46" Spirit of St Louis

46" Spirit of St Louis 3.1

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Tench745

Master member
Tench745 submitted a new resource:

46" Spirit of St Louis - An updated version of my "Small Spirit" now with a rounded cowling!

A master series style, 46" wingspan Spirit of St Louis. Not a Swappable.
Uses a 2826 1400kv motor and 2000mah 2S.

Radial engine and other decals are included as a separate PDF.
Wing struts are not yet available. The landing gear fairings are still in beta.

Feel free to experiment and ask questions.

Read more about this resource...
 

Tench745

Master member
I wasn't planning on building this one out fully, but once I started mocking up the cowling to make sure it would work I had to keep going. Here are a couple process photos stepping through the build process.
The cowling starts by gluing up the nose box. The final version of the nose box varies slightly from the one in these photos, but the process is the same. The three cowling formers slide over this box.
IMG_1936.JPG
Former 1 glues on with the front flush to the end of the nose box. The 1/8" plywood firewall glues to the front of this assembly.
IMG_1933.JPG IMG_1932.JPG
Former 2 isn't really necessary, but it helps cut down on wrinkles when forming the cowling and adds a bit of nose weight. It glues on flush to the step where the larger portion of the nose box starts.
IMG_1934.JPG
Former 3 is made by gluing the two identical pieces together then gluing it on with the aft side of the former flush with the back of the nose box.

Once this assembly is all glued up the cowling skin can go on. Pre-form the curves on the edge of your table like any master series build, putting more curve in the aft corners of the cowling. The cowling piece lines up with the seam between the front and rear Former3 pieces. Start gluing at the top of Former 3 and Former 1, then work your way around each side in turn, finishing with the seam on the center-bottom. If you've seen a master series go together, you probably get the idea.
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The forward cowling piece gets rolled over the table edge and glued into a ring. There are three foam rings that get laminated together and then fit around the front cowling piece to help hold it round.
These rings are a mock up the Wright J-5 radial engine, the image is included in the markings Pdf. It is easier to glue this image onto the engine ring and trim it to fit before installing the ring onto the cowling. A little black marker to draw the rocker covers onto the edges of the engine ring finishes it off.
After your motor is mounted and ESC leads run you can glue the forward cowling and engine assembly onto the front of Former 1, beveling edges as necessary for a good fit.
IMG_1940.JPG IMG_1941.JPG IMG_1943.JPG
Once the cowling assembly is finished it glues onto the rest of the fuselage. The fuselage sides overlap the aft piece of Former 3 and Former three butts into the fuselage doublers.
IMG_1949.JPG
Here's a shot if the H-stab, elevator assembly to clarify all those score lines on the plans. There are two pockets cut into the underside of the foam which get a sectoion of BBQ skewer glued in to stiffen the H-stab and the elevator joiner. The long skewer passes through the notch for the V-stab, the V-stab has a notch for this so don't worry about it. With the elevator reinforcement, be sure not to run long and block the slot for the control horn.
IMG_1942.JPG

More pictures to come as I build out the wing. Feel free to ask for clarification on anything and I will do my best to show it.
 

danskis

Master member
For someone who lacks motivation you sure seem motivated.... Nice work!!!
Do you use hot glue or something else?
 
I wasn't planning on building this one out fully, but once I started mocking up the cowling to make sure it would work I had to keep going. Here are a couple process photos stepping through the build process.
The cowling starts by gluing up the nose box. The final version of the nose box varies slightly from the one in these photos, but the process is the same. The three cowling formers slide over this box.
View attachment 215449
Former 1 glues on with the front flush to the end of the nose box. The 1/8" plywood firewall glues to the front of this assembly.
View attachment 215446 View attachment 215445
Former 2 isn't really necessary, but it helps cut down on wrinkles when forming the cowling and adds a bit of nose weight. It glues on flush to the step where the larger portion of the nose box starts.
View attachment 215447
Former 3 is made by gluing the two identical pieces together then gluing it on with the aft side of the former flush with the back of the nose box.

