Coosa vs Nidacore

Discussion in 'Fiberglass and Composite Boat Building' started by rlilley, Jun 13, 2010.

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  1. rlilley
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    rlilley Junior Member

    Thanks for the input

    The reason I am going with coosa is the 40% lighter weight. I have removed aprox 650 lbs of plywood so far. That counts the floor, wall paneling that was 3/8 thick and built in furniture.

    Bob
     
  2. apex1

    apex1 Guest

    I understand your motivation and I am not completely against your plan.

    But, Bob, you have to comprehend, that your choice of material has some severe disadvantages over the claims of the manufacturer.

    It will most probably not hold up for the same number of stress cycles (known as fatigue), as a simple ply would. It is by no means rot resistant or free of mold build up! It is not water tight if you do not encapsulate it the same way you would encapsulate ply.

    So, where is the advantage?

    200 gram, 800 gram per m² ???

    believe me, we have proven ALL the stuff, the industry is trying to sell us since ages. And we have fallen back on our feet almost every time.

    Plywood is one of the strongest, best predictable, and one of the most worthwile materials in boatbuilding.

    It has to be grade A marine ply, it has to be encapsulated completely in PU, Polysulphate, Epoxy, or even Polyester*, then it will nor fail for over 30 years.

    *as a sidenote: the bond between poly resins and wood is never sufficient, so that will not hold for 30 years.
    and that is the reason you have to replace the crap.


    Regards
    Richard
     
  3. kach22i
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    kach22i Architect

    It is your boat, do what you want.

    If you don't want to get into vacuum bagging (honeycomb), and want to save weight over marine plywood then Coosa seems like the only practical choice.

    Get some samples of all the materials in question (typically free), play around with it (epoxy resin it) and then feel confident in your decision.

    Similar thread, you might want to contact Seajay and find out what his experiences was three years ago.
    http://www.boatdesign.net/forums/fi...ing/foam-core-deck-cabin-bulkheads-19034.html
     
  4. kach22i
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    kach22i Architect

    Not that I doubt your word, but I Googled "Coosa failure" and several other related search terms such as moisture and weight and could find nothing on it posted on the Internet.

    One exception, Defiance Boats seems to love the stuff.
    http://www.defianceboats.com/content.php?p=why_defiance/why_defiance.html

    Richard/apex1, please help me find evidence to back up your commentary.
     
  5. apex1

    apex1 Guest

    George,

    coosa is a PU foam. PU foams have a water absorbing capacity of 3 - 5% (vol.) by nature. The fibre reinforcement is a good helper for water intrusion.

    All core foam materials known by so far, can build up rot / mold under certain conditions.

    Of course ply has far worst properties, but both materials need to be encapsulated / reinforced, then the advantages of the foam are minor, but the cost is three times higher.

    A wooden core can be treated with copper naphtenate prior to encapsulation to prevent rot and mold. PU / PVC not.

    Regards
    Richard
     
  6. Ilan Voyager
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    Ilan Voyager Senior Member

    "Plywood is one of the strongest, best predictable, and one of the most worthwile materials in boatbuilding.

    It has to be grade A marine ply, it has to be encapsulated completely in PU, Polysulphate, Epoxy, or even Polyester*, then it will nor fail for over 30 years."

    You're right Apex (but I add that I wouldn't never use polyester, as it needs the same amount of work as epoxy, less forgiving, and won't last. The saving on the resin cost versus epoxy is too low to accept the drawbacks)

    When you're a home builder, it's better to go to the simplest way because with a simple tooling you can get 100% of the quality, with the the least work. And epoxy-plywood is a well proven technique with excellent results.

    Foams and honeycombs are a step further, need good knowledge of the engineering of the material, very good craftsmanship and it's very expensive. Too many occasions of big mistake.

    And I can say by experience that if you have not the money, tooling, engineering and some "maestria" of composites, the results and weight savings are very deceitful, and it's more depressing when you compare with the cost and the work involved.

    Besides, if the polyethylene of the Nidacore, and the PVC of foams are stable, PU foams are not known for their long-term stability, and do "rot" very well in presence of water.
     
  7. apex1

    apex1 Guest

    You noticed my sidenote Ilan?

    I never recommend poly for anything but a newbuilt!

    Regards
    Richard
     
  8. kach22i
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    kach22i Architect

    FYI: if you guys like to play around with materials, order up some samples of Monopan. I cannot wait to use the stuff on my hovercraft.

    http://www.monopan.ca/

    I suspect the minor porosity between the cells and the outer surface to be very, very low.

    Bob, monopan is translucent so it could act as natural lighting (skylight) if clear sealed. See the award winning applications on buildings by doing a Google image search.
     
