Model coverings

[DaveyP]

After much thought I've decided to build 2 aircraft over the winter months, the first one is a Vic Smeed "Madcap" which will be 2 channel radio assist and a 4 ch trainer.

I'm going to build the Madcap first as I haven't built anything for many years and it looks like the type of aircraft I used to build.

The question is what to cover it with, I've only ever used tissue and dope in the past.

I read the article in Rcme but, to me it was a bit vague and too general, I don't know yet what the Madcap will weigh but it should be quite light, it will have a Merlin 0.75cc diesel for power 

Any suggestions welcome.

Edited By DaveyP on 13/12/2016 16:02:53

[Martyn K]

No reason why you shouldn't stick to dope and tissue again - especially for the Madcap. There are other modern alternatives, but the trick is to keep it light.

If you want to use film then I would suggest something like World Models 'Light Tex' which is light and a dream to apply. The shrinkage can be a bit too much for lightweight airframes though so be careful

Good luck

Martyn

[Engine Doctor]

Try lightspan by Solarlac . It's proof against glow and diesel fuel and a lot stronger than tissue .

[John Muir]

If you do use film, which is a lot more resistant to punctures than tissue, I'd suggest doping some lightweight tissue over the top to add some rigidity to the structure. Lightweight film is great but these old designs relied on the doped tissue for some strength and resistance to twists. I built a Mini Robot a while back and managed to fold the wings when they were covered in Lightspan. They feel much more solid with a layer of tissue as well. Obviously adds weight but it didn't seem to make any difference in flight. I believe the best covering for this type of plane is tissue over mylar, which is a very lightweight film, but I've no experience of that myself.

John.

[Peter Christy]

Ah! The old Mini-Robot wing folding syndrome! My original did that, back in 1965, despite being covered in tissue! When I built a new one last year (from my original plans), I substituted spruce for the balsa spars. So far its proven very resilient, despite being film covered. And it has no problem with the extra weight, if indeed there is much!

--

Pete

[ken anderson.]

hello Davey-when I re-joined the defying gravity club..i had come from the time when tissue and dope was the norm. The LMS owner showed me the film coverings which were in use and still are and I was amazed ....have a go with film's etc..you'll be impressed with the finish you can achieve in a couple of min's...

ken Anderson...ne...1 .film dept.

[Mike T]

Folding wings have little or nothing to do with the covering and everything to do with the structure (specifically the spars/joiners) underneath!

If you want the doped tissue look on a Madcap-sized model, then try Litespan (matt side out). You get all the benefits of film, plus a coat or two of thinned dope will give it a satin sheen and stiffen it up considerably.

[Engine Doctor]

Some suggestions for using film but be careful as some of them are not proof against diesel fuel . Re litespan and wings folding ! I don't understand the connection as it the structure that gives the wings their strength. Yes the covering helps to stiffen the wings against twisting but doesn't stop wings folding that's all to do with the construction. Litespan is IMO superior to tissue but needs to be fitted properly . It has no adhesive so adhesive has to be applied to the airframe wherever it touches . Once the litespan has been shrunk then an iron applied to the frame stiffens the whole structure. Tip if you decide to use litespan is to use solarlac Clear coat as an adhesive. Good luck and enjoy the Merlin they are great little engines.

Edited By Engine Doctor on 13/12/2016 17:52:36

[David Davis]

This is my Veron Cardinal, Mills 75 up, covered in blue and cream lightspan. I hope to maiden it tomorrow.

[DaveyP]

Thanks for the replies, looks like Litespan / Solarlac is the popular choice, I guess it is readily available from most model stores. Will I need a special iron to fix and shrink it ?

David, your Cardinal looks great, hope the maiden flight goes well. I like the logo on the wing 

 

Edited By DaveyP on 13/12/2016 18:10:17

[David Davis]

Davey, the trick with using Lightspan is to get the covering as tight as possible before shrinking it. I use a purpose-built iron but in the past used a travel iron.

If you were to use a conventional film like Profilm or Solarfilm, you would find the covering process easier because the glue is part of the film, it doesn't have to be applied to the airframe. However, most films are too shiney and do not look authentic.

I would recommend it for your four-channel trainer mind.

[John Muir]

Oh dear, maybe it was the consecutive loops that did it for my Mini Robot then. Still feels a lot stiffer with the tissue on. I tried dope only but it still felt a bit flexible, maybe should have tried another coat or two.

At least this one flew. My first Mini Robot, built when I was very young, was covered in doped nylon and finished with humbrol enamels and fuel proofer. Powered by a DC Bantam it sagged gently to the ground after about twenty or thirty feet. Seemed pretty tough though.

John.

[John Muir]

This is my Mini Robot before stupidity induced structural failure. The wings are lightspan, the fuselage and tail are lightweight modelspan.

