Foam cored flats boat?

Discussion in 'Boatbuilding' started by gotmuddy, Jan 7, 2013.

  1. Tungsten
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    Tungsten Senior Member

    Not to highjack but what happens to the cured glass on flat foam panals when bent into shapes.Does this weakin the joint from glass to foam?
     
  2. groper
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    groper Senior Member

    The only axe i have to grind, is the misinformation you presented, nothing more. If you post misinformation on a public forum, then expect it to be corrected.

    Sandwich panels are typically much stiffer than ply for a boat of the same design, in most instances a design can be built in a similar fashion to a plywood boat (sheeting the hull skins over the bulkheads) without even the need for stringers due to the increased stiffness. However, if less stiffness is required for bending a tighter curvature for example, then the sandwich panel can be re-engineered with different laminates or core thickness to accommodate. its a very versatile method...

    Tungsten,

    The allowable bend radius can be tweaked in many ways as i hinted to above. If you simply try to bend a panel beyond what its capable of, then yes it will either break or start to de-laminate. Tight radii are generally made via kerf cutting the panel leaving 1 skin intact, bending the panel and then restoring the cut side laminate. Another option is to leave the core out altogether so you only bending a single skin solid glass laminate. The amount of bend you can get into a solid glass laminate depends on its thickness AND the fibre orientation within it. ie - its most difficult to bend with the fold axis at 90deg (perpendicular) to the fibre. A typical folded panel will have the fibres at 45deg to the fold axis. Gradual gentle bends are not a problem, you dont have to do anything more- you can basically treat it like a sheet of plywood. If the bend is a bit more significant, I like to do this when the epoxy is still quite green (less than 24hours cured), then once in shape, heating the panel (using sunlight) you can raise the temp past the very low HDT of the green resin, which softens it and relieves some of the skin stress you have put into the panel from the bend...
     
  3. Oyster
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    Oyster Senior Member

    Sure, as you back track on the folly of your laminating foam and admit that torturing into some shape can and will stresse the layup. You are correct that there is a lot of misinformation that fills forums, using big brushes to do so. Reengineering a project? First you need to look at the best way and if a person is not familiar with boat related properties to make a sound hull, its quite possible that they also will end up with a questionable hull too.

    I did not address your folly early on as it was laughable at best, even though you continue to spread myths that a one off builder with a 16 or 18 should only subscribe to your folly in this build. What you have additionally described amounts to many grey areas in the wrong hands too. If you are going to have to cut glass in order to get the shape that you need, you have also done double the work and will also end up with questionable areas in the relieved area in which you will need to also do big amounts of fairing. In those slits in and around those areas, you do not get a continuous curve or flow of the hardened panel regions of the glassed sections. Its no different than a cardboard box corner that has not grid in that area.

    Foam is very forgiving but attempting to sand hardened glue filled seams against foam comes with pitfalls too.

    Carry on,,,
     
  4. groper
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    groper Senior Member

    So does plywood! Anytime you bend a sheet of anything you introduce stress. How much is acceptable is totally dependant on the individual situation, but its generally and widely accepted that small amounts of stress from panel bending are not a problem, every bent sheet boat on the water is tesatment to this.

    At what point did i say people should only subscribe to my methods and exactly what myths have i spread? The only inaccurate information posted in this thread has come from you. I have provided explanations and examples including photographs of the methods - you pass off as folly... wheres your proof to back up your claims?

    It seems like a grey area because you do not understand it. Did you ever consider not putting any glass in the area you plan to cut or not putting any core so that you do not have to cut??? Did you not see or understand the photos i posted earlier???

    You have no idea what you are talking about. Have you ever worked with composite panels or are you simply passing on "hear say" youve picked up around the grape vine? How closely you space the kerf cuts determines how pronounced/visible the chines showing in the panel will be...

    Heres a pic of the same hull bilge posted earlier, faired and painted. The bent area needed no fairing compound whatsoever beyond what could be acheived within the thickness of 2 coats of high build paint primer.
    [​IMG]

    If you are doing this, again you have no idea what you are doing... i have never needed to do what you described above, it is a mistake to even attempt it...

    Its clear to me that the problem is not the composite panels, it is that you do not understand how to work with them. Ill refer to an earlier comment, if you did some more reading and learning you might be able to get the results using very similar methods to plywood boat building. If kerf cutting the panels is not your cup of tea, then dont do it... instead do it the way you would with plywood... cutting and bending is an additional versatility you dont have with plywood, which is the only reason i brought it up...
     
  5. groper
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    groper Senior Member

    Here, you might learn something from this too; and before you get knit picky, if infusion is not your thing, you could hand laminate the panels instead... its the concept, rather than the execution, that is relevant.

     
  6. Oyster
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    Oyster Senior Member

    More ifs, ands and buts,,, Look if you wish to do someone one way, that does not mean that its your way or the highway across the board in the art or sport of building boats.

    Misinformation you say in all of my posts? Well geewizz, you need to let a much larger fish know when it comes to building hulls with foam as its primary shape component. For some reason you are at odds with some folks familiar with plywood and foam core construction methods, spreading their wares across the internet.

