Vacuum infusion autonomous vessel

Discussion in 'Fiberglass and Composite Boat Building' started by PjNote, Apr 12, 2016.

  1. PjNote
    Joined: Nov 2011
    Posts: 2
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    Location: Antwerp

    PjNote New Member

    Dear boat designers and builders!

    Three friends and I are building an autonomous vessel. At the moment we are building the prototype to do some testing with it before building the actual one. The prototype will be 2m long and 0.5 wide.

    We decided to use vacuum infusion to build a lightweight hull and deck structure. Since preparation and placement of spiral tubing, inlets and outlets is crucial, we would like to ask the experienced people from boat design.net for their opinion.

    I added a top view of the vacuum infusion set up in the attached picture.

    What do you guys and girls think about the placement of the spiral tubing, inlet and outlets?

    PJ

    Ps. you can find more information about us on projectmahi.com and pictures on twitter and facebook.
     

    Attached Files:

  2. rob denney
    Joined: Feb 2005
    Posts: 754
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    Location: Australia

    rob denney Senior Member

    Depending on the laminate, I doubt it will work as well as it could. A rule of thumb for first time infusers is that resin will travel a few centimetres across glass and 60 cms across flow medium.

    It will not flow very far/fast from resin to medium so the stern strip will not fully wet out before the resin enters the outlet on the stern.

    Assuming the flange has no laminate on it, i would run a piece of spiral or 3 strand rope around the flange near the edge. Put peel ply under it and extend it onto the glass. Apply the sealant tape next to the rope/spiral. You only need one outlet, the bow one would work best. Cover the laminate with medium, stopping 30mm from the edge, maybe a little more at the bows. Run the spiral from 300mm in from the edge of the mesh, along the keel to 300mm from the edge of the mesh at the bow.

    The resin inlet should be towards the stern, but is not critical. The resin should run very quickly along the spiral, a little slower through the mesh and quite slowly across the glass. If any of the edge gets fully wet, the resin will flow very slowly across the peel ply. By the time enough gets there to fill the spiral, the rest of it should be done.

    If the laminate includes foam, make sure it is perforated. If it is also slotted, you won't need the mesh. Any areas without foam, use the mesh.

    Hope this helps.
     
  3. PjNote
    Joined: Nov 2011
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    Location: Antwerp

    PjNote New Member

    Hi Rob,

    Thanks for your quick reply.

    I forgot to mention in the drawing attached to my previous message that the blue grid is also a flow mesh layer on top of the peel ply which is on top of the fibre layers. This means that the entire surface is covered with flow mesh to allow for quick distribution of the resin.

    As you assumed, there are indeed no fibre layers on the back flange. I was indeed thinking about taking the spiral tube a bit further than the end. The spiral tube will indeed then be on top of the peel ply. What do you mean by 'apply the sealant tape next to the rope/spiral'? What is the purpose of this?

    I tried to follow your reasoning and translated it into a sketch which I added to this message. Is this what you mean? The spiral tube is ran along the edge of the flange following the shape of the boat transversely and a resin connector is placed on the CL with a spiral tube then running longitudinally to the bow.

    I am however afraid with this set up that the side will not wet out and that the easiest for the resin is to flow along the spiral tube straight into the outlet...

    It is a monolithic laminate so no core.

    Let me know what you think. I'm eager to learn how the set up should be done correctly.

    PJ
     

    Attached Files:


  4. rob denney
    Joined: Feb 2005
    Posts: 754
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    Instead of sucking from end to end, it is better to suck from the middle to the edges. So the vac needs to be distributed all the way round the mould. Between the vac distribution line (rope or spiral) and the laminate there should be ~50mm of peel ply. Between the edge of the distribution mesh should stop ~20mm from the mould edge.

    The object is to quickly get the resin into 95% of the glass, then slow it's travel before it gets to the edge, then slow it again once it has wet the glass. Send me an email and I will send you a sketch.

    harryproa@gmail.com
     
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