Fuselage Construction

Riley Model B - Series 11 - Fuselage Construction

December 22, 2016

Fuselage construction (ready to paint) will require about 80 hours. Note: Some of the pictures are from earlier editions. The text has been updated and is accurate for Series 11 construction.

Order of Fuselage Construction

1. Apply paper template to flat building surface and set jig blocks in place.

2. Prepare all fuselage formers.

3. Glue all forward stringers to rear stringers (sticks) at scarf joints.

4. Depending of which engine is to be used, set F2 in position with (4) designated forward stringers.

5. Install pull-pull cable tubing.

6. Mount and glue all remaining stringers, including short pieces F15-F16.

7. Cut off “legs” from all lite ply formers (F6-F14). Leave all other legs in place.

8. Apply balsa planking, shape and sand.

9. Apply 4oz fiberglass cloth and epoxy resin to planking. Paint epoxy inside of engine bay.

10. Apply basswood, mahogany, or other veneer.

11. Cut and trim cockpit opening, rear scallops, bottom of engine bay, and holes for Camloc mounts.

12. Apply cap strips to rear stringers. Install balsa fill pieces at tail wheel mount. Assemble tail wheel forks.

13. Form pull-pull cable tubing exits.

14. Dress veneer seams (if needed). Sand entire fuselage to prepare for varnish and covering. Glue gas cap mount in place.

15. Varnish veneer and instrument panel.

16. Complete and sheet stub wings.

17. Cover the fuselage, stub wings, fin and stabilizer. And while you’re at it, you might as well cover the wings, each elevator and the rudder through one coat of nitrate dope (but not painted yet).

18. Install headrest.

19. Mount stabilizer and fin to fuselage.

20. Form wing fillet and tail fillets.

21. Prepare to paint.

22. Paint.

23. Install fuel and smoke tanks. General plumbing.

24. Install all radio control electrical. Install pull-pull cables.

25. Cockpit combing. Windshield. Gas cap.

26. Hinge ailerons, elevators and rudder.

27. Install flying wires

28. Motor install.

29. CG check.

2 In order for the fuselage to be straight and true, it must be built upon a flat surface. A plain door panel works well. If in doubt, check for twist with a level. If the reading is the same on both ends, obviously, you have a flat building board.

There are two ways to mount the paper template to the building surface. If you have an extra set of hands you can probably lay down the template in one piece. If not, draw a straight-line on-center on the building board. Cut the template into smaller sections. Apply each section in alignment with the datum/reference line. Apply 3M#77 adhesive to the paper not the building board.

Glue 3/4” x 3/4” x 1-1/2” jig blocks to paper template. Use Titebond glue; CA glue will work, but it will likely soak through the paper and stick to the building surface and be very difficult to remove. Make sure jig blocks are drilled according to the instructions on the template!

Mounting the Formers to the Jigs

There are various ways to mount the formers to the template jigs. Screws or clamps all work well. The important thing is to align each former laterally on-center as shown on the template. The holes in the formers are designed to allow some adjustment. The holes in the jig blocks are drilled so that a #6 sheet metal screw goes in easily. Any #6 screw and washer combination should be fine. Keep in mind that the jig blocks are glued to paper and the paper is attached only with adhesive spray to the building surface. Make the screws snug, but there is no need to over tighten. The jig blocks have plenty of strength to keep the formers in alignment while the stringers are added, but they can become detached from the paper template with rough treatment. Be gentle.

The larger formers, if not careful, can easily tip over before they are secure. The “legs” on each former are strong enough to do their job –they will be cut away later –but they can break if you are not careful.

4 When in doubt, dry fit all joints. We are working with wood. Wood can swell in humidity. The wood itself (stringers, for example) may not have been precisely sanded to the specified thickness. A basswood stringer only a few thousands oversize, can make for tight fitting joints. Any number of factors can affect fit. Use a small flat file to open up former notches, if needed. Check everything and don’t glue until you know it is right.

