The amount of time that can be spent talking about a subject on the evening is very limited, so I thought that a series of follow up articles might not go amiss, it’ll help take up space in the newsletter, so it’ll keep Bernie happy too.

Tissue and Nylon covering are both ‘traditional’ methods, being used since just after the Second World War. Before that, silk was used, tautened by rubbing some sort of oil into it – the lucky ones who could lay their hands on the dope used for full size aircraft did so, and were very popular in their local club!

To start with Tissue covering, I have developed my method over a number of years, and it is only the right method because it works for me, some one else will more than likely have a subtly different method to use it. My way is a good starting point for your own voyage of discovery…

Before you start, make sure that where you are going to do your ‘doping’ is well ventilated – the fumes given off are quite intoxicating! (aeromodellers were into solvent abuse long before Government got worried).

As with any covering, the surface must be as smooth as you can get it, the longer you spend doing the finish sanding the better the final product. For sanding, get hold of several different grades of sandpaper, I use 80 grit for roughing out, 120 grit for getting the shape nearly there and 320 grit for final smoothing. I don’t use wet & dry for this stage, you can’t use it wet, so it clogs as quickly as cheaper sandpaper. Don’t be afraid to fill minor ‘dings’ in the surface, using a polyfilla type product – if it’s a big ding, cut and fill with more wood – it’s stronger and lighter! The master plan is to use no filler at all, but I’ve not achieved it yet! Ensure that any foam is sealed so that it cannot be affected by the cellulose.

I use screw-topped jars to store the thinned, ready to use, sanding sealer / dope / banana oil, so I know the tins are full strength. My doping brush is years old and as stiff as a board! I have driven a nail into the side of it so that I can hang the brush in the dope jar without the bristles touching the bottom of the jar and splaying out as the brush softens in the liquid.

Once the surface is as smooth as you feel you can get it, put two coats of thinned ‘Sanding sealer’, this is a non – shrinking Cellulose dope, with a Talcum powder-like filler in suspension. Sanding after each one is dry to the touch. I normally thin this out 50/50 with Cellulose thinner, bought by the gallon from my local car accessory shop. The small tins are ok, but it’s cheaper by the gallon. The only time I don’t thin these initial coats out is when I’m applying them to a veneered, foam wing, I don’t want it to soak in too far and dissolve the foam! (Yes I found out the hard way!)

The two coats, lightly sanded after each is dry to the touch, will seal the grain sufficiently for the main event – Tissueing! I use the same method as when film / ‘tex covering to decide how many pieces of tissue I will need to cover an item. I.e. four pieces for a wing, (top & bottom, each side) and about six for a fuselage. (Both sides, rear underside, front underside, rear top & front top) Cut the pieces slightly oversize and then get them wet – I use a plant spray to lightly dampen the tissue. Lay the damp tissue on the item and then brush thinned (50/50) shrinking dope through the tissue, onto the wood. This will stick the tissue down, and ‘shrink-fit’ to the job. Smooth out any wrinkles as you go, make small cuts as necessary to negotiate corners or humps. Cut the overhang to about 3mm, (1/8th inch to you pre-decimal people) and then fold around and stick down. It’s always a good idea to cover an item symmetrically, to prevent the shrinking action pulling a warp into your lovingly prepared aileron, for instance. If it is a very light structure (not the sort of thing we normally use) pin the covered item down onto a flat surface as soon as the dope it dry to the touch.

Once this coat is dry, a white ‘bloom’ will be evident – don’t panic! This will disappear when you put on the next coat of thinned dope. Sand lightly once this coat is dry (every coat will ‘raise the grain’ slightly) and then get the last product out – ‘Banana oil’. This is a non-shrinking dope, without the sanding sealer suspended filler, but with a plastisiser added – normal shrinking dope can be used if you can’t get hold of Banana oil. Just add about a teaspoon of Castor oil to a pint of shrinking dope – hey presto! Non shrinking, plastisised dope. Just keep on apply coats of Banana oil, sanding after each coat is dry, until you get the shine you’ve always wanted.

Nylon covering is the same, except it will take longer to fill the weave, and I dunk the piece of nylon into warm water, then immediately squeeze out the excess, prior to applying to the structure.

If you intend applying a painted finish of any sort, allow the dope to finish ‘gassing off’ (the smell to disappear completely) before painting. The last thing you want is for the paint to suffer an allergic reaction!

That’s all there is to it folks, next time Glass cloth and Resin (if you can cover with nylon and dope, you can cover with glass & resin.)

Tom Gaskin