Best way to get glass to lay flat on sharp exterior joints

Discussion in 'Boatbuilding' started by hospadar, Jun 24, 2013.

  1. hospadar
    Joined: Apr 2011
    Posts: 60
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    Location: Michigan

    hospadar Junior Member

    Getting ready to get going on my 3rd little wooden stitch-and-glue plywood boat, and I have a question about a problem that's vexed me on the other two boats.

    When I have a sharp exterior corner (90 deg.), I have a helluva time getting fiberglass/fiberglass tape (I use 6 oz biax tape on seams) to lay flat around the corners. I tend to find a lot of bubbles and resin pockets under the tape on either side of the edge.

    Things I've tried:
    - Radiusing (3/8") and sanding corners smooth
    - Applying resin to the edges and letting it get tacky before glassing. The tackyness doesn't really have enough hold to make a big difference

    Any tips for getting my glass to really lay flat reliably on corners like this?
    Should I be:
    - Applying tons of epoxy putty to the corner and sanding it smooth?
    - A bigger radius? 1/2" - I could maybe go to 3/4" but It's only 1/4 inch ply so I'd really be digging into the fillet on the inside of the joint this way
    - Something else I've not considered at all?
     
  2. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Radius is the big part of it. One tip I remember reading that works for me, is to leave the glass draped over the edge for 24 hours. It tends to sag into the shape.

    Finally, the ultimate solution is to put peelply over the difficult edge and smooth it down. If you leave quite a bit of extra peeply on the edges , you will find you can get a lot of pressure on the 'sharp' bits, and force it into shape.

    Check out the middle picture at

    http://greencanoe.weebly.com/furniture.html

    where I get 6oz cloth to conform to a gunnel edge with peelply..
     
  3. member 52498

    member 52498 Previous Member

    corner problem

    Can you get to the inside to run am epoxy cove? Maybe try the filler in exterior and radius , or tape to hold it down, resin and micro fibre/ cab-o-sil thick slurry - wet on wet, or make a mould up of the job and glue it on with resin/fibre mix. Can you vacuum bag it with a super fast hardener? Also, tape to the peel ply's dry edges and pull tight.
     
  4. hospadar
    Joined: Apr 2011
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    Location: Michigan

    hospadar Junior Member

    Mmmm taping down the peel ply. I think I'll give that a go. I don't really want to bother vacuum bagging. I might be able to pull it off, but for such a small project I just don't really care enough.
     
  5. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Taping peel ply might work if you have cured glass close to the sharp edge, but usually you are doing a big area at the same time.

    Try a test patch if you like, but what I found is that you can smooth the peel ply very tightly using the surface tension of the wet epoxy on the flat surfaces, and you may not need to bother using any tape.
     
  6. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member


    With a 25 mm radius I have no problems with getting 6 or 12oz Biax 45 45 cloth .
     
  7. garydierking
    Joined: Sep 2004
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    Location: New Zealand

    garydierking Senior Member

    The secret for me has always been to use multiple small overlapping round patches. There are very few shapes that a small round patch of woven cloth won't conform to.

    dl.dropboxusercontent.com/u/21351227/P8230226.jpg
    dl.dropboxusercontent.com/u/21351227/P8230228.jpg
     
  8. boatbuilder41
    Joined: Feb 2013
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    Location: panama city florida

    boatbuilder41 Senior Member

    Try using a material with a 45 degree weave and stitch . Its called 1808 stitch mat. It is made for radius edges. You would not believe how nice of a job this material can make. Just be carefull not to use to big of a piece. This material can stretch out real easy. You won't be able to move it around much after wetting with resin
     

  9. tunnels

    tunnels Previous Member

    Improvise !! Thats what its all about !!!

    Double bias light weight a couple of layers and stager the joins of v=cut the woven cloth on a 45 degree angle will give you double bias !! Peel ply rolled and put plastic or mylar over the top and tape and pull firmly . there's lots different ways Done get confused with the radius and diameters people are talking about a 10mm radius is a 20 mm diameter and that's heaps to get any glass !!, run strands angled at a 45 degree round a corner is much easier than simply trying to go straight round !!. Use lighter glass and more layers rather than one heavier cloth and just one layer !! Also use long strips not silly little patch's that at the end of the day is weak !!. :D
     
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