Maximum Transom and deadrise angle?

Discussion in 'Boat Design' started by jimianbu, Aug 23, 2010.

  1. jimianbu
    Joined: Jun 2009
    Posts: 33
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: Manjung, Perak, Malaysia

    jimianbu Junior Member

    I'm designing a car-topper boat, so is there a regulation for transom and deadrise angle? What is the minimum and maximum angle (range) for transom and deadrise for such type of boat? Need help on this. TQ.
     
  2. Willallison
    Joined: Oct 2001
    Posts: 3,590
    Likes: 130, Points: 0, Legacy Rep: 2369
    Location: Australia

    Willallison Senior Member

    Well, if your planning on putting an outboard on it, the transom should be at around 12 degrees (sloping backwards!;) )
    Beyond that, there are not really any 'regulations'... it would normally be a function of ensuring that the panels are developbale (only bent in one direction) so they can easily be made from plywood
     
  3. gonzo
    Joined: Aug 2002
    Posts: 13,609
    Likes: 382, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    12-14 degrees is the standard for ourboards. Deadrise depends on the overall design.
     
  4. jimianbu
    Joined: Jun 2009
    Posts: 33
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: Manjung, Perak, Malaysia

    jimianbu Junior Member

    Thanks for quick reply Willallison and Gonzo. Now I understand about the transom angle. But, for deadrise angle, can you please give me a specific value for the range of the angle? I need in numbers. Sorry for the inconvenience. And Gonzo, what do you mean by depends on the overall design?
     
  5. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    0-24. it depends on what the kind of boat it is .
     
  6. lewisboats
    Joined: Oct 2002
    Posts: 2,329
    Likes: 126, Points: 0, Legacy Rep: 1603
    Location: Iowa

    lewisboats Obsessed Member

    What Frank said...along with the generality of the smaller the boat the shallower the deadrise. It goes to stability. Too much deadrise in a small boat makes it tippy without a heavy keel or some such usually related to sailboats. Flat is generally considered 0-3 deg...4-10 shallow 11-18 medium and over 18 gets toward the deep with over 22 being considered deep. These are general numbers that I have come across but I have no links or cites to give you to back that up. I think though that these fall within most peoples definitions. The deeper the Vee the more power it takes to come up on plane, the slower the top end is in relation to horsepower but the smoother the ride and the rougher the water the boat can handle. An example is a typical Ranger Bass boat...shallow vee, wide and low. It likes smooth water, skinny water and runs like a ***** ape but would be a hand full or even unsafe in the higher waves of say...Lake Superior out in the deeper stuff. On the other hand are the Lunds designed for Great Lakes Walleye fishing are deeper, not quite so wide for length and not as fast with the same horses but can handle much more troublesome water with aplomb.


    Transom angle is as said 12-15 degrees raked back. The motor is usually measured vertically though so that is how you want to derive your height. From the Plate to the part which rests on the transom itself is from 15" to 35" (uncommon) but the usual suspects are the first 3...15", 20" and 25". The plate should be within an inch of the lowest point of the transom with it better to be more in the water than less...generally. For real shallow running you might go the higher route but you run the risk of Aeration (NOT Cavitation...different animal all together) and a bit of reduced speed...especially when running in choppy or wake disturbed waters.
     
  7. terhohalme
    Joined: Jun 2003
    Posts: 512
    Likes: 37, Points: 28, Legacy Rep: 506
    Location: Kotka, Finland

    terhohalme BEng Boat Technology

    Where are you going to use your car topper? Channels, small rivers, bonds, lakes, coastal, offshore? And what speed? How many people? How big engine? Will you build or buy it?
     
  8. gonzo
    Joined: Aug 2002
    Posts: 13,609
    Likes: 382, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Deadrise is only one of the characteristics of a design. It has to be considered in relation with all others. There is no definite answer.
     
  9. jimianbu
    Joined: Jun 2009
    Posts: 33
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: Manjung, Perak, Malaysia

    jimianbu Junior Member

    Lewisboats: Thanks for an outstanding explanation. Really appreciate that.

    terhohalme: Yes, I'm going to build it. Here's the design specification of the DIY boat;
    1. Car-topper (LOA, Beam, Depth and Draft to be suggested)
    2. No. of passengger: 2-3
    3. Outboard engine: 5-15hp
    4. Speed: (Need suggestion please)
    5. Construction: Marine Plywood Stitch and Glue Method
    6. Usage: River/Estuary
     

  10. lewisboats
    Joined: Oct 2002
    Posts: 2,329
    Likes: 126, Points: 0, Legacy Rep: 1603
    Location: Iowa

    lewisboats Obsessed Member

    http://www.angelfire.com/ego/lewisboatworks/html/fishbuildnav_a.htm

    fits everything but maybe the width...it is a bit beamy to comfortably cartop. However...if you design the rack properly...not much of a problem.

    [​IMG]

    Vital Statistics

    Length: 10 feet

    Max Beam: 54.75 inches

    Beam at chine: 45.5 inches.

    Boat weight: 75lbs.

    Payload: 475 lbs or 3 adults + gear.

    Freeboard: 10 inches.

    Motor Capacity: 15 hp (9.9 recommended)

    Speed with 1 200 pounder and a 9.5 hp Johnson...23 mph clocked.
     
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.