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Laminate Thickness

Old 08-29-2010, 01:51 AM
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Ghost_
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Default Laminate Thickness

Hello guys i am new to composites and i would like to ask how to calculate the laminate thickness.

For example is there a method or a matrix or something which tells you for example what cloth weight to use and how many

layers...??

Thank you in advance
Old 09-08-2010, 02:19 AM
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Ghost_
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Default RE: Laminate Thickness

Noone knows guys...??
Old 09-08-2010, 11:55 AM
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Default RE: Laminate Thickness

Laminating fabrics commonly used in RC applications vary in thickness from about .004" to about .010" thick. If you layup a 60 size fuselage with 6oz of fabric, you will get sufficient tensile strength to withstand normal flight loads, but is will be very "flexy". you can make it stiff enough by making a heavier layup, say about 10oz or so. A lighter, but more difficult way would be to make a composite sandwich. This would be a 2oz outer layer, a lightweight core of balsa or foam. and an inner layer of 3-4oz fabric. Again foam is easier to work with, and a little lighter than balsa, but balsa will be stiffer.

The website for CSTsales has some good technical info on specific fabrics. Also, carbon fiber and epoxy resin cures a bit stiffer for a given thickness than fiberglass.
Old 09-08-2010, 03:06 PM
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Default RE: Laminate Thickness

dreadnaut thank you very much for your answer do you now any specific layup for laminating wings
with core and hollow molded...??
Old 09-08-2010, 10:39 PM
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Default RE: Laminate Thickness

The wings can be layed up similarly to the fuselage. You will need just a few ribs and a vertical grain spar.
Old 12-13-2010, 05:00 AM
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Default RE: Laminate Thickness

Guys, The fiberglass for fuselages can be very thin applied to the mold. Say fine 3/4 oz woven glass first to give smooth surface, no pinholes. It's easy to apply, bends into corners easily. It wets out nicely, then apply a 1 1/2 oz or 2 oz woven to the mold. Lightly wet it out, then apply in the main areas of the fuselage "NIDAcore Matline 201" core material. This thin core material is very flexible. It is perforated with holes so it will bond top and bottom layers, it will not absorb epoxy, or polyester resin. It can be slit at the ends in pie shaped wedges to fit a pointed nose. It's ok if it has a gap. It only needs to fit into the main curve of the fuselage sides, leaving 1/4" or 1/2 " all the way around the edge of the mold uncovered. This edge will be seamed with extra glass tape when the fuselage halves are joined later. With the NIDAcore in place, apply one more layer of thin 3/4 oz woven glass lightly wet out. Place the whole thing on a vacuum bag. The pressure will compress it all into a very thin, light , and stiff fuselage side. Using this type of core material, builds bulk which stiffens the sidewalls. The thickness of the core material holds the last layer of glass you put in out from the first layers of glass. The perforations allow resin to weep through creating hundreds of very small bonding points that strengthen you laminate, without extra weight. If you built a wing and alternated glass, NIDAcore, Glass, NIDAcore, glass etc. You will end up with a thicker laminate, Very Very stiff, and Very light weight. Balsa sheet can be used as laminate core in the same way. But it will soak up resin into itself. NIDAcore will not, when you vacuum bag it, the excess will be pushed out. The only extra resin is at the perforations...which are needed, and not any measurable excess weight, for the small structures we are building. There are other core materials that will work, but I have used the full range of NIDAcore products. Go on line, and order their free sample kit, it has 5 inch square samples of each core material they make. Learn to use them in the right places, and you will have mastered the fine art of Strong And Light Laminations. Carbon fiber is great stuff, but a properly cored fiberglass laminate can be stiffer, Lighter, and more impact resistant than the fuselage made of several layers of Kevlar and Carbon fiber uncored. It will cost less, which is why I use it. Yes, If you use NIDAcore with kevlar and carbon fiber layers, it will be even stronger, than just glass. I just need it to be strong enough...you decide if you need it bulletproof. I hope this helps you guys, It works for me.
Good luck with your projects, John Taylor

Here is the NIDAcore site: http://www.nida-core.com/english/nid...honey_h8pp.htm
Old 12-13-2010, 05:44 AM
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Default RE: Laminate Thickness

John thanks a lot for your answer if you don't use a core what glass do you use...??

