I just started vacuum-bagging my CF and I wonder if the breather should only slightly touch the piece or should the breather be all over it?

The piece of breather fabric that you are going to use mast be larger than the part itself. So it must be al over it and beyond it a little bit. Don’t forget to cover the part whit peal ply (or equivalent) before you lay the breather otherwise it will stick badly to the part.

Thanks.

Please tell as what you are trying to built. It will be easier to advice you.

But yeah, if you don’t place de breather covering completely the part, the excess of matrix and air won’t have any opportunity to escape anywhere. The breather serves tow major purposes, to guarantee that the air and vapours from the matrix can bee vacuum up and to absorb the excess of matrix.

The peal ply just make it possible to place the breather on top of the part without sticking to it, as the same time that it permits the air, vapours and excess of matrix to flow from the part to the breather.  

You don’t really need two layers of peal ply, although some time you should use more than one layer of breather (if you think that the CF is just to soaked whit matrix).

But like I stated above, if you tell as what your building, it will be easier to advice you.

I'm building a bikeframe (to use in triathlon). 

Ok, you should wrap the breather all around you’re part just like you do with the peal ply.

Also, there’s at least one more topic talking about bike frames in this forum, unfortunately I don’t remember where I read it, but it even points you some YouTube videos about composite bike frames building.  

Ok, so I will cover the whole part then. 

Hi,

If you wrap your breather all over your part (well, on your peelply, actually), it will give an even amount of pressure all over your part. I dont know anyone complaining for using breather could lead to the fabric not being completely applied on the mould.

Hope it helped.

 



 


    A $1000 electronic device will always protect a 10 cents fuse

The reason that I wonder if one should use the breather on the whole part is that I found the guy you, Joe linked in another thread about how to build a bike-frame. That guy in video 3 doesn't wrap the breather around it, but just put the breather next to the plug.  It's projectjunkie on youtube