Covering and Coverings

 First off, my standard disclaimer:  I am still a “wannabe fast” pylon racer.   I have not completely figured it out so take my words with caution.  I can only claim to be mediocre.

 There are numerous types of coverings to chose from out there besides Hal Garwood’s favorite – silk and dope.  The younger guys favor Monokote or Ultracote, something produced within the last century.  Below are my personal observations based on several years of using both (covering is one of my favorite phases of completing a model –honest).

 Monokote

• Has the highest gloss.
• Slightly more difficult to work  with compared to Ultracote – less forgiving – but results in a better finish..
• Better selection of metallics. 
• Must be applied with a higher heat. 
• Seems to withstand heat variations (cool nights/hot days) with less bubbles forming However, when and if bubbles appear, it is more difficult to get rid of them compared to Ultracote. 
• Easier to cut a final edge (after covering has been applied to the model).
• Harder to cut out detailed designs.
• More brittle than Ultracote.  Metallics are most brittle, followed by transparents.  Regular colors are slightly more brittle than Ultracote.

 Ultracote

• Same as Oracover (the old high temp version of Oracover – the new Oracover is a low temp covering that I have not tried yet)
• Seems thicker than Monokote.  Overlapped seams are more visible.
• Less glossy (but acceptable – I normally only use Monokote on pattern planes)
• Easy to work  with – more shrinkable and stretchable than Monokote (but see next comment)
• Must be careful not to use too much heat (just slightly less than Monokote).  If too much heat is used, it can shrink excessively, pulling edges apart and exposing balsa (such as at the LE and especially at the wing tips.)
• Bubbles severely over time – but easily removed with iron.
• Best selection of fluorescents.
• Very difficult to cut a final edge – ensure you have a super-duper sharp razor blade or your final cuts, such as along the corners of the fuse, will look more like tears.  This could possibly drive one to drinking.  NOTE: The cheap razor blades sold at Harbor Freight and Tool King DO NOT hold an edge for more than ONE cut.  The Stanely razor blades sold at Home Depot are far superior – it took me years to figure this out.
• More elastic than Monokote – probably the reason for the difficulty in cutting with a dull blade.
• Great for cutting out detailed designs thanks to the white paper backing versus the clear vinyl backing on Monokote.  Very easy to draw directly on the backing, just remember you have to draw it backwards!
• Difficult to use as pin-striping because of its shrinking characteristics.  You cannot go over everything with a hot iron to seal the edges – the edges shrink, resulting in wavy pin-striping.
• Ultracote Plus has a sticky backing.  It is no longer being made (I think). I’ve used it several times and found no advantage. Only disadvantages.  The sticky backing seems to make the covering even thicker and overlap seams are more noticeable than normal.  It can also be very deceiving.  You think the covering is stuck down over the entire surface, only to find out a day later that it isn’t.  I’ve had the entire top side of a V-tail completely come off in flight.  I won’t use it again. 

TIPS

• Pin-striping – I cut my own pin-striping and prefer Monokote.  Caution must be taken when using Ultracote.  It distorts very easily and makes straight line pin-striping very difficult.
• I mix Ultracote and Monokote all the time.  I keep track which is which to make sure I don’t overheat the Ultracote.
• I press very very hard on solid surfaces and work from the center out.  Think “squeegee” not “iron.”  In fact, I push so hard I get a blister on my thumb – I now wear one of my old racquetball gloves.
• Since I push so hard, I have to use iron socks.  But be careful with cloth iron socks.  Sometimes the seam can find its way to the bottom of the iron and can leave a big indentation on a balsa surface – arrrrgghhhh!.
• I have two irons turned on during covering.  One with a cloth sock, and one without.
• I rarely, if ever, use my trim iron.
• When you are wrestling with wrinkles, such as around wing tips, “stretch” don’t shrink.  Make sure you have enough overlap to grab onto.  Heat the covering up and stretch BEFORE you wrap it around the curved surface – just like you would do with saran wrap.  Sometimes I lift and stretch (sounds like Hal Garwood at the gym) several times before most of the wrinkles are out.
• Instead of using an X-acto blade to cut out holes, edges around the engine compartment, servo boxes, etc, I use a red-hot pin or piece of thin music wire heated up with a lighter and held in a small pair of vise-grips.  I simply run the hot pin along the edge – not only does this cut the covering, but if angled correctly, it also seals the edges.
• Once the control surfaces are permanently attached, I use a ½” strip of covering to seal the hinge gaps.
• I use a paper towel with just a few drops of acetone on it to remove adhesive that has seeped out along seams.  If you use too much acetone, you’ll mar the finish.
• Even though coverings are advertised as opaque, they are not completely.  So just like painting, put the lighter colors on first, and then the darker colors.
• CA is a great field repair for when the corners of covering start to come up.
• Silver Monokote AND Ultracote are the worst!  Both bubble the most and don’t stick very well.  No solution to this one.

 Kurt Bozarth