Tutorial Advanced - Orta Saint - Hubert G - 1

[Gearup]

Applying exterior fuselage stiffeners

Stiffeners run longitudinally along both side of the fuselage. The original Orta looks to have been built from wooden frames skinned with plywood.

To represent the stiffener, I constructed one from heavy white card stock (110lb). The strips are 1/16" wide and cut 1" longer than the length of the fuselage. I used a paper cutter, but a knife and straight edge will work. Cut a few extra for the inevitable losses to the floor or other minor disasters.

The strips run from the cowl line aft to the end of the tail and will be trimmed to size once the glue dries,

I used the still visible alignment holes (now filled) to use as a guide to install the strips. Wet the strip using carpenter glue by applying a blob of glue to your finger then pulling the strip through the glue. Make sure enough glue is applied to the side of the strip that will be bonded to the model.

Lay the strip on the models side and apply a but of tension to the strip to straighten it out. Do not pull too hard though, the paper may pull apart otherwise (good thing there are extras right?) When you are satisfied of the location, rub the strip down into the side to ensure a good bond.

After a few minutes look where the front of the strip starts at the cowl line. Use a single edge razor blade to press lightly at the cowl line across the strip, just hard enough to hold the strip without damaging the wood fuselage. Lift the excess part of the still damp strip up and it should tear cleanly at the razor.

Of course this works better if the glue is not set completely. If it has set, you will have to carefully cut the strip across at the cowl line and remove the excess piece with a razor.

I left the tail ends long until the glue fully dried. This allowed me to simply cut the fully bonded strip flush with the fuselage end.

Apply the opposite strip as the first one.

Once the glue has dried, lightly sand the strip and make sure there is no glue squeezed out  along the length.

Note that this also a technique used to simulate wing rib tapes on wings, although I will use a different method later.

[Gearup]

Marking and drilling engine cylinder locations on the nose

The Orta has had several engine configurations: 5 cylinder radial, 7 cylinder radial and 4 cylinder inline. This particular one is a 5 cylinder engine.  The discussion on making the cylinders for this model will come later.

Side note: why do radial engines always have an odd number of cylinders, 3, 5, 7, 9? (Single row engines)

Template

Make a template to lay out the five cylinder locations.

Since the engine is five cylinders, a pentagon can be used to equally space the cylinders.
Either using a drawing program, cad, geometry layout with compass or tracing around a pentagon shaped toy draw a pentagon to fit a two inch circle (approximate). Find the geometric  centre and mark it. Use heavy card stock for the template.

Measure the diameter of the location aft of the nose to set the centreline of the cylinders. An easy way to do this is use a circle template (art store) and fit the nose into various circles until the template fits at the circumference where the cylinders will be located.  Due to carving variances, the desired size of the circle for the cylinders may vary.

Locate this circle centred in the pentagon and draw the circle to the template. Make sure the lines to the center are dark enough to see and cut out the inner circle. Cut the template outer size to about two inches in diameter.

You now have a template that can be used to mark out the locations on the model.

Marking cylinder locations

With the template positioned on the nose, trace the circumference around the nose.
Mark the location of the top cylinder on the centreline of the fuselage on the circumference line with a sharp awl. This is #1.

Making sure the #1 is always aligned with the template, mark the remaining four cylinders on the circumference line.

Single row radial engines are built with the top cylinder opposite from the oil sump. So the #1 is at the top and the remaining cylinders are numbered clockwise as viewed from the back.

Drilling the holes

Use a 1/16" twist drill to make the pilot holes. Start with the #1 cylinder as it is easiest to hold the model squarely for this position.  The model is wrapped with paper towel and mounted in a small vise. The smaller pilot will  start easier than the larger bit as it will not catch on the spherical nose very easily. Drill in vertically about 1/8" deep.  Remove the small bit and redrill the hole with the 1/8" bit.

Now rotate the model to get each cylinder location aligned vertical as in the #1 hole and repeat with the smaller bit before sizing to the 1/8" hole.

To hold the fuselage in the vice, wrap it with a small piece of paper towel, not cloth. Cloth may catch on the spinning drill bit and cause a hazard whereas the paper will tear out. NEVER USE CLOTH NEAR ROTATING TOOLS.

Side note answer: Radial engines always have an odd number to allow for the four-cycle firing order to work. All the odd numbers fire in sequence first then the even numbers fire in sequence. This pattern repeats and gives a radial that nice stuttering sound.  For a seven cylinder engine. 1,3,5,7,2,4,6,1,3,5,7,2,4,6

[lastvautour]

Never thought of using heavy paper for stiffeners. Great Idea Fraser.

Lou

[Gearup]

Thanks Lou. It gives a nice sharp definition and the thickness is about the right scale.