I use for example one layer of 1 oz then two layers of 6 oz and on the tail nose and wing saddle i use one extra layer of 6 oz
Old 12-15-2010, 12:56 AM
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Default RE: Laminate Thickness

John Taylor,
It was interesting to read how you use the Nida-Core MatLine as a light weight sandwich core material. According to Nida-Core's data sheet, it appears that the MatLine is primarily ment as a laminate bulker, saturated with resin. The resin consumption is given as 1.2 kg/m2, which would be far too heavy for our application.
However, according to your description, you don't saturate the material, the only resin in the core seems to be the resin that get wicked up through the holes, and this would be almost negligible.
1. Do you not end up with a soft/flexible core with little strength/stiffness?
2. Have you tried any of the other core materials, such as the H8PP and H11PP?
3. Do Nida-Core sell quantities suitable for hobby use?

Regards,
Magne
Old 12-21-2010, 05:25 AM
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Default RE: Laminate Thickness

Magne,
You need to order the free sample box from NIDAcore. They will send you a sample of all their core materials. Take the Matline and do a small test layup. There are several thicknesses included. I use the two thinnest they make, the most.

I use the Matline core for very thin laminate structures. It's often a 3/4 oz fine, tight weave glass, first in the mold, followed by a 1 1/2 oz layer, then matline core, and another
1 1/2 oz glass layer. I will add extra glass and core material to areas that need, extra strength, but as little as I can. I am at sea level here on the Texas coast, so I get a little more vacuum than other higher areas, but I do use all the Hg I can when molding a fuselage with Matline core. It compresses the layup a lot. I don't need the matline saturated, just through bonded to the last layer on top. It works.

Most of the fuselages you see made for RC models are just one or two layers of glass, no core backing glassed in. I don't know why. They will often just add another layer of glass, carbon fiber, or kevlar...to stiffen the fuselage, But it's still not rigid...like you would want. I see many, with the thinnest streak of carbon fiber tow, looking like a
marks-a-lot was used to draw a line down its length, with one layer of glass. The carbon fiber in that case will not help. I'm not sure they really think it's enough. Maybe it's just easier, cheaper, taking less time , and less money ...than adding core material that can really strengthen it. [:@]

To stiffen any structural laminate...you can use balsa, or even Dow blue panel foam. It will not absorb resin. ( In this case it's Better to use than Balsa) You can take it and strip 1/16, 1/8, or 1/4 thick strips 3/4 in wide. Use the strips, instead of the matline. You will end up with a glass layer formed over the rectangle shape of the foam...forming a sort of C-shape. It will be very stiff when setup. You don't get the strength from the foam, like a lot of people think. You get it from the structural shape of the hardened glass that forms the C. It stands apart from the first layers in the mold..backing it..formed as one solid laminate. The NIDAcore does the same thing...it's a thinner laminate...not as stiff as using the thicker C-shapes, but "STRONG ENOUGH". You might have to do it several different ways, to understand, or get to what you want, as strong and stiff enough...for your project, and the area you are building up. You can do it. Many times the stiffeners are only needed in the broad flat, or flexible areas of the fuselage. It's ok to space them as needed, and only long enough to strengthen the weak area you are concerned about. Like a tail area.

Divinycell foam and Hexcel foam are very expensive core foams, that don't absorb resin. They are pretty crush-proof. They are great for strong light laminates like Boat decks, interior light weight walls, airplane bulkhead formers, wing structures etc. You don't need them! When bonded between the glass layers where they are used...they do the same thing as the blue foam. They may be a little firmer to squash...but in the end, it's not the foam that counts, it's the glass formed around it, the "shape of the layup" as a whole that gives it the most strength.

There are other core materials I use a lot, that don't absorb resin. I use the round closed cell foam, it comes on a roll, that looks like a foam rope. It comes in 1/4 in, 1/2, 3/4 etc. Its very light and flexible, insulation used to stuff into open gaps, around doorjambs in new construction. I split it down the length, to form half rounds. Like the blue foam it gets a layer of glass over it to form a C-Shape, backing the main laminate in the mold layup. It's great stuff, because it can be formed, curved, circled, and glassed.
Even if you are not vacuum bagging it.

