Old plywood boat. Epoxy / Polyester ??

Discussion in 'Wooden Boat Building and Restoration' started by Skookum, Apr 24, 2015.

  1. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    Old plywood boat. Can you actually polish a turd?

    My boat has one layer of glass fabric on the plywood hull and the inside has fabric as well.

    Without knowing for sure whether the original owner used epoxy or polyester when it was built what would be my best course of action in recovering the boat....inside and out?

    I've been doing some research here and see that epoxy is the stuff to go with but in this case with an old boat (1974) and unknown materials as far as the glasswork goes, can anyone shed some light on this?

    My best guess would be he used polyester as we are out in the sticks up here and I doubt epoxy would have been easily available.
     
    Last edited: Apr 26, 2015
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There's a couple of ways to find out, first is the color, which will be greenish if polyester. The second is the smell if sanded hard, which will likely have taints of solvent, if polyester. Pictures would be helpful, as the sheathing could have been added at anytime.
     
  3. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    Thanks for the response.

    Gonna go down in the am and keep puttering with it. If it were done in polyester am I doomed to continuing with poly?

    The reason I ask is that the inside of the boat is glassed around all the framing and stringers and I am doubtful that I could realistically get all the goop off.

    Also....some of the two part foam they had in between the framing did not expand and hardened into lumps and runs here and there.

    I'll try and get some pics.
     
  4. whitepointer23

    whitepointer23 Previous Member

    I have glassed over poly with epoxy and it stuck fine. It doesn't work the other way around though.
     
  5. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    Thanks.

    I just waded through 30 pages of the "materials section" trying to get a fix on this.

    I got the epoxy over poly thing and not vice versa. And if i got it right the fact that the poly does not adhere that well to the plywood should mean that if i can get down to wood I should be good to go (assuming exiting product is poly here.)

    Gonna "deglass" the boat and during this i should be able to find a few area where I can sand and see if I can get a whiff of any polyester.

    Definitely gonna go epoxy either way. Sorta too bad I just knee jerked a good deal on a big *** roll of mat. Thankfully they also threw in a substantial roll of weaved fabric as well....but what to do with a 500 foot roll of mat? haha
     
  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The mat isn't very useful with epoxy. It's a bulking agent used with lower modulus resins, like polyester and typically not needed with epoxy.
     
  7. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    So....Had a chance to look a little closer at a couple things today.

    Pulled up some fabric here and there and sanded the resin that was left. It definitely had that candy sweet resin smell.

    Some of the glass I pulled up was stuck to the plywood pretty well. It actually pulled some wood up with it here and there. Anywhere where there was water intrusion the glass came off readily but where it was dry it seemed to be pretty well stuck.

    [​IMG]

    [​IMG]

    I knew there was some soft spots in the bow area and also knew there was some poured foam in the bow as well. After pulling some glass and wood this is what was left more or less.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    I was a little dismayed to see that the plywood was fastened with what appeared to be drywall screws but anywhere the wood was dry the screws seemed solid and the joinery where I could see it seems "ok". Am thinking that when it comes time to flip the boat and reglass (assuming I get that far) I could refasten it with brass screws.

    [​IMG]

    I was most worried about the stem being inside the sodden foam. I excavated a bunch of foam from around the stem and it was wringing wet. (forgot to snap some pics) The top 8 inches or so of the stem is pretty punky with it getting less and less so the further from the deck it gets. I am hopeful that I won't have to replace too much of the stem. Am kinda thinking that perhaps some sort of sistering of the stem as well.

    Gonna completely remove all the foam tomorrow to get a clear assessment of the stem. I have been waiting to come across the proverbial straw....the bow section loomed in that way but I feel like it is repairable.
     
  8. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,005
    Likes: 356, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    A terrible thought occurred to me when I saw all that rot up at the bow. Where's the chainsaw !!! I visualized cutting off the 'nose', installing a waterproof bulkhead at the limits of the sound part, and making a nose-cone for it, to be bolted on. But you will probably get better suggestions.
     
  9. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    Interesting. I also initially had thought of a chainsaw, just to make the pieces easier to take to the dump. Once I actually got a look at the stem and saw it was not completely rotted out I felt a little better. That foam really did not do the craft any favours. Neither did the poor glass work. Many many pinholes.

    Part of what I found interesting was how obvious the problem areas were once the glass was off.

    Tomorrow I want to complete excavating the stem area and strip the glass along the keel to look for more evidence of water damage / rot.
     
