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General control line discussion => Open Forum => Topic started by: Dennis Toth on October 07, 2012, 07:15:01 AM
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Guys,
I am in build mode on two ships and don't want to reinvent the wheel so I have searched the forum for information as to why carbon veil is used to cover wood structure. Basic conclusion is it adds stiffness and fills with less dope then say paper therefore it weights less. Others have used 0.5oz fiberglass cloth applied with epoxy that is scraped off (with a playing card) and rolled with toilet paper. This also adds stiffness and requires less fill than paper (paper having lots of pores to absorb dope). The fiberglass goes around curved surfaces much easier than carbon veil but with the epoxy is going to be heaver then the carbon veil. However, carbon veil is black and seem like it would requires a denser blocking coat then the fiberglass.
Question is has anyone used fiberglass applied with nitrate dope and wouldn't that work the same as the carbon veil as far as reducing the amount of filler? The fiberglass should use even less dope since it has more thread count than the carbon veil, it should also add stiffness that is very close to the carbon veil. Anyone try this?
Best, DennisT
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Dennis: The two (CF veil and fiberglass) actually differ quite a bit. I say this because
most of the CFV will be sanded back off. Whereas, the fiberglass will remain after sanding.
The CFV is really more of a grain filler than a strengthener. While it will add some strength
during the finishing process the real purpose is to fill the wood grain. After sanding it
will not remain on the model as a 'solid', rather it will look like something that is sanded
after applying primer. It will remain in some areas, while being almost completely removed
in others. If you have a depression, dent, or just a particularly difficult area to fill you
can actually use 2 or 3 coats of CFV, and just keep sanding to remove any unnecessary
material.
Steve
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Steve,
There is 0.3 fiberglass veil available would you use that the same as the carbon veil? Seems if you fill the waive either material will sand down and not absorb dope and still save weight.
Best, DennisT
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Steve,
There is 0.3 fiberglass veil available would you use that the same as the carbon veil? Seems if you fill the waive either material will sand down and not absorb dope and still save weight.
Best, DennisT
No Dennis, not so, the Glass cloth will "fuzz" very badly if you sand it like CF mat,or at least the stuff I have tried does, it is best to not sand into the cloth, the CF does not absorb the resin so it doesn't fuzz, and nothing like that happens when you sand it, other than it is silly to sand too much of it off.
Randy
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I used fiberglass veil on my last two models. I liked it better than carbon veil. I applied it with nitrate dope and treated it the same as carbon veil. Meaning I sanded it very aggressively. Two differences I found were the FG did not float in the air as bad when sanding. And it didnt seem to "flake" off as bad. It seemed to attach to the wood better.
I would advise when using this stuff, CF or FB veil, always tear it instead of cut it where there will be overlaps or seams. It is much easier to fade two edges together is the overlap is a tear vs a straight hard line.
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I used fiberglass veil on my last two models. I liked it better than carbon veil. I applied it with nitrate dope and treated it the same as carbon veil. Meaning I sanded it very aggressively. Two differences I found were the FG did not float in the air as bad when sanding. And it didnt seem to "flake" off as bad. It seemed to attach to the wood better.
I would advise when using this stuff, CF or FB veil, always tear it instead of cut it where there will be overlaps or seams. It is much easier to fade two edges together is the overlap is a tear vs a straight hard line.
Hi Doug, where did your FG come from? the stuff I have tried fuzzed when sanded too much
Randy
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Randy,
I want to say it came from CST composite. But they dont have it listed on their site at this time.
it was .03 I think.
Are you sure you are talking about fiberglass? The fuzzy stuff you are describing is very common when you sand into Polyspan. It doesnt cut like glass or carbon. The polyester just fuzzes up real bad. The only way to fix them is it to put some thin CA on the spot and sand until smooth. The CA soaks all the way through the polyester and hardens it so it can be sanded.
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I have always used silkspan and dope to cover solid surfaces and seemed to have good luck with it. Has CF veil taken over for silkspan now?
