2005 43’ Trawler w/ Marine Plywood Core in Deck and Pilot House – Major Concern?

Discussion in 'Boat Design' started by TJB_Patriot, Feb 16, 2011.

  1. TJB_Patriot
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    TJB_Patriot Junior Member

    We are considering the purchase of a 43’ 2005 "Cape Islander" custom built trawler, 40,000lbs with 8-9 knot cruise and 4.3gph fuel burn. The boat has the layout and equipment we desire.

    Today we learned that the coring material used is ¾” marine plywood, hull is 100% glass and has been barrier coated. The entire boat is glassed with Isophthalic Polyester Resin. We're concerned about the deck being cored with ¾” marine plywood due to the materials tendency to transmit water if introduced. The boat was built in 2005 by a quality shipyard.

    I’m also very concerned about future resale value. Although we intend to keep the boat for 10+ years you never know what will happen forcing us to sell sooner.

    How will future buyers react to plywood cored deck and pilot house? Is our negative reaction well founded or are we responding differently then the typical buyer?

    Any opinions of the pros and cons of using marine plywood as a deck and pilot house coring material?

    Thanks
     
  2. gonzo
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    gonzo Senior Member

    There is nothing wrong with it. Test it with a moisture meter.
     
  3. TJB_Patriot
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    TJB_Patriot Junior Member

    Would You Design Modern Trawler Deck with Plywood Core

    After giving my question additional thought perhaps I should have asked it in another way to gain additional insight.

    Question:
    Would you design a 43' trawler, built today, with a plywood cored deck? If so, why would plywood be the material of choice?

    Thanks
     
  4. FAST FRED
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    FAST FRED Senior Member

    "Would you design a 43' trawler, built today, with a plywood cored deck? If so, why would plywood be the material of choice?"

    Its way cheaper to get a passable flat surface on a deck or pilot house with plywood than build a mold that is flat.
    And easily allows for running upgrades from owner feedback.

    Many of the old Taiwan boats used house ply , not marine ply , which was OK till they poked holes in the thin GRP covering to add a "teak deck" .

    The ply structure may remain intact , if you simply consider the area to be wood , not "Chinese composite".

    That means being willing to understand that all bedding compounds have a limited life and must be on a Sked for replacement , before the water starts to eat the plywood.

    Deck fittings , windlass, windows and trim will need to be looked after every few years.

    FF
     
  5. viking north
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    viking north VINLAND

    I am familiar with the name Cape Islander as a style not a trade name. In your case is it a trade name? When you say custom, many "one off" are also labeled custom. What i am getting at is, is it a trade name factory built boat, if so it is a big plus for info. During my past experience in boatbuilder/repair I have often phoned up the factory stating i had one of their boats in the shop, complimemted them on their work, and just point blank asked them was there any problems in this area or that area that i should take a look at for the customer while i had the boat in the shop. I was always amazed with their honesty and excellent feedback. An additional path of course is to track down other owners and get their input and you can make use of all the boat forums to do this as well as visiting marinas. As mentioned above ply core is commonly used and my concerns would be the inital quality control of the build, any after factory installs that required cutting thru the protective grp coating, however minor as a small opening to moisture travells a long way over time, any damage that resulted in the same, was the vessel ever flooded, partially sank or fully sunk as the inside grp coatings protecting the ply are usually less stringent in their applications. This is a big cash outlay in life so take your time do good research, hire a good surveyer, often while he will not find any majour problems he will save you his fee in pre buy repairs, or a bargening leverage of such for a better price. Geo
     
  6. gonzo
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    gonzo Senior Member

    I would definitely use plywood core on a new build. It is relatively cheap, easy to make flat or lightly cambered surfaces, it holds fasteners well, and it doesn't collapse like foam when you tighten bolts.
     
