OK, this is going to take a little while to explain, so let's just jump right in and get started. We start by truing up the edges of all of our balsa sheeting. I just went ahead and did all the sheets for the wing at this time to, so they'll be ready when I get to that phase of the build.
There are a number of ways to true up the edges of your balsa sheets, but here's the method I like. I first take a long 4-5 foot metal ruler and lay it on each sheet to as a guide to cut the straightest edge I can with an X-acto knife, on both sides. That will get you very close. Next I use a long piece of aluminum "L-channel" which is basically like a piece of angle iron, and clamp it along the edge of my table. This metal piece has sandpaper adhered to the surface that you will have sticking up vertically on the table. In addition to the clamps on the ends, I put some building pins into the table up against the backside of the angle bar to keep it from flexing inward while sanding.
Now it's as simple as sliding each edge of each sheet back and forth down this sanding bar until your edges are true. Once this is done, you can go ahead and start gluing them edge to edge until you have one big piece that is tall enough to wrap around your fuse from centerline to centerline, making sure you have some extra for tolerance. I then rough cut it to the approximate shape of the fuse and move on to the next step. Note that you can do your edge-gluing however you prefer, I like to lay my sheets on wax paper and use thin CA to join them.
Now you can run some low-tack masking tape down the centerline of the fuse, top and bottom. Make the tape offset so that it is all to the left or right side of the actual centerline. In my case, that would be right down the center of the optional centerline balsa strips I added.
Laying down the glue
Before applying any glue, lay the fuse in position on your sheeting panel and put some tick/registration marks on the fuse and sheeting so that you will be able to align it right on spot when you have the glue applied. Once the glue grabs, you are not going to be able to adjust, so make sure you know where to set the fuse onto the sheeting.
Now you can go ahead and apply the glue to the fuselage with your roller. Once your done, pull the tape off and let it set a while. When it's nearly dry, put the glue on your sheeting. It will immediately start warping, but just spray some ammonia/water mixture on the backside and it will relax back to flat, and become flexible for applying it to the fuse.
Applying sheeting to the left side... a learning experience
Well the next step didn't go quite as smoothly as I had hoped, it was quite a learning experience. I've done my fair share of planking with sheeting on fuselages, but this is my first time at trying to apply a whole side in one sheet. Here are the steps I took, and just what I learned in the process.
I began by laying the fuse onto the sheeting, with my tick marks aligned. I started with the front end of the fuse going down first, then rocking the plane downward out to the tail. Now the glue has grabbed all the way down the side centerline, right around the thrust line. I flipped it over and began using a clean roller to start rolling and working the sheeting down smoothly onto the fuselage, working from the side centerline outwards towards the top and bottom.
I worked from the front of the cockpit back to the tail, then went back to the same point and started working my way towards the nose. I made some relief cuts in the balsa where it wraps over the cockpit and wing saddle area so it would allow me to wrap the balsa more easily. Repeat the spraying of ammonia/water as needed to keep the balsa pliable. Now is about when the fun started...
What I quickly found is that when you get to the angular change in the fuselage right in front of the cockpit, I had trouble getting the balsa to lay flat in all directions. This is right at the seam where the front foam section of the fuse is joined to the middle section. The fuse shape changes from a taper from the tail up to a round cylindrical shape, thereby causing a major angular change in where the sheeting needs to go.
No matter how hard I tried, how much I wetted it, or how much I rolled it out, it just wanted to pucker up here around the side of the fuse and up onto the area of the gun hood. Before I knew it, I had a big crack down the side and things were beginning to get quite ugly. Yes, panic started to set in! Well, I stuck with it and cut some excess balsa out of the area and kept on rolling. Eventually I got it to all lay down flat, but it left me with a decent amount of putty work ahead to get it smooth. In the end it all worked out, but now I knew I had to rethink this before doing the right side.
Moving on, I went ahead and cut the sheeting down the centerline on top and bottom right where the masked edge of my glue stops.
Next I cut a couple small triangular wedges of balsa sheeting and applied them with Foam Safe CA to the vertical walls of the exhaust port slot on the side of the fuse up at the firewall.
Lastly I sealed my seams with more FS CA and gave everything a shot of balsa putty. After sanding, I was relieved at the way things turned out and ready to try again on the right side.
Applying sheeting to the right side... much better luck this time
After my stressful experience on the left side of the fuse, I prepared to approach the right side a little differently. My Dad and I had been working together on the whole sheeting process so we came up with a plan of attack that proved to work out pretty well. The whole idea was that now that we knew where the "pucker" was going to rear its ugly head at, we would stop and make a relief cut into this area before even starting to try to roll things out.
This technique is called taking a "tuck" in the sheet metal industry and is quite common. I don't know if this is what others are doing on this kit but Dad and I could see no way around it. I did all the same steps as I did on the left side up to the point where I had the sheeting glued up, and the fuse was laying on it with the whole side centerline adhered. I flipped it over and started to execute my new plan...
I now made my relief cut right at the same spot that there is a seam in the foam fuselage joing the front and mid sections together. My cut ran from about the side centerline up over the top of the fuse under the gun hood area. Then I started rolling out the piece to the rear of the cut so it laid down smoothly onto the top of the fuse. Lightly wrapping the remaining flap in front of the cut over onto the other flap, I end up with a slight overlap. I cut away a wedge shaped piece where the two flaps overlap (taking my tuck) and then rolled out the front flap smoothly onto the fuse.
After this was done, the rest of the sheeting seemed to roll out pretty easily without any major problems. Eventually I was able to go back and seal the tuck cut with Foam Safe CA and use some balsa putty to smooth it out quite nicely. I'm not concerned about strength or stress cracking here as the balsa gun hood I will later build will scab over 70% of my relief cut tying it all back together well.
Finishing up the sheeting
To finish up, I sealed up all my seams with FS CA, did my putty work and moved on to the last bit of sheeting at the tail.
You'll find your sheeting will be just a few inches short of covering the entire tail, so you'll need to scab in a few more short pieces of balsa sheeting to close it all up.
I used the same technique as I did on the rest of the fuse, doing it in two pieces, left and right, from centerline to centerline. Seal again, putty again, and your done!
Final comments & summary
So what is my final evaluation of this entire "two-piece sheeting technique" now after giving it a shot? Well, first let me say up front, I really didn't know what I was doing when I started into it... maybe I still don't. However, I'm sure that it will be easier the next time and that I'd get better at it every time I tackle this step.
All in all, I definitely have to admit that while it was a little daunting at first, it really is easier than traditional planking methods that are normally used on a fuselage and is most certainly a whole lot faster. The whole process took me about 5 hours, even with me not knowing what I was doing. Planking with individual sheets would have taken me much longer.
