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Covering With Japanese Tissue

[The following is an outline of a presentation I made to the  Phoenix Model Airplane Club in October, 1999]

Note: as modelers, we have all referred to our old favorite covering material as ‘jap’ tissue. While we had no disrespect in mind, people now suggest that its proper, less offensive name is ‘Japanese’ tissue. In this discussion, the term ‘tissue’ will normally be used.

Tools: new #11 xacto blade w/handle, broken ‘blue’ or throwaway razor blades CA’ed to 1/8" sq wood handles for trimming, embroidery scissors for trimming and relief cuts around edges, sanding block, long sanding block, 100 grit and finer alum oxide paper

Adhesives: clear ‘straight’ nitrate, nitrate plus Ambroid, ‘Super Seam / seam cement’ used in covering of full sized fabric planes, thin white glue

Shrinking: rubbing alcohol acts like ‘thin’ water, minimizes shrink induced warps - can spray again if there’s a wrinkle - and can still spray lightly with straight water for a bad wrinkle

Finishing:

~ recommended: non-tautening nitrate all the way - pulls up just right without warping light structures

~ butyrate - no redeeming qualities that i can find; poor adhesive for tissue; poor adhesion to inside corners; NOT really fuelproof; clouds tissue colors

~ spray clear krylon - useful for very light models; can also use lightly to stabilize tissue against humidity-induced warping for indoor or NOCAL models

~ fuel proofer - for low nitro fuels [prob up to 15-20%], can use Ace Hardware spray gloss urethane varnish - for high nitro, use clear spray epoxy paint; HobbyPoxy is still available, tho K&B seems to have gone away

 

Favorite material: modern Esaki tissue - like ‘pre-war’; one shiny side, one dull side

•Preparation:

-sanding - long board [10"-12" is about right] sanding is essential for blending of contours

-scalloping formers - designate perimeter formers at ends or where the contour changes - in between, scallop the formers to get smooth, dirigible-like gores - looks better and will have slightly less drag

-priming of wood with ‘stickum’ + sanding again - nitrate based materials are best for this - use 2-3 coats - sand away the raised wood ‘fuzz’ between coats - apply to all perimeters [plus all body stringers if dry covering will be used] ;if white glue is used, grain is raised but can’t be sanded, so covering will be rough wherever it’s attached

-for indoor or NOCAL, can pre-shrink tissue on a frame - to avoid warps; can also cover with ‘crushed’ tissue, but it’s difficult to appreciate the pebbly appearance

•Covering:

-Dry:

~grain - good tissue will tear nicely along the grain; for best appearance and minimal sag, apply tissue with grain parallel to longest dimension

~where to begin: on the bottom of all parts; makes overlaps point down - will be least obvious

~stick with thinner [I have poor luck with this method, believing that dope has become less sticky through the years - but a recommendation heard during the presentation was to try acetone instead; it’s considered a ‘hot’, fast evaporating solvent], dope or dope plus Ambroid, seam cement

~for stringered bodies, plan to cover one or two gores at a time [gore= 2 stringers plus the end edges]; this can be tedious, but you can alternate sides while pieces dry; trim the next gore tissue by lightly marking with a pencil and then cutting to shape

~trimming edges and overlaps - through habit, I overlap leading edge tissue about 1/8", curved edges about 1/16", and trailing edges not at all; the result is minimizing bare wood on the model; exacto blade is used for the overlap trimming and the tiny scissors is used to make relief cuts every 1/8"-1" [depends on the shape - tight curves get close cuts]; overlaps are stuck down with dope; trailing edge trimming is done with a sanding block, applied at an angle of 30o-45o

 

-Wet

~priming/preparation is same as dry

~cut a piece of tissue larger than usual, lay across your knee or a towel, spray with water or rubbing alcohol, pick up the tissue and lay it on the surface to be covered

~pick up edges and rearrange as needed to get rid of wrinkles - can respray as needed

~stick with thinner, dope or dope plus Ambroid

~trimming edges - trimming works better after the tissue has dried

~overlaps - same as dry method

 

