DIAB Foam

Discussion in 'Materials' started by MarineSurvey, Sep 23, 2009.

  1. themanshed
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    themanshed Senior Member

    Yes but it would be local if proper construction methods were used and easily repaired. Many times only the outer skin will be holed leaving the inner skin intact. I think you have epoxy sheathing over ply coming off much more then the problem with foam. Foam will absorb impacts more then wood but they all have breaking points. A much more serious problem with wood products is dry rot; you do not have that problem with foam.

    Wood and modern age epoxies are excellent material, but you are somewhat limited to square and angular designs. But if you want to give your lady curves foam works best.
     

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  2. rwatson
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    rwatson Senior Member

    I have comitted to foam for my next project, hence my interest in the trimaran build.

    In making this decision, I have tried to research all I could on different boatbuilding techniques.

    I hope a lot of what you say is true, but one thing that seems to be mentioned from lots of sources is that timber (plywood etc) absorbs more impact than foam ever can, is less prone to heat fatigue and of course is much stronger.

    The factor that pushed me to try foam is lower weight and lack of water absorbtion.

    The term "proper construction methods" is also fraught with peril. DIAB state that hand layup will produce satisfactory results in their product information, but then you read that hand layup is the most problematic method of applying glass from one of their chief chemists.

    You have to watch the "spin" from the manufacturers.

    I guess Iwill have to try it to see.
     
  3. themanshed
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    themanshed Senior Member

    Most builders in Florida have gone with foam because of the problem with rot in a tropical climate. Make sure you pick quality foam. There are two methods the vertical strip method like the newer Farrier designs from the bilge to deck and the horizontal strips like my method. The best bet on horizontal strips to cut the cove and bead on the strips. American Eagle www.eagleamerica.com sells a combo router bit so you just have to purchase one bit the part number for the 3/8 bit is P14-3425 @ $44.97 US. This allows the strips to blend nicely on a curve for less fill & faring. I'll give you the heat fatigue and also condensation plays into decks. Boats with large decks often use Balsa core for the decks then edge it out with foam to aid in the faring. It depends on whom you read in what can take hits better foam or wood and which is stronger. The density of the foam and type of laminates play heavily into the factor also.

    If you do the One-Off method building with foam it is great and the bond between the foam and skin is very good. I used West System epoxy with a bit of 407 powder mixed in to make a runny bog for the first layer of epoxy between the foam and carbon. The bog with 407 makes the lay-up stiffer fills any voids and gives an excellent bond. All other layers were just straight epoxy with the carbon. If you use more then one layer of fabric in lay-up vacuum bag. A vacuum compressor cost about $150 US from harbor freight sales for a good pump. I built my own tank.

    Right now I'm messing with the repair of a carbon A-Cat mast, most shy away from such a repair, make sure if you use carbon to paint it. Direct sunlight deteriorates carbon fiber.

    Good luck let me know if I can be of any help. What design are you going to build; purchased or your own? I’ve collected a few tips on the way
     

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  4. rwatson
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    rwatson Senior Member

    Your web site has given me a lot of help already, but there is lot more to learn.

    My project is a 28ft trailer/sailer, and I have minimised the foam work - I may not even need to vacuum bag.

    You can see that there are two "mould lines" around the hull. The sides are made up of two developable flat panels, while the bottom of the hull will be done in a female mould with no foam. I am planning on using VinylEster only, to save costs dramatically.

    The idea is to lay the fibreglass out on a flat bench, apply the foam and just lay flat boards on top of the foam for weight till they cure.

    Then I will mount the panels in a basket, and layup the interior by hand.

    Doing the full mould for the bottom will be the most time consuming, but since I plan on building more of these boats, it should save time in the long run.
     

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  5. wardd
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    wardd Senior Member

    putting a vacuum on your layup table would be simple and bullet proof and you could use an old refrigerator compresser
     
  6. themanshed
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    themanshed Senior Member

    If the panels are to be bent into shape it is best to mold them to the shape not flat. Once a composite panel is made it is very stiff and will not want to bend. I’m not familiar with a basket. But if you can shape the foam in the basket then glass it you are better of.

    The usual way is to construct the foam shape then glass up the foam. I agree if you have a lay-up table it would be better to lay-up the complete panel in one step and a great chemical bond, very simple. Lay down some 3M- plastic, glass wetted out, bog on the foam, foam, bog the back side of the foam, then your laminate, peal ply, felt, then plastic bagging material fasten the bagging material to the table and pull a vacuum and it makes a great panel.

    Nice design.
     
  7. Alik
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    Alik Senior Member

    Back to delamination issues - before using any foam make sure it does not peel off. Some 'good quality' light density foams are easy to peel off in the center of core.

    I have never seen this happen with honeycombs, so I prefer to use honeycombs in deck and cabin.
     
  8. rwatson
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    rwatson Senior Member

    Well, I think non-vacuum methods are far easier and cheaper than layers of peel ply, vacuum bag, pipes, joiners, gauges, pumps etc.

    If I lay 1/2" waxed melamine faced, chipboard panels on the top of the foam which is on top of CSM which is on top of the 200 gsm which is on the flat layup bed, this thould give good compression I would think. I am planning on putting holes through the foam to ensure I dont get airlocks.

