Angle on sides of jon boat

Discussion in 'Boat Design' started by msaxton, Apr 1, 2016.

  1. msaxton
    Joined: Jan 2014
    Posts: 57
    Likes: 3, Points: 0, Legacy Rep: 30
    Location: Duluth Minnesota

    msaxton Junior Member

    Looking for opinions, what is the best angle to have on the sides of a flat bottom jon boat and why?
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There's no best angle. The sides can be plumb, though this makes the ride wetter, it is easier for some to build. The sides could be quite dramatically angled, which can be a little harder to build, but it'll be drier and will offer greatly increased volume improvements, as the boat's PPI goes up with loading.

    More importantly than the angle, is how much twist the side panels have, at least in terms of building ease. Maintaining a consistent angle makes the boat easy to plank. Making the angle vary (twist) can offer more deck space and to most is a lot prettier.

    Maybe it would be best to tell us what you're doing, as this question is so basic in nature, it makes me wonder about having sufficient skills to design (and engineer), even something seemingly as innocuous as a jon boat.
     
  3. Barry
    Joined: Mar 2002
    Posts: 1,222
    Likes: 119, Points: 63, Legacy Rep: 158

    Barry Senior Member

    If your width is fixed due to towing restrictions, the more vertical the sides, the wider the chine width will be which helps in planning, packing weight etc.
    You can easily google Jon boats, pick up a few manufacturers websites and some will have a stern view. Print the picture, put a protractor on it and away you go.
    As Par said, some angle will give you a drier ride.
    Remember the more off vertical the side angle, for a given width, the chine width will narrow, reducing planing or weight carrying capacity
     
  4. msaxton
    Joined: Jan 2014
    Posts: 57
    Likes: 3, Points: 0, Legacy Rep: 30
    Location: Duluth Minnesota

    msaxton Junior Member

    Umm, wow, have built several small boats, I was simply asking opinions because I see different plans with different angles, But thanks for being condescending. And yes, I am building a simple jon boat, sorry to start such a simple conversation amongst pros!
     
    1 person likes this.
  5. troy2000
    Joined: Nov 2009
    Posts: 1,743
    Likes: 170, Points: 63, Legacy Rep: 2078
    Location: California

    troy2000 Senior Member

    He wasn't being condescending; he was asking pertinent questions and pointing out that your question was basically a clueless one. Face it: if there were an all-inclusive 'best' angle, every jon boat out there would incorporate it.

    The most reasonable answer to your question is another question: "best angle for what?" Maximum load capacity, driest ride, ease of building, most attractive... every boat plan is a compromise, that reconciles conflicting parameters.
     
  6. Barry
    Joined: Mar 2002
    Posts: 1,222
    Likes: 119, Points: 63, Legacy Rep: 158

    Barry Senior Member

    Crestliner and Tracker give the specs for many of their boats and I expect that others do as well

    Here is the formula that will give you the tools to perhaps look at the boat on the net, pick out some of the numbers from the spec sheet and calculate the angle off vertical that the sides make with the horizontal.

    Width of the boat at the transom minus the chine width. Divide this by 2 and call this number A

    Find the depth of the boat from the spec sheet, inside height, call this number B

    A divided by B will give you a number, call it C

    Go to the net and find a tangent table, and match your number C to the table, it will have a corresponding angle. And you are set to go
    Crestliner and Tracker seemed to run between 30 to 37 degrees off the vertical

    Personally I would have ran around 20 to 25 degrees and increased the chine width for better planing and weight carrying capacity
     
    1 person likes this.
  7. msaxton
    Joined: Jan 2014
    Posts: 57
    Likes: 3, Points: 0, Legacy Rep: 30
    Location: Duluth Minnesota

    msaxton Junior Member

    It was not a "clueless" question, Im trying to decide what angle to make mine, I know what I like as far as looks, but was just seeking to get opinions from others on what they like pertaining to the things you mentioned, load, dry, ease of building. Though, ease of building doesn't matter much as the angles don't scare me. I guess I should have clarified my question better.
     
