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Re: REFLECTOR: Bulkhead Installation






>Date: Wed, 13 Jan 1999 20:52:19 -0500
>From: Dave Black <asterisk@erols.com>
>To: reflector@awpi.com, Benjamin David Cowan <bdcowan@telepath.com>
>Subject: Re: REFLECTOR: Bulkhead Installation
>Reply-To: reflector@awpi.com, Dave Black <asterisk@erols.com>
>
>David,
>
>> Is that really that big of a deal?  
>
>I doubt it. The fuselage flange is just where the top and bottom halves 
happen
>to come together.
>
>> Also, when I layed it up (MG BH), about 2 hrs
>> later I noticed some linear dry spots in the top layer in the bend 
part of
>> the BH. Should I trash the hole thing and start over? Or is that not 
a 
>> major problem.. Otherwise the layup is extra wet if anything. I 
wanted to be 
>> sure nothing unravelled. 
>
>Dry spots in your layups are definitely NOT good. But neither are super 
wet
>spots. The method we adopted in all our fiberglass work was to wet out 
the
>fiberglass on a piece of construction plastic, then transfer it to the 
place
>where it's needed. 
>
>If you do as we did and wet out the glass at the workbench, you have 
MUCH
>better control of how much resin is in the lay-up, and can squeegee it 
until
>it is completely uniform, and maybe a wee bit toward the dry side. 
>
>Before you lay it in place on the airplane, you need to "prewet" the 
area of
>the lay-up with a thin layer of resin. We use a cheap 1" or 2" paint 
brush for
>this (the brush is trashed afterward, not cleaned). Next you put the 
prewet
>fiberglass in place and dabble it into position with that same 
paintbrush. Lay
>Peel Ply over top of the whole package, and dabble that into place. 
>
>You do not want pools of resin in your lay-up. It adds weight and 
reduces
>strength. Nor do you want your layups too dry. That saves weight, but 
also
>reduces strength. The trick is to get the fiberglass strands as near to 
each
>other as possible, and have just enough resin to fill the space between 
the
>fibers. 
>
>Practice makes perfect.
>
>Dave Black
>SW RG TopDoor
>
I used the exact method above with 1 additional point.  If you are going 
to do any vertical layups, then, allow the layup to partially cure (this 
is a given for me considering the speed, or lack thereof, that I work 
at) then heat with a heat gun prior to transferring to the pre-wetted 
area.  This prevents the resin from draining out of the glass and 
leaving voids.

Larry Epstein 
173 FGE 

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