  9. kach22i
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    kach22i Architect

    Is Coosa an open cell or closed cell PU foam?

    I am very leery of open cell, be it on building walls/roofs or on boats/hovercraft.
     
  10. apex1

    apex1 Guest

  11. kach22i
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    kach22i Architect

    Of course closed cell is better, it's used unprotected for concrete ground slabs (against the moist earth) and on basement walls on the wet/earth side of the damproofing.

    I still want to see some documented cases of Coosa failures. Closest thing I could find on the Internet is a double section transom which was designed to trap water (design flaw not material flaw).
     
  12. kach22i
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    kach22i Architect

    MONOPAN
    http://s184.photobucket.com/albums/x295/kach22i/Hovercraft Random Pics/
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    They clear tape the edges to lock in the tiny specs of debris after cutting. This could mean it's messy to cut, or that you need to static wipe everything in sight.

    The knuckle knock test has a wood-like sound, not the glass/acrylic sound of factory glassed and epoxied Plascore honeycomb.

    No flex in my small sample but would believe that it is more bendy than other honeycombs and would not snap. In fact there are videos on the Monopan website which show it returning to it's original shape after impact.
     
  13. Ilan Voyager
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    Ilan Voyager Senior Member

    Yes I saw and we know that we agree that polyester is for GRP and nothing more, I just added my salt grain.

    I've used Nidacore and it's good stuff. Originally designed in France for making bridges and highways. It's the easiest honeycomb to use, a hot wire for cutting is very helpful.

    Just needs a bit of engineering to take care of its properties (like any material).

    It's incredibly resilient and withstands a lot of abuse. Coupled with a very good isophtalic polyester resin like the Reichhold 50some and triaxials, that gives one of the best composites within the ratio price/strenght/weight.

    A bit of flexibility is not a defect if the material is strong. That permits to dissipate the stresses, specially impacts. The Lord method (controlled flexible structures) is based on that, and that works very well on very fast boats.

    But like all honeycombs Nidacore needs a good craftsmanship and sharp engineering. So a home builder has to stay in simple methods, easy to use so he can get 100% quality. I'll add that plywood is the fastest method for a home builder with minimal tooling on a one off project. Investing in good light marine plywood will be cheaper than foams, honeycombs and tutti quanti. You can find pretty good meranti and okoume plywoods at reasonable prices in the States. Do not base your opinion about plywood on the miserable examples of heavy crappy fir plywood covered with a gooey of cheap fiberglass and low quality polyester.

    In other words, it's better to get all the qualities of a material, even if it looks "inferior" at first sight, than to use a theoretically superior material, and to be unable to get all its qualities.
     
  14. kach22i
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    kach22i Architect

    I used a little bit of MDO plywood on my hovercraft (under hull landing pads epoxy coated). It was incredibly light after being weathered outside for a couple of years, not sure why.

    Has anybody used MDO in boat building?

    Found this:
    http://members.fortunecity.com/duckworks/2005/0515/index.htm
    NOTE: Kiln dried wood has a higher moisture content than Coosa will even absorb under the worst of conditions. I'm going to order samples and do some in-house testing myself.
     

  15. kpiazzisi
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    kpiazzisi Junior Member

    I am in the middle of redoing my stringers and deck with Plascore Honeycomb product. Yesturday I wet out a layer of CSM 1.5 Oz one each side of the 4 x8 sheet. I DID NOT VACUUM BAG IT. I used Poly Boat Resin. I followed the manufactures instructions. I rolled one quart onto the board. Next, I laid the CSM down. Finally I wet out (roller) the remaining 3 qts. onto the pannel. I had no air bubbles, extra resin, etc. The sheet is light and strong. I may even laminate a layer of Roving on each side to make it even stronger. I am not a boat builder, and had no problem accomplishing the task.

    I was able to get the 4x8 sheet for < $60.00 which is about the same as Marine Grade Plywood. I didn't go with Epoxy, because sealing the wood was not critical (no wood to seal). Yes epoxy has better adhesive strength, but most boat are Poly and repairing with two like material has it's advantages. The cost of Marine Grade wood and Epoxy is just as expensive as Boat Resin and a Honeycomb product.

    I did not use the vacuum process. I talked to the Nida-Core Tech Advisor (probably their Engineer) and he did not mention I needed the vacuum bag process. If someone on hear feels that is necessary then please explain.

    I have attached PICS of the 4x8 sheet after being laminated, and a bulkhead that I cut out of the laminated 4x8 pannel. I will also mention that it was a breeze cutting the bulkhead out using a jig saw.

    TY
     

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