One more thing: Although the stub wing ribs SW3 are not glued in place until much later in the framing process, it is good practice to make sure they fit nicely to the spars of F3, F4 and F5 early on. Check the fit of the tenons at the ends of the spars of each former with the mortises (slots) in each SW3 rib and make any necessary adjustments. Do this before mounting the formers to the jigs.

Important: The labels on all fuselage formers face toward the front of the model. Unless otherwise noted, right and left are determined as if you were sitting in the cockpit facing the nose.

Prepare Fuselage Formers – F1

Press two 4-40 T-nuts into the 9/64" holes through the backside of F1. (The T-nut flange faces the tail.) These T-nuts, along with 4-40 socket head screws and washers, will be used later to mount the optional Power Box Smoke Pump.

5 Prepare Fuselage Formers – F2

Press four 10-32 T-nuts into the 1/4" holes through the backside of F2. (The T-nut flange faces the tail.) Make sure they are fully seated. To create the motor mount studs, insert four 10-32 x 1-1/4” screws from the rear. Add a drop of thin CA to the last 1/4” from the head. Immediately tighten the screw all the way. The CA glue will seize very quickly and permanently lock the screws in place.

6 Prepare Fuselage Formers – F3 and F4

Position and glue F3A (right and left sides at stub wing spar) to the front of F3. Glue F4A to the rear of F4.

Formers F3 and F4 are glued together to make one module out of the two formers, the wing tube socket center mount, and the landing wire mounts (hard points).

Dry fit first. When all parts fit together nicely, glue and mount F3-F4 to the jig blocks.

8 Prepare Fuselage Formers – F5

Position and glue (4) F5A to the front and rear of F5.

Prepare Fuselage Formers – F6 and F7

Dry fit first. Assemble the battery box that is located between F6 and F7. Insert box between the formers. Install the servo tray. When all parts fit properly and are square, use thin CA to glue all joints.

11 Glue receiver tray in place. Make CERTAIN that the narrow spaced threaded holes orient toward F7. Also glue the pilot tray mounts to F6-F7. Make sure that the mounts are fully seated. When finished, mount to template jigs.

Fuselage Formers F8-F14

Formers F8 through F14 do not require any preparation. Just make sure that the part labels face forward.

Prepare Fuselage Formers F15-F16

Insert a 6-32 T-Nut through the top side of the tail wheel mount.

Glue stabilizer spar pocket to the tail side of F15. Titebond recommended. Use #2 servo screws to insure correct alignment and provide clamping pressure while the glue sets. These may be removed later.

Insert and glue tail wheel mount into F15 and F16. Mount the assembly onto the template jigs.

15 Notice in the previous picture that F2 is not shown. The stub wing ribs SW3 are in position to make sure that they fit nicely to the spars, but they should NOT be glued at this time.

Mounting F2

The Series 11 has 1.5° right thrust and 1.5° down thrust angles built into the airframe. These angles are governed by the position of F2, which in turn is governed by four special cut basswood aligning stringers. However, some hand finishing may be required for the stringers to fit well into the notches of F2. How much is a factor of how close the stringers are to exactly 1/8” thick, whether the plywood used to make F2 is exactly 6mm thick, and how accurately the notches in F2 were sawn. Before you install F2, check the fit of all the notches in F2 to see if they will allow the stringers to angle slightly (1.5°) of square, you can do this by eye. If the fit is too tight at square, obviously the fit will be even tighter if angled 1.5°. The solution is simply to use a small flat file and open up the notches slightly. It won’t take much. Sometimes only the width of the notch of the stringer itself is all that needs to be shaped. All notches should be checked before mounting. When F2 is in place, with all the stringers and planking also installed, you will have a very secure F2 on which to bolt the engine motor mount.

The fuselage construction procedure for either the Moki 180 or the Valach 120 is identical, EXCEPT for the position of F2. The F2 former for the Moki and the Valach are not the same; they are not interchangeable. The four special basswood aligning stringers are not the same either. Depending on which engine you have chosen to use, make certain that you are using the correct F2 and the correct aligning stringers for that engine. These two engines have different requirements for correct mounting and are not interchangeable.

