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Old Jul 19, 2011, 09:41 AM
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KevinSharbonda's Avatar
United States, MD, Lutherville-Timonium
Joined May 2003
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Help!
1 oz. R&G Kevlar/Disser layup techniques ?

Guys, how are you handeling the light Kevlar Disser material and can you give me some guidance on the layup for a bagged wing using this cloth? I'm doing a d-box disser layup over foamular 600 and am curious on the right way to handle the layup since the weave is so open! I don't want to overdue the epoxy but still don't want to make it to dry either! What do you recommend for getting the ratio exceptable or do I have to just go for trial and error till I figure it out? Thanks in advance - Kev.
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Old Jul 19, 2011, 10:09 AM
G_T
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From my limited experience with Phil, it works just like 1oz Kevlar but is easier to handle as the fabric is a bit stiffer. Treat like any Kevlar, but more hard rolling is required to close the weave.

Arrange a setup where one has an overhead light which reflects off the mylars. Now you can see the open spots as bright reflections. Use a wallpaper seam roller and some elbow grease to close up the weave. This is done after drydown.

Phil may give some better or more complete information. Or some other people. My only experience with it has been at Phil's shop.

BTW, with a D-box I'm presuming you are only using this fabric behind the spar. That far back on the wing, the surface texture is not quite as important as it is towards the front. In the front of the wing one should try to be very smooth.

Gerald
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Old Jul 19, 2011, 10:36 AM
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This is very odd timing. I was just in the process of cutting some of that fabric for a new Zone wing. It's only the second time I've ever used that fabric and I was just becoming frustrated because I couldn't figure out how to mark that fabric for cutting. A pencil is bad because it leaves lines in the layup. The scratch awl doesn't work on that fabric very well. I haven't had any disappearing ink markers in my shop for many years. Then I remembered; I should be using a wax paper transfer method and so the patterns would be traced out on the wax paper with a sharpie marker. All that stress made me want to take an RCgroups break and, how odd it is to find this thread.

Gerald mentioned a couple of things about that fabric: It has a more open weave than the 1.0oz plain Kevlar fabric and so it takes a lot of hard rolling to even attempt to close up the weave. One correction/clarification though; Don't fully dry the layup before doing the hard rolling. The epoxy acts as a lubricant between the fabric and the mylar. When the layup becomes very dry, the fabric becomes very fixed in place on the mylar. If the layup is soupy wet then when you try to hard roll it, the fabric may want to swim around on the mylar too much. On the other hand, if the layup is too dry, it will be very hard to close up the weave with the hard roller. The hard rolling will work best with a moderate amount of wetness. For that fabric, I will try to hard roll it at every stage of the process in hopes of finally getting it to look good. It is also going to be important to have the mylar on a very flat, hard surface for the rolling.
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Old Jul 19, 2011, 12:28 PM
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United States, MD, Lutherville-Timonium
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Thanks guys, the main reason I asked is yes fabric behind the spar and the fabric doesn't look like you could ever close the weave because it is more of threads than facric per say. It looks like 2 threads close together and then a space then 2 threads etc. I marked a line on my mylar for the edge of the spar and fabric then lightly 3m the mylar and layed it on the fabric and trimed the thrailing edge. I used a sharpy to mark the straight cut line along the spar and it won't show up there because of the black carbon. It was very tedious to say the least ! Masking tape was use to try to hold the fabric straight on the bias for trimming.
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Old Jul 19, 2011, 02:24 PM
Hey was that a Thermal ????
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It's funny the circles we run in. The carbon I have been using can be quite difficult at times and then I remembered the "Phil Barnes wax paper method".

I simply lay my fabric pattern on the wax paper and cut 4 wax paper skins. I spray mount those to my cloth and cut around them. I am even doing this with my glass skins because I can then do my lay-up even faster which is critical with my current shop temps.

You do need to make sure you get resin on ALL the cloth before you hard role because the resin releases the cloth from the wax paper.

Thanks again Phil for introducing some great techniques.

