Beam Pin Vacuum Infusion Help Please

Discussion in 'Boatbuilding' started by Fanie, May 8, 2009.

  1. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Attached is a pin for my folding beams I'm about to vacuum infuse. It is very tightly wound around the former. Length is 650mm and the glass is 16mm thick.
    It gets a layer peel ply also.

    Initially I was convinced the resin will seep through it easily, but seeing how thick the glass is I have a bit of doubt.

    Would any one comment on this please

    I was thinking of feeding the resin from the ends to the centre.
    Or feeding it from the bottom horizontally to the top horizontally.

    I have about 30 minutes before the resin begin to kick.
     

    Attached Files:

  2. kroberts
    Joined: Mar 2009
    Posts: 318
    Likes: 12, Points: 18, Legacy Rep: 210
    Location: Chicago area

    kroberts Senior Member

    Based on the time of your post, you have either already wasted a pot of resin or you have tried it out and it either worked or you wasted the whole project.

    Have you done infusion before? I have not, but I've done some reading, some tools collection and some talking to those who do it commercially. So I have book learning but no experience yet.

    In my understanding, how well the resin infuses into the part depends both on the viscosity of the resin and on the weave of the glass. And the size and shape of the part, of course.

    Some weaves are designed for infusion, to let the resin in. Also, the thinner the resin the easier it is to infuse. If that pin is regular woven glass, then I think it would be hard to infuse completely, especially with a standard epoxy.

    The guys I talked to use resins specifically designed for infusion, and they seem to run like water. Those resins (that they use) need a post-cure in an oven though. I understand some people use standard epoxy but thin it down until it's pretty runny.

    Either way, let us know how it turns out.

    How big is that pin?
     
  3. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Hi ken,

    I have done a little, but limited.

    The pin is 150mm ID, 600mm long and I want the wand thickness 16mm.

    The resin I have is for injection, much thinner than the regular stuff, almost like water.

    I have just done a test vacuum on it and it is not going to work as is. The vacuum compress the glass so much that it makes unregularities on the glass surface as a result of the diameter declining. Despite that I have wound it extremely tight.

    There is another method I have been pondering and that is to make a metal jig, take the glass off the former and put it inside the metal jig, Put a baloon or tube inside and pressure form it instead... I can then go to 5 to 10 bar on it. That should make it tight :D
     
  4. kroberts
    Joined: Mar 2009
    Posts: 318
    Likes: 12, Points: 18, Legacy Rep: 210
    Location: Chicago area

    kroberts Senior Member

    Is the strength direction mostly shear or something else? Maybe you could use unidirectional and orient it all the same direction, or maybe wrap two layers at a time, each oriented slightly differently. That might make the compression ripples go away.

    I tried the pressure thing once. I got the same thing you got, only in reverse. The glass tries to stay small and an epoxy "bubble" happens, where there is no glass but epoxy. I got ripples on the inside then.

    Here's another possibility. If you wind such that the cloth weave is at 45 degrees to the axis of the pin, then when you hit it with vacuum on your existing form, the part will actually lengthen a bit maybe, or at least with the pressure thing and a female mold it would shorten as it expands.
     
  5. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Hi Ken,

    I have considered the 45 degree but it's a lot of work and difficult because there are then so many loose pieces of glass. this also makes it difficult to maintan an even thickness all over. The woven I have just rolled up, took probably half an hour to get it done properly.

    If the former could expand the bubbles may be forced out, but how to make the former axpandable.

    As far as I know pressure formers have a male and female, you lay the wetted glass in it and the two gets squished together under high pressure.


    I have another question. Is the pin strength compromised if it is two halves that fit into the beam and the housing instead of a solid round ? It can't fall out or go out of position. The same idea is used in automotives ie the valve stem clamps are two thick washers contained by their housing.

    How about if the pin has a slit in the one side ?

    The idea is to give the glass room to expand to when it gets vacuumed.
     
  6. kroberts
    Joined: Mar 2009
    Posts: 318
    Likes: 12, Points: 18, Legacy Rep: 210
    Location: Chicago area

    kroberts Senior Member

    Re: 45 degree layup: You can buy cloth which is woven in a 45 degree orientation instead of 0/90. Slightly more expensive, but not if you count the time you waste cutting all that glass, or the number of cycles it takes to wash the glass fibers out of your clothing after you got done. Well worth it IMO, for something the size of your project. Just about every glass vendor I've found online has it, or did a couple years ago when I last looked.

    Strength of a split pin: I'm not an engineer. I can't answer that for you.

    Female mold and pressure former: I used a piece of pipe and a bladder made of vinyl-coated nylon made just for the project. My project wasn't nearly as massive as yours, particularly in number of layers. The bladder was bigger than the ID of the project, which did not matter that much. What mattered is that half the glass fibers prevented the thing from expanding to the pipe, and the epoxy bubbled in there.

    Keep in mind that on a project the size of yours I don't know if a 45 degree weave is going to scrunch down enough to avoid your ripples, but it might be. You wouldn't be able to wind it tight, but you also wouldn't WANT to.

