engine compartment hatch

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

  1. tunnels

    tunnels Previous Member

    Yes the foam is exspensive as a whole sheet ! try a fibreglass company and tell them what you want 30mm thick and the size thay might have just what you want. not a whole big sheet !!:eek:

    Balsa could also be used as a second choice and just do everything the same as written !! 25 mm is ok but could be springy so add 2 unidirectional glass instead of one !!:(

    :D
     
  2. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    i never work with epoxy always poly.how much time do i have to lay down everything
     
  3. tunnels

    tunnels Previous Member

    what ever !!

    No mater what you are using it has to have bleed holes about every 80mm apart over the total panel !! if you use P matt not e matt the binder with epoxy is never a problem !!! E matt has emulsion binder and its like watered down pva glue sprayed on and put through a oven to eveporate the moisture thats why it absorbs moisture and has to be kept dry !! P matt is a powdered binder of fine resin crystals and is heated to make it melt and hold together !!! so moisture doesnot effect it plus p matt is fractionally stronger then ematt because of the wet out of the glass fibres is better !
    Mixing goop is not that good as it needs micro fibes in with the mix to help the unreinforced resin from cracking :confused:
    Rememeber this is under a lot of load and is bending inder the pressure .

    Funny we all have great ideas of what has to be done but when it comes to the crunch we always back away and take short cuts and a while later end up having to redo that same job over again !! :eek:
     
  4. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    exactly. that`s why if im not 100% confortable i ask ? before i start
    waste of $$ and bad job.
    i don`t understand the P and E on use :)
    i have the mini fibre and i was planning to use as thickener,that`s what You are talking about ?

    how much time do i have to lay everything,do i have to rush to go wet on wet ? - epoxy lets say at 15 C outside temperature
     
  5. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    i gotha Ya
    "E matt has emulsion binder and its like watered down pva glue sprayed on and put through a oven to eveporate the moisture thats why it absorbs moisture and has to be kept dry !! P matt is a powdered binder of fine resin crystals and is heated to make it melt and hold together !!! so moisture doesnot effect it plus p matt is fractionally stronger then ematt because of the wet out of the glass fibres is better !"

    "Ok differant between p matt and e matt is the binder used to hold it all together . E matt has a emussion type binder the breaks down when the resin soaks the matt , trouble being that if the resin goes off and gells to quickly then the dinder may not have had time to dissolve 100% so the glass is not wet out properly . This can be and is bad news as the first layer of glass behind the gelcoat even if you are using Vinylester resin as a barrier and is still more likely to get osmosis !!!
    P matt has a sprinkling of powdered resin as its made and then put through a oven that melts the powder and so binds the glass together . It does not have to dissolve in the resin and there for if you have a quick brew then it is far less likely to get Osmosis .
    P matt also wets out much quicker and better than e matt and in some situations of multi layers of csm it gives a slightly strong lay up "


    this is a suplier in my area
    http://www.fibertek.ca/materials.htm.

    my head is blowing.
    which cloth do i have to use on the first layer before i put the plywood then which and how my layers on the top of the plywood to finish ?
    im asking about the oz - like 1.5oz , 2.5oz etc
    they do`t sale p-mat.
    You said do not use mat with epoxy.use cloth . this is pictures of mat and cloth
    from left
    first is the cloth,the second is mat,the the last on the right is rowing cloth

    that was my last ? i belive
    please :)
     

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  6. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Here's what I would do if it was mine. I would use polyester resin. Grind the hatch clean. In the picture in the first post, for me, there is too much gelcoat (the white coating) that has not been ground away. Polyester resin doesn't stick to gelcoat.

    The chart at post #3 here http://www.boatdesign.net/forums/fiberglass-composite-boat-building/fiberglass-thickness-8686.html will give the weights of cloth and resins required per square foot, so you can figure out how much resin you need depending on how much fiberglass you put on your hatch. A gallon of poly resin weighs about 9 pounds.

