Covering a fuse in silk - how to trim it?

[pmackenzie]

I have run into a problem here, hoping someone can give me some ideas.
This is not C/L, but I will ask here anyway. I figure there are some here who might know
And depending on how this works out, I could see doing a stunt model in silk at some point.


Covering a model in Silk for basically the first time (I think I covered a couple of wings in silk ~40 years ago ).
Actually doing silk over 1/2 mill Mylar. Started on the fin and rudder, made some mistakes, but it turned out OK.
Moved onto the stab, learned some more tricks. So by the time I did the wing I was quite happy with how it came out.
(I will put a black tissue trim stripe between the red and the yellow sections on the wing, to cover the slightly way trim line.
It is pretty much impossible to get those straight with silk)

Now I am onto the fuse. The problem is that because of the curved cross section there are no obvious edges/corners to trim to, and nowhere to hide the trim seams. I figured I could minimize the problem by doing it in halves, with the only seams being along the centre line stringer on the top and the bottom.
Sure enough one piece of silk was able to conform to the entire fuse on one side from nose to tail But now I am stuck with how to do a nice straight trim, both on the first side and then on the next.

Worst case I will just use scissors, and put a trim stripe over the resulting slightly ugly seam. But I am wondering if there is some trick I am missing?

It goes without saying, that there will be no colour applied on top of this, only clear. So no way to hide anything with the finish.

Thanks,

Pat MacKenzie

P.S. the model is a Value Planes Cloud Walker 65.
65" span, bigger than it looks in the pictures.
Sort of a "modern" Old Timer if that makes any sense.

[Paul Wescott]

Hi Pat.  Silk is a bit beyond where my skills are at.  But I stumbled across and read this guy’s page years ago and it seems to be about the best treatise on the subject one can find.  Let me know if it helps:

https://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/finishing_techniques/silk_a_wing/index.htm

Paul W.

[Lauri Malila]

Hello Pat.

I've covered a lot with silk, but only wings. and never over Mylar. Your fuselage is for sure more difficult to cover than those.
But to me it looks like you're taking a too big bite when trying to cover the hole fuselage with just 2 pieces, but maybe with Mylar it's a more realistic plan.
Personally, I'd go with 4 strips. it's possible to have a nice, almost invisible seam over one of fuselage stringers. The silk doesn't have to overlap more. You can, for example, mask the underlaying covering next to stringer with low-tack masking tape, or a row of Post-It's if you want.
after a couple of coats of dope it's easy to crack the masking tape off from base, and trim the edge of silk accurately along the edge of stringer, with a sharp razor blade.
Also, with 4 strips of silk it's easier to make your working sequence more symmetrical, to reduce warping.

Cheers, Lauri

[pmackenzie]

Paul - Good article, I read that one before starting on the wings.
Covering the model in Mylar first made the silking part go pretty easy.
You can get it as wet as you want without worrying about affecting the wood, and take all the time you want to get it smoothed out and adjust things to get the weave straight.
The wetter it is the easier it is to move around, as it gets less wet the surface tension makes it stick to the Mylar. The first coat of thin dope attaches it to the Mylar. It blushes like crazy due to the moisture, but the blushing disappears with the second coat.

Lauri - I was thinking of the tape idea, I might go with that. Perhaps two layers, so that I don't have to worry about going through with the knife.
The underlying Mylar, in theory at least, results in a lighter and stronger finish.
I say in theory, because they say the same thing about tissue over Mylar being lighter, but in my experience it basically adds the weight of the Mylar.
I think with Silk it could be better than that, because it will take less dope to seal it. It is sealed right from the first coat, additional coats are only needed to get the shine you want.
Besides the increased toughness from the Mylar, it also seems to control the shrinkage so things are far less likely to warp.
But that fuse is extremely stiff, just about zero chance of that.
A least I hope so, the one side was done last night and the other side won't be done till today

Pat

[FLOYD CARTER]

With wet silk, you can stretch the silk over extremely curved surfaces.  I once covered the planked (round) fuselage of a Megow Ranger free flight with two pieces of dyed silk.

[pmackenzie]

Just an update - the tape trick worked well, it would have been even better had I used it from the beginning.
Because of that, the seam is still a bit ugly, but I think I can live with it ( and a few other flaws).
Next silk job will be better, which was in a way the point of the exercise.

Basically I doped the silk right over the tape, but not past it. Once dry it was easy to  peel it up from the far edge and fold it back. Then the knife can be run along the fold.
Where the fuse was really curved near the nose the tape was cut into shorter segment to allow it to be bent back.

Looks "good from far, but far from good".

Still more clear coats to go, particularly the wing which will get more translucent. Trying to decide on some additional tissue trim before I add more dope.

Taking a break from the dope fumes today to work on the equipment install.

edit - it looks small in the picture. It is actually a pretty big model, 65" wing span

[pmackenzie]

The tape folded up 90 degrees. I actually found it easier folded back even more.