There are four special alignment stringers that govern the correct location of F2. (All other stringers, both basswood and balsa, are generic and interchangeable.) Of these four stringers, the two for the bottom or right side are identical and interchangeable. And the two stringers for the top and left side are identical and interchangeable.

All forward stringers, including the special alignment stringers, have a scarf joint near F5. All of these forward stringers should be glued to either 1/8” x 3/8” x 48” basswood sticks or 1/4" x 3/8” x 36” balsa sticks. It is easier to glue the stringers to the formers in “one piece” than it is to glue the scarf joint in place at F5.

The bottom basswood stringer goes first. This is also a special alignment stringer that should be labeled “bottom or right.” Always make certain that this and all other stringers are full seated in all the former notches. When installed correctly, the stringers will protrude about 1/32” forward of F1 and will be sanded flush in a later step.

Glue the bottom stringer in place. It will terminate at F15. Set F2 into approximate position. Install the top special alignment stringer is place. Do the same for the right left sides at the 9A and 3P positions.

16 When you have determined that F2 is aligned properly and that all four special alignment stringers are fully seated in their respective notches, glue all joints. It is highly recommended that you do not install the remaining stringers until you have installed the pull-pull tubing as shown after this series of pictures.

To make sure that F1 is square vertically, clamp a square to your work table and F1 while installing the stringers.

Install Cable Tubing

You will need three sets of Sullivan brand #503. Route cable tubes as shown on the fuselage template. Do not glue the tubes. They will be exactly positioned at the rear in a later step.

19 Install All Remaining Stringers

Work from the bottom and toward the top and mount and glue the rest of the basswood and balsa stringers. If you don’t do it this order, the lower stringers will be difficult to mount and glue.

The forward tips of all stringers will mount slightly proud of F1 and will be sanded flush in a later step.

Make sure that all stringers are fully seated in the notches –especially at F14 and F15. The stringer cap strips, to be added later, will close the gap.

You will need to cut and fit the two stringers –one basswood and one balsa –that fit into the stub wing spars (F3A, F4A & F5A. To fit, simply cut on the notch line with a razor saw. The balsa stringer that joins with the landing wire hard points will also need to be cut to fit.

The balsa stringers terminate at the last former which has a 1/4" notch.

The basswood stringers at 8A, 9A and 10A and 2P, 3P and 4P should terminate at F15 so stabilizer spar pocket is left open. No stringers should extend through the stabilizer spar pocket. Fit short stringers from the rear side of the spar pocket to F16.

21 Just for fun, here’s what the engine and motor mount setup will eventually look like. Obviously, if you choose the Moki radial it will look different, but the motor mount will bolt to F2 just like the Valach 120. The shock mounted Garolite tray is for the ignition module and allows the engine to be removed without disconnecting the ignition.

Prepare for Balsa Planking

Remove fuselage from building surface. Save template for reference, but otherwise, it is no longer needed for construction. Cut off “legs” from all lite ply formers (F6-F14). Leave all other legs in place. Go over all joints and add additional glue where needed.

With the legs on F1, F3, F4, F5, F14 and F15 still in place, the fuselage should set square on the building surface and will help keep the fuselage square while the upper sections of planking are glued in place. But since the sides and bottom also need planking, a method to rotate the fuselage to any position will be needed. That’s next.

22 Make Jigs to Support Fuselage

You will find it to be a very frustrating experience if you try to plank or finish the fuselage without the use of support jigs at F1 and F16. Make four standoffs that will attach at F2. These can be made from 1” x 4” wood dowels. Drill 5/16” holes 1” deep on each end, and then add 10-32 threaded inserts (McMaster-Carr 92105A670). From these stand offs almost any jig arrangement can be devised. These standoffs have worked very well for previous models. However, the Series 11 incorporates engine offset, which means that F2 is also offset. The upper right stud’s new location will prevent mounting the standoff. The solution is to use a belt sander and reduce the diameter on one end to about 5/8”. The other three standoffs will work fine as they are.

There are two 1/4-20 tapped holes in F16. Use either of these holes to attach a support for the tail.

