Peel ply....

Discussion in 'Materials' started by Roly, Oct 28, 2006.

  1. rxcomposite
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    rxcomposite Senior Member

    One of our guys would always salvage the used peel ply. He says that when it is laundered, it makes for a good sail for his small sailboat. For the still smaller pieces, he sews them together. What a great way to recycle.
     
  2. Yellowjacket
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    Yellowjacket Senior Member

    Does anybody know a source for polyester film to use for covering laminating.

    The only stuff I've found thus far is a 4 x 8 sheet of.030 inch material. I haven't been able to find a roll product and I would prefer a narrower width. The cost of 4x8 sheet was reasonable (about $35), but for what I'm doing a narrower sheet on a roll would work better for me.
     
  3. rwatson
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    rwatson Senior Member

    I cant see what area of the world you are in - but look for the trade name Mylar, that seems to be pretty common in most parts of the civilised world. It comes in rolls.
     
  4. lewisboats
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    lewisboats Obsessed Member

  5. themanshed
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    themanshed Senior Member

    I've also used 3M painting plastic. Make sure the 3M emblem side is down towards the wet work, if backwards it will stick. Test a small piece to get use to the method. When working with foam and epoxy I mix a little bog with the epoxy to get the foam pores filled by brushing on the mixture before my first lay-up. Then do a regular layup. I use an auto body type plastic squeegee; the plastic is thin and works out well the squeegee action will remove the excess epoxy by working it to edge. Once it is dry the 3m plastic comes right up. Make sure you leave some extra 3M painters plastic overlap that stays dry on the edge to use to pull it off, easier to grab no chance of glue over. A roll can be purchased at most paint or home project stores like Home Depot and it is cheap. This method gives the effect of both vacuum bagging and peel ply.
    The picture below I was puting a two layer lay-up of 200 gram carbon on foam for my bulkheads.

    Just a note I only use peel ply (costly) when doing a vacuum bag job so the excess can bleed though to the bleeder cloth all other times I use the above method and I'm still on my first roll of cheap 3M painters plastic.
     

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  6. Charly
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    Charly Senior Member

    Hi the manshead,
    That stuff is only about 4mil thick isn't it? And the the vinyl stuff is about 30 mil thick? It sounds like the thicker stuff might make a fairer surface on a large area, like a hulls exterior. Does the thickness make a big difference? I am curious because I hope to be coating and fairing my two 36 foot hulls is a few months. They get one layer of 10 oz cloth over okume ply. I have been assuming that I would fair it, lay-up the cloth, coat it again while tacky and then peel ply, hopefully then to have very little sand prep before priming. Now I am thinking maybe to go with the vinyl instead of peel ply and just wet sand the whole thing before priming. What do you guys recommend?
     
  7. Yellowjacket
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    Yellowjacket Senior Member

    The best thing I have found so far is PTEG sheet. At $32 per 4x8 sheet it's going to cost about $130 to do what I have to do. Not too bad, but not cheap for a throw away piece of plastic.

    Most of the Mylar I've found is pretty pricey. To buy enough Mylar to cover the hull I am doing is going to cost almost as much, or more, than the epoxy that I will use. It's looking more like $200 or more to do the boat I need to do. For a pair of 36 foot cat hulls you are talking at least a thousand bucks for that much sheet, so if the vinyl works for that it could save a bundle.

    The mylar I've found is limited to mostly .014 thickness. The guys using it for RC airplanes have found .014 mylar to work pretty well, but they are using pretty light cloth. If I have to go with Mylar I'm thinking that .014 is a minimum thickness that will work well.

    Lewis boats, What thickness of the vinyl did you use?

    I had seen that marine vinyl at Online Fabrics, and wasn't sure if it would work all that well. The vinyl is a lot more flexible than an equivalent Mylar sheet. More chance to get wavy surface and uneven amounts of resin under the sheet. The price is right though. The boat I am doing is made up of relatively flat sheets so the stiffer material for me the better it is likely to work.
     
