Preview: How to Vacuum Bag, Part 2 – Watching it Happen

46 Responses So Far to “How to Vacuum Bag, Part 2 – Watching it Happen”

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  Alan Gideon says:

  The motors of most shop vacs are cooled by the air passing thru the inlet hose. No flow, no cooling, motor over-heats, vacuum lost. No fire, if you’re lucky.

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  Jason byl says:

  Great series with some great advice, I would like to add a note in hopes of saving someone else some time.
  -the bubble wrap as flow media works great with an exception, if you’re using it to laminate a cloth on top of a substrate the bubble wrap definetly prints through. I’m building a new rudder for my 1/4 tonner and had a laminated cedar blank CNCd. Today I vac bagged skins on the outside of each half using bubble wrap as the flow media, it definetly left an inprint in the fabric, so I have some fairing to do now. It’s slight and not a big deal, but I wouldn’t have used the bubble wrap had I known so. Otherwise a very informative series.

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    Jason byl says:

    * breather cloth, not flow media.

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  Gieri Cosson says:

  Thanks, very comprehensive instructions. Looking forward for the following videos. Would love to learn about cold-molded veneer with vacuum construction.

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  Tyler Trowbridge says:

  Great series of videos. I too would like to see the complex shapes video in a part 3.

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    Nate Rooks says:

    Tyler – it’s on its way, featuring a very interestingly-shaped carbon part with Russell Brown.

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  Mikkel Pagh says:

  Hi Steve, Eric,

  Thanks for a great video. I would love to see more of this! Hull bagging or bagging of other complex shapes.

  – Mikkel

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    Steve Stone says:

    Thanks Mikkel. That’s on our list.

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  Robert J England says:

  Very interesting videos. Thank you! For this particular part, how did you account for the additional thickness of the plywood added to the finished thwart, or was that necessary?

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    Steve Stone says:

    Hey Robert, good question. In this particular case, the bit of extra thickness wasn’t an issue other than getting longer bolts (given that I sail the boat hard, often full of kids, dogs, camping gear, etc., the extra thickness provides confidence without notice of any aesthetic tradeoff). If the ending thickness had a tight tolerance, Eric could have planed the core to the needed thickness before bagging the plywood on.

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  Michael Seibert says:

  Very interesting video. My understanding is that, when gluing with epoxy, you need to avoid clamping things so tight that all of the glue is squeezed out of your joints, leaving you with a dry joint. I understood you to say that vacuum bagging creates tons of pressure on the wood, and that it removes all of the air and voids in the glue job, but I am concerned that, in doing that, you might be putting the kind of pressure on your glue joints that we have been advised to avoid? Is this something to worry about or am I misunderstanding things?

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  John Simlett says:

  Thanks Eric. As usual you make things sound and look easy to do. The list of suppliers at the end, together with prices and models is really useful.

  Thanks a lot!

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  Robie Gardner says:

  I know that this doesn’t have anything to do with vaccum bagging, but I recognize the forward thwart off of Geoff Kerr’s caledonia yawl he built for OCH. I’m thankful I chose solid sapele lumber verses laminated pine stair treads. Have any other twarts delaminated? Thanks.
  Robie
  Portsmouth, VA

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    Steve Stone says:

    Yes, our hardware/lumber store acknowledged a bad batch of wood with faulty adhesive and refunded our purchase. This happened previous to getting wet or experiencing any stress. It’s the only such circumstance of this we know of as this is the only time Geoff has used stair tread (at our request if I recall, because we liked the idea of making the point of using inexpensive options from the local lumber yard). We see many of Geoff’s boats throughout each summer and they are flawless.

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      Robie Gardner says:

      Thanks for the explanation. I almost purchased the stair treads for myself until I came across another substitute. I’m just curious though, will you be laminating and vacuum bagging the rest of the thwarts and seats or will y’all build all new?

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        Steve Stone says:

        Not sure yet. It’s an aesthetic issue and not functional so no hurry.

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      Geoff Kerr says:

      Let me add that the OCH boat is the only time I have used glued-up stair tread as stock for the seats. That choice was made as a function of time, budget and local availability. The southern yellow pine stair tread I get in my neighborhood is clear and solid. I have also used sipo and northern white pine at times, depending on customer wishes.

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    Weaver Lilley says:

    Yes, my yellow pine mast partner was starting to check. I saw Eric’s videos and decided to give it the same treatment. Dependable vacuum pumps start at $300. I discovered a skate board site which sells pre-made bags for $89 which vacuum by a supplied hand pump similar to the pumps used to vac oxygen from opened wine bottles. It worked beautifully and the mast partner is painted and ready for spring. As far as the thwarts checking, it’s more of a cosmetic problem easily dealt with by paint and filler.

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  Allen Sawyer says:

  Good video, y’all! Informative and demystifies vacuum bagging. Thank you.

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  John Foad says:

  Thanks Eric. Very educational. The amount of detail is much appreciated.

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  Philip Prather says:

  Thank you for this . Lots of great info. I’m looking forward to the next videos on this topic!

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  Sean Scully says:

  Good Video, Next time I make a re-curve bow going to try it. THANK YOU

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  Bruce Perry says:

  Lots of mysteries solved for me with this video series. I am looking forward to the next one. Thank you for sharing.

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  Kevin Tisdall says:

  Would peel ply between the envelope and part on the bottom and between bubble wrap and part on top help reduce the sanding needed once the epoxy cures?

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    Thomas Dalzell says:

    Yes it would, and that is why they use along with smooth diffusion layers and other bits. I have to say for the amateur, the cost of all these components when purchases at aircraft quality product levels, and all the solid waste produced is daunting to me. I used to wince at the cost of the cloth an epoxy, now it seems every new membrane is the same cost as the glass itself, and more stuff end up being thrown in the garbage than ends up being used. Meanwhile, I have endlessly reused my bubble wrap, I have some on rolls from the 80s when I did my trimaran.

