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n7188u
Joined: 15 Nov 2015
Posts: 395
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 Posted: Mon Jul 31, 2017 8:58 am Post subject: Making fibers straight during UNI layup |
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Dear Europa group members,
I am currently working on the flap layups and I am finding that the time it takes me to do the layups is WAY too long for my taste. It took me 3 hours from the moment I started applying micro slurry to finish doing the top of the port flap.
What I find I am struggling with is making the fibers straight. I am using a pipe to roll the fabric and then place it on the surface. I also place a tape at the line where the bias cut is made in the fabric (which I think maybe causing issues when the fabric is placed in the core).
After I place the fabric on the core, I start pulling the fibers straight but it's not easy to get a good result since other parts of the fabric are already getting stuck in the epoxy. I do hold the fibers down at the LE and pull the fibers away from the surface at the TE to make them straight, but that action disrupts adjacent fibers that I already made straight.
Any techniques to help making the fibers straight? How straight do they have to be? I know that the straighter the better but maybe I am working too hard to make them perfect, which I am starting to believe is a hard thing to achieve. After all, every process has a tolerance.
BTW, at the end the flap come out OK but its a painful process I am hoping to learn to do in an easier faster way.
Best Regards,
Chris Martin
sites.google.com/site/martineuropaxsa291/
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spcialeffects
Joined: 29 Aug 2012
Posts: 305
Location: Kent
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| Posted: Mon Jul 31, 2017 10:47 am Post subject: Re: Making fibers straight during UNI layup |
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Hi Chris. Don't worry about how long it takes you to complete the task, the more you glass the quicker and better you will become. What I found worked best for me was to draw lines at 30 degrees on the foam core in both directions, then put down the micro slurry. Leave it there 5 or 10 minutes and then scrape it off. Now roll your cloth on dry following the lines the best you can. Once the cloth is on the foam don't try to adjust each individual strand try to look at the whole piece and get an overall straightness by pulling the corners to straighten the strands. When the weave is say 70/80% there then move the parts your not happy with. I think the tolerance is + or -10%. However doing it this way the only wetness is that of the slurry so you can quite easily move the cloth to correct the weave. Once your happy with the position of the cloth mix up some resin and pour it on the cloth and at first spread it around lightly so as to not move the cloth and once the cloth goes translucent then you can apply more pressure with the squeegee.
Hope this helps, good luck and enjoy,
Regards Frank.......classic kit #165
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keithhickling(at)clear.ne
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| Posted: Mon Jul 31, 2017 2:20 pm Post subject: Making fibers straight during UNI layup |
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Hi Chris,
I found the same problem, and what I found worked well was to make a simple
lightweight wooden frame from 15mm x 35 mm wood (about .75 x 1.25 inch) to
fit around the foam with a gap of about an inch all round. I rolled the
glass cloth out on the cutting table nice and straight, laid the frame over
it in the correct orientation, and cut around the edge of the frame with a
pizza cutter, leaving enough cloth around the edge (2 inches) to turn over
the edge of the frame. I then clipped the cloth over the edge of the frame
with bulldog clips every 12 inches or so all the way round. I found I could
then simply lift the frame / glass up, carry it over to the prepared foam
core and lay it down as 1 piece onto the core. Then remove the clips, lift
the frame away and usually there was only minimal straightening or removal
of wrinkles to do. When there are 2 plies to apply in 1 layup, you need 2
frames prepared with glass ahead of the layup.
It takes about 10 mins to make the frames for each layup but I found it was
well worth that. You can reuse the wood for subsequent frames. I can send
you photos if you like.
Good luck!
Regards,
Keith Hickling,
New Zealand.
ZK-MEE
--
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n7188u
Joined: 15 Nov 2015
Posts: 395
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| Posted: Mon Jul 31, 2017 6:13 pm Post subject: Re: Making fibers straight during UNI layup |
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Thanks for the replies Frank and Keith.
