REFLECTOR: Jeffco question

[John Tvedte]

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<mailto: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<mailto:grigore.rosu at gmail.com>
To: Velocity Aircraft Owners and Builders list<mailto: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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