Building the Piper Super Cub 95 (Kit 602)

[Mfezi]

Steve, he has never intentionally broken anything, but of course at age 4 he does accidentally damage parts occasionally. However, I really like to encourage his interest, so I let him touch and and inspect the airframes when he asks. He is actually surprisingly careful.

David, thanks very much. I think all parents think their kids are handsome, but it is always nice to hear it from someone else.

Scott, you're welcome. There are some beautiful builds on this site. I refer, for example, to the wonderful static builds by David Duckett and the very educational step-by-step builds by Phugoid (Andrew) and Scigs30. There are many others. I don't think I'm in their league, but I do a few things differently and the info might be useful to someone.

Back to the build: I did not make that much progress since the last update, but I did get a few things done. After completing the framework, I painted one coat of sanding sealer on all the edges that will touch the tissue. The sanding sealer is a local (South African) brand, but I am sure just about any equivalent will work equally well. I thinnned it significantly with lacquer thinner, which I mixed with it in a smaller bottle that is much more convenient to use:



There is of course not much to show from that step. I waited for the sanding sealer to dry and harden and then lightly sanded everything again with relatively fine sandpaper (400 grit). I used the opportunity to double check all the joints and add a bit of glue here and there.

I like to start the covering with the small bits and pieces. These parts are less interesting to me, so I try to get them done first before the real fun starts. I planned to make the wing struts black. The tail wheel assembly would be partially painted - some of that in silver. I found that black tissue makes one of the best base colours when you plan to paint anything silver or another metallic colour - something that I learned from my plastic models. So, the tail wheel assembly also had to be black.

I find Esaki tissue by far superior to just about any other tissue that I have used in the past. Unless the kit comes with a high quality domestic tissue (for example, the new laser cut Pilatus Porter comes with a nice useable red tissue), my first choice is usually to use Esaki. The only problem with Esaki is that it can be a little transparent once sealed with clear dope, so I decided to chalk the tissue. The black was simply chalked with black pastel chalk rubbed onto the dull side - the side that will eventually end up on the inside. There are many articles describing how to chalk tissue, and it is pretty easy anyway - I'll just give the highlights. I started out by cutting a piece of black tissue that would be roughly enough for all the parts that I planned to cover in black:



Then I used a razor blade to scrape some powder from the pastel chalk, dusting it over the tissue:


A small piece of paper towel was used to rub it in. The process was repeated a few times until I was satisfied that the tissue was covered evenly:


A hint at this stage: Don't do this on a bare melamine counter top like I did here. It took longer to clean off the black smudges from the counter than it took to prepare and chalk the tissue. Use a sheet of paper or something else that you can throw away when you're done.

[Mfezi]

I prefer to use clear dope for covering. I know glue sticks and white glue are both very effective alternatives. However, I have experimented with both in the past and just find the clear dope method easier. It is probably just because I had more practice with this method. Two reasons I prefer it are that (1) while working with it you can flood it with thinner anytime, which loosen it and allow you to re-position the tissue and (2) the tissue doesn't wrinkle up when wet from thinner like it does from water based glues. The second point is less of an issue with Esaki which is quite useable wet, but with domestic tissues it can be a problem - at least in my experience. Of course, if you are sensitive to lacquer thinner or forced to work in a small enclosed area where proper ventilation is a problem, you will probably have to use one of the more environmentally friendly alternatives.

Once again, I use some local materials but any nitrate dope will do. The stuff as it comes in the bottle is usually too thick, so I thin a smaller amount about 50:50 with lacquer thinner in a smaller bottle. I also keep a separate container of clean thinner within reach to dip the brush in when it gets sticky and for above-mentioned re-positioning of tissue when needed.



The process from there is pretty simple. Brush a bit of thinner on the balsa part and place on the tissue:



Turn around and flood some thinner from the outside to make sure the tissue is properly stuck down. This is a good time to re-position as needed to get any wrinkles out of the tissue:



After letting it dry, trim around the parts, leaving about the thickness of the part around all the edges. Then stick down the edges by brushing on some thinner, wetting the tissue to help it fold around the tight bend, gently rub the tissue down (adding a bit of thinner or dope if needed), and let it dry. After trimming:



After sticking down the edges:



Once dry, I remove any excess tissue with a sanding stick (by sanding right on the corner to cut through the tissue) or with a very sharp scalpel:



Repeat the process for the other side. When completely done, I brush another coat of dope all around the edges to seal them properly. There is nothing as annoying as discovering a loose edge when you start painting (if you plan to paint the tissue, of course):



Right in the corners on the inside of the main struts, for example, you might notice small triangles of wood that could not be covered completely because of the way the tissue is folded. These are barely noticeable, but I like to touch them up later with a littlebit of enamel paint. Next, I'll start working on the tail pieces...