24 Planking the Fuselage

Planking the fuselage is a job that requires patience, skill and experience. So please, don’t rush this process. In fact, it really can’t be rushed. There is no fast way to plank. Allow about 7 hours to plank. Planking is tedious, messy and possibly frustrating. So let’s get started!

The following bullet points are not meant to promote a precise sequence, but to provide some insights so you can develop a planking procedure that works well for you.

The planking pieces themselves can be individually fitted or you can cut them to size using the paper templates. The paper templates are technically accurate but may require some trimming for a good fit.

Planking is best cut on a band saw. Remember to mark the 1/4" overhang that will extend forward of F1. This is to insure that the planking doesn’t come up short and will easily trim flush to the face of F1.

Use Titebond. It has just the right amount of open time to allow positioning and clamping without rushing. It has a good grab and will set up in 30 minutes.

You can either apply the glue to the planking or the stringers. A combination of the two works best. Apply glue to the planking for the stringers, and apply glue to the formers with an acid brush. On the glue side of the planking, scribe a line right down the center to create a guide for the glue that will contact the basswood stringers. On each side, apply the glue that will contact the balsa stringers. Make sure that you apply plenty of glue to F1-F5 -especially F1.

Preparing and gluing the first plank may take an hour or more to do right. Be patient. You will be rewarded by not having to undo mistakes. This planking step is unlikely to result in perfect seams. Fortunately, perfection is not required. As long as the planking is secure to the stringers, gaps as wide as 1/16 won’t be a problem later. Once the planking is glued and sanded, the epoxy resin and 4 oz. fiber glass cloth will fill the gaps and lend all the strength needed for a strong fuselage. This whole process will come out better than you think.

NOTE: The open space between the stub wing spars must be filled in (section #5). If you don’t, the vacuum created by the open cockpit will suck up grass and debris up from the wheel pants. Make sure this area is sealed!

You will need at least 100 push pins to hold the planking in place while the glue dries. Push pins work surprisingly well for clamping. You will not have a good experience with cheap plastic pins. Make sure you are using heavy duty pins. I recommend “Moore Aluminum 5-100, 5/8” steel point with 1/2” aluminum head” –available from www.amazon.com.

You will also need some clamps to pull the planking down tightly against F1, and anywhere else that needs a little help. You will need at least 4 clamps at F1.

All planking pieces are mounted “on-center” –meaning that the center of each plank is glued to the basswood stringer and clamped (and pinned) at the edges to the balsa stringers.

The balsa stringers are not indestructible. Take care when pushing in the pins. Since the planking is made from 3/32” balsa, it should bend without water or steam. Note: C- grain balsa is great for ribs, but is a poor choice for planking because it has a tendency to split.

When you remove the push pins you will likely have some dents in the planking. These will probably disappear after the planking is sanded.

Mount and glue the top piece first, and then work down the sides. Needless to say, as long as the fuselage is mounted to the building board, you can only mount the top and two segments on each side. When this is accomplished, the template and jigs have served their purpose and the fuselage can be removed and the legs cut off. Use the F2 and F16 support jigs from now on. Turn the fuselage over and plank the bottom.

29 Shaping the Fuselage after Planking

After the fuselage is planked, fill the seams and dents with lite spackle. After it is dry, give the fuselage a preliminary sanding with a 50 grit large sanding block. Use this step mainly to smooth out the spackle. Spray a lite mist coat of fast drying primer onto the planking. Use 45- degree light sanding strokes. When the mist primer coat is almost all gone, you’re done. Don’t sand excessively. Just enough to make the fuselage smooth and nicely rounded. You may find that simply using your finger’s sense of touch is the best guide. Mount the cowl ring to F1. This will serve as a sanding thickness guide. Plan on about 3 hours to sand the planking.

32 Fiberglass the Fuselage

Plan this step carefully. Allow about 3 hours to glass the fuselage.

Cover all fuselage planking with 4 ounce fiberglass cloth (#1522-50 Aircraft Spruce). One layer will be plenty strong. Use West System 105 Resin and 206 Slow Hardener, or similar. This hardener is low viscosity and will allow plenty of time to compete this step. A small paint roller works very well to spread the epoxy resin. You will use 8-10 ounces of resin.