Fraser

[lastvautour]

I usually use masking tape but have to double it up. Heavy bond paper can be beveled if you are careful. Again, thanks for the tip.

Lou

[Gearup]

Creating flight control surface lines with a scribe
From a previous post on building the Mosquito Fish hook scribe description
For scribing the lines I watched a YouTube video "Creating scribed detail". The author uses dental tools but I tried another tool. I used a 4/0 fishhook modified and fitted into a x-acto style blade holder. I pinched the barb down with pliers, straightened it slightly then cut it off from the shank. The hook tip is actually triangular in cross section. If you work the tip against a fine sharpening stone you will end up with a triangular facet.  I used 0.003" brass cut to strips as a straight edge that was attached to the model with painters double-sided tape. A light touch works best.
Locate the lines that will define the ailerons, rudder and elevators. Keep in mind that flight control surface lines appear on the opposite side (top/bottom left/right). Starting on the wing, the reference holes were placed at the intersection of the aileron intersection of its leading edge and end rib.

Wing aileron upper and lower surfaces
Use a straight edge to lightly pencil in the lines on the top surface. The leading edge of the aileron on this airplane runs parallel to the wing trailing edge. Mark both the outboard and inboard ends of the aileron. This is a bit trickier because the aileron ends are parallel to the airflow, not square to the trailing edge of the wing.
The only wing surface that is square to the airflow is the leading edge of the center section of the wing. All the future references for the wing will be from the center section leading edge.

An easy way to transfer the ends of the aileron is to use the plan of the wing and cut out the aileron. Now you can use the reference hole at the outboard end to locate the aileron template you just cut out. Mark the aileron ends in pencil. Repeat on the opposite aileron.
Now work on the wing lower surface and mark the ends and leading edge of the ailerons as before. Looking edge on from the rear of the wing, the upper and lower pencil Lins of the aileron ends should be in line. If not, correct it before going further.
Now with the pencil lines as a guide, line up the straight edge on an aileron end line on the top outboard end. Hold the scribe like a pencil and drag it lightly form the leading edge marked out for the aileron back towards the trailing edge of the wing. You are scribing cross grain which is a bit more difficult than following the grain. Use a light touch to go over the line a few times to avoid tearing the grain out. When you have a nice distinct scribed line repeat this on all of the remaining aileron ends, top and bottom.
Now reposition for the aileron hinge line with the straight edge. The straight edge should be parallel to the trailing edge and contacting the forward end of the two lines defining the aileron ends. Scribe this line making sure not to run past the aileron ends to give a nice crisp corner. If you go a bit far, no worry...that is what filler is for.
Repeat scribing the remaining aileron lines.

Rudder and elevator hinge lines
Mark out with a pencil, the scribe lines of the rudder. Note that the rudder has a small portion that runs forward to the leading edge from the hinge line. This is the rudder horn aerodynamic balance panel. Make sure the scribe lines meet there and do not go past to the top of the rudder. Scribe the lines in on both sides.
The elevator does not have balance horns so the hinge line goes tip to tip square to the center line. The central notch that defines the elevator halves is the measure of  the width of the elevator.
I realize this is a long description of what is really a simple process but I unfortunately only provided one photo.

[Gearup]

Marking pin locations for aligning and mounting the tail surfaces

I like to use .020 inch brass wire pins to mount my wings and stabilizers. This provides a strong and accurate location of the vertical fin and stabilizer pin holes.

Here is a brief description on fabricating the locating pins as used on previous models They are 0.020" brass by 1/2" long. There is a small blob of solder at one end that has been turned using a Dremel tool against sand paper to create a small point. The solder cone acts as a shoulder to prevent the pin disappearing into the hole and the point makes a mark for the corresponding hole.
Vertical fin pin hole alignment method
To locate the pin holes I marked them out on the centreline of the vertical fin where it sits on the stabilizer. After marking the hole centers with a sharp awl I used a 0.025 (#72) drill bit mounted in a Dremel tool to drill two holes about 1/4 " deep into the fin. The pins were a bit too long so I shortened them for this particular job to about 1/4" overall length.
I inserted the pins into the holes and placed the fin in position on the centreline of the stabilizer with the pin tips just touching. When it was in the correct location a little downward pressure on the fin left two small centre points for the matching hole on the stabilizer. Now the .025' (#72) holes for the pins are drilled through the stabilizer.
Now put the transfer points through the stabilizer, with the pints on the bottom surface and align it so the centreline of the stabilizer is on the centreline of the fuselage. After ensuring the part is correctly aligned and not skewed of centre, press it down to leave the centre marks on the fuselage. Drill the .025 inch (#72) holes about 3/8 inch deep into the fuselage.

