Recording gunnel

Discussion in 'Fiberglass and Composite Boat Building' started by Mrgibbs1, May 12, 2016.

  1. Mrgibbs1
    Joined: May 2016
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    Mrgibbs1 Junior Member

    Recoreing gunell

    Any advice on re Coreing gunnel . I've have cut out the bottom glass and now want to replace the core with plywood . The fiberglass store thinks I should use polyester ? I just need the best bond to the underside of the gunnel ,so the rod holders will not flex . Should I use glass matt between the wood and the bottom of the gunnel ?if so whit kind ? If I use epoxy can I just butter up the wood and press it up , then glass the bottom prices I cut out out back in .
     
  2. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    What's the make, model and year of your boat? Polyester and wood don't work nearly as well as epoxy. The guys at the "fiberglass store" should know better. Is this a marina ship's store, a retail marine store or the local auto parts store that also sells marine stuff? If so, try someplace else, unless you have something specific you need, know the normal price and don't need their advice. Simply put, a "fiberglass store" will know the realities of polyester on wood and the abilities of epoxy, comparatively.

    If using epoxy, coat the plywood piece(s) with epoxy on all sides, in all holes, notches and cutouts, especially the end grain. 3 coats except the side that will be bonded underneath the side deck (my assumption). When ready to install, wetout the underside of the side deck wit epoxy and smear a thickened batch of epoxy with a 1/8" notched trowel on the plywood and press into place. Not tightly, just enough so the epoxy oozes out all around and is in full contact with the underside of the deck cap. Brace this into position and give it a day to cure. If you have to do more drilling, cutting etc., coat the holes or whatever with more epoxy, which will keep out moisture.

    The same procedure is done with polyester, except you'll use mat between the plywood and the side deck and the plywood will probably rot anyway, in spite of coating it with polyester, because it sucks on wood. A polyester reinforcement will also be generally weaker too, but lots of folks use it anyway, mostly because of price.
     
  3. SukiSolo
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    SukiSolo Senior Member

    What is the thickness of the core? A lot of thin ones can just be replaced by epoxy and suitable filler material ie glass fibres, microballoons etc. The reglass over it. I prefer roving to mat but you may require both. Check for epoxy compatibility when using mat, as some is specifically polyester use.

    A thick core is often better replaced by solid timber using the grain to help compression loading. Epoxy is 'better' than polyester, but sometimes you can work the two together well depending on the repair. Sort of horses for courses.

    Otherwise, follow PAR's excellent advice.
     
  4. Mrgibbs1
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    Mrgibbs1 Junior Member

    Thanks for the response . The fiberglass store is a wholesale operation that will sell To the public the guy ther seems to think epoxy may not be nesseary . With all the reading I've done I think it would be the way to go . The Boat is a 99 hydra sports 2250 the gunnel is all wet balsa core , seems no one sealed the rod holders the right way so it's my problem now . So far I've cut out the bottom glass . The core is only 1/2 and the bottom skin is very very thin . My plan was to use the west six10 tubes and cut a pice of plywood and past it up to the top then fill in the sides . When bonded past the bottom skin back on and go over the seems with some type of fiberglass mat? I would like to strengthen the gunnels up maybe add to it so it will not flex When a down rigger is in the rod holder . The back rod holder hole has less acess to it so a smaller pice of wood I all I can get in . But I can squeeze epoxy in 4to 5 inches I to the void then buttup the wood to it to it for a total of 12 inches . Is a 1/2 thick 6 " wide 5 " long to large of a space to be a solid puck of epoxy? Thanks http://img.photobucket.com/albums/v712/jdgti/Vector gunell/image_3.jpeg
     
  5. Mrgibbs1
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    Mrgibbs1 Junior Member

    would a nice pice of Douglas fir trimmed to fit be a better choice , then use polyester with mat to replace the bottom skin? While using epoxy to do the rest ?
     
  6. PAR
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    PAR Yacht Designer/Builder

    Six-10 is a thickened adhesive and works well, but it's not going to protect the wood from moisture ingress.

    The procedure is to remove the bottom skin (which you've done), clean (grind) the area to good, clean material. Wet it out with straight epoxy and apply the prepared reinforcement in a bed of thickened (Six-10) epoxy. You can also stick the old bottom skin back on at this point.

    Any piece of wood that goes in there will need to be "entombed" in epoxy, completely, with a 10 mil or thicker coating. Other wise it's going to rot. This embalming process requires every hole, cutout, notch and especially the end grain receive this treatment. Yeah, a pain in the butt, though it insures you'll not have to worry about it again, so it's your call.

    Mat (CSM) doesn't really add any strength, it's a bulking material used in polyester laminates. Epoxy laminates don't need CSM, except on rare occasions (prevent print through, special bonding, etc.). If you want to reinforce the general area, use cloth or a biax fabric and you'll need a few layers to do any real reinforcing.

    Don't mix resin systems - pick one, polyester or epoxy. Polyester can do the job, but you'll be better off without wood in there, so consider using "Coosa" or similar. Epoxy can do the job and will be stronger and more water tight, especially if using wood. Epoxy will stick to polyester, but polyester doesn't stick to epoxy very well, which is why you don't bounce around with resin types.
     
  7. Mrgibbs1
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    Mrgibbs1 Junior Member

    The advice was spot on, my repair is rock solid the only problem is that I want to cover it with glass Matt to make it look good and add some support but , I can't seem to make it stick I'm using epoxy and 1708 with a slow hardener .it the 1708 to heavy , ployester iwould be easier and would tack while wetting it out . Any ideas [​IMG][​IMG]
     
  8. Mrgibbs1
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    Mrgibbs1 Junior Member


  9. rwatson
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    rwatson Senior Member

    If you use CSM, get some Peel Ply ( or Taffeta from the Sewing Shop ) to lay over the CSM after you wet it out. You will abe able to shape and smooth the glass before its cured with your fingers, straight edge tool or whatever gives you a flat finish.
    After a few hours at partial cure, you will be able to peel the fabric away from the goo, and leave a smooth, neat surface. CSM would add a bit of weight.
    If you want to experiment, and since the gunnel could act as a usefull flotation area, I have had reports that polyester beads like the ones you find in BeanBags mix well with resin. You could make up a thickened mix, and plaster it up under the Gunnel to hide the messy bits, and if you also used Peel Ply there, you could get a couple of inches of tough, lightwight waterproof floatation that looked professional. Might be worth a bit of small scale experimentation.
     
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