Carbon items

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Feb 3, 2018.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Want to build some carbon items...

    I see you can purchase carbon tubing for about 10 bucks a foot for 1/2" tube. I want to do some things in carbon on my boat and there is a local supplier of carbon fabric, but I haven't got a clue about how to proceed.

    I would like to have carbon railings and posts. I need about 35 feet of railings and the posts are roughly 15" high give or take.

    I would like to build a carbon windscreen with lexan in it. I'm not sure how, but perhaps I could trap the lexan between two carbon pieces or build some type of flange to hold the lexan in place.

    I would like to build carbon posts for the helm enclosure which is outside. I was thinking some rectangular posts with 1/4" radius edges might look nice. The posts might be like a 1x2 or 3/4" by 1.5" actual. I could wrap core for those if it was easier. Those might be rather long, like, ? 8' pieces..tbd Also not sure how you'd intersect post and rail, but perhaps I could build some carbon connectors?

    It might be a fun way to start to learn infusion. I could maybe start by building the railing posts 18" long. They might be good at 3/4 or 1" rounds?

    Problem is, I have no idea how any of these smaller parts are made with carbon. Are they moulding rounds over a waxed pipe, or is there some magic machine to do it?

    Any takers on advice? Thanks.
     
  2. rxcomposite
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    rxcomposite Senior Member

    Carbon fiber has a zero or negative CTE. Bonding it to Eglass itself (which has a high CTE) is a problem as internal stress will develop. Lexan or Acrylic has a very high CTE. It expand when heated. The way to low CTE safety glass is to isolate it from the frame by an elastomeric compound or sealant tape. The side must not touch the frame by about 1/8" and adequate clearance must be provided all around the edges or filled with rubber or sealant. This is a class rule.

    If you are bolting Lexan or Acrylic, the hole must be bigger by more than 1/8" (depending on the area of the panel). This allows the plastic to move while expanding. We build racing cars before and we used acrylic for windshield. The hole keeps cracking so we oversized it and used large washers.
     
  3. fallguy
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    fallguy Senior Member

    I wrote a nice long reply, lost it somehow, will try again.

    Thanks for the information. This is all for the helm enclosure. I would like carbon railings, but plan to purchase them.

    So, I will avoid marrying glass and carbon and leave gaps in any lexan/ carbon framing intersections.

    My helm enclosure is on a riser and the helm overlooks the cabin roof. The cabin roof is about 5' high above the cockpit sole. The boat is fully demountable, thus the desire to make an ultralight windscreen/helm enclosure. The width of the helm is about 4' and the depth for and aft is say 4' as well. The height of the helm above the cockpit sole would be about 7'; perhaps a bit less. I would like to build the enclosure frame with carbon. The top of the helm enclosure could be vinyl or carbon only, but not sure how I'd attach a carbon rooftop to posts underneath and make it removeable.

    Also, can I put carbon around high density m200 corecell? I imagine the corecell would heat and the carbon would not expand and thus I'd end up cracking the carbon. I was hoping for bolt and screws into the posts for snap bases. I suppose I could make the inside of the posts hollow to allow for expansion inward?

    Then, the only real difficult thing is how to combine the carbon support posts and the carbon roof frame. Anywhere framing intersects, what would be done? Could I build a carbon line rail clamp of sorts?

    Thanks for any thoughts.

    My boat build picture isn't updated for a few weeks, but here is a picture. The first hull has a beaching keel on it now and all the taping is done; ready for sanding and fairing. The first hull is getting wrapped for outdoors (no paint on it so needs covers) and we will start hull two in about 10 days. Hard to believe from the picture, but this is a 32' cat hull. The frame is half apart due to head clearance problems with the flip.


    IMG_3150.JPG
     
  4. rxcomposite
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    rxcomposite Senior Member

    It is only an helm enclosure so there is no benefit in using carbon. Weight savings would be minimal.

    If you plan on carbon railings, that is fine. It will be supported on several distant points. Lots of leeway for expansion.

    You can skin M200 corecell with carbon. That is standard practice. It is the shear in the core or the bondline that matters. Since you are using a high elongation resin, it should work.
     
  5. fallguy
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    fallguy Senior Member

    The helm is removable. I would like the components to be light.

    For example, one of the components is a riser step. A chair will sit on it as will two people. It will be screwed to a cleat on the cockpit sole, which is also removable.

    The riser is about 10” high by 4’ long by 3’ wide. The windscreen will be ? 12” high or so by 3’ wide lexan. The rooftop would be 3x4 with one edge the windscreen. Seems like carbon would be handy.

    I just don’t know how to join perpendiculars. Bolts I suppose with some type of female half pipe shape like a line rail clamp.
     
  6. rxcomposite
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    rxcomposite Senior Member

    Fallguy- Do you have a sketch so others can chime in?
     
  7. fallguy
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    fallguy Senior Member

    See study plan link below.

    Basically, the cockpit sole panels are attached to the hulls and beams. They are about 4’ wide by 8’ long each and join the hulls and each other on the 8’ side.

    The sole is about 8” above the cabin sole which is forward of the cockpit.

    The roof of the cabin is about 5’ 6” above the cockpit sole thus.

    Then the helm riser is starboard. The riser is about 8”; perhaps with a second step if need be. About 4x4 riser. On top of the riser a chair. The helm will be attached to the aft side of the cabin and the windscreen attached to the cabin roof.

    The helm is permanent. The riser, chair and enclosure, windscreen- all removable.

    This is not really a trade secret as Richard’s Skoota 28 has helm videos. His helm is not enclosed. I will be traveling in colder conditions.

    I attached the study plan which is public domain. He calls the riser a steering upstand and shows min 1100x600 mm. I said 4x4 or 3x4, but I expect mine to be a bit wider than he shows. You'll see the windscreen in sideview of the boat. The windscreen doesn't have any aft attachment points. Please refrain from mentioning Richard or the designer in any responses; he and I have not had time to discuss this in detail. I thought it might be fun to do some things in carbon and it is an aesthetic, not construction requirement. Thank you.

    Also want the windscreen removable for driving the cabin down the freeway on a trailer at 70mph.
     

    Attached Files:

    Last edited: Feb 8, 2018
  8. fallguy
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    fallguy Senior Member

    So, the carbon wrap around the M200...

    Where do you terminate the edges of the carbon and how would you laminate a 1" x 2" rounded edge profile to make it come out looking great and avoid air bubbles/voids. And then how much carbon would I need around the aft supports which might be 6 1/2' long?

    Obviously, I am using vacuum. I could perhaps build a female half mould and wet the carbon inside the mould, the M200 into it and then an overwrap and vacuum press the entire thing, but not sure how I'd keep the edges together while getting it in the bag...perhaps it'd be easier to shrink wrap the carbon onto the core and skip the vac. Does shrink wrap stick to epoxy? Never tried it. Sounds messy...

    Any advice on making a clean part would be helpful. Tape doesn't really work because it'll be wet.. Infusion might be the best way to go because everything could be taped up nice and tight before wetout. I'd have to learn it.
     

  9. Tungsten
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    Tungsten Senior Member

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