DIY Carbon whisker pole

Discussion in 'Boat Design' started by Gashmore, Dec 25, 2009.

  1. mark775

    mark775 Guest

    With an imidazole (like EMI-24) or lewis acid (like boron trichloride amine) you can get anything from 24 hours to six months room temperature gel time. Typical room temperature gel time with EMI-24 is 2-5 days (depending on ambient temps) but with even modest heating to 120F it will cure in 6 hours. It has an unlimited post-cure window, also. (This is NOT necessarily true for the amine agents you typically see in commercial prepreg; if you get the cure cycle wrong, it may be impossible to EVER achieve the full 'as advertised' cured state properties, no matter what you do later with post curing.)

    These type of agents do not have a critical mix ratio either and will work in any resin. The typical 'starting point' mix ratio is 4%. Either will work as low as 1% PHR.
    - Jimbo, What is "any resin"? I thot we were talking epoxy. You have completely lost me. Where do I find the info in print? In other words, how do I learn this?
     
  2. Jimbo1490
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    Jimbo1490 Senior Member

    Yes, it's understood we're talking epoxies, here. The others are not even compatible with the finish on carbon fiber anyway. I mean they will work in West, East, Epon, hardware store, 'clock table' or whatever epoxy resin you can find, they will cure it.

    These are true 'catalysts' for epoxy. All the others are 'curing agents', NOT catalysts. Catalysts typically do not have a set 'stoichiometric' mix ratio, but instead can be varied, resulting in different cure cycle time and cured state properties. With a 'curing agent', varying the mix ratio more than a few % will give your the cured state property called 'mush':D

    Jimbo
     
  3. mark775

    mark775 Guest

    I usually use Systems Three. Their how-to pamphlet doesn't talk about this...
     
    Last edited by a moderator: Dec 30, 2009
  4. Gashmore
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    Gashmore Junior Member

    West and System Three are general purpose room temperature cure epoxies. Their instructions don't cover the more advanced techniques. West makes a high performance line called Pro-Set that has a lot more variety of cure processes. Once you get into the more exotic formulations though you have to do a lot more study to figure out exactly how to use them properly.
     
  5. SamSam
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    SamSam Senior Member

    G Ashmore, are you still contemplating a move to the coast here to finish up the boat?
     
  6. Steve W
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    Steve W Senior Member

    Gash,this is an interesting project that i expect to learn a lot from following.I can totally understand your fear of not being able to get it off the mandrel,would it be possible to layup over a styrofoam mandrel,build a conventional oven to cure and then melt the foam out with acetone?
    Also,do you have any estimates as to the weight of the finished tube,i think you were stating it would be 3"ID x12ft,is this correct?
    Steve.
     
  7. Gashmore
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    Gashmore Junior Member

    Sam, I was going to commission her at Tidewater in Savannah but they sold out to Hinkely and are a bit to high cotton for me. Not very DIY friendly. Looks like Two Way Fish Camp in Darien will be the alternate.

    I would worry that styrofoam would be to soft and crush some under the bag causing buckling in the transverse fiber. Worst case I could pour some antifreeze and dry ice down the pipe to shrink it away from the carbon.

    Assuming my layup is adequate I figure the finished tubes would weigh about 8 to 9 pounds each. Target weight for both tubes with end fittings and stinger rod maybe 24 to 25 pounds. I actually worked backwards from the weight of a Forespar carbon LC13-24 to estimate the layup. In aluminum tube it would be close to 40 pounds and wouldn't be as much fun to build. :D
     
  8. Gashmore
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    Gashmore Junior Member

    Thought I should update the plan so if the whisker pole turns out a disaster you will know what not to do. My apologies to the SI fans but I grew up in the imperial/slide rule era.

    First step was to figure out the curing oven. The recommended cure cycle is ramp up at <5F/minute, hold at 200F for 30 minutes for the resin to consolidate, ramp up at <5F/minute to 250F and hold for 240 minutes. Then cool at <5F/minute to below 150F.

    R6 rated fiberglass duct board will be the material. A piece of aluminum down spout laying on the bottom of the oven with slots cut in it will be the baffle. The oven interior will be 168"Lx8"Wx14"H with a total area of about 53 sq.ft. Cure temperature will be 250F so maximum delta T will be about 190F and heat loss will be about 1,700 BTU/Hour. (53 sq ft/R6*190F)

    The aluminum pipe mandrel weighs 28 pounds and has a specific heat of .230 BTU/lb. so it will require 6.5 BTU to raise the temperature 1F.

    Epoxy resin and carbon will weigh about 8 lb and the specific heat of both is about .260 BTU/lb or about 2 BTU for 1F rise.

    Ramp speed is 5F/minute so the heat source will have to provide 8.5x5 = 42.5 BTU/minute or about 2,550 BTU/Hour.

    The maximum heat supplied will be in the last minute before the pole reaches the final cure temperature of 250F so adding the heat loss to the ramp heat comes to about 4250 BTU/hour.

    So theoretically the heat source will have to start at about 2500 BTU/hour and gradually increase to 4250 BTU/Hour then drop to around 1700 BTU/Hour. But, the air that is blown in has to come out so not all the heat will make it into the layup. I am guessing that the heat source needs to supply at least 50% more BTUs. If it takes more than that the ramp up will just be slower. No harm in that.

    To prevent thermal shock the cool down has to be less than 5F/minute. At the cure temperature the mandrel and tube will need to loose about 1600 BTU to get back to ambient. (8.5*190F) If the oven looses 1700 BTU/hour at 250F that works out to about 28 BTU/minute or about a 2F drop per minute and gets slower as the oven cools all I have to do is turn off the heat and wait.

    In my collection of esoteric and seldom used tools I happen to have a 2KW heat blower that can put out about 6800 BTU/hour at 800F. Sort of a heat gun on steroids. I'm thinking I could rewire the blower's heating element through a relay that the PID controller could turn on and off as needed.

    The next question is where to vent the oven to insure even heating. I am thinking slots at the bottom of each end just past solid mandrel supports. That way the air has to come up and over the mandrel before turning down and out the vents.
     

  9. wet feet
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    wet feet Senior Member

    It all seems to be progressing well.I hope the collection of esoteric tools includes a thermocouple or two as I know a man who made a mistake early in his composite career by not using one.He made sure that the temperature readout on the oven controller followed the recommendations,quite oblivious to the fact that the resin/fibre matrix was not doing the same as the oven roof.The component was scrap and its replacement had a thermocouple inside the vacuum bag which gave the readings that mattered.I would think that for your project it would be no bad thing to try to blow at least some of the heated air down the middle of the pipe as the conductivity is likely to be better than through the breather cloth.It would also help with attaining the expansion that may be useful when releasing the part.
    I have to admit to a lack of comprehension about the units;most of the prepreg I have encountered cures at 120C and the dwell time at maximum temperature is less than 4 hours.No doubt this is a matter of different resins from different suppliers.Please continue to keep us informed about the project.
     
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