Tutorial Advanced - Orta Saint - Hubert G - 1

[Boomerang]

A terrific tutorial Fraser.

Well Done.

Cheers

Gordon

[Gearup]

Thanks guys. I am getting back into the swing of building, recording and writing about the build. More to come.
Fraser

[Gearup]

Shaping the horizontal stab and vertical fin

The stabilizer and elevator are generally a non airfoil shape on small aircraft like the Horta. The fixed portion of the stab is usually flat with a rounded leading edge while the elevator tapers to a fine trailing edge from the hinge line.

Mark the middle of the trailing edge of the elevator. Now mark the line on the top and bottom of the stabilizer to define the hinge line of the elevator. Mark guide slashes no the upper and lower faces of the elevator.

Using the 80 grit stick, taper the elevator top and bottom from the hinge line to the centre of the trailing edge. The tail surfaces are only about 1/16 thick so it does not take a lot of effort. Also since maple was used for the parts here, it can be sanded to a thin taper. Be careful, as it can get really thin and sharp!

Lightly sand a half round along the leading edge

To ensure the hinge line can be found later, I lightly notched the tips with a razor blade. Give the parts a final sanding with 220 grit.

Use the same method to taper the rudder on the vertical fin.

[Gearup]

Fuselage shaping

Shaping the fuselage is done with pretty much the same tools. I don't use the block plane as the fuselage is small and more sculptural in form.

Print out a plan so that a template of the fuselage cross section can be cut out of either card stock or paper then glued onto cardboard. This airplane pretty much only needs the one template at the section between the two cockpits. The nose is circular and the aft fuselage is pretty much rectangular.

Use the centre and longitudinal small drill holes to mark reference  lines on both sides and top and bottom of the rough cutout. Don't press hard enough to groove the wood, a light touch with the HB pencil is good.

It is not too critical where to start carving the shape, but I like to start at the forward fuselage. My eye tends to fill in the detail from nose to tail better.

Make faceting cuts with a knife to start the radius of the fuselage at the engine cowl area and nose. Use the template to see that you are removing material in the right places. Now continue to remove material with the flat 80 write sanding stick. Again, move the stick like a violin bow across the grain of the wood to gradually remove material.

Work all areas of the model now to ensure symmetry and fair lines. If detail areas need work, then a knife can be used to work that area though. Re-mark the centre lines as required if they fade.

Do not remove the material at the centre and side guidelines as the profile shape of the fuselage was set when you roughcut the block and sanded to the edges earlier on. Removing the lines with a blade or heavy sanding now will change the shape of the model substantially. If this happens, it can be fixed as will be seen later.

[Gearup]

Checking for fair

Fair lines are a term used to see that the shape your are creating is smoothly curved and looks smooth to the eye. Take a long flexible stick and bend, by hand, a long curve like a bow into it. If you sight along the length of the stick it should be a nice curve without noticeable bumps or dips. That is a fair curve.

It is used in boatbuilding (such as a kayak or dingy) by looking along the length of the boat and sighting the curve as you move along the hull. If the curve of the part you are looking along makes a sudden bump or dip that is not part of the plan, it is out of fair. Removing or adding (filling) material is done to get the line back to fair.

This is also how the shaping of models works. The side of an airplane may start as a fair curve at the nose, flatten at the doors passenger area, then curve back to the tail. Or there could just be a straight line that smoothly transitions into another straight line. In other words, the fair line is defined by the shape fro the plan. If the line is not fair and it should be compared to the plan it can be fixed.

As can be seen in (IMG_0128.JPG), I under cut one side of the fuselage and it is too flat. I'll add a piece of wood to get the line back fair again. Also in (IMG_0127.JPG) there is a divot that will need filling to make up for the errant cut I made.

[Gearup]

Adding material to re-establish the shape

For the large flat area where I cut too much material at the very start, I will glue a thin strip on using carpenters glue. Once the glue dries I carved and sanded the repair down to a fair curve to match the other side. Checking the model to the plan now shows that it is the right shape and symmetrical.

Don't forget to redrill the side ref hole that is now covered by the repair. Drill from the opposite side using a small pin drill.