[shawn32671]

I really like your work up to this point of the build, it sure looks better than mine turned out that I built earlier this year....As with all of my recent builds I post a video of progress and finished model on youtube so here's the link for anyone wanting to check it out.

http://www.youtube.com/watch?v=9rJYAd5BqgA

[Mfezi]

Hi Shawn. Very nice! I still feel, as mentioned in my first post, that Guillows could have done a little better than the white and grey tissue. This series is meant to serve as an introduction to scale modelling, and some nice cub yellow tissue would certainly have helped to inspire a first time builder, for very little increase in cost. A good domestic tissue would have been fine - it didn't have to be expensive Esaki. Of course, that is just my opinion.

Did you fly your model?

I've covered the tail and made some of the paper parts. I'll post an update again in the next few days.

[shawn32671]

i really havnt attempted to fly rubber powered planes in a long long time, I'm always too scared of bad landings wrecking the models.

[Mfezi]

I decided to cover the model in yellow and blue. More specifically: Since it is a Cub, I wanted it in yellow. My son insisted on the blue, and arguing with him about something like colour would have been futile... Yellow and blue (with black struts) it will be. The chalking method on Esaki gives you some interesting options. Esaki tissue is not made in that many colours, but with pastel chalks you can make fairly significant colour shifts from the base colour. I experimented with the yellow tissue and a few different chalks. Remember I chalk the rough "inner side" of the tissue, but the picture was taken showing the shiny "outer side":



I liked the yellow tissue + yellow chalk, but you can see if you wanted a deeper or lighter colour, you could have achieved that quite easily with the chalks.

I don't think it is necessary to show every step for every part, but I took some progressive pictures of the horizontal tail so you can get the basic idea. There are many books and websites that cover the techniques in detail. I started with a coat of thinned dope around the edges. On the stab, I like to put some dope on the middle support also. The coat of thinned dope dries almost immediately. Remember, there is a big difference between "dry" and "cured"; while only dry, you can re-activate the dope any time with some thinners. I then lie the frame upside down on the tissue. Since the dope is more or less dry by then, it doesn't really stick the tissue down but it will hold it in place more or less. I then "tack" the tissue down using thinners flowed right through the tissue using a brush. First on the middle support, then on the wing tips:



I do pull the tissue a little when I flow the thinners through and rub it down very gently with my finger until it feels dry. Next I continue doing the same at some intermediate points, now pulling the tissue across a little:



Remember, if you see any slack or wrinkles, you can re-activate the dope any time with some thinners, move or pull it a little and then rub gently down until it feels dry to the touch again. I then do the remaining parts until the entire edge has been stuck down:



I now leave it at least 30 min before starting the trimming process. I follow exactly the same process that I did for the struts to trim the tissue. Notice that I fold it over the thin edge of the part, but not back onto the opposite side. Once one side is trimmed and folded, it looks like this:



A small note about the above picture: Note that I did not fold the tissue over the lower part of the rudder where it will be glued to the fuselage. Notice also that you can barely see any wrinkles at this stage on the photo. In real life it is pretty good, but not perfect yet. It still needs the water shrinking. Of course, I first continue to cover the other side. Again I wait 30 min, then trim the edges and fold over. When I am done, I brush a generous coat of dope all along the seam at the edges to make sure they are glued down properly. The whole thing is then left at least overnight - no need to rush to the next stage...

When it comes to shrinking with water, I do it differently from what I see most people do. I don't really wet the tissue: I use a water bottle that sprays a very fine mist. I then spray into the air, and waft the part through the water mist once. I repeat this three or four times until the tissue goes slack. To give you some idea how little water actually ends up on the tissue - after 5 minutes or so the tissue is essentially shrunk and dry. It really gives you a lot of control and stress wrinkles or "banana parts" due to too much shrinking seldom happens. You can repeat the process if it is not perfect after the first time, but I stop as soon as it looks completely tight. This is what the part looks like when damp:



I do only one side at a time on tail surfaces. Because the shrinking is so gentle, this is ok. As soon as it is damp, I place it on a flat surface, damp side up, and start putting weights all around it. The little humbrol cans are more than heavy enough:



Notice that the tissue is already almost shrunk in the picture, even though I had just finished putting the weights on. I leave it long enough to dry fully before I do the other side. Once the other side is also done, I leave it overnight to dry out completely. This is what it looks like all done, ready for dope. Notice that by putting the tissue on neatly in the first place and following the very gentle shrinking process, there is not a single wrinkle left at this stage:



Of course, getting more complex parts like the wing completely wrinkle free is much more difficult, but it can be done. I should also mention that I don't think twice about removing the tissue and doing it over. If you have any deep wrinkles at this stage, using more water won't fix it. The easiest by far is to brush on a liberal coat of thinners, wait for the dope to soften, pull off the tissue, wait for it to dry, sand gently and then start all over. Everything worked out nicely this time, but in the past it has happened that I had to cover a part three or four times before I was completely satisfied.

