Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
July 18, 2018, 04:52:59 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1]   Go Down
Print
Author Topic: Mylar covering 10 microns hints and tips please  (Read 1120 times)
0 Members and 1 Guest are viewing this topic.
dieterperiperi
Silver Member
****

Kudos: 7
Offline Offline

United Kingdom United Kingdom

Posts: 118


Topic starter


Ignore
« on: August 03, 2017, 04:29:15 AM »

Hi all

I have taken delivery of some 10micron Mylar covering clear and a bottle ofbalsa lock adhesive recently. I plan to build a small model (maybe a 13-15" ws) And then later play around with adding some colour. I got the 10 micron stuff to retain some strenth. Didnt want it to tear too easily. And 10micron is a similar weight to esaki lite flite

I fly outdoor most of the time which is why I wanted to try Mylar as it doesnt suffer like tissue from moisture, but thought Id post here in indoor as you guys might be more likely to comment on small light sports/scale models

Ive also read about esaki over mylar as opposed to painting/airbrushing. This would surely add a lot of weight on a model but I would like to try this method

I got the balsa lock to perhaps heat seal it on to the parts as Ive read in some other forums?
Will it be nesecery to heat shrink the mylar after covering or should I aim to cover tight?
I also thought that if there was a slight warp in a wing that you could shrink the mylar in certain areas to remove the warp?

Any tips on covering with this Mylar would be welcomed

Thanks.

D
 
Logged
ffkiwi
Gold Member
*****

Kudos: 19
Offline Offline

New Zealand New Zealand

Posts: 439



Ignore
« Reply #1 on: August 03, 2017, 04:57:58 AM »

10um is way too heavy for the size of model you propose to cover-5um is more than adequate-and for models right up to P-30 size. I use 5, 10 and 15 um mylar in both clear and aluminised-the c lear when overcovering with tissue, the aluminised virtually exclusively for tailplanes. Balsaloc is not the best adhesive for attachment either-though very useful for some other types of covering. The best method for attaching mylar is using a thinned down contact adhesive-Evostik or Uhu since you're UK based...! Thin it down to about dope consistency. You normally apply it to all parts of the airframe that the mylar will contact, and iron on the mylar. That you have to do by trial and error-depending on the brand of your iron-the ideal being hot enough to activate the glue-but not hot enough to shrink the mylar. You do not have to attach it drum tight-but be aware that wrinkles can occur quite easily-and can be worked out with care-but try and avoid them in the first place. static can be a problem as the stuff acquires a static charge quite readily just with handling-and this can cause it to stick to itself rather than go where you want it.  You also want to use a brand new blade when cutting it.

Contrary to your expectations-tissue over mylar does not add a lot of weight-in fact-and there is good empirical evidence for this point-tissue over mylar is no heavier than the same structure covered with tissue alone. the reason behind this apparently illogical fact is that (i) the mylar layer is completely impervious-so no dope should enter the airframe structure itself, (ii) the evaporation is all outwards and (iii) the consistency of the dope used is generally thinner than used for tissue alone.

I have been using tissue over mylar for some 25+ years now-in fact it is my default covering method. It is slower though-than tissue alone-and you need good attention to detail-overlaps, treatment of compound curves on wingtips etc. It produces a much stronger 'composite' covering-which is waterproof, doesn't go slack in the damp (a real asset in the UK!) and allows you to get really creative with colour schemes. You can also go somewhat lighter in structure-as it doesn't exert that murderous tension on the structure  that tissue does.  It doesn't stop there either-silk or nylon over mylar are viable techniques-especially for vintage and large FF models.

A few cautions though: it is still possible to get warps as a result of the covering process-and in some cases these will return-but these are generally easily removed with heat. Also- over time-the stuff will creep-albeit very slowly-so it is a good idea to allow reasonable generous overlaps at TE and LE. Over a period of years you may find the mylar slackening slightly-so a quick run over with the iron will tauten it again. Patching is generally easier than with tissue-and with care (and a lot of practice!) the repair can be invisible to the eye... And finally-the aluminium is only on one side-which should be on the inside surface if you use the silver stuff-otherwise it will wear off in handling-and look a bit naff. The quick way to check which surface you have is to scrape it with a knife blade-the aluminium will scrape off-the elegant way is to use a multimeter set on the ohms or 'continuity' scale-the aluminised side is conductive obviously.....!

