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Glass wings

Old 04-02-2004, 04:55 PM
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Default Glass wings

Hi,

Maybe some of you do this, but I know they put a sort of foam in the wings when they want to make them stronger, can you tell me what foam or sponge that is?

Or how do you lay up....it's for a Spitfire wing by the way.

Thanks
Tom
Old 04-02-2004, 09:41 PM
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Default RE: Glass wings

Tom, the material you might be referring to is coremat. Here's a link to the catalog that I use.

https://www.cstsales.com/Core_Materi...remat_core.htm

This 2mm thick material doesn't really add any additional weight, just additional stiffness, to your vacuum bagged skin laminates, allowing you to use fewer ribs.
Old 04-03-2004, 04:40 PM
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Default RE: Glass wings

Hi Mel,

Yep that was the material I was searching for.
Does some of you have experience with Honeycomb?

Why is Honeycomb better?

Tom
Old 04-03-2004, 11:50 PM
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Default RE: Glass wings

Watch out with honecomb. The cell shape can show through your finish if you get your surface hot (like when a plane sits out in the sun.)

Antony
Old 04-04-2004, 07:08 AM
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Default RE: Glass wings

I am having trouble keeping up here. I have read reference to wing skins, ribs and vacuum bagging. Are we vacuum bagging built up wings?

Ed S
Old 04-04-2004, 11:04 AM
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Default RE: Glass wings

ORIGINAL: Ed Smith
I am having trouble keeping up here.
It's stuff like this:


It has a good flow rate for expoy, so it will draw the expoy in to give you high strength with lower volume and weight. They make a few products like things.
Old 04-04-2004, 12:09 PM
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Default RE: Glass wings

I know what is meant by honeycomb material. I am still wondering about the wing construction refered to.

Ed S
Old 04-06-2004, 09:21 AM
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Default RE: Glass wings

Personally I wouldn't use Coremat, I find it absorbs too much resin, acts almost like a sponge. In fact boatbuilders use it exactly that way. They completely soak the Coremat in a bucket of resin, squeeze out the excess and then lay it up on the part they're working on as the final layer on top of CSM. It does add tremendous stiffness but the extra weight for what we want is not good. Corecell is much better, it sticks fine with epoxy (or polyester) but doesn't absorb so much resin being a closed cell type foam. It's much more rigid than Coremat. Coremat comes on a roll, Corecell is sold by the sheet and can be formed into molds using a hot air gun. Though they have similar sounding names, they're totally different products.

Another alternative that one of the specialist model plane manufacturers in the UK uses to good effect, Pete Tindall, is the thin foam lining that you can buy in any decorating shop for going under wallpaper and lining an uneven wall. Its a vinyl foam about 1 or 2mm thick. I've seen a couple of his moldings using this stuff and it adds a good amount of stiffness for very little weight penalty, and of course very cheap. Cuts with ordinary scissors and he just sandwiches it between two layers of cloth. I'll certainly try this method on my next molding. Works fine on epoxy moldings, not sure if it would work on polyester though.
Old 04-06-2004, 09:42 AM
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Default RE: Glass wings

The way I've found that works best with coremat, is to apply the resin to the glass cloth on a wetout table, then place it in the mold.

The 2mm coremat layer is placed dry into position on top of that, then the final, pre-wetted layer of cloth is added to the stack.

Then close the vac bag as normal.

This prevents any additional resin weight, and the resin still wicks into position in the small cell walls of the coremat.
Old 04-06-2004, 04:52 PM
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Default RE: Glass wings

Thanks for the reactions!!!!

Do you also have pictures of a wing lay-up?

Thanks
Tom
Old 04-06-2004, 05:54 PM
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Default RE: Glass wings

Here are some test laminations that were done, using West System epoxy and equal weight sections of Rohacell foam and coremat, both at a 2mm thickness.

4 + 4 indicates 4.5 oz cloth on either side of the core material
4 + 9 indicates 4.5 oz, then a 9.0 oz cloth
9 + 4 indicates the inverse of that layup
9 + 9 indicates 9.0 oz, and another 9.0 oz cloth

Notice the weights, shown in thousandths of a pound, are basically identical, for the same laminates on each core type.