[Mfezi]

I also made some of the paper parts - the fairings that go over the diagonal landing gear struts and the simulated intake under the cowl. I traced the templates from the plans when I made the balsa parts, so I had those available already. I prefer to make all my paper parts from watercolour paper. You can buy watercolour paper in different thicknesses (or weights) at any shop that sells art supplies. I can't remember what weight I bought last time, but it is a very smooth relatively light paper as far as watercolour paper goes. The advantage of using this paper is that it has no grain, unlike your typical printer paper. It is similar to thin card, but is much easier to manipulate and not as dense. You can wet it a little and then bend it, wait for it to dry and it will maintain its shape. You can also sand it once it is dry. It is the only paper that works for me when making paper wing root fairings.

I simply stuck the paper templates to the watercolour paper like I did with the balsa parts:



I then cut them out and peeled off the templates. To bend the fairings, I wet the paper with a brush dipped in water along the bend line. I then gently bent it and put the strut itself in the middle as a spacer. The trailing edges were then glued together using white glue and pinned down:



Once dry, I sanded the joints smooth and also sanded the paper down in thickness a little. The dummy intake under the cowl was bent by gently scoring the paper and then bending along a ruler, using a single-edge razor blade as a folding tool. Anyone working with photo-etch material on plastic models will be familiar with that technique.

Once everything was done, I brushed on one coat of sanding sealer, just like I would have done for balsa parts, and again sanded it with some fine sandpaper. Here is the final result, ready for covering:



Notice on the picture above that I still had to sand the edges a little.

[Mfezi]

I covered the landing gear parts using the same methods as before. The paper parts were covered using exactly the same methods as covering the balsa parts:



I wanted to experiment a little with the colour combinations, and to do that I needed to do the first stage of doping on the tail surfaces. Just like I don't like to flood the tissue with water for shrinking, I also don't like to flood it with dope when doping. Doing that has two disadvantages:
1) It adds a lot of weight very quickly, which means one or max two coats is the most you can practically do on a flying model.
2) It results in some additional shrinking, often causing new wrinkles.

Instead, I like to build up the dope very gradually. To do that, you will need an airbrush unfortunately. A possible alternative is to use an aerosol clear coat such as Krylon clear, which I have not tried yet, but I have heard that it works quite well. If you plan to airbrush the dope, like I do, just about any airbrush will work. Even a cheap single-action airbrush should do the job. Ideally, don't use a fine-line needle, as it may get blocked and you will take a while to cover a big area. I use the same double-action airbrush I use for my plastic models, but with a 0.4mm needle:



To airbrush the dope, I thin it even more. Mine was effectively thinned to dope:thinner = 25:75. It should be very thin. The first coat is then almost misted on. I don't really aim for a "wet look" at this stage, and if the tissue starts to sag, I know I am putting on too much. Because it is so thin, it should take only about 10 to 20 minutes or so to dry completely to the touch. You can then turn it around and do the other side. What this first coat does is to start sealing the tissue, while it also prevents the tissue from soaking up too much dope during subsequent coats.

I then sand the tissue very lightly with very fine wet/dry sandpaper (used dry in this case). About 800 to 1200 grit should do the job. The idea is just to remove any "fluff" or roughness and also any ridges that might have been left on the edges where the tissue overlapped. The tissue should feel nice and smooth. Of course, you have to be very careful not to overdo it - especially on sharp edges you can easily sand through the tissue if you don't take care. I then spray on the second coat - possibly a little heavier this time but I also stop before it looks "wet". When this dries, the tissue looks almost ready and you have put on only a fraction of what you would have put on with a brush:



I plan to do a third coat, but only once all my trim has been added. For this, I made a small motif for the tail. The process is pretty simple:



I then brushed on a coat of thinned dope (the same viscosity that I use for spraying) on the inside of the motif part to lock in the chalk. I wait a few minutes, then brush on a second coat. Wait for it to dry to make it easier to position, place in position and then flood some thinner through to reactivate the dope and glue it into place:



As you can see, I didn't use enough chalk and the yellow is really coming through too much. There are various ways to prevent this. You could, for example, spray some blue paint on the inside of the tissue to make it truly opague. The problem is, once these things are on, it is very difficult to remove without messing up the covering. The easiest solution was to just double up on the markings. I first lightly sanded over the marking to minimize the edges and make it as smooth as possible. Then I added the second one:



When that dried, I again sanded it very lightly and it actually looks pretty good. Despite being two layers, it is actually quite thin and not much thicker than the decals supplied by Guillows.

