Need advice on infusion/vacuum line arrangement

Discussion in 'Fiberglass and Composite Boat Building' started by laukejas, Dec 26, 2024.

  1. laukejas
    Joined: Feb 2012
    Posts: 823
    Likes: 25, Points: 28, Legacy Rep: 128
    Location: Lithuania

    laukejas Senior Member

    Hi guys, Merry Christmas! I've begun building a new boat, where the construction is 3D printed core encased in carbon fiber. Imagine like how surfboards are made (foam core and fiberglass all around), but with 3D printed plastic instead of foam. The goal is to avoid having to build molds, yet still end up with lightweight and strong composite hull, saving lots of expense for a one-off design.

    I have worked with composites before, but it's my first time with infusion, and since I'm doing it without molds, it is somewhat risky and unproven technique. To test it out, I first want to try it on smaller parts, to see if it works at all. Here I have printed the core for the rudder blade that I want to try infusion on.

    upload_2024-12-26_12-30-50.png

    I am aware that this blade would be far easier to make with layup instead of infusion, but like I said, I want to try infusion because I need to test this method before doing the entire boat hull this way; layup won't be possible there because I won't be able to wet all the layers and bag it before epoxy starts to set, it would be a race against time. Besides, infusion results in much lower weight, which is critical in my design.

    How I imagine this happening:
    1. Seal the surface with epoxy and very light fiberglass cloth so that it doesn't collapse or soak in epoxy during vacuuming;
    2. Key the surface with sandpaper;
    3. Attach 3 layers of 220gsm carbon fiber, using composites tack spray to keep it in place, with overlaps where necessary;
    4. Add peel ply, infusion mesh and infusion/vacuuming lines;
    5. Bag and vacuum it, test for leaks;
    6. Infuse;
    7. Remove consumables;
    8. The surface will be rough and probably uneven at overlaps, so fair it with epoxy filler;
    9. Prime and paint.

    However, I am not sure on how should I arrange infusion and vacuum lines. Should I run an infusion line along one side of the blade, and have a vacuum outlet on the other side? I mean like this?

    upload_2024-12-26_12-54-21.png


    Or add multiple horizontal infusion lines in a "ring" around the blade? Or something else? Those who are experienced with infusion, can you advise? I've watched some EasyComposites videos on YT, but they all deal with arrangements in molds, not "around" the parts like in my case.
     
    Last edited: Dec 26, 2024
  2. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    I'm still a neophyte at infusion but have made a two of three side planks for my proa, learning as I go.

    Planks are ~ 6' long with a 7" wide by 2 1/4" cross section. Core is a blend of 1.75" xp foam with a 1/2" gpet cap on top. Reinforcement is 22 oz uni top and bottom wrapped with 18 oz woven glass. Uni is stapled to foam with ss staples and glass wrap, peel ply and infusion media held in place with rubber bands, ends spray glued down.

    Infusion setup is with supply along one side of plank and vacuum on the other bagged in a poly tube.

    First plank used some harbor freight open weave tarp stuff for infusion media, idea gleaned from a YT video on home built aircraft. Worked OK on a test piece, cheap and easy. Bigger plank worked but was a PITA to remove, stiff and wastes way too much epoxy. Other issue was I had one feed point for supply epoxy at center of plank and one end filled before the other and ended up with a dry spot at one end, easily enough wet out later.

    Second plank used real infusion media, much better. Feed line fed in at two places to balance supply and was better but one end still won the race and there was a dry spot at one end.

    Last plank will have two separate feed lines so as to shut one side down when filled and waste less epoxy. I'll post some pictures when all my company has left here after the holidays and I have access to computer in study.
     
  3. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    First.jpg
    First plank setup from feed line side
     

    Attached Files:

    Last edited: Dec 26, 2024
  4. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    Removal.jpg
    Laboriously removing infusion media and peel ply.
     
  5. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    20240826_094654.jpg
    Dry patch.
     
  6. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    20240908_103930.jpg
    Second plank partially infused, view from vacuum side.
     
