Any experience with Coremat Xi ?

Discussion in 'Fiberglass and Composite Boat Building' started by jav, Jun 12, 2008.

  1. jav
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    jav Junior Member

    I'm interested in using this material as a core (4mm) in a hardtop I'm building but have found almost no information on it. I'm most interested in how easy it is to work with, how it bonds to other laminate layers (cloth,roving,matt),how much resin it aborbs and how solid it is once saturated. Is it not a good idea to have end grain exposed (like at an edge)? Will it absorb water etc?

    Any help appreciated.
     
  2. Herman
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    Herman Senior Member

    http://www.lantor.nl/index.php/id_structuur/10598/coremat.html

    Above is a link to some reading. Also the links on the bottom are nice.

    Although advertised as a lightweight material, from a boating point of view it is not really light. (due to resin consumption). Xm version is slightly lighter. Read that in the link.

    Properties are quite resin-dependant. When the product is compared with a single skin laminate of the same weight, there will be less glass, but the product is more stiff, due to the increased thickness.

    I must say I rarely see problems with this material. Probably due to a combination of factors:
    -no large loads on the end products
    -usually quite good workmanship
    -although thicker than single skin, end product will still be relatively thin, so deflection will help spread loads.

    Answers on your questions:
    relatively easy to work with, cut in shape, impregnate one side, turn over on the part, then impregnate the other side. Use enough resin. Excess resin can be used for the next layer of glass
    the bond to other materials is dependent on the resin used, but is more than adequate.
    resin: 600 gram / m2 / mm. (your turn to convert that to imperial...)
    if possible, do not keep the edges exposed. They will be somewhat fraying, and might absorb water. It is better to beef up the structure with some CSM450 (4 layers, in the case of 4mm Coremat) on the sides. (narrow strips 1" are enough)
     
  3. jav
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    jav Junior Member

    Herman-

    thank you! Yes I had read all the site info and my laminate analysis software lists Coremat Xm... but not the Xi. And yes- I had already converted to imperial...it's a shame my mind just doesn't wrap itself as easily around the metric system but "old dogs" as they say.

    I've been running some calculations to gauge different layups and adding the 4MM (Xm) coremat really improves the tops stiffness, even though I understand the strength to weight ratio isn't very good (and the Xi is 20% worse than the Xm). I can only seem to find the Xi locally so I was concerned about the differences.

    I Understand on the end grain- that was one concern and the other was it failing as a core either by falling apart itself or via poor adhesion wth other laminate layers. Sounds like it should work and appears to be somewhat economical per M2 @ 4mm.
     
  4. Herman
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    Herman Senior Member

    I used it in trailer moulds (where racing boats sit on) in 4mm, and I always was happy with the results. I did not care to seal the end grain, as the product was neither highly loaded nor visuallt important. I was just aiming for more stiffness. (some areas were treated with a double layer)

    I also used it in some racing boat decks, but the end grain was hard to seal. The Xm version was used in the sides (tanks) and that worked well. No end grain there. I used vacuum there, and today Lantor has their "Soric" for that, which does not compress. I used that for several other items, including boat hulls.
     
  5. waikikin
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    waikikin Senior Member

    Jav, the main problem I,ve seen with coremat style products is usually due to insuficient resin, as Herman has indicated you must wet out the back of it before laying into the job, if you dont it will scavenge resin from the base laminate & can end up "dry" & not too good a job. All the best from Jeff.
     
  6. jav
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    jav Junior Member

    Well - if I could indulge a little more help... my layup plan was spread into 3 stages of laying this up on a male mold.

    1st day- gelcoat then 1 layer 1.5 oz c/s mat. (wet on dry)
    second day- 18 oz roving then 4mm coremat (wet on wet)
    3rd day 18 oz roving, and 1.5 oz. CS mat. (wet on wet)

    But the wetting out of the core "down" face has me worried. Once the coremat is wetted out, the binder would allow "stretch " (this is according to their website). So placing the nicely cut shapes, of which some are large (and heavy with resin if pre-wetted on one side), is going to be quite difficult to do well.

    My plan had been (on day 2) to layup the first layer of roving with a very heavy layer or resin then place the coremat dry on that wet layer and then continue to wet out the coremat from the top (using the color change feature to gauge saturation). Is this not advisable? If not, how do you handle large sections of wet coremat when the shapes and placemnt are somewhat critical?

    Any suggestions about the mat or the layup schedule are appreciated.
     
  7. Herman
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    Herman Senior Member

    Your second day creates some heavy resin buildup, thus heat. Probably not so important, as you are working over a male mould.

    Handling heavy Coremat? Be with 2 persons, and do not make the patches too large.

    I suggest letting the 1st layer of day 2 cure, then lay a patch of Core-mat up-side down on the laminate, roll in the backside, turn over and adjust placement, then impregnate topside. And on to the next patch... Calculate the amount of resin that you SHOULD use. This is a nice guide, although my experience is that you will probably need slightly more. You can let this cure, or put the next layer of glass over it. Depends on the project.
     

  8. jav
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    jav Junior Member

    Herman-

    unfortunatly, 2 persons is not an option where I'm doing this project. I suppose I could make the patches smaller but had tried to minimize breaks in the core to maintain as much strength as possible.

    As far as letting 1st layer of day 2 cure, I thought of that as well but I've not had the best luck with roving as a single later (without a wet mat backer)... I figured wet on wet with the core would provide the best roving to core primary bond and minimize weight /resin useage.

    But I am concerned about the heat as well given the size of the panel about (2 meters x 2.5 meters). I've always heard 1 layer per day on large layups but I don't know what constitutes "large". I've laid multiple layers in one day on smaller molds so this is new to me.
     
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