engine compartment hatch

Discussion in 'Materials' started by andrew1, Apr 26, 2012.

  1. andrew1
    Joined: Apr 2012
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    Location: vancouver bc

    andrew1 Junior Member

    hi all :)
    im new in this forum and i need some advice.

    i have to rebuild the hatch.right now is saging so for sure the core is damage.
    this is bayliner victoria and the hatch is aprox 5' x 3' like on the picture(simular to my ).
    i can use 3/4 " plywood but it will be heavy,balsa will be lighter or ??
    im planning to cut off the fiberglass around the core then remove the core and cleaned.then i thought of taping of the holes ( from outside) which are in the hatch (after some screws and bolts ) then apply gelcoat ( in the inside ) then the mat with polyster resin then the core and start laminating.
    im hoping that the gel coat will fix the holes.
    what im worry is if the plywood will glue to the mat (the mat that will be lay after gel coat).maybe drill some 3/8 - 1/2 " holes in the plywood so the resin can go thrue the plywood to the mat
    any sugestions for how to do it without spending a lots of $$$ ?
    thank You :)
     

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    Last edited: Apr 28, 2012
  2. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    A 3x5 hatch is pretty big, you probably need the plywood in core for strength unless your willing to do some reinforcement beams withing hatch. If your hatch cover is in good shape, you can gut hatch core from the bottom and rebuild it from within so that outside of hatch is. Grind all the wood off leaving only fiberglass then glue new wood to fiberglass with epoxy.
     
  3. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    thank You.
    the cover is in good shape.
    when i use the epoxy then i will have to fill and paint the hatch from the top (outside).this will lead to sanding the hatch which is original (with groves and squares the anti slip) and will show to much difference from the rest of the cockpit in my opinion :)
     
  4. mydauphin
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    mydauphin Senior Member

    No, the whole operation is done from bottom.
     
  5. andrew1
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    andrew1 Junior Member

    i know but how can i refinish the top to original stage after epoxy (the hatch isn`t smooth )
    i know that the epoxy is the superior for wood.im not saying that i will use wood.maybe balsa will be better for this project then i can use gel coat and polyester.
    ppl will walk on the hatch
     
  6. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    You don't touch the top, the area where people walk. You epoxy a board under hatch, and cut out wood from the bottom, then you glue it back together, but you don't touch deck. Balsa is very weak and wont easily hold a persons weight across a 3 foot span. Did you already mess up the top of the hatch?
     
  7. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    no i did not yet start the project.
    it`s large hatch and i want to do it properly.
    i want to understand correctly :)
    what You sugest is :
    cut the fiberglass from the under the hatch
    remove the rooted core and clean with solvent
    put the cloth and epoxy resin (the epoxy doesn`t require a mat)
    put in the core
    etc....
    now from the top of the hatch:
    the resin will go thrue the top
    to refinish the top and paint i will have to sand about 1/16 of the top of the hatch and this will give me smooth top (not matching the rest of the cockpit).
    im, not sure if You got what im trying to say ( sorry for my english - im polish )
    to make this easier :
    if i repair this hatch with epoxy (the underside ) can i put gelcoat over epoxy (on the top -outside) to fill and finish the holes ?
    im i vancouver bc canada and there is just few places that supply fiberglass materials and they don`t have the special gel coat to use wth epoxy.only polyester gel
     
  8. andrew1
    Joined: Apr 2012
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    Location: vancouver bc

    andrew1 Junior Member

    one guy did like this and the another one like this.
    im concern if those projects what they did will hold 4 ppl on the hatch that big while fishing :)the hatch is taking almost all the cockpit area
     

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  9. tunnels

    tunnels Previous Member

    Basics of making a hatch !!

    Its what underneith thats the critical part and has little to do with whats on top !!
    Ply is not the answer and never will be !! you are wasting your time !!

    The thickness of your core is what makes it strong and will support weight !! its what you use that will keep it light but its the glass you use thats the deciding factor as to how strong it will be as well !!

    i have a dozen hatchs laying on the workshop floor in a row , each one is differant from the other , I was told the are all to weak and cant be used so i asked 4 guys to break any or all of the hatchs !!!!! oh sue they bend but with 4 guys jumping really hard over and over for 20 minutes the hatchs are still there in the same place and not one has even a tiny crack in it!!