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  8. lewisboats
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    lewisboats Obsessed Member

    I am not sure exactly what the thickness I used...I bought it at Walmart in the fabric department and it didn't really say except that it was the "thickest". I expect it was 15 or 20 mil judging by the roll plastic I use at work which is 4 mil.
     
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  9. themanshed
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    themanshed Senior Member

    Charly,
    The hulls should be fare before fiber glassing. So what you are trying to do it is to get the lay-up on as smooth as you can. The 3M painter’s plastic is thin and light you can work the material - epoxy and lay-up really well and see your work as you go. Plus the 3M painter’s film does not mind shaping some to your piece or surface. A little epoxy on the squeegee edge as a lubricant works good and lets you glide along. The finished parts come out very smooth. A little scuffing and you are ready for the Yacht finish.

    I've not used the thicker plastic, Mylar, or vinyl. Those materials always seem to want to fight you when you use them as indented. They kind of have a predetermined shape that they like to keep - flat - and wrinkle or bulge when they meet a curve. Plus all the weight you are talking about as the length gets longer not sure how that matches up with epoxy and fiberglass.

    Peel ply is ok but you do not see your work and the parts come out with a matted surface. Peel ply is great if you want to do more lay-up, but the hulls still would need more work to put a shine on it. The cost is way too much. The only problem I have is that I need it for the bleed through for vacuum bagging if it was not for that I’d not use peel ply.

    For the minimum cost of a small roll of the 3M you should try it on a small panel for a test. This method makes a very compressed lay-up that you would think was vacuum bagged. I read about this method as an alternative to vacuum bagging several years ago in some reference material. Anyway it is neat trick I like and use, and if you do not like it when you paint your house you can always finish up the roll of 3M painters plastic. As always take several ideas test them out and find out what works best for you, your build, and your wallet.
     
  10. Charly
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    Charly Senior Member

    Thanks guys.

    I will do a few experiments before I commit to the hulls. I used some six mill poly over a rather large hull patch a few months back. It worked OK, but the end result was uneven resin (Wavy) thickness. Maybe I didn't squeege enough resin out of the cloth after I put the plastic on. There was also a problem getting it smooth where there was a crease in the plastic, as it comes folded up on the roll.
     
  11. Yellowjacket
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    Yellowjacket Senior Member

    I'm going to do the heavy fim trick on my boat. I've found the .030" PTEG (trade name Vivak) sheet for a very reasonable price at a local plastics shop. Meyer plastics has it for $26/sheet. I shouda looked locally before I spent hours on the web looking for the best price.

    I'm doing a plywood sheet hull with it and was curious if Par could chime in since he has done the plastic sheet trick process previously (and obviously knows his way around the epoxy patch). I'm planning on using a fairly thin resin (600 cp Raka) for wetting out the cloth since I want to wet out the glass well for a clear finish (and also Raka 350 is realllllllyyyyyy sloooooooow which is what I need).

    The question is, when using the thick plastic process, is it better to use a thicker more viscous resin or will the thin resin work just as well. I'm thinking that the thinner resin will wet out the cloth better, but have a concern that the thinner resin would mush down the cloth more and won't leave as much resin on top of the cloth. I guess I can go back and put another coat of just pure resin on the top after I take off the plastic, but that kinda defeats the process to some extent.

    Also, Par, when you are doing this do you squeege as much out of it as possible or do you leave it a little bit wetter and just roll the excess out from under the plastic???
     
  12. rwatson
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    rwatson Senior Member

    If you are putting mylar over the top, it doesnt matter as to the epoxy thickness, as it will just hold it all in place, even on a verticle surface.

    Is you hull made of developable surfaces only ?

    If it isnt, the thick plastic will cause big blobs where it cant lie against the fibreglass cloth.

    I suggest you do a couple of small test panels first to make sure the stuff will peel off later, and get the feel for the epoxy you are using.
     