  10. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,005
    Likes: 356, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    That glass seemed to be bonded fairly well, if it is taking ply with it when removed. I've seen it peel off pretty cleanly, but a lot of that could be the species of timber used. Epoxy should not delaminate, polyester only has a tenuous hold.
     
  11. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    Yeah. I keep reading how poly has no adhesive qualities. After sanding a few areas of resin and clearly getting the sweet smell I assumed was polyester I felt pretty safe "zipping" off the glass. Am slightly discouraged that I inadvertantly damaged good wood assuming poly had only a "tenous" grip.

    Gonna try and be a little more patient today. Hopefully I don't continue damaging the good areas in my ignorance.

    I guess I need to be a little more diligent in my research and yet not blindly make assumptions based on it.

    Will try my exploratory stripping of the glass with a heat gun today.
     
  12. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    Question before I head out.

    Any opinions on how the sopping wet stem is going to react now that it is being exposed to open air?

    I am operating under the assumption that the conditions are ripe for the process of decay and hope to mitigate these conditions as I can. I would like to retain the solid sections of the stem and sister "something" on either side of the stem to assist in the attempt at replacing the damaged plywood.

    Once the stem has dried and the punky sections are removed, would some product such as "git rot" be of any use in this situation?
     
  13. Canracer
    Joined: Aug 2009
    Posts: 621
    Likes: 9, Points: 18, Legacy Rep: 47
    Location: Florida

    Canracer Senior Member

    I'd be tempted to adjust the depth on a smallish circular saw and cut through the ply only. If that bad ply was removed carefully, it could be used as a template. Also, that would make the frames visible for inspection, and make room for the repair.

    Same deal with the transom. Disassemble and try to save something for a template. The "git rot" solution might be right in some areas but "git new lumber" should be plan A.

    Your pulling up some grain with the glass removal but it doesn't look to terrible. Those voids will have to be filled and faired before re-glassing, not impossible but it will be extra work and expense. A sharpish putty knife might slide under the glass and do neater work (not sure though.) Epoxy is light years better than poly, but poly can be encourage to stick so it's unsurprising that it's not falling off by the yard (if it was falling off, that wouldn't be a surprise either.)

    The heads of those screws look fine, but the threads might be shot. If you remove a couple dozen from different areas of the boat, you will get a better idea of how the screws held up.
     
  14. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Polyester has enough grip to remove the surface fibers of rotary peeled plywood veneers, particularly if the fibers have been soaked or saturated at some point in its life span. This is especially true with Douglas fir (what yours appears to be), where the summer growth gets pulled off, while the winter growth tends to remain, tearing the wood fiber all to hell.

    As others have noted, you need to do some more "exploring", digging out fasteners, foam and generally cleaning it down to her bones. Most folks would have dragged her off to the land fill by now, so . . . get 'er cleaned and naked (this is what I tell my other half all the time), so you can take a good hard look at what you've got.
     

  15. Skookum
    Joined: Apr 2015
    Posts: 22
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Canada

    Skookum Junior Member

    That's the plan at this point. To keep paring her back looking for the cumulative results that will necessitate the trip to the dump. Admittedly, I do have a soft spot for old bikes, boats and trucks.

    Gotta take a couple days off to work in town but next week I gonna try to keep poking about. So far the only thing it has really cost is the spontaneous purchase of the glass mat; fortunately the deal also included a big roll of fabric so.....

    I started posting the pics in the other thread I had started as this one has gone a little off topic. The bow looks a little skeletal now and the stem is in pretty rough shape.

    http://www.boatdesign.net/forums/wo...ation-mahogany-ply-jet-boat-1974-a-53113.html

    Anyway...thanks for the responses.
     
Loading...
Similar Threads
  1. fpjeepy05
    Replies:
    58
    Views:
    18,055
  2. Hercules
    Replies:
    12
    Views:
    3,882
  3. Nictoe
    Replies:
    0
    Views:
    135
  4. Graham Tapper
    Replies:
    25
    Views:
    1,238
  5. StandedInMx
    Replies:
    13
    Views:
    1,041
  6. DCockey
    Replies:
    0
    Views:
    1,649
  7. bjn
    Replies:
    9
    Views:
    1,820
  8. bentshaft24
    Replies:
    27
    Views:
    2,140
  9. Tiny Turnip
    Replies:
    63
    Views:
    9,498
  10. seymour2252
    Replies:
    2
    Views:
    1,619
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.