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How to Silk a Model Airplane Wing

May 05, 2015



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Back to Silking a Wing

 

Airfield Models (http://www.airfieldmodels.com/)Applying Silk to a Model Aircraft Wing

Before you get here you must have prepared and sealed the wing.

The ultimate goal is to get the silk on the wing exactly as you want it before it's doped in place.  Do not apply dope to any portion of the silk until you are absolutely satisfied with it.

If the wing is fairly flexible without covering then take care not to warp the wing as the silk is tautened.  Wings that are more rigid can warp but it's not likely.

You get unlimited do-overs.  If you can't get the silk right and become frustrated then remove the silk and come back to it later.

Keep your work area and hands clean so the silk doesn't get stained or the weave messed up from picking wood chips or other crud.  Silk is a natural fiber that is very absorbent and will soak up just about anything including oils and dirt from your skin.

 
 

Tools and Supplies Needed

  • Silk.

  • A spray bottle filled with fresh, clean water.

  • Sharp scissors.

    A rotary cutter works well for initially cutting the silk but scissors are necessary for coarse trimming after the silk is in place.

  • Patience.

  • A helper if available and willing.

While a spray bottle works it can be a little difficult to control the water application.  I found that using it to mist water from a few feet above the wing allowed a little better control.

When silking this wing I used my spray gun filled with water and set my air compressor to about 8 PSI.  My spray gun puts out a much finer mist than a spray bottle.

Another option is to wet the silk in the sink under running water.  What that does is give you a wad of silk that's a real pain to get unwadded.  It's also harder to control the moisture content of the silk.  It will be too wet until you squeeze it out and then it tends to be too dry.

Best is to put the silk on the wing dry and then wet it.

 
 

Apply Silk to the Wing

The wing fairing is silked in advance. I could not think of a way to apply silk to the top and bottom of the wing in a manner that would not leave exposed wood somewhere on the fairing at the trailing edge.

I decided it would be best to cover the fairing in advance and then allow the other pieces of silk to overlap it.

After it was initially doped in place I applied two more brushed coats.  When they were dry I feathered the silk into the trailing edge using a sanding block with fine paper.

Begin by placing the dry silk on the wing and aligning the weave. Apply silk to the bottom of the wing first.

Many wings may require separate pieces of silk on each half of the wing instead of a single piece.  If that's the case then the silk should overlap at the center of the wing by approximately one inch.

If the wing has several degrees of dihedral then you may be able to silk the bottom with one piece.  The top may require two pieces.

Be sure to cut the silk with the grain correctly aligned.  Silk has very subtle finished edges.  The weave of the silk should run with finished edges parallel to the span.

Cut the silk about 3" longer than the span and chord.  That gives you 1-1/2" all the way around to work.  When the silk is wet you will have even more to work with because the silk will stretch quite a bit.

Take the time to align the silk so the weave isn't skewed to the wing.  The weave is very visible in the finished product.

The silk won't stay in place when it's dry but do take the time to stretch it out as much as possible.  Don't worry that it pulls back to its center.

Wet the silk at one tip and stretch it taut. If using a single piece of silk then begin by wetting the silk at one tip to the point that it strongly clings to the wing.

If using two pieces then start at the center of the wing.  Only apply one piece of silk at a time.  Don't apply the second piece until the first piece is doped in place.

Pull the silk across the chord and around the tip.  Work out all the large wrinkles and puckers.

If the silk becomes so dry that it won't stay in place then wet it again.

Ensure the weave remains aligned.

This isn't a difficult task but it is much easier if you have a helper.

It should be evident why the wing needs to be sealed well before the silk is applied.

Stretch the silk then wet and tauten the opposite tip. Any time you are stretching the silk taut, pay attention to the weave that is 90 to the direction you are stretching.

In other words, if you are pulling across the chord then the span-wise weave will tell you if you need to pull from the leading edge or the trailing edge.  If you pull from the wrong edge you'll end up with serpentine weave.  As I said, it's visible in the final product so take your time.

Now pull the silk taut along the span.  Then wet the opposite tip.

Work out the silk as you did with the first tip.  Pull across the chord and work the silk around the tip removing wrinkles.

The silk at this tip is too oversize and difficult to work with.  I trimmed off the excess to make it easier to work with.  Wet silk cuts nicely with scissors.

Wet the center and tauten to each tip. Now wet the center and pull it taut.  Check that the chord-wise weave in the center is straight from front to back.

From here on you will be working the fabric from the center to each tip, not from tip to tip.

If the silk is really messed up you can remove it and try again.  You may want to allow it to completely dry before reapplying it but you don't have to.

Wet the entire wing and continue stretching the silk. Now wet any areas of the silk that are still dry.

Continue stretching across the chord and then along the span.

If you pull across the chord last then the covering will sag more than if you pull the span last.

Silk on one half of the wing fully tautened. One half of the wing is as good as it gets.
The silk is ready to dope to the wing. And now the wing is ready to have the silk permanently attached with dope.
 
 

Inspecting the Silk

I can not emphasize strongly enough not to apply dope until the silk is right.

What to inspect:

  • Ensure the weave is correctly aligned

    If the weave is wrong then it's almost impossible to fix without removing the silk and starting over.  If the wing is fairly rigid on its own then you can leave the silk misaligned if it doesn't bother you.  If the wing is very flexible then the misaligned silk may warp the wing as it shrinks, especially if the silk on the opposite side of the wing isn't aligned with the first piece of silk.

    When I say misaligned I mean that the average direction of the weave is askew to the wing.  I've never been able to apply silk with the weave dead perfect.  I don't think that's even a realistic goal.

  • Sight the wing from the front across each rib.

    If you see even tiny wrinkles then pull the silk across the chord to remove them.  If you see the silk sag more between ribs then stretch across the span and inspect again.  If the wrinkles were really tiny then you probably don't need to stretch the silk across the span.

  • View the tip from many angles.

    It may look perfect from where you are standing, but another viewpoint may reveal a pucker.  Dope does not shrink out puckers.  In fact, they become worse so take them out before using dope.

  • Ensure the silk is still clinging to the wing around the entire perimeter.

 
 

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Sealing Balsa Wood in Preparation for Silk
Doping Silk to a Model Aircraft Wing

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Copyright 2009 Paul K. Johnson