ply over glass hull leaking...help! :S

Discussion in 'Boat Design' started by floydrob, Jul 18, 2008.

  1. floydrob
    Joined: Jul 2008
    Posts: 38
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: scotland

    floydrob Junior Member

    hi, i just made a ply over glass hull,or glass over ply or whatever its called, i dont know much cos i'm only 15 but this is my 3rd boat made of ply but my first attemps at fiberglassing. iu got epoxy resin as advised by sum1 on here cos it is more flexible and doesnt crack so much, but i covered all the corners, chines and the keelson in fiberglass, everywhere where water could possibly get in is fiberglassed but ther is loads of tiny pinpoint holes. how do i get rid of them, cant afford another l;ayer of fibverglass and i dont have very much resin left., she floats but every hour or so i have to bail some water out.i was thinking of putting some sealant on the inside of the joints but i recon that would just cause water to get trapped between the fiberglass and the sealant and rot the ply. any help greatly appreciated :D
     
  2. KnottyBuoyz
    Joined: Jul 2006
    Posts: 829
    Likes: 55, Points: 0, Legacy Rep: 685
    Location: Iroquois, Ontario

    KnottyBuoyz Provocateur & Raconteur

    Sounds like you might have a leak larger than a few pinholes. That's going to be tough to track down though. If you don't find the leaks and plug them the water getting into the ply will eventually rot it out.

    Have you painted the hull yet? Can you post a picture of the area you think is leaking. Coating or plugging from the inside won't help at all.

    If you have a way of thinning the epoxy and recoating the areas you think might be leaking that might help. I once read about a guy who had a similar problem. He was working on a small boat and flipped it upside down. Sealed the entire boat with plastic and used a shop vac to put a vacuum on the hull then recoated the outside with thinned epoxy. The vacuum pulled the epoxy into the pinholes and sealed them up. Sounds kinda tricky!!!
     
  3. Frosty

    Frosty Previous Member

    Cheapest way to get round that would be to mix up some paste with what you got left of your epoxy, like mix it with talc or similar, smooth the filler over all the holes and paint the whole thing with some paint,--any paint.

    It'lle make it water tight.
     
  4. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 121, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    Your problem is most likely too much dependance on epoxy coupled with too little epoxy to do the job. Now, how to fix the pinholes?
    I see no alternative besides sanding the taped seams and adding another layer of light tape. I realize this means expense, but if the boat is small, just a quart should do.
    I don't know how the chines are constructed but I'm guessing with chine logs rather than fillets over stitch and glue.
    When you're short on cash, chine logs WELL FITTED AND BEDDED with polysulfide or some good below-the-waterline sealant will keep the sea out for years. It makes no sense to depend on the sealing forgiveness of epoxy if you can't afford enough epoxy to make it work.
    In any case, welcome to the forum. It's great to see people of your age building boats.

    Alan
     
  5. Manie B
    Joined: Sep 2006
    Posts: 2,041
    Likes: 116, Points: 63, Legacy Rep: 1818
    Location: Cape Town South Africa

    Manie B Senior Member

    please post some pics
    i may be able to help if i can see what you did
     
  6. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Thinning epoxy is a bad idea, it lowers its waterproofing level

    try a search on the subject
    http://www.boatdesign.net/forums/showthread.php?t=23206&page=2&highlight=thinned epoxy\

    The best solution is the suggestion to go over the unpainted surface with a thickened epoxy carefully, covering all the holes.

    If you have already painted or varnished the surface, then apply several more coats of that paint or varnish until every little hole is filled in.

    If you have some major voids, you will need to grind them out, and refill with epoxy. Finding them is easier by sitting the boat on some old tyres and hosing water on the inside against the seams until drops appear on the outside of the hull
     
  7. kengrome
    Joined: Jul 2006
    Posts: 718
    Likes: 25, Points: 0, Legacy Rep: 305
    Location: Gulf Coast USA

    kengrome Senior Member

    If the boat is not designed to handle the stresses its joints are experiencing, it will take a lot of 'fixing' to eliminate these stresses before any pinhole filling will work reliably. I would like to get to the source of the problem, and this probably means posting pictures of your hull and describing how you constructed the joints ...

    When most people use epoxy and glass on joints they do not do it simply to waterproof the joints. The reason for using epoxy and glass on plywood joints is primarily for structural strength. -- waterproofing is a secondary effect -- and joints never leak when the plywood panels have been welded together properly with epoxy and fiberglass. This assumes the design is well engineered to avoid stresses or distribute them rather than concentrate them in the first place of course.

    Please describe the specific way you created your plywood joints, and post pictures of your boat so we can see what we're dealing with here ...

    :)
     
  8. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Ooooohhhhh - now i remember!!!!! Floydrob has already posted a picture of his boat previously - just did a search.
    I am not surprised the joints leak Floyd - they are amongst the roughest joints I have seen, and unless you used several layers of cloth very well saturated with epoxy, then the fact that you dont sink is a credit to you.
    I am interested in the 'foam' you used to 'glue' the edges together. Is it what the call Balcotan of somthing like that?

    Ken gromes interest in the flxing joints might be well justified too.

    Have you applied paint yet? It will be easier to fix if not. lets know what stage you are up to.
     
  9. kengrome
    Joined: Jul 2006
    Posts: 718
    Likes: 25, Points: 0, Legacy Rep: 305
    Location: Gulf Coast USA

    kengrome Senior Member

    I just did a search and found these pictures:

    http://www.boatdesign.net/forums/attachment.php?attachmentid=23001
    http://www.boatdesign.net/forums/attachment.php?attachmentid=23002

    floydrob, if this is your boat I applaud your effort as an inexperienced teenager, but as much as I hate to hurt your feelings I'm going to tell you the truth because I think you should hear it from someone:

    You did a whole lot of things really badly on this boat, starting with the design itself and progressing to the use of inappropriate materials and really bad construction techniques. I'm not saying this to discourage you, but I think you should stick to building boats designed by professionals -- or at least experienced amateurs -- because this one is a real mess.

