Hull Reinforcement Methods

Discussion in 'Boat Design' started by Waverunner Eagl, Jun 18, 2016.

  1. Waverunner Eagl
    Joined: Dec 2012
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: California

    Waverunner Eagl Junior Member

    Hello,

    I have an old stand up jet ski project I'm working on that has a set of braces on the side of the hull. I think the ones I have are mostly visual, rather than functional. My question is - what is a stronger way to attach an aluminum brace to a fiberglass hull?

    Currently the brace is held on with 6 #10 fasteners, on the back side, each fastener has a standard washer and a locknut. Other variations I have considered are the 6 #10 fasteners, but with a backing plate to sandwich the hull. What about using an epoxy to bind the brace to the hull? Another thought was to use a larger number of smaller fasteners - probably rivets.

    I have a basic engineering education, but little practical experience. I'm planning to construct a new set of braces, so any input would be greatly appreciated.


    Thank you

    [​IMG]
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 476, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Those trapezoidal aluminum pieces are decorative in nature, so anything will do. I'd just bond them on and skip the potential leak points altogether. Epoxy would be the choice and look up how to prep aluminum for bonding at westsystem.com. If you prefer a hard fastener, consider a "nutsert" which is a rivet with a machine thread, instead of a hollow shank.
     
  3. Waverunner Eagl
    Joined: Dec 2012
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: California

    Waverunner Eagl Junior Member

    Thank you for the reply, and for confirming my thoughts.

    The nutserts are a great idea, I am heading towards an interference problem between the nuts that hold on the "brace" and the rather large exhaust I am using and I think they might solve my problem.

    This ski also has a brace around the nose of the ski. The area under the small trapezoid in front is very prone to cracking. I think the best solution is to reinforce the area from the inside with more glass. However, let's say for whatever reason I couldn't glass the inside, how would you recommend reinforcing the area with an aluminum plate? Or am I completely barking up the wrong tree?
     
  4. Waverunner Eagl
    Joined: Dec 2012
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: California

    Waverunner Eagl Junior Member

    I'm just going to bump this up to the top to see if anyone else has any input

    Thanks all
     
  5. upchurchmr
    Joined: Feb 2011
    Posts: 3,053
    Likes: 150, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Perhaps a picture of the nose "brace" would help.
    If you already have an aluminum brace that the glass cracks under, why would you want to try that again?
    Where are the cracks - on other boats I assume.
     
  6. Waverunner Eagl
    Joined: Dec 2012
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: California

    Waverunner Eagl Junior Member

    It's the small piece near the front of the ski with the three bolts on the first picture.
    It's impossible to determine if the ski cracked before or after the brace was installed, most likely it was before the brace.
     

  7. upchurchmr
    Joined: Feb 2011
    Posts: 3,053
    Likes: 150, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    All I see is a piece of aluminum with about 20 fasteners that goes side to side.
    Is that what you are talking about?
    is the crack only under the piece on the side right where the cowling opening heads upward?

    Where does the crack go? Between fasteners, vertically, horizontally or otherwise.

    General rule of thumb is that if you want to return the strength, you have to add the same amount of material.
    If you want it to not crack again you need to add some more.
    That is if you add glass.
     
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.