Vacuum Bagging honeycomb core

Discussion in 'Fiberglass and Composite Boat Building' started by ian_upton, May 23, 2007.

  1. ian_upton
    Joined: Apr 2006
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    ian_upton Junior Member

    Does honeycomb core material lend itself to vacuum bagging?

    I am considering trying this when I replace a cabin bulkhead on an old Bertram 25.

    The finished surface will be painted, so I thought the peelply surface from the vacuum bag would give a nice surface to start with.

    I have access to partial sheets of Corecell at a considerable discount (Noah's in Toronto) and am also wondering if two pcs butted against each other would be sufficient or would this create a weak panel?


  2. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    Be aware that there is more than one type of honeycomb.I have encountered Nomex and Aluminium in vacuum bagging situations and both do a satisfactory job.You need to be sure that the material you have access to is of the correct density to provide the strength for the job and that it has the flexibility to conform to any necessary shape.
  3. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Corecell is not a honeycomb, it is a closed-cell foam. It is probably suitable for your bulkhead replacement.
    I have never seen a satisfactory honeycomb core job done without vacuum bagging, on anything but a horizontal flat plate. Curved or vertical parts with honeycombs simply have to be done under vacuum bag in order to work properly, unless you want the finished product to be 75% resin and way overweight. Nomex and aluminum honeycombs both have a tendency to suck the liquid resin out of the skins; a good layup is not nearly as easy as with solid fibreglass. Honeycombs are complex materials and specifying an appropriate one for a particular job requires a good understanding of the stress distributions within the part.
    A peel-ply surface has a slight texture, generally comparable to 150-220 grit sandpaper in terms of how much it deviates from perfectly smooth. It is paintable, but to get a mirror-smooth finish will require that you fair it with a microballoon filling compound.
  4. ian_upton
    Joined: Apr 2006
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    ian_upton Junior Member

    That's for the replies.

    I guess I was vague in my question. I understand that corecell and honeycomb are two different materials.

    My corecell question is will you lose much in stiffness by having multiple pcs of core material within the panel or should I spend the $$ for a continous sheet?

    If I am bagging a wet laminate (not infusion) do I need to prime the corecell with resin and let it kick?

    My concern with honeycomb was if the voids in the honeycomb would suck up the resin and create a honeycomb cells full of resin.


  5. Bayport_Bob
    Joined: Sep 2005
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    Bayport_Bob New Member

    Honeycomb cores are typically used with prepreg materials where the layup is cured in an autoclave or an oven under vacuum. There is minimal resin flow with this type of system and the hollow chambers don't fill up with resin.
  6. johnhazel
    Joined: Jun 2008
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    Location: Michigan

    johnhazel Senior Member

    Crozier Racing canoes has been vaccume bagging hand lay up carbonfiber/honeycomb for decades. These canoes are 18.5 ft long and weigh less than 30lbs. $4850 will get one for yourself but the waiting list is long. Crozier is getting tired of building.
    Rimer racing canoes also builds them in a slightly faster but less stable version. Those can be had for about $4400.

    The trick to bagging honeycomb core parts is to use a two step process which requires a two molds. For example if a 3/8" sandwich canoe hull is being built you need a mold for the inner layer and one for the outer. The inner mold (male) is the same shape as the outer mold (female) except that it is 3/8" smaller to make room for the core material.

    Building the part:
    The inner layer of cloth is laid on the male mold and wet out. Then the core material is laid onto the wet cloth and vaccume bagged down. After the epoxy cures the part is removed from the mold and trimmed/test fitted to the outer mold. Then cloth and epoxy are applied to the outer mold. The part from the previous operation is then bagged into the newly wetted cloth to crate the carbon-honeycomb-carbon sandwich.

    It is amazing how flexible the part is before it gets the second skin. This is a good thing though because that flexibility allows the second side of the honecomb to make good contact as it is bagged down into the wet cloth that becomes the outer hull.

    I actually have done this process in Rimer's shop and have spent several hours with Crozier in his shop too.
  7. tunnels

    tunnels Previous Member

    Simple question! what do you think will happen to the Honey comb when you put it under vacuum on a wet surface ?? remembering its got all those voids all over it ??:confused: :eek:
  8. lesburn1
    Joined: Oct 2007
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    lesburn1 Junior Member

    I have been vacuum bagging with honeycomb cores since 1986.
    My process has been to lay up the outer skin in the mold, then fit the prepared honeycomb core ( in my case a Plascore polycarbonate honeycomb product) then lay in the inter skin and install the Vacuum bagging consumables. This presupposes that all the components have been cut to plan before hand and that you are using a very slow resin/hardener mixture. While this works with S-Glass, I have found that kevlar rolls up on a pvc pipe after wet out much better.
  9. apex1

    apex1 Guest

    Not what your question suggests.................:confused: :eek:

    Nothing will happen, just the core will stay in place and have contact with the wetted out surface.
    Thats why it is done.

  10. tunnels

    tunnels Previous Member

    Trouble with answering peoples questions is do we understand what they are really asking ? what you see is totally differant to what i see ! so the answers given are a little bewildering for some one that dosent know much about what they have asked about .
    Lets try standing in there shoes with a blank mind looking at what they are asking about.
    I have often askes "HOW MUCH VAC SHOULD BE USED TO DO THE JOB" i have never had anyone answer ! dont they know or are they to affraid that what they say might not be right ?. :confused:
  11. apex1

    apex1 Guest

    so then Tunnels, here you can shine!

    What did you mean with: "remembering its got all those voids all over it "


    And don´t argue when your questions get no reply, YOU are the one claiming to know advanced composites! Although......
  12. tunnels

    tunnels Previous Member

    Honeycomb ,voids, empty spaces ,holes ,places that will fill with resin !!
    I have never laid claim to advanaces composites ever ! Have been round the playground a while and been and seen a lot a stuff in differant countries. When asked i will go any where to show others how and to learn from them ! There is no black and white in this industry just varying shades of the color gray !
  13. apex1

    apex1 Guest

    So, core composites are not known as "advanced composites" ???

    And the honeycomb spaces fill with resin when vac. bagged? How do they do that?
    In my village they don´t.

    Tunnels you should stay with what you know, not with what you guess!

  14. tunnels

    tunnels Previous Member

    Explan in fine detail how the voids never fill with resin if you place honey comb core under vacuum on a wet layer ?? :confused:

  15. apex1

    apex1 Guest

    Explain how they would, you are the "expert" :p (as far as the forum understands your claims)

    We are talking bagging here, not infusion!
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