Frank, what you describe is similar to what I am doing now. It's not too bad but I am finding it hard to straighten the fibers. It seems that when I make one section straight, I mess another. And when I go fix the other, I mess the first one  But at the end it works out OK. One thing I don't think helps is that I apply masking tape to the biased cut line. Its nice for cutting but I think that when I place that line on the TE, any pull on the fibers at that end will distort adjacent fibers since they are joined at that edge.
Keith, your proposal is intriguing since I was thinking about something similar. I will think about that. Our parts are not that big and a small frame would probably work well. I had it with the "roll the fabric in a tube" technique which is not working that great for me.
BTW, I asked the Cozy group about it (I was building a Cozy before I got the Europa kit). In the cozy, UNI layups tend to be the big stuff (wings) so you use the whole width, unroll it over the wind and have two people pull at the ends of the whole width of cloth. You lift the whole thing, straighten and then bring down. That is hard to do with pieces cut to match the shape of the flap with biased cloth. Other suggestions from the Cozy group where the 'Spatula" idea (placing the cloth on a big flat piece of cardboard and then sliding the cloth in place, the portable roll to move in place for unrolling the glass over the part at the right angle, etc. But they all involve full width of cloth and dropping it over the part which I find a little wasteful for our small parts.
Best Regards,
Chris Martin
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graemeh
Joined: 15 Jun 2017
Posts: 17
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| Posted: Mon Jul 31, 2017 6:35 pm Post subject: Making fibers straight during UNI layup |
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I haven't tried it with UNI but the DIY prepreg method where you apply the resin to the ply between two sheets of plastic and then use the plastic as a carrier to put the ply on to the surface works very well with BID. I can't see why it wouldn't work with UNI and I'll certainly try it with my landing gear ribs when I finish off the work another builder did.
On Tue, Aug 1, 2017 at 2:13 PM, n7188u <chmgarb(at)gmail.com (chmgarb(at)gmail.com)> wrote:
| Quote: | --> Europa-List message posted by: "n7188u" <chmgarb(at)gmail.com (chmgarb(at)gmail.com)>
Thanks for the replies Frank and Keith.
Frank, what you describe is similar to what I am doing now. It's not too bad but I am finding it hard to straighten the fibers. It seems that when I make one section straight, I mess another. And when I go fix the other, I mess the first one But at the end it works out OK. One thing I don't think helps is that I apply masking tape to the biased cut line. Its nice for cutting but I think that when I place that line on the TE, any pull on the fibers at that end will distort adjacent fibers since they are joined at that edge.
Keith, your proposal is intriguing since I was thinking about something similar. I will think about that. Our parts are not that big and a small frame would probably work well. I had it with the "roll the fabric in a tube" technique which is not working that great for me.
BTW, I asked the Cozy group about it (I was building a Cozy before I got the Europa kit). In the cozy, UNI layups tend to be the big stuff (wings) so you use the whole width, unroll it over the wind and have two people pull at the ends of the whole width of cloth. You lift the whole thing, straighten and then bring down. That is hard to do with pieces cut to match the shape of the flap with biased cloth. Other suggestions from the Cozy group where the 'Spatula" idea (placing the cloth on a big flat piece of cardboard and then sliding the cloth in place, the portable roll to move in place for unrolling the glass over the part at the right angle, etc. But they all involve full width of cloth and dropping it over the part which I find a little wasteful for our small parts.
Best Regards,
Chris Martin
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spcialeffects
Joined: 29 Aug 2012
Posts: 305
Location: Kent
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| Posted: Mon Jul 31, 2017 9:42 pm Post subject: Re: Making fibers straight during UNI layup |
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Hey Chris. Yes if you tape up the end then any movement at one end WILL affect elsewhere. When I cut the cloth I just use a meter long metal rule and a pizza cutter. My aircraft is a classic with foam wings which I covered in uni. When the uni folded over the LE trying to keep the weave straight was probably my hardest challenge during glassing 😳
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