rustyrivet

My Feedback: (6)

Well, now that I bought a $50 gallon of Brodak's brand BUTYRATE DOPE, do you think it will work fine enough with silkspan? I thought dope was dope, was dope, and didn't realize there were two different types. (NITRATE DOPE being the other type availabe).

I had told the guy at the LHS that I didn't want to wind up buying 37 little 2 oz. bottles of "Dope" at $2.69 a bottle after I had started my project! (And running out of the stuff 37 times while in the middle of the work) So this is what he sold me.

What's the difference between the two, and does it matter a lot?

Flypaper 2

Butyrate is fine for what you are doing. many guys use nitrate for sticking down the silkspan for better adhesion but I use butyrate for adhesion and finishing. Nitrate is not fuelproof, but butyrate is. You can put butyrate on top of nitrate but not the other way around unless you want a nice wrinkle finish. Most butyrate needs to be cut with thinner for brushing or spraying. Any more questions just holler. P.S Its becoming a lost art.

Ed

You done good !

rustyrivet

My Feedback: (6)

Gord,

I'm still trying to make up my mind whether it will be silk span or Sig "Koverall". But concerning the type of dope finish:

The older and experienced guy at the hobby shop warned me that Nitrate dope is preferable because I don't have to concern myself with the covering becoming too tight and warping the structure, as it could with Butyrate dope. I had warping problems on the 1/16" stringers on my Guillows 34" model using Butyrate dope, and learned real fast how to use it and avoid this. However, it's been 6 years since I last used the stuff, and I don't want to learn again on my 89" model. But this time I'm also not dealing with 1/16' balsa stringers to worry about either.

Also, I read the label on both the Sig products. On the can of Sig Nitrate it says to use the nitrate only for the frame and ahering the material to the frame. It then says to use Butyrate dope when it's time to cover the whole surface.

Yet, on the can of Sig Butyrate dope, it seems you can use the Butyrate to do the whole job! So unless the Butyrate realy poses a warping or shrinking problem much more severe then the Nitrate, I don't see the advantage of using Nitrate dope.

So I want to get your blessings that this might just be a personal preference of this older and experienced guy at the hobby shop I don't need to necessarilly follow, and the Butyrate dope will not bend my enlarged 89" Sig Astro Hog into a pretzel !

Flypaper 2

As you say,Randall, It's a personal preference thing. I never had any problems with using Butyrate only. I would still only use silk as I know the silkspan wont be strong enough. Just dope the framework first, then dope the silk to the framework starting from the middle of the wing and working outward. It need not be tight, just smooth and no wrinkles. If the dope dries to fast and gets stuck down,put on a little more dope or thinner to soften it. I use a Windex spray bottle with water to just dampen the silk abd it will shrink up nice and tight. Any more questions just yell. Glad to help.

rustyrivet

My Feedback: (6)

Thanks Gord,

I have been going back and forth between here and the "Tips and Techniqes forum" where I asked about covering material as well.

Seems just like you say, that Sig Silkspan is just not strong enough for a 89" Hog. But a lot of folks seem to feel Sig Koverall is ok.

My LHS carries it, and that's what I'm feeling safe and planning on going with.

-Randall

Flypaper 2

Take your time and do a good job. Post a picture if your able to. AsI say just holler if you need a hand.

Walter D

My Feedback: (16)

Randall, if you can, get your hands on a Sig (even an old one) catalog, do it, it explains nicely the differences between all these different coverings, its atributes and best way to use them, and how to apply a covering that requires the use of dope.
Flypaper and I agree on the same principle, butyrate dope will do the job nicely from beginning to end, I've used it for 27 years, and never had anything become unstuck, never a bubble, never a wrinkle and never a warped surface, and I'm referring to models from .40 on up to 9 feet in wingspan and radio controlled, with glow and/or gas power, and also diesel.
By the same token, I've had friends that like to use nitrate to stick the material down and sealing, and then finish painting with colored butyrate (as only it, is fuelproof).
I wouldn't hold an open flame to neither one of them, but remember that nitrate is extremely flammable, not so butyrate, I keep this stuff inside my garage, so safety is important to me.
Having a model that used nitrate and butyrate sit side by side to one that only used butyrate, and there is absolutely no difference at all. If you are going to use dope in delicate models, where surfaces could warp easily, Sig sells a low shrink butyrate dope.
As far as covering is concerned, for radio control use, I would only use silkspan (this is more like paper) on fully sheeted surfaces, it works great here, on open surfaces, you can poke through it very easily, not good.
Silk (rayon) is very strong and very light, but somewhat expensive, it is used on either planked or open surfaces, and it is probably the lightest of all materials, a well done finish by using dope and silk, is a thing of beauty.
Koverall (polyester), is the same as Super Coverite, Coat lining material, they are all of the same family, just a little different weight, these materials when used with dope are probably one of the best and strongest finishes you can have on a model airplane, they impart tremendous strength to the overall airframe, on all of them, except Super Coverite, you'd have to use dope on the wood to assist in the glueing of the material to the frame, and fast acting dope glue, like balsarite, to first glue the edges, in order to be able to do the rest.
Super Coverite, on the other hand, already comes with glue on one side, and it sticks very well by just the use of a hot iron, although more expensive than the others, it is worth it, as it saves on a lot of time when covering, these materials do not trap air when being applied, as films do, thus a much better finish is achieved, as the material will stay put without sagging or wrinkling, Coverite used to have a material that even had a painted finish, Permagloss I believe was called, and it was great as it didn't have to be painted, it however lacked the ability to hold its shrink and would somewhat sag in areas like wing ribs.
All of the above materials have to be painted, as they have no finish. Once you learn to use them along with the use of dope, you will be surprised at how fast you can finish them and how well you'll make them look. Any finish that you use with dope, can be painted with whatever kind of paint you want to use, just give the dope a good 4 or 5 days to fully cure, before doing it.
Hope this helps a little bit the use of these materials, good luck!