    A person is limited with the use of glassed sheet foam of any size when torturing is required, even though you have represented examples in which has worked for you.
    http://www.amateurboatbuilding.com/articles/howto/foam_sandwich/index.html

    These folks have provided the identical information in which many seasoned folks will subscribe to, too.

    But in the hands of people just starting out, bending glassed foam panels comes with many downsides unlike bending plywood panels, simply because the components in glassed foam panels have entirely different properties unlike the wooden veneers glued together. The veneer are much more consistant in density and the bonds of plywood is normally thinner than your proper glass thats required for the laminates making up the skins of the foam. This allows a more forgiving bend without scoring or even stressing the inner laminates or cores or bonds, which also gives a person a much better and continuous run of their component, which also reduces the amount of work for a finished product with shine on it.

    If the bend is too tight, then alternative methods and materials creates a much better arrangement in the hands of an amateur in hopes to achieve a finished product that you can be happy with.

    I have worked with Airex, Divinicell, and Klegecell along with Coosa Board since the modern era of boating when wooden boats fell from grace on the production markets. There is some content on this forum early on that provides some insight too. I have fixed enough balsa cored crap that was also the wearall of all alternative materials for weight savings and contored shapes for cores.

    While building with foam has its advantages, in the wrong hands and wrong applications, mainly in small runabouts or even dinghies, any and all amateurs will not create a better hull the first time around with any foam.
     
  7. groper
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    groper Senior Member

    In an effort to bury the hatchet with you, i will make some more "ifs and buts"...

    I will agree with you in that, IF you plan to work with unglassed foam sheet over forma/frames, you will need to support the sheets at closer spacings. BUT, this method described in your link above, is not the only way of building a boat with foam and is certainly not the ideal way you would build a flats boat using foam, NOR any other boat design that uses developable plates/panels. Building in the manner you have linked to, is a method for creating compound curvature in foam, thats the only reason to use that method. You would need a similar method to the same in ply, like double diagonal for example.

    Your comments on people just starting out are valid, BUT IF you remember, the person that started this thread said he has a friend that builds composite aircraft helping him - so therefore has access to considerable expertise working with foam core composites.

    All i offered, was advice on building developable (single curvature) designs using foam core panels. Whilst its certainly not the be all and end all, and has its limitations. The most annoying and limiting is almost zero compound curvature. Its a very efficient building method in terms of labour, that acheives very fair lines. If you infuse or vacuum bag the panels on a table, no fairing at all is required over most of the surface area as you get dead flat "shiney side" off the table. Only the tape joins between panels/chines need fairing, this can be almost eliminated by using rabets on the panel edges to lay the tape into. Most people know this method as dereck kelsalls KSS building method although i see his core concept in the dart cuts and pulling the infused hull profiles into shape on a jig - not so much building with flat composite panels...
     
  8. Oyster
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    Oyster Senior Member

  9. groper
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    groper Senior Member

    very interested, thankyou.
     
  10. edwmama
    Joined: Feb 2013
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    edwmama New Member

    concerns about 30 year old balsa cored FG C&C hull

    hollo

    i own a Cal /cruising 46, the original Cal 46 designed by the hall of fame designer Bill lapworth. its a solid thick epoxy fiberglass hull

    it sails well and is rock solid.

    lately i have been looking at the C & C landfall 48 with indoor steering. it offers more room etc.

    my overwhelming concern with these 30+ year old
    boats is their balsa cored hulls which can rot and destabilize the whole structure which could lead to a catastrophic hull failure...as i understand to repair the balsa coring would coast more than the whole boat

    what has been your experience with this boat specifically in regard to the hull integrity and overall performance and quality

    bests
    edwin

    Cal Cruising 46
    Lahlia
    Marina del Rey, CA
     
  11. edwmama
    Joined: Feb 2013
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    Location: marina del rey ca

    edwmama New Member

    hello kingfisher

    i own a Cal /cruising 46, the original Cal 46 designed by the hall of fame designer Bill lapworth. its a solid thick epoxy fiberglass hull

    it sails well and is rock solid.

    lately i have been looking at the C & C landfall 48 with indoor steering. it offers more room etc.

    my overwhelming concern with these 30+ year old
    boats is their balsa cored hulls which can rot and destabilize the whole structure which could lead to a catastrophic hull failure...as i understand to repair the balsa coring would coast more than the whole boat

    what has been your experience with this boat specifically in regard to the hull integrity and overall performance and quality

    bests
    edwin

    Cal Cruising 46
    Lahlia
    Marina del Rey, CA
     
  12. Johnbrad

    Johnbrad Previous Member

    I think you have finally completed your project and the boat looks awesome!
     

  13. SamSam
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    SamSam Senior Member

    I would experiment first with that scenario. I once made a banjo case using styrofoam covered in a few layers of duct tape and a layup of mat and polyester resin. It immediately started changing shape, when it was all cured and set I cut it open on the line to form the case and the lid. All the duct tape was still stuck together and in its general form but the styrofoam was all shriveled up into a solid lump about the size of a golf ball. It wasn't contact with the resin/styrene that had destroyed it but just being enclosed with the fumes of the styrene. So I would be leery about switching to regular polyester resin in your laminate.
     
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