The Return of the TigerKitten (5)

I chose to begin laying out the first fuselage side frame by positioning the laser cut balsa wing saddle and landing gear mount reinforcement. These two parts are positioned in reference to a 3/16" sq. balsa upright which I have fitted in place here. Thin (instant) ZAP is the adhesive of choice here as it allows me to locate and pin each of the parts involved in exactly the position I want, then add adhesive.

Here I have fitted the top longeron to the 3/16" sq. balsa upright that supports F-1, as well as the 1/8" x 3/16" balsa diagonal brace that lies directly behind it. This is an example of the way you should make all the joints in a model structure fit... it doesn't make sense to have the advantage of precision laser cut shaped parts and not have the joints you fit yourself match that level of accuracy.

I have all the longerons, uprights, and diagonal braces in place along with the laser cut components...this defines the structure of the side frame.

The basic fuselage structure consists of two identical side frames connected by various cross members and formers. The best way to to be sure both of the side frames are actually identical is to build one directly over the other. That's what's going on here. I have completed the first side, sanded the structure smooth with the good old sanding block, and covered it with a new sheet of plastic wrap while it is still in place on the plan. (It will be necessary to move and reset the pins that are holding everything in place, and then insert new pins as necessary to hold the new/top parts as they are assembled.) Here I have the laser cut wing saddle in place to begin constructing side two.

Here's another quick look at the way the various 3/16" sq. balsa longerons, uprights, and diagonals are going to fit against the wing saddle as I build side two in place over the first side frame.

The trick to building really accurate fuselage side frames is block sand them aggressively while they are still pinned to the building board. Here I am using 80-grit production paper, which is coarse enough to cut through all the hard spots of glue neatly without compressing the balsa. The important thing here is to sand off enough material to get a flat, true surface. Don't leave ridges or low spots. Here I'm sanding the second side, still in place. When it's done I'll remove it along with the top sheet of plastic wrap and repeat the operation with the first side.

A 1/64" plywood doubler is added to the inside face of each of the side frames before we go any further. These will be laser cut parts in production kits, so I have not gone into detail on making them. I used ZAP A GAP for this operation to give me time to spread an even layer of adhesive over every part of the side frame that is going to contact the doubler.

The side frames are assembled upside down over the plan in order to take advantage of the flat, straight top longeron as a reference to keep the rest of the structure square. This is the left side as seen from what will become the inside of the fuselage. I'm using an actual drafting square to get the alignment right at this stage before I proceed further. The side frame is pinned through the top longeron to the building board in several places.

I have added the laser cut plywood landing gear mounting plate and the rear wing mounting bolt plate ( F-2 and F-6) as well as the 3/16" sq. balsa crossmembers that correspond to their positions between the top longerons.This is probably the most critical part of the fuselage construction where correct alignment is concerned.

Here's another look at the basic fuselage framework all squared up and glued back to the wing trailing edge station. Notice that I have not yet made any attempt to pull the sides together at the tail.

Got it right! I'm double checking that the fuselage side frames are assembled square to each other and the building board (which is my reference for all alignment) before I move to the tail.

The vertical members at rearmost point of the fuselage are 3/16" sq. balsa. When they are drawn together and glued, they will have to match the width of a 1/4" thick rudder. It's necessary to bevel the inside face of each one so the final outside dimension will be 1/4" , not 3/8". I'm using an 80-grit sanding block for this, with the assembly still flat on the building board.

The rearmost uprights of the fuselage side frames form what is also referred to as the tailpost. In the last step I beveled them to match the 1/4" rudder leading edge. Now I'm using clothespin clamps to hold them in exactly the right position while I use fast ZAP to glue the joint.

All the fuselage crossmembers are 3/16" sq. balsa. Cut them in matched pairs to align the side frames with the plan. They all get the same ZAP treatment once they are in place.

Check the assembly AGAIN to be sure it's square. If you make a mistake in alignment here, it gets harder to fix with each successive step you complete.

I'm using a bubble level to be certain the fuselage frame is squared off before I go on to work on the the wing attachment structure.

Prior to positioning the wing on the fuselage assembly I measured and marked a centerline equidistant from each tip. I also marked a center point on the leading and trailing edge station formers. With those matched up, I used the long metal straightedge as an aid in setting the wing at exactly a right angle to the fuselage.

I'm using an older model Robart incidence meter to check that the wing is set at an angle of three degrees positive. Remember that the entire airplane is assembled upside down, so the meter will read out at a negative value.

