Anyone Tried This ????

Discussion in 'Fiberglass and Composite Boat Building' started by tunnels, Dec 11, 2012.

  1. tunnels

    tunnels Previous Member

  2. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    That's exactly what I posted about doing, years ago. Using cheap polyurethane foam from Home Depot and threading a strand of roving back and forth through the foam. Everywhere the roving went through allowed polyester resin to form glass reinforced pillars between the two glass faces to resist compression, and all the loops and exposed rovings on the surface of the foam tied the two fiberglass faces together, resisting tension, preventing shear and buckling of the outer laminates.
     
  3. Herman
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    Herman Senior Member

    Structiso is the same.
     
  4. gonzo
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    gonzo Senior Member

    Polyester resin will dissolve polyurethane foam. It will make a gooey mess. Also, the labor involved in doing something like that will more than offset the cost of proper foam. You could get a job at minimum wage, pay for structural foam and still have leftover for beer.
     
  5. tunnels

    tunnels Previous Member

    Thank you for the info much appreciated !! have heard of but never seen . Its really interesting stuff thats for sure !!.
    There some interesting reading in there Balslite section and answers to few mystries that have been happening over the years ! problems we never ever had and never heard of .Some of the old methods used in the 1970s/80s were pretty cool and all completely mad sense !!. I was fortunate and worked with really seasoned and very exsperianced guys at the time and all there thoughts and habit i cave carried with me ever since .
    When some thing works and works well all the time why change it !!
    Thank you again !!:D
     
  6. tunnels

    tunnels Previous Member

    Those kinds of problems are man made and very rarely product faults
    The glass stitched core is for a spacific project where skin to core bonding has to be really good and the old thing of peel and shear is a ever present problem !!
    If it was my project id be using Balsa 100% for the totall core . peel and shear dont happen with Balsa anything like Foams .

    Its about now after reading this mr watson will have the hairs on the back of his kneck standing up !So i await his reply !! :p
     
  7. Canracer
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    Canracer Senior Member

    Looks like a challenge to wet out.
     
  8. Herman
    Joined: Oct 2004
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    Herman Senior Member

    Using resin infusion the wetout is not difficult.

    On polyurethane foams: These are perfectly suitable for polyester resin. It is EPS and XPS foam that is not polyester compatible. PUR and PIR are very suitable.

    As a side step, there are polyester resins that are compatible even with EPS foams. (for instance EPS-Coat by Ce-Sense)
     
  9. El_Guero

    El_Guero Previous Member

    Penny wise and pound foolish?

    Pre-built laminate board, or pre-cut pieces, will be much cheaper than labor costs of manually stitching things together.

    Even at Chinese labor costs, unless it is a sweat-shop.

    Great to experiment, but why "fix things which are not broken?"
     
  10. Canracer
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    Canracer Senior Member

    El Guero, I think this is a pre-built board.
     
  11. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    You're right in that it was labor intensive to do that. I mostly did it to see if it would work, with a subtext of being extremely cheap as a result of lack of money, and large dislike of paying 8.5 times what something is worth just because it is labeled "marine".

    What I used was 3/4" foil faced, tan colored foam from Home Depot. Technically, it was polyisocyanurate foam, a form of polyurethane foam. From what I can tell on the internet, polyester won't melt polyurathane. I know for a fact it won't melt 'polyiso'.

    The foil faced foam was very light and friable, easily crushed and a lamination of plain csm easily came apart as the glass stuck to the foil but the foil peeled right off the foam.

    I tried it different ways, threading through from one side to the other and then back through etc. That was a nuisance because you had to pull the whole "thread" (roving) through for each stitch, which broke down the roving and was very labor intensive.

    Then I tried using short pieces that I just poked halfway through, which left a short end on each side. Next I tried short pieces where I poked the middle through, which left a loop on one side and two ends on the other.

    That led the way to the last solution which is what 3M does. I just layed a string of roving on the foam and poked it through every so often, leaving a line of flat threads on one side and a line of loops on the other. In 3M's photo, The lines with flat threads have loops on the other side and the lines of loops have flat threads on the other side.

    [​IMG]

    Once I got to the last technique, I made an 8' x 8' panel for my workshop that could be easily removed to bring big stuff in and out. I made a light frame of 3/4" x 1" sticks around the edge and then divided that in the middle horizontally and vertically so I had four 4' squares. The top half I divided up some more into 'windows'. I fitted in my stitched foam into all the spaces but the windows and then vacuum bagged it all with poly and 1 layer of 1 1/2 oz mat on each side. I ended up with a Japanese Paper Wall type of thing that is very light weight and has been in place for almost 20 years. I could easily bust through it if I took a run at it, but it has stood up to the wind and rain for that long and I only put stitched loops spaced every 6", as in 1 sq. foot would have 8 loops around the side and 1 in the center. I imagine with as much stitching as the 3M photo it would be very strong.

    I also used the Polyiso foam to build a jonboat similar to how "Carolina Skiffs" build theirs.
    http://www.polyiso.org/
    It's a very common commercial product that can usually be gotten at wholesale insulation prices, which is like half the price Home Depot would ever charge and 1/10 or 1/20th the price of "marine". They make it with or without the perforated paper face and in all sorts of weights and thicknesses. It's used a lot as the base for tarred roofs, so it comes in structural densities that can be walked upon by construction crews or used in SIPs, structurally insulated panels.

    As for working at minimum wage to buy structural marine foam being a good way to do it, it depends on what you need it for, how you go about it and how much it would cost. How much does a 4x8' sheet of 3/4" structural marine foam cost now? I have no problem at all with other people spending their money for expensive items, but if it's me, I start thinking of alternatives.

    I was looking at the foam in the 3M photo and thinking it looked like that flexible packing foam and sure enough, I think it is.
    http://multimedia.3m.com/mws/mediaw...vTSevTSeSSSSSS--&fn=3M RTM Core Data Page.pdf
    The stuff sounds pretty useful. Being flexible it can bend to compound curves and still have 250% more rigidity and 1000% more resistance to shear failure than other materials, and the prices even seem reasonable to me.

    See now, I immediately think of that cheap flexible foam that goes under laminated wood flooring and that with a little thought it wouldn't be hard to automate or semi-automate a way to stitch in roving as simply as 3M's is stitched in.

    It looks like the one guy could use it in his go kart bodies for a vast improvement and Frosty could try making a BBQ out of it.
     
  12. El_Guero

    El_Guero Previous Member

    SamSam,

    That was work!

    Did your test show that you could train local college kids to do it at minimum wage and it still be cheaper and close to the same quality as buying predone board?

    Would you trust it for the hull skin? Structural support? Or non-support features?

    Wayne
     
  13. Canracer
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    Canracer Senior Member

    Why all the concern about polyester compatibility? I thought that everyone was building with epoxy.

    (sub question: Is it the styrene in the polyester that causes the problems?)
     
  14. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Well, Wayne, I can't make much sense out of what you're asking.

    It wasn't work, it was something I did after work because I was interested in seeing how it would work.

    I did it almost 20 years ago and there was no 'predone board' like it to be bought. Whether college kids could be trained to do it is debatable, the new ones seem to be kind of stupid as far as actually being able to do anything worthwhile or having much sense.

    Would it work for a hull skin (?) or structural support or non-support features (?)? I think so. Did you read the 'applications' at the site I posted? Did you open any of the links posted?
     

  15. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    The styrene in polyester dissolves EPS and XPS.

    Back in the old days I mixed my first batch of gelcoat in an EPS coffee cup...
     
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