Undercambered airfoils require care-just as they do with tissue alone-and you need to be very thorough with applying the adhesive to the undercambered portion of the ribs-a slightly thicker glue mix may be appropriate in this instance [also applies to scale model fuselages if there are concave areas-and fillets may need care to ensure the mylar is well adhered and following the surface contour.

Finally-though people generally go 'like with like' for ToM, there is no obligatory reason you have to-so you could use lightweight tissue over heavier mylar, vice versa -or any other combination you deem appropriate for the airframe type and structure.

 ChrisM
 'ffkiwi'
Logged
Footloose
Bronze Member
***

Kudos: 1
Offline Offline

United Kingdom United Kingdom

Posts: 25



Ignore
« Reply #2 on: August 03, 2017, 02:31:50 PM »

The Evo Stick generally available in the UK is no good for this because it has been re-formulated and is now water based. The only alternative that I know is the 'No Nonsense' contact adhesive which can be found at Screwfix.

Bert
Logged
mkirda
Gold Member
*****

Kudos: 14
Offline Offline

United States United States

Posts: 657

WWW

Ignore
« Reply #3 on: August 03, 2017, 04:48:13 PM »

THere is 2um mylar available that would be suitable with BalsaLoc for adhesion. I used it on an indoor 54" wingspan model and would use it for lighter too.

10um is way overkill.

Regards.
Mike Kirda
Logged

Tapio Linkosalo
Platinum Member
******

Kudos: 28
Offline Offline

Finland Finland

Posts: 1,123



Ignore
« Reply #4 on: August 04, 2017, 03:34:30 AM »

There is another catch in thicker mylar - it shrinks and pulls structures quite strongly. I tried to cover one P-30 with that stuff, as with 5 micron mylar the wings were puhctured all the time. Even with carbon tube spars, the 10 micron mylar tends the warp the wings, and even worse, the wings may warp over time, so the mylar "lives" and settles over a period of time. I have recently started to use Oracover Air Indoor for P-30, E-36 and F1B & F1H tailplanes. Different material which seems to be more stable - when you tighten it, the shape and warps are then stable. It weights more than 5 micron mylar, but is much more puncture-proof.

Logged
vintagemike
Bronze Member
***

Kudos: 7
Offline Offline

United Kingdom United Kingdom

Posts: 91



Ignore
« Reply #5 on: August 04, 2017, 01:07:14 PM »

I use a Pritt stick to stick the mylar to the airframe, use a new one, they tend to go slimy after a while
Logged
ffkiwi
Gold Member
*****

Kudos: 19
Offline Offline

New Zealand New Zealand

Posts: 439



Ignore
« Reply #6 on: August 04, 2017, 08:00:53 PM »

There is another catch in thicker mylar - it shrinks and pulls structures quite strongly. I tried to cover one P-30 with that stuff, as with 5 micron mylar the wings were puhctured all the time. Even with carbon tube spars, the 10 micron mylar tends the warp the wings, and even worse, the wings may warp over time, so the mylar "lives" and settles over a period of time. I have recently started to use Oracover Air Indoor for P-30, E-36 and F1B & F1H tailplanes. Different material which seems to be more stable - when you tighten it, the shape and warps are then stable. It weights more than 5 micron mylar, but is much more puncture-proof.



Tapio I draw your attention to the final line in my post above  "......appropriate to the airframe type and structure...."    Implicit in that statement is the need for common sense when deciding on the covering regime......

Personally-I've never encountered the problem you describe-if anything-the exact opposite-the heavier the grade of mylar the LESS shrinkage it seems to have.... just for the record-I use 5 micron on coupes and P-30s and small open models, 10 micron on A2 and 1/2A tailplane-and small power model wings (1/2A and 09), 15 micron on big power model (.21 and up) tailplanes and 15 clear on some vintage power models that then get silk or nylon over the top.

ChrisM
'ffkiwi'
Logged
Flyguy
Gold Member
*****

Kudos: 35
Offline Offline

United States United States

Posts: 711




Ignore
« Reply #7 on: August 04, 2017, 08:50:29 PM »

That has sort of been my experience as well - the 5 micron consistently seems to shrink the most, I've also used 7.5 and 10 micron - sometimes the thicker ones have shrunk really tight, sometimes they haven't, so who knows. I like the 7.5 on P30 wings because it's more puncture proof; 10 is definitely overkill, unless you're flying around prickly bushes!

