Bench Seat Removal

Discussion in 'Boat Modification Journal' started by wcgordy, May 2, 2008.

  1. wcgordy

    wcgordy New Member

    Messages:
    16
    State:
    Texas
    Any body ever removed a bench seat from a jonboat. I have a 12' v-hull I am currently working on. I would like to drill the rivets on the middle bench and remove it. Don't know if this will weaken the ridgity of the hull or not. Would eventually like to build a floor, but that seat is in the way. Any tips would be appreciated.:big_smile:
     
  2. peewee williams

    peewee williams New Member

    Messages:
    3,111
    State:
    Pembroke,Georgia
    I am almost 63.I have been around the water and small boats all of my life.I have owned and preferred Aluminum boats,but have owned wood,glass and plastic also.

    This is part of the design and strength of the hull.The removal can cause flexing,rivet popping,weld cracking and hull metal cracking.It can cause this in the immediate side or floor area or some remote location that you never thought of.I got all of this from seeing it happen to others.I would try to build my floor on either side or else reinforce my boat in every way to equal or exceed the strength of what you had in the exact area with the seat installed correctly.Even adding a rigid floor can excessively stress your hull in other areas at times.Even laying thick plywood or aluminum heavy tread plate can keep your hull as a whole from flexing correctly under a stressful situation and fail.Many,including I have gotten away with this where others ruined their boat.I used the thinest and most flexible plywood I could get away with and sprinkled sand on the wet paint for anti skid.I left the seat and just kept stepping over it.I have seen it done both ways.

    Great Big factor.I have always run lower HP motors that were well within and under the recommended MAX.HP.!My boats were well under the designed stress limits at all times.This is everything with hull stress.

    Remember.Is the seat part of your flotation?Also.Are you BREAKING THE LAW?Check it out.You may well be if you modify your hull in some states.

    All of your insurance is usually Null and VOID if you have a accident,including your liability with the altered boat!Check it out with your agent."Any lie to them voids your policy".Lay a sheet of plywood in the bottom of a boat and it does not affect any insurance that I know of.It is also far easier to lift out and clean under!

    Open Johns with or without floors are designed and built with all of this in mind.Most are built with more ribs,heavier ribs or both.Often with thicker hulls with stronger alloys.Also and very important!If you do this,you will be far safer running a very small minimum horsepower motor to keep from stressing the hull with any excessive flexing or pounding at all if possible.If you run a planing motor you are subject to "Catastrophic" and "Sudden" failure instead of slow cracking and splitting.

    As I said,"I saw it".I saw it done and the results about a dozen times in my 50+ years on the water.This is totally from experience as I am not a Marine Engineer.I have also heard of problems with this.

    You are doing great by learning all that you can ahead of time.The design and strength of your hull plus the way you will use it is everything here.The unsupported sides of a hull will be attempting to collapse inward more and more as load or wave hight increases.This is when you need the proper strength the most.

    Do you know where your hull was made to flex?If so,how much?Do you know where your hull was made to be rigid?

    Now you can easily find someone who claims to know all of these questions and answers or who will tell you that you can ignore them.Every single case of failure that I know of followed such advice and thinking.

    I love you Brothers and Sisters.peewee.
     

  3. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    You dont have to remove a seat in a jon boat for the aluminum to crack.
    I own one that is cracked and it doesnt use outboard power and no seat has been removed.:wink:

    Seen em cracked in some odd places because of altering or overpowering.

    It would be more economical to buy a used boat that is something like you are looking for rather then making a boat into something it isn't meant to be.

    An outboard puts alot of lateral forces on a hull. The entire bottom of a planing hull takes a alot of force just from the engine. You haven't even got in the transom and sidewalls yet.
     
  4. wcgordy

    wcgordy New Member

    Messages:
    16
    State:
    Texas
    Thanks for the advice. The seat in question is attached to a handle on the side of the hull (12 or so rivets). It does not attach to the boat in the floor or anywhere else that I can see. It has two other seats attached the same way. All 3 seats have an airfilled? box attached for floatation. This is an old 50-60 model Lone Star. I do not know about flex in the hull. It has just an 2.5 horse Mercury outboard, probably should not stress too much.
     
  5. PeeDee Cat

    PeeDee Cat Member

    Messages:
    351
    State:
    SC
    I HAVE REMOVED SEVERAL BENCH SEATS FORM JON BOATS WHAT I DID WAS TIG WELD THE RIVET HOLES AND FABRICATE SUPPORT BRACES TO REPLACE THE SEATS. I TOOK 1/8" ALUM. AND FABRICATED THE BRACES AND WELDED THEM IN PLACE SOME OF THESE WERE FORMED CHANNELS AND FORMED HALF MOON SHAPE. THE BRACES WERE THEN WELDED IN PLACE FOR STRUCTUAL SUPPORT. HAVE NOT HAD ANY COMPLAINTS YET. SOME HAVE BEEN DONE FOR NUMEROUS YEARS. IT PROBABLY WILL COST MORE THAN WHAT IT IS WORTH TO HAVE THIS DONE AT A SHEETMETAL OR FABRICATING SHOP. IT JUST DEPENDS ON HOW MUCH MONEY U WANT TO SPEND. jUST THOUGHT I WOULD THROW THIS OUT TO U.
    PEEDEE CAT
     
  6. peewee williams

    peewee williams New Member

    Messages:
    3,111
    State:
    Pembroke,Georgia
    Something else to consider.Few boats other than some of the expensive Grumman's were made of Aircraft grades of Aluminum alloys.The heating and cooling from the Earths temperature changes alone can change the temper of some Aluminum or any metal to some extent.Just check out any old house that has old copper tubing for gas or fuel oil lines.It gets HARD and BRITTLE over many years.

    I love you Brothers and Sisters.peewee
     
  7. kevhead56

    kevhead56 New Member

    Messages:
    62
    State:
    Greenfield, Il
    A totally welded boat might be OK to remove a seat but the riveted ones need the extra support and strength that the seat gives. Be very careful in making the decision to remove a seat.