Granted, the Rohacell foam is stronger, but is also four times as expensive, and more difficult to comform to tight radii, unless it is pre-formed by heating. It also cracks easily, and the edges should be beveled, as was done in these samples. If the samples appear curved, it's because they were done in an existing upper wing-skin mold.
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Old 04-08-2004, 02:06 PM
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Default RE: Glass wings

Hi Mel,
Very nice work with the Coremat!!! A few weeks ago I posted a request concerning Coremat on the yahoo moldmaking group. I copy that below for you. As you can see I have found exactly as you...that the Coremat needs to be sandwiched DRY. Although I've just done some small flat panels and a few small parts with Coremat, I want to make light and STIFF F3A fuselages with Coremat in a sandwich core. I have tried Rohacell 51 (3.2 pcf) but it cracked very easily even in moderate curves. One good responce I got was to use it (the Rohacell) only in key areas...kind of make a cut and splice skeleton as the core. I love the way the Coremat can conform to even the tightest curves and is a dream to work with under vacuum, but controlling the amount of resin saturation is the real problem....If you can share more on your experiences with Coremat as a sandwich then please do! If the fuses work out well then I want to make all composite wings and stabs using Coremat in the same way as done for the fuslages...something you may have experience with (?). Read my previous post copied below and let me know what you think,

Thanks,
Erik

__________________________________________________ _______________________
from groups.yahoo.com/moldmaking

Hi All,
A while back there were a few questions regarding the use of Lantor
Coremat as a core material in a composite sandwich. There were not
too many responses, so I got the impression that not many were using
it on parts (however, a few were using it to build up thickness and
stiffness to their master molds). I am interested in it because I
want to make very stiff F3A fuselages with it...stiff enough to
eliminate any formers. I have made a few fuselages with balsa as a
core and I was not happy with either the weight or the stiffness.
Note that I was not using end-grain balsa, but rather cutting and
splicing 3/32" thick balsa (4-6 lb/cu.ft. density) in the mold
between E-glass layers (two layers of 3 oz. cloth for each side) and
vacuum bagging.
Anyway, I have been playing with Coremat and thought I would share
a bit of info and also solicit a bit of advise. I have been making
some carbon-Coremat-carbon flat panels, mainly to be used as light-
weight and stiff servo trays or formers. The carbon is 5.8 oz 2x2
twill weave. The size of the panels are 12" x 24" and so far the
lightest one I have been able to make is right at 5 oz. You don't
want to know the weight of the heaviest....let's just say that if
you're not careful the Coremat is a nice sponge!
The way I make these is to use two 12" x 24" pieces of 3/8 thick
ultra-smooth Plexiglas. These are waxed and polished. I then roll on
a thin film of epoxy on the plexiglass (for these pieces I'm using
West Sys 105/206, but will also use MGS 285) then lay on one layer of
the 5.8 oz. carbon. I roll and saturate the carbon making sure that
the carbon is uniformally wet and pick up as much excess epoxy as
possible. At this point, I have two separate 12" x 24" wet carbon
sheets on the plexiglas plates. Now I place a piece of DRY Coremat
(2mm thick) between the two plates in contact with the wet carbon and
place the whole mess in the bag and vacuum. Another thing that I do
is to surround the edge of the piece with strips of breather cloth to
soak up any epoxy under vacuum. I should also note that I'm in the
Mile High City of Denver, Colorado so I can only pull approx. 20 in.
Hg. true vacuum.
After approx 36 hours in home-made oven at 120 deg F, I separate the
panel from the plexiglass...flat, light and STIFF! The heavier ones
were the result of trying to wet out the Coremat with epoxy...in the
end, far too much epoxy as evidenced by the completely saturated
breater strips.
Okay, now my problem.....I'd like to make a fuse using a similar
technique, but have a problem with laying up the final cloth layer.
For the fuse, I thought of a mix of Carbon and Glass...putting some
carbon in the key areas. I can lay-up a couple of layers of glass,
then lay in the Coremat (which is very flexible), but how to get the
final layer on without saturating the Coremat with epoxy is the
problem???
I imagine that you guys that make honeycomb sandwich parts have a
similar problem with the final layer .... unless it's a pre-preg.
Does anybody have any experience with using Coremat in this way or
any suggestions about how to approach this?
Old 04-08-2004, 10:33 PM
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Default RE: Glass wings

I frequently use the 2mil coremat from Baltek. If you soak too much resin in the coremat then you're pretty much doing it the incorrect way. Not a big problem with epoxy, but the styrene content in styrenated resins could potentially eat away the coremat material rendering it useless in term of effectiveness. Coremat, done correctly, adds very little weight but at the same time increase stiffness and bulk.

Evan
Old 04-09-2004, 07:59 AM
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Default RE: Glass wings

So how is it done? I'm looking to do the very same thing, only with a large jet fuse, so weight is a big issue to me also.

Is it just careful epoxy wetting (brush? roller? sprayer?) once the coremat is pressed into placed?

Would solve my last issue before production....
Old 04-09-2004, 08:31 AM
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Default RE: Glass wings

As stated in my post #9, your precut sections of glass should be infused with resin on a wet-out table, then placed into final position in the mold.

A roller works best for even wet-out.
Old 04-09-2004, 08:40 AM
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Default RE: Glass wings

Yeah...that's what I was afraid of...

