Polypropylene honeycomb panels for hull construction?

Discussion in 'Materials' started by harry tams, Feb 22, 2010.

  1. brian eiland
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    brian eiland Senior Member

    ...more on my hoped for utilization of this plastic honecomb material....

     
  2. brian eiland
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    brian eiland Senior Member

    So here is Groper's initial reply to my postings...
     
  3. brian eiland
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    brian eiland Senior Member

  4. brian eiland
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    brian eiland Senior Member


    Originally Posted by groper
    Brian- I believe you asked me about polycore once before. I explained that a friend of mine is building a pacific 40 catamaran entirely from polycore near where I live
    .

    Is that Pacific 40 the same cat design as the Solitary Island Catamaran?

    Has he had that project under way for quite a while? I believe Solitary Island stopped building their kits a number of years ago due to financial difficulties of the boat market in general.


    Originally Posted by groper View Post
    It's more time consuming to and less friendly to work with compared to foam core. Any joins or edges need to be decored and back filled first before bringing the join together , gluing and glassing over so there is an extra step of decoring and back filling not the mention the extra resin to fill the core along the joined chine. If you don't do this there will be air bubbles all along the Chine
    .

    That is if you have a hard chine in the hull design.

    I believe Solitary Island had a solid glass 'shoe' below the waterline?


    Originally Posted by groper View Post
    The next issue my friend had was out gassing due to so much Trapped air in the polycore. He always had to wait till Temps were falling to get a good glassing job done or the dreaded air bubbles would arise
    .

    That's interesting

    Wouldn't out-gassing (of core materials), and trapped air be 2 different things.? There can always be 'trapped air' in any fiberglass layup procedure, regardless of core material?

    I would be particularly concerned if it were the chemical make-up of the core that might be producing gassing after layup.

    Originally Posted by groper View Post
    So No- I wouldn't use it except for perhaps again- certain key areas in the interior such as small bulkheads with no cutouts etc made from pre-made panels to save cost. Perhaps the front 3 watertight bulkheads for example. Certainly nothing outside like a deck which is full of leak points from all the hardware mounted all over it.
    .

    Agreed, decks have many potential leak points, and regardless of what cores they are built of one has to take extra precautions at mounting deck hardware.

    Balsa cores are off my list as there is just too many documented cases of water following the bond-lines and eventually rotten decks.

    Lots of foam cores do not hold up well in the heat of sunlight, and tropic conditions.

    I believe I had read in a number of cases that bond line failure of Nidacore type products did not occur if the job was done correct? And another thing that had impressed me about the Nidacore type product was its 'ductility'. This property helps the sandwich structure stay intact, and not delaminate so easily.


    Originally Posted by groper View Post
    And of course because it not infusion compatible, you can't use it to make large panels yourself via KSS...
    .

    I believe i also discovered there were some examples of utilizing these core materials in an infusion process? I just can't recall right now.

    Thanks for bringing this to my attention. I will have to look back and re-evalute
    Brian
     
  5. groper
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    groper Senior Member

    Brian - i also edited some of those previous postings to include more information. Please reread the following;

    When i say "chines" i dont just mean underwater chines of a hull. I mean anywhere there is a change in plane between 2 panels. These exit everywhere - deck to cabin, hull to deck, chamfer panel to floor, a multitude of places throughout the interior and furniture, the list is endless... and everyone of those edges had to be decored and backfilled before glass taping around these edges or "chines" as i call them. If you dont you end up with 2 abutting polycore edges which you cannot remove all the air bubbles from when you attempt to glass around that edge. Think about it - often these edges dont fit perfectly, so the panels must be shaved back a bit to get a good fit before glassing together and even the simple process of sanding an edge flush is difficult with polycore as the plastic doesnt sand down easily. If you attempt to grind it - it melts etc. Then your left with this open cell edge which you need to round off so the glass will wrap as you cant glass wrap a sharp edge. But you cant round off open ended cells - you end up with a rough jagged edge which is full of open cells to wrap. So the process my friend used was to decore and back fill after he trimmed panels to fit - then round off the cured bog edge and glue/glass around it. With foam core panels none of these difficulties exist. You can trim it, cut it, rout it, sand it, plane it, grind it, and you can glass around them directly as the foam core itself can be neatly rounded off (usually with a router) and glassed over directly. Using routers was difficult with polycore as the router bits tend to rip out the plastic rather than cut it. Everything about the stuff is just difficult..

    The major issue above all else tho, is its not compatible with KSS! You cant infuse PP core or the cells fill with resin. Flat table infusion allows a single worker to infuse a giant panel (upto 100kg of resin )with a perfect finished surface in a single day! I was having breakfast in the morning before starting with a bare table, then laying everything up and infusing my topsides panels before clamping off the lines and going to lunch! - You cant beat that in terms of man hours by any other method, period.

    And yes - the solitary island (pacific 40) uses an infused hull 'shoe" with a foam core which is all below waterline as i doubt the designers felt polycore was suitable below waterline either - that and its not an efficient material to attempt to obtain that shape with in terms of time. They used double cut foam which conforms to the compound curved mold and infused it. So despite foam being more expensive - it allowed them to produce the part quickly and saved time = $$$.

    You can (and people do) use polycore anywhere on boat. I wouldnt use it below waterline for fear of water migrating between cells in case of damage. The solitary island uses it everywhere else including decks. Every peice of hardware mounted to it must be carefully decored and backfilled so water never gets into it. Basically need to treat it the same as balsa. Except balsa is easier/quicker to work with...
     