[Gearup]

Mark out the cockpits

Refer to the drawing to get the cockpit locations and shapes. I free handed the cockpits and shaded them with pencil for further shaping to come. The plan does not show the cockpits too well from the top, so the opening shapes extrapolated from the side views.

[Gearup]

Aft cockpit headrest
All of the pictures I could find of the aircraft that I am modeling show that it had a headrest for the aft cockpit. The plans did not show it so I added one to the model.

I drew the part into a 1/4" thick block and cut the top plan view shape out. With the part double taped to a popsicle stick I rough carved it the sanded it to shape 
I'll glue it in place after I have carved out the cockpits.

[Gearup]

I just realized that i had not put a photo of the aircraft I'm building here.

So here is the actual pilot and aircraft and another with the pilot (in the new colours) discussing something with a (probably) mechanic.

[Boomerang]

Excellent tutorial Fraser . Easy to follow.

Between Lou and yourself the Tutorials should enable anyone to take up the challenge and turn out a model to be proud of.

Well Done both of you.

Cheers

Gordon

[Gearup]

Thanks Gordon. Even if this model never gets built by another modeller, the techniques are transferable to almost any model.
Fraser

[Gearup]

Cockpit carving

Caution: You will be using sharp tools with small parts. Ensure that the work is held securely in a small vise with padding to prevent damage to the outside of the model. Sharp tools will cut easily. If you are exerting yourself to perform the cuts, re-evaluate the sharpness of the tools. Never cut towards your body or use your body to support the work. Small cuts using the thumb and fingers to control the blade and amount of travel is important. Don't use stabbing actions with a folding knife.  Always look where the blade will go if you slip or the part splits during the cut.


Now is a good time to carve out the two cockpits. It is tempting to use a large drill to hog out the material, but this would probably end up in grief if the bit catches and destroys the model so far. The walls get too thin and there is no real good way to support the fuselage for heavy drilling at this stage.

A good carving knife and a small corner gouge are what I used. The knife is a folding pocket knife by Flexcut called the Whittlin Jack. The two different blades, detail and roughing, are polished and sharp right out of the box. It is my go to carving knife. The "V" gouge is also by Flexcut and is a palm style with interchangeable handles. They are not inexpensive tools, but will last a long time and keep a keen edge.

A good Swiss army knife with two smaller blades will work quite well.

Use the tip of knife to score vertically  around the cockpit outline to a depth of about 1/8".

Now cut inside that scored line about /16" inch inside of the cut starting across the grain at either end of the cockpit. On this cut, angle the blade over about 45 degrees so the tip will intersect the bottom of the previously made score cut. Don't try to do the entire perimeter around the first score line. Work the tip of the knife for a short distance across the grain to remove a small sliver of a wedge from the inside of the cockpit. Basically you are doing a chipping cut.

Make the same cut at the opposite end of the cockpit. Now cut using the same method on the sides of the cockpit. Try to avoid prying the pieces out with the tip of the knife, but try and get a chip to come away cleanly.  Leave the side walls a bit thicker as it will be easier to remove more than fix the side wall if it breaks out.

Keep working around the perimeter to get the waste removed from inside the cockpit until it gets awkward to use the knife only. Now switch to the small 'v" gouge to start removing the material from the centre. I keep pushing it into the waste wood to break it up and remove the pieces with either the knife or gouge as required. Again, don't try to remove larges amounts of wood at a time or go too deep with the tool.

Use a stick with a mark about half the depth of the fuselage at the cockpit to estimate the depth of the cockpit.

When you are deep enough, use the tools to clean up the cockpit to the shape you drew at the start. Course sandpaper on a dowel can be used. You can also use a dremel tool with a small sanding drum to finish it out. On thing to be careful with a dremel is the tendency to grab the adjacent wall when moving it. This results in the sanding drum  rapidly running around the inside of the hole you are trying to finish.

Next we'll look at the addition of a paper liner in one of the cockpits to refine the shape a bit better

[Gearup]

Paper filler in aft cockpit (optional)

I was not quite happy with the shape of the seat area of the aft cockpit so I decided to give it a paper liner secured with automotive glazing putty.

