Thoughts on using modern butyrate dopes

SuperDave Sun Oct 23, 2011 9:59 am

Building my Brodak "Lil Toot" bipe my thought was to do it "retro-style" as I did many years ago with buytrate dope in two colors: red an white. I selected Brodak as my supplier.

What I learned might be instructive to others contemplating the use of modern butyrate. Simply put it is NOT the same a the Aero-gloss of old. It's more complicated than I would ever have imagined. For this I can't fault Brodak but since what I have to write should be understood by anyone contemplating doing the same.

First, butyrate and it's necessary components are EXPENSIVE: dope, thinner, retarder etc. especially the shipping cost from Pennsylvannia included. Don't cut yourself short on thinner and retarder because butyrate from the can will dry almost immediately upon exposure to the air. To get it flow correctly it must be thinned with 2X thinner and retarder by volume. Otherwise with a brush you simply won't have time to properly apply the dope.

Since this plane is a bipe with a 16" wingspan it is very compact to work with a brush especially if you are short on thinner and retarder. I got 4 oz. containers except for the retarder which came in a pint. 4 oz. may be fine for the colors but certainly not for the thinner and retarder. And even more so if one plans to apply it will the a spray outfit.

I have a bit over $50 invested in the materials that I ordered and I should have gone for at least $30 more to be safe. I've yet to try synthetic covering but this episode is strongly pushing me in that diection.

Just thought you'd like to know. Judge accordingly for yourself. ($80 is pretty expensive to finish a plane with a 16" span)

PV Pilot Sun Oct 23, 2011 10:53 am

The warmer the outside/working area temp, the more retarder you'll need as well.

If you don't have either thinner or retarder,,get ready to lay it on REALLY thick and work as fast as Flash Gordon with a sponge brush, or you'll have stop and start brush stroke lines in the finish.

I don't think I'll brush another one with Brodak stuff, it will be shot with a automotive touch up gun.

The Brodak stuff is not a hobby blend,(if there is one). It's a full sized aircraft consistency from Randolph finishes packaged in a Brodak labled can.

SuperDave Sun Oct 23, 2011 11:04 am

PV:

It's one of tne great dimensions of this forum that we can share each other's experiences with products both good and not so good.

What is your experience, if any, using SIG butyrate products?

I'd also toss that question to anyone who DOES have expereince with SIG butyrate products.

Input appreciated.

gcb Sun Oct 23, 2011 11:11 am

Dave, you are correct. I usually get thinner in quarts and colors in pints, since I build small planes and do minimal (sport?) finishes. Some folks buy clear and thinner in gallons.

Blame our government for the high prices. They keep banning ingredients so the products seem to get degraded somewhat. I believe the latest victim is the banning of MEK, one of the ingredients in most paint thinners and paint removers.

I think I may experiment with various wood finishes like urethanes, especially the water based ones. I may try some of the iron-ons also, but I prefer paint.

Brodak dope was formulated from Randolphs, with help from a modeler (Windy Urtnowski) who is noted for his magnificent CL Stunt plane finishes. I think all dopes (except perhaps Aerogloss) came from full size airplane dope. I doubt there was ever a market for models large enough to sustain production of dope. I believe within the last year or so, Brodak started mixing their own dope in house to maintain tight control over it. You can call John Brodak and get more details on this.

BTW, for those who fly CL, John Brodak sponsors a "Fly In" in his back yard every year that equals the size of the AMA CL Nats.

I have used SIG dope and like it. I use Sig and Brodak dope.

George

SuperDave Sun Oct 23, 2011 11:46 am

George:

Having lived into my mid-70"s I well remember funding my youthful ventures into modeling with the proceeds from my paper route. (I still have my trusty Veco .35 in it's original box marked "$15.95") Although modest, my route money seemed to stretch farther than the funds that come from my retirement checks, Social Security etc. In effect, my "discretionary money" just doesn't seem to strech as far as it once did even when I was saving as a kid to attend college.

I know, times and circumstances change and not always for the better.

John Brodak DID include a nice instruction manual with my order but I wish it had been available prior to that. If I had know what was realisically involved I would gone directly to synthetic coverings as less expensive alternative then butyrate.

andrew Sun Oct 23, 2011 12:25 pm

I buy my clear high-shrink and low-shrink butyrate, thinner and retarder from either Aircraft Spruce or Airsuppliers -- this is for Randolph dope. Pricing moves around, but Airsuppliers currently has butyrate quarts for 13.58 and low-shrink for 14.53. Thinner is 9.84 and retarder is 12.88. There are no hazmat shipping charges on quarts, regardless of how many are shipped.

I have used commercial lacquer thinner, but it can cause some colored dope to clump or separate. It works pretty well for cleanup and saves the more expensive butyrate thinner for painting.

I've read about using pigment for coloring clear dope, but never tried it. Given the high cost of colored dope, it would be worth looking into in more detail.

andrew

gcb Sun Oct 23, 2011 12:27 pm

Dave,
I hear you on the SS situation. I turn 70 next month and understand the retirement thing.

I remember standing in my LHS in my teens, deciding whether to get the Ringmaster Junior for $!.50 or the newer Jr. Flite Streak at $1.95...I went for the Ringmaster Junior for price. A medium tube of Ambroid was $0.25, a bottle of Aerogloss or Testors was $0.49, and a sheet of 1/16"x3x36 balsa was $0.12...those were the days.

I have not bought dope since the prices went up, but I'm getting to the end of my "stash" so I'll need some pretty soon. It's an opportune time to try the poly-U for the base coats.

George

andrew Sun Oct 23, 2011 12:41 pm

gcb wrote:I have not bought dope since the prices went up, but I'm getting to the end of my "stash" so I'll need some pretty soon. It's an opportune time to try the poly-U for the base coats.

I experimented with poly-U some time back --- I was using it to apply .5 oz. glass cloth to foam cores to stiffen the core and harden the surface. It did both of those, but when I used it as a fuel proofing, it got gummy. Bipe Flyer, from RCU, had better luck using it, but it was a different brand. I used MinWax, he used Behr (sp?). You need to do several test strips to check it out. It will surface coat, but does not shrink.

SuperDave Sun Oct 23, 2011 1:17 pm

Or another avenue to pursue would be to apply a coating of clear finishing resin (such as Pacer's Z-poxy) over colored dope that is not fuel-proof. I KNOW Pacer's Z-poxy is fuel proof because used it on my Dumas "Lil Swamp Buggy" /throttled Sure-Start combo.

BTW, I've had unsatisfacory results using Tower Hobbies equivilant finishing resin which is less-expensive by several $$$$$. (Yes I followed Tower's directions).

nitroairplane Mon Oct 24, 2011 8:32 am

I'm a bit late on this thread as I'm on holiday with an unreliable Internet collection.
But that is a lot of $$$ compared to what I pay.
For a 20" ff model I spend roughly 25-30£ on materials that's no more than $50.
and I use butyrate and tissue.

gcb Mon Oct 24, 2011 9:08 pm

SuperDave wrote:Or another avenue to pursue would be to apply a coating of clear finishing resin (such as Pacer's Z-poxy) over colored dope that is not fuel-proof. I KNOW Pacer's Z-poxy is fuel proof because used it on my Dumas "Lil Swamp Buggy" /throttled Sure-Start combo.

BTW, I've had unsatisfacory results using Tower Hobbies equivilant finishing resin which is less-expensive by several $$$$$. (Yes I followed Tower's directions).

I haven't used finishing resin in years. If I remember correctly, the brand name was Frances's. It was not an epoxy but a Polyester resin. I believe it would melt foam wings. :-(

George

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