REFLECTOR: Jeffco question

Fri Feb 8 22:09:22 CST 2008

John,

Here is what I wrote down while talking to Scott; he said that this is how
he does it, not necessarily the only way to do it:

(1) mix the following
- 3 cups of Jeffco 9700
- 1.5 cups of the hardener that came with the Jeffco
- 4-5 cups of cabosil
- 4-5 cups of flox

I found these proportions too huge for me, so I was planning on reducing
everything by 33%.

(2) throw the entire mix in the middle of the tank; he said that it is not a
good idea to keep it in the mixing container and take bits from there.

(3) using a squeege, spread the mixture all over the place as quickly as you
can

(4) using a brush, take care of corners, etc
(5) between 8 to 24 hours after the first coat, give a second coat following
the same procedure and proportions

(6) between 8 and 24 hours after the second coat, bond the top strake using
the same Jeffco mixture on the baffles and the tank-inner part of the
bulkhead flanges, and using, as you said, Aeropoxy with cabo and flox on the
spar and the aft part of the bulkhead flange

I do not remember anything about having to sand the Jeffco or not; I'm
assuming that if you do it within the time frame 8-24h you may get chemical
bonding, which may be even better than sanding?  Also, I do not remember
anything about the top strake.

Grigore

On Feb 8, 2008 5:09 PM, John Tvedte <johnt at comp-sol.com> wrote:

>  Grigore,
>
> I would be surprised if Scott Swing said to mix flox in while 'painting'
> the strakes.  Cabo is ok to add, but not much - Jeffco does tend to be
> slightly thin and runny - so the cabo will help when painting vertical
> surfaces.  Well - it's more like it gets runny when it starts to cure - so
> the cabo helps...
>
> Flox and cabo are used to make a frosting like mixture when sealing the
> top strake to the baffles and bulkheads.  Use Aeropoxy cabo and flox for the
> spar portion, and you can also do a small area of the leading edge of the
> strake with this if you don't use Jeffco for the entire area - use the
> Jeffco on the leading edge where there will be exposure to fuel.
>
> You can also use milled fiber to replace the flox - if you want a smoother
> texture - I find it easier to work with - and although heavier - I think it
> is a fair trade off when used on the strakes.  Flox tends to be lumpy...
>
> John
>  ------------------------------
> *From:* reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] On Behalf
> Of Grigore Rosu [grigore.rosu at gmail.com]
> *Sent:* Friday, February 08, 2008 4:40 PM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: Jeffco question
>
>    Thanks Ronnie.
>
> Hm, this is in contrast with what Scott Swing told me last week; I
> guess there are different ways to do it.  It was him who recommended me the
> composition above and he said that I should use a squeege, lay two coats of
> Jeffco, and use the same paste to bond the top strake.  There were many
> things he told me and many things I forgot to ask; in particular, I am not
> sure whether it is best for the top strake to cure all together in place as
> it's being bonded, or to do what you suggested.
> Grigore
> On Feb 8, 2008 4:25 PM, Ron Brown <romott at roadrunner.com> wrote:
>
> >  Grigore,
> >
> > I don't think you need the flox and cabosil for coating the fuel tanks,
> > bulkheads and baffles.
> >
> > Just mix and apply the Jeffco and watch for bubbles to form - prick them
> > with a tooth pick or use a small paint brush.  The key is to stay with the
> > Jeffco until it sets and no more air bubbles appear.  I didn't watch for the
> > bubbles, let it set and had a bunch - so I had to sand it and apply a second
> > coat - which only added more weight.  Not good.
> >
> > Go ahead and paint the underside of the upper strakes too.  Just roughen
> > the Jeffco where the stakes meet the bulk heads and baffles before
> > installing the strakes.
> >
> > Some folks have used the Jeffco to install the strake tops - then you
> > would use flox and cabosil to make more of a putty that will stand up and
> > fill the gaps between the bulkheads/baffles and the upper strake.
> >
> > Ronnie
> >
> >   ----- Original Message -----
> > *From:* Grigore Rosu <grigore.rosu at gmail.com>
> > *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> > *Sent:* Friday, February 08, 2008 4:06 PM
> > *Subject:* REFLECTOR: Jeffco question
> >
> > I understand that Jeffco cures much faster than EZ-84, so it is not a
> > good idea to prepare too much at once when sealing the tanks.  Also, it
> > appears that it is a good idea to mix it with flox and cabosil.  I'm
> > thinking of mixing the following at one time each time:
> >
> > - 2 cups of Jeffco
> > - 1 cup of hardener
> > - 3 cups flox
> > - 3 cups cabosil
> >
> > Also, I'd like to give a first coat, then 8-12  hours later give a
> > second coat, then 8-12 hours later seal.
> >
> >  Does this sound right?
> >
> > One thing I'm not sure about is how to deal with the top strake.  Should
> > I coat it at the same time I coat the rest of the tank, or I should just
> > coat it before sealing?  I'm worried that if I coat it following the same
> > timeframe as for the rest of the fuel tank, then I may end up with a layer
> > of sealant on the top strake that is thicker than 1/8'' - 3/16'', which is
> > the gap I currently have between the bulkhead flanges and the top strake.
> >
> > Thank you,
> >
> > Grigore
> >
> > ------------------------------
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