    Once the hatch and beveled ply were ready, (holes drilled, bevel cut and surface ground to new, clean wood with 24 - 36 grit disc, then vacumm clean) I would coat the side of the ply that's going against the hatch with resin and set aside. Then I would roll some resin unto the hatch, put a layer of 1 1/2 oz mat on that would cover the whole area up to where the hatch turns up on the edge. (Even though the the ply is cut to leave a 1 1/2 to 2" space around it's perimeter, running the mat to the edge of the hatch will leave a patch of brand new lamination to attach to when you come back the next day to finish the lamination.) If the hatch has been ground flat enough (with 24 or 36 grit disc) one layer of mat is enough. Coat the ply again, set it unto the mat, weight it all down, remove as much as you can of the excess resin that oozes out. Make sure your weights don't get stuck to the top by the excess resin that comes out the holes in the ply.

    Let this set and cure for a number of hours. If you finish in the evening, overnight is good. There is roughly a 24 hour window between laminations to get a good bond between them.

    Take off the weights, precut your glass to size and set it aside. (A layer of 1 1/2 oz mat and one of 18 oz woven roving should be good, I would use 24 oz as it only weighs a few pounds more in the scheme of things.) Grind the surface of the ply as before, and also the new mat around the edge. ( If you have the skill/experience enough, running the first and second laminations of mat all the way up the vertical lip of the hatch will add another inch or two of attachment strength that will work in the shear mode instead of the peel mode, which is much stronger. BTW, tape or heavily wax the outside of that vertical lip and all other areas you don't want resin on, to make clean up easier.) Resin the ply. (I always try and let that set at least until touchable so as to minimize the ply soaking resin out of the glass. A lot of people don't wait.) Lay on the mat and some resin, lay on the woven roving and roll it down with the roller "dry". That will consolidate the two and let the WR soak up excess resin from the mat. Then roll on resin until the WR is saturated pretty good. You don't need excess puddles, but at this stage they won't be a strength detriment. After that all sets, trim the edges, smooth the lumps and sharp spikes and paint or gelcoat.

    For the laminating use UNWAXED resin. Iso (FT-402) is best. (Plus the MEKP hardener) If you use gelcoat, use WAXED gelcoat. Of course disposable gloves, safety glasses, and ventilation and some acetone solvent are also needed.
     
  7. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    Thank You :)
    i will do it like You said but i think that i will use vinyl easter .i think that will better
     
  8. tunnels

    tunnels Previous Member

    so hows your hatch ??
    3/4 plywood and glass will be heavy ! right? and if it gets wet for any reason will be even heavier !!! :p
     
  9. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    the weather is getting better and warmer so i will start in about 2 weeks
    yes You are right and i din`t really need 3/4.
    1/2 will do the job i think
    thank You
     
  10. tunnels

    tunnels Previous Member

    1/2 will be springy for sure so the 3/4 will be better ! sounds like the cost of everything has scared the pants off you !! woven roving will still be springy and 1/2 ply wont help much at all . You think like the chinese guys i work with !!:rolleyes:
     
  11. andrew1
    Joined: Apr 2012
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    andrew1 Junior Member

    no,not realy but i have to do it outside
    one guy did this and he said is very good.he used 5/8
    so i thought what sam sam sugested if i will use 3 layers of cloth including rowing in between that should be stiff
    the one mistake he did imo that he did not drilled the plywood
     

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  12. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    It will be fairly heavy no matter how you do it. If you replicate what was there with similar stuff it should be fine. If 3/4" was on there, replace it with that. For a given weight, plywood is stiffer than fiberglass. Thickness and stiffness is also exponential, as in double the thickness and get 4 times the stiffness. Going from 3/4 to 1/2" is not saving much weight at all, it still takes the same amount of glass and resin, but it loses half the stiffness or so. But if it had 1/2" before and was allright as far as stiffness, 1/2" is fine.

    When you start taking it apart, some close up photos and thicknesses of the wood and glass might help us tell what it's made from.
     

  13. andrew1
    Joined: Apr 2012
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    Location: vancouver bc

    andrew1 Junior Member

    thank You
    i will make the pictures
     
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