Going All-Out With A Classic Balsa B-17-F – Part 12

Going All-Out With A Classic Balsa B-17-F – Part 12

Do you like it when all the separated parts of a project finally begin to come together? I certainly do, and…for me anyway… that’s what starting work on the fuselage of a new model airplane is all about. As you’ve already figured out, I nearly always build the flying surfaces (wing and tail components) first, then concentrate on the fuselage which quite literally brings everything else together and holds it in place. The fuselage of an airplane is nearly always where the most interesting things happen, and for that reason I like to arrange a building project so I can focus my attention on that part with all of the other components “ready and waiting” off to one side. With that said, I’m going to change the emphasis of my writing at this point in the B-17 story. Up until now I have devoted LOTS of time and page/screen space to explaining …in great detail…HOW I cut or glue or sand a specific piece of balsa or some other material. Having pretty well shared all those “inside secrets” with you in the story as it has unfolded so far, now I’m going to concentrate more on WHAT I did, and why, than on the nitty-gritty angle-the-blade-like-this stuff. The most obvious result of this will be that the pace of the project (as I present it to you, at least) is going to speed up.

 

B-17-12-1 Even so, we’re going back to basics to get started. In the beginning this project started out as a (big) classic stick-and-tissue model. I’m starting work on the fuselage…exactly per the original kit design and instructions…by laying out the first of a pair of totally traditional side frames directly over the plan, using clear food wrap film to keep the various adhesives I’m going to use from adhering themselves to the paper as well as the things that are actually supposed to become parts of the airplane. As per the instructions, I’ve pinned the laser cut balsa sheet wing saddle in place and then arranged the various 1/8” sq. and 1/8” x 3/32” balsa longerons, upright and diagonals around it.

 

B-17-12-2 This is the same layout from another angle…from here you can just see the laser cut horizontal stabilizer saddle that I “built around” in the same way.

 

B-17-12-3 I assembled the entire side frame “dry” (without adhesive), checked it for accuracy, and then used Deluxe Materials SuperPhatic glue on all the joints. This kind of assembly is a perfect application for SuperPhatic.

 

B-17-12-4 Up close, a joint freshly glued with SuperPhatic should look like this. As with thin/fast cyanoacrylate, you apply SuperPhatic to the outside of an assembled joint and the adhesive “wicks” itself into everything it touches. This is not “too much glue”. Immediately after gluing a SuperPhatic joint should look “generously wet” like this. Check out subsequent photos to see how neatly the wood structure is going to absorb this stuff.

 

B-17-12-5 With both fuselage side frames assembled and all the SuperPhatic thoroughly dry, I re-positioned them vertically/bottom-up per the kit instructions over the top/bottom fuselage drawing and began joining them by cutting and fitting the 1/8” sq. balsa cross members at every upright location. What you’re looking at here is the wing leading edge station. What I’m doing is using the first (top) 1/8” sq. crosspiece to measure the bottom one so that they come out at exactly the same length, which is a big step in the process of building a square, accurate fuselage.

 

B-17-12-6 Having gone to all that trouble to get the parts cut accurately, my next step is to use a square to make sure the entire assembly really is “square” before I add any adhesive.

 

B-17-12-7 For this part of the assembly sequence I’m switching to Deluxe Materials Roket Hot (fast/thin) cyanoacrylate so I can get these critical-to-be-square joints locked up quickly. I have already “squared” this assembly.

 

B-17-12-8 Here I’m checking the next fuselage station in line the same way before I add the Roket Hot.

 

B-17-12-9 And … the same thing from the other side on the one ahead of that.

 

B-17-12-10 This is the basic framed-up fuselage structure with both side frames aligned over the plan and joined by all the various top and bottom cross members.

 

B-17-12-11 Now I’m adding the diagonal braces to the top and bottom surfaces of the fuselage frame, starting at the nose.

 

B-17-12-12 Aft of the wing the diagonals look like this.

 

B-17-12-13 I have removed the fuselage frame assembly from the plan and turned it onto the right side so you can compare the structure to the plan layout beneath it. The next series of steps are going to be about adding the various laser cut F- formers. Here I have them all separated from the parent balsa sheets and arranged them for identification.

 

B-17-12-14 The pre-existing longerons and cross members, along with all four F-1 formers, are going to make up a complete (circular) former assembly at the nose…and that assembly needs to be FLAT and square to the fuselage centerline. This is the way I chose to keep all the loose bits in alignment and under control. Note that I’m doing the assembly using Roket Hot (fast) over a sheet of clear plastic to avoid building part of the plan into the airplane.

 

B-17-12-15 The rest of the F- former sections can be put together like this. Here I’m using Roket Rapid (medium) so I can add glue along the joining edge of the part and press it into place with at least ten or twenty seconds to adjust the alignment as necessary. This is an excellent example of a joint that could be made properly using either fast or slow Roket cyanoacrylate OR a glue like either SuperPhatic or ordinary aliphatic resin. All of these products work just a bit differently and each has its own advantages. As a model builder you get to choose which one you think would be best for YOUR airplane.

 

B-17-12-16 From F-1 back through F-4 (at the wing leading edge) the fully rounded-out former assemblies look like this.

 

B-17-12-17 Same deal behind the wing looking back toward the tail.

