Sliding in turns -PLANING HULLS

Discussion in 'Boat Design' started by eightwgt, Apr 18, 2006.

  1. SamSam
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    SamSam Senior Member

    Look at Carolina Skiffs. The more HP the boat is rated for the more they deal with side slip. Also look at different jon boats. B and C will help prevent grabbing but not side slip, in fact they may promote it. Sam
     
  2. eightwgt
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    eightwgt Junior Member

    I have seen Carolina Skiffs MANY times =) I have seen many small skiffs. I in fact build boats. I came on here and asked to question hopoing to get some other professional opinions on the re3ar end of a skiff as I am designing a new boat (16') for our line of boats. Considering some of the people known to frequent some of these forums thought Id see what I could hear.... anyway - I have seen about any skiff you could mention although I have not been on all of them =).

    I am leaning towards 'D' or a variation of it and C

    Thanks guys.....
     
  3. Ike
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    Ike Senior Member

    I am all too familiar with the Carolina Skiff and it's problems. In it's earlier years there were many problems with skidding and chine tripping. Then they modified the chine slightly and added two strakes on the bottom. They will still do funny things if you push them too hard but that can happen with any flat bottom boat. They don't have the kinds of problems they had when they first came on the market.

    You would be wise to avoid a "hard" chine for two reasons. One is the skidding and tripping problem. The other is that the Coast Guard has seperate formulas for calculating horsepower on a flat bottom hard chined boat, and other boats. You can put more horsepower on a boat that doesn't have a hard chine. They consider any curvature or angle to the chine, to not be a hard chine. C or D would be a good way to go. I would still put some small strakes on the bottom to give it some straight line directional stability. In other words, make it run in a straight line when on a plane, rather than skitter around or crab at a slight angle.
     
  4. Pipex
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    Pipex Ace

    Surfers...

    That pesky bunch of water enthusiasts have been using this for years. See Quick Release Rails by Hawaiian Island Creations. It was a "gimmick" then and is a "gimmick" now. There is no way of making a flat hull go round corners fast without sliding. Designers wont tell you this but even V hulls slide, thats the nature of water. There are only way of limiting the slide.
     
  5. FranklinRatliff

    FranklinRatliff Previous Member

    Sliding

    Maybe then I was right to suggest a skid fin if someone absolute positively wants to limit sliding.
     
  6. Pipex
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    Pipex Ace

    Yes you are entirely correct. However, I do appreciate that I am probably one of the younger generation of marine engineers. Although I have tradition in the fact I learned with my hands. Still where I am from theres thrusters, bonzers, twinnies and single fins. "Skid fin" seems an outdated term for the modern generation... A generation where we pride ourselves in our skill at slide slipping corners quickly!

    As we often see with trim tabs, see recent design issues facing the Viper jet boat trim it is difficult to achieve a firm palcement of a trim tab under such loading. Henceforth considered as the major problem associated with fitting a fin or fins to the bottom of a boat.

    Personally I like the Willis brothers idea of golf ball shaped indentations on the hull which create air pockets for which the hull to slide coupled with a deep single to double concave.

    This invention leads to another interesting development commonly known as the cathedral hull, and similarly "winged" powerboat which are all further developments of this idea.
     
  7. redfury
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    redfury Junior Member

    quite an interesting read here. Of course, it throws my curiousity into a twist... I'm curious as to what level of effect of "sliding" I'll feel with my Glastron Tri hull since the "tunnel" goes straight to the back of the boat...

    From what I'm reading here, it seems that this design would be superior for handling vs. a standard "v" hull configuration.

    Which begs the question then...why did they stop making "Tri" hulls?
     
  8. tom28571
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    tom28571 Senior Member


    Some degree of sliding at the stern is necessary or the boat would never turn at all. You could say the front end of your car "slides" in the same way.

    Multihulls generally slide less than monos and are more difficult to turn or maneuver because of it. The tri hull is in many forms but falls in between the true multi and mono in these respects. The craze for the deep V may have been a major factor in reducing the number of tri hulls being built. It's the marketplace factor. A deep V on a lake where chop and waves are limited is way overkill and very inefficient to boot. The tri is more stable than most monos and is also rougher riding in chop than a moderate to deep V.

    You don't need math to reach these conclusions. Just imagine what is happening when the boat is in motion.

    You rarely get one desirable attribute without giving up something else.
     
  9. Ike
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    Ike Senior Member

    WHy no tri's or what was also know as the cathedral hull. 2 things. Fashion and harsh ride. You still see a lot of them around though.
     
  10. redfury
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    redfury Junior Member

    Well, I'm happy with the "fashion" of my trihull, but then again, there are some really ugly trihulls out there. The ones that have the block front ends are the worst looking things out there.

    I'm quite happy with the design of my 74 Glastron V178 ( though I'm finding that it isn't the most well built boat out there for its age )
     
  11. eightwgt
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    eightwgt Junior Member

    Hey guys.....

    I wasnt talking about tri-hulls !

    Just a simple concept as my drawing shows.....

    Im not trying to stop it from sliding, just looking for ideas to make slight improvements - I have to keep the aft end flat for shallow draft....:D
     
  12. redfury
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    redfury Junior Member

    Sorry, didn't mean to change the subject!

    Contribution!

    What about using those planer boards on the back of some boats? Have the one on the inboard side of the turn dip down harder, like a surfboarder putting his hand out and dragging the water during a tight turn?
     
  13. eightwgt
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    eightwgt Junior Member

    No problem... it is easy to get off the subject and start discussions.... I know ! :)

    All I was looking for were ideas regarding the hulls chines near the transom - no attachments, tri hulls, etc...
     
  14. messabout
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    messabout Senior Member

    Take Tom's advice. Attach a pair of skids to the bottom of the boat. Even a pair of small ones will make a remarkable difference. Three quarters to one inch thick and perhaps an inch and a half wide. Put these on at about the quarter beam locations. That is to say about half way out from the centerline. Do not put them at or too near the chine. If you do the chance of tripping will increase. These runners can be simple wood strips bedded in compound, not epoxy, so that they can be easily replaced. The runners may actually make you boat a little faster. If you have way too much power on the boat you will just have to reduce throttle when turning unless you are into stunt work. Skidding is bad news, but flipping can be disasterous because you could end up with the boat on top of you. Been there, done that.

    The non trip chine is a standard feature of fast boats. They dont need to be very big, but bigger is usually better to prevent flipping. On the other hand if they are too big they will contribute to the skidding tendency. That feature will be difficult to install on an existing hull. Try the runners first.
     

  15. wdnboatbuilder
    Joined: Nov 2005
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    wdnboatbuilder Senior Member

    how about the simplist solution................. 3/4x3/4 keel rounded with a fillet. it will make your boat stick in a corner. also end the keel about 30" from transom.
     
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