bones99

My Feedback: (3)

Hi, just a word here because I didn't see it brought up in the other replies. When I was building in the 50's and 60's and used silkspan or silk on all the models, nitrate dope was not fuel proof. You had to use a fuel proofer over it. Butyrate however was fuel proof and did not require a fuel proofer over it.
Bob

Flypaper 2

I think we've all forgotten about Micafilm. Memory goes to h*** when your an older fart. Have been using it for a long time. Building a 60 size TF Corsair with all the control surfaces covered with Micafilm. About as strong as silk but a much lighter finish. Stronger and lighter than any of the plastic finishes, also stays tight. I think it's one of those sleeper finishes, put it on and forget it.

Walter D

My Feedback: (16)

I don't think it is still available, is it? I never used, but it seemed very strong too.

rustyrivet

My Feedback: (6)

Walter,

I plan on using Kovearall. If as you say, Koverall is the same as Super coverite, then does this mean the Koverall has adhesive on one side for ironing it on? Also, do I apply the Koverall damp just like I did with the Guillows tissue?

When I did the Guillows model, I would prepare the balsa surfaces with butyrate dope. I would then apply the damp tissue onto the balsa, applying butyrate dope on to the perimeters of the tissue to hold the tissue down onto the already butyrated wood. Once it was holding firm, I would let it dry good. I would then dope the entire tissue surfaces with light applications, sanding lightly between the dryed cotes.

Can I use Koverall the same way? Or do you recommend I use that Sig "Stix-it" on the balsa perimeters to hold the Koverall down?

This oversized Astro Hog is going to have the traditional paint scheme in red and white stripes. I will use red and white pigmented Sig Butyrate dope sprayed on for the final paint finish. So that will pose no problems, and I have no concerns with that.

Walter D

My Feedback: (16)

You would have to use Stix-it to glue the perimeter down first, as Koverall doesn't have glue on one side, you don't use water to lay it down, this is not like silkspan, this is a true woven polyester fabric, you will use a hot iron, get the kind that we use in the hobby, as regular clothes irons are too heavy and big for this job, use stix-it on the perimeter only, and by applying the hot iron on the material, it will stick to the surface, do the entire perimeter, stretch the material as much as possible with your hands and then start shrinking it, these materials like to have the iron pressed down, instead of just having it slide over the surface, as you would with Monokote, do the bottom of the wing first, then the top, bottom of fuselage, sides and then top.

Derek_TX

My Feedback: (1)

Here is a summary of what I gleaned making models since the mid 60's. I have made all kinds of airplanes and used both with great results using these guidelines. Sadly I havent used either in a decade.

Nitrate dope - less shrink, not fuel proof,will not work on top of butyrate dope, typically used for lighter applications

Butyrate - greater shrink, fuel proof, applies without problems over nitrate dope

I think the real core difference is in bold.... the fuel proofing qualities.

... but I never understood why anyone would use both.

rustyrivet

My Feedback: (6)

Walter,

Yes, I do own a Top Flite variety iron and have applied Monokote covering to many a trainer plane in the last 12 years. So I am very familiar with applying heat shrink type materials.

But the description of this SIG Koverall stuff useage confuses me, as it doesn't seem to fall into either category. It doesn't go on the plane either like silk span, or like Monokote.

Ok, so Koverall doesn't have adhesive on it. And it sounds to me too that I can't use the Butyrate doped balsa surfaces alone to hold it down, like when covering a Guillows model. So then first I dope and prepare all wood surfaces. Then when I'm done preparing the wood surfaces, I apply the Koverall using stix-it to hold it down. Then I'm ready to start spraying or brushing on my Butyrate dope onto the koverall surfaces ?

If I put the koverall on pretty taught, do I have to worry about the Butyrate dope warping the surfaces? And does the heat iron ever get used again when working with this stuff? Or is the iron used only to activate the hold-down areas where the stix-it was applied?

