You align a profile model that same as you would a full fuselage model. When you first lay out the fuselage, or lay out the pattern you are going to make for it, study the plan and be sure of the wing center line, power plant thrust line, and the horizontal stabilizer line. To make things simple, you can build a 0-0-0 model where everything lines up! But if the thrust, wing, and stab lines are all different, carefully measure the dimension of the thrust and stab line from the wing center line, and make note of it. Draw a clear, clean wing center line on your fuselage pattern or on the balsa plank. I like to use a fine point ball point pen or a fine point Sharpy.
If the thrust line and stab line are different, mark out the center lines for those by measuring up from the wing center line. I use those Westcott brand metal office rulers in 6", 12" , 18", 36" and 48" lengths. They have nice, sharp lines for the divisions. Be careful and accurate with your markings. When finished, draw the line as far as you can on your patter or plank. Now you can check the dimensions you noted in several different places to see how well you drew the line parallel to each other. That is your guide for alignment.
Make the cut out for the wing on your pattern as accurate as you can. You have a line to follow and the line has thickness. The thickness of the line and where you cut the piece can make a difference in how it fits. I cut the pattern on the outside of the line. Then when you trace it, that line will be pretty close to where it should be. When cutting out the slug, cut it out to the inside of the line. If you try to slide the wing in, it probably won't fit, so you get your sanding tools out and sad the cut out to the outside of the line. Doing this slowly and carefully gives you a good fit. Make sure the edge of the cut out is square as yoy go. If you get a big big here and there, don't sweat it .Work at it and when you can get the wing in place, eyeball it from the front and you should see that it's pretty square already. Do the same with the stab. It takes some focus and practice to read a ruler accurately. In building machinery and installing printing press and bindery equipment, you learn to read a ruler to the front of the line, back of the line, or to the center of the line. That can give you an accuracy of .015" to .030" or so, which is plenty close for out purposes. But it does take practice.
When you check the stab cut out, if it has one, you can measure to the wing center line that you drew. Slide the stab in place and then you can measure right to the stab surface, or leading edge and trailing edge center line if it has an airfoil shape. The engine center line will guide you when cutting the engine mounting space. You can make a crutch with the engine motor mounts and scrap balsa, and then cut the fuselage plank to accept that crutch. The inside edge of the motor mount stock should be parallel to the engine center line. When you get the crutch mounted where it should be, get things sanded for the ply wood doublers. When those are glued in place , trimmed and sanded, transfer the engine thrust line to the forward fuselage again for further reference.
When you get down to the point to do final assembly, get your ,measuring tools together , and clear work table, and some time and patience. I have accumulated several Robart incidence meters. One can be great help, but three will let you measure everything at once when you want to and are ready to glue things. Get the wing glued in first. You want it sguare vertically to the fuselage and you can check that with a simple triangle, and also for and aft and you can check that with the same triangle or a larger one. Work slowly and carefully here as everything else will be based off of this. When the wing is set up, the stabilizer is next. Square it up vertically first, and measure from the wing trailing edge back to the stab trailing edge to get it square with the wing. Tack glue it in place for now.
If your fuselage is already drilled for the engine, now is the time to mount it. Clamp up the fuselage or jig it up some way that it is secure, and put the first Robart meter on the wing. Adjust the fuselage to where the meter is at "0". Take the second Robart meter and attach it to the engine by the part that is intended for that. If the wing is at "0", then the engine should be at "0" also. If not do what you need to do to get it that way. If you are inclined to add a bit of down thrust, now is the time to do it, or make sure you can adjust the engine as required by a couple of degrees each way. The stab is last. You can take the meter portion of the Robart meter off the rest of the assembly and just set it on top of the stab. It should be at "0", and if it isn't now is the time to fix it, or if you want a half degree or so of positive incidence in the stab, now is the time to set it.
Once finished with the stab, you can check all three at once now. Complete the gluing in process of everything, then recheck the alignment. If you do not have or want to invest in the Robart meters, (I found them really cheap at model swap meets) and you were careful with your marking and measuring, you should still have a very closely aligned air frame. Check it as you assemble it and triple check it as you finish. And again, a full fuselage model is assembled and aligned in the same way. Keep an eye out at the swap meets for those Robart meters! They make it a lot easier.
Type at you later,
Dan McEntee
Topic: video that shows how to align a profile airplane (Read 1789 times)