Re: Fiberglassing Techniques


Jon Finley <finley@...>
 

Hi David,

I don't recall what RAF had to say about it, I would certainly think one of
those guys asked. It was at least a couple years ago. I will see if I can
lay my hands on them tonight and let you know.

I use the "bubble sprinkle" somewhat differently than maybe what you are
thinking. I use it to eliminate the glossy surface on the layup so that the
dry micro applies easier and has a surface to grip. So the only sanding that
is minimized/eliminated is that required to remove the gloss and create
something for the micro to grip, filling is still required. With this in
mind, I believe that the bubbles should be applied just before the epoxy
tackiness goes away and that only a very small quantity of bubbles be
applied. The goal is is to have the bubbles stick but not absorb epoxy. I
usually sprinkle the bubbles on, rub it in with my gloved hand (if this
helps understand when I do it - the epoxy is pretty set), and then brush off
the excess bubbles (the ones not sticking). I have never done it with a
large/structural layup (haven't had the opportunity). I'm of the opinion
that if the layup isn't dry and the builder waits until the right stage, it
is ok. I can imagine someone pouring a couple gallons of bubbles on a wet
layup, obviously this isn't going to work real well (probably result in an
extremely dry layup with a ton of sanding needed (before throwing away)).
The big problem with doing this is that layup inspection is very difficult
after applying the bubbles, you really need to inspect the layup before
applying the bubbles.

As long as we are talking about stuff that is "wild & crazy".... I also
use alcohol to thin my dry micro. I mix up the micro as dry as possible,
add a small amount of alcohol (I do it by eye, but it is probably a
tablespoon or so for an 8-12 oz cup of micro), and then add more bubbles.
The result is an extremely light micro that is easier to spread. Yea, there
was a big debate about this too (does the alcohol mess with the chemical
properties of the epoxy, etc...). All I know for sure is that all of the
airplanes that I know were finished this way and they still look fine.

Jon Finley
Q1 N54JF - 1835cc VW
Q2 N90MG - Subaru EA-81 DD Turbo
Apple Valley, Minnesota

-----Original Message-----
From: David J. Gall [mailto:David@...]
Sent: December 06, 2000 11:38 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Fiberglassing Techniques


Jon,

I must have missed this item. Did RAF ever endorse the hard-shell
procedure?
If not, did they ever renounce it? Either way, can you narrow down the
approximate year in either the CSA or RAF newsletter so I don't have to
dig
so deep?

On a related issue, I do recall the big debate over sprinkling micro on
the
surface of a still-wet layup to save on post-cure filling and sanding. Do
you have an opinion on that technique?

Thanks,


David J. Gall

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