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Feb 28, 2017, 07:45 PM
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Have an old silk and dope covering question


Last Fall I aquired an old SE5 Top Flite assembled plane that was covered in Silk and dope. The Silk is a yellow colored material and was unpainted other than a coat(or two) of clear. Seems the covering has become a bit "brittle" over time as it seems to tear kind'a easily. The silk seems to be a light weight grade and perhaps that is as much of the problem as any. Back in "the day", I have done some silk and dope but it's been many years ago. Other than recovering, anybody have thoughts as to how this might be corrected or halted??? So far, patches seem somewhat realistic but....
Thanks in advance.
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Feb 28, 2017, 08:17 PM
B for Bruce
BMatthews's Avatar
The model was likely stored somewhere the sun was able to shine on it. Over a few years the UV really does a number on the silk. A buddy has had to recover a few silked models over the years due to this.

There's no way to "fix" it. The damage to the silk is done. If it's that fragile then best to sigh and strip the whole model and use something else.
Mar 01, 2017, 08:06 AM
Brighto?
Mike Denest's Avatar
You could try "rejuvenating" it with a spray coat of clear butyrate dope mixed with Randolph rejuvenator but it may be a lost cause. The problem is dirt and other crud that may have accumulated on the surface, making it difficult for the fresh dope to stick. You might try a small area to test the fabric before you get too far just to see what happens.

You should look at this thread to get some ideas. https://www.rcgroups.com/forums/show...storing-models
Mar 01, 2017, 12:30 PM
B for Bruce
BMatthews's Avatar
It's not the dope though. It's the silk within the dope. The UV makes the fibers break down and lose their resiliency and strength. It reduces the silk to something like weak tissue paper as a substrate.

I've seen and punctured first hand while we were transporting his models to the meets. A few years being out on the field in the sun and it's almost impossible to handle the wings without rupturing the silk from the slightest misplacement of the grip.
Mar 02, 2017, 07:41 AM
Brighto?
Mike Denest's Avatar
Then it's time to get the acetone and old rags out to take it off. Messy but it works.
Mar 04, 2017, 12:03 PM
TonyE

Following footsteps Black Magic


Similar occurance, the Black magic (2.5cc R/C) airframe I made back in 1978, followed me on every move around Europe, and I have just restarted the hobby after a bit of a break !
Some of the covering had gone saggy with the fuel, and some brittle with the sun.
Removed it all, cut out some rotten bits, sanded and doped the woodwork, and then applied wet-doped nylon, did the fuselage this afternoon, not looking bad for a first attempt after a long time,
just need to remember to leave plenty enough of the nylon each side of the wood to allow a finger pull to tighten it...While it was stripped I converted to electric flight, more work than the original build!
Interestingly, the balsa spars after 36 years, pickled in the original dope, were as hard as spruce, amazing really, like good wine !
Mar 09, 2017, 09:15 PM
Culper Junior
How about Doculam? I bought a silk covered Lanzo Bomber that was very brittle. Fixed the tears, then ironed Doculam right over the silk. I like the result, still looks like silk but is almost puncture proof now. And the wing is much stiffer now.
Dec 02, 2020, 11:12 PM
Registered User
Quote:
Originally Posted by aeronca52
How about Doculam? I bought a silk covered Lanzo Bomber that was very brittle. Fixed the tears, then ironed Doculam right over the silk. I like the result, still looks like silk but is almost puncture proof now. And the wing is much stiffer now.
been reading on doculam....very interesting stuff
Dec 03, 2020, 02:50 PM
B for Bruce
BMatthews's Avatar
I've seen lots of folks using Doculam under the silk then dope the silk onto the Doculam. Saves using lots of dope as sealant to fill in the pores.

But this is the first time I've seen anyone using Doculam over an older covering. That's a highly interesting idea!.

Some extra care is likely needed as you iron it down onto the old surface and you'd want to use care to avoid air bubbles. But once it's down that would be an interesting option.
Dec 06, 2020, 05:04 PM
Registered User
ErcoupeEd's Avatar
I will have to research the "doculam".
Anyone care to tell me where I can get some ?
When I was teenager ( a few years ago, lol! )
My Dad showed me how to mix in a small amount of castor oil into the dope to help keep it from getting brittle over time, using either silk or silkspan.
Dec 07, 2020, 02:07 PM
B for Bruce
BMatthews's Avatar
Just do an Amazon or Ebay search for "thermal laminating film" and lots of options will turn up. I ran the search on Amazon and got back a few different options for around $50 that would give you pretty much a life time supply of the stuff being 12" wide by 200ft long.

The few drops of castor oil not only helped with stopping those things but it also somewhat reduced the long term shrinking. And yes, very much old school. When I started out the books on model building from the libraries that were written in the 40's and 50's typically called for adding a few drops of castor oil and thinning the dope well for use with lighter structures.
Dec 09, 2020, 01:33 PM
Registered User
N1EDM's Avatar
A friend of mine has been telling about using a clear kitchen shelf material (which shrinks with heat) that he puts under silk the way that BMatthews describes in Post #9.

I haven't tried it myself but my friend is a very experienced modeler and knows what he's doing. I'd trust him.

I just thought I would pass this along.

Bob


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