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Hull fairing matl.?

Discussion in 'Wood and Canvas' started by chris pearson, Jan 7, 2008.

  1. chris pearson

    chris pearson Michigan Canoe Nut

    I got a "factory" low spot on the outside hull of my OT Guide. It is rib width and about 30" long. How can I fill it in, assuring the patch wont move later on after the canvas is on and the canoe gets wet? Any ideas? I'm sure you guys have run into similar situations before. :confused:
     
  2. bob goeckel

    bob goeckel Wooden Canoe Maniac

    does it run across a group of ribs? do you have a picture?:eek:
     
  3. OP
    OP
    chris pearson

    chris pearson Michigan Canoe Nut

    nope

    Its over and parallel to the rib. Almost like they strapped it down and it stayed that way.
     
  4. bob goeckel

    bob goeckel Wooden Canoe Maniac

    assuming the hull is bare could you try soaking the cedar? it may swell it back out to shape. my next GUESS would be a filler made of fine sanding dust and epoxy. i use a product called super bond from fgci.com. a half pint of the epoxy and half pint of the hardener lasts me a year or more. it's a slow cure usually 8 hours to overnight. a heatlamp will push that time nicely. lastly if the rib was not leveled to begin with then a new rib might be the last resort. not a big fix. good luck
     
  5. Todd Bradshaw

    Todd Bradshaw Sailmaker

    I might caution against using an epoxy/wood dust mix. The reason is that it tends to make a pretty hard fill - much harder than the cedar around it. When you go to sand it to a flush, smooth shape it may be quite difficult to do so without dishing the cedar on either side of the fill. Epoxy mixtures made for hull fairing are generally phenolic microballoon mixtures, which are much easier to sand. You first coat the area with a thin coat of plain resin. Let it harden enough that it won't smear when you work on top of it and then mix your filler goop. The easiest to find may be a can of WEST System #407 low-density filler additive from places that sell marine supplies. You mix a small portion of your resin and hardener, stir them well and then start mixing in spoonfulls of filler powder. You want a mixture that is stiff enough to stand up without sagging and flowing (think peanut butter) and this is achieved with a lot of filler and a small amount of epoxy. If in doubt, add more filler as it is critical that this stuff holds it's shape, rather than start to run 15 minutes after you apply it. Overfill the area slightly using a spatula or stiff squeegee and let it harden. Once hardened for a couple of days (minimum) you sand it flush with a block of wood with some medium-grit sandpaper wrapped around it. With a filler of this density the task isn't too different in terms of smearing on the goo and later sanding it smooth, than filling a seam between two sheets of drywall in your kitchen.

    This might be overkill, but I doubt the trench is actually very deep, which brings up another potential problem. The final, sanded fill won't be very thick and it will be crossing the seams between the planking. I'm not at all worried about the fills coming loose, but I am a bit worried about them cracking at the planking joints as the boat flexes and the planking moves. If it was my boat, I think I'd do my filling and fairing and then make small saw-cuts through the fill following the planking joints to allow more independent movement between the planks in the filled area.

    Which brings up repair option #2: Whenever possible, the best filler for wood is often more wood. Not having seen the boat, I don't know how practical it is, but buying a 4'-5' long hunk of planking stock, cutting it into short chunks and glueing them into the depressions, plank by plank with epoxy resin might be possible. Once the epoxy hardened, they could be planed and sanded down flush and any additional filling done with a resin/filler mix.
     
  6. Fitz

    Fitz Wooden Canoes are in the Blood

    Exact opposite problem

    I have a similar issue with the Godzilla canoe, although exactly the opposite. I have a bulge in the canoe. It almost looks like someone had a habit of using a big boulder as ballast in the bow. It dented the rib and pushed out the planking making the bulge.

    My plan is to try and some hot water first, and maybe re-tack the planking, but I suspect that I will end up pulling the rib and putting in a new one to get rid of the bulge.

    I was just thinking hot water and even a new rib might be easier than all the goop. Maybe your low spot won't show under the canvas anyway??? High points will show though.
     
  7. OP
    OP
    chris pearson

    chris pearson Michigan Canoe Nut

    heres what I did...

    In making canoe models, I just took some scale planking scrap and used industrial gap filling super glue to glue the thin cedar over the depression, then sanded it level. I have used this super glue on my models and know that it will never let go. On models, I use it to glue the planks over the ribs after coming out of a pot of hot water, so I know its water resistant. I'm ashamed to say it but I've also used this stuff on hairline planking cracks before and it holds well. Anyone else ever use it?:rolleyes:
     
  8. Denis M. Kallery

    Denis M. Kallery Passed Away July 3, 2012 In Memoriam

    Chris,
    I too was going to suggest using a thin piece of Cedar as wide as the planking. Gluing it with Titebond 3 and fairing it. Seems a whole lot simpler than mixing up all the goop.
    Denis
     
  9. bob goeckel

    bob goeckel Wooden Canoe Maniac

    the epoxy was an ill-thought out idea. the voices were SO wrong this time. it wasn't my fault:eek:
     
  10. Todd Bradshaw

    Todd Bradshaw Sailmaker

    There's nothing wrong with epoxy Bob, or the method you suggested, other than the specified filler to be used. In some ways the epoxy fill is the easiest and fastest way to permanently fix a problem like this. It's damned difficult to fair a hunk of glued-on cedar to just a hair above flush with a squeegee so that all it needs is a little bit of finish sanding and you're done. Funny thing about epoxy is that folks tend to either be good with it and confident using it because they've taken the time to learn how, or scared to death of it and not interested - which always brings up the same arguments of "too much trouble" or "too messy" etc. In reality, it probably took me as long to write the instructions above and try to get them reasonably clear than it would have to do the job. Once the materials needed are gathered, there is maybe an hour's worth of actual work there, even for somebody who is new to working with resin.

