planning boat, hook or hollow

Discussion in 'Projects & Proposals' started by gtflash, Oct 28, 2011.

  1. gtflash
    Joined: Jun 2006
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    Location: uk

    gtflash Senior Member

    Hello

    I have a fast planning boat hull, she was damaged years ago when hit a submerged object, but repaired. I noticed she leans to port, and took a straight edge to underside. Sure enough approx 2m from bow, on port side is a dip in the hull, inwards of about 5-10mm, also the spray rail goes up, and hollows out.. The etire area, is about 2ft long, and is the opposite shaped to a banana. one one planning area of 2ft x 10" and including the one spray rail.

    I have had it suggested I lift deck up and un pin stringers, then jack the hole outward, and then fix in place, and It has also been said to just fill the outside flat.

    Can anyone help, or make valid suggestions. It is a open boat with moulded deck, but I do need to do minor stringer repairs inside hull also, due to an old ballast tank being damaged and needing removal, for space.

    Thanks
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    A hollow will decrease lift and make the boat lean. You can fill a small hollow with light weight epoxy filler and then refinish. Taking the boat apart is a major job and may cause extra damage.
     
  3. tunnels

    tunnels Previous Member

    Sound like you need to flip the hull upside down and do a major fairing job to get the hull straight again . Check aso how the hull sits on the trailer as if there a hollow a roller could be the problem pushing a hollow !Even the slightest bump or hollow will have a dramatic effect on performance specially at speed . Hook is when the hull goes up along the keel line Hollow !!
    Rocker is when the keel has a hump down this can does and will cause porposing depending on how bad and where the main part of the hump is . Playing with Hook and rocker you can completely change the handleing of the boat . Some boats love a little hook to get up and fly aross the water .
    Rocker can do a simular thing but will make a hull turn very quickly even to the point of flipping over if you dome antisapate what can happen and not prepaired for it . The positioning of the high part of the rocker is the key to getting the effect you are looking for . so straight is ok but !!:p
     
  4. gonzo
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    gonzo Senior Member

    There is a difference between hook and hollow. A hook will lift the stern. The buttocks are straight almost to the stern and then curve down. A hollow will make the boat squat. The buttock is straight from the stern forward, but there is an area where is curves in.
     
  5. Bobthebuilder06
    Joined: Oct 2011
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    Bobthebuilder06 New Member

    Thanks for feedback. I have taken alot of references and it appears the 1st spray rail goes up but is square left to right. The planning surfaces each side of that spray rail are also concaved but straight by the time they reach the next datum, one being the keel of the deep v, the other being the next spray rail. The entire surface area concaved is about 10-12" x 18". I am relieved the spray rail appears straight jut concaved. It does have an ill fitting new trailer. But it takes all its weight on the keel rollers instead of the bunks.

    I tend to use west systems epoxy, what filler additive would be most suited to fill and fair the area. Max depth of concave is 1/2" if that much, trying to convert from mm to inch in head :)
     
  6. gonzo
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    gonzo Senior Member

    I use microfibers and silica mixed to fill the bulk of it. You can use microballons or other lightweight filler for final fairing.
     
  7. gtflash
    Joined: Jun 2006
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    gtflash Senior Member

    thankyou. I will follow your advise. I have read conflicting info on gelcoat over Epoxy. I had hoped to spray or paint gel on after, then mix some with a thinner (what type) and overcoat a larger area to help grade into existing hull. Is this OK?
     
  8. gonzo
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    gonzo Senior Member

    I have heard a lot about gelcoat over epoxy too. As an experiment I repaired a boat with epoxy and then gelcoated over. I first made sure the amine wax was all removed. Even below the waterline the gelcoat has stayed on.
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You can use a bonding promoter to get the gel coat to stick, but knowing how difficult it is for a novice to do gel coat, you should strongly consider painting.
     
  10. tunnels

    tunnels Previous Member

    Having worked in the glassing industry for 30 years polyester over epoxy i would advise never think about gel coating . Ok sometimes it has worked but there always the possablilty it wont and i would never advise anyone to do it . Two pot urethane paint yes ok everytime !! Gell coat no !!:D
     
  11. gonzo
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    gonzo Senior Member

    I experimented in my own boat and it has worked OK. It has only been a year though.
     
  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I agree with Tunnels, Gonzo. You have a much better understanding of how things work and would likely fair better then the average guy attempting to spray gel coat in his driveway, next to his wife's Mercedes. I've never seen a driveway job turn out very good.
     
  13. tunnels

    tunnels Previous Member

    I cant believe this thread is still rambling on fron hook and hollow to epoxy , gelcoat over the top ! Most urethanes are harder than gel coat anyway so what are you worried about ?? Gel coat scratchs and get damaged easyer than urethane ,gel coat is brittle and like a egg shell . Its not the be all to end all . GET ON WITH IT !!!:(
     
  14. Bobthebuilder06
    Joined: Oct 2011
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    Bobthebuilder06 New Member

    Alright alright. Calm down. Appreciate all the advise, apologies for the rambling. I mistook this for a public forum. I haven't got on with it yet, due to working away, and living in the rainiest country in the world (as it seems). I wi update when done, all materials sourced with the exception of paint.
     

  15. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Nothing to apologize for, it is a public forum and some of us, (myself well noted) have considerable verbosity to utilize, often off topic. Speaking of which, yes, the UK is the rainiest place on the face of the earth, in spite the jungles of South America. I've been there twice, spend a total of a few weeks and I don't think the sun appeared once or if it did it was so fleeting that I missed it . . . :rolleyes:
     
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