DEREK,
Thanks for your input. I have already purchased $50 bucks worth of Butyrate dope, and have pretty much ruled out Nitrate dope. I prefer painted surfaces for my PRIZED models that take me a year or longer to build. And where I can't use glass I will use dope. I'm probably going to offend some folks, and I wish they wouldn't take it personal, because as I too have some VERY nicely Monokote planes that I have built. But I hate that stuff!! (Especially on a warbird) It belongs on a gift box! Thus, the answer why I would use Dope Finishes.

Derek_TX

My Feedback: (1)

There is true quality to the doped planes. Nothing looks better imo!

Monokote has many great qualities, but the surface luster of a good doped airplane isn't one of them. Monokote can look better in some ways too, but there is no nostalgic feeling with the plastics.

I am not sure what Koverall is but I have used many types of materials with dope. I used a type of covering in the 70's that was not a weave, but rather a spun matte. I would adhere it to the wood with dope painted onto the wood. One coat on the wood, let it dry, apply a second. Once the second coat was applied, I placed the material over it and painted the wood areas with another coat of dope to seal the edges to the wood. I would pull the material to remove any wrinkles and if necessary, pin it down to kep it in place.

The covering was ironclad! I couldnt drop a blunt object on a wing and get it to pierce. A knife would though. *chuckles* If...err, when I would break the ground barrier with the planes I would have a doped bag of balsa. Wish I could remember what it was called.

The same technique worked with silk or nylon. Nylon make bullet proof, but heavy coverings. Silk was the covering of choice for me for years.... ehh, until the plastics came :O

I think you would do just fine using the dope to adhere the edges just like you do tissue, but the balsarite type adhesives are more convenient & fast - due to the ironing speed. Be careful shrinking synthetic cloths with the iron too much, as the dope will shrink it again as it dries. Might get too much stress buildup. It think Koverall is similar to the material I used in the past, or like nylon for that matter, and several methods of attachment will work just fine.

The secret to good dope jobs (like any finish really) is surface preparation. Make all the wood grain lines go away with the lightest filler you can. I used to use balsa fillercote from Aero Gloss - not necessarily the lightest! Many coats, all almost sanded completely off until the last one which is applied when the grain lines were fully filled.

BTW, is the gallon of dope clear?

Walter D

My Feedback: (16)

As not to confuse you, if you have used Monokote before, the steps are pretty much the same, the reason to brush a couple of coats before covering is that, after you have covered the area, and apply the top coats of dope over the Koverall, the strong solvents will soften the coats under the covering material, thus glueing it to the surface.
When using Koverall, after the airplane has been covered, and before brushing the dope on, use your heat gun to shrink it, in sheeted areas use the iron, using slight downward pressure, remove wrinkles as much as possible, now you can start brushing the dope, use a "good quality" soft bristle brush no more than a couple of inches wide, two coats minimum, 4 to 6 is ideal, after the first two coats, using the brush, the other 2 or 3 can be sprayed on, if doing it this way, the dope has to be diluted with lacquer thinner, the Home Depot variety is fine.
Wait until one coat dries, before starting on the next one, when spraying, most coats will go pretty much one after the other, as it dries very quickly, as much more solvent is being used.
Tips:
When brushing the first coat, do not brush on top of wing ribs and fuselage formers in a perpendicular fashion, as this will have a tendency to squeeze the dope out of the brush too heavily, and it will sink under the material and form globs, brush, instead parallel to ribs and formers, for the first coat, after this one is dried, it will not seep in under the material.
When brushing, don't be tempted to go back to areas that were just brushed on, as you'll leave marks on the almost dried out dope, just keep on going, do it slow and moving forward, any areas that haven't been well covered will be so on the next few coats.
A very light sanding every two coats is ok, but I mean very lightly, sand dry, with maybe a 320, just slide the paper over the surfaces, you don't want to cut through the material, just remove the fuzz, wipe clean, and then go on to another coat.

The step of pressing down the iron when covering as opposed to just gliding it over the covering applies better to Super Coverite, which has glue on on side, thus, by maintaining the iron for two or three seconds in one spot promotes better adhesion to the frame, when using dope, is not as necessary.
How much dope to use? Until the surface takes on a sheen, or a very dull shine, the material in open surfaces will be very taught, if dropping a coin on it, it should bounce right up, by thumbing it with your fingers, it will sound like a drum.
It sounds much more complicated than what it really is, the worst part is to glue all the edges and finalize the covering part,
you won't believe how much the dope will shrink that material overnight.
If when brushing, the dope wants to dry too fast, add a little bit of lacquer thinner as you go, but you don't want it to be too watery, at least for the first two coats, these are mainly the ones that are going to glue the material down.
It is best to do this in well ventilated areas, outside if possible, Lacquer thinner and dope sting to high heaven, and if married, divorce is eminent!

rustyrivet

My Feedback: (6)

Thanks Gentlemen,
I appreciate all the detailed input.

big max 1935

My Feedback: (9)

Well heres my 2 cents worth. No matter what dope you use,add a few drops of castor oil.This keeps the covering from becoming brittle with age.Also a hint to dopers,check your local air ports&spray plane hangers for dopes.Have had it give to me just to get rid ove it.EPA you know.Have not seen mention about bamboo paper yet.now talk about an old fart!!!