Flex all question

[carl30]

I bought Dave Brown Flexall to add to Sig Lite Dope. It says to add 1 or 2 Tbs per in thinned pint of dope.  Would the full 2 tbs be ok to add? Thank you

[Bill Little]

Hi Carl,

While I have never used that much in a thinned Pint, if the directions say so, it is probably all right.

Thanks!
BIG Bear
RNMM/AMM

[carl30]

Ty, I am using Sig Lite Coat and was wondering if I can still add the 2 Tbs.

[Dan McEntee]

    If everything is shrunk up nicely already, I don't think it would hurt and help the finish age better. I think that Flex-All is the same as medicinal castor oil and does the same job as what you used to read in the instructions of older free flights kits to plasticize the dope and control the shrinking. I gave it a simple "taste test" and they sure tasted the same! I only added a couple of cap fulls to the mix the last time I needed to spray something. Two table spoons sounds like an awful lot but I haven't seen the label on a bottle in a long time.
  Type at you later,
  Dan McEntee

[billbyles]

I bought Dave Brown Flexall to add to Sig Lite Dope. It says to add 1 or 2 Tbs per in thinned pint of dope.  Would the full 2 tbs be ok to add? Thank you

As I type this I have a new bottle of Dave Brown's "Flex-All" plasticizer sitting on the desk in front of me.  On the label the directions clearly state that for butyrate dope (such as Sig Light-Coat) "one or two tablespoons per UNthinned pint.  If you use that much for a thinned pint of Light-Coat dope you will have intercoat adhesion problems.

I use non-tautening butyrate clear (Sig Light-Coat) from the bare balsa all the way through the final coats of clear, except for the first three coats on open bay surfaces only where I use tautening type butyrate (Sig Supercoat) or Randolph tautening type.  Up through the color coats I use only one tablespoon of Flex-All per pint of unthinned non-tautening (Light-Coat) butyrate.  For the final topcoats of clear I use Sig Light-Coat with two tablespoons of Flex-All per UNthinned pint of butyrate.

[carl30]

I have used sig lite with Silkspan with good results. I am building a small rubber plane with Esaki tissue and don't want it to warp so that is why I want to try 2 tbs of Flexall

[Dan McEntee]

   On a small rubber model, you are going to be using a lot less dope, so the ratio of Flex-All could remain the same, especially if you already have some left over treated thinned dope.  The old rubber model instructions and old books on the subject of doping called for castor oil, and usually 3 or 4 drops per ounce of thinned dope. By my best guess, the table spoon to un-thinned dope sounds about right.
 Let us know how it turns out.
  Have fun!
  Dan McEntee

[carl30]

Thanks for the replies and info, I have never used Flex-all. One more question, what is the down side to using the full 2 tbs vs 1 tbs of a Flex all in Sig Lite?

[billbyles]

Thanks for the replies and info, I have never used Flex-all. One more question, what is the down side to using the full 2 tbs vs 1 tbs of a Flex all in Sig Lite?

I have never encountered a "downside" to using the recommended amount of Flex-All in Sig Light-Coat butyrate dope, with only one exception: if you use Flex-All in Sig Light-Coat butyrate for the first coats on the bare silkspan over the open bays you will likely have silkspan that is not as taut as you want.

All dope shrinks (or tautens); tautening type shrinks about 10 to 12% whereas "non-tautening" butyrate shrinks only about 4 to 5%.  However, over time the plasticizer will leach out of all types of dope and the dope will slowly shrink more and more.  This leaching out process likely won't be a factor for our models since they are normally not stored outside in sunlight.  For full-scale fabric-covered airplanes stored outside this process of the plasticizer leaching out can take up to 15 years before you will see evidence of it in the form of the dope film cracking where the fabric transitions from open bay to hard underlying surfaces such as ribs, trailing edges, longerons, leading edges, etc.

[Dan McEntee]

Thanks for the replies and info, I have never used Flex-all. One more question, what is the down side to using the full 2 tbs vs 1 tbs of a Flex all in Sig Lite?

   The only down side I can think of is using up your bottle of Flex-All faster than you really need to, and the next time you REALLY need some for a rush job, you bottle will be empty of your shelf bare!
   Type at you later,
   Dan McEntee

[carl30]

So if I shrink the Esaki tissue with water and the open bays are tight with no wrinkles. I brush on Sig Lite with Flexall, will the tissue tighten up back to where it was or will it stay loose?

[Dan McEntee]

  I think it will be fine. The good thing is,if it doesn't, you can brush on a coat of un-treated dope to help out. Even some GENTLE heat with a hair dryer or mono-kote gun will help with light wrinkles. But properly applied tissue, and satisfactorily water or alcohol shrunk, it will sag a bit while the dope is wet, but will firm up when the dope dries. Another approach to it is, pre-shrinking your tissue on a wooden frame before you cover the model. This helps on real flimsy, light weight air frames.
   Type at you later,
   Dan McEntee

[Brett Buck]

   The only down side I can think of is using up your bottle of Flex-All faster than you really need to, and the next time you REALLY need some for a rush job, you bottle will be empty of your shelf bare!
   Type at you later,
   Dan McEntee

  Too much will definitely hurt the adhesion of following coats, as noted above.

    Brett

[RandySmith]

I have used the flex all  for decades now, with dope and laquer, I only use it in the last clear coats and so far it has been excellent. I use 2 teaspoons full in an unthinned pint
. Can you still buy DB Flex All ?  I have not seen it in a while.
Randy