards the transom end. Do you think that would help? I see few gas rc boats with them
     
  14. messabout
    Joined: Jan 2006
    Posts: 2,985
    Likes: 191, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Not sure what you mean by "reverse chine" Are you referring to narrow, diagonally placed fins at the intersection of the bottom and the sides? If so, that feature would, perhaps, augment dynamic lift in the afterplane and also help keep the spray down. But there is a downside. The fins can cause the boat to hook in a turn and cause a crowd pleasing, spectacular, rolling flip. The boat needs to be fast but it also needs to turn reliably, without surprises.

    If you look at some of the APBA hydros or racing runabouts you can see chines with a configuration called non trips. The chine area has small bevels. The bottom often extends slightly below the bevel intersection by the thickness of the ply bottom. In some cases a very low angle wedge is inserted into that area, thickest at the transom. Those used to be called "dutchmen". What they do is introduce a very slight hook in the afterplane that helps hold the nose down, hopefully to prevent or reduce the liklihood of blowovers.

    There are way to many matters to consider in designing a race boat. Flat out speed, turning ability, reasonably level running, diminished tendency to pogo or jump waves, little or no tendency to bury
    the bow, and more. All those requirements involve a ton of compromise.

    You could keep the forward sections very narrow and sharply veed. That would reduce aero bow lift and slamming. Fine. If overdone you lose too much forward bearing and then you risk plunging, bow bury, or even pitch pole. Too many variables.

    I suspect that you will need to do a bunch of experimental builds in order to arrive at the ideal for the water conditions that you normally expect.

    Post some sketches and we can disect the ideas.
     

  15. aaronhl
    Joined: Aug 2012
    Posts: 194
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Central Connecticut

    aaronhl Senior Member

    You have shared some great thoughts so far. This is what I am referring to for reverse chine. If that isn't what you were referring to hooking in turns, then what would? You are right these boat turn sharp, it's what they do for 80% of the race.

    [​IMG]

    Do you have a picture of the "dutchmen" example? I think I know what you are talking about. I made a non trip on hydro sponsons. A picture might show the size a little better and the exact placement. Could you have a reverse chine with a bevel (non trip) wider towards the transom to help with spray and stable turning? I liked the design of this APBA mono I saw yesterday. It has a pad, shallow V, and extended chine to transom. The short sides and flat deck seems like it would help with aerodynamics.

    [​IMG]

    I realize I am asking for help designing the perfect hull (fast and stable). I have no experience designing a mono hull, and no computer software to do so. I want to attack the build with a particular plan so sketches are probably a good way to start.
     
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.