I used the pre-drilled holes in F-3 to mark the wing leading edge at the center and drill holes for the 1/4" dowel mounting pegs. These extend all the way back to the main spar doubler and must be glued securely. I used ZAP A GAP applied to the inside of the opening before inserting each dowel.

Here's a look at the inside of the nose structure so far. I have added pieces of 3/8" quarter-round balsa as corner gussets along the back of F-1

The formers that create the raised portion of the rear fuselage (the "turtleback") are added now. I am using a square to make sure F-7 is perpendicular to the top longerons.

This is a better look at F-7 through F-11 in place.

The top stringer is a piece of 3/16" sq. balsa, which is intended to lie straight as seen from the side. I'm using a steel ruler to check ...this is where you need to trim the top of one or another of the formers if necessary to keep the stringer from bowing or bending.

The top stringer is glued in place. It ends flush with the rear face of F-11.

The top center rear deck stringer is 3/16" sq. balsa. All those on the sides are 1/8" x 3/16" balsa, and it's best to add them one at a time, alternating from one side to the other to minimize the chance of pulling a twist into the structure. I used fast ZAP here, holding the stringers in contact with each former in turn to get the alignment exactly right.

The best way to locate the position of the side stringer is to measure off the plan and mark a location where the stringer crosses each upright in turn.

The fuselage side stringers rest on the top of each of the uprights, but are recessed to lie flush with the tailpost.

All the rear deck stringers are in place now.

Here the left side stringer has been installed, using the locating marks I made earlier.

The surface created by the longerons, F-1 former, and the side stringer must be sanded to provide a mounting base for the side sheeting that comes next. Notice that the surface is not flat...the stringer creates a bulge that will cause the sheet to assume a shallow convex curve.

The fuselage side sheet is a complex part that was not laser cut in my early kit. I'm not sure how this will be presented in production kits, so I'll show you how to mark and cut it yourself. I cut a piece of 1/16" balsa sheet from a 1/16" x 4" x 36" sheet long enough to extend from F-1 to the rearmost point on the side sheet. Here I am using the top edge (along the top longeron) as a reference, as it provides the only straight line I can use as a starting point. I have used clothespins as clamps to hold the top edge of the sheet to the longeron.

With the clamped-up assembly turned over I can mark the cutting line along the wing saddle and the rest of the bottom edge of the fuselage onto the side sheet blank.

Without cutting the plan it's hard to mark that inside cutout curve onto the sheet blank. I traced the curve off the plan onto a sheet of ordinary copy paper (you can see through it OK if it's held tight against the plan), then cut out the pattern. Here I am tracing the resulting curve pattern onto the side sheet.

This is the side sheet blank with the inside curve marked, ready to cut, resting in place on the fuselage side where I'll ZAP it pretty soon.

This side sheet is going to have to assume a gentle compound curve to fit tightly against all the underlying structure. The easiest way to get a sheet of balsa to do this is to wet it with a light spray of water ...only on what you want to be the outside surface of the bend. The sheet will automatically curl away from the wetness AND become more pliable at the same time.

ZAP A GAP is my adhesive of choice here, as it allows me to spread an even layer of glue over all of the longeron, former and stringer surfaces where the sheet is going to stick.

It's easy to press the wet sheet into place all around the edges where you want it to stick using the palm of your hand. ZAP A GAP will grab and hold a joint like this in ten seconds or so.

There are lots of places in the TigerKitten fuselage assembly sequence where the edge of a part may not seem to fit right away. Don't sweat that...it's all planned to come out right. Here the best way to blend the rear point of the side sheet into the rest of the structure was to design in a longeron cap of 1/16" x 3/16" balsa, which you see being fitted here.

One of the features that gives the 'Kitten such a finished look is these stringer inserts, which are provided laser cut slightly oversize to permit you to trim and bevel each one for a perfect fit between each pair of stringers after YOU have assembled them. You can see where a bevel needs to be sanded into this one.

I have sanded a bevel into each of the edges of the insert that will fit against the two adjacent stringers...you can see how it's going to slip right into place.

I left just enough material on this insert to give a tight press fit...now thin ZAP is the perfect adhesive to keep it there. All the rest of the stringer inserts go in just the same.

All the stringer inserts are in. You can see that the material selected for them leaves some extra thickness to be sanded away, allowing a perfect fit.

Here's what the inserts should look like when you have the entire surface of the assembly sanded.