Silkspan Will it ever fill ???

[Leester]

I am on about my 5th coat of clear on the wing and there are still little pin holes in the silkspan. I still get dope on the inside of the open bays thats how I noticed them. Do I just keep doping the open bays untill they fill ? or what ? It is medium silkspan.

[Robert McHam]

Sounds like you need to mix some talcum powder in some clear for a coat or two. This should have been your first coats. The talcum seals very well and is cheap and easy to come by.

By the way are you spraying or brushing?

Robert

[Randy Powell]

If you plan a clear finish and use only clear dope, it can take a lot of coats, depending on how much you thin it. Upwards of 8 to 10 if you are using minimal thinner. Perhaps more depending on how well the frame was sanded and prepped and how much dope you put on the structure before the paper. This last plane brushed on 3 unthinned coats of non-taunting clear, sanded a little then sprayed on 2 relatively heavy coats of filler coat (talc and clear), 2 days apart to let the first gas off. Then sanded my little fingers to the bone and removed most of the filler except what was left in the paper and in the low spots. Touched up a couple of spots by brushing on some filler at those spots then sanded some more.. Then sealed the thing with a coat of 80% thinned clear (sprayed) and was about ready for color.

[Jimmy R. Jacobs]

 If you are brush clear dope, use a foam brush. I've had better luck with foam to fill silk and silkspan.
                     Hope this helps.    Jimmy J.

[Robert McHam]

Also if brushing it helps do make sure the work is verticle so that gravity does not tend to pull the liquid through the fabric but along the weave.
Another help would be to let each coat dry thoughly.

There are others that swear by toilet paper to apply the dope.

The good news here is that it is clear dope. The pigment is the killer for weight. Far better to use plenty of clear to get your base finish before you apply even one coat of color.

Robert

[Leester]

Thanks for the tips, I am brushing this on. I'll mix up some dope and talc and try that, I just didn't want to sand the open bays as I know it will sand through. I haven't had this happen on SGM only lighter SS.

[Bob Disharoon]

I suffered the same problem..used 25% thinned dope with a foam brush..the brush really seemed to help

[Dean Pappas]

Hi All,
As Robert said, the saving grace is that clear dope is dead light. I zillion years ago, some of my flying buddies dried down a quart of clear dope and reported that it weighed 3/4 ounce.
Hope that allays your fears about the weight of so many coats,
     Dean Pappas

[Ralph Wenzel (d)]

One other item not yet mentioned is that Nitrate fills much faster than Butyrate. Obviously this is too late to do you any good on this plane, but for the future . . .

[Leester]

I mixed up some talc about 3 tablespoons in a 3" dia jar with about 1" thinner and mixed and then added 1" Butyrate clear. The mixture flows good and is dirty gray in color, can smell the talc. I brushed it on and did not notice dope on the inside of the SS. Anyway I'll let it dry till monday then sand with 400? or 600? the wing has no cap strips so GULP I'll hope for the best. I did shake it up several times while putting it on, how long will this last in a sealed jar ?

[Tom Perry]

I had some that lasted for over thirty years and was still usable.  The jar was sealed and about half full.  I added a little thinner and was good to go.   

[Jim Thomerson]

"Sand' the open bays with bits of steel wool rather than sandpaper.