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Tips & Tricks for Building Better Models


Gluing up skins for sheeting

Seems like a no brainer right? Grab some sheets and glue the edges together until you have one sheet big enough to do the job. Well, that's a pretty simple summation of the process but, as with many other aspects of model building, the devil is in the details. Here is how I get the job done:

1. First off, choose your sheets carefully. Balsa comes in three grain types, A-grain, B-grain, and C-grain, which is determined by how it is cut from the log. It also varies in density. For a good explanation of balsa grain types and uses see here. We need to choose the grain/density combination that works best for the job. For sheeting a model the size of the Hellcat I generally shoot for a medium density A-grain. If you have some in your stash the light density A-grain can be used on the tail surfaces to save some weight at the rear end. Try and use sheets that don't vary in density and grain too much as it becomes very difficult to sand accurately when one sheet is softer or harder than the next. Lastly, don't use wood that is too light in those areas where you will be handling the model.

2. Very rarely do balsa sheets come from the supplier with a perfectly straight edge. I use a metal ruler and a brand new #11 blade to put straight edges on each sheet prior to gluing. I also generally bevel them to give a bit more glue surface. This is done by simply holding the knife at a bit of an angle while cutting. It takes a bit of practice but you will probably find that you naturally hold the knife at an angle anyway and it's just a matter of being consistent with each cut.

3. Once you get a good fit of the sheets tightly hold them together and run a strip of masking tape along the seam to act as a hinge.

LAYING UP THE SHEETS

4. Now you can open up the sheets, apply glue to the joining edges, and then close them back up. The tape will ensure that the two sheets come right back together in perfect alignment while the glue dries. Speaking of glue, if you want to achieve the best results then you probably don't want to use CA for this task. The instant glues get much too hard and it is impossible to sand the glue joint to achieve a smooth transition between sheets. Aliphatic (yellow wood glue), white glue, or Ambroid/Sigment are much better choices in my opinion.

APPLY THE GLUE

5. Squeegee the excess glue from each joint and weight the sheets down underneath some glass or a piece of MDF or by some other means to keep them perfectly flat while the glue dries. You will probably want to put some wax paper between the sheets and your weights to prevent gluing the two together.

REMOVE EXCESS GLUE

6. When the glue is dry carefully block sand your sheets on a flat (and clean) surface to blend them together. It is best to do the majority of your sanding now and as little sanding as possible after the sheets are attached to the structure. This is because the sheeting will sand away at much faster rate where there is structure underneath, i.e. ribs or bulkheads, and at a slower rate where there is no underlying structure. This makes it very difficult to get a smooth surface.



Strip Planking a Fuselage

A few tips that may help to simplify what can be a laborious task.

1. Choose straight grain balsa of the proper density. On the Hellcat the fuselage sheeting bears most of the load and so the planked areas can be done with light, low density balsa to make the shaping process easier and keep the weight down.

2. Don't use instant glues! I can't stress this enough. Instant glues get much harder than the balsa wood and make it impossible to sand and blend the planks into a precise shape. I prefer yellow carpenter's glue for the task but I have also had good results with Ambroid and Sigment model airplane glues.

3. The width of the planks depends on just how tight the curve that is being planked. When in doubt go smaller rather than larger. Generally I don't use planks much wider than about 1/2" for anything on a model the size of the Hellcat. Notice I said "generally" because there are instances where wider planks are used and at times a tapered plank will be necessary that can be much wider on the large end. Experience, practice, and maybe a bit of research to see how other folks do the job are the keys.

4. Start your planking at the same spot on both sides of the fuselage and then work up or down until you meet in the middle. Generally you can get away with constant width planks for the vast majority of the job with a few precisely cut tapered planks where the two sides meet in the middle.

5. Cut an angle on your planks as seen in the drawing below so that they interlock together as you install them. This allows for more glue surface and helps to keep the planks accurately shaped and located while the glue dries.

PLANKING DIAGRAM



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