Vacuum bagging tutorial

Since we are spending most of our boat building time on laminating panels on the vacuum table now, I though it would be useful to describe my process.  This is basically the same process described by other, more professional types of experts.  Note that in this example I am just laminating one side of the panels at a time so I don't have to punch a million tiny holes in these foam sheets.  Laminating both sides simultaneously is quicker (by almost exactly a factor of two), and can use less material.  If I were to do this again, I would buy some perforated foam core to make panels.  Nonetheless, the end product is just as good in either case, and plain foam core is a bit cheaper.  So here we go (take notes as there will be a test at the end!):

1)  Start by preparing all of your materials.  You will need:
- The foam core cut to the desired size and shape, and pre-sanded to remove any residue that would inhibit bonding with the epoxy,
- The glass fabric cut a couple inches oversized,
-  Peel-ply cut a little bigger still,
-  Perforated release film so it doesn't stick to the bag, and
-  Breather fabric cut large so the air can get out.
I also have a rectangle of sealing tape laid out on my table top with the vacuum bag sealed along the back edge.  I also have the vacuum feedthrough installed in my vacuum bag and the pump ready to go.  Note the vacuum bag is really just the top layer that seals to the table top.  The table top forms the bottom half of the "bag."  On my roll cart I have my epoxy (paint) tray and roller set up and waiting.  The more you can do before you mix epoxy, the better.

2) Now that we are ready to laminate, let's mix some epoxy!  I use pre-marked mixing cups to make measuring easy.  These cups from Noah's have marks for various mixing ratios and quantities.  I use an electric drill with a paint mixer attachment to mix the resin and hardener.  I have found I need about 45-mL of mixed epoxy for every square foot of laminating.  Regardless of quantity, I always mix for 2-minutes.  I adjust speed of the drill to compensate for quantity, and try to avoid sucking air into the mix.

Here is a tip I came up with for joining pieces of foam core into a single panel.  I just staple the pieces together on the face NOT being laminated.  This hold the seam together until the first side is laminated.  When I flip the panel, I remove the staples and epoxy fills the holes during the second lamination.  In this case, the panel needs to be about 47-inches long, but the  sheet of foam was only 46" wide.  So I just used a piece of scrap foam to cut a 1-inch strip and joined it to the larger panel.  Once laminated, it is as strong or stronger than a single piece of foam core.




 3)  Now it is time to wet the foam core with a good coating of epoxy.  You could skip this and do a "dry lay up," but I think it is good to work some epoxy into the foam texture before laying on the glass fabric.  Although air entrapment should not be an issue on a vacuum lamination, I figure the less air the pump has to suck out, the less likely there will be an unexpected issue.

4) Once the foam is wet, I carefully lay the glass fabric on the foam, ensuring there is glass over all of the edges.  I then stroke the fabric along the direction of the fibers to get rid of any wrinkles.  Be careful here or you can make it worse.

 5) Now you can roll on more epoxy to saturate the glass.  I find it works best to roll on one stripe of epoxy at a time.  Then move to the next stripe while the previous one soaked in to the glass.  You know it is working because the glass disappears.  In this photo you can see how the glass becomes transparent when saturated (right half).  You don't need to over-saturate the glass, just enough to make it transparent with no white strands remaining.

6) As soon as the glass is saturated with epoxy, lay the peel-ply on top.  Try to lay it out carefully with no wrinkles.  Once it starts to absorb the epoxy It will become more difficult to adjust.  If you move it around too much it will start to drag the glass which can make a mess.  In general, less handling is better with all steps of the lay up.  The peel-ply serves a couple purposes.  First, it absorbed excess epoxy, which result in a lighter, stronger part.  Second, once peeled off, it creates a surface that is ideal for bonding to epoxy during later assembly.  Third, it creates a very smooth and uniform surface.

7) Now roll over the peel-ply to set it into the wet epoxy.  I start by making a cross through the center of the panel.  Roll slowly so the peel-ply sticks to the panel and not your roller.  Don't add any extra epoxy, rather let the peel-ply soak up the excess epoxy from the glass.  This step is another that is not really necessary, but I think it helps avoid problems later.  I think this step helps ensure the peel-ply doesn't get creased when pressed under vacuum.

8) Now you can lay the perforated release film on top of the peel-ply.  This film prevents the breather fabric from sticking to the part being laminated.  The film has small holes punched through to allow air and excess epoxy to escape.

9)  Next on the stack is the breather fabric.  There are various types, but I like the high-loft type that feels like a fluffy blanket.  The breather need to overlap all edges to give air a path to escape when the vacuum starts.  I cut it long and then fold a pleat at one side where the vacuum feedthrough will sit to serve as a manifold for air escaping under the pressure.

 10)  Now the vacuum bag layer is layer on top and sealed to the table via the sealing tape (yellow) around the perimeter.  This takes some practice to get the seal uniform without lots of leaky wrinkles.  Be careful about pulling the bag too tight when sealing because it may pull the sealing tape off the table once the vacuum starts and the bag stretches to conform to the shape of the panel.  Notice the vacuum feed trough nipple at the far end of the table on top of the breather fabric pleats.

 11) On goes the vacuum hose and the pump starts sucking the air out.  I continue to massage the seal to work out leaks.  I found my ears to be the best leak detectors.  I walk along the seam with by ear almost touching the table and listen for leaks.  Once the seal is tight my pump runs until it reaches its set point and then kicks off until the pressure creeps back up.  You can also use a continuous running pump with no reservoir.