Paint Engine Bay with Epoxy

It is inevitable that gas, oil and dirt will find its way into the engine compartment. If it soaks into the wood, you will not only have a mess, but it is virtually impossible to remove –a very distressing situation. Allow about 40 minutes to “paint” all of the inside surfaces F1-F3 with epoxy. Epoxy does not flow like paint, so just brush it on liberally any way you can. Then, when you are certain that all wood surfaces are coated, use a clean cloth and wipe off all the excess epoxy. When the epoxy hardens it will look pretty good and will prevent any oil or gas from seeping into the wood. Make sure to protect the motor mount threads with tubing!

Applying the Mahogany or Basswood Veneer

You are now leaving the world of model airplane construction and entering the world of fine woodworking. Veneering is expensive, wasteful, messy, tedious, time-consuming, and often frustrating. But it looks fantastic!

If you plan to finish the planked part of the fuselage with dope or paint, then needless to say, the veneering process can be skipped. Sand the fiberglass cloth. Brush on one thick coat of nitrate dope. Apply Sig Sanding Sealer and sand. Repeat as necessary to create a smooth finish.

A mahogany or basswood veneer finish is beautiful and different. It takes patience and skill, and will add at least another 15 hours to your building time, not counting the time it takes to apply up to 10 coats of varnish. One source of mahogany veneer is www.woodcraft.com. http://www.woodcraft.com/product/131443/mahogany-veneer-12-sq-ft-pack.aspx

Thin basswood is available from www.nationalbalsa.com.

The paper templates are accurate, but keep in mind that the fuselage is a series of ever changing compound curves, so some minor fitting may be necessary. The last two planking pieces at the bottom will be fitted. The following procedures and methods are a general description of how to plank the fuselage with veneer.

Sig Stix-it is a heat activated adhesive that works better than anything else I’ve tried. You will need at least a pint, maybe more. A hobby covering iron works fine for covering but will NOT transfer enough heat to set and cure Stix-it when using it for veneering. To make sure you have enough heat, use an ordinary clothing iron set to “high” or “cotton.”

To position the veneer for fitting or gluing, use masking tape as an extra pair of hands. Scotch #2020, 3 Day High Adhesive has a very strong grip and works best.

Stix-it adhesive should be “painted” on both the fuselage from F1 to the end of the balsa planking AND the veneer. It is a little more wasteful, but considerably easier to “paint” the veneer as it comes from the package before cutting to size.

Sometimes it is a good idea to check the grain to see if you like what you have and perhaps to decide which pieces will look best in a certain position. A good way to do this is simply to wipe some paint thinner on the veneer. This will give you a good idea of what it will look like after it is varnished.

Cut the veneer stock into (22) 2” x 48” strips. (Basswood will come 2” wide.)

Spray 3M #77 to the paper template (Veneer #1) and attach to the veneer. Carefully and accurately cut the piece with sharp scissors. The dowel holes should be cut with a 3/16” paper punch. With the same punch, cut some “dowels” and press them back in with the grain rotated. This will create a nice subtle look of dowels holding the veneer in place. Make one piece at a time. After cutting the first piece, remove the paper template. There will still be enough adhesion to apply and cut the second identical piece. (You will make two pieces from each veneer template.) Use a pencil and draw a line 1/4" from the front edge (shown as a dashed line on the paper template). This line should align with the front face of F1. The overhang will be trimmed after the engine bay is painted with epoxy.

Start at the top. Lay a straight edge exactly on-center at 12:00 o’clock and draw reference line. Begin ironing the veneer with reference to this line.

With your iron on the “cotton” setting (high), iron down the veneer. Sometimes a small block of wood can be used to press the veneer down while it cools and bonds.

All the rest of the veneer strips, except the bottom two, generally follow the procedure described above. Some fitting of #10 will be needed to clear the stub wing spars.

36 As you plank around the fuselage, if you notice that the veneer strips are trending a little wide or a little narrow, just cut your next strips a little wider or narrower to compensate. These templates are very accurate. In actual practice, if the veneer seams stay within 1/16” of the stringers center, you will be fine.