Cut two 1/2" pins from the .020 brass rod and insert them into the vertical fin. Place the fin on the stabilizer and place the whole assembly onto the fuselage. It should be nice and square. If not, you can adjust the holes a bit with the drill to give a bit of wiggle room for alignment.
Take the pieces apart after the dry fit is good. Use a pencil to mark the top of the vertical fin. A small "X" on the centreline will suffice. Keep the pins where you can find them for later assembly

[Gearup]

Sealing and Priming the model

Since we have the major components cut for the model, it can now be sealed and primed.

First I brush a couple of coats of nitrocellulose dope to the bare wood to act as a sealer /filler, sanding to 220 - 320 grit between coats. A great source for this type of dope is...clear lacquer nail polish from the dollar store! It is the same stuff as nitrocellulose dope and it even comes with a brush! Plus the small quantities are perfect for small projects like this.

Prior to applying a finish to the surfaces to be glued, cover them with small pieces of masking tape. The masked areas are visible on the pictures of the fin and stab. Don't worry if there area is a bit big, as a second coat of primer after assembly of the tail will fix that.

Since the parts already have an assortment of holes, it is easy to insert toothpicks into them to hold the parts for painting.

Apply the first coat along the grain and the second coat across the grain. Wait about 20 minutes between coats.

After drying and sanding smooth, now apply the primer. I use a spray automotive primer /filler that is sandable. Ant brand will do, just make sure it is a sandable, filler primer. I t comes in various colours. I generally use grey, but I also use the off white as well depending on the top coat colour. The primer should be well shaken and when applied will go on as a wet looking coat. Don't apply too heavy to prevent runs, but a a short spray along the full length of the object about 8" away works well. The product I use looks somewhat rough when wet but dries quickly to a nice even flat finish.

Look for any imperfections in the models surface and apply thin body filler as before over the areas and sand them back.

You may notice that the bare wing has had the rib stitching details added before priming and the fin and stab have had the stitching added later. Either order is fine and will work in the next step in adding the rib stitching with glue.

[Gearup]

Wing rib simulated stitching-tape using glue
Ref article 1/48 Fiesler Storch August  23 2019 replay
Photo from web
The following information is from a post from my 1/48 Fiesler StorchcReply #1 on: August 23, 2019, build. It describes the process for building and using the wing stitching jig with a ruling pen and thinned glue.

I made a small fixture that essentially allows me to follow a straight and perpendicular line across the wing surfaces. General construction of the fixture is two 1"x 0.5"x 10" rails screwed to a board and spaced apart the width (chord) of the wing plus about .5" extra width. I double side taped a copy of the wing plan to reference the rib spacing on top of one of the rails. I placed the wing in reference to the drawing on some spacer blocks to get the top surface to just below the tops off the rails. Double sided tape is used to secure the spacers and wing together on the base. Small pieces only required. Tape of areas that do not have rib stitching ie: smooth panels.

I mixed a small quantity of water proof wood glue  (Elmers glue, PVA that was on hand). The waterproof glue seams to be a bit better at remaining as a raised line. About 2ml of glue thinned with 0.5 ml of water (few drops); enough that it drips off a toothpick. Now using a small square that spans over the wing and sits on top of the rails, line it up with a small offset from the drawing to allow for the pen width. Dip a ruling pen into the glue and touch off the excess. Now draw the pen along the edge of the square to mark the rib. A ruling pen can be adjusted to get the line width you want. I set it about 1/32" wide. Continue along making rib lines, refilling the tip as needed. Since the square is sitting above the wing surface, there is no risk of smearing the wet glue and you can go over a rib again if needed. When done, peel off the tape and continue to finish the model.....

smearing the wet glue and you can go over a rib again if needed. When done, peel off the tape and continue to finish the model.....
Building the fixture took about an hour, but it can be used to make future models.

Tools needed:
Ruling pen
Small square
Simple fixture as described above

Materials:
Double sided tape
PVA type glue thinned with water
Regular masking tape

For this model, I used a photograph to count the ribs and divided the number rib spaces into the model measurement to get the spacing for the model. This is also how the spacing for the stab and fin was calculated. For the wing  from the plan, there are 10 spaces between center of the wing to just outboard of the aileron end. The measurement is 3.785" / 10 = 3/8" spaces.
For the stab the spacing is 1/4 " and the fin is 3/16".

Tape the area along the leading edge about 1/4" wide to provide a clean line to define the forward end of the rib stitching. Raise or lower the wing to provide a clearance of about 1/32" from the square to be used and the top of the wing surface ( I used a popsicle stick under the square here). Align the center of the wing to the first line of the markings with the center leading edge against the jig to ensure the correct alignment of the wing.

Mark the ribs as described above. Repeat for opposite wing half and lower surfaces. Position the fin and stabilizer in a similar manor and apply the glued lines.

[Gearup]

Assembling the tail

Since the detailing of the fin and stab are complete, I decided to assemble the fin and stab to the fuselage.

