Airfield Models - Installing Robart Hinge Points

Join Wing Panels of a Flying Model Airplane

May 03, 2015

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Back to Joining Wing Panels


Airfield Models ( the Foundation for Properly Aligned Wing Panels

The ultimate goal when joining wings is to have them align correctly in all respects, have the correct dihedral and have a join that is capable of withstanding flight stresses imposed upon it.  All of these things are vitally important if you want your model to fly properly.

Aircraft with twisted wings will fly in most cases, but they are also speed sensitive.  What that means is that if the model is trimmed for straight and level flight at one speed, the model will roll in one direction at higher speeds and in the other direction at lower speeds.

If the wing is absolutely straight, the speed of the aircraft will not bank the model.

Presumably, the designer engineered the wing so that all you must do is build it properly.  Improper assembly, poor fitting joints or a poor glue bond will significantly weaken the wing.

Proper alignment entails several things:

  • The angle of the root ribs must be correct to provide the proper dihedral.

  • When the wings are mated they should match the plan view.  That means all outlines should line up directly over the plan without unintentional sweep.  This is a mistake that can easily be sanded into the wing root.

  • The incidence of each panel should match exactly.  Building two absolutely straight panels will be for naught if the panels are joined such that they are twisted.


Sanding the Wing Root

Sanding the wing root is fundamental to joining the wings properly.

Sand the root of the wing using a good, flat sanding block to bring everything flush.

Do not rush this step.  If it takes 5 hours to get it right, then it's 5 hours well spent.

The top of the root rib will be canted toward the wing tip if the wing has dihedral.  Do your best to maintain the correct angle while sanding.

You must also take care not to sand in unintentional sweep.  Go slowly and check your work often.  Put the panels together over the plan to ensure one panel or the other isn't being swept forward or backward.

Stand the wings on their root to see if the roots are sanded to the same angle. A quick way to find out if the angle of the root rib is the same on both panels is to stand the panels up on their root.

Even a small difference will translate to a large misalignment over the length of the panel.  For example, both panels shown here are off by less than one degree each.

More work to do...

Use a template or adjustable triangle to check the angle of the wing root. Draw a centerline down the trailing edge.  You'll need it when it comes time to install hinges.

An Adjustable Triangle has a lot of uses at the drafting table and in the shop.  I use mine for many purposes such as setting up the tables on my power tools.  It's much more accurate than built in gauges that are almost never right.

If you don't have an adjustable triangle, you can make a template from card stock.

This step isn't necessary, however.  You can lay the panels on the board and prop up the tips to the correct height.  If the root ribs mate properly and the wing lines up with the plan then you're done.  If anything isn't right then more sanding is necessary.

I use this method with wings having one straight edge because it's faster than jigging the panels on the board.  If either the leading edge or trailing edge is perpendicular to the root rib (in plan view) then I can use a large drafting triangle to ensure that edge is perpendicular to the board.

Sand the wing root until both wings are at the same and correct angle. This is as close as I'm going to get these panels.  Although the tips are off by maybe 1/16" the angle is so small I have no way to measure it accurately.

When the panels are jigged on the board they will mate very well with the tips propped up to the correct height.



How to Join Multi-Panel Model Aircraft Wings
Matching Multiple Wing Panels

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Copyright 2004 Paul K. Johnson