What's a good set-up for a wet-out table?
Old 04-09-2004, 08:54 AM
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Default RE: Glass wings

I have a 2' x 4' white melamine panel that I wipe off after each use, or you can use a sheet of cardboard and discard after using.
Old 04-09-2004, 09:12 AM
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Default RE: Glass wings

Sounds simple enough-I've always disliked having to handle wet cloth-guess I'll have to get over the hangup if I want to build this way.

Any issues with delamination of layers from coremat? I'm guessing there must be some wicking of resin between the inner and outer layers, causing a tie-bond. My application would be:

3/4, 6.7, Coremat, 6.7; bias weave carbon in select areas.
Old 04-09-2004, 09:27 AM
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Default RE: Glass wings

I would recommend doing a smaller test lamination, that would help you develop a routine that can be applied to larger parts.

The resin content of the glass on either side of the core, wicks into position easily on the 2mm coremat.

Coremat is sensitive to vacuum pressure, since it compresses. You might try lower pressures, around 15 to 20 inches, since it helps the mat retain it's height. A full 25 inches of pressure can collapse the 2mm mat to half it's original height, and once demolded, if it's too green, the internal mat's foam pressure will distort the molded surface.
Old 04-09-2004, 10:23 AM
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Default RE: Glass wings

Good tip Mel, hadn't thought about the vacuum pressure and coremat.

Thanks! I appreciate your help with this fledgling molder. I've done a bit of molding (paint in the mold, standard layups in vacuum, etc.), now I want to get into saving weight on this plane.

Chuck

p.s. good source on coremat (cheap)?
Old 04-09-2004, 10:47 AM
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Default RE: Glass wings

My source so far, is CST. Here's the link:
https://www.cstsales.com/Core_Materi...remat_core.htm
Old 04-09-2004, 11:03 AM
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Default RE: Glass wings

Thanks, I'm set up with them already, just was wondering if there was cheaper out there, not that it's particularly expensive to begin with; I just like saving money if possible. I'll get me about 10 yards to play with.

Thanks again for your help. I'll post some pic's if I EVER get to play in the shop...darn "critters" take up so much time-I guess that's why they're made so cute; to overlook there faults.
Old 04-09-2004, 11:22 AM
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Default RE: Glass wings

Chuck,

I agree with Mel...I get my Coremat from CST. I have purchased what was called "Coremat" from two other sources that was less expensive, but BEWARE, what I recieved was not Lantor Coremat XM, it was something that looked like Coremat from a distance, but if you inpected it closely it was VERY different. If you look closely at the real Coremat you will see a beautiful hexagonal stucture of what I would call micro bubbles with a thin support layer separating them acting as a shear web. The imatation Coremat was more like a fiberous woven mesh with similar dimpled holes spaced every .5 inch or so to make it look like the real thing. The microbubbles and their support layers are the key! As Mel states, I think want you want is to have just enough resin to be able to "wick" throught these shear webs and close the structure.....too much resin and you will impregnate the whole mess, microbubbles and all. The two links below describe Lantor Coremat and I found them very useful. The second one in particular, is an excellent resourse for composite molding and layup techniques. It is a German company and the "handbuch" is written in German and English (leave off the kapitel_09.pdf to access the whole book). Interestingly, after you see how these describe how to use Coremat you will see they are doing just what Mel and I are saying not to do....namely, saturate the whole Coremat layer. I believe that for most of the applications of Coremat where one wants high stiffness in their part, weight is probably not of concern...i.e. boat hulls or car hoods etc. However, as you are well aware, for your jet fuselages and my pattern fuselages just a few extra ounces can defeat the whole purpose and render the whole part useless. Check out the links below. I'm not giving up on Coremat yet, I do think that it can be used to make stiff and light parts, but it will take some experimenting to discover the right techniques. Mel has some great experience and in the next few months I'm hoping to post some picutes and share my experience with the fuselages.
With regard to the amount of vacuum. I have also tried lower vacuums (around 8-10 "Hg....similar to vacuum bagging balsa to white foam) and that works great. As Mel states, too much vacuum and you will crush to Coremat. The compression strength is quite small...nothing like end-grain balsa or Rohacell where you can pull 20-25 "Hg.
Please keep us posted on your progress and I will do the same.

Cheers,
Erik

Links about Coremat:

http://www.lantor.nl/composites/fr_comp/frame_comp.html

http://download.r-g.de/handbuch/kapitel_09.pdf
Old 04-09-2004, 11:29 AM
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Default RE: Glass wings

Thanks for the reinforcement, guys.

I've been working on coremat ribs, to eliminate wood from the composite process, too.
Old 04-09-2004, 12:30 PM
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Default RE: Glass wings

Which coremat are you using?

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