  6. brian eiland
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    Bondline(s)

    ...from another forum...
    This bondline between the skins and the core is certainly an important one for any core/sandwich construction material, and these PP cores depend on a very viable thermo-fusing process. Two questions came to me recently,
    1) that observation above about an early production PP core that might have had 'furry scrim' material applied
    2) Chinese made stuff, (that I always question quality). That is one of the reasons I had asked about the builder of that cat in Thailand that was experiencing problems....where did their PP core come from?

    One item in PP's favor is its ductile nature that would keep it from cracking along this bondline as do quite a number of rigid foams might do when slightly over stressed.
     
  7. groper
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    groper Senior Member

    If i had a bigger budget, or was a commercial catamaran builder - i would build a flat table or floor mold large enough to infuse the entire deck of the design i intended to build.

    Then i could infuse, the entire deck in 1 shot. The entire bridgedeck floor in a second shot. And, ALL 4 topsides panels in a 3rd shot.

    Each one of the above shot - could be setup and infused in no more than 2 days per shot by a single experienced worker. The deck would be complete with all high density inserts for cleats and hatches etc.

    Its costly because you need alot of floor space and an overhead gantry to lift such big panels around the place... fine for commercial builders but a bit much for low budget home builders like me...
     
  8. groper
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    groper Senior Member

    i dont have any issue with the mechanical properties of PP core panels. They seem plenty tough and strong enough to me - and testament to this is many PP boats going strong provided they are built carefully. The issue is the man hours it takes to use PP core, it may be less expensive at the end of the day, in terms of time = money, to use a more expensive core like foam...
     
  9. brian eiland
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    brian eiland Senior Member

    Pacific 40 vs Solitary island 40

    Hi Groper, ...greatly appreciate you joining this subject thread.

    I've attached two PDF's, one I had for Pacific 40, and one for the Solitary Island vessel. It appears that the Pacific 40 vessel preceded the Solitary Island attempt to build these kit boats.

    And it appears as though the Solitary Island guys adopted a little bit more sophisticated method of joining the polycore panels together?

    "the Pacific 40 kit Catamaran Reborn as the Solitary Island 12"

    So your friends' boat might be one of those very early ones?

     

    Attached Files:

  10. groper
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    groper Senior Member

    Brian- please know that I have intimate, first hand knowledge about this stuff. I'm not an Internet armchair critic.

    This kit boat from Mark Stephens is supplied with half boat length PP core panels in addition to the infused foam core shoes. The panels are made like so;
    1. They use a wet out machine to wet out full width rolls of glass and lay it out on a flat table.
    2. They layup the sanwich panels with PP core and between panels use a layer of plastic to separate each panel from the one below it in a stack.
    3. Once multiple panels have been layered and stacked, the whole thing is vacuum bagged and left to cure.
    4 . It takes 3-4 people working like crazy to get this done using a slow cure epoxy.
    5. The surface on each panel is pretty good, but not good enough to paint directly, it requires a little filling of pinholes and feathering of glass overlaps etc which still means that every square cm of surface area still need to be sanded, faired, primed, and painted - a huge amount of work in itself.
    6. The panels are cnc cut and packed into a container for shipping.

    The boat is then built as per a Duflex build- the difference is you only have to join once along the length of the boat rather than every 4ftx8ft Duflex panel. However there is no z joint in the polycore panels so taping together leaves a raised bump to fair out.

    All of the points I raised about rhe difficulty in working with PP sandwich panels are still valid. Where do you think I learned all about it? - it was through the building of this very kit which is happening 15mins from my house and have become good friends with the builder. Weve helped each other out on numberous occasions...
    So far he has used an enormous amount of fairing compound and highbuild primer - over 500kg so far, and has employed 2 full time fairing/painting professionals for 6 months.

    I will say tho however - the standard to which they are building this boat, is equal to or better than, a professional boat yard. When this boat gets its final coat of paint it will look absolutely mint. This is also in part why its taken 5 years full time...
     
  11. groper
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    groper Senior Member

  12. brian eiland
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    Hi Groper,
    I've been away from the forums for awhile with some sort of flu, and not over it yet., so haven't done much follow-up on our subject. But I did just 'rediscover' this other subject thread that had lots of good material submitted by yourself.
    http://www.boatdesign.net/forums/fiberglass-composite-boat-building/polycore-21319.html.
    Your contributions are significant.

    I'm going to look back thru both subject threads when I get to feeling better, and perhaps after my planned visit to Thailand for 2 months.

    BTW, did you see this subject thread and the problem that power cat experienced in Thailand with core and water.
    http://www.boatdesign.net/forums/materials/repair-water-core-material-fibreglass-boat-56743.html

    I met with a boat builder there years ago, RB boats, on a couple of occasions, and saw where he was using a 'nidacore like' product in many of his constructions. I don't seem to recall any major problems he has had with the boats in regards to core problems?
    I was trying to find out if that power cat with the water problems might have been built by him, but thus far have been unable to get the gentleman who posted that subject thread to respond any further??
     
  13. brian eiland
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  14. groper
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    groper Senior Member

    The problem with this material is the ease of which you can work with it- or lack thereof. Like is said before, I don't have anything negative to say about its structural properties.

    It's also not compatible with infusion, which is a huge loss in terms in terms of being able to efficiently layup the structure of a yacht. Infusion is being embraced by all leading manufacturers now , and I can tell you from personal experience that's it's a lot quicker in terms of man hours to use infusion processes. There's a reason so many boat builders have gone overseas and it's entirely driven by labour costs being such a high component of boat building.

    Polycore is not conducive to efficient building hours. Yes it's cheaper to buy compared to foam, but it'll cost you more in labour...
     

  15. Sunsine
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    Sunsine New Member

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