Airfield Models - How To

Mount a Scale Pilot Bust

May 03, 2015



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Airfield Models (http://www.airfieldmodels.com/)How to Mount a Scale Pilot Bust

Most pilot figures mounted in model aircraft are busts and not full figures.  I've seen busts mounted a variety of ways.  The simplest way is to just glue it in.  One problem with that approach is if the pilot comes loose in an enclosed canopy you will either have to perform surgery or just live with a pilot bouncing around the cockpit.

Glued pilots can fail for several reasons:

  • Incompatible glue was used.  Many glues peel off plastic easily.
  • Glue softened in hot sun.
  • Hard jolt popped pilot loose (glue joint failed or the bust busts).

This pilot by Aces of Iron is exceptionally rendered but is hollow molded resin.  The casting is thin and very weak.  I wouldn't even consider just gluing this pilot in place because I don't think it would take much of a shock to tear the molded base loose and pretty much destroy the bust.

Caution!  Never pick up your plane by the pilot.  This pilot gets mounted to a removable hatch and it's natural to want to grab the pilot to remove or replace the hatch.  Discipline yourself not to do it because the bust just isn't very strong.

Also see

 
 

Mounting the Bust

The bottom of the pilot needs to be removed so that a more substantial base can be added.
The best way is to sand it off.

Be careful when sanding to prevent chipping the edges when the base is sanded through.  In most cases it will let go in some areas before others which leaves those areas more vulnerable.

To sand evenly, rotate the pilot every so often.  If you sand with more force on one edge than the other it will be more even.

Caution!  Don't sand the bust at an angle to make the pilot look like he's leaning.  It doesn't work that way.  He'll look awkwardly tilted not leaned.  Shoulders stay fairly level and the head is mostly vertical when a person leans.

Ask someone to sit across from you and lean as if they're trying to look around you to see something.  Note how they look.  Don't mention the shoulder thing to them until after you've made your observation.

I managed to chip part of the back of the pilot.  It's covered in this photo but is bad enough that it will need to be filled.

Clean up the inside edges by scraping with a knife.  Just remove the flash and then stop.

Place the bust on a piece of 1/8" lite ply.  This will be the base glued into the bust.
Trace around the bust being careful not to distort the bust while doing so.  The wall thickness at the base is minimal and can be deformed by the pencil as you trace around it.
Make a second line inside to adjust for the wall thickness.  The wall thickness is not uniform all the way around so there's some trial and error work here.

Use a hobby knife, scroll saw or coping saw to cut along the inside line.

Check the piece on the bust to see where adjustments need to be made.

You can see where the casting is paper thin in the back and chipped when the bottom was being sanded off.

Mark the areas with pencil.  Trim excess wood away using a sanding drum in a Dremel or sandpaper wrapped around a dowel.
After several fittings the plywood base drops into place.
Glue some 1/8" reinforcing pieces on the base to thread studs into.  I used knock outs from lite ply ribs.
Drill for whatever tap you will use.  I am going to use 6-32 nylon bolts.
Tap for the bolts.  You want to do this type work before the base is glued into the pilot so that you don't risk damaging the pilot.

Lite ply doesn't hold a thread very well so I hardened the threads with some thin CA.

Put the base on something flat with the reinforcing pieces down.
Clean the base of the pilot thoroughly where it will be glued to the base.  I went ahead and washed the pilot using warm water and tri-sodium phosphate to get all the dust and oil off the pilot.  It will need to be cleaned again before painting.

Place the pilot over the base.

Because my workbench is glass, I can see if the base is flat on the table.

Gently squeeze the pilot to grip the base.  Pick up the pilot being careful not to let the base shift.  Put a few drops of CA in places where the base contacts the pilot.  Let the CA cure before releasing the pilot.  Spritz a little accelerator to speed things up.

You don't need a lot of CA.  It's just to spot the base and prevent it from moving.

Allow the CA to fully cure before this step.

Mix up some 30 minute epoxy.  Brush the epoxy on the base around the perimeter and inside the bust.

Mix some micro-balloons into the same batch of epoxy.
The micro-balloons should be about the consistency of peanut butter.  You don't want to use any more micro-balloons than necessary because they weaken the epoxy.  The idea is to add just enough micro-balloons to prevent the epoxy from running.
Spread the paste around the base and inside the bust to create a fillet.  I repaired the chipped base of the bust with the same batch of micro-balloons.  I made it oversize and then filed and sanded it after the resin was fully cured.

The base will be as strong as it's going to get.  It's not going to come loose without destroying the bust.

When the epoxy is fully cured, sand the base flat again ensuring that the plywood sits on the bench without distorting or stressing the bust.

At this point you can do whatever clean-up work is necessary on the rest of the pilot to prepare it for paint.  That means removing flash, filling or sanding away imperfections, etc.

Sometimes it's nice to have a template to drill mounting holes in the model that match the pilot. Normally I use the base plate that is glued inside the pilot to locate the mounting holes in the model before I glue the base plate into the pilot bust.

In this case I have been commissioned to paint the pilot but I'm not building the model.  I made a template for the builder to use to locate the mounting holes so he won't have to measure the pilot.

Before the base was glued in the pilot I used it to drill holes in a piece of lite ply that will be the template.

Drill matching holes in the template and bolt the pilot to it.  Trace around the pilot. Insert studs into the pilot base or just bolt it to the template.  Trace around it.
Cut out the template. Cut it out and there's your template.  I cut a little oversize to give the builder some wiggle room.
 
 

Reinforcing Thin Areas

This isn't something I would think should need to be done normally.  Mike called me up one day to tell me that the pilot I painted and installed in the Eindecker I built for him had almost completely lost his head.

When he show up at my shop I saw what he was talking about.  This pilot has some very thin areas.  One of those areas is in front of the pilot at the base of the collar.  The bust had split almost all the way around.  The only place where the pilot's head was still connected was at the back of the neck.

I reinforced Mike's pilot exactly the way shown below.  The difference is this one is being reinforced prior to painting.  At the time of this writing, the repair on Mike's pilot is only a couple weeks old so there's no way to tell at this point how long the repair will hold up.

Hopefully the folks at Aces of Iron will correct this problem.

The pilot in Mike's Eindecker almost lost his head.  There was maybe a half inch of material in the back holding it on.  It cracked in front all the way around both sides just under the collar.

This pilot will probably do the same thing.  The resin is very thin in this area.

Another view of the thin resin below the collar.
I could have done the reinforcement before gluing on the bottom but when Mike informed me of the problem the base was already glued on.

The cutout was easily made using a Dremel.

The arrow shows the crease at the base of the neck (front of pilot) which is the only area we're concerned about here.

Chopped fiberglass is added to 30-minute epoxy to reinforce the area.

Mix the epoxy first.  Then add just a small amount of the chopped glass.  Mix it thoroughly to break it apart into individual strands.  If it's too thick you added too much or you spent too much time and the epoxy started to thicken.

If it's too runny then you didn't add enough or you haven't broken the strands down enough.

You will have to use chopped fiberglass a couple times to get a feel for how much to add to the resin.  Better to start with what you think will be too little.

I used the mixing stick to put the resin/chopped fiberglass mix into the bust.  I dipped the stick in alcohol so that the mixture wouldn't adhere to the stick and pull away.

Once it was pretty well in place I put on a latex glove and dipped my finger in alcohol to press the mixture in place and shape it around the crease particularly the other side where I could not see what I was doing.

Also see

 
 

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Copyright 2007 Paul K. Johnson