    As you say, its better to glass the foam in its bent shape. I am planning to only put one layer of 200 gsm + CSM under the foam for the initial flat join. I am expecting this to provide a good self-fairing panel that wont require a large number of moulds. Its a bit like making one big sheet of plywood, and laying it along the frames like you would with stitch and glue.

    This should not put significant internal pressure on the foam/glass interface, but keep it nice and rigid and fair for the internal hand layup. I think the layup schedule requires Bi-ax 400 gsm on the inside and outside.

    Its a bit of an untried method, and as you say Alik - I better check it out on some test pieces.
     
  9. apex1

    apex1 Guest

    It´s not that uncommon watson! Lookup bateaux.com they recommend it on some larger boats.

    Regards
    Richard
     
  10. f250
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    f250 Junior Member

    T+T+core= T+3% I dont think so
    = 2T + 3%
     
  11. Herman
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    Herman Senior Member

    I see there are dry spots, which means there have been air inclusions, very probably caused by "race tracking" in the corners.

    I also see the shape is somewhat more complicated, in which case it is more difficult to generate an infusion strategy by intuition and/or experience. A computer simulation (www.polyworx.com) would have helped.

    There are several stages at which things might have gone wrong: choosing layup, actual laying up, infusion strategy. It is impossible for us to find out what exactly went wrong, without knowing the complete story.

    Infusion is about getting the details right. Either you need to cut up the work in very manageble pieces, and have untrained people do it (I have seen it working) or have trained professionals who do the job, or at least supervise it. (which is an art in itself).

    Anyhow, as long as so called professionals still screw up, the infusion debate lingers on, and infusion will not be a widely accepted production method, even if it has certain advantages over traditional methods. (and yes, there are downsides as well)
     
  12. rwatson
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    rwatson Senior Member

    Thats good. I couldnt find anything after a quick look. I thought they only did plywood kits. Do you have a link ?
     
    Last edited: Oct 1, 2009
  13. themanshed
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    themanshed Senior Member

    T ; then compared to T in core of foam and the T laminate splt 1/2 of T on each side is 103% was the calc I used. Your formula is over kill, sorry if I was misunderstood.
     
  14. themanshed
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    themanshed Senior Member

    I am not an infusion fan at all. It's been done but my jury is still out. I compare it to Stevie Wonder in the subway trying to catch the 7:05.

    I'll keep my thought to boats for the US markets built in China private:p

    Hole in the foam is not keen in my book that is chance to de-laminate. The sheer force cannot be transfered between the skins. I drilled 1/8 inch holes 1 inch on center to raise the sheer in places. The holes were filled with bog. It is recommended to not have any voids in the foam. If you have a void it should be filled with a bog. They do make foam with small holes for the vacuum to suck resin though the foam to wetout both sides of a "panel" layup. The voids are filled with resin it does increases the weight.

    One layer of 200g E-glass unidirectional 90 degree may bend, perhaps you may want to try just one side first. Edge glue the sides of the foam with epoxy careful to not get any on the plane surface, if you do clean it up. The foam and glue sand at different rates, usually the foam will dish out..

    More next post.....
     

  15. themanshed
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    themanshed Senior Member

    If you want to make a panel and not want to use a vacuum do one side at a time foam down and perform your layup on the top with peel ply or 3M masking film and squeege it out very good. This will get the air out and make the cloth lay very flat / Let me see if I can find non-copyright material on the 3M masking film. I've used both; peel ply although more expensive works best. In your case once the top side is cured flip it over and do the process again. This way you will be sure that the air is out and the cloth will be very tight and have a nice finished surface. You will not need to weigh it down with peel ply and again have a very nice finished surface. Let it cure out completely before you try to remove the peel ply. Since I'm using West Systems I mixed some 407 powder to make a runny bog, ask your supply co. for the resin for something to add to the resin to make a thin bog for the first wetout. It is also recomended to flash coat the foam first with a thin coat of resin before you lay-up any glass. This will keep from dry spots during lay-up if the resin getting sucked up in the foam.

    (For your panel you may want to fore go the bog it tends to make the panel stiffer, save that for the inside. You may want to test with the lay-up on just one side only - Listen for cracks as you bend the foam panel, you may get away with it using E glass. It has been recommended for large panel lay-up to scrim one side of the foam to stiffen it, perhaps even thin mat for the scrim if 200g cloth proves too stiff.)

    I just used the peel ply method without a vacuum bag on a carbon mast repair last night and pulled off the peel ply tonight. It came out smooth, even though it was curved, and the cloth compacted very nice. The vacuum bag tends to wrinkle the cloth on a tight curve of a tear drop shaped mast of a A-Cat Catamaran.

    But my friend it is your job and I do not want to sound directive. I've studied this method for a decade and have become experienced with my project. I've been around boat building and studied with many boat builders of racing multihulls, and have about $1,000 US in design and consulting fees on my project from my NA.

    In the Aug edition of Sailing there is a story named Backyard Tri. I meet with Kevin Cook several times, prior to the article, in his house to learn from his experience. I've also meet with another NA on a different matter (purchase), specifically carbon fiber, foam, and vacuum bagging. I wanted to do my homework before I started my project. I also have the mold that Kevin used to build his boat and his plans for free. Kevin works with this stuff in his real job in the building of submarines for the US Navy. I meet Kevin though another forum, and ran into Kevin when I doing some work for the NCIS in Washington DC at the Navy Ship Yard.
     
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