glassing in chainplates

Discussion in 'Sailboats' started by bluwateronly, Feb 5, 2008.

  1. bluwateronly
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    bluwateronly Junior Member

    Okay, I have read all posts on the subject and can't seem to get an answer to my question. I was checking rigging before a sail and tugged on the foward lower and twang the chainplate broke, yes the boats lucky. I grinded out the port side chainplates and noticed no bolts just was glassed in. I went to Svendsen's metal works and had some new ones made up. Now the question, should I wrap the new chainplates in fiberglass and then bond to hull, bed them with 5200 and glass over or epoxy them in and glass, I even have seen them use fiberglass strands and bond that to hull. I have a little time since weather is too cold to do the work so I want some expert advice before I start the install. I have spent days pouring over information and none seems to answer my questions.
     
  2. PAR
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    PAR Yacht Designer/Builder

    Bond them in with epoxy and structural filler, but I'd also strongly recommend you through bolt them to a hefty backing plate which is also bonded to the inside of hull. Nothing like some good old fashioned through fasteners to keep some piece of mind. If you aren't sure it's strong enough then through bolt it, if your are sure enough, then through bolt it anyway.
     
  3. masalai
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    masalai masalai

    Otherwise add additional strengthening by adding more woven cloth to the bulkhead/hull - distributing the load, and make the entire assembly of glass - get knowledgeable advice first, it is the woven material that makes the strength not the use of big gobs of pure of epoxy. Then use a big screw in D shackle to attach the shroud/assembly....

    I have seen it done. it is elegant and sound engineering when done with advice from or by experienced & competent people.
     
  4. charmc
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    charmc Senior Member

    Good advice from both Par and Masalai. Reinforcing the attachment bonded area with additional cloth will add strength and spread the load. For insurance, however, my personal preference is to bond thoroughly, but then through bolt to a sturdy, well bonded backing plate. Overkill in the opinion of some, but I don't believe there is such a thing as too much strength.
     
  5. PAR
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    PAR Yacht Designer/Builder

    To give you an idea of the forces involved on those chainplates, take the displacement of the boat with a maximum load and double it. That's how much strain can be placed on them, when you drop off a wave on your beam ends (for example). Most designers have a reasonable safety margin factored into the laminate and pieces of the chainplate assembly. The smallest piece (typically pins) will have a working load limit above this double displacement figure, as this will be the weak point(s).

    It's likely you boat had loose plates that broke their bond, little by little until eventually tearing free. A big *** backing plate and some though bolts, spreads the load, transferring it to the hull for dissipation. This decreases the stress on the fasteners, laminate, etc. I prefer metal backing plates for chainplates. You can use plywood, which is much easier to bond into a 'glass hull. Make the backing plate (if plywood) at least three times as wide as the chainplate is and as long as practical. Tab it well with big overlaps on the fabric. The tabbing should rival the hull dimensions in thickness. In other words, if you have a 1/4" thick hull in the area of the chainplates, then you want that much tabbing holding the backing plate to the hull.
     
  6. bluwateronly
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    bluwateronly Junior Member

    Thanks for the geat input

    From all information I've gathered seems the best approch in this situation is to bond too hull using proper glassing procedures, I have the hull and deck repair book. I will post some pics tomorrow and i'm sure it will shed some light on my approch. The chainplate failed due to corrosion from years of neglect letting water in between the plate and glass. I saw no sign the plates were loose from the hull infact they seemed well bonded even after over 40 years of work.
     
  7. bluwateronly
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    bluwateronly Junior Member

    some pics

    Here are some pics, looks a bit scary at this point. There is bends in the chainplates that match the contour of the hull. I will be finishing the grinding this weekend and hope to get the new plates in. Now the only part I'm not sure on is do I lay a layer of glass and then epoxy chainplate to that and add layers on top doing all one right after each other so it becomes on unit. Any specifics would be great, this is my first fiberglass job so I want as much information going in as possible.
     

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  8. masalai
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    masalai masalai

    Bluw, Why repeat the problem? Make the replacement of "glass" using tapes or whatever they call woven strips, and lay out a series of bracing to fix the issue/problem properly.
    I am NO expert, but have seen it done. I will get some pictures - will have to do a bit of driving (which I hate) - but I feel the info is worthy of your serious consideration
     
  9. bluwateronly
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    bluwateronly Junior Member

    Great hope to see the info

    Thanks for the advise Masalai, I think my issue would be solved using epoxy mixed with glass strands to build up the sharp edges so the woven cloth I have will lay down properly. I will be looking forward to seeing some pics and more info. PS my dog hates all the work on the boat, as you can see;)
     

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  10. masalai
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    masalai masalai

    Hot off the camera. - - - This is off a Bob Oram 42 sailing cat. - Each assembly will hold more than FOUR (4) times the weight of the finished fully laden yacht! - - These points are used for lifting out on to the water at launch time...