  7. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    Final.jpg
    Second plank, with smaller dry spot.
     
  8. laukejas
    Joined: Feb 2012
    Posts: 823
    Likes: 25, Points: 28, Legacy Rep: 128
    Location: Lithuania

    laukejas Senior Member

    Thank you, this is very useful! From this I gather that is best to have multiple infusion/vacuum lines, so they can be clamped off fully or partially to control the flow and balance the infusion. How did you wet out these dry spots afterwards? Wasn't it difficult getting epoxy through that many layers of fiberglass?
     
  9. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    The dry spots were wet out with small brush then peel plied. Dry area was pre heated with shop hair drier to help. No real problem but close inspection will show there is a little difference; cloth is not quite as well compacted and has a very slight cloudy appearance due to air bubbles.

    I will have to say if I was going to make a rudder like yours my first thought would be to mold two halves (vacuum bagged) and then then glue together with a micro balloon slurry. It's the way I made the sculling oar for QB which has about a 42" span and 5 1/2" chord and turned out well.

    I've 3D printed about 20 kilos of stuff so far, about half of it boat related. I'm curious about how you're going to do a whole boat. I haven't done any calcs but 20% gyroid infill, my favorite, probably can't hold a candle to conventional core foam (PVC, SAN or GPET) for shear modulus/strength or density.
     
  10. laukejas
    Joined: Feb 2012
    Posts: 823
    Likes: 25, Points: 28, Legacy Rep: 128
    Location: Lithuania

    laukejas Senior Member

    I see... This is what troubles me. Although I plan to use proper materials (purpose-made infusion mesh and other consumables), I'm still not sure how to lay out the lines to ensure this doesn't happen to me.

    But that would require making molds, which is exactly what I'm trying to avoid. For a one-off design, it's just wasted material, which is extra cost and not really environmentally friendly. Besides, even micro-balloon slurry will be heavier than a 3D printed core...

    I'm using much lighter configuration: 1 wall (0.4mm), one top and bottom surface, and 6% Adaptive Cubic infill. With this, I get a density of around 30kg/m^3, which is better than most foams out there. I haven't tested it separately, but it feels about as strong as common PU foam, and handles compressive loads really well. When combined with a composite and put under stress, composite fails first. I did some experiments in the lab that showed this. I suppose it is not as strong as purpose-made core foams, but the convenience and cost factor makes it worthwhile for me.

    As for the boat, I plan to print the hull in pieces that fit my printer (350x350x320mm, about 120 pieces), glue them together with CA, sand, seal, and infuse like I described in my first post. It is all doable, but the size of the boat scares me - I really need to place the infusion lines and vacuum points in a smart way to be able to infuse the entire hull at once. Hence this post :)
     
  11. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    A boat size thing with a printed core with one layer of 0.4mm top and bottom might be pretty fragile, I really don't know. Another consideration if the skin has a pin hole epoxy is going to fill a substantial part of the core.

    I also don't know what kind of boat we are talking about. If it's more of a surfboard configuration without an inner space things seem more doable.

    I admire your stepping out and trying some new that shows promise but don't have anything to contribute other that than I've already done.

    Do the rudder and learn from that and let us know. Best wishes.
     
  12. laukejas
    Joined: Feb 2012
    Posts: 823
    Likes: 25, Points: 28, Legacy Rep: 128
    Location: Lithuania

    laukejas Senior Member

    Yeah, it will be quite fragile until carbon fiber is added, but so would be foam. The hull shape looks like this:

    upload_2024-12-28_4-22-42.png

    Wall thickness varies from 8mm to 35mm approximately. Here is a cross-section of the midships for reference:

    upload_2024-12-28_4-24-16.png


    (Subfloor will require special attention, but I got a solution for that).

    As for pinholes, yes, you are right, I have forseen this. Like I wrote in my first post, the plan is to seal everything with thin layer of epoxy and lightweight fiberglass so there are no pinholes, and the hull cannot soak in epoxy or collapse during infusion.