Once this assembly is all glued up the cowling skin can go on. Pre-form the curves on the edge of your table like any master series build, putting more curve in the aft corners of the cowling. The cowling piece lines up with the seam between the front and rear Former3 pieces. Start gluing at the top of Former 3 and Former 1, then work your way around each side in turn, finishing with the seam on the center-bottom. If you've seen a master series go together, you probably get the idea.
View attachment 215450 View attachment 215451 View attachment 215452
The forward cowling piece gets rolled over the table edge and glued into a ring. There are three foam rings that get laminated together and then fit around the front cowling piece to help hold it round.
These rings are a mock up the Wright J-5 radial engine, the image is included in the markings Pdf. It is easier to glue this image onto the engine ring and trim it to fit before installing the ring onto the cowling. A little black marker to draw the rocker covers onto the edges of the engine ring finishes it off.
After your motor is mounted and ESC leads run you can glue the forward cowling and engine assembly onto the front of Former 1, beveling edges as necessary for a good fit.
View attachment 215453 View attachment 215454 View attachment 215456
Once the cowling assembly is finished it glues onto the rest of the fuselage. The fuselage sides overlap the aft piece of Former 3 and Former three butts into the fuselage doublers.
View attachment 215458
Here's a shot if the H-stab, elevator assembly to clarify all those score lines on the plans. There are two pockets cut into the underside of the foam which get a sectoion of BBQ skewer glued in to stiffen the H-stab and the elevator joiner. The long skewer passes through the notch for the V-stab, the V-stab has a notch for this so don't worry about it. With the elevator reinforcement, be sure not to run long and block the slot for the control horn.
View attachment 215455

More pictures to come as I build out the wing. Feel free to ask for clarification on anything and I will do my best to show it.
That looks so good.
 

Tench745

Master member
Tench745 updated 46" Spirit of St Louis with a new update entry:

V 3.1

Just posting an updated set of plans correcting a few errors in the wing drawings.
- Cutouts for aileron servos were backwards.
-Moved the wing base forward to correct wing location on fuselage.
-Widened the aileron cutout in the lower surface for better clearance.
-Added notches in the trailing edge for aileron control horn clearance.

Read the rest of this update entry...
 

Tench745

Master member
On to the wing.
First picture shows what it should look like after being cut and the foam removed.
IMG_1950.JPG
Picture two showing the bevel cuts and paper removed from the forward portion of the top wing skin. You'll want to roll this section over the edge of the table to establish a curve. If you don't the airfoil will kink slightly when you fold things over.
IMG_1951.JPG
Spars get glued on. The wider spar is scored down the middle, as per the plans, then glued and folded over on itself. This is the main structure of the wing. I haven't found it necessary on the prototype, but if you want some extra strength you could add a dowel, arrow shaft, or piece of wood along this spar between both wing halves. The thinner spar just helps establish the rounded curve at the leading edge.
IMG_1952.JPG
The cutout in the lower skin for the aileron gets folded over and glued. (c-fold) Before you fold the wing over, crush the trailing edge of this spacer slightly or you will have a slight gap on either side of the aileron bay.
IMG_1953.JPG
Next we start the airfoil. The paperless skin makes for a really smooth curve, but it is harder to get consistent curves from one side to the other. It might be easier to get a consistent airfoil if you glue both wing halves together before forming the airfoil, but I have not tried this method yet. Remember to pre-curve the top skin over a table edge or else it may kink as it bends over the spars.