    Why don't you get some plans for a small and simple boat, and then build it properly -- by following the designer's plans very carefully. You have enough materials already if you take this one apart and clean up the pieces. Why not use them to build a proven design?
     
  10. Dane Allen
    Joined: Jul 2008
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: So Cal

    Dane Allen Junior Member

    You've shown a lot of creativity, resourcefulness and drive for someone your age...but I want you to live. So, go to your library and check out some books and DVDs on boat building. Also, practice joining small pieces of wood and also laminating small pieces together and chalk this boat up to experience. It would make a great sandbox in a school yard.
     
  11. Dane Allen
    Joined: Jul 2008
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: So Cal

    Dane Allen Junior Member

    I'm probably going to regret this but I have to take exception with something Kengrome said about epoxy and glass being primarily for strength and waterproofing secondary. I know Ken has a lot more posts than I but this was nagging at me.

    While fiberglass does add some strength to joints I have always understood to never think of it as structural component. Rather, the main benefits of fiberglass are (in no particular order) 1. Reduce hull maintenance 2. Improve appearance 3. Waterproof the hull and 4. Protect from impact/abrasion. I derived this list in parts from Ken Hankinson's "How to Fiberglass Boats"., Glen L. Witt, Naval Architect, "Boatbuilding with Plywood" and several other publications and on-line references.

    Let the flames begin :- )
     
  12. kengrome
    Joined: Jul 2006
    Posts: 718
    Likes: 25, Points: 0, Legacy Rep: 305
    Location: Gulf Coast USA

    kengrome Senior Member

    Well, I guess you can think of epoxy and glass however you like, but you're missing some very important information I'm afraid ... :)

    Practically every plywood joint I build is held together with epoxy and glass, I've been building this way for almost three decades, and I have yet to see or hear of any of my joints failing because the epoxy wasn't structural.

    There's not a single nail or screw or staple or rivet or any other mechanical fastener remaining in this Tolman Seabright skiff I'm building -- it is ALL held together with epoxy and fiberglass -- and if that's not 'structural' I don't know what is:

    http://www.bagacayboatworks.com/images/seabright01/
    http://www.bagacayboatworks.com/images/seabright02/
    http://www.bagacayboatworks.com/images/seabright03/

    These boats and tens of thousands like them are built using the extremely common "stitch-and-glue" technique ... which means they are all being held together with epoxy and glass which creates the structural bond between the panels. Using epoxy and glass PROPERLY along a plywood joint produces what is essentially the same effect as if you were to be able to weld the two panels together -- it is stronger than the wood alone.

    I'm glad you think so ... :)

    Don't get me wrong, these are all acceptable reasons for using epoxy and glass -- but you're definitely missing something on your list here -- and it's a biggie.

    Perhaps it is hard for me to understand how anyone in this day and age can fail to recognize epoxy's exceptional performance as a structural adhesive because I've been using it for so many years in this role ... but epoxy and glass are absolutely structural in my everyday use of these materials -- and I'm sure in many many other builder's use as well.

    I haven't tried but if you know how to use Google I'm sure a search there will pull up more than you every wanted to know about the structural applicaitons of epoxy and glass fibers, not only in boatbuilding but in automotive applications, industry, aerospace and many other industries.
     
  13. Dane Allen
    Joined: Jul 2008
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: So Cal

    Dane Allen Junior Member

    Excellent points. In thinking back, I think the gist of the "epoxy as a structural component" discussion arose from people who thought that they could use, say, 1/2 inch ply in conjunction with fiberglass instead of the 1 inch ply recommended in the plans (to save money, of couse.)

    Suppose you T-bone a submerged log at a certain speed, will the fact that you used fiberglass on a thinner than recommended hull keep your hull from opening to the sea? I completely understand and agree that epoxy is a wonder jointing adhesive that makes many fiberglassed boats what they are today. What, triple the peel of Ployester with much more wood saturation?

    But, and maybe this is splitting hairs, I don't see that fiberglass cloth/mat applied to the hull strengthens the hull to the extent that the urban folklore prostyletizes. Otherwise, why even use wood? We would just make a fiberglass skin like that on the old canvas skinned bi-planes, soak with epoxy and call it a day.
     
  14. the1much
    Joined: Jul 2007
    Posts: 3,897
    Likes: 44, Points: 0, Legacy Rep: 696
    Location: maine

    the1much hippie dreams

    you dont need wood,,,at all,, for anything in a boat,,,BUT,, now a days,, im sure its the wood giving a little strength to your glass? instead of how it use to be as the glass giving a little more to the wood.,, most use wood just for the "form" ,,does sand give aluminum strength?,, or does the aluminum give the sand strength?,,cause if you step on plain sand,, its pretty easy to squish,,or if you step on a can, its just as easy,,,,,,,,but,,,,,if you step on a can of sand,,,,,hmmmmmmm <<<<damned soda can analogy ,,hehe :D
     

  15. tom28571
    Joined: Dec 2001
    Posts: 2,474
    Likes: 116, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    Dane,

    The epoxy and glass in the joints of S&G boats ARE structural and that is their primary reason for being there. The proof is overwhelming and I suspect you misread something that was in Glen-L's material.

    Floyd could benefit greatly by taking his advice seriously also but I doubt that will happen. Some tried to steer him in the right direction when he first posted but were accused of being spoil sports and too negative to a young and enthusiastic builder. No one is done any favor when they are told that a bad idea is a good one.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.