Building Frenzy Syndrome

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The "Building Frenzy Syndrome"
By Mark Kallio

Now that the weather is starting to become more favorable to building than flying, I'd like to share some things that I have discovered which makes the building experience an enjoyable one. The majority of LFE flyers build from kits (actually I've never built from plans or the like and couldn't help much in this regard) so kit building will be the main focus. My intent here is not to reinvent the wheel. Most quality kits nowadays contain a fairly comprehensive and complete manual on how to correctly build the plane. Rather, I'll focus on what they don't or won't tell you. Also in coming issues, we'll again explore the wonderful world of covering with MonoKote as well as other covering options. Hopefully there will be some things of value that you can use. That said, let's get to it.
Many of us get that new kit and rush home to start building so fast that we really haven't the first clue how the thing really goes together and what part fits where. I have fallen prey to this "Building Frenzy Syndrome" on more that one occasion and have deeply regretted it on each occurrence. Get to know the kit first. Read the instructions, study the plans, look at and organize the parts by sub-assemblies. Know how the plane is put together before you even think about using any glue. When I buy a kit I NOW always read the assembly manual and study the plans over and over again so that by the time I start building the project, I can almost do it by memory....But don't try to build from memory, I have also done this and learned the hard way that this ain't the way to do things. Anyway, knowing and planning an assembly before you build it will save time and money. Rather than having to stop and over analyze while building a wing and trying to figure out how to install retracts after you put in the blocks for fixed gear, you should have had this planned ahead of time.
While in the planning stage, you should make sure that there are no surprises along the way when it comes to tools required. Common sense tells you that you have to have the right tools to do the job AND always use the right tool for that job. As an example, some kits require quite allot of carving solid balsa blocks to shape. Well, the right tool for this job wouldn't be sand paper alone. A small orbital sander or your Dremel tool with a sanding drum attached would be a far better choice. As a matter of fact, I have found that my wife’s potato peeler works great to rough shape balsa blocks (due to the various brands made, some work better that others, but this is a really cheap tool so get a few and find out which works best for you). If the model has built up tail section or aft fuselage section, you would be wise to invest in a miter sander for all those butt-joints. Better yet, an electric drum and belt sander is an invaluable piece of equipment. I can't believe that I did with out one for so long and it's still today, the most used piece of equipment that I own. On a closing note here, clean up and organize your tools often during building. I get more frustrated trying to locate that Exacto knife or pair of pliers that I just had seconds earlier. Believe me, you'll save more time in the long run by staying organized and keeping the shop clean. Throw away spent balsa scraps often, keep that shop vac handy, and most of all - keep the tools where they're supposed to be and put them back after your done with them.
Lastly, you should have the trim design well in mind prior to building. Certain trim designs might require the addition of wood supports for splicing MonoKote (never, ever splice MonoKote over an open structure. Although this can be done, it is a very difficult thing to do correctly. It may look great and last for a while, but inevitably will cause more problems that it's worth.) I always make a three view drawing of the model (top, side and bottom views) go to a copy machine and run off about 20 copies to play around with. After I've decided on what the finished plane will look like, I note all the structural changes required and add them to the plans along with notes describing anything unusual. A good example would be when splicing a light color and a dark color of MonoKote, you should always splice over the lighter color. This would affect the location of the supporting wood in an open or built-up structure. Also, to the extent possible, transfer the final trim scheme to the plans as well. This has helped me in the past to spot my screw-ups, excuse me I mean "flaws", in the trim design and supporting structure.
One particular trim design I prefer is to have a large contrasting color stripe running the length of the fuselage to facilitate plane orientation (it also looks great!). However the majority of kits utilize lite-ply in fuselage construction, leaving large open areas. Although the solution to this adds weight to the plane, something to be avoided in most every case, the weight penalty is minimal. What I have found that works well is to laminate a piece of 1/64 inch plywood over the fuselage sides. This plywood ain't cheap. Expect to pay about $20 for a 12"x48" piece. However, you should only need one to sheet a normal fuselage. After sanding the fuse to eliminate any protuberances, I apply "Sig Kwik-Bond" to the plywood and the fuse according to the manufacturers instructions (be sure to tape the plywood down to a flat surface along the complete perimeter prior to doing this as the plywood tends to curl after this application of Kwik-Bond. Also, don't remove the tape until after the fuse has been bonded to the plywood. Very important....). After that, It's a simple matter of insuring a good bond between the two. To do this, I borrow my wife’s rolling pin and go over the entire fuse. Finally, the easiest way to trim the overhanging plywood is to use an Exacto knife to trim the excess. You can't cut through the plywood on the first pass, but the third pass will cut it cleanly off with hardly any sanding required afterward. Attaching MonoKote to plywood isn't difficult, but it does require a certain technique that will be discussed in a later article.