  7. viking north
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    viking north VINLAND

    Exactly, while moderately heavy i think it is one of the most economical, strongest, easy to build with, easy to repair, but it will rot, the key is moisture proection at the inital stage of the build and continious protection for any add ons after. If there is moisture in the ply core or any core it will show up during the first cycle if the boat is taken from a southern low to no frost climate into a northern definite freeze thaw home.Geo.
     
  8. TJB_Patriot
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    TJB_Patriot Junior Member

    Built By a Quality Canadian Shipyard

    The boat is a Cape Islander style that was built by Atkinson Shipyard a commerial builder in Canada, in operation since 1905 I believe. It has 1200 hours on her to date and has traveled from NY to FL and Canada, very sea worthy vessel. I have talked with one owner of an earlier model but that was cored with Airex. They were very happy with the boat and still own her after 17 years. My understanding is that was the last boat the builder used Airex in due to expense. Choosing to go back to marine plywood which they feel is a very good material for thius type of vessel and were very nice to speak with when I called stating they beleive the boat will be in operation for decades as many of their build have.

    Sounds like 3/4" marine plywood is okay as long as very well cared for. I still have some concerns about affect on resale but not sure how much of an impact that will actually have.

    Thanks
     
  9. u4ea32
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    u4ea32 Senior Member

    Wood should never be a structural part of a boat. When (not if) water gets in ther, the structural properties go away, and its very expensive to get them back! Not impossible, but almost certainly it will cost more to replace that rotten plywood than the boat is worth.

    Gonzo mentioned some good reasons to consider using plywood, but these reasons are only valid if the intended life of the boat is less or equal to the time it takes plywood to rot (which is not long).

    For example: I own a 10 year old Fountain powerboat. Its entire structure is foam + triax + vinylester. EXCEPT for the transom. The transom is about 2" marine ply inside of triax+vinlyester. The only part of the boat that is rotten is the transom. I just had to have the entire transom rebuilt, this time with high density foam!

    Talking with many quality builders worldwide, nearly all concur: using wood is a little cheaper, and results in a much shorter life span.

    Wood core (balsa, ply, cold molded, timber) is a very bad idea in a boat unless initial cost is paramount and life expectancy is not considered. That's why these materials are common in production boats: it gives the appearance of cost savings, when in fact it simply increases the depreciation rate and long term total cost of ownership.

    Regarding ease of construction: another red herring. Modern fiberglass construction almost universally uses molds. Even one off boats use molds, lots and lots of one-time special purpose molds for counters, cabinets, deck furniture, hatch gutters, structural grids, and so on. You'll build a mold for the hull and deck too, for sure. Its far, far easier to get the shape you want with door skins over particle board frames than using structural members of the actual boat, like plywood for a deck. Therefore, foam is easier for construction than plywood.

    Plywood is too stiff, so it does not conform as well to the mold, so you don't get a good bond between the plywood core and the fiberglass surface that is against the mold.

    The core does not give the strength, its the "I" beam effect, where the skins provide all the strength, and the core just keeps the skins apart by the correct amount. When the bond between the plywood and a skin fails, the plywood becomes (almost) useless, it does not impart (useful) strength. When the plywood gets soggy and does not keep the skins properly separated, the same situation occurs.

    So: only use plywood in design and construction, and only buy a used plywood cored boat, if initial purchase price is all you consider. For an owner, that is RARELY a reasonable choice. For a company that sells to fools (LIKE ME ;) that can be a reasonable choice.
     
  10. gonzo
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    gonzo Senior Member

    I am still building and repairing wooden boats. I completely disagree, and have centuries of shipbuilding success to back me up. Boats that are more than fifty years old and have been worked hard come in for repair with most of the structural members in good condition.
    u4ea32: You don't have any understanding on how plywood is used as a deck core. The deck is built in plywood and then laminated over. It allows, among other things, an economic way of customizing a design. Plywood lasts for a very long time. The proof of this is right over your head. The house you are in most likely has plywood siding and roofing. Houses never get the maintenance that boat do and are always in the weather. Claims about plywood rotting fast were used by fiberglass boat salesmen from the start. The facts prove them wrong. If you want hard data, read "The Wood Manual" that the Wood Institute in Georgia produces. It is the official data by the US goverment.
     
