wheat flour epoxy additive

Discussion in 'Boatbuilding' started by Collin, Nov 2, 2012.

  1. PAR
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    PAR Yacht Designer/Builder

    Vermin can't eat the flour used in a fillet. It's entombed, so getting at it will not be tasty and there's not much of it to make it worth their while. It will not break down with age, nor will it decompose. It's no different than wood or nut flour. If it's possible, get some wheat chaff flour, which will be stronger.
     
  2. Frosty

    Frosty Previous Member

    Flour, wheat , talcum is just a way of making space in the medium.

    Like mixing aggregate in cement does'nt matter what it is.

    In epoxy it is sealed , the rats cant eat it.

    In any discussion about humidity you have to include talc or micro balloons in the discussion.

    There is a difference in mixing in the rain and mixing on a rainy day.

    But --to repeat myself I buy talc at 10 baht per kilo 30 baht to a dollar.

    I cant by corn flour or anything in the supermarket that cheap.

    Sago _ I have used, rice, tapioca flour, corn starch many years ago before talc was available here.

    When I was asked why I was repaing my dinghy with rice and Fibreglass I said so if I get shipwrecked I can eat it.
     
  3. PAR
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    PAR Yacht Designer/Builder

    Flour, wheat or what ever are more than bulking agents and impart strength and stiffness to the cured matrix. Talc, balloons, etc. don't, unless used is huge quantities. Humidity can affect the bulking agents, as well as several other common filler materials, such as cotton flock and silica. If moisture content is permitted to stabilize at much higher levels, with open container on very humid days, then it will clump up and mix poorly, usually leaving unmixed clumps in the goo, which you find as dry powder as you smear it on something.

    For the most part you can use anything you like as a bulking agent, though light weight, easy to sand materials are obviously beneficial.
     
  4. Frosty

    Frosty Previous Member

    Mixing sawdust into water and freezing it goes against all reasonable thinking and makes a very very strong material called Pykrete.

    Simalarly mixing rubber particles with cement does the same there by suggesting the strength of the filler particles dont have anything to do with the strength of the epoxy substance when set.

    http://www.simegen.com/writers/lois/pykrete.htm
     
  5. PAR
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    PAR Yacht Designer/Builder

    Pykrete isn't unreasonable once you look at physical properties. Similarly concrete is a quite different material than epoxy and given it's physical properties . . .

    Various filler materials in epoxy are well documented, though possably hard to find without some industry insight. Improving epoxy and other resin systems with filler materials, does alter the physical attributes of the cured matrix. Aggregates are a different beast altogether and need to be looked at differently. Cast concrete is essentially useless without an aggregate or other reinforcement, ice not so much, though it can benefit from a fibrous filler, to help hold the crystalline structure together, preventing cracks and fractures.. Concrete can't be used comparatively against epoxy, it's just too weak and surprisingly flexible, amazingly enough. Ice is a little closer, but also not especially representative of these types of resin/filler combinations.
     
  6. Northman
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    Northman Junior Member

    For what it's worth I build a small (11 ft) sailing dinghy with plywood, epoxy and wheat flour only. It's now 9 years old and while I several times had to patch up some serious cracks in the plywood panels from when waves smashed it hard on the rocks I never had any trouble with the seams.
    Wheat flour I have always at hand and it doesn't cost me an arm and a leg as does any filler from an epoxy supplier. Next year I'll start with a nesting dinghy and it will be done with flour again.
    Walter
     
  7. waikikin
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    waikikin Senior Member

  8. Pericles
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    Pericles Senior Member

    I mixed dry Portland cement with epoxy resin and coated the bottom of a skiff with it. I rolled on the mix and flattened it with a polyester film, which I lifted off after the epoxy had cured, accompanied by ear splitting shrieks from the film. The result looked like obsidian glass. I decided that no further finishing was required, because UV radiation would not be a concern.

    The skiff bottom was hardly marked despite being grounded on river gravel on a number of occasions. The cement created a very tough surface and longboard sanding would be a thankless task, so using polyester film is an essential component of the process. For Brits, CFS Fibreglass in Redruth Cornwall supplied me with 10 metres of 87cm wide film for £26-78 delivered and it can be used a number of times. One caveat; flat surfaces only. :mad:
     
  9. Steve W
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    Steve W Senior Member

    When i first started down the boatbuilding path in New Zealand about 1970 the major epoxy supplier for several decades was Epiglass and they had a product called Epicrete which was basically epoxy and portland cement, they also had of course a full range of laminating resins, preblended epoxy thixotropic adhesive and fillers ready to use. Incidently,this was about the time that West was introducing the amature chemistry set to the boating world and one of the filler powders they offered was, wait for it, asbestos fibers. They were fairly long fibers and actually made a very strong filet, fortunatly i only used it on one project before it was pulled from the market.
    I sure miss Epiglue and Epifill, they did a much better job blending in the factory than we can in the shop.

    Steve.
     
  10. Steve W
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    Steve W Senior Member

    Waikikin, i use a cheap electric blender to blend my powders, i find that sometimes when i buy a 10lb bag of Aerosil it is lumpy, sometimes not, so when i am making my favorite fairing blend of 50:50 Aerosil/Q cell i throw equal scoops of each into the blender, put the lid on and give it a few seconds, smoooth.

    Steve.
     
  11. waikikin
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    waikikin Senior Member

    Sill use Epiglue here, sure beats mixing powders, nobody misses asbestos flock! Jeff.
     
  12. Frosty

    Frosty Previous Member

    I can see this conversation swaying towards the possibility that we as consumers are lead to believe that only one kind of product is suitable and ALL other alternatives are inferior.

    This is cheating and nothing more than repackaging a cheap item and selling it a profit because of our own unawarness and ignorance.

    This is an appaling suggestion.
     
  13. PAR
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    PAR Yacht Designer/Builder

    I disagree Frosty, most every boat builder I've met, has been "innovative" in many regard,s during every build. If you as a consumer don't do the back ground and end up paying full retail, for a product you could have had at 1/5th it's price, who's fault is it really.

    I'll gear up for some more tests over the holidays (not an uncommon thing for me) and I'll toss in some filler comparisons, to see how different species of wood flour compare to wheat, rice and corn flour from the supermarket.
     
  14. Collin
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    Collin Senior Member

    I'm going to test wheat flour too. I plan on testing the strength of fillets made with it and whether it absorbs water/the strength of the fillet after submersion.
     

  15. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You can skip the moisture gain test. flour becomes saturated with epoxy, so assuming you have a 100% solids resin, you're only going to find out what the moisture absorption rate is for the epoxy (3% or less), not what the flour may absorb. The only way the flour can cause a difference if if it's not mixed very well in the resin, which is just testing bad prep procedures and dubious at best.

    Also there's more to the equation with testing, strength is just one component. Peel strength, stiffness, elongation, tension and compression are some of the others. Naturally, these all need to be compared to something, so a base line for each test is necessary.
     
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