That layer of glass on top your core doesn't have to be perfect to be strong. I mean, wet out all the glass, but you don't have to saturate it till every pin hole disappears and the surface is slick. I often wet and roll out the last layer of glass on an 8 inch wide piece of Mylar, cut to whatever length I need. I lift or slide the glass onto the core, form it lightly and bag it. The vacuum will form it tightly around the core strips. It doesn't have to be all one piece either....you could use wet strips just wide enough to cover the strips and reach down each side, laying out enough to touch the layer below, and form a small flange the length of your strips. Which is the way to go, maybe, if your strips are spaced far apart, and you don't need a whole extra layer of glass, spanning between the strips. Lifting the glass after rolling out the excess resin, the glass is still wet, but you will see its got gaps, or pin holes, most the time , it is still going to be very stiff, and strong enough, when it cures hard. My point is its ok to have some pinholes. Think of a steel bridge with an open lattice of steel cross members, spanning the river. Wet open weave will still be pretty stiff shaped to the backing for your main laminate. It needs to be light. There's lots of other core materials you can use...even heavy dense ones work if you are building a battleship. My point is, to see the shape it forms in the glass...and not so much what the core is made of.

Have some fun.....Make your own 12 inch x 12 inch flat laminates on a waxed surface, to see and test it for yourself. Use foam dinner plates, just the flat center part. Use your medium weight glass. Lay up glass, foam piece ( with a few holes in it from heated t-pin), glass, foam, glass. Then another one...Just glass and resin, but add an extra layer of glass. The last layup piece... use the lightest glass you can find...layup glass, foam (with pinholes), and light glass. You can bag them all, or not , it won't matter for the test.
When cured out. Pull them up, and try to flex them. The last layup you did, will be as stiff as the all glass layup. The first one will be overkill...and very very stiff. Don't bend them to the point you break them....[>:] because you can use them to make bulkheads, electric motor mounts, or light weight flat panels. You will see my point on using light weight cores is best, instead of many layers of glass, is all I'm trying to tell you.

To answer you last question: The H8PP is a pretty thick honeycomb with scrim bonded to the stiff hexagon core. It's too thick for my projects, ( sailplanes), I have not used it. but could be used maybe in wings. The scrim helps it bond the rigid core to whatever you use top and bottom on it. The core strong is also good in sheer strength. Might work cut in thin long strips for wing sheer webs. The H11PP sample I have is glassed with thin layer of fiberglass, and white gelcoat already, top and bottom. Like in the video at NIDAcore...see the hammer test. It is tough stuff. You can figure the best use for it. I have not used it. It looks bulletproof. By itself, cut in thin strips, it might make a very good wing spar...nothing else needed.

Good luck on your project, yell at me if you have questions. I'll be glad to share with anyone, what works for me. [8D]

Merry Xmas and have a Happy New Year

John Taylor
Old 12-21-2010, 05:28 AM
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TexasThermalKing
 
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Default RE: Laminate Thickness

Ghost, What size, type, and weight of plane are you building? John
Old 12-21-2010, 08:50 AM
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Default RE: Laminate Thickness

I want to built a jart here is a link you can see the plane.. [link=http://jartworld.com/]Jart[/link] it's a slope plane about 56'' wingspan and a fuselage of about 1 meter
Old 12-22-2010, 02:24 AM
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Default RE: Laminate Thickness

Hey! Ghost, That's a nice plane...looks fast. I don't fly much slope...but it looks like a lot of fun. Do you have one now, or just looking to build your own version of it?
It's not hard to do, just stay close to the inbounds of what you see already works...to start. I mean, weight, span, tail moments ... a close clone maybe
with the airfoil you'd like to try. You can do it. John .
Old 12-22-2010, 07:53 AM
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Default RE: Laminate Thickness

Thanks for the encouragement John i am planning to scratch built it...!! I am a bit nervous about how it will go i am planning to do the molds
with polyester resin and 2mm Coremat to keep the cost down.I have some gelcoat but it is not tooling gelcoat do you know if this will be Ok to make the mold
surface from this..??
Old 12-24-2010, 02:21 AM
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Default RE: Laminate Thickness

Ghost, It's fine to use what you have. The Gelcoat is a good idea, it adds color to the molds inside surface. It will work fine. It doesn't have to be thick, just an even coat.
the right color, usually white, or black helps you see any bubbles in your layup. There are lots of videos on layup techniques, just take your time, study a little, and try it.