    You can get metal split pins (can't recall what they're called) at the hardware store, it's a spring steel tube with a split down the side. It's sound in principle, the pin expands to fit the hole exactly. Your application though I can't say. You're not really doing the same thing. IMO your groove would simply fill with epoxy and create a weak spot.
     
  7. Guest625101138

    Guest625101138 Previous Member

    Fanie
    This is something I have only given a moments thought and not something I have tried.

    I expect your glass wrap is still quite porous. I think if you mounted the tube vertically with resin feed from a bottom ring while pulling a vacuum from a top ring with the whole thing sealed wrapped the resin would migrate quite quickly and disperse evenly.

    You could do a preliminary check to see how easily the vacuum pump pulls before you add resin. I do not think you will need any channel material. In fact this may cause preferential flow up the outside.

    When you think how far you can infuse resin through a thin layer this one "should!!" be easy.

    Will watch with interest.

    Rick W
     
  8. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Thanks Ken and Rick,

    I have a simple question regarding hand layup vs vacuum infusion.

    If one have the same amount of glass, does the vacuumed item come out stronger or is it only stronger for it's thickness.

    Ok I understand you use less resin and you gain on weight by vacuum infusion.

    My logic tells me that the same amount of glass, though a bit thicker should be just as strong when you hand layup as what the vacuum infused part will be, in fact, the hand layed up part should be stiffer than the thinner infused item due to the additional thickness.

    Have I got it wrong ?
     
  9. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    On the glass wrap, yes the vacuum draws the bag flat quite quickly and the roll should be porous enough.

    Ken I was going to use HDPE extrusions of 110mm dia for the pins, it would be easier to buy them as to making these. The HDPE pins can carry 30 tons of shearing which would be enough, but they were friggin expensive and the glass at 16mm can carry > 100 tons. Never the less, I want the pins, beams and their bulkheads to be an overkill, you never know that gets throwed your way and it must not even be an issue in any kind of weather.

    The pins are only big on your lap. Out there they are going to look very small :D
     
  10. Guest625101138

    Guest625101138 Previous Member

    Glass is stronger than resin. The more glass you can get into a given volume the stronger the part. Any air bubbles give potential to get water logged and the water will eventually destroy the glass to resin bond as it works its way in.

    The main advantage of vacuum is the air exclusion and high clamping force with no need for heavy weights or hydraulic rams. The bagging will also conform to the shape.

    If you are concerned about infusion then wrapping a pre-impregnated glass will work. You can add the wrap and vacuum after you have formed it. That will provide the pressure and pull out any air.

    Rick W
     
  11. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    I would defenately like to vacuum every item for the boat. On the pins alone I can save a lot of weight.

    The glass per pin is 5kg. If I hand layup it the weight will be around 10kg per pin. A vacuumed pin will weigh around 7.5kg's. In total that's 60kg's vs 45kg's. Which girl do you prefer, the 60 kg one or the 45 kg one :D

    Doesn't sound like much but it calculates to 15kg's. If everything gets added 25% in weight the boat will become unnessesary heavy and cost 25% more in resin. Quite a bit in total. On a 2000kg boat it adds 500kg's. It's going to haunt you when you trailer, launch or sail the boat, and you may have to leave some drink on the beach to save on the payload :D

    I'll take a bit of time and see if I can come up with something sensable. It always feels to me like I'm missing the obvious.
     
  12. jim lee
    Joined: Feb 2007
    Posts: 368
    Likes: 20, Points: 18, Legacy Rep: 247
    Location: Anacortes, WA

    jim lee Senior Member

    What side is critical? Inside or outside?

    -jim lee
     
  13. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Hi Jim, the outside is.

    Once it's done it will be trimmed with a lathe, varnished etc to form a very smooth fine fiberglass outer surface.

    The beam housing will be formed as wet glass around the pin for a snug no play fit. I tested doing it that way and the play is 0 while it hinges very nicely.
     
  14. jim lee
    Joined: Feb 2007
    Posts: 368
    Likes: 20, Points: 18, Legacy Rep: 247
    Location: Anacortes, WA

    jim lee Senior Member

    If it is the outside then I'd try a mold shaped like a cup. Maybe split down the middle for release? Shoot the gel inside, drystack it. Bag it from the open end. Flow from the bottom, breath at the top.

    But 16 mm is really thick, your going to get a lot of heat going on there. can you find a resin that will work for this?

    Where does the 16mm bit come from?

    -jim lee
     

  15. Fanie
    Joined: Oct 2007
    Posts: 4,604
    Likes: 177, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Vacuuming it on the inside brings other problems Jim, for one you cannot see and you cannot 'help' the flow.

    Besides, if the outer diameter is shorter than the cup then the glass won't fill the cavity, it's going to be either an air pocket or a resin pocket.

    The 16mm thickness is to make it strong enough to keep the beam attached to the hull and the beams hold together, The boat is foldable, so the beams fold in half and the hulls can be moved together or apart.
     
Loading...
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.