Paul
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Old Jul 19, 2011, 02:51 PM
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Phil,

Are you hard rolling directly on the wet kevlar? If so, how do you keep the roller from moving the kevlar?

Gary
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Old Jul 19, 2011, 03:19 PM
Hey was that a Thermal ????
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Gary, not Phil but I hard roll right on top of the wax paper. I do this with both my carbon and glass wings. This is why Phil is saying wet is good so the cloth sticks to the mylars but too wet and the cloth will slide around. The wax paper also helps the cloth keep it's shape.

Paul
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Old Jul 19, 2011, 04:11 PM
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Quote:
Originally Posted by GaryO View Post
Phil,

Are you hard rolling directly on the wet kevlar? If so, how do you keep the roller from moving the kevlar?

Gary
Important Note: The following post is talking only about the use of lightweight, open weave fabrics that require a wax paper transfer method for handling and require hard rolling to close up the weave of the fabric. Fiberglass layups and Kevlar layups with 1.7oz Kevlar do not require most of the methods discussed here. The lighter 1.0 oz Kevlar and the R&G 1.0oz disser Kevlar fabrics do require these methods or at least benefit from these methods.


Many different methods can work, but what I'm doing lately is as follows: I roll the fabric out on my bench. The bench should be smooth with no snag points for the fabric's weave to get stuck on. Any fabric that is finicky enough to require a wax paper transfer method is the type that will get distorted out of shape if it snags when being moved over a bench. Sometimes I'll even quickly run a sanding block over the bench to be sure it is smooth and then brush the dust off thoroughly. Then I roll the fabric out and I'll spend some time adjusting the fabric on the bench until the weave is all lined up properly and not running in all different directions. Then brush the fabric very lightly with a drafting brush to smooth it down flat to the bench.

I then reel off a long piece of wax paper and lay that on my layup bench (away from where the fabric is) and I put a very light spray of 3M77 on it. I just spray horizontally a foot or two above the wax paper and let the mist settle on the wax paper, just one quick spray. I pick up that wax paper with one hand on each end and drop it in place over the rolled out fabric. I usually will align the wax paper diagonally on the rolled out fabric, usually there is a bias cut end on the fabric anyway so I just follow that edge, or I lay the wax paper parallel to one of the diagonal lines on my bench. For the Zone wing I just did, I had to lay three strips of wax paper side by side on the fabric to cover enough of the Kevlar. I taped the joints of the wax paper with masking tape after laying the wax paper down. If you do this, be very sure that there are no gaps between the sheets of wax paper. The tape will not release from the fabric without a great deal of grief. It's OK if the wax paper overlaps a bit.

My fabric patterns are just made from poster paper and I trace around these with a fine point sharpie marker which writes very nicely on wax paper. I try to remember to make lefts and rights, but when I forget I just have to put wax paper on the other side of half of the pieces and pull the first piece off.

I have my mylars laying on the layup bench, lightly tacked to the bench with 3M77. I roll epoxy on the mylar and then drop the wax paper backed fabric in place. I'll just lightly press the fabric down until I see that it is all wet out. There is a lot more epoxy on the mylar than what the layup needs at this point so it easily wets out the fabric. I then pull the wax paper off. I roll the fabric with the hard roller as soon as the wax paper is off. At this point the fabric is very wet with epoxy so I have to roll gently to avoid moving the fabric around. If the fabric still moves then I would have to put some paper towels over it and hard roll that gently to remove some epoxy. In general, the wetter the layup, the lighter the pressure you use with the hard roller. I'll generally take every opportunity to hard roll.

