I wanted to test the wrinkled up polyspan that I had mentioned in another thread. I have my first attempt at a center section of the T-6 wing sitting on my table, and thought that would make a perfect test bed. While on the phone with dad the other night, we got to talking about finishing, and brought up a method of finishing devised by one of the St Louis members. Bob Arata refers to it as "doping dope". The process can be used for any color, but particularly with white, being that white paint is prone to cause weight issues if not applied conservatively.
The trick is to start with the first coat of dope on the model. Add some white paint to the clear dope when applying the base coats. Bob used the TLAR method, or "That looks about right". Trying to be more scientific, I went with one part white dope to five parts clear dope.
Now, there are some givens in this demonstration. The wing panel I covered was hastily sheeted and cap-striped. Care was made to ensure nice fitting parts but not a whole lot. Also, The entire thing was done with a brush to make this easier and quicker. If thats your thing, cool, but a spray gun will turn out still better results.
These first 3 pictures are the base coats with the 5-1 dope mixture. First one isnt too impressive but by the 3rd coat, it looks almost solid. Notice on the first picture, there are some pen marks on the LE sheeting and one of the cap strips. I used scrap sheeting for this. I would never start finishing a model with pen marks still on the wood of course, but I left them on just for S&Gs and to see how well they would be hidden.
Fourth picture has the polyspan on. Tacking the poly down normally using five part clear, five part thinner, and one part white. I put it on wrinkly--made no effort to get any wrinkles out before hand. I used a monokote iron on the lowest heat setting and worked my way up to, i suppose "low-medium" heat. No wrinkles in the finished product!!
Now to finish. Pictures four through 7 show each of four surface coats with the 5/5/1 mixture. Again, each subsequent coat makes the surface more opaque and more solid in color. The last picture shows ONE coat of white dope. To quote the old man, it now "looks like a refrigerator". Completely solid in color. When applied to the actual model with 50/50 color, one coat will still be all that is needed to pull the whole thing together and make the surface even. The idea behind this process is that by starting with the first coat, the white tint slowly builds up so that only one ( or maybe none) coats of colored dope are needed, depending on the color scheme. It would take a great deal of white to get the same effect, and would be allot more difficult to achieve without tipping the scale and adding excess weight.
Like I said, this experiment was hastily prepared and executed, so what you see isnt at all 20 point material simply because almost no surface preparation was made. The purpose was to see how well the polyspan would de-wrinkle, and to demonstrate the "doping dope" method that I plan on using.
Hope someone finds this useful!!
Topic: wrinkly poly and "doping dope" (Read 877 times)