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Thread: How much deadrise is too much

  1. #1
    Member akrstabout's Avatar
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    Default How much deadrise is too much

    I know of a boat being built that has 28* deadrise. Which for rough water days in the fall and even in the summer would be nice. At what point do you lose effiency in a steep deadrise. Not sure what the bow is, have not seen the boat yet but will sometime soon. It is 28* at the transome. I think I would like my next boat in the area of 20 23* deadrise at the transome and 50ish at the bow. Just wondering also with the increased surface area about how much more horse power would it take on the 28*. The boat is 27' and does not include the extended transome I believe. All aluminum too. Any ideas or input?

  2. #2

    Default Need more info...

    Since everything in boat design is a compromise, deadrise has to be looked at in the context of the entire hull. Are there planes or cylindrical or spiral curves as you approach the chines?

    Does the hull design software indicate an "undevelopable" surface (one that will tend to porpoise)?

    Also, deadrise affects the comfort of a boat at anchor. A tippy boat that moves with every wavelet isn't nearly as nice to sleep in or fish from as one that sits flatter when still. But a little deadrise in the stern keeps an aluminum boat quieter in the same conditions.

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    Member jrogers's Avatar
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    Default 28 degrees seems like a lot

    I was just doing a bit of checking.

    Seawolf is 14 degrees
    Coldwater is 19 degrees
    Coastal craft is 16 degrees
    Seasport Voyager is 22 degrees

    The first three are aluminum. I would like to learn more about this. I suspect that hull design is much more than one number. I had a builder tell me once that it is all a compromise to make a boat work well in all of the different sea conditions and there are a lot of variables.

    Jim

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    Member akrstabout's Avatar
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    Default as far as I know

    there is no hull software he uses. I have not seen the boat yet so don't know about the bottom or chines. Not sure how wide the bottom is or the deck space once floor is in. I know it has a pilot house and a huge V-birth. Once the cabin is roofed and such he said he will call me up for a looksie. He will be selling once it complete.

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    Member captaindd's Avatar
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    Default Dead Rise

    Most aluminum boats have an 18 degrees or greater at the transom. Once your boat gets on plane you have to have a good V in order to cut the chop or your boat will pound. Back in 1993 I had a boat built in Anchorage by Marian Boat works. I requested that the boat have an 18 Degree angle at the transom as I had read an article about a 30 ft Almar in a boating mag that had outstanding performance. After I got the Marian I noticed that it sure pounded in chop but in flat water it could go up to 55Kts and had cruise of 34Kts. In 1997 I change the engines out to Volvo Diesels and ended up building the stands for the motor mounts my self. I put a guage on the hull of the transom and it read ten degrees. Last year I purchased a New Cold Water with a 19 Degree Transom.The difference was like night. On 1 July I drove the Cold Water boat and one of my friends drove the Marian Boat so I got to see what they would do in the same water conditions. We crossed Prince William Sound and the sea's where running 3 to 4 feet out of the South East. I was cruising at 26 Knots and drinking coffee. My friend in the Marian Boat was doing 12 Knots and getting beat up. I made several trips back to cut the waves for him. So dead rise is very important. Just a note on the 16 of June I broke three bones in my ankle and they put a steel rod in my leg and seven screws. I went back to work on the Cold Water boat and did 69 more charters. I could not of do that on my old boat. If you are going to buy a boat that is made out of aluminum find someone who has got one and get all the information that you can on it. One of the best boats that I have seen built in Alaska is the Bay Weld in Home. Good luck

  6. #6
    Member Sobie2's Avatar
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    Default

    akrstabout,

    What company is this?

    The debate isn't really about efficency. A displacement vessel (one which does not get up on step) can be just as fast and more efficient that one which gets up on step. Glacier bay catamarans for example are this.

    On a monhull though you run up against stability at rest. If the deadrise is too much the boat will seem tippy. My friend with a 22 hewescraft searunner is a great case in point. He loves the way it rides through the chop but being the sea runner model it is a little narrow and very tippy at rest and when trolling.

    I think ACB boats and Stabicraft offer up to 22 degrees but have aluminum pontoons which come in contact with the water when not moving to add stability.

    The efficency is how much HP you need to get up on step and it will be just as efficient IF it can get up step... truly on step. When it does it will be fast and smooth riding.

    Sobie2

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  8. #8
    Member akrstabout's Avatar
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    Default Lifetime Boats

    is what he is called. On his personal boat he added the pontoon thing last year so when at rest greater bouyancy kicks in. Looks pretty good and slim, sleek design. Not sure what is the plan for this boat. I don't believe it will be a dispacement hull. He did say it is double hulled. He said a 200-250 hp will push it just fine.

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