  13. Yellowjacket
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    Yellowjacket Senior Member

    The boat is all developed plywood surfaces. It is a classic racing runabout from the late 70's. The mylar will have to be pieced, but this application is exactly what the process was designed for. There won't be any issues with bunching or blobbing, but the middle of the bottom the hull is done in two strips that that are a foot wide (13 ft long), and two subsequent on each side that are about 8 inches wide and eight and 10 ft long. Since I'm doing relatively long strips I want a slow epoxy so that it isn't setting up one end by the time I get back to the end where I started and start the next srip.

    I plan on doing some interior surfaces first, but wanted to know if you squeeged it out to be relatively "dry" and then put the mylar on, or if you left it relatively "wet" and rolled out the excess epoxy with the mylar on it. In describing the process some have said it actually uses less epoxy because when you roll out the mylar it compresses the cloth (somewhat like a vac bag, but not as much pressure).
     
  14. rwatson
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    rwatson Senior Member

    Sounds like you are on the right track.

    The Mylar will compress slightly, but no more than a good squeegee job would, as the fibreglass cloth is un-compressible. The air pressure against what is virtually a vacuum makes helps a lot. The trick is to do a slightly sloppy job of squeegeeing the goo onto the cloth at first, so you have little bits of excess at intervals.

    Apply the mylar from a roll, (roll it around a hollow pipe, which is suspended by a rope through the pipe, that you can move along the hull) starting at one end, and use a hand roller and/or dry squeegee to smooth it down as you go.

    You will find as you hit a dry spot, that you can often 'roll' some excess goo from an adjoining area into the dry spot, or worst case, back off the Mylar by about 6 inches, and put a bit more goo on the problem area. (Be careful not to lift or wrinkle the cloth as you do.)

    The trickiest bit is to make sure you have aligned the Mylar roll with the hull panel before you start. You can get a third of a way along the hull and see that the mylar edge is too high or too low, and you are going to end up with 6 inches or so uncovered at the other end. If that happens, dont try and re-lay it, just cut out some more mylar into a triangle and cover the exposed bit.

    Don't expect to get a finish that will require no sanding entirely, but it will reduce the amount of sanding hugely. Often the Mylar will have a 'bump' in it made by folding, or a production fault, that will make a slightly thicker bit of epoxy than required. Or, you may find a bit of the hull that has a 'dent' or a rise. These are easily straightened later with a long fairing board.

    Don't be scared of scuffing up the surface with 'sandpaper' after you have removed the mylar. If you use 'wet and dry' quality fine paper, say 120 grit to finish, the protective coating will restore that deep lustre with no problems.
     

  15. Yellowjacket
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    Yellowjacket Senior Member

    rWatson, Thanks, that's the kind of advice I was looking for.

    The hull is 13 ft long and has a 56 inch beam, and the bottom has to be done in one coat with no stops. The hull is very well defined in that each section of the bottom is one strip of plywood that isn't twisted very much and it will be pretty straightforward to make the mylar to fit. Thanks for the overhead roll trick, I will definitely do that for the wide center section. The other sections are pretty narrow, only six and eight inches respectively, so I can just roll it up and handle those narrow strips.

    I'm don't think I can wet it all out and then put down the mylar before is starts to gell, so my plan is to work in strips. This is one reason I bought slow epoxy.

    The current plan is to start in the middle, work from transom to bow in a two foot strip, leaving a couple of inches wet past where the mylar will be, and put down the center strip of mylar. Then do a single 6 inch side strip on each side (which should go pretty quickly), and then follow that with a final 8 inch wide strip on each side.

    One other approach is to work from one side, the epoxy doesn't have time to start to set up along the next edge before I get there. Probably have to be careful with how the cloth pulls over the bow edge as I work it but I won't have a problem with the epoxy setting up before I get to the next part. Also it might be easier to keep the mylar aligned with the one edge as I go along. I'm thinking I could probaby keep each section of mylar lined up with the previous section and avoid (but not totally eliminate) a lot of recutting and fitting the mylar.

    Any thoughs you have on the approach are most welcome. Perhaps I'm over analyzing it, but I only get one shot at this without making a mess of it and it's a lot cheaper and easier to carefully plan what you are going to do and then do it as opposed to trying to figure it out on the fly.
     
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