The last two pieces at the bottom (# 12) should be cut about 1/4" wide on the side that will be “on-center.” This means that you will have two pieces that are NOT identical, but are mirror images of each other. The excess edges should overlap each other at 6 o’clock. Use tape to hold in place. Use a straight edge and cut both excess side simultaneously. This should create a perfect fit for the final seam.

See pictures on the following pages.

Trim Veneer at F1

Trim off veneer and sand flush with F1. The veneer is very delicate and any mistakes here will be very noticeable. Perform this step with plenty of patience, a fine tooth razor saw, and a sanding block. Mahogany veneer is somewhat fragile, so take your time.

43 Trim Fuselage

Trim away excess planking to (1) create the cockpit opening, (2) the bottom opening between F2 and F3, (3) the holes for the landing wire mounts (Camloc receptacles), (4) the scallops (semi-circles) that create the transition from the planking to the rear stringers that will be covered with fabric.

Use the paper templates on the plans for the cockpit opening and the scallops.

The bottom opening to the rear of F2 to F3 is bordered on the sides by the balsa stringers.

The landing wire mounting holes are located (on-center) 10” back from the face of F1 and on center with the stringers. Drill a 3/16” starter hole, then open up with a regular #11 blade.

Use 3M #77 to temporarily attach paper templates.

The pictures below are from an earlier build and show the cutouts being made before the veneer was applied. While it can be done either way, it is simpler to make the fuselage cutouts after the veneer has been applied.

46 Cutting away the scallops is not difficult but it is very time consuming. Make rough cuts first then finish with careful sanding. All of the scallops are measured on-center from the rear face of F16. Cut templates and locate to the appropriate position with 3M #77 spray adhesive, then mark the cut with a pencil or ball point pen.

There will be considerable excess planking to cut away, including the balsa stringers. All scallops are cut between the basswood stringers.

The top piece of balsa planking should terminate square at the rear side of F8 and between the basswood stringers at 11A - 1P. All other scallops are sized and located according to the chart below. The location of the 12 basswood stringers follows the face of a clock.

49 Add Cap Strips

Glue 3/32” x 1/8” basswood cap strips to the rear stringers from the scallops to F15 or F16. The purpose of the cap strips is to create a consistent stringer height (or transition) from the scallops to the rear of the fuselage. Neither the stringers nor the cap strips should pass through the stabilizer pocket. You will need to sand fair most joints at the scallops and the bottom stringer at F16.

50 Add Balsa Fill at Tail Wheel Mount

Glue parts in place, then shape and sand to conform to the taper and curves of the fuselage.

51 Control Cable Tube Exits

There are 3 pull-pull cable tube exit points on each side of the fuselage. The installation procedure is the same for top elevator, bottom elevator, and rudder. Installing, forming and finishing the cable tube exits is somewhat challenging. We’re dealing with compound curves and twisting stringers. For that reason, work slow and careful!

All six cable tube exits install by the same method. Make sure to dry fit before gluing. You may need to sand the beveled edges slightly for better fit. The correct position for each part, when sanded, should be flat to the edge of the cap strips, just like the covering will be flat between the stringers. A small balsa wedge in the slots may be useful to hold the pieces in place until the glue dries.

Push the Sullivan #503 tubing forward so they are out of the way.

The upper elevator/rudder exit mounts slightly forward at F13 and butts against F15. Glue in place.

Install and glue the lower elevator exit. It should be located on-center at F14

Pull the tubing through the corresponding slots and scuff the ends with sand paper.

Glue the top elevator tube terminating at F14.

Glue the rudder tube terminating even with the rear side of F15.

Glue the bottom elevator tube terminating midway between F14 and F15.

54 Fit scrap balsa into the open slots and sand flush.

Use lite spackle to fill voids and form a nice filet around the tubes. It will probably take two sessions to get the filets to form the way you want them. Use any curved blade with about a 1/4" radius. The rounded end of a 6” metal rule works well.

Alternately, the fileting step can be done after the fuselage is covered.

The servo ends of the tubes will be trimmed in a later step after the cockpit is opened up.