 

B-17-12-18 Here’s a close-up at station F-7. You can see the various sub-sections of the F-7 former assembled in place. The flat-looking piece of balsa sheet across the bottom is the rear end of the left wing saddle, and the 1/16” deep slot between the two side sections of the former is the space into which a 1/16” balsa sheet wing saddle plate is going to fit. The important part is what’s going on in the background…I’m making a reference mark on the main face of the 1/8” sq. balsa upright to help locate some new structure I’m going to add to the original kit design.

 

B-17-12-19 I repeated that little pencil mark exactly 1 ½” down from the top face of the upper longeron on both sides of the fuselage at F-4, F-5, F-6 and F-7, then used the marks to position a pair of 1/8” x ½” balsa strips along the inside face of each fuselage side as defined by the 1/8” sq. balsa uprights. What you are looking at here is the right-hand strip at F-7 as I add Roket Hot from what will be the outboard-facing surface. Why am I doing this?

 

B-17-12-20 …because the airplane as designed does not include a motor battery mounting surface/area that I consider substantial enough. I’m adding structure where I feel it’s necessary to provide me with a practical flying model that will stand up to the everyday lumps and bumps of a real world flying field.

 

B-17-12-21 I have chosen to add a 3/32” balsa sheet battery floor/center deck that will fill the area (from side to side) between the fuselage longerons and extend from F-7 (at the wing TE) all the way forward to F-3 (ahead of the leading edge up to the scale instrument panel location in the cockpit) to provide plenty of room to adjust the location of the LiPo packs I’ll be using. This will be a big help in my being able to get the fore-and-aft balance (CG) right without having to add any extra weight to the model. Those 1/8” x ½” rails I installed in step B-17-12-19 became mounting rails for the new deck. I’m using Deluxe Materials Roket Hot to glue the deck securely in place so that it becomes part of the load-bearing structure of the fuselage and not just a battery tray.

 

B-17-12-22 With the grain of the 3/32” balsa sheet deck running front-to-back, it will still be subject to deformation (squeezing) spanwise unless I reinforce it. Here I’m using more Roket Hot to attach one of several 1/8” sq. balsa stiffeners. There will be one of them at each former location.

 

B-17-12-23 Now I’m working “backwards”…those 1/8” x 3/32” balsa diagonal braces are going to get on the way of what’s coming next so I have to cut several of them out of the way. A careful cut with a sharp razor blade takes care of this.

 

B-17-12-24 What’s going on here is that I’m preparing to add some 3/32”balsa sheet “side plates” to box in what will become the main load-bearing portion of the battery deck and add considerable structural reinforcement. I’m measuring the distance from the longeron to the deck surface that must be matched by the side plates.

 

B-17-12-25 Cut, fitted, and glued in place they look like this. I’m going a step further by framing the box they create with several strips of 1/8” sq. balsa cut to fit the spaces defined by the existing structure.

 

B-17-12-26 With those 1/8” sq. balsa strips all in place it looks like this…I’m using clothespin clamps to assure that I get tightly-fitted joints with the side plates along the full length of each 1/8” sq. strip. Getting the details like this right really does contribute to the overall integrity of the completed structure.

 

B-17-12-27 Here’s the battery deck section all assembled and ready for the next step in fuselage construction…

 

B-17-12-28 which turns out to be adding all those fore-and-aft stringers. I’m doing this exactly according to the original kit instructions. All the stringers are 3/32” sq. balsa and they fit nicely into the laser-cut notches in the various formers.

 

B-17-12-29 This is not a stringer, but it’s made of the same 3/32” sq. balsa. This strip is going to bend to match the curvature of the balsa sheet wing saddle and fit into cutouts provided in then relevant F- parts.

 

B-17-12-30 When that’s done it looks like this. I chose to use Deluxe Materials Roket Hot (fast) here and hand-hold the joints for the few seconds required for curing to avoid having to clamp or tape this delicate part of the structure.

 

B-17-12-31 Again per the original instructions I’m adding wing saddle base plates cut from 1/16” balsa sheet, again using Roket Hot.

 

B-17-12-32 As viewed from the top down, the center of the fuselage structure as it exists so far looks like this. In the foreground (at the bottom of the image) is the completed “battery box” and below/beyond it you can see the upper/inside surfaces of those wing saddle base plates I just put in. BTW: the tail is pointing to the left.

 

B-17-12-33 Same game looking aft across the box…you can see where I have added the “header” (per the kit) inside the F-7 former structure.

 

B-17-12-34 The purpose of the F-4 and F-7 former headers is to provide gluing area for the plywood wing bolt plates. This is the forward plate seen from below and behind as it attaches to the F-4 header.

 

B-17-12-35 It’s time for some preliminary sanding. I’m cleaning up the fuselage structure between F-4 and F-7 where the wing is going to fit.

 

B-17-12-36 When I’ve finished that the wing saddle area looks like this upside-down…

 

B-17-12-37 …and turned right-side-up it looks like this.

 

B-17-12-38 And… “First Contact”! I have dry-fitted the wing to the fuselage so we can all have a look at it. The next step will be to establish wing-to-fuselage alignment and install the wing mounting bolts, again as per the original instructions.

See the entire build series: Building the Balsa B-17-F