Next step is to dry the layup in a vacuum bag. I just move the mylar over to the bagging bench and put a layer of paper towels over the wet out fabric. Then I invert the other mylar, face down on top of the first. So you now have the two mylars face to face with paper towels in between. If I'm doing a full wing with four mylars then I'll make a stack of all four mylars in two pairs with paper towels between the wet faces. That goes into a vacuum bag and sits there while I finish prepping the core. I used to try and time how long it stays in the bag to get just the correct amount of epoxy out. Lately I just let it stay in the bag a long time. It just reaches a point where the paper towels are saturated and they won't take any more epoxy. This is also a point where the layup is too dry, all the remaining epoxy is concentrated near or at the mylar face and there is almost none on the face that will be against the foam core. If you bag the wing with the layup like that you'll get a wing like my original Zone wing that delaminates the skins with every slight impact.

The mylars come out of the bag, the paper towels are removed and the mylars sit face up on my bagging bench. I then roll the skins again with the hard roller. This time I'm pushing real hard with the roller because the skins aren't going to move at all. Then I take my foam roller that is used to spread the epoxy and add a little epoxy to the layup again. For this application, the roller needs to be almost dry, just a little epoxy in it. You want to add just enough epoxy to get a little bit of a sheen. Also when you press your finger into the layup, you should be able to just see a little epoxy ooze out around where your finger was. If you press real hard with your finger tip and still can't see any epoxy and if you don't see that little sheen of epoxy then the skins likely won't stick well enough to the core.

As the last step before putting the cores in place, I'll add epoxy to critical areas of the layup. This always includes the trailing edge area. I'll run a stripe of epoxy about a 1/2" wide along the trailing edge of each mylar. Make it sloppy rich epoxy. This will make the wing trailing edge durable so it doesn't turn to mush every time you touch the wing's trailing edge. I also run a narrow (maybe 1/4" wide) strip of epoxy on the hinge line areas. I have a mylar template that I lay over the layup. This template has a window cut in it where the hinge lines are. This ensures that I get a nice narrow strip of epoxy in just the right place. If the wing has prefaced hinge lines then this extra epoxy over the hinge line is not needed and actually is hurtful because it floods the hinge gap with epoxy and makes the hinging job difficult.

The wing is then ready to bag. I didn't talk about some details such as adding doublers, spar rods, etc. I only mentioned the bits that related to wetting out and hard rolling the main skins.
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Old Jul 19, 2011, 05:54 PM
Hey was that a Thermal ????
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Thanks Phil that was really detailed and very helpful. I will try rolling after I remove the wax paper to see if the carbon weave gets closed up even more.

Paul
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Old Jul 19, 2011, 10:51 PM
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Thanks, no worries ! The weave flattened out nice and my suspicions were unfounded! Thermals dudes !
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Old Jul 19, 2011, 10:54 PM
It's a mere flesh wound!
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Quote:
Originally Posted by Phil Barnes View Post
I haven't had any disappearing ink markers in my shop for many years.
Phil...Is there any reason to not use the disappearing ink markers?

Buddy
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Old Jul 20, 2011, 08:04 AM
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They work well but they don't last very long and there are other ways of doing the job.
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Old Jul 20, 2011, 11:08 AM
Aurora Builder
United States, MD, Lusby
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Phil, thanks for those tips, they are extremely useful. I will be using them on my next wing layup as I have switched to the carbon Paul is using for select areas (leading edge D-Box, flaperon doubler) and in a quest to save weight will be reducing my glass usage down to the minimum (aka, not covering carbon with 1.2oz glass, especially in the d-box). I have had problems leaving the skins in the bag for too long and getting a too dry layup, you have presented a method that should solve that issue.

Are you still facing your ailerons on the Zone V2 series of wings? I can see how it would be needed and I had to do it on my Zone v1.5 but I think I need to launch harder on the v2's before it becomes a factor.

I think you need to re-make your excellent bagging video with some of these more modern techniques so the rest of us can get good wings!
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Old Jul 20, 2011, 11:54 AM
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I always preface the flaperon leading edges, and also the trailing edge of the main wing. Besides stiffening the flaperon, it prevents the wing skin from debonding at the hinge line.
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Old Jul 20, 2011, 12:03 PM
Hey was that a Thermal ????
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Phil, what do you use as a spacer between the wing and the flaperon. Brian has been using mylar.

Paul
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