    My choice is to use Core cell foam 30mm thick and cut to shape and bevel and round the edges so it fits neatly where the hatch will close properly and not touch any where . The bonding surface totally needs to be sanded and ground so you will get a good bond when you glass it right to the very edge
    The foam can be stuck down with a single 450 gram chopped strand matt cut to the same size as the core , place it where its meant to be and wet it well and then place the foam ontop and gently work the resin so it is 100% coming out round all the edges .
    Because the hatch is likely to have a hollow in the centre place it on a smooh flat surface and place a sheet of plastic over it and a piece of ply a couple of feet square and a really heavy weight on top !! Cut some small thin wedges and gently push them a small way under the edges all way round so the centre has a bend ever so slightly the other way instead of a hollow . only needs to be about 1 mm thats all .
    When its cured hard take the weight off and turn it over its could be flat or have a slight raised centre

    Clean it and sand any resin places and sand the glass that could have squeezed out from under the core !!


    Now What glass to use !!
    1x 450 Chopped strand matt to go over the core right out to the very edge where its turned up and up that edge , next a 800 gram double bias cloth to cover the core and go to the edge but not up the edge .
    lastly a single layer of 600 gram unidirectional matt running across the 3 foot width of the hatch!!!! this is important that its goes across not the length unimatt has normally a light csm on one side make sure the csm is uppermost and this need to go all the way out to the very edge of the hatch !!!important !!!!! finish off using peel ply nicely rolled smooth all the way out and up the edge !! yes you will need to cut the corners to make it fit and lay properly

    The 30mm foam is light and will make it strong and the unidirectional glass in conjunction to the double bias will give you ridged strength !!!

    Ideally you could do all this with a vac process !!, what i have discribed is hand lay up !!if you use polyester resin or vinylester resin ,when the hatch has cured it could have pulled flat again as it cures !!

    :D

    If you use wood in a floor hatch eventually it will get wet and go soft and spongy and get really heavy over time !!
    Foam is eayer to use than Balsa and will be lighter as Balsa will absorb quite a amount of resin . specially at 30mm thickness . Remember the thicker the core the more strong it will be so if you use 40mm with the same glass it will become totally ridged !!.
     
  10. andrew1
    Joined: Apr 2012
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    Location: vancouver bc

    andrew1 Junior Member

    that`s what i was looking for.
    THANK YOU VERY MUCH :)
    i have to do hand lay up
    what doYou yhink about coremat for this ?
     
  11. tunnels

    tunnels Previous Member

    Just one word on using core matt NO
    To gain ridged strength you need thickness !! so the thicker the core you use the better !!!!,
    But going hand in hand you also need good glass to use as well !!
    A triaxle glass just one layer would be suitable but its the uni glass running across from side to side that doing the bulk of the work for you in your case !!!.

    The words Core matt are a bit miss leading . Core matt is ok but theres not to many people including the sales people that pedel the stuff that realise
    Its meant to be for bulking up and giving thickness to a panel of any shape and not solely to be used as a core material at all .
    Core matt is quite often used in all the wrong situations !!
    Its complately useless where a panel has movment like the bottom of a hull as a good example !! The inner and outer skins want to move in oposte directions and the corematt cant stand that and shear and breakdown completely from end to end
    Its only Q CELLS impregnated into a glass material simular to tissue to displace resin so you use less !! so as a bulking material ok !!,
    Example of its place to be used if you want 7 mm thickness of glass panel then 5mm core matt with 1 mm of glass each side and there you have it !!quick simple and easy !!!! It has the advantage because theres a reduced amount of resin it becomes a core and so adds stiffness !!!but add movement and you have one disintergrated panel !!!
    The very thin core matt layers i see getting used as a anti fibre or core print barrier that works well but is also a layer tha alows the two skins either side to be parted easly as core matt by it very nature is weak in the shear mode !!.
    Wet out just core matt and let it harden . it breaks quite easy !! and if you hit it it will shatter like a egg shell . It has its uses like all things but think long and hard before you use it and what you are trying to do !!
    The best way i found to use it is at the same time as you are laying a panel wet the core matt and make sure its really wet then glass straight over the top and just carry on going !!. some where i read its impossible to over wet core matt !! That partly true but only if you put a layer of glass over the top and wet that out at the same time . Its soft when wet so dont try to roll it hard and make a mushy sloppy mess because its totally defeating the purpose of what it there for !! to build thickness !! There is a spec for thickness = number of grams of resin per sqr foot or mtr but i havent seen it for long long time !!.
    . :p:D:p
     
