Using Vacuum for covering parts in CF.


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Interloper393
Interloper393
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Buddy your over complicating things here..
Key the part with 120 grit 
Tack spray and stick the cloth to the part,  if you push excess cloth into the whole fisn't you with be able to wrap the inside too.
Apply your first resin coat and wait for it to cure.
TrI'm excess off and apply resin coats as normal
Hanaldo
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Aha... I hadn't realised you were trying to skin the inside of that lip as well. That is always going to be a struggle.

Do you actually NEED to cover the inside of the lip? It doesn't appear to be visible once the leather boot is fitted? In which case, I would simply paint it black and trim the carbon back flush with the top of the lip.

If vacuum works for you and you can do it without getting creases in the top then stick with it, there's no reason not to. What I meant with bridging is that vacuum isn't very good at getting into the inside radii, so it tends to just fill it with resin instead. If you aren't getting that problem, then vacuum is a solution! 
fibernoob
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Here is a pic of the part 

Note the inner part still shows the peelply texture since it was not sanded.

The outer part has already been wetsanded and ready for extra coats of resin.


fibernoob
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Hanaldo - 1/19/2018 12:32:14 AM
That part shouldn't be difficult to do without vacuum, it sort of sounds like you aren't leaving the initial cost of resin long enough before applying the carbon/further coats of resin.

But, there's no harm in using vacuum either, so long as you don't pinch the fabric or get lots of bridging. 

Yes, bridging is the issue im trying to get around when using the vac. 

I will try again letting the resin come to a perfect tach stage to apply the fabric....   

Thanks for the help

fibernoob
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MarkMK - 1/19/2018 6:01:22 AM
It might also help to attach a temporary flange to the inner edge of the part to give the fabric some additional surface to grip to. Making this flange follow the angle of the lip would likely make the fabric less likely to want to lift, especially if you're currently trying to fold it around the inner circle

I wouldn't be averse to the idea of using separate pieces of fabric for the lower sides of the parts also. This will leave an overlap to deal with in your finishing, but would allow you to put some small cuts in the corners of your main piece of fabric which will help maintain the weave alignment on top and, perhaps, ensure there's less 'pull' on the fabric when trying to get the area around the centre hole to conform. If the fabric's cut and placed neatly, I'm sure that a great finish is possible

Thanks Mark. 

Sometimes its just those small things that can mess everything up.

 I have considered using some fabric in the inner hole as you have mentioned.    

Thanks for the feedback. 

MarkMK
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It might also help to attach a temporary flange to the inner edge of the part to give the fabric some additional surface to grip to. Making this flange follow the angle of the lip would likely make the fabric less likely to want to lift, especially if you're currently trying to fold it around the inner circle

I wouldn't be averse to the idea of using separate pieces of fabric for the lower sides of the parts also. This will leave an overlap to deal with in your finishing, but would allow you to put some small cuts in the corners of your main piece of fabric which will help maintain the weave alignment on top and, perhaps, ensure there's less 'pull' on the fabric when trying to get the area around the centre hole to conform. If the fabric's cut and placed neatly, I'm sure that a great finish is possible
Hanaldo
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That part shouldn't be difficult to do without vacuum, it sort of sounds like you aren't leaving the initial cost of resin long enough before applying the carbon/further coats of resin.

But, there's no harm in using vacuum either, so long as you don't pinch the fabric or get lots of bridging. 
fibernoob
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scottracing - 1/16/2018 9:34:11 PM
why are you using peel ply? you dont need to and also have you tried using spray tack to locate the dry fibre in position?

A couple of photos  would be good too , but when you are trying to do a wet lay and vac bag you dont want to pull full vac as you will pull too much resin out.

I am using peel ply  because if i use the vacuum bag directly it will stick to the resin ... Ive used spray tack but with the part im doing ... its loosens up the fabric especially on the plastic rib just arrounf the center hole. (location of the gear boot)

The resin stays under the peel ply... the vac is mainly to tighten the fabric to the parts contours.

This is the part i am trying to skin....



And this is the desired end result.





Edited 7 Years Ago by fibernoob
fibernoob
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Interloper393 - 1/18/2018 10:13:00 PM
The peel ply will leave a texture finish which iv found helps grip next coat,  I still sand just to be sure Smile also means bag can be reused.
I tack spray the cloth to the piece,  wet the fabric ,  apply peel ply then vac bag.
Iv started to use poly resin as it' much quicker wit the extra work with the vac bagging plus parts and cured in 2mins XD

Yes, ... If more resin will be used I often sand it down with thin sand paper because if the texture is left , small dots can be seen from the layers above.

If more carbon is to be used, i think the texture is great for the next layers to grip.

I am still using epoxy and experimenting ...but it helps a lot with tight curves and nasty angles that the CF does not want to contour.


Interloper393
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The peel ply will leave a texture finish which iv found helps grip next coat,  I still sand just to be sure Smile also means bag can be reused.
I tack spray the cloth to the piece,  wet the fabric ,  apply peel ply then vac bag.
Iv started to use poly resin as it' much quicker wit the extra work with the vac bagging plus parts and cured in 2mins XD
GO

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