Bow angle of entry question

Discussion in 'Boat Design' started by Tom Maine, Mar 13, 2018.

  1. Tom Maine
    Joined: Mar 2018
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    Location: Maine

    Tom Maine New Member

    Hi,

    Looking to understand how much angle of entry is needed to cut through 2 foot seas. In terms of entry angle, where is the cut off line for a bow that will cut through 2 foot seas safely and a bow that will rise and fall with the wave?

    Looking at two used 2012 Sea Hunt Escape and Key West 18.5 foot boats to use on the inter coastal waterways in Maine. Both boats are dual console with a full windshield and a 150 HP Yamaha 4 stroke outboard. The other boat I am looking at is a 2018 Crownline 19 XS, a 19 foot dual console boat with a full windshield but with only has a 115 HP 4 stroke Mercury. It seems a little under powered to me.

    I am told the 50 degree entry angle of the Sea Hunt and Key West (I think) boats will handle 2 foot seas very well but the Crownline with a 37 degree entry angle will not do as well. I am also told a Sting Ray and similar lake boats tend to rise up in 2 foot seas and slam down. I don't know the typical entry angle of lake boats.

    Knowing the entry angle and bridge clearance of various boats would help but that info is hard to find. Any thoughts?
     
    Last edited: Mar 13, 2018
  2. jorgepease
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    jorgepease Senior Member

    Length will help you go faster ... at 19 foot, I think you will have to moderate your speed.

    I have a 22 foot flat bottom that I slow down and keep the bow up and it handles going into 2 foot seas pretty well but probably not as comfortably as those boats mentioned. On the plus side I can scoot along nicely when going with the seas, surfing is fun on a flat bottom!
     
  3. DCockey
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    DCockey Senior Member

  4. Tom Maine
    Joined: Mar 2018
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    Location: Maine

    Tom Maine New Member

    Thanks for the video on dead rise. I need to know what angle of entry or dead rise angle at the forward end of the water line on an 18 to 19 foot boat with a 150 HP outboard will tend to cut through 2 foot seas instead of rising with the wave and then come crashing down.

    I am told the deep V hull design of a 186 (18.5 feet) DC Sea Hunt Escape has an "angle of entry" or dead rise at the bow of 50 degrees or so. When facing the bow of the boat the sides have a very sharp angle from the gunnels to the keel or center line of the bow. See photo attached. What I need to know is how shallow a dead rise at the bow will still cut through the waves? 50 degrees works but how will 40 or 30 degrees dead rise at the bow handle 2 foot seas?

    Just found a front photo of the bow. This boat has a Carolina flair with dead rise of 55 at the bow, 21 mid ship and 16 at the stern. My guess is this boat will cut through 2 foot seas well.
    download (3).jpg
     

    Attached Files:

    Last edited: Mar 14, 2018
  5. Tom Maine
    Joined: Mar 2018
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    Location: Maine

    Tom Maine New Member

    Just found a front photo of the bow. This boat has a Carolina flair with dead rise of 55 at the bow, 21 mid ship and 16 at the stern. My guess is this boat will cut through 2 foot seas well.
     
    Last edited: Mar 14, 2018
  6. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Your question leads to 2 possible replies.

    1) 2 foot seas - cut through...in terms of slamming
    2) 2 foot seas...in terms of seakeeping

    In either case, 2 foot seas are small, except if the boat is small. .....in terms of 1 + 2, speed plays more of an important role in this behaviour.
    The angle of entry is defined by the type of boat you have anyway. A supertanker of 200,000 tonnes doing 10 knots will have a very different angle of entry to a 15foot 40knots RIB.

    Other than - nice to know -..what is your objective?
     
  7. Tom Maine
    Joined: Mar 2018
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    Location: Maine

    Tom Maine New Member

    Thanks everyone for your comments. I just found what I am looking for and am posting what I found to help others with the same question on seaworthiness.

    I discovered a comparison between a Tidewater and a Sea Hunt boat, both 21 feet long. What makes the Sea Hunt cut through rougher seas is an entry angle or dead rise of 55 degrees at the bow, 21 mid ship and 16 at the stern. The pronounced Carolina flair at the bow and the dead rise taper back to the mid ship, behind the driver and provides for a much dryer ride. The 16 degree dead rise at the stern provides a much more stable ride because the boat doesn't rock side to side as much if the transom dead rise were greater. The Sea Hunt also had much greater freeboard than the Tidewater.

    The Tidewater only had a 40 degree angle of entry or dead rise at the bow and a less pronounced flair, both of which didn't extend past the drivers seat. The Tidewater also didn't have as much freeboard as the Sea Hunt and tended to rock more than the Sea Hunt. As the owner said, the Tidewater was a great boat but just didn't handle rougher seas.

    The owner traded in his Tidewater for the Sea Hunt because he wanted to venture out about 5 miles off the coats and he found the Tidewater didn't work as well as the Sea Hunt in the rougher seas commonly found that far out to sea.

    Thanks. I hope this post helps others get their questions on entry angle and the ability to cut through rough seas answered.
     

  8. messabout
    Joined: Jan 2006
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    messabout Senior Member

    If the forefoot is in the water, which it often is, a 55 degree deadrise forward section is more likely to "root" than a flatter section. The slang expression "root' means that the boat will snap its bow one way or the other in response to quartering waves or wakes. That is a disconcerting characteristic. The flatter the section the more likely that the bow will pound. Also rather disconcerting.

    It is fair to say that adequate seamanship is as much a factor as the shape of forward sections.
     
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