  8. gonzo
    Joined: Aug 2002
    Posts: 13,953
    Likes: 486, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The range of angles is huge. The purpose of the boat, and the operating conditions play a big part on the choice. However, there are also local preferences that are simply customary. For example, if you are planning on spearfishing, a larger angle allows you to lean over and reach further than on a slab sided boat. However, if you want maximum initial stability for the beam, slab sides are better.
     
  9. troy2000
    Joined: Nov 2009
    Posts: 1,743
    Likes: 170, Points: 63, Legacy Rep: 2078
    Location: California

    troy2000 Senior Member

    And I could definitely have been more diplomatic in my response. My bad. :)

    Don't mistake PAR's bluntness and lack of obfuscating pretty language for condescension... he's willing to go out of his way to explain and inform, and is one of the best resources for amateur builders I've run into online. I've learned a lot from him - and he also happens to design boats with a nice blend of looks and practicality.
     
  10. messabout
    Joined: Jan 2006
    Posts: 3,016
    Likes: 210, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    As stated above in different words; form follows function.

    You will get more detailed advice if you will post a SOR (statement of requirements) which is to establish the intended use of the boat and the conditions in which it is to operate, the size of the intended engine, the anticipated load it is to carry, the speed that you wish to achieve, whether you will need to move around in the boat to play a fish, will you use an elevated swivel seat?, and a few more things that ultimately dictate the design features of the boat.

    Almost none of that is much concerned with the flare angle. It is somewhat incorrectly assumed that flare is necessary to increase the roll resistance of the boat. It does help but not as much as one might imagine without doing the actual math. Most observers tend to believe that a boat must have some flare, so if you ever intend to sell the boat then make it look like what the buyer perceives to be necessary. On average Jon boats often have something on the order of 14 degrees which is roughly a bevel of one on four. That is about the same angle that the transom should have in order to accommodate the motor.

    None of your replies have any intention of a condescending nature. This forum has thousands of members and many of them are very knowledgeable as well as admirably generous. Please do not take some of the straight talk as an affront to your intelligence.
     
  11. TANSL
    Joined: Sep 2011
    Posts: 5,926
    Likes: 239, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Often people do not want a lecture but a simple answer.

    If we mean by "initial stability," the value of the initial GMt, it does not depend on the angle of sides, but the waterline inertia at the time, and some other things. So, msaxthon, you need not worry, for now, the "initial stability"
     
  12. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I don't think anyone has been condescending, though possibly too direct. Often topside planking angles on flat bottom boats, are more related to bottom panel widths. A dory would be a typical example, where it's relatively narrow bottom panel offers little elbow room, so the sides are angled outboard more, to provide additional internal volume. Another example might be tumblehome, to permit a fisherman to get right up to a rail and handle a net or something, without his feet bashing into the topside planking.
     
  13. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,172
    Likes: 397, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Simple example, if I place my weight on the gunwale of a 6' wide flat-bottom boat that is 4' wide at the waterline, I will notice more heel than if the waterline is 5', all else being similar. Which is what gonzo is talking about.
     
  14. Alumination
    Joined: Oct 2013
    Posts: 84
    Likes: 2, Points: 0, Legacy Rep: -7
    Location: Knoxville, Tennessee

    Alumination Junior Member

    Sure he was! This is how he likes to break the ice.

    Don't let any negative comments deter you from finding the information you are seeking. There will probably be someone along shortly who has studied and experimented with this exact dimension and found a narrow range where the most benefit is.

    Thank you for being the bigger person and lending a helpful hand.

    True, this Forum is a plethora of information. Extracting it is the difficult part sometimes.

    It's my understanding that the angle of the sides is not simply done for looks, the right angle can keep passengers dry as well as giving them more room where they need it.
     
    SamSam likes this.

  15. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Bite me Alumination. I wasn't trying to be anything more than observant of the questions, offer some consideration to his questions and reasonable speculation that someone asking about topside angles, very well might be a wee bit lax of the fundamentals, which clearly is the case.

    As I pointed out in my post and you've partly reinforced, there can be several reasons any particular design might elect a specific angle, but if you're asking if there's a "best" angle, the obvious return question seems reasonable.
     
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.