old paper, no shrink?

[twospruces]

Hi,

I'm putting together a very old guillows 500 series FW190 - it has red plastic parts and wood wheels - and the tissue doesn't seem to want to shrink very much. Does that make sense? Would old paper essentially shrink a bit in the box over time?

When I wet the paper, it certainly loosens up. I'm papering using the thinned glue technique mostly, and so the paper is dry going on. To shrink, I am simply spraying water on the paper and letting it air dry (pinned to keep things flat).

Is there any way to exaggerate the shrinkage? I've read that some use alcohol? I would like to find a way to make the paper shrink up properly.

thanks for any suggestions.

[Mitch]

Sorry, you got me stumped on this one. I build old kits from time to time. Usually I do not use the paper as I see it is old and crinkly. On my last 'old' build I used the paper and things worked fine. I actually used old kit paper for top and new paper on bottom of wings. I did this because the paper was of a color that I do not have.

The only reason to use alcohol is when you have printed paper (ie. German Lozenge) so the ink does not run. It serves the same purpose for shrinkage.

Usually the paper only needs a mist of water. I would say soak it this time and see what happens. Otherwise you may need to strip it off and get new paper.

Sorry, Mitch

Here is the SE5 I built with kit paper. The kit had the pilot so I am guessing it is from the 70's or 80's. I have kits that are older and I throw the paper and rubber bands away, and with those kits the decals are useless also.

[Brenda]

With 40+ year old paper that has been exposed to humid then dry then humid you have problems. Even if it's only a few percent over the course of 40 years it takes a toll. If the paper has already been attached with glue but not soaked in it you can use real dope. You need to thin it out a bit more than normal however, then allow it to cure over night. I've used paper from Comet kits that are 50+ years old this way and it worked fine. The only reason I used the old paper was to have a 100% Comet plane. Might be best to get off old paper and use new.

[twospruces]

Hi, not sure I follow completely with how to use Dope.

So, the paper is shrunk, but not snug in many places It is still "bare paper" meaning no glue or dope has been applied to the surface.
Does dope (mixed with thinner) induce shrink as well?

I would have thought that the shrink is now "done" and applying dope just secures the shrink.

thanks,
Steve

[Brenda]

Buterite or however it is spelled makes paper shrink up a lot. Old days they would use straight bannana oil

[kittyfritters]

Nitrate dope does not stop shrinking unless plasticized. This would eventually warp the airplane or tear the tissue. (I tend to keep models a long time, I'm still flying models I built in 2004.) Back in the day, we used to put a drop of castor oil into an ounce of dope to plasticize it. Since 2004 I have been using Krylon or Armstrong Shine Keeper instead of dope.

[twospruces]

ok, well ... that's interesting.
I thought dope "Sealed" the paper and prevented it from shrinking.

So, What I have is fuel proof clear SIG butyrate dope. If I wanted max shrink, should I put that on straight?

How would I know if there is plasticizer included?

thanks

[twospruces]

So, thanks again. I read more about Sig supercoat-

I guess it does the shrinking and the colored dope stops the shrink.


-----
SIG SUPERCOAT DOPE
Cellulose acetate butyrate dope is a paint that was developed many years ago for use on full-scale airplanes. It is a lightweight, fast drying, lacquer-related formulation. Ever since its first introduction, butyrate dope has been a favorite with model airplane builders due to its many unique properties.
Butyrate dope is excellent for finishing any type of wooden model airplane, especially when used in conjunction with an uncoated cloth or paper covering like SIG Koverall, Silk, Silkspan, or Plyspan Tissue. It has the ability to shrink these coverings drum tight and provide a fuel proof finish. Butyrate dope is very flexible, making it the very best paint to use on a model that has open areas in its structure where the covering is unsupported. It will not crack or split from
vibration or flexing.
SIG Supercoat Dope is available in brilliant high-gloss colors and clear. The Supercoat clear dope is a high-shrink formulation, intended for initial wood surface
preparation and for the coating of covering materials that must be sealed and shrunk prior to applying color dope. The Supercoat color dopes are mixed in a special low-shrink base to help minimize warping.
All SIG Supercoat dopes can be brushed or sprayed on with good results.

[kittyfritters]

Butyrate dope does shrink the covering but it DOES NOT have shrink without limit. It does get brittle from age and exposure to UV over the years, but you probably won't fly a model that long, at least without recovering it at some point. You always use butyrate dope on an IC engine powered model since it is fuel proof.

NITRATE dope has the continuous shrinking problem, over a long period of time, unless plasticized. Nitrate dope is used on rubber powered, CO2 powered, and electric powered models where exposure to fuel is not an issue. I haven't used nitrate dope in about 30 years so I don't know if the newer formulations have a plasticizer. There have been fuel proof coatings to cover nitrate dope, but I haven't seen any advertised for years.

I have been using Krylon fixative or Armstrong Shine Keeper, both acrylic products, on my models since I started building again in 2004 because of their lower toxicity and odor. That is unless it is a seaplane or a flying boat, since the acrylic products are water resistant, not waterproof. If you need real waterproof you need to use dope. (Although I did have a model that had the tissue fixed with krylon and painted with acrylic ink get caught in a sudden rain storm while flying without any damage after it dried.)

With any tissue or cloth covering, you have to shrink the covering tight before applying a fixative, dope or Krylon. The fixative, in spite of it's ability to shrink the covering, just makes sure it stays tight, fills the grain to make the covering air tight, and provides a base coat for color. Dope won't rescue a sagging covering job.

[twospruces]

Thanks for the detailed info.
I bought fuelproof because it covers any use I might have, although it is unlikely that I will power up my .020 any time soon.

I`ll give it a try; planes that I have pained with SIG supercoat are *very shrunk*. Perhaps it will just give it that final tension that it is missing in a few places.

Last question - in order to maximize shrink I would guess putting it on un-thinned would be best, and let it air dry slowly.

thanks-

[twospruces]

I think I have evidence of shrink by Butyrate right here. I built this Guillows kit, and painted the win with Sig supercoat to make it waterproof.

Look a the pretzel I ended up with. This happened slowly over time and can`t be recovered. Since there was paper on only one side of the wing and elevator, both warped heavily. The rudder was papered on both sides..no net warp.

[kittyfritters]

Did you only dope it on the top? If you are going to dope single sided covering you have to dope the covering on both sides. But, I'll have to admit, I've never seen butyrate dope do anything like that. I've never used Sig Supercoat. All my butyrate experience was with Aero Gloss over 30 years ago.

[BillParker]

Last question - in order to maximize shrink I would guess putting it on un-thinned would be best, and let it air dry slowly.

NO.

Always thin your dope 50/50 with thinner. I use pure acetone from the beauty supply or home depot... I use Butyrate Dope from Aircraft Spruce. Took me years to figure out that the instructions for using dope were correct. Full strength has to be better, right? WRONG... I shrinks way better thinned. I have however learned that thin structures will twist up like a pretzel if dope is used on them. So, regretably small planes really are better served by clear Krylon Spray, like Howard uses.

my 2 cents...

bp

[twospruces]

Hi, yes I doped only one side of the paper, and there is only paper on one side of the wing, as you noticed.

The twist just keeps getting worse!

Did you only dope it on the top? If you are going to dope single sided covering you have to dope the covering on both sides. But, I'll have to admit, I've never seen butyrate dope do anything like that. I've never used Sig Supercoat. All my butyrate experience was with Aero Gloss over 30 years ago.

[BillParker]

Howard: (butyrate)



Nice custom tail feathers, eh?