I have molds that are just natural resin, no color at all. I have used Polyester fiberglass resin, Vinylester resin, and many types of epoxy resins for molds. The poly and vinylester resins are cheaper for me...and done right you get just as many pulls off them. It's the prep for release that makes the difference. They work well even for epoxy laminated projects, like epoxy fuselages.

Your first layer over your plug should be a smooth coat of resin, no bubbles, gelcoat is fine, if you are going to have the inside of the mold colored. I use c-vail glass in tight areas first, where you see some use a putty made with resin and cabosil, or talc, or other filler. I don't like the putty, it is prone to surface cracking when stressed. The very fine c-vail is easy to use, very easy to wet out. Then followed by the 3/4 oz fine regular weave glass. Your layup of other glass weights, and layers after that, is really set by what you need for strength. Just glass might be fine, for a short, compact fuselage like you are looking at.

The more curves, and flare you have in the body will add to it's structural strength. You might not need core material, to get what you need for it to be strong enough. You can add bulkheads across the fuselage, and make it strong, even with a thin fuselage layup.

I have grandkids, and kids with out dads, I work with several days a week after school . They are 8, 10 and 12 and built a mold for their own projects. I helped, but they did just fine. They were mighty proud when the first one popped out, slick, shiny and no pinholes. One of them told me he liked building more than he did flying. He worked hard to get it right, the satisfaction of seeing it finished...makes him want to do it again. The moment of realization....they see they can do it, they did it and well. It's a great feeling for them...and seeing the change come over them is like they say...Priceless. You can do it.

Stay in touch, ask lot's of questions, you'll get a feel for what you need to do, even before you start. The simple problems can be avoided...just know what they are. Like mixing too much resin at once. It's wasteful but the real problem is it kicks faster. It's better to pre measure 3 small batches, resin only into separate plastic bowls, or pails. Have the catalyst if its poly or vinyl resin ready to mix quickly, when you need it. Same for epoxy hardner, if you use epoxy resin.

Don't use a fast cure setup...slow it down for you first few projects. I put the mold in a heat box, anyway, so it will set hard each time, no matter what. Plenty times the kids got one batch mixed hot, and we just, stopped using the resin that was kicking off, and followed with fresh mixed to finish and close the layup. It's not a problem, but you will find it confounding, if you aren't ready to deal with it.

Good laminate, has it's own plan, and flow. You lay it all out first. Then begin. You will need the small rollers, a few different shapes will help, to roll out the bubbles. They look like a finned aluminum tube. You've probably seen them. Keep some methylene chloride handy to quicky soak them, rinse off resin before it sets. It's easy to keep them clean often than, to clean them once it's set. We dip them often as we go along, one end of the mold to the other.

Have a Happy Holiday, John Taylor
Old 12-31-2010, 07:10 AM
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Ghost_
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Default RE: Laminate Thickness

Hello John thanks for your support... Next week i am thinking to buy some tooling gelcoat the guys from the composites shop told me that it provides better glossy surface
than the normal gelcoat and it is a bit tougher. I hope they say the truth..!!!