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  Lou Volpe says:

  Once again, a great instructional video. Good job Eric, thanks for making videos that are detailed and very useful.

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  Dennis Dunn says:

  Eric:
  What if you want to finish the outside panels bright? How can you keep epoxy off the outside surfaces so that the cured epoxy won’t interfere with the varnish? You can sand of course but then you risk sanding through the veneer.

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    Eric Blake says:

    Hey Dennis
    Good question.
    The plywood I am sanding in the screen shot is 3mm or 1/8″ thick.
    The face veneer of 3mm ply is less than 1mm thick and if you are paying attention you wont sand through this getting all of the epoxy off. Something that you are intending to finish bright I would use a thicker/ solid wood, but regardless you have to watch what you are doing and keep the sander flat.

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  Richard Whiting says:

  Two great videos. You guys are the best. Please come visit the MATHEW TURNER in Sausalito, CA soon! Lower masts are now stepped, bow sprit in place, decks all done. Interior is being fitted as I write. Can’t wait to meet you guys!
  Capt. Rick

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  James Long says:

  When I worked at United Airlines (SFOMOC) as a mechanic in 2007 I worked in a repair area repairing acoustical panels made out of a honeycomb material and Kevlar. There was a silicone heat blanket adhered to the panel that sometimes would get damaged and would need repairing or replacing outright. We would fashion a vacuum chamber much like this set up for the blanket R & R. A sleeve of plastic sheeting sealed on both ends with 3M Weatherstrip caulking. The part inside and a Transducer device installed on an air hose with the weatherstrip caulking sealed around the Transducer. Plug in air hose and watch the fun begin. Pressing on the caulking to get rid of air leaks. The part would look like it’s vacuum wrapped. 24 hours later the high temp RTV silicone sealant cured between the silicone blanket and the panel repair complete.

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  Bill Bouldin says:

  Another great video! I must say that vacuum bagging was mysterious. Now I’m looking for something to stick together. Very cool!

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  Mal Botterill says:

  Hi Eric what happens to all the bag material, reusable or more plastic waste?

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    Eric Blake says:

    Mal,
    We are looking into a durable reusable vacuum table membrane and many shops who are bagging the same objects over and over again certainly use them. Typically we are bagging huge parts, and the risk of using a second hand film isn’t worth the risk. We certainly try and use up large bags for bagging smaller parts, but there is always a use in a wood epoxy shop for scrap plastic. There is a waste stream involved for sure, but if done correctly I would like to think that there is a long term waste stream savings in maintenance and life expectancy going forward.

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      Alan Mudd says:

      Back in the mid-90s I worked at a composite boatbuilder building rowing shells. Everything was vacuum bagged, and between the hull and deck parts (each 27 feet long) the amount of wasted bagging material was insane. Can’t begin to tell you how guilty I felt looking at that overflowing dumpster at the end of every work day.

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        Thomas Dalzell says:

        I agree, I think it is very wasteful, however wood bagging is different, in that the parts are not always wet on their surfaces and as such I have reused the bags a lot, I would start with a really big bag and do many parts, trimming the bags as the edges wore out from sealing. We would also find any holes and plug them, you can hear the holes even with the racket of the pumps, though we had pretty high volume pumps.

        Making composite parts, the waste is huge, but there is the payback to an extent in making such high quality parts, saving on materials in the parts, and possible a lot of fuel in operation of the vessel.

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  Chris Methot says:

  Eric

  You implied, but never specifically said that the vacuum process would pull the check splits together (since most of the pressure is on the large flat surfaces, not in on the edges). Once the edges are cleaned up it would be nice to see that they are pulled up tight. I suspect they are.

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    Steve Stone says:

    Good question. I checked the ends after sanding and all looked filled and/or pulled together. Hard to know for sure about the interior but my suspicion is that all that liquid-ish epoxy is despatately seeking voids at the pressure of an antique Caprice Classic, and I’d prefer it filled with epoxy rather than clamped without epoxy and bet that’s what happened most.

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  Doug Hermann says:

  Excellent series. thanks

  Does the vacuum bag method provide horizontal clamping pressure, in addition to the vertical pressure?

  Thinking of those splits in the thwart, did they tighten up as well, or just get filled in with epoxy?

  Thank you

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    Eric Blake says:

    Doug,
    There is pressure from all sides yes.
    My guess is that the crack was clamped 90% back to its original state and the rest filled with glue 100%.

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  Mikkel Pagh says:

  Love it! Looking forward to the next episodes!

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  Matthew Nienow says:

  Excellent piece. Cheers!

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  William McCaffrey says:

  Good video series… looking forward to future segments.

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  Bruce W Kratky says:

  Nice tutorial. I use a manual reverse hand pump to create a vacuum when making long boards with youth I mentor. Amazing the forces envolved and how effective the little pump is. I have not invested in a powered unit, but after viewing these two videos I just may. Thank you.

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  Ian Thomson says:

  Thanks for demystifying the process. I am looking forward to the next installments. Incidentally what abrasive were you using to remove the excess epoxy? It seemed to come off so effortlessly!

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  Glenn Holland says:

  This is GOOD. Eric,Thanks a lot. Most of the videos that you see are from equipment mfgs. and seem to be just trying to sell you the equipment. That’s OK but this is better. Looking forward to more.

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  Larry Cheek says:

  THANK YOU for the comprehensive detail in these two episodes. Eric anticipated and answered every question that was forming in my mind as we went along.