CWLWL

Can POLYURETHANE (CLEAR ) PAINT replace DOPE 's role in covering silk or nylon type materials?
DOPE is not available here. I tried PU one some frameworks, but seem not as ADHESIVE as DOPE when dried.I can't tell it is definitely not adhesive, but according to my memories it seems so.
Anyone could kindly offer some opinions here?
Thanks a lot.

DL

Azcat59

I have covered many planes with silk, and I do not believe that poly-u will work, either to adhere the silk, or to fill the weave. There must be some source for nitrate or butyrate type dope if silk is being used, and even for full size planes that are fabric covered. Good luck finding some!

Clair

Jim Thomerson

You can use Titebond glue thinned a little with water to adhere silkspan or silk. You can also watershrink silkspan or silk with a little Titebond in the water. It will make the covering more opaque than clear dope. You can use thinned Titebond as a filler coat on wood or over open bays. Just sand it gently as it will get soft with heat. I've been told you can put water-based poly-u on wet silkspan and it will end up looking good. I have not tried this and I suggest you try a small test panel to see if any of my advice is useful. I think Titebond is an alphatic resin glue. I don't think it is fuelproof.

Hope this helps,
Jim

ballgunner

My Feedback: (1)

Dope, both butyrate and nitrate are available from Sig. Whether or not it can be shipped to you is another question. Perhaps if they labeled it model airplane parts instead of dope it could get through.

J_R

Titebond is aliphatic resin.. yellow wood glue. It is fuel proof when cured. I use it, watered down, instead of epoxy to seal the inside of the fuse and any areas around the engine where fuel might attack raw wood. It sure weighs a lot less than epoxy when it is dry. If you have ever put a horizontal stab in a slot in the fuse, it works great. It cleans up with water.

BTW, CA is not fuel proof.

JR

probligo

JR,

A word of warning - some aliphatics are not water-proof. How do I know? Imagine a ff HLG "disassembling on launch" and you have some idea[sm=spinnyeyes.gif][sm=idea.gif]; the result of flying over long grass after rain.

J_R

Was it white glue or yellow? How long did it cure before it let go?

CWLWL

Thank you all of your kindly replies.

I am in HONGKONG.

One thing I want to made clear is that the PU I mentioned is formally called POLYURETHANE VARNISH, it comes with 3 parts to use, 2 PARTS OF B+ 1 PARTS OF A+ THINNER to apply as instructed. IS IT THE PU in USA the same thing as this?

I will try again to experiment with PU to cover silk on a LARGER area of framework sample to see if it held will onto it.(at least acceptable level). BTW, from last time experiment result, I can spray paint onto the PU covered silk but seeing grains, it doesn't varnished even I brushed as many as 5 times onto it. I THINK THIS IS ANOTHER IMPORTANT ISSUE WITH PU COVERED FABRICS.
Anyone have an idea to hide the grains to a level so as to have a gloss effect? (even if dope can be available and used)

Jim and JR,
Thank you for info about TITEBOND, do know that ELMER brand white glue is SIMILAR STUFF AS TITEBOND YOU MENTIONED, and if so, do you mean that can be used to replace DOPE as described. Also think you for info about CA, is it really not glow fuel proof? If so I will be in trouble, but it doesn't react for 10% which I am using, can WHITE GLUE used as fuel proof layer in fuel exposure area, like engine bay ?

Regards,

DL

J_R

White glue is NOT fuel or water proof. CA does not dissolve rapidly in fuel. If you take a lump of cured CA and put it in a sealed jar of raw fuel, it will eventually dissolve. For modeling purposes, it is fuel proof enough for almost any use. Just wipe the fuel off at the end of the day. It can be of concern when the wood gets fuel soaked at the joints. It is more a point of interest than a point of concern.

Polyurethane is used in a rather generic way in the US. It can come as a two part product, as you are refering to, or as a one part.. ready to apply product. Having never used it for your intended purpose, I will not venture a guess as to how it might work. As someone else suggested, make a mock up and try it before applying it to your model.

JR

probligo

It was one of the yellow aliphatics. It was left for at least a week after building - because of the weather down here you know.

BTW I have since only ever used aliphatics for gluing down tissue. At least that way it is under dope and waterproofed.

Why "no dope" on the hlg? I dope prior to assembly. CF booms need none. I now use epoxy and ca exclusively.

rnlocnil

There are at least two kinds of aliphatics. The original, and then the water resistant, such as Titebond type 2. White glue is something else.

Model airplane dope is very similar to dope used on full scale airplanes. Perhaps if there are people building fabric covered airplanes in Hong Kong, you can get some from them. BTW, if you do find dope, it may not be as adhesive as it used to be, though in my experience the stuff for full sized airplanes is much stickier than the stuff for models, and FabTac is REALLY sticky. I have some good dope from Aircraft Spruce, but somehow I doubt they ship to Hong Kong. Remember that nitrate is stickier than butyrate, but nitrate is not fuel proof.