Actually you can see the paper in place on the previous photo 0165. You will also notice in the pictures that I have added filler on the fuselage. So the pictures are a bit out of sequence but....well look at filling the fuselage in a bit.

I cut a small piece of regular copy paper to form a rounded seat back for the aft cockpit.

I curled it and kept trimming it to fit where I wanted it. To keep it's shape, I used wood hardener on the paper. This essentially saturated the paper and it became like a composite material. Other stuff could be used as well. Clear nail polish or thick cyanoacrylic glue will work as will carpenters glue. The idea is to create a form that will be held inplace with the auto glazing putty.

Once the coating has hardened and the paper is now relatively stiff, it is held in place with the auto glazing putty. Plastic wood will work as well.

With the paper form removed, apply a small thickness (approximately 1/8" max) of putty to the to the back of the paper and set it into the cockpit back. Press the paper in place until you are satisfied with the position. Ideally there should be some squeeze out. Allow it to set and and the sand top of the paper flush with the cockpit. If there is a lot of paper or filler exposed, remove the bulk with a knife first. When sanding the paper top edge, full the sanding stick towards the wood walls to prevent tearing the paper away.
If needed, add more filler for any gaps or hollows remaining, sanding as necessary.

Filler can be used inside the cockpits to smooth out the carving marks if required. A sanding stick on a dowel will help clean up the cockpit and make them smooth.

[Gearup]

Filling defects with automotive glazing putty (or plastic wood filler)

I use automotive glazing putty to fill and fair my models. It fills small to large areas and sands beautifully. It dries pretty fast so many thin coats can be applied and it adheres well to wood, paint and sealers.

A few drawbacks. It scores ( scribing a line) well, but differently than the bare wood. It can chip during the scoring process especially across grain. Also it has a strong smell. Its solvent is acetone and the filler is likely styrene based. It therefore flammable. Since only small amounts are used in modeling, I find it is ok to use in my shop. If you are in a smaller room, ensure you have ventilation.

However it comes in a nice large toothpaste tube with a screw cap. I have used the same tube for a few years, so it keeps well if capped.

Tools.
I have a set of tools used for shaping clay pottery. They are quite cheap ($25 CDN on Amazon, Yasumai 12 Pcs Carving Knife Tool kit Pottery).  They are stainless steel and will last forever. I also use spatulas made from plastic gift cards, dairy product containers or wood craft sticks.

To fill holes like the alignment holes made earlier it works very well. I use the square end spatula to press a small amount into the holes. It only takes a match sized blob to work into the hole, Smooth it off with the spatula leaving it slightly high at the hole. This will allow for shrinkage. Keep in mind the hole should be filled to least 1/8" into the depth. On a through hole like on the wings or other thin sections, it should fill all the way through and pop out on the opposite side.

When the filler dries after about 10 minute, lightly sand the excess filler off until the bare wood is left around the filled hole. As you sand you will notice the filler goes from dark red to pink (or lighter red). When the filler material around the hole has been removed to just "coloring" the surrounding wood grain, you will probably see that the actual filled hole is still dark red. This is good because it means the filler is below the surrounding wood and has not been touched by the sanding.

Apply another thin coat of filler at the hole and again leave it slightly high. After it is dry, sand it lightly again and it should now have filled the hole completely. It will remain the same light red as the  "colouring" of the surrounding wood gain. Carry on to fill all the holes in a similar manor.

Filling shallow dips or contours is done the same way, just use a wider spatula and apply thin coats sanding between each layer. Each layer is checked until the area over the defect is the same color as the area around it and is feathered (smoothed) to the correct contour.

Long gaps such as during the repair done to correct a mis-cut fuselage side earlier are filled and sanded the same way.

Keep filling and lightly sanding the whole model until you are satisfied that is smooth and fair. Go to at least 220-400 grit as a final sanding. The model will be primed and additional filling may be required later.

Also you may notice the sand paper clogs with filler during sanding. To clean the sand paper use a gum eraser on the sand paper and it will remove the clogged filler.

[Gearup]

more filling picture