REFLECTOR: Coarse/Fine BID

[Richard Riley]

I'm guessing fine bid is 7781, and coarse is 7725.  That's just a 
guess, I haven't seen them.

If that's true, they are equal in strength.  7725 is easier to work 
since air comes out through it easier.  7781 is more often used as a prepreg.


At 09:58 AM 7/22/2006, you wrote:

>keithhallsten at quiknet.com wrote:
>
> >I think the use of peel ply make far more difference in whether or 
> not you have a leak than which weave of glass.  The weight of fine 
> bid and course bid is almost identical, so I wouldn't worry too 
> much about substituting one for the other.  However, it's easier to 
> get air bubbles out from under course bid than fine bid, so there 
> is some difference.  When I asked the factory guys about this issue 
> they said that they are not using fine bid anymore, and course bid 
> could be substituted.
> >
>Thanks.  That's what I thought after Scott's response.  I like to use
>peel ply, so I am covered there.
>
> >For fuel sealing surfaces, you definitely don't want to get 
> carried away with weight reduction - go ahead and make sure you 
> have sufficient epoxy to fill any voids, then use peel ply to give 
> you a finished surface and pick up any excess.
> >
> >Keith Hallsten, XLFG
> >
> >
> ><Jorge Bujinda wrote:>
> >The manual calls for fine BID to reinforce the vertical and horizontal
> >seams of bulkheads and baffles (Fig. 9-16. Fuel baffle and bulkhead
> >location.).  Although up until now I have used coarse BID almost
> >exclusively, I ran out of fine BID glassing the Divinicel for the fuel
> >tanks and I am about to start glassing the baffles and bulkheads.
> >1.  Can coarse and fine BID be used interchangeably?
> >2.  Can I use coarse BID to reinforce the horizontal and vertical seams
> >of bulkheads and baffles without increasing the risk of leaks?  Seems to
> >me like the fine BID would seal better due to a tighter weave.  Am I
> >wrong?
> >4.  Is there a difference in weight between the two?
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