Thank you again
Old 01-01-2011, 08:09 AM
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Default RE: Laminate Thickness

I usually use 1 layer of 48 grm amd then 1 layer 200 grm.
I don't use gel coat but just spray the paint into the mold and lay up on that. Saves weight. About 5 thin coats dusted on. Here in Thailand they make a paint that dries very quickly which is the secret to easy release.
What really stiffens it up is a few lightweight bulkheads strategically placed for wing mounts, tail fixings etc.
Better to use a few bulkheads than make the whole thing heavy.
You can always use an extra layer of 200 around structural mounting point areas.
Wings have to be a glass/foam/glass composite done with a vacuum. Then joined with the spars in place.
Jim
Old 01-17-2011, 10:10 AM
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19grb57
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Default RE: Laminate Thickness

Hi John,
I came across your post while looking for some tips on doing light strong layups for wings and it seems you use the same procedure I have tried but my results need some refining.
I was going to send you this in a private message but decidedGhost and others may benefit from my experienceas well.
I have made several fiberglass molds and parts for models but this is my first attempt at a composite wing. I amusing 1mmNida Core in the part for added strenght and to keep the weight down.Ihave made a mold of the wing I want make parts from, 48" (1200mm)span double taper, about 475 square inches for a jet.
The procedure I used for glassingthis wing isas follows:
Sprayed the mold with gel coat, then 1 layer 1.5 oz cloth, then1 layer 3.2 oz 40x40 cloth. I then put the core in the mold and 1 layer of the 3.2 over the core.
When the resin was cured I thought it was to soft, meaningI could push my finger into the core throughthe top layer of glassand thought I should addanother layer of cloth on it. I used a layerof 5 oz on the top of the3.2 and then glassed it on and let it set. I joinedthe wing and let sit over night anthen demolded. It looked great, no pinholes, glass smooth surface and very veryrigid. Theproblem was the weight,it weighs 3lbs 3oz. (1.44 kg)Am I unrealistic in expecting this wing to be about half of the weight of what I have and still be strong enough to use on a 10 lb EDF.
I could have used it as a bumper on the front of my truck!
From what I remember when I was putting the 1st layer ofglass on the core it was absorbing the resin and that is why I thought it was to soft. When I was putting the 5oz cloth over the 3.2 I could seethe resin was going throught the 3.2 and into the core, I could see it changing color as the resin was being absorbed but thought I have come this far I am going to finish it.
My question is how do you use the mat without the resin soaking into it and gaining to much weight.
I don't want to go through the process of joining, then steaming balsa for a core for a weight saving process and gaing strength.
Thanks for any advice you may be able to provide on weight saving.

Gary.
Old 02-02-2011, 04:39 PM
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Default RE: Laminate Thickness

Ghost, most people are using a minimum of 3 layers of 6 ounce e-glass on a Jart fuse + a light veil layer. I would consider adding a forth layer from the wing forward. I would orient the fabric using a 0/90, +/-45, 0/90. The downside to using a sandwich construction on slope fuses is that the outside surface ends up being prone damage and puncture. The butted seams backed by tape are also very prone to splitting. Putting all the layers without the core and a solid wet seam/overlap is much moreresistanceto the tough landing that a Jart will undergo. You can use your mold to pre-make a sandwich strip that goes down it's length. On cured, you can remove it, resulting in a properly contoured reinforcement. You can add this to the inside of your fuse lay-up. This technique enables you to make a seam that is much more durable. This is called a hat stiffener. It can really prevent the sides from buckling and failing upon in impact.

You can do the wing without a spar using UD carbon like this(see 3.7 uni-web)on 0* with a 2 or 3 ounce balanced fabric on +/-45.
Old 02-02-2011, 04:54 PM
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Default RE: Laminate Thickness


