I am trying to find a suitable substitution for the Sig Nitrate Dope. They are hopelessly out of stock and I spilled my remaining quart. I did some research and found references to a product from Randolph and some other brands. They market as tautening and non-tautening. What type is the Sig Nitrate dope? Tautening or Non? Does anyone have a recommedation for a suitable replacement for the Sig Nitrate dope? Thanks, Johnny
I have heard (but not confirmed) that you can get nitrate dope at supply stores for full-size aircraft. Apparently people who build home-made airplanes buy it by the gallon. If you do find a confirmed source, let me know because I'm interested as well.
This is what I found out: (links) http://www.rcuniverse.com/forum/m_5631297/printable.htm http://www.randolphaircraft.com/html/e4964.html Supposedly according to the forum threads Randolph creates dope for many brands including Sig. The Sig website does not say if it is 'tautening or non-tautening' so I wouldnt be sure which to get. But its WAY cheaper by half than the Sig product. If I had more expertise I would buy a quart for 10 bucks and try it out but I wouldnt know the difference. Let me know what you think.
I can't help you with which dope to use question but have you ever tried using weldwood contact cement instead of dope? The fumes aren't as bad and at least as far as I cant tell there isnt much difference in performance. You can thin it down with 50/50 with MEK. I've been using it for years and I've never had a problem with using it.
I tried spray-on contact cement, but it didn't work out very well. fine finish, but the contact cement occasionally failed during the sheeting process. Smash the silkspanned balsa down along a bead of superglue, kick it, let it dry, and let go... only to have the silkspan stick to the superglue but not the balsa. A few additional drops of superglue got the balsa back in place, but it lost the physical benefits of silkspan in the process. This didn't happen very often, but it did occur enough times to be worth mentioning. Tautening vs Non-Tautening... I have seen a few times with butyrate (hot-fuel-proof) dope tautening the silkspan, and the results are impressive. Even the sturdiest 1/8" balsa can be bent by it. That's great if you're going for a bend, but not so great when you want it straight. I figure you can always bend the balsa by hand, so I would choose non-tautening. But that's just a guess, I don't know for certain.
Oooook... I have gone this far. I sent an email to Randolph and this is the reply: I called Sig and the tech support said that Sig Nitrate Dope is indeed tautening, but not as much as butyrate. I have not seen an description on the dopes that said 'slightly tautening' so I am thinking its either tautening or non-tautening. ----------------------------------------------------------------------------------------------------------------------------- Mr. Adams, We too, have strict rules on the strength and penetrability of dope when used on real airplanes with real people inside. You may be interested in our 210 tautening nitrate dope for use on silkspan. It is usually thinned one to one with 286 nitrate thinner. These products are available from our distrbutors in quart or gallon cans. Thanks ----- Original Message ----- From: Johnny Adams To: info@randolphaircraft.com Sent: Tuesday, February 10, 2009 6:15 PM Subject: question about Nitrate dope I don’t know a great deal about these products but we have been using Sig Nitrate Dope on hobby product silkspan. The supply has dried up and we have been unable to get any at all from any source. I needed to find the same nitrate dope in a Randolph product that has the same performance as we have strict rules on the strength of the silkspan after covering with nitrate dope. (It must be penetrable) So if you can tell me which product will do the job I will greatly appreciate it as I am completely out and have projects on hold waiting for supply. Thanks, Johnny Adams -------------------------------------------------------------------------------------------------- So I called the distributor in Texas and ordered a quart of Dope for $11.48 and a quart of thinner for $7.25. I will try it out and see how it works. I think I will make a little wooden frame and sheet it and compare it. They 'set the standard on nitrated dopes' so I am sure it will work. At the very least its nearly half the cost of Sig so I am hoping it works. I went trhough two quarts fast but I didnt cut it 1 to 1 like Randolph suggested. I will try it out both ways as well. Here is the link for the product I purchased: http://www.randolphaircraft.com/html/210dope.html Let me know what you think
I suspect that you and Randolph Aircraft have two different definitions of the word "penetrable" (he's thinking soaks through silkspan and you're thinking shoots through armor), but overall it sounds about right. With that in mind, I see no reason why not to try the tautening dope.
I was at the local hobby store looking for dope. They were all out of my favorite color Polar Grey in a can. They did have two spray cans of it that are now in my basement. The store had another brand of Nitrate dope it from Brodak Manufacturing in CA. They had jars of colors, no large cans and a can of Nitrate.
I dont have the experience to completely evaluate the Randolph Nitrate Dope but here is my review so far. I got a can in to test and its not as thick as the Sig Dope. It brushes on much easier. They recommend spraying it on cut 1 to 1 with their brand thinner. I took a spare piece of balsa and applied the backing silkspan. I took a 2 inch brush and did a quick brush straight from the can. I let it dry and came back and the entire piece had curled slightly. I added the second sheet and did the quick brush and let it dry. After drying it had curled length wise into a half pipe. WOW I am not sure if its usable or not. I will try to cut it with MEK and see if it works any differently. Is there a way to test it without sheeting a ship with it?
reviving a dead thread but thought i would offer my limited expertise on dope. look at wik's aircraft or aircraft spruce.com for large pots of dope. i would recommend a non taughtening dope as well, the taughtening will shrink the sheet just a little and could pull it loose ( especially after a day in the sun) and to look into Stewart Systems as it is waterbased and as waterproof as anything else once dried however it is more expensive.
The Brodak dope works, but the stuff I tried was /thick/ and needed a lot of thinner to be useful. I tend to like the finish that nitrate gives on my hulls. Less wrinkles and bubbles. The full scale airplane guys like the Butylrate dope for covering fabric planes. It was developed around WW1 to replace the nitrate dope that was in use. (Nitrate dope being made using cellulose dissolved in nitric acid) For some reason, pilots found the flammability of fabric coated with nitrate dope to be disadvantageous.... can't imagine why Butylrate is simply cellulose dissolved in butyric acid. It's less flammable, but doesn't tauten as much or adhere fabrics as well as nitrate dope. So airplane folks tend to use nitrate first and then put several coats of butylrate over it to reduce the flammability. FAA has a nice PDF on the subject: https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/amt_airframe_handbook/media/ama_Ch03.pdf
I took advanage of my states warmest nights in it's history for the month of december, to finished my hull sheeting . Hobby Town hasn't even heard of Silk Span. So I had to find a suitable substitute. I was just about out the door heading for the Dollar Store to buy craft tissue , when my wife hands me an old dress pattern. She imforms me that I could iron it with a pretty hot iron to get all the wrinkles out. "it's built to take it". ( maybe I'm out of the dog house from that unfortunated epoxy mishap with her hair drier.) I sheeted both sides and used Sig dope that I got from my bother inlaw, that looked as old as he was. But it spread ok, I guess. I hope I did the right thing by putting sheeting on both sides.
