Mylar transfer method...

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#1

So I tried the mylar transfer method suggested by WYOWINDWORKS in previous post… http://www.compositescentral.com/showthread.php?t=7124

This method works great for epoxy but when I tried it with vinylester resin the mylar immediately started to curl up and deform (some sort of adverse reaction with the vinylester resin) so using this method to pre-wet out a 4" by ten foot laminate for my wing leading edge probably wont work because the mylar will be totally deformed and wrinkled before I finish pre-wetting out the laminate.

Question: Do any of you know of another material that I can substitute for the mylar that wont deform when used with vinylester resin? The material must peel away from the wetted out cloth as easily as the mylar AND it must not stretch since the laminate is 10’ (feet) long. (I had planned on using a helper, he and I at each end of the wetted out laminate/mylar holding it taught while we lower it down on to the wing leading edge (the wing will be in a jig oriented vertically so the leading edge is facing up to make positioning the wetted out laminate as easy as possible).

Any suggestions for an anlternate material? Could I use release film for this? What about vaccuum bagging material?

#2

Since mylar is made from polyester then the vinyl ester must have messed with it.

Is there some reason that you are wanting to use vinyl ester over epoxy? If you are looking for a good aircraft certified epoxy resin you might consider MGS 285. This epoxy will cure harder, stiffer, and with a higher HDT of any room temp cured epoxy that I have used. I know that the mylar transfer method will work very well with it.

The advantage to the .014" Mylar transfer method is that it will generate a smooth surface which reduces and in some situations eliminates the finish work. Release film or bagging material will just transfer wrinkles to the surface.

Adam

#3

The two main reasons that I wanted to use ve resin over epoxy is (1) the aircraft is constructed with ve resin and (2) ve resin that I’m using has a much higher HDT (220 degrees f approx) than any roon temp cured epoxy that I’ve found. Also I was planning on using the mylar (or whatever works) just to pre wet the long laminate and then transfer said laminate to the wing le… with the laminate in position I was going to remove the mylar lay a layer of perf release film, then a layer of breather material and vac bag it…

#4

Since I just plan on using the Mylar (or??) just long enough to pre wet the laminate and get it into position on the wing le… wouldn’t vac bagging plastic/film or even release film work (if using release film I could save a step and leave the release film in place on top of the laminate, then add breather & bag it… I’ve not used release film before though so I don’t know if it is as resistant to stretching as the Mylar is… thoughts?

#5

FYI the material has to be non stretchy because the laminate is approx 4-6" wide by 10’ long… it will be 7781 glass cut on a 45 bias. due to the width of my 7781 glass roll the laminate will have to be made of 3 pieces placed end to end… to get a narrow but long pre wetted laminate transferred from the material in question to the wing without ruining it or pulling the joints apart (would be the case if the material stretches) is going to be a challenge I think…

#6

Release film usually is too thin, try a 0.002"or preferably a 0.003" vacuum film (nylon)

#7

If your plan was to remove the mylar then the mylar would be a bad choice of material. It would be hard to remove because of it’s stiffness. Something more flexible like bagging film would be easier to remove.

Honestly, I would just lay the raw fabric in position on the bonding surface and then wet it out. The downside to pre-wetting and using carriers is that you will get more bubble entrapment between the laminate and the bonding surface.

#8

I have thought of wetting out the laminate on the wing leading edge but I’m concerned with two things… (1) the ve resin that I’m using gels in 15-20 min and I don’t think I can wet out a 10 foot by 4-6" laminate AND bag it in that short of time… pre wetting is much faster because you can pour a thick bead of resin down the middle of the cloth (cloth is laying on top of whatever material is used to transfer to the wing) lay a piece of Mylar and squeegy out the excess resin… remove the Mylar and transfer the pre wetted cloth to the wing… quickly work out he large bubbles and bag it… (2) how to avoid getting too much resin on the cloth resulting in a big mess of excess resin drooling down the wing where its not wanted.

#9

Can’t you add less MEKP to the VE to increase the working time. I think you be struggling, regardless of the method, if the gel time is only 15-20 minutes.