Mike
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I have always used silkspan and dope to cover solid surfaces and seemed to have good luck with it. Has CF veil taken over for silkspan now?
Mike
If you've got the money! ;D The CF veil fills the grain quicker, is a bit harder as a surface and costs a bunch more to do a fuselage, etc..
BIG Bear
RNMM/AMM
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I quit carbon veil because of expense and the problemsI had learningto use it. Can not back stroke if using dope I found out the hard way. It does sand easier and as Rusty Brown told me don't blow the dust off. Also don't rub it off if you don't want it permanently in your skin. I do most of my planes with lite weight fibre glas and dope. Goes down much easier than carbon. Also I put two to three coats of dope on before sanding lightly to get rid of the rough feel.
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Guys,
Thanks for the input. I did a little web search on carbon and fiberglass veil.
Here is the Carbon & Fiberglass Sales web site ( http://carbonsales.com/search.php?mode=search&page=1 )
The fiberglass veil is 0.3 oz per sq foot x 50" wide, $3.12 per yard (5 yard min), SKU: FL-151V50. They also have carbon veil 0.3oz per sq foot (8gsm) x 39"(99cm) wide, SKU: FL-171, $46.12 per yard (3 yard min).
They also have fiberglass and carbon cloth on the site.
Best, DennisT
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Wow, check here for carbon veil: A lot cheaper.
http://www.cstsales.com/carbon_tissue.html
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Wow, check here for carbon veil: A lot cheaper.
http://www.cstsales.com/carbon_tissue.html
That looks like the "bad" kind. Has anyone used this particular version? I would be very concerned about pinholes.
Brett
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I generally use both - depends on the application.. as a guide :
I use .75 oz Fiberglass with EZlam epoxy resin or West Systems over doped balsa surface ; for high structure area's such as the nose area - portions of around the wing, and anywhere that might be subject to cracking due to vibration.
I like to use combinations of .02 carbon and .03 oz Carbon Veil applied over all of that for a uniform finish - depending on where It is going.
( CST also do Kevlar tissue .. I'm yet to try it. )
I certainly have had no issue's with the "pin holes" and it fills perfectly with very little weight added. I dont know about "sanding it all away" I certainly have sanded through it many times but basically it sands so easily overlapping and block sanding it proves much easier with CF than Fiberglass.
However : using the .75 from CST and the matched epoxy you can sand that to a flawless finish also.
Once all of the bases are applied with your choice of either for strength I would apply 1 coat of dope sealer - the 1 entire coat of epoxy resin lightly coated and sanded. Then 2 more coats of dope - Then randy's Aero ZS - Sand sand sand.. 4:1 White Auto Primer - Paint base - clear - buff.
Simple.
Someone asked about the black CFV needing more of a blocking coat ? A good 4:1 PRIMER will only need 2 passes to cover in any case.
For things like flaps for example I like to use both .75 then .03 carbon veil to get them stiff.
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That looks like the "bad" kind. Has anyone used this particular version? I would be very concerned about pinholes.
Brett
It states that it is without the sizing.
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The best way to apply 0.5 oz glass to a fuselage or sheeted wing is with thinned K&B Epoxy clear w/ satin finish hardener. The cloth is brushed down on finish sanded raw wood. Just one thin coat is applied, just enough to lay the cloth down, not enough resin that a gloss surface appears. Let cure overnite, and sand. Apply a second coat of the resin ….. not glossy, just thin coat. The best thing about this method is the resin cures rock hard overnite and sands very easily, and the satin finish hardener fills somewhat. For me, applying resin and scraping it off, sometimes left a gummy surface that was difficult to sand.
I know K&B is gone, unless you have a stash of it. I would hope that KlassKote would work the same.
Carbon veil does add strength ….. a number of people who have applied veil to wing sheeted surfaces from wingtip to fuselage intersection (without carrying through the fuselage) have had the wing shear off right at the intersection during a hard pull. In other words, the outer wing now was much stiffer and the load at the carbon / non-carbon line was magnified greatly.