Airfield Models - Wing Construction Example

Miscellaneous Internal Wing Details

May 03, 2015



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Airfield Models (http://www.airfieldmodels.com/)Miscellaneous Wing Details

To this point I have spent less than an hour building this wing.  The previous three parts were done in one evening and then the structure was left to dry.  This page will cover some items that must be installed before sheeting the wing.

In the previous part I goofed.  There is one more thing I should have done before leaving the wing to dry.  It wasn't a big deal and I managed to work around it, but it could have been planned better.

 
 
Glue in the wing bolt support blocks.  Ensure they will be flush with the side of the wing that the bolt heads will tighten to provide maximum support. This is where I goofed.  These balsa blocks are about 3/4" square and will be the wing bolt support blocks.

I should have glued these in place before leaving the wing for the night because I have to wait for them to dry before I can sand the trailing edge to receive sheeting.  Like I said, it is not a big deal.

Here they are being test fit.  They should fill the entire area (top to bottom) to provide the best support for the nylon wing bolts.

Wing bolt support blocks firmly clamped while glue dries. The wing bolt support blocks glued and clamped in place.

This step took 5 minutes

Elapsed time 55 minutes

Tools used to shape sub-leading edge - a razor plane and long sanding block. The sub-leading edge must be faired into the ribs before sheeting the wing.  This applies to wings that have leading edge sheeting (D-Tube) as well.  The only tool necessary is a sanding block.

I use a razor plane to bring the sub-leading edge roughly to shape.  However, it is easy to gouge the ribs if you are not careful.

Proceed slowly and especially watch the angle of the plane.  The sole of the plane should be a tangent to the forward most part of the rib.

Sub-leading edge roughly planed to shape. It is difficult to see here, but the sub-leading edge is still slightly higher than the ribs.  Man I wish I had a decent digital camera.

This is where I stopped planing the sub-leading edge in preparation for final sanding.

Use masking tape to protect ribs while sanding sub-leading edge. I use masking tape to protect the ribs while sanding the sub-leading edge.  The tape will prevent the part from completely fairing in to ribs.

When the sanding block starts cutting through the tape at the forward portion of the rib, I remove the tape and carefully finish sand.

Sand sub-leading edge from back to front to prevent the sanding block from chattering. The ribs are not well supported side to side.  Anyone who has attempted to sand back and forth spanwise has experienced the sanding block "chattering" which is not a good thing.

Instead of sanding spanwise, sand from back to front, but do not go back and forth.  Lift the sanding block, place it back on the masking tape covered ribs and pull the block forward over the sub-leading edge while following the contour of the rib.

If you start cutting through the tape then replace it unless the tape is being cut through directly behind the sub-leading edge.  In that case, remove the tape and finish sanding while being careful not to remove material from the ribs.

The sub-leading edge sanded to match the contour of the ribs. Here is the sub-leading edge after finish sanding.

This step took 17 minutes

Elapsed time 1 hour 12 minutes

Sand the trailing edge to match the contour of the ribs. At this point I decided the wing bolt support blocks had dried long enough.  Titebond grabs in about 20 minutes.  If this were wing sheeting, spars or something that could cause the wing to warp then I would have left it to dry thoroughly before proceeding.

I planed down the trailing edge and the blocks at the same time and then sanded in the same manner as the sub-leading edge.

Again, masking tape protects the ribs.

This step took 14 minutes

Elapsed time 1 hour 26 minutes

Hinge support blocks. The trailing edge is only 1/4" deep.  There is not a lot of material there to hold the hinges securely.

Lightweight blocks are glued in front of the trailing edge to give additional support to the hinges.

Determine the size of the block by measuring the hinge and subtracting the thickness of the trailing edge.  Add a little bit onto that so the hinge is fully enclosed in wood.

Hinge support blocks clamped in front of the trailing edge of the wing. I eye-balled the hinge support blocks locations.  Their placement is not critical as long as they are mostly centered top to bottom.

This wing has separate flaps and ailerons.  I will be using three hinges in each (twelve hinges total).

This step took 9 minutes

Elapsed time 1 hour 35 minutes

Mark the location of the hinge support blocks so you remember where to install the hinges. Draw reference lines to represent the hinge block locations.  The hinge slots or holes, depending on the type of hinges used, are not cut until after the wing is sheeted and the blocks are no longer visible.

I will be using Robart Hinge Points.

I used to rely on my memory for things like this.  It didn't take long for me to discover that my memory isn't all that great.

Now I take notes or mark things so I can remember what I did.

I did not time this step.  Let's say two minutes just for fun. Timing things adds to the time it takes to do the thing.

 
 

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Adding the Sub-Leading and Trailing Edges
Sheeting a Built-Up Wing

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Copyright 2003 Paul K. Johnson