Before we get any further, it would be most advisable to tell you some of the pitfalls of kits. First of all, the biggest problem in most kits today is the wood. To be quite honest, the only thing of value in them are generally the bulkheads, main fuselage components and wing ribs. Very little else in them are good to excellent quality. The plane will be only as good as the materials used in it's construction. In other words. "If it don't fit; It ain't worth !@#$". A short breakdown of materials typically discarded are:
Sheeting: Balsa sheeting should be light weight and of a consistent density. It's easy to tell if sheeting is heavy even without weighing it. If the grain looks tight (look at the ends of the sheet. It's fairly apparent.) and the balsa is a dark color, it's heavy. If you need to replace it, look for balsa that's a pale light cream color and if you can, hold it up to direct sunlight. You should be able to see through it somewhat and select wood of basically the same density. Another thing to look for is gray discoloration in the sheets of balsa. These are usually found on light weight sheets, BUT this discoloration denotes weak, diseased areas. Avoid gray balsa like the plague. A final word of caution here; Don't use light weight balsa for sheeting the center of the horizontal stab, you'll regret it.
Balsa Blocks: This is pretty much the same as balsa sheeting. I have found some "kit wood" balsa blocks to be of excellent quality but the majority of the time they would be better suited as anchors.
Wing Spars: If these aren't straight and true, I mean absolutely no bends or warps whatsoever, I replace them. If I do need to replace them, and I often do, get some good quality spruce or basswood. Balsa wing spars just seem to me to be a contradiction of good sense.
Stick Balsa: Not only do these need to be of the correct weight and density for the job (medium balsa for wing trailing edges, rudder/elevator leading edge, cap strips and bracing) but they also need to be the right size. There has been many a time that the "kit wood" was not even close to being the correct size or had a gradual taper to it. By the way, could somebody tell me where I should use a light weight piece of stick balsa? I see this stuff all the time in kits.........
Aileron Stock: Just like wing spars, if these aren't straight and true, I mean absolutely no bends or warps whatsoever, I replace them. Also I have found many made from light-weight balsa, a definite no-no. These should be of medium weight & density. If they aren't...........well..........you know by now what to do with that stuff (I'll tell you how to straighten out the bends and strengthen light-weight aileron stock so that it may be used next month).
Lite-Ply: Although rarely have I had the need to replace this stuff, be wary of pieces that contain allot of knot-holes. This compromises the integrity of the wood tremendously. Also, even if the plan calls out for it, don't use it for a firewall or engine mount. (Yes, I've seen this before - on an ARF)
You may think that replacing all this wood is unnecessary and really doesn't add much weight. Well, that ain't so. On a typical 60 sized airplane you can add 2 oz. easily to the tail section aft of the C.G. by using heavy balsa instead of the medium to light-weight stuff. This will require that you add approximately 8 oz. to the front of the plane to compensate for this. Also add in the 3 oz. or so to the weight of the wing (assuming of course that you used the "kit wood" here as well) and the 3 oz. of weight for using the "kit wood" balsa blocks. So for using that "kit balsa" now we've added 1 pound of weight to a plane that should weigh 7 1/2 pounds total. The difference being that at 7 1/2 pounds, the plane would be a sparkling performer; At 8 1/2 pounds, performance suffers greatly. The overall point that I'm trying to make here is that EVERY OUNCE COUNTS !!!!
Now we're just about ready to start, but I think that the following should be stated prior to the actual construction. A correctly built and set-up plane will do exactly what you tell it to do. In simple terms, if your model is not to design specifications, or it is not "straight", it will probably still fly but the misaligned model will constantly change trim or have odd reactions to control inputs. You will waste more time struggling with a model that isn't "straight" than it takes to build it accurately in the first place.
If you believe that the cut parts in a kit will produce a "straight" model when assembled, think again. They don't........... Due to the various levels of "acceptable tolerances" used in the model's manufacture, the assembled plane can be far from perfect. So just how are we to compensate for this? The only tried and true method for this is to follow and believe the information on the plans and contained in the manual. All information contained in these are usually well thought out and tested. Unless you know what you are doing or have a specific reason to deviate from the design parameters, accept them as "gospel" and build to them.... If there is any conflicting information contained in the plans and/or manual, call the manufacturer and get the answer....don't guess!!! Just about anyone can build a "straight" airplane if you follow the manufactures recommendations. There's no substitute for experience though. Some techniques used by different manufacturers work better than others.
It's hard to believe that we still don't have any wood glued together at this point, but first things first. Next months article will deal with some more "Tricks of the Trade" on how to do it right the first time around and how to fix it when you forgot to do it right the first time.