    Contact Bob Oram for further information. - - The photo is of the builder - no more outside work, says he as... - his next will be his own, Oram designed sailing yacht.

    The first 2 are from the deck, the next are from inside (red stuff is peelply - to protect joins from gunk 'till he is ready to paint/finish)

    Email Bob Oram and when he gets back from sailing around & checking / helping builders, I am sure he will reply with the appropriate guidance...

    Don't use polyester around wood (balsa) as it uses chemical bonding & won't effectively stick to wood... use epoxy. See Gaughan Bros and other builders who use composites (wood & glass mix). Do not "bolt through" around wood as it is IMPOSSIBLE to guarantee no water will get in, use multiple layers of layup.....

    Ignore the window frame in #3 & 4 it is just stowed there for later use elsewhere... but hides some of the work..
     

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  11. PAR
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    PAR Yacht Designer/Builder

    Bluewater, grind down through the gelcoat over a wider area then shown. Make sure you have ground down to the mat. Wet out the whole area with unthickened epoxy then push into the recess some fabric. Wetout the area again, working it into the cloth which will pretty much go transparent, also wetout the chainplate metal (which should be freshly sanded) where it lands against the boat (set it aside for now). Next mix up some more epoxy, but thicken it with cab-o-sil or other structural filler, until it's about like heavy cream or loose peanut butter and smash a dollop into the recess (more is better, as you can always remove extra). Push the chainplate into the recess and insure you use enough pressure to seat it and have ooze out all around its edges. Don't push so hard or your smash all of the goo out of the joint, just stop when you have oozed all around and it feels and looks in place. You can stop at this point if you need to brace the chainplate to keep it in place or you can move on if it'll stay put.

    Smooth out the excess thickened goo, removing any that isn't helping fill the area. Place some more cloth over the repair area and wetout. Build up layers of fabric so you have the required thickness of material.

    Put that beer down, you ain't done yet, but you're getting close. If the area is reasonably flat, place a piece of clear plastic sheeting over the whole shooting mess, pressing it into the still wet goo and smooth out any wrinkles. Now place a piece of plywood (I use plexi glass because it's a lot smoother then plywood) over the plastic and brace this in pretty tight. Now go crack open a beer.

    When this sets up in a few hours (depending on the hardener you used) you can remove the brace and plastic sheeting. Under it, you'll find a very smooth surface, though along the edges you may have some ooze out or other clumps of not tacky, but still relatively soft epoxy. With a razor, cut away the soft clumps of excess goo. Now you can't do much until the whole thing cures good and hard. This can take a day or more depending on temperature, hardener, etc. Go get another beer and watch (or wait for) the goo to cure.

    With the cured patch, you can now finish sand to the level of smoothness you want. You'll have to feather the edges and generally sand more then you wish you had too, but the smooth area in the middle, as a result of the plastic sheeting will save you some effort. Paint it pretty, then call it done, possibly celebrated with another beer or two.
     
  12. Jimbo1490
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    Jimbo1490 Senior Member

    Don't forget to do the proper surface treatment of the aluminum before you bond them in. Acid etch followerd by chromium conversion (Alodine). Mil Spec yellow epoxy primer on all sides afterward is a good follow on option. This will make the plate VERY resistant to de-bonding again years from now, something to worry about even if you sell the boat as you have now undertaken to repair the chainplates yourself.

    Since these chainplates are of a manageable size, you have the option of dip treating in a plastic bag, tray or drum, which always yields better results than brushing or spraying.

    The chemicals are cheap and you don't need a lot anyway; just quarts.
     
  13. PAR
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    PAR Yacht Designer/Builder

    The chainplates (I would assume) should be stainless steel. I should also mention the chainplates should be well scuffed up with 100 grit paper, then wiped clean, just moments before applying a wetout coat of epoxy.
     

  14. bluwateronly
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    bluwateronly Junior Member

    Thanks Par, I took all your advise. I decided to just grind and sand down the whole section and lay a fresh layer of fiberglass (glass mat and roving)and then used some strips going down from the tee sections and three more layes getting bigger each time and final was to put a whole sheet of the super duper 45 degree angle mat and roving over the whole thing. I used a half gallon of apoxy and alot of glass. I will post some pics tomorrow, I know that damm camera is around somewhere. Thank you all very much!
     
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