ORIGINAL: 19grb57

Hi John,
I came across your post while looking for some tips on doing light strong layups for wings and it seems you use the same procedure I have tried but my results need some refining.
I was going to send you this in a private message but decidedGhost and others may benefit from my experienceas well.
I have made several fiberglass molds and parts for models but this is my first attempt at a composite wing. I amusing 1mmNida Core in the part for added strenght and to keep the weight down.Ihave made a mold of the wing I want make parts from, 48" (1200mm)span double taper, about 475 square inches for a jet.
The procedure I used for glassingthis wing isas follows:
Sprayed the mold with gel coat, then 1 layer 1.5 oz cloth, then1 layer 3.2 oz 40x40 cloth. I then put the core in the mold and 1 layer of the 3.2 over the core.
When the resin was cured I thought it was to soft, meaningI could push my finger into the core throughthe top layer of glassand thought I should addanother layer of cloth on it. I used a layerof 5 oz on the top of the3.2 and then glassed it on and let it set. I joinedthe wing and let sit over night anthen demolded. It looked great, no pinholes, glass smooth surface and very veryrigid. Theproblem was the weight,it weighs 3lbs 3oz. (1.44 kg)Am I unrealistic in expecting this wing to be about half of the weight of what I have and still be strong enough to use on a 10 lb EDF.
I could have used it as a bumper on the front of my truck!
From what I remember when I was putting the 1st layer ofglass on the core it was absorbing the resin and that is why I thought it was to soft. When I was putting the 5oz cloth over the 3.2 I could seethe resin was going throught the 3.2 and into the core, I could see it changing color as the resin was being absorbed but thought I have come this far I am going to finish it.
My question is how do you use the mat without the resin soaking into it and gaining to much weight.
I don't want to go through the process of joining, then steaming balsa for a core for a weight saving process and gaing strength.
Thanks for any advice you may be able to provide on weight saving.

Gary.
John, many people are using balsa for wing cores. The advantage is that is much less prone to denting when using lighter layups. You can mist it with hair spray to prevent it from absorbing excess resin. It doesn't require you to steam it. It will conform nicely with theassistanceof a vacuum bag. Often you can buy balsa as a "wing skin". These are wide pieces of balsa so no joining would be necessary.

Another option is to use a high density foam like Rohacell. These can be quite dent proof, consistent in thickness, conform under vacuum but are more expensive than balsa.

I would recommend not using gel coat as it's quite heavy. It is possible to paint the mold with the base color of you paint scheme. If the surface of your mold is nice then the paint will come out nice. If you use the right release agent then you can do the entire paint job in the mold. There is nothing lighter. I would recommend do a little test on a piece of waxed mylar to make sure that they paint you use is compatible with your resin. Some paint and resin combinations can leave a tacky exterior surface.



Old 02-04-2011, 05:42 AM
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Magne
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Default RE: Laminate Thickness

My question is how do you use the mat without the resin soaking into it and gaining to much weight.
Gary,
I have not used that particular core material, but the problem applies to a lot of porous cores, including honeycomb. (particularly honeycombs, in fact.)
What I have been doing in the past is to lay down the "inside" glass layer on a piece of polythene plastic, and wet it out there.
Then I put the polythene on top of the core material, with the glassed side down, and bag.
(Leave the polythene on the glass until the resin is cured, the polythene sheet can then be peeled off, as the epoxy does not stick to it.)
You can draw the outline of the wing on the reverse side of the plastic with a marker pen before you apply the glass, this will give a visible line to cut along before you transfer the polythene and glass.
Cut with scissors for a nice, sharp cut-line with no fraying.
I buy the rolls of polythene from builders merchants, it is generally used as damp proofing in house walls. I use 0.05mm thickness. (0.001" approx.)

Magne
Old 02-13-2011, 09:40 AM
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19grb57
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Default RE: Laminate Thickness

I had posted a reply to the answers last weekbut apparently my post did not make it through.
Thanks to Magne and Wyowindworks for your response to my question and the ideas you have given me.

"What I have been doing in the past is to lay down the "inside" glass layer on a piece of polythene plastic, and wet it out there.
Then I put the polythene on top of the core material, with the glassed side down, and bag.
(Leave the polythene on the glass until the resin is cured, the polythene sheet can then be peeled off, as the epoxy does not stick to it.)"

Magne,I am not sure I follow what you are suggesting here. What are you using for a core material. If you could walk me through it I'm sure I can grab the idea.