There are two rare problems that I've had with fairly extensive use of mylar, curious if others have had it as well. One is that it appears that you sometimes get 'bad' mylar, in that parts of it don't shrink at all or don't shrink correctly. I've learned that you can't ever get it smooth in that case, and so now I usually just redo it when that happens, the 'good' stuff (possibly from the same roll!) goes on nice and smooth. Another problem that's rare is that it doesn't keep the shrink, a week or two later the wrinkles creep back, you can reshrink them out but they come back again; I've had this happen on two planes. My guess is that maybe that mylar was an 'old' batch or was just defective?

In the vast majority of cases, you can shrink it dead smooth and it holds it for at least a few years. I have a few planes that are a few years old and the covering is still really tight and nice (whereas my old tissue jobs get little warps with moisture changes over time). Plus the wing remains dead flat and still has whatever wash-in or other trim I put in, so if I pull it out of the box after 9 months, it still flies great!

Logged
Tapio Linkosalo
Platinum Member
******

Kudos: 28
Offline Offline

Finland Finland

Posts: 1,123



Ignore
« Reply #8 on: August 05, 2017, 12:52:15 AM »

I guess the mylar properties vary for different brands. For the ones that I have, the 10 mil stuff shrinks heavily, while the 5 mil stuff is quite soft. But the latter punctures too easily. Never had any 7.5 mil mylar, where do you get that from?

FWIW, I covered too F1H tailplanes yesterday. Remembered yet another feature that I like with the Oracover Air Indoor. It shrinks with rather low heat, so I did not need to adjust the iron tamperature cooler for attaching and hotter for tightening, as is the case with mylar. Instead one setting was good for the whole process, and the outcome was nice and smooth.
Attached files Thumbnail(s):
Re: Mylar covering 10 microns hints and tips please
Logged
ffkiwi
Gold Member
*****

Kudos: 19
Offline Offline

New Zealand New Zealand

Posts: 439



Ignore
« Reply #9 on: August 05, 2017, 02:52:16 AM »

Nice looking covering Tapio-how colorfast is it? decades ago-in the early 80s-I used to colour clear mylar by using the felt carrier wadding from felt tip indelible pens soaked in dope thinners, filtered, then sprayed on the mylar with an airbrush. You had to remember to cover with the sprayed side innermost. It was great for a while but faded relatively soon in use-especially red, yellow and orange....black faded to a purple..then to an indigo..then to virtually nothing. Subsequently other people discovered you could dye mylar with fabric immersion dyes...
    I've not heard of Oracover Air indoor covering material before....'Oracover Light' yes-but not this stuff-I wonder how widely it is distributed. I think your comment about source is quite pertinent-I have several examples of 'light' aluminised mylar (nominally 5 micron)-which handle quite differently- some have a mirror finish, one is quite dull-and while it shrinks OK-it melts readily if you're a fraction slow with the iron. Other examples are striped, not continuous aluminium-which matches the rumoured origin of the material as used the manufacture of mylar capacitors.......

 ChrisM
 'ffkiwi'
Logged
Mike Thomas
Bronze Member
***

Kudos: 0
Online Online

Australia Australia

Posts: 65



Ignore
« Reply #10 on: August 05, 2017, 04:12:01 AM »

Tapio, Mike Woodhouse stocks 7.5 micron Mylar.
Logged
Pit
Palladium Member
********

Kudos: 125
Offline Offline

Germany Germany

Posts: 5,450


aka staubkorb


WWW

Ignore
« Reply #11 on: August 05, 2017, 08:05:17 AM »

The indoor rc people use ORACOVER Air Indoor mostly (it's marketed thru Horizon Hobbies) but can probably be ordered directly from Lanitz-Prena (the manufacturer and a very good acquaintance) in Germany.  It's good stuff with no adhesive - adhesive also available from Lanitz - and is definitely colorfast.  Other adhesives (thinned contact cement) probably also work.
Logged

A Dedicated Convert to:
WWWoFF (Wonderfull Wacky World of Free Flight)

Comparing Spammers to a pile of organic waste is an insult to the organic waste!
Tapio Linkosalo
Platinum Member
******

Kudos: 28
Offline Offline

Finland Finland

Posts: 1,123



Ignore
« Reply #12 on: August 05, 2017, 08:27:24 AM »

Tapio, Mike Woodhouse stocks 7.5 micron Mylar.

