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Building Tips and technical articles. => Building techniques => Topic started by: Ironbomb on March 17, 2006, 10:24:53 AM
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I have the mat applied to my wing LE, TE, and center section. I have at least three coats on it, brushed in. It is begining to look a bit glossy.
So, if I knock the fuzz down now, do I apply the silkspan at this time?
I did not cover the open bays with the carbon mat, was this a mistake?
This is new to me, I want to be familier with the process, see what works, then see what works for me.
Here it is so far.... :o
Greg
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Run it over the cap strips and all wood that the tissue will ouch.
This promotes two things; additional strength at all of the joints and acts as filler prior to installing the silkspan.
Only put the silkspan over the open bays,with the exception of double covering the center section.
Install with the overlaped ends slightly outside of the ends of the fillets-1/4 to 3/8 of an inch.
This prevents a stress riser being created when you sand your fillets.
Good luck
Busby
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You forgot to tell him that carbon veil/mat will not stay together in open areas. DOC Holliday
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I am applying the carbon mat to the rest of the exposed areas. Thanks for the pointer Marshall. Glad I didnt put it over the open bays.
When will I be able to apply the silkspan?
I will put three coats on the cap strips, then silkspan as normal?
What should the mat feel like before the silkspan?
Greg
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Has anyone ever tried covering the open bays with film like SLC or OzLite and then covering that with carbon mat? I and a number of others do that wil silkspan or modelspan, but I've often wondered if its worth trying with CF veil...
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What is the difference between woven and unidirectional carbon matt? Which is prefered for our models and at what weight?
Mike
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Mike, I dont know that. which is why I am doing this carbon mat in the first place. I can say that what I have covered is alot stiffer than the bare wood was. I had sanded some areas pretty thin, and the mat has gotten rid of some of the "soft feel" the leading edge and trailing edge had.
I dont know how this will turn out, but I will have done it once, and can go on from there.
try it, you'll like it ;)
Greg
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What is the difference between woven and unidirectional carbon matt? Which is prefered for our models and at what weight?
Mike
Hi Mike,
I will admit my ignorance on this one, too. I have been using CF *matt* since it was first mentioned for our planes. BUT, I just get it in the 2/10ths oz. weight from Randy Smith.
I also use the solid *strip* CF in .007 thickness for many reinforcement applications.
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Mat or veil is a random chopped strand array of fibres lightly held together with a binder. It has no primary grain direction and is not especially efficient (strength/weight) in any given direction compared to other forms of CF. Woven cloth is the typical under and over weave of any regular fabric. It offers much more efficient use of the fibres but still only half of the threads are working in any given direction. Unidirectional CF has almost 100% strength in one direction and almost none in the other. All the fibres run in one direction and only a thin thread or glue holds them all together. This stuff is only useful in specific critical locations in models.
Mat or veil is readily available in 0.2 and 0.5 oz weights. Woven CF cloth is only available in something like 3.2oz and above through the usual channels. You can get it lighter, but you need to be buying whole rolls from specialist suppliers it seems.
Use Mat/Veil wherever silkspan would usually touch balsa. Use cloth where you might have put a ply doubler or aluminium, use unidirectional for props, spars or stringers.
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Thaks, Adrian. I was thinking along those lines as to the differences, but I have only used the 2/10ths and 5/10ths oz. veil and some tow. I would guess that the tow is the unidirectional without a binder.
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Alittle secret that Rusty Brown told me, was, when you sand the veil after the first two coats of dope. Do not blow or wipe the dust off. He says two coats of dope, sand and then put on third coat. It fills the weave faster. DOC Holliday