Wyowindworks, I have some questions with regard to your techniques. First, what kind of paint do you use that is resin (polyester)friendly. I have about 30 years experience in the automotive refinsh industry so painting is second nature to me. I agree that gel is heavy and I could save alot of weight by painting, plusputting on graphics would be easier. My thought on the paint in the mold technique is when asecond color was to be applied the tape covering the first color would removeit from the mold because of the wax on the mold surface?
Second, I have abondoned the use of Nida Core for use in the wings, it is a resin sponge! I have obtained some foam that is what I believe to be similar to Rohacell. It is resin resistant and seems to work quite well. It is a green foam that is quite lite. I found a piece that is 1/2 inch thick, I ran it through the band saw and got 3 pieces about 1/8 thick. I did a test layup as follows, 1 layer of 1.4 oz. and then2 layers of 3.2 oz., then the foam and one layer of 3.2 on top, put it in the bag until cured. I can't believe how rigid and light this piece is. It also seems to be very ding resistant. I am going to try a wing layup using this method. When checking the price of Rohacell foam this green foam is less than 1/4 the price and I can get it here in British Columbia.
It also does not absorb resin. With regard to wing layups does my formula sound like it will be adaquatefor a 48" span 10 poundEDF. What is the norm for spars and the material they should be made from. How much of an advantage is carbon cloth in the wing if "S" glass is 80% the strength of CF.

Thanks, Gary
Old 02-13-2011, 10:46 AM
  #22  
wyowindworks
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Default RE: Laminate Thickness


Wyowindworks, I have some questions with regard to your techniques. First, what kind of paint do you use that is resin (polyester)friendly. I have about 30 years experience in the automotive refinsh industry so painting is second nature to me. I agree that gel is heavy and I could save alot of weight by painting, plusputting on graphics would be easier. My thought on the paint in the mold technique is when asecond color was to be applied the tape covering the first color would removeit from the mold because of the wax on the mold surface?
Second, I have abondoned the use of Nida Core for use in the wings, it is a resin sponge! I have obtained some foam that is what I believe to be similar to Rohacell. It is resin resistant and seems to work quite well. It is a green foam that is quite lite. I found a piece that is 1/2 inch thick, I ran it through the band saw and got 3 pieces about 1/8 thick. I did a test layup as follows, 1 layer of 1.4 oz. and then2 layers of 3.2 oz., then the foam and one layer of 3.2 on top, put it in the bag until cured. I can't believe how rigid and light this piece is. It also seems to be very ding resistant. I am going to try a wing layup using this method. When checking the price of Rohacell foam this green foam is less than 1/4 the price and I can get it here in British Columbia.
It also does not absorb resin. With regard to wing layups does my formula sound like it will be adaquatefor a 48" span 10 poundEDF. What is the norm for spars and the material they should be made from. How much of an advantage is carbon cloth in the wing if "S" glass is 80% the strength of CF.

Thanks, Gary
Gary, I don't use polyester resin so I can't comment on the paint compatibility. The key to working with different colors is to know when to pull the tape. You have to pull it before the paint sets up. If you wait too long you will pull the paint with the making tape. Paint also tends to fisheye when spraying on wax. Light coats are neccessary at first to prevent this. Over reducing the paint, and using flat paints (still come out glossy) can help as well. There is a wax called Dolphin wax that doesn't cause fisheyes.

With molded wings the primary purpose of the skin is to provide torsional strength and cross-sectional shape stability. You could probably go with an even lighter layup. The bending loads are handled by the spar. Most spars in molded wings are constructed by using carbon fiber spar caps top and bottom that are separated by a balsa shear web. There a many techniques to create these spars.

Although carbon fiber is stronger in tension and compression than S-glass, it is almost 3 times stiffer. E-glass is able to handle the tension loads in our models. The weaknesses with glass is its stiffness. S-glass is also 75% of carbon in respect to compression strength. Carbon, since it is stiffer, resists buckling much better when under compression. Glass tends to buckled far before the fibers fails under direct compression. This reduces it's potential to effectively carry the load. For spars, carbon is typically the first choice since it is stronger in compression (common failure mode of spars) and much more resistent to buckling (also a common failure mode of spars). If you decide to start working with carbon you should really switch to using epoxy resin.
Old 02-13-2011, 11:49 AM
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19grb57
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Default RE: Laminate Thickness

Thanks for your reply,
I have had plenty of experience with fish eyes beirng in the autorefinish business! The mold release that I use is a 3 part system (Chem Release)that allows up to 50 pulls between reapplication and have found it is not to paint friendly. I may try some of the dolphin product you suggestand a 2 part urethane paint, it sound like it would be a great weight saving and allow numerous colors in the mold. For use in epoxy, what paint do find works well for you.
After reading your reply I certainly see the benifit of carbon over fiberglass cloth. When you make your wings do you use all carbon or just as a compliment to the glass cloth and what weight of carbon clothdo you use.
Thanks, Gary
Old 02-13-2011, 02:59 PM
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wyowindworks
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Default RE: Laminate Thickness