[Mfezi]

I completed the wings since my last update (among with some other bits and pieces). I was just going to post pictures of the results, but thought that someone might find the techniques useful or, at least, interesting. By the way, if you ever need a really good step-by-step walk-through on building a balsa model aeroplane, I can highly recommend this section on Mike Stuart's website:
http://www.ffscale.co.uk/comper.htm

I originally planned to make the whole wing yellow, but after a long argument with a certain four-year-old, it was agreed it would be blue and yellow. That complicated things a little. First I covered the bottom sides using one piece of tissue for each wing. The method is no different from the one used for the tail surfaces, since it is completely flat. Stick on the tissue as before:



...and trim and fold the edges over (without going over onto the upper surfaces). Next the upper surface. I planned to use yellow from the main spar to the trailing edge, and blue in front of the main spar. Due to the shape of the wing tip, I figured I would be able to cover the entire upper surface (from the spar backwards and from the root to the very tip) using one sheet of tissue:



Notice at this stage I did not glue it to the tip itself. Unfortunately, I didn't take pictures, but I had to wet the tissue at the tip with a wide brush dipped in water to "wet cover" it. I then glued it down while gently stretching it. This is something you can do with Esaki tissue that is very difficult (but not impossible) to do with domestic tissue. Once the tip had shrunk back, I trimmed the tissue about 0.5mm oversize at the trailing edge, folded it over and sealed it. The overlap between the upper and lower tissue is therefore directly on the trailing edge. I then gently shrunk the upper surface tissue using my "misting / wafting" technique. Normally it is better to wait until the whole wing is covered before shrinking, but if anything went wrong it would be very difficult to replace the yellow tissue once the blue has also been added. As it turned out, everything was fine and it was completely wrinkle-free:



Now for the blue. I learned my lesson with the transparent motif on the tail, so this time I chalked the tissue properly:



Here it was obvious I would have to use a separate piece of tissue on the very tip:



Even on the second-last rib bay, it was necessary to wet the tissue to get it tight. Here it is with some water brushed on and stuck down:



You can see those bigger wrinkles won't come out like this, so once again the dope/thinner method makes things a bit easier. I added a bit of thinner, lifted the tissue gently from the leading edge, pulled a bit tighter and then brushed on some more thinner. As it started to dry, you can see it was looking very promising:



And fully dry, it looks just about how I was hoping it would at this stage. Remember, the rest of the tissue had not been shrunk at this point:



The tip had to be covered with the tissue wet:



As you flood the thinner through to stick it down, you just gently pull and adjust.If you are not happy, add some more thinner, lift it, pull it and stick it back down:



After that, trim everything, seal all the joins with an extra bead of 50:50 dope and then start the shrinking process once everything has dried fully. I don't use a lot of water - as before I just spray a fine mist into the air and waft the part through it until the tissue goes slack. I'll repeat that process a few times if it doesn't pull tight enough the first time. If everything looks good except for one or two places, I just wet the tissue with my finger at the specific place that is giving me a problem. The whole process takes time, but I am very wary of "over-shrinking" the tissue.

I then sprayed two very thin coats of 25:75 dope and thinner onto the wing. I follow each coat with a "flood coat" of pure thinner, which helps to smooth down the dope a little. I also sand the whole wing very lightly with a worn-out piece of 1200 grit sandpaper between coats (after the previous coat had fully dried of course). The final result, bottom:



And top:



I must admit, a certain amount of luck is also needed to get this type of wrinkle-free result. However, that luck does seem to come your way more often as you build more models...

[davidchoate]

thats nice work. i got alot out of it. I smetimes get a little impatient, by showing a times with your thred, I am reminded how important patience is. like when tou let the glue dry all night before contunuing to the next step. that stuff makes a difference in the outcome. thanks for reminding me of that, and thanks for your ideas

[Mfezi]

thats nice work. i got alot out of it. I smetimes get a little impatient, by showing a times with your thred, I am reminded how important patience is. like when tou let the glue dry all night before contunuing to the next step. that stuff makes a difference in the outcome. thanks for reminding me of that, and thanks for your ideas

Hi David

Thank you very much. I am glad you find some of it helpful. I was overseas on holiday and haven't had time to work on the model since I got back, but will try to get going again this week.

