09/06/2014 at 8:17 pm #42244Daniel HopkinsParticipant
I was wanting to try this method and in general I am pleased with the results. But I have a few questions/observations.
So I covered the wing and stabilizer of the model with 1/4Mil mylar from FAI supply and wet covered the mylar with light silkspan from easybuilt models using SIG nitrate dope. So far so good. Looked nice and seems very tough. Tougher than another model I covered with SGM. Since this is a gas model (1/2a Fortastrop) I thought I should fuel proof it so I used Randoph clear non tauntening butyrate dope thinned 50/50. I have since read that butyrate dope is note quite the fuel proofer I thought it to be.
Anyway the butyrate seemed like it was attacking the nitrate dope. It is warm out +80F but in the shop it is about 70F. In the end it is all fine except for looking a little blotchy. So my questions are:
Butyrate over nitrate bad?
Mixing manufactures bad?
Should I have sprayed the Butyrate on rather than brushed?
Thanks in advance
dlh9837009/06/2014 at 9:08 pm #54970Glenn SchneiderParticipant
The real advantage of tissue over mylar is the relative waterproofness. The tissue does supply the stiffness desired that the mylar does not. I have used butyrate alone on my projects, giving the mylar a coat then tissue over with butyrate, then slosh the tissue with thinner rubbing it lightly with the fingers to draw up the underlying dope into the tissue. A single coat of thin dope, then it is ready for a brushed out thinned coat of KlassKote@for fuel proof. Generally, it is OK to put butyrate over nitrate but not the opposite. The chemistry is probably more important than the different manufacturers. I almost never spray any of these projects, usually thin the dope or epoxy to the same consistency that one would use to spray then brush it on in several directions. Works for me. Thermals, Glenn09/07/2014 at 2:06 am #54971Mike SchwartzParticipant
On the first Series 70 Satellite 1300’s, we used mylar on top of the tissue. This method allows you to use nitrade dope on the tissue and the mylar is 100 percent fuel proof. You can soak mylar in 100 percent nitro-methane, clean if off and let it dry and then apply the mylar over the tissue with no ill effects. This is just an example of its fuel proof abilities. The mylar is very reflective and gives the appearance of multible coats of dope without the weight penalty. Mylar provides a high puncture resistance to the covering. Bill Hunter’s article on mylar covering in the Oct. 72 issue of American Aircraft Modeler magazine goes into a lot of detail on the use of mylar. I have a copy of the article from the magazine and it is 4 pages long. if you don’t have the magazine issue, you can go to the following web site which has the article for you to read and download. http://www.airplanesandrockets.com/mylar-oct-1972-aam.htm. Hope this helps clear up any questions on mylar covering.
Regards, Mike09/07/2014 at 5:23 am #54972Steve JensenParticipant
(If Mike’s URL doesn’t work)09/07/2014 at 5:51 pm #54973Dean McGinnesParticipant
There is another side to this–surface roughness of the tissue providing turbulation across the upper wing surface. The FAI Sportsmen have had good success with the smooth surface on the bottom with Icarex or some other covering providing roughness on the top.
This could be easily done with the tissue/Mylar combination.09/13/2014 at 5:01 pm #54974Daniel HopkinsParticipant
Will have some pictures of the results soon.
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