ORIGINAL: 19grb57

Thanks for your reply,
I have had plenty of experience with fish eyes beirng in the autorefinish business! The mold release that I use is a 3 part system (Chem Release)that allows up to 50 pulls between reapplication and have found it is not to paint friendly. I may try some of the dolphin product you suggestand a 2 part urethane paint, it sound like it would be a great weight saving and allow numerous colors in the mold. For use in epoxy, what paint do find works well for you.
After reading your reply I certainly see the benifit of carbon over fiberglass cloth. When you make your wings do you use all carbon or just as a compliment to the glass cloth and what weight of carbon clothdo you use.
Thanks, Gary
I use Frekote which is similar to your release. I've used rattle can paints, single component sprayable paints, and 2K paints. You just have to get used to spraying them on the release agent. Adding 50% extra reducer helps with 2K paints. You spray very light mist coats to start, let them set, and then try a little heavier coat. I often us a hot box in conjuction with my paint. I'll shot a very light mist coat and hot box it for 20 minutes at 125*F. Then I can move to heavier coats sooner. I've used PPG Deltron Concept (fuel safe), Deltron DC3000 Clear coat (naked carbon) for 2K. A really easy single component paint to shot is Dupli-color Paint Shop (not fuel safe).

The choice of skin material is really dependant on the application. On super high g (20 lbs at 90 g's) DS gliders I use all carbon on the skins to really stiffen it torsionally. I often use layers of 5.7 oz carbon on both sides of the sandwhich skin. On general racing planes I use glass skins with a balsa sandwich core. I always use unidirectional carbon for the spar caps. These I often make with raw carbon tow.



Old 02-16-2011, 10:12 AM
  #25  
MarkGrabowski
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Default RE: Laminate Thickness


ORIGINAL: 19grb57

I had posted a reply to the answers last week but apparently my post did not make it through.
Thanks to Magne and Wyowindworks for your response to my question and the ideas you have given me.

''What I have been doing in the past is to lay down the ''inside'' glass layer on a piece of polythene plastic, and wet it out there.
Then I put the polythene on top of the core material, with the glassed side down, and bag.
(Leave the polythene on the glass until the resin is cured, the polythene sheet can then be peeled off, as the epoxy does not stick to it.)''

Magne, I am not sure I follow what you are suggesting here. What are you using for a core material. If you could walk me through it I'm sure I can grab the idea.


Wyowindworks, I have some questions with regard to your techniques. First, what kind of paint do you use that is resin (polyester) friendly. I have about 30 years experience in the automotive refinsh industry so painting is second nature to me. I agree that gel is heavy and I could save alot of weight by painting, plus putting on graphics would be easier. My thought on the paint in the mold technique is when a second color was to be applied the tape covering the first color would remove it from the mold because of the wax on the mold surface?
Second, I have abondoned the use of Nida Core for use in the wings, it is a resin sponge! I have obtained some foam that is what I believe to be similar to Rohacell. It is resin resistant and seems to work quite well. It is a green foam that is quite lite. I found a piece that is 1/2 inch thick, I ran it through the band saw and got 3 pieces about 1/8 thick. I did a test layup as follows, 1 layer of 1.4 oz. and then 2 layers of 3.2 oz., then the foam and one layer of 3.2 on top, put it in the bag until cured. I can't believe how rigid and light this piece is. It also seems to be very ding resistant. I am going to try a wing layup using this method. When checking the price of Rohacell foam this green foam is less than 1/4 the price and I can get it here in British Columbia.
It also does not absorb resin. With regard to wing layups does my formula sound like it will be adaquate for a 48'' span 10 pound EDF . What is the norm for spars and the material they should be made from. How much of an advantage is carbon cloth in the wing if ''S'' glass is 80% the strength of CF.

Thanks, Gary
Gary, what's the name of this green foam you speak of?

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