The corugated shape in cardboard question

Discussion in 'Fiberglass and Composite Boat Building' started by Boston, May 10, 2012.

  1. Boston

    Boston Previous Member

    Ok so I've been reading along for a while now and I've yet to see anyone build the classic cardboard section in a composite yet. I wouldn't think milling out the foam to fill the voids would be all that hard. I guess bagging the corrugated bit would be a pain in the *** but maybe not. I suppose it could be done by sandwiching the corrugated section wet between two sheets of cured, one for the inner and one for the outer.

    Anyway just an idear, thought that since cardboard was such a strong shape I'd throw it out there. Folks seem to go to no end of trouble to get things light and strong around here so I'm curious why the classic cardboard cross section seems to be absent from boat design ?


    do that out of carbon fiber and you'd likely have an extremely tough something :D
  2. Frosty

    Frosty Previous Member

    There is no diagonal triangular strength, it will collapse.

    Do you see any triangles there, just a sine wave.
  3. Herman
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    Herman Senior Member

    Do a lookup on "Structiso" which can be considered "composite cardboard" in a way.
  4. tunnels

    tunnels Previous Member

    It falls apart when it gets wet !! its cardboard !!!!
    Has some guys in a glass shop in Brisbane ,Queensland that tried making tanks using a simular material !! was back in 24 hours collapsed !! :mad:
    Im sure i seen some one with carbon sheets that look like that !!!! mmm have to keep looking !! AS a something yeah the shape is cool !!
  5. Herman
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    Herman Senior Member

    It is very obvious that you did not read the start post, or did not understand...
  6. latestarter
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    latestarter Senior Member

  7. PAR
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    PAR Yacht Designer/Builder

    Cardboard has been done. Interior doors for houses typically use cardboard to space the skins, which is the same thing. I also remember some expanding cardboard that was used as a honeycomb core back in the 70's and early 80's.
  8. waikikin
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    waikikin Senior Member

    I've never seen one in Aus but I've read about some skiff in the US that uses maybe trapezoidal logs glassed over in the bottom, kinda similar? Jeff.
  9. Herman
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    Herman Senior Member

    For the lazy basterds I have done a search on Structiso:


    I also recall our company having a table, made from epoxy-saturated cardboard, and carbon skins.. Was quite nice.
  10. Boston

    Boston Previous Member

  11. SamSam
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    SamSam Senior Member

    Carolina Skiffs patented a composite with straight up and down web like IIIIIIIIIII in the 80s. (it expired a few years ago.) There was a dispute between partners early in the venture, and one got muscled out. He started making boats with a WWWWWWWW type web.

    Here's the patent...

    The older patents in the 'References Cited' part are the forerunners and very interesting also.
    1 person likes this.
  12. Frosty

    Frosty Previous Member

    Repeat Post #2
  13. gonzo
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    gonzo Senior Member

    Small boat racers were using cardboard between very thin plywood in the 60's. A couple of friends of mine did.
  14. Frosty

    Frosty Previous Member

    Don't use corrugated cardboard as a gasket,--it leaks.

  15. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Some one gave me points for post #11. Thanks!

    I've posted details in other threads about the way Carolina Skiffs did their boats. It really works well for different applications. I copied their procedure making flatbottom jonboats and I still have one from almost 30 years ago, still solid, flat , strong and light.

    The same process can be used for panels for any purpose. The first mention I ever saw of it (which predated the Carolina Skiff patent and would probably have busted it if anyone took it to court) was an article in National Fisherman, where it was built in place in a large fishing boat and formed a structural bulkhead and at the same time a 12" thick insulated wall for their fish hold.

    I used the method in a mold, but a flat table can be used to give panels that can be cut to shape.

    Another good thing about it is it uses foam, but building foam can be used which bypasses the marine label and that huge markup. Even the CS boats used it, the type and supplier is mentioned in their patent.
    Polyisocyuranate foam. You can get the stuff at commercial roofing supply companies. Most of the time they will sell to anybody, not just commercial accounts. Compared to 'Marine' prices, for the same material you get a building construction price and usually a discounted wholesale price. Since the method uses small pieces, I bought odd lots, leftovers, and damaged stuff for even less $. I bet it was like 10% of 'Marine' prices.

    The process is real simple, and fast. And strong. When the CS guy started started taking his boats to shows and getting orders, he would turn one upside down and park the front wheels of his semi on it to show it's strength.

    I found a better site (Google) to look up the patent, where you don't have to download an application to see it. Fig. 2 gives a general view of the method, fig. 4 a close up.

    Here's a variation for v-bottoms...

    Here's another sort of impracticable "corrugated" idea...

    The partner I mentioned that used a WWWWWW pattern did it by putting a layer of upside down V shaped foams on the bottom of a skinned hull and then a lamination that formed the web. Then another layer of V shaped foam was stuck in between them, right side up, and a lamination put across the top to form the floor. The tips of the Vs were flattened and the bottom layer spaced so as to form flats and areas that would allow the web to tie the floor and hull together.

    Long rambling posts like this are usually barely comprehensible and passed over, but if understood, the method is cheap, easy and strong and has potentially a lot of applications for different things, marine related or not, nor is it limited to flat shapes. It sure worked well for the Carolina Skiff guy.

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