  11. viking north
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    viking north VINLAND

    Ok Patriot i thought as much, you have what we call a modified Novi Hull an excellent sea boat. Sounds like you have done good homework but i would have a good survey done, it's worth the investment. Airex would have definately been a better core but it would have been reflected in the price. If I read you correctly the hull is solid FRP and only the decks cored in ply. This reduces the risk greatly and once the surveyer has done his job which is to pay particular attention to this area I would think your concerns would be put to bed. In todays economy and projected futrue market for used TOYS if you can recover 50% of cost you'd be doing well. Likewise in todays economy it's a buyers market and with the flood of all TOYS (boates, bikes, whatever) personally The price would have to be almost too good to be true, I'm thinking 1/3 of orig cost. especially a boat form a company no longer in buisness. Ply is ok, have it surveyed by a top notch surveyer, don't skimp on price here, and if you are as old as I am buy your dream, ride it hard on enjoyment, whats left over they can build you a fine box and future return on investment becomes irrelevant. Geo.
     
  12. mark775

    mark775 Guest

    Just so that you don't think Gonzo is an anomaly, I agree completely with him and have to say that, speaking in the most polite terms I can now muster, U4ea32 is talking out of his ***.
     
  13. Tad
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    Tad Boat Designer

    Tell that to millions of wooden boat owner's..........:)

    This is like saying don't use foam because it might sheer or delaminate (both these things really happen!) or don't use steel because it can rust.......rubbish.....
     
  14. TJB_Patriot
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    TJB_Patriot Junior Member

    Thanks for the Input & Insight

    Thank you everyone for the comments, insight and feedback.

    The information provided has given me great insight into boats with a plywood core deck and alleviated some of my concerns.

    Viking North
    Yes the hull is solid FRP and very well constructed. I agree with the pricing comments and should we decide to move forward I’ll be working on formulating a fair and appropriate offer then lining up a top quality surveyor should it be accepted.

    Thanks again everyone and of course should you have any additional tips or comments please keep them coming.

    Thanks
     

  15. u4ea32
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    u4ea32 Senior Member

    I'll stand by my comments, but I respect that others may disagree.

    Its a complex trade space. Initial cost is often a big deal, aesthetics are often crucial, and very many other issues are important to different people.

    Yachts are toys, nobody really NEEDS one, and so the buyer's choice is totally up to them.

    Gonzo and Mark, I'll stand by my statement that molds are easier to build than plywood structures. And I'll stand by my statement that building a boat or boat component from plywood and then glassing it over is simply an inferior way to go: more work, lower quality (heavier, more flexible, ...), and less durability.

    Also, Mark, perhaps my explanation was not clear, for which I apologize. Hopefully this time I am more clear. Nothing here is coming out of my a**, its all foundational structural engineering. It might seem counter-intuitive that one really wants a flexible core, but its very well founded on theory, experiments, and experience in the marine and aerospace industry. A core just keeps the skins apart by a consistent amount (stiffness), and allows forces to be distributed to as large an area within the skins as possible (strength).

    I agree, Tad, that delamination does occur, regardless of core material. However, you certainly know that there are two key reasons for delamination: 1) lousy initial bond during construction, 2) exceeding the strength of the core-skin bond during operations. BOTH are strongly affected by the stiffness of the core: the stiffer the core, the more likely delamination occurs. As I mentioned before, a stiff core is prone to areas of poor initial core-skin bond due to the inability to get consistent core-skin pressure during construction. During operations, a stiff core causes stress concentrations, increasing the likelihood of locally breaking the skin-core bond.

    Let me turn this around, so maybe I learn something too: Why would anyone use plywood in a boat to make a "better" boat? Define "better" any way its important to you.
     
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