Ah, good to know. He did not before, but I'll have to get some to try on P-30. Where 5 micron is too light and 10 is too heavy.

The indoor rc people use ORACOVER Air Indoor mostly.

Also getting more popular in small outdoor FF models. Like my F1H tails (as above), P-30 and E-36 models.
Logged
Flyguy
Gold Member
*****

Kudos: 35
Offline Offline

United States United States

Posts: 711




Ignore
« Reply #13 on: August 05, 2017, 11:18:04 AM »

The 7.5 is perfect for P30 wings, I also use it for all my 30 something inch oldtimers, lots of flights with no damage. In addition to Mike, you can also get it from FAI model supply and Retro RC, it's also listed as 3/8 mil (or 1/3 mil is another that's close), both very good.
Logged
dieterperiperi
Silver Member
****

Kudos: 7
Offline Offline

United Kingdom United Kingdom

Posts: 118


Topic starter


Ignore
« Reply #14 on: August 05, 2017, 01:04:59 PM »

Great responce from everyone. Thanks to all
Should have asked the question first and then purchased (lesson learnt).

Will have a play around with the 10um ( Purchased from Mike Woodhouse) and get a feel for it.
It does state on a website that baslaloc(also from Mike)is used to adhere mylar. The replies here state differenly?

Just want to clear up one other thing please people. When its mentioned about covering the mylar with esaki, dope is used.
Smelly dope or Eze dope?
Logged
vintagemike
Bronze Member
***

Kudos: 7
Offline Offline

United Kingdom United Kingdom

Posts: 91



Ignore
« Reply #15 on: August 05, 2017, 01:23:30 PM »

I,ve always used thinned (75% thinners) smelly dope.
Logged
Buster11
Bronze Member
***

Kudos: 0
Offline Offline

United Kingdom United Kingdom

Posts: 79



Ignore
« Reply #16 on: August 05, 2017, 04:15:38 PM »

Further to Footloose's warning to avoid the Evostik now sold in the UK, I'd suggest that most contact cements that have an Inflammable warning on the tube would be worth trying, and should thin satisfactorily with dope thinners. It would be worth talking to a shoe repairer, too, as the stuff many of them use works well as a Mylar adhesive.
Logged
dieterperiperi
Silver Member
****

Kudos: 7
Offline Offline

United Kingdom United Kingdom

Posts: 118


Topic starter


Ignore
« Reply #17 on: September 15, 2017, 01:19:19 PM »

Hi all
Thought I'd post to let you know how I got on...the 10micron Mylar is quite easy to use. A bit fiddely when it picks up static but nothing major. Cuts easily with sharp scissors or knife. The 10micron stuff is very strong and will order 5 at some point. Wing tips are a bit of job and I never managed to all the creases out.
Balsaloc worked realy well for me to iron it on after painting it on to the balsa and dry for few minutes.
Will definately use this more often now.
Thanks for all your advice 
Attached files Thumbnail(s):
Re: Mylar covering 10 microns hints and tips please
Re: Mylar covering 10 microns hints and tips please
Logged
DerekMc
Platinum Member
******

Kudos: 51
Offline Offline

United States United States

Posts: 1,329



Ignore
« Reply #18 on: September 15, 2017, 01:24:45 PM »

Another option for mylar adhesive is Deluxe Materials Cover Grip. I've used it on small patch jobs and it has worked well so far.  It is water soluble and has a distinct odor according to my daughter but no where as bad as dope thinner etc.
Logged

They fly better when you smile!
Derek
aerotrope
Bronze Member
***

Kudos: 0
Offline Offline

Canada Canada

Posts: 15



Ignore
« Reply #19 on: March 14, 2018, 01:18:11 PM »

I've had good results using LePages water based contact cement, thinned 50%. I use the very cheapest sort of disposable brush or roll it on with a cotton swab, as even the slightest drying makes the brush uncleanable. Let it dry a few minutes; it will be slightly sticky, enough to position and reposition the mylar as smoothly as possible, then use a covering iron to first tack, then seal all around.
I mostly do ToM with 5 micron just on the bottoms of surfaces and fuselages to add puncture resistance.  It's also good for complex tissue colour schemes, as the tissue edges don't need to align with structure.
Logged
Pages: [1]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!