•Finishing:

-shrinking: hair spray or grocery store bottle; rubbing alcohol vs ‘straight’ water

-doping

~clear; non-tautening vs regular; non-tautening is recommended - it pulls up OK and doesn’t produce many warps

~nitrate vs butyrate [as discussed above]

~thin 50/50; brushing is OK as brush marks don’t show much on tissue

-trim with tissue

~how to cut; draw/print markings on bond paper; tape tissue down to thin card board, tape bond paper over that, paper stabilizes the tissue allowing fairly easy cutting - guide with straight-edge when possible, freehand otherwise -use fairly shallow angle of xacto blade [20o or so] as it helps guide the cut and minimize jaged edges; attach with light application of thinner on top of doped tissue base - add a couple of coats of dope

~inkjet printed tissue - inkjet ink is NOT waterproof, but it can be attached with thinner just like cut-out tissue trim; minimize heavy fill-ins of color or black as it will pucker the tissue - use a ‘draft’ print setting for even lighter ink; should also minimize the size of printed stuff as the decoration may be difficult to stick onto the contours of a rib/spar joint

~need a light color over dark? use white [actually a pearly white] micafilm base, then add tissue over that

-print decorations on clear sticky-back - can get intense colors; must spray with clear Krylon or fuel proofer as the ink is not waterproof; same size/contour considerations as printed tissue

-trim with vinyl stick-on letters or stripes

-trim with spray enamel - clear doped tissue is great base for color dope or paint; over sheet or block balsa doped tissue acts like 3-5 coats of wood filler

•Repairs:

-patching or recovering; cut back to nearest sticks or ribs, patch with an overlap of at least 1/16"

-complications due to existing epoxy or varnish fuel proofer finish - dopes pucker varnish or epoxy when applied, but thin white glue will stick OK for patching; shrink and dope carefully

-removing tissue

~sanding

~solvents - use paper towel scraps to hold thinner on wood to be uncovered; 20- 30 seconds should allow peeling tissue away

-field tears - apply Ambroid or Duco to tears, cover with Saran Wrap or lunch bag plastic; poke Saran Wrap into the glue smear, then pull around the edges to get repair up to the original contour; wait an hour, remove Saran Wrap

•Sources:

Campbell Model Supply [not the same as Campbell’s Custom Kit company], 37742 Carson St., Farmington Hills, MI 48331; 248-478-7846 Esaki genuine Japanese tissue, plastic props plus some kits. 

Peck-Polymers, Japanese and domestic tissue

Library of Paints, 1102 W. Madison, Phoenix, AZ 85007; 602-252-1785 & 602-252-2321: [this is an auto paint store but they carry aircraft dope products] clear nitrate and butyrate dope in non-tautening and regular, by the gallon with empty quart/pint cans also available for sharing/repackaging; ask for their recommendations on thinner. Thinner use varies with the application and the temperature - hardware store thinner dries fast but produces little gloss. High gloss thinner is referred to as ‘slow’, allowing the dope to flow out better. Check out the blue 3M 1/8" or 1/4" narrow masking tape - really great for masking for painted model trim; about $6-$7 a roll, but worth it!. EAA homebuilder folks buy here; the staff even knows what you’re talking about! You should be able to find a source like this closer to where you live - check the telephone book, and look around at small airports.

SIG, pint cans of nitrate, but watch out for this product - it turns out to be non-tautening! That's what I use on Japanese tissue for stick&tissue models but it will not work on silk - says so right on the can in very fine print.

Other Materials:

•Craft tissue; hobby shop type, many colors, used for paper flowers; very cheap [1/10th price of good tissue], NOT colorfast, but can still be shrunk - use an airbrush to spray a light fog of water vapor

•Domestic tissue; sold by Peck; colorfast version of craft tissue, many colors, darker colors tend to be splotchy, heavier than Japanese tissue, takes more dope, difficult to use wet, retails at about 1/3 the price of ‘real’ tissue

•Hallmark giftwrap tissue - has been recommended as a model covering material