  12. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    As Dauphin said, don't touch the top. Tape up the bolt holes. Turn the hatch upside down, get out the old wood and glass, lightly grind the hatch with coarse grinder (36 grit or so) to expose a new fiberglass surface, then vacuum and clean with solvent. Laminate with resin (not gelcoat) as suggested by others. Lightly sand to remove lumps and sharp edges and then finish the underside with paint. (As far as I know, gelcoat only comes in polyester and polyester doesn't stick to epoxy)

    We always had a bunch of dead 12 volt batteries to use as weights for glueing the ply to the hatch. They are manageably heavy and usually have a carrying strap attached.

    You don't want to sand or do anything to the top of the hatch, or you will end up with more work than it takes to replace the rotten wood. When doing the bottom, put a little glass in the bolt holes or use some glass filled putty to fill them. Gelcoat fades/changes color over time and if you sand down the top and re-gelcoat it, you will probably fill in and lose the non-skid surface, and have a hard time matching the hatch color to the color of the rest of the deck. Even if you get it matched, the new gelcoat will change color at a different rate than the old gelcoat and after awhile they will not be the same.

    The best solution is to reuse the same hardware in the same place, so all you have to do is re-drill the holes and reattach. (BTW, it is most likely the hatch rotted because of those very holes drilled to attach the hardware, and will eventually do it again unless precautions are taken, which others can explain.)

    If you need to use different hardware that leaves old bolt holes exposed and visible because of plain resin, you can use a little bigger drill to shallowly drill a clean pocket, get a small jar of over the counter touch up gelcoat pre mixed to the model color of your boat (19?? Bayliner Victoria deck) and use that.

    If anyone ever notices anything amiss, quickly maneuver in front of them, point over yonder and say "What was that?". That is a universal fix-all.
     
  13. andrew1
    Joined: Apr 2012
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    Location: vancouver bc

    andrew1 Junior Member

    yeh the previous owner has bolted something to the hatch(maybe chairs) and that was the bigest mistake so i will make sure that those holes are cover.the hinges are not interfear with the core so it`s ok.If You see the picture of the hatch there is a bolt to open the hatch which is thru the core.maybe better to replace this with pull latch or laminate some sleeve.how much epoxy aprox do i have to buy to do the project ? if the hatch is made from polyester (what i read that it is probably with the balsa core )and i will go with epoxy will the epoxy laminating stick to this hatch.Before i start this thread i read a lot and everyone said will not.
    i called the suplier and he told me that i will have to buy full sheet of the foam core $320

    Thank You again :)

    i found this ste with helpfull information for me and others
    http://www.lbifiberglass.com/TECH/techresin.html
     

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  14. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    I hardly ever used epoxy, but the way it works is epoxy sticks to polyester but polyester won't stick to epoxy.

    If you use plywood correctly in the hatch you won't have any problems with rot for pretty much forever.

    A problem with a full size sheet of ply is to get it all bedded to the hatch without air pockets. If you use epoxy then supposedly you shouldn't use mat as the binder in mat won't be dissolved by epoxy. So it would best be bedded to the hatch in some sort of epoxy goop. 1/4" air holes spaced around the sheet as you mentioned in an earlier post will help an awful lot in bedding the ply to the hatch.
     

  15. andrew1
    Joined: Apr 2012
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    Location: vancouver bc

    andrew1 Junior Member

    Thank You again :)
    the foam core is to expensive so i will go with 3/4 plywood.
    if i understand corectly i will do :
    cut off the fiberglas from the core
    remove the core and perfectly clean
    lay down cloth and wet it out with epoxy
    while is still wet put the plywood ( the edges around wet with epoxy )
    wet the plywood with epoxy
    put the cloth
    wet the cloth
    put the cloth again in oposite direction
    put the rowing cloth
    no mat with epoxy
    put 1.5oz cloth again and wet out good
    after is dry light sanding and paint
    no mat with epoxy
    is this good ?
    i have 1 galon of epoxy resin plus hardener .is it enought
     
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