    Thank you for sharing your experiences and pictures. Hopefully someone else will give some more suggestions on that infusion layout. I am still waiting on some materials, so I will be infusing that rudder no earlier than 2 weeks from now :)
     
  13. seasquirt
    Joined: Dec 2015
    Posts: 249
    Likes: 111, Points: 43, Legacy Rep: 10
    Location: South Australia

    seasquirt Senior Member

    Can you re-print your rudder in two mirrored halves, maybe with some peg/hole locating features; or tongue in groove around the edges ? Then you can do a good job on each half, like Skip advises, to your liking, then do a final bond together, no molds needed. Don't ask me, I've never 3D printed or vacuum bagged anything. Soon a vac bagging / composites expert will be along with advice. You can experiment with the rudder you have, and if not perfect, it can be a spare; any boat is better off with a spare rudder, even if kept home.
    For infusing the boat, could you have the hull vertical, resting on the bow, so the resin travels up in a level progression / flood, until the transom is thoroughly soaked and bubbles stop rising? Injection at the bottom, vac on the top. I did this with my plywood dinghy after major bow surgery, sealed outside with aluminium foil, upended, and poured in resin into a dam, left to set. Now the strongest part of the boat. It was difficult balancing it, leaning slightly into supports, and waiting for still air outside.
    Could you make all your 3D printed parts stronger, each individually sealed, and they snap and lock together like lego with added lock pins, with something like velcro to hold it from unlocking? No glassing done. A bag of bits in the car, and a mast on the roof.
     
  14. laukejas
    Joined: Feb 2012
    Posts: 823
    Likes: 25, Points: 28, Legacy Rep: 128
    Location: Lithuania

    laukejas Senior Member

    Thank you, these are some really interesting ideas. Yes, I can re-print the rudder in 2 pieces, but that would kind of defeat the purpose, since this rudder is a test piece for the entire boat, and I won't be able to do this for the boat.

    Interesting idea. I didn't think that gravity would play such a role in infusion, I always thought that force from gravity is minuscule compared to vacuum and wouldn't impact anything. I am not yet sure if the printed boat will be rigid enough to place her like you suggested. But in any case, EasyComposites guys say that the distance between infusion lines and vacuum should never exceed 500mm, while the boat is 4.5m long. So there is no chance that the resin would travel that far in this bow-down configuration.

    I tried to imagine that and had a good laugh, thanks :D

    Waiting on that expert you promised!
     
    Last edited: Dec 28, 2024

  15. Skip Johnson
    Joined: Feb 2021
    Posts: 113
    Likes: 71, Points: 28
    Location: Lake Tenkiller, Ok, usa

    Skip Johnson Senior Member

    I hope the expert shows up.

    Thanks for the images, makes it easier to understand what you are wanting to accomplish and the issues involved. Some years ago there was a similar craft on one of the earlier Texas 200 adventures we nicknamed the Tie fighter, awesome performing boat, far beyond my capabilities even back then.

    The ideal method of making such a craft, especially one off, with minimal effort and waste isn't here yet. In my younger days I'd probably consider hotwiring XPS foam in sections and then fairing same before adding composite skin, I swore a mighty oath to never use beaded foam back then and haven't slipped except for a couple of wingsail pieces a few years ago.

    Carry on, I hope to see the art advanced a bit.
     
Loading...
Similar Threads
  1. Alistair Perrott
    Replies:
    3
    Views:
    1,205
  2. fallguy
    Replies:
    7
    Views:
    1,223
  3. Wesley2022
    Replies:
    6
    Views:
    2,423
  4. vroomZOOM
    Replies:
    8
    Views:
    3,215
  5. tuna_fan
    Replies:
    5
    Views:
    2,553
  6. Ryan Look
    Replies:
    12
    Views:
    2,947
  7. Tom Hickson
    Replies:
    4
    Views:
    2,050
  8. Garandpa
    Replies:
    9
    Views:
    4,519
  9. Keegan
    Replies:
    5
    Views:
    7,570
  10. tpdavis
    Replies:
    26
    Views:
    5,422
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.