    There is no question that epoxy is the best waterproof marine glue available in terms of sealing the joint to prevent future water-absorption-caused failure and in exceeding the grain strength of the wood. For glueing-in chunks of new wood, super glue has never been shown to be a durable marine adhesive and Tightbond 3 is generally used in situations where it will be epoxy coated later or at least where the joint can be varnished or painted to seal it and accessed and repaired later if needed. In this case, if the glue fails, it's going to be damned difficult to get back in there and fix it. If epoxy is the most durable, best sealing wood glue available for the job at hand, it takes some pretty strange logic to justify using something inferior.
     
  11. OP
    OP
    chris pearson

    chris pearson Michigan Canoe Nut

    superglue

    I did use superglue to glue in the pcs, hope it doesnt bite me in the butt later. I know it is waterproof, but can get brittle. I'm going to cover it with west system epoxy to protect it. It wasnt a real big area and not very thick as well, but I know that it would show with glossy paint. If it wasnt in just one area, I would have figured something else out. :rolleyes:
     
    Last edited: Jan 8, 2008
  12. Fitz

    Fitz Wooden Canoes are in the Blood

    Putty

    I wouldn't worry about it. Tonight, I pulled the original canvas off Godzilla (late 60's vintage Chestnut) and the spaces between the butts of planks were filled with wood putty. I bet your fix will last longer than putty.

    Cheers.
     
  13. bob goeckel

    bob goeckel Wooden Canoe Maniac

    what if any are the problems associated with retacking through the epoxy? would it tend to bend the tacks prematurely?
     
  14. Todd Bradshaw

    Todd Bradshaw Sailmaker

    If it was used as glue - simply to glue more wood on, it likely will be so thin inside the joint that it won't be a problem. If it's a fill, using an epoxy/filler mix and having more thickness, it might tend to shatter around the tack and it's possible it might bend the tacks. It's not too hard to get an epoxy mix that will flex a bit with the cedar in thin applications or which will sand similarly to the cedar, but getting one to accept nails like cedar is a pretty tall order and probably not going to happen.
     
  15. Rollin Thurlow

    Rollin Thurlow member since 1980

    If a hollow is so serious that it need repairing the best method is to just do it right and replace or reform the offending ribs and or planking. Applying large patches of glue or laminating wood over planking is just asking for trouble. It is difficult to fair without grinding off more good wood or fastenings and it will make a hard spot in the hull that will not flex like the rest of the hull. Old planking is usually impregnated with old dirt and oil which makes the bond process even more questionable.
    By the time its all said and done, it's no more difficult to replace the ribs and planking than fooling around with a method that has a questionable future.

    Rollin
     
  16. Todd Bradshaw

    Todd Bradshaw Sailmaker

    I'd love to hear the blow-by-blow description of that process as it seems like a tremendous amount of work and a far more risky proposition for somebody who isn't already set up to build and restore canoes. With my luck, I'd get it all put back together and have a worse trench than I started with. Any tips?
     
  17. OP
    OP
    chris pearson

    chris pearson Michigan Canoe Nut

    yes, but....

    Thats my thinking as well, I would pull the rib, and replace the planks, and still see the valley. It wasnt that big of a depression in the first place, I just want the hull to look really good after shiny paint is on it. Rollin is amongst the best in the business and is certainly capable where I might not be, just hope it doesnt bite me in the end. It was about 1/16" deep and didnt take alot to fill. Redoing the rib and all the planks that touched it just didnt seem worth it to me, right or wrong.
     
  18. Dave Wermuth

    Dave Wermuth Who hid my paddle?

    fwiw

    Depending on how severe the dip is. ( Make that was) I might have just left it. Except for a show boat of course. I also thought it sounded as if one rib layed lower and caused the 30" long 1/16" deep dip, like it was strapped and stayed that way. In that event one could remove the tacks and shove the rib down to push the planking out fair, but oops, now the rib's too short, so a new rib might be needed. It's not too hard to do. but your solution sounds as if you've fixed it and still have the correct color of the original rib and all that. there are many paths to canutopia. I always find useful ideas in these forums.
     
  19. bob goeckel

    bob goeckel Wooden Canoe Maniac

    or you could just end up with a nice pair of canoe shelves:D :eek:
     
  20. Todd Bradshaw

    Todd Bradshaw Sailmaker

    That would be my fear - ending up with a front half and a back half that weren't connected.... I'll take my chances with a 1/16" thick goo fill instead.
     

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