Airfield Models - Fuselage Construction Example

Building the Inner Fuselage Side Structure

May 03, 2015



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Airfield Models (http://www.airfieldmodels.com/)Building the Inner Fuselage Side Structure

Building the inner fuselage sides is another task that is not particularly difficult.  It is simply a matter of measuring carefully.  Often there are pieces that will determine the alignment of formers.

If these pieces are not attached identically to each fuselage half then the formers will not be square to the centerline when the fuselage sides are aligned.

Many slab-sided fuselages such as this one have square or triangle stock longerons.  Excessive glue or poorly aligned longerons will result in additional sanding necessary later.

 
 
Fuselage side and aircraft plywood doubler. The forward fuselage doubler is cut from 1/64" plywood.  The wing saddle area on the doubler is left oversize and will be sanded to final shape after the doubler is glued to the fuselage side.

Epoxy glue is used to minimize the tendency to warp.  Also, water-based glues can take a long time to dry when used for laminating.

After the doubler was positioned, a piece of waxed paper was placed over it and then a great deal of weight was placed over the doubler until the glue cured.

Plywood doubler glued to fuselage side. The wing saddle area has been shaped and former positions have been transferred to the inside of the doubler.
Longerons being glued on to fuselage sides. A straight-edge is used to align the longerons inside the fuselage.  This will help with alignment later as well as minimize sanding.
Vertical uprights being glued to fuselage side.

Vertical supports are used to prevent the fuselage sides from cupping.  They add a lot of strength across the grain and their weight is negligible.

A triangle is used to ensure they are square to the bottom of the fuselage.

Weight placed on fuselage side while longerons and uprights dry. After gluing the longerons in place they are weighted down to dry.

Weight is added a second time after the vertical pieces are added.

Fuselage sides being sanded to a perfect match. The fuselage sides are taped back together and block sanded to an exact match.  Because of the care taken during assembly, only a light sanding was needed to remove excess glue.

I used my long sanding block used for truing edges of sheets.  Instead of moving the sanding block over the work, I did just the opposite after clamping the block to the workbench.

Marking aft fuselage prior to sanding bevel. The fuselage side is jigged up on the board so that the bevel can be marked at the tail post to bring the fuselage sides together.

The first step is to determine how thick the fuselage should be at the tail and mark half that measurement on each fuselage side from the outside.  In other words, if the fuselage is to be 1/4" thick at the tail, then measure 1/8" from the outside and mark the bevel at that point parallel with the fuselage center-line.  In this case the tail post is 3/8" wide, so each side is 3/16".

Line drawn to show how bevel is sanded. The fuselage side is trimmed to the line shown.  The line is drawn on one side only.  The sides are laid next to each other and the line is extended across the inside.  Both sides are sanded up to the line.  It does not hurt to put a piece of appropriate diameter music wire at the tail post to act as a sanding stop.

Sanding to the bevel is not difficult but take your time and stop to check your work frequently.  If you sand too much away you can add a shim in between the sides to bring back some thickness.

Bevel sanded inside aft fuselage. The tail end of the fuselage sides after they have been sanded.
 
 

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Laying out the Fuselage Sides
Preparing the Formers

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Copyright 2003 Paul K. Johnson