As the atmosphere presses down on the evacuated stack of materials, excess epoxy will seep through the holes in the perforated release film and get absorbed in the breather fabric.  This is good for making a strong, lightweight panel.  I am working at almost 7000 feet altitude, so I don't have as much atmosphere to press down with as those of you at sea level, but it is still adequate to make an excellent panel.

 12)  After the epoxy cures for a few hours (6-12 hours, or more, depending on the temperature), you can remove the panel.  If you are careful, the vacuum bag with sealing tape and the release film can be reused.  The breather is best used only once.  The excess glass and peel-ply can now be trimmed with a sharp knife.  If you do this within 24-hours, the knife will cut the excess off very easily and cleanly.  If you let the epoxy fully cure over days, it gets tougher and may require more effort to trim.

And Voila! here is your laminated panel (or half laminated if this was the first side).  To do the other side, just repeat the above steps.  With a little practice, this is very efficient and you will be able to make super-strong lightweight panels.  Initially the process can be frustrating due to excessive mucking with the layers.  Remember, less handling is always better, and the process is generally self-correcting.  So far I have not had any panels come out looking bad, much less unusable.  The same cannot be said for my effort laminating by hand (see discussion about the first float half about a year ago).

Starting to install flat panels

We are still laminating bunches of flat panels on the vacuum table.  I have finished about half of the panels from the full-size plans, and also noticed there are several panels that are cut to fit.  This is going to take a couple more weeks to work through (if only the day job didn't take up so much of the day!)  However, we have now started installing these panels in the port half of the main hull.  Here is a photo of the aft cockpit and side deck installed.  Technically, these are the last components of the deck to be installed, rather than interior panels.  Nonetheless, the flat panels are starting to get used.

As we have done with other panels, e.g bulkheads, after trimming to fit, we bed the panel in epoxy putty, form a nice fillet (in this case only along the inside seams), and tape in place with 12-oz double-bias glass and epoxy.  I am also finishing these seams by applying peel-ply over the tape. Once cured, I peel off the peel-ply and the result is a smooth join with no evil epoxy-glass spikes along the edges.  You can see the result looks very clean and professional (said with a thick southern accent).  I have most of the panels ready to assemble the rest of the cockpit required at this stage, but I need a couple bulkheads before proceeding.  More to come ...

News Flash: Farrier to discontinue boat plans!

I recently saw a post from Ian Farrier announcing that he will discontinue his sailboat building plans on Sep. 25, 2012!  Apparently he is focussing his attention on developing his production boat business again.  He is currently planning to start production of his new F-22 design.  He notes there are several quality builders that are licensed to build his designs.  He also mentions availability of kit boats, which might be interesting for someone wanting to build without as much time commitment.

In any case, if you have been watching this blog with the intent of trying this yourself, you may want to get your plans very soon.

Panels, panels, and more panels

 Now that the port hull interior is fully glassed, it is time to prepare the myriad of flat panels that reinforce the hull and divide the volume into various spaces.  These flat panels are best laminated on the vacuum table.  As discussed previously, I am applying the glass and epoxy to one side at a time rather than perforating a couple hundred square feet of foam core.  Unfortunately I got a little hasty today and tried flipping the first set of panels too early.  The epoxy was fully gelled, but still too soft to release from the table easily.  To make it even more difficult, I didn't place a sheet of release film under the panels, so I had to use a thin scraper blade to free the overrun epoxy from the table.  I will be sure to wait a good 6-12 hours before trying to remove the panels from here on, and I will need to thoroughly clean the table for the next set of panels.

I tried to precut some of the materials for the dozen or so sets of panels.  Laminating one side at a time requires twice as much release film and absorbent matting, and I ran out.  So I will be placing an order for another 50 yards of each.  I have enough supplies to get through about half of the panels, so I have a little time before I need the additional materials.  As we slowly make progress, our stock of materials is dwindling.  I will probably need a few extra sheets of CoreCell foam core as well, but I think we will be close to the planned quantity.

Here are some of the cut foam panels awaiting their turn on the vacuum table.  It took the better part of a couple of days to cut all of the panels.  I transfer the full size plans to poster board and then use the poster board templates to trace the shapes on the foam.  I think this method is much easier and more efficient than transferring the plans directly to the foam.  The laminating will probably be going on for the next couple of weeks.  But I am fabricating both the port and starboard half of the panels, so this will all pay off once we get to the starboard half of the hull.

The glassed deck

Last weekend we finally glassed the interior of the deck.  As planned, Dawna got stuck on the inside while I supplied fresh batches of epoxy from outside.  It was also quite warm, in the 90s by mid-day, so we had to move fast to keep ahead of the epoxy cure time.

The lamination came out quite well, thanks mostly to Dawna's talent.  After three hours in the hull wetting out glass with epoxy, I offered to finish the aft end of the deck and give Dawna a break.  Of course, this was the only area where we had any bubbles form in the laminate.  Lesson learned: Never give Dawna a break!  It is very difficult to see the bubbles under the laminate, and the white splotches of putty filler tend to camouflage the bubbles.  In any case, I will have to grind out the bubbles and add a few patches of glass fabric.  In the end, my "oopsies" will blend into the hull, but it is frustrating to do all that work so carefully and still have some blemishes.