Since we have the alignment predetermined by the pins previously fitted, it is a simple matter to assemble the parts.

Insert the two pins (kept from earlier) into the fin and apply wood glue to the base of the fin. Insert the pins through the stab, ensuring the stab top surface is up and check the fin for vertical square. Let it dry for about 1/2 hour.

Now apply glue to the notched surface on the fuselage where the fin sits and insert the exposed pins into the holes.  Check that the fin is level and square to the fuselage viewed from the back and is not skewed left or right sitting on the fuselage.Clean up any glue squeeze out before it dries fully the set aside to dry.

Once dry, apply a bit of body filler to any gaps, most likely at the centre leading edge to fuselage joint and file or sand smooth.

[Gearup]

The Landing Gear.
This will be a fun challenge coming up...Jigging and soldering up the brass landing gear assemblies..........

Soon....
Fraser

[Gearup]

Landing gear and strut fixture

I have taken quite a hiatus from writing this tutorial. I turns out that the seemingly simple model  airplanehad landing gear that was the most challenging part of the build. The landing gear is incorporated into the wing support structure and is comprised of five struts per side. There are multiple soldered connections as I like to use brass tubbing and wire for gear construction. The three dimensional aspect of the gear means that I needed to construct a jig to fit all the parts together before I tried assembling them to the model fuselage.

Since all of the components except the vertical gear struts are at a diagonal to any view of the aircraft, it is a challenge to determine the actual length of each strut.

Add to the challenge there where different configurations of the landing gear geometry depending on the development of the Orta. Some variations where found in the pictures of the actual aircraft that did not match the three view plan I had.

So staring off, I designed a holding fixture to represent the fuselage and wing attach points based on the side view of the fuselage. IMG0996

I went a bit overboard and drew up a 3d model in Sketchup based on dimensions from the plan and the as model fuselage as it was built.

Most important considerations were the: cross section of the fuselage, the location of the lower fuselage attach points, the height of the bottom of the fuselage ( when level) above the ground, the height of the axels above the ground, upper fuselage attach points and wing lower surface above the ground.

I drew up the points in Sketchup but in fact it was just as accurate to build of the fixture by direct measurement.
.
I made a side view block as shown in IMG 999 from material the thickness of the fuselage width and the height of the axel to the bottom of the wing.   It was hot glued to a base block, making sure it was positioned squarely. IMG 1001

I used dividers to mark the width od the gear from the fuselage side drawing and transferred it to the wooden block. IMG 1003

The centre of the vertical strut was marked square to the block approximately mid point IMG 1006

The fuselage bottom was marked reference to the axel and the attachment points marked on that line either side of the vertical reference. IMG1007

The upper wing strut attach points on the fuselage were measured up from the bas and the positions of the attach points marked on the line.IMG1008 and IMG1011

Problem. The aft end of the upper strut is actually farther aft on there aircraft than the drawing shows, so I had to adjust the mount point aft based on a photo. IMG1012.

I used a sharp awl to make a pinpoint at each attachment. This is repeated on both the left and right sides of the fixture.IMG1011

[Gearup]

pictures ref fixture

[Gearup]

Wing lower surface Fixture

After the gear points are marked on the base and fuselage points, a representation of the wing lower surface is attached to the top of the fixture. This will allow for accurate positioning of the wing and vertical strut. IMG1037

A thin plywood was used to represent the centre flat portion of the wing lower surface. It is attached to the top of the fixture so the lower surface is the plan measured distance from the axel to the wing bottom. A line is drawn on the lower surface to mark the fore/aft location of the wing mounting points the measurement of the points are taken from the drawing and marked on the surface left and right.

The wing fixture section is attached to the top of the fuselage fixture using small 1/8 dowels to allowing it to be removed as required after finishing the gear soldering. Make sure to mark the forward direction for reference.

Drill a 0.020"  hole at the two wing strut attach points on the fixture and the bottom of the fixture but the end of the vertical strut. The upper and lower holes should be in vertical alignment and will be key to fitting up the gear parts.

[Gearup]

Making aerodynamic flattened brass tubes
The struts of the wing and gear structure are aerodynamic shaped tubes. To make them I use brass tubing with a core of 0.020" brass wire. If the end of the strut is to be attached by adhesive to t wood, I leave the wire inside about 1/8" long to use as a pin.

After the tube is measured for length, a piece of wire about 1/4" longer than the tube is inserted into the tube. The gear uses 0.062" and 0.096" brass tubing as required for the particular part.

To flatten the tube, use a flat faced hammer and a steel plate as an anvil. Using even steady flat blows to the tube flatten it until it has firmly pinched onto the wire inside. Trim the wire as needed for the particular part location. IMG1034, IMG1035, IMG1039, IMG1040