Overhead Epoxy Work

Discussion in 'Fiberglass and Composite Boat Building' started by FrigidNorth, Dec 31, 2012.

  1. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    Ahhh BILGE KEELS !!!


    I didnt understand the term "rolling chock ".
     
  2. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    What do you think of this chock angle? The purpose of the chocks is not only for roll dampening but also to to keep the stern from sliding in following sea conditions which I found can be pretty exciting and call for a lot of work at the helm. To go along with the chocks i plan on 9 foot pvc spray rails on the bow chine to keep spray down and lessen bow plunge into the wave in front. Spray rails might be a topic for another thread but my plan there is to glue and screw with stainless screws and 5200.
     

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  3. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    I can't take credit for These ideas, here is the website of the fellow with the sister ship to mine. He has lots of good photos and I've talked to him several times but I was missing some technical info on how to actually put it together.

    https://sites.google.com/site/lhboatinfo/
     
  4. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    First Test Panel

    I've put together a test panel to try out the technique recommended by michael pierzga. I'm putting a lot of details in here so I can look back at this thread for my own reference, so please excuse me if it seems kind or wordy.

    For the test I constructed a fake rolling chock, which was just 3/4" marine ply at a right angle to a larger piece, simulating what I will be up against later. I coated both pieces with epoxy and let dry, then sanded with 80 grit to prepare the surfaces for bonding. I then made up a mix of epoxy and silica very thick bedded the "chock" and made a fillet on both sides similar to how I envision it happening.

    After that set overnight I made up a "prepreg" with 6 layers of 10 oz cloth, cut at a diagonal to take advantage of both directions of fabric. I made the first one full size (10" X 18") an each additional layer smaller to taper, with the smallest piece on top.

    I then saturated with neat epoxy. It took about 220 grams of epoxy to wet out this amount of fabric. Even after thorough squeegee action there were dry spots on the back when I flipped it over and removed the foil. I mixed a little more epoxy and used a roller to fully saturate. I then rolled a light layer of neat epoxy onto the test piece, and applied the prepreg to the test piece. I left the 4 mil on and used the squeegee to work it into place before peeling the 4 mil off. I squeegeed towards the fillet which seemed to work. I then used the roller to lay all the threads down.I put in on overhead/upside down I am happy to say it stuck like magic.

    Things to do different:
    1. A larger fillet with more radius would be helpful
    2. Cut the fabric wider in both dimensions so it is easier to layout and trim to the appropriate size.
    3. Use two different colored sharpies for the fabric and for the foil.
    4. Make a square template for cutting fabric - it stretches all over the place

    This will leave me with a bunch of butt joints, is that a problem even if I stagger them on both sides of each chock?
    How does this sound for a layup schedule, 60 oz per side adequate?
    I'll see how it looks when cured, would peel ply be necessary?
    Any other thoughts?
     

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  5. OFFSHORE GINGER
    Joined: Nov 2011
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    Location: Mich

    OFFSHORE GINGER Junior Member

    From the looks of things .....you have just taken something very simple ( layup ) and make it L@@K very complicated ..........WOW !
     
  6. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    Big fillet is good.

    Pre preg on a wet out table is good.

    Offseting the edges of the cloth is good. 1 inch is minimum, most times I see 2 inch offset specified on plans

    I dont know about layup schedules. Logic says that there is no need for the structure to be lightweight, so use plenty of glass fiber.

    Cloth with fiber orientation that is 0 90 is not the best choice. only 50 percent of the glass fibers will cross the joint.

    Biaxial 45 45 weave is superior...all fibers cross the joint.

    several layers of Stitched 12oz 45 45 eglass would be a good choice and is a very common cloth

    You can also cut 0 90 fabric on the bias to make your own 45 45 but it is tedious.

    One detail that will need some thought is how to terminate the ends of the bilge keel. Stress concentrates at the ends . Cracks will develop. A long taper sounds logical
     
  7. mikereed100
    Joined: Jan 2007
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    Location: Borneo/California

    mikereed100 Junior Member

    Frigidnorth,

    I recently had to glass the underwater sections of both hulls on my 46' cat. It was actually fairly easy with just my wife and I doing the work. We would roll on a layer of epoxy, then I would apply masking tape to the upper edge of the glass panel to be applied with about 1" overlapping. I would then clamp batten to the bottom edge with lightweight stationary clamps. I would carry this over to the hull, stick it onto the side with the tape, pass the battened edge under the boat to my wife and while she held it in place I would quickly wet it out. Then my wife would remove the battens and wet out her side. While I went back to get more glass my wife would go over the panel with a ridged roller and then apply epoxy to the next panel area.
     
  8. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    With the mild weather this week I was able to finish gel coat removal on the underside of the hull, so i temporarily attached a chock to one side to get a feel for the position and angle I want to use. This also gave me an idea of the dimensions for pre-cutting the cloth for layup in the spring. One this I noticed is that I have a gap of 1/2" at the very front of the chock moving to no gap about 3 feet back from the curvature of the hull. Can i use thickened epoxy to bridge this gap or should I trim the chocks to get the chock closer to flush with the hull?

    I also think i have decided on a layup schedule of 8 layers of 12 oz biax for each side of the chock. I plan on laying up 18" long sections of 4 layers, with a 9 inch overlap. My plan is to graduate the size of each of the four layers - something along the lines of 8" wide, then 11", then 15" wide, the a final layer 18" wide. My question here is should how should I layer the four layers for the best strength? Should I have the narrowest piece of biax against the hull and chock or on the very outside.

    Thanks!
     

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    Last edited: Feb 3, 2013
  9. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    Update:
    Got the chocks glassed in place this weeken. Me and a helper took about 24 man hours. It went pretty well all in all. Had no trouble getting the glass to stick upside down, but i did get some in my hair! I used system 3 with the fast hardener because of the low temps here. 7 gallons of epoxy, 10 qts of silica and 5 of microspheres. I'm letting it dry for two weeks before sanding and bottom paint. Some things I learned:
    Temperature really changes the viscocity of the epoxy. It warmed up 20 degrees during he day and it flowed through the fabric much better for wet out.
    I tried squeege and rolling pins to assist the wetout, but the best and by far fastest method was spreading it around by hand between each of the three layers I applied at a time.
     
  10. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    Pics of fillet.
     

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  11. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    Fillet 2
     

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  12. FrigidNorth
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    Location: Kenai, AK

    FrigidNorth Junior Member

    Glass on
     

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  13. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    Fairing on but not sanded
     

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  14. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    Its dangerous to pick up a bilge keeled boat with a travellift,or slings. Be sure to mark strap locations or notify the shipyard of your special appendages before hoist.
     

  15. FrigidNorth
    Joined: Dec 2012
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    Location: Kenai, AK

    FrigidNorth Junior Member

    I hire a hydraulic lift trailer for launch and takeout, no slings!
     
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