[Mitch]

I like the Blue trim... I'm glad you listened to the "Inspector"! Mitch

[Billy Mc]

Great work, I started building one of these several weeks ago. I've built more plastic model than I care to count, but this will be my first balsa model.

[davidchoate]

nice job. I'm doing the same plane for my G challenge. will U use the blue rubber, and do U have too for the rules? and will you please post U'r final wght.?

[Mfezi]

Hi Everyone

I completed this model a long time ago, but somehow just never got as far as uploading my progress. I will do it in a few separate posts over the next few days, as there was quite a bit more left to do after my last post.

Before I go on, just to answer David's questions:

nice job. I'm doing the same plane for my G challenge. will U use the blue rubber, and do U have too for the rules? and will you please post U'r final wght.?

Thanks for the compliment. I have not flown the model yet, but I have no intention to use the rubber that came with the kit. My experience with Guillows rubber has not been very good. However, although I am sure this model could do with a bigger or better propeller, I do think it will fly fine with the Guillows propeller if you don't intend to try and compete with it. I just build and fly for fun.

I don't know how the G challenge rules work, so I can't answer you there. The final weight of my model including everything, even the wheels, propeller, struts, paper scale details, etc, but without rubber, was 26 grams. There are ways to make it even lighter - for example, I used three sprayed coats of thinned clear dope whereas one would have sufficed, I didn't have to paint the wheels and struts like I did, etc. Once again, I build for fun, so I am willing to pay with a few grams to make it look a little better. My CG was almost spot on, and I expect requiring only a very small amount of clay to compensate for the rearward move when I add he rubber.

So, back to the build. When I left off, the wings were done and it was time to cover the fuselage. At this stage I could have covered it all in yellow, and it would only have taken one evening to finish it all up. However, I wanted something more interesting, so I used the pattern that Guillows use for the 300-series Piper Cub as inspiration for my own design. I wanted to do the pattern using only tissue and without the use of paint on this model. Designing the pattern took a bit of effort. Here are the steps roughly:
1) Scan in a side view of the plans, clean it up and open it as a background image in CAD. I used DraftSight, which is a free CAD program published by Dassault Systemes.
2) Do some scaling in the CAD program to ensure the sideview appears exactly full-scale.
3) Trace the side view using the various draughting tools provided in DraftSight.
4) Design the pattern like I want it to appear.
5) Work out what should be yellow tissue, what should be blue, where they need to overlap each other, etc.
6) Export individual patterns for yellow and blue tissue and print these on normal paper.
The whole process is not particularly difficult, but it does take time. You could have done exactly the same by hand on a few sheets of tracing paper or draughting velum. A computer is not really needed, although it makes it easier.

Here is an overall printout (slightly smaller than full-scale), a printout of the yellow pattern only and a few pieces of yellow tissue already cut:


Of course, I made sure I made a left and right side, since the Esaki tissue has a smooth and rough side. Once again the tissue was chalked to make it a bit less transparent, and then it was carefully positioned on the fuselage with the usual clear dope and thinners method:


At this stage, the top of the fuselage could also be covered:


Now for the tricky part: The blue. First I printed the pattern again on normal printer paper:


Cutting it was a very delicate process. I used low-tack masking tape to keep the tissue in position as I carefully cut it with a scalpel with a brand new blade. Using a blunt blade here would be recipe for disaster. As I went along, I moved and changed small pieces of masking tape to keep everything in place.


Once the two pieces of blue were cut, there was still a bit more preparation work left. Next I again rubbed on chalk. This time I made sure it was very well chalked, otherwise the yellow was going to show through as soon as I glued the tissue down:


Of course, there was now the danger that the blue chalk was going to go all over the yellow tissue. Furthermore, it was necessary to pre-coat the tissue with dope so that I could just activate it with clean thinners to glue it down while I kept it in position. What I did was to spray on three heavily thinned coats of clear dope on the BACK side of the blue tissue. That is the rough side - therefore the same side on which I had rubbed the chalk. This process pre-coats the tissue with dope, while also locking in the chalk. By this time I had also lightly shrunk the yellow tissue and I also sprayed a thin coat of dope onto the yellow tissue. I then waited for everything to dry to the touch, but not cure completely. Then the blue tissue was held in place and very carefully I started to flood through thinners with a brush. It immediately re-activated the dope and it only took a few minutes to glue down the tissue completely. Here is the result:


Side panels done:


The top of the nose and bottom of the fuselage could then be covered normally:




After this, it was just the home-made registration decals, a few more details and then final assembly...