[Allan Bennett]

When I started converting all my models to electric, I experimented with LiteSpan on one model, but didn't like it because of the extra work in gluing, plus it didn't shrink so much as the SolarFilm I was used to. Then I found SoLite, which is basically the same as SolarFilm, but less than half its weight, and lighter even than Litespan.

[NormB]

When using Litespan or Fibafilm, I use the method suggested by Peter Rake:

tape the panel to a flat surface, shiny side down, apply a thin coat of BalsaLoc or equivalent to the whole surface using a sponge brush or similar. I usually apply a little thinned adhesive to the frame in a few key areas as well to make sure. Allow to dry and iron on like a 'normal' film covering..The added weight of 'unused' adhesive is very small, IMO negligible .

Litespan and Fibafilm , being based on a synthetic tissue, won't stretch around compound curves like for example Solarfilm ( Well, I can't get them to anyway )

Get yourself a Coverite iron thermometer too - doesn't cost much and it'll save you overheating the film during shrinking and so minimise slackening problems later.

Norm

[PatMc]

From experience :

Litespan is more puncture resistant than tissue but not a lot more & IMO it's useless in any airframe that relies on the covering material for stiffening such as the Madcap. Litespan can be stiffened using a coat of dope but it then becomes slightly brittle & loses much of it's puncture resistance making it virtualy the same as doped tissue in this respect.
Airspan would be more suitable having about the same puncture resistance as undoped Litespan after the required coat of dope it is stiffer than Litespan (See Solarfilm product info http://solarfilm.co.uk/ ) without losing the puncture resistance quality.
Fibafilm is another issue lookalike to consider & IMO the most suitable overall. It's heavier than both of the above but very much stiffer & puncture resistant than either. On a model the size of the Madcap the weight increase would only be around 15 grams. On the down side I think it's more expensive & not stocked by many model shops.

These three products require the airframe to have an adhesive applied, Balsaloc is the recommended adhesive.
They all have less heat shrink properties than Solarfilm etc making compound curve covering difficult though this shouldn't be a problem with the Madcap.

I've also tried doped tissue over mylar on a KK Chief glider using Balsaloc as the adhesive for the mylar. It looked fine but the covering tended to come away from the undercamber after a while & needs ironing along the ribs to reactivate the Balsaloc.

I have two or three vintage model in my build schedule that I would like to finish with at least the appearance of doped tissue but don't fancy any of the above methods. I've read about using tissue over laminating film & been impressed by photos of the results [particularly those of George Stringwell]
A few months ago I decided to cover a redundant tailplane from a large glider with laminating film & tissue using Rustins Floor Coating clear acrylic instead of dope on the tissue. The result was encouraging & I intend using the same method but with water based clear satin varnish when I cover a Graupner Amigo II glider that's currently being built.

The Chief covered with doped tissue over mylar.

Laminating film before applying tissue.

 

Tissue on, elevator was later fitted, hinged using Blenderm tape.

Edited By PatMc on 13/12/2016 23:15:49

[ken anderson.]

Davey............... I started of with her indoors iron...... ok for the job...... then got a purpose made hobby one after a couple of years....

ken Anderson...ne....1...... ironing dept.

[Peter Christy]

John, my Mini-Robot:

The wings on my first one folded when the sequential escapement skipped to left instead of right! I held it on for about 1 1/2 turns of a spiral dive, until I realised what had happened! When I released the button, it snapped out of the dive, and the wings promptly folded!

This one is flying well, with similar equipment and engine, but I made it with spruce spars. Much stronger!

--

Pete

[John Muir]

Brilliant Peter. I still have the Futaba radio and Elmic Conquest escapement from my original but I didn't have the nerve to try single channel. The new one does get flown around without touching the elevator much though, so nearly I suppose.

[Engine Doctor]

Posted by NormB on 13/12/2016 22:07:42

 

Litespan and Fibafilm , being based on a synthetic tissue, won't stretch around compound curves like for example Solarfilm ( Well, I can't get them to anyway )

Get yourself a Coverite iron thermometer too - doesn't cost much and it'll save you overheating the film during shrinking and so minimise slackening problems later.

Norm

They stretch around compound curves very well with a hot air gun . Make sure you leave enough spare covering to get a good hold of while pulling around curves or wing tips. Re slacking problems : The problems usually occur if the film is applied too slack. Tack it and get it as tight as you can before ironing down the edges firmly then shrinking with hot air gun. Also note that Litespan or fiberfilm has a grain that needs to go along the wing or fuselage and not across it. Fitted this way it will last for years . No dope is needed to keep it tight, infact dope will make it brittle and can also be badly affected by diesel fuel. Fix , seal edges and glue down overlaps with Clearcoat it's far stronger IMO than basaloc.

 

Edited By Engine Doctor on 14/12/2016 23:56:42

[Mike T]

I can't say I've noticed that doped Litespan is any more puncture prone than undoped and I've not used it with diesel so can't comment on the effect of it. If you wanted the 'doped' finish without the dope, then apply it shiny side out.