Spread hot glue along the leading edge bevels and fold the top skin back until it touches the first spar. The hot glue will help melt the foam and form the curved leading edge. Once the leading edge has cooled, let the top skin lift again, spread glue on the first and second spar, then press the skin down until the glue has cooled. Try to keep even, downward pressure along the leading edge when you do this to keep the lower skin from lifting off the table and changing the airfoil.
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Now you can squirt some hot glue in the trailing edge and press it flat until everything cools.
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If you haven't already, now is the time to glue the wing halves together.
On my build I installed the servos first, but the arms get in the way, so I would recommend doing it last.
To join the wing halves, put a strip of packing tape across the seam on the lower skin. Hinge it open on this tape, coat the wing root generously with hot glue and then fold it back together, doing your best to align both halves. If you've built an FT wing you'll know how this works. There is no dihedral, so you don't need to prop a wingtip or anything. The last thing is to glue in the wing base. This is the cutout from the top of the fuselage and it helps keep the wing aligned when rubber-banded on. I make sure my glue gun is really hot, spread glue generously across the wing base, then press it roughly in place on the wing. Then, while the glue is still warm, I set the whole assembly lightly on the fuselage and nudge the wing until it is square to the plane.
IMG_1960.JPG IMG_1961.JPG
Here is the servo setup I have. Two 9g servos, FT control horns, two 6" servo extensions, and a Y-harness. For one side I plug the servo wire, extension, and y-lead together then tape the connections. Feed it from the servo hole, along the spar and out the center hole of the wing.
For the other side I run the servo wire and extension. Since we're installing these after the wing is folded you need a long enough extension wire to pull the connector out the center hole in the wing and plug it into the Y-harness.
IMG_1958.JPG
From here it's just a matter of gluing the servos in their pockets, making pushrods, and installing control horns. All this is pretty standard FT procedure.
IMG_1959.JPG
And we're done! The wing base nestles in the cutout on top of the fuselage and rubber bands hold it all on.
IMG_1962.JPG IMG_1963.JPG

If you wanted to add a little dihedral for a more docile flying experience you could always trim the upper skin slightly and prop up a wingtip when you glue the wing halves together. Personally, I don't think this is necessary and it takes away a little of the flying personality of the Spirit of St Louis. It's not a hard plane to fly, but you do have to fly it all the time, no letting your mind or thumbs wander, else the plane will go with them. The choice is yours.
 

Tench745

Master member
Just a quick photo comparison to illustrate the importance of pre-curving the wing top skin. The port wing was rolled over the edge of my table before gluing. It has a nice, smooth, consistent curve. Compare that to the starboard wing, which I forgot to pre-form and came out with a slight kink at each of the spars and the leading edge lifted ever-so-slightly from the extra force it took to shape the wing skin during gluing. Clearly either method will generate a wing capable of flight, but I know which one I prefer.
IMG_1965.JPG IMG_1966.JPG
 

danskis

Master member
Good reminder - also on some wings you have to remember that the paper has a grain and the grain needs to go the length of the wing and not across it. Otherwise it will cause the wing skin to kink.
 

Tench745

Master member
I forgot to post this here. Maiden flight video! I apologize for the camera work, it's hard to get a phone strapped to your head pointed where you want it.
It was cold enough that I couldn't feel my fingertips after 5 minutes, the motor was whining a little, and the wind was picking up, so I had to cut the flight short. I was hoping to get some more video by now, but it's been snowing and gusting for weeks here.
 

Tench745

Master member
Apparently I also forgot to show the landing gear struts. We start with the strut blank, this is the left side blank, but all the other photos are of the right side.
IMG_2012.JPG
The ends get tapered, the center gets a double-bevel. Foam is removed from the tab. On the first one I ran a skewer down the last score line, but it's easier if you save this for later. The strut then gets formed into an airfoil shape. I used foam cure for this step, but gorilla glue would probably work just as well. Don't use hot glue; when I tried it, it melted everything into a shapeless mess. Once the glue is dry we can run a skewer up the middle of the strut along that last score line. Don't glue the skewer in, we're going to let it float inside the strut.

IMG_2013.JPG
The paper tab gets glued onto the upper portion of the gear V like in the photos.
IMG_2014.JPG IMG_2017.JPG IMG_2018.JPG

The gear V then gets glued onto the landing gear wire. The wide portion of the V saddles the lower corner of the fuselage and glues in place. Finally, a little dab of hot glue secures the skewer to the gear V.
IMG_2020.JPG IMG_2019.JPG

The forward wing strut will attach to the point of the upper V... as soon as I figure out how I want make that happen.
 

Tench745

Master member
I had to make some tweaks to the design to get it flying the way I wanted. 47g of nose weight were added below the motor to get the cg on the marks. I would have added a spinner instead, but I don't currently have one that fits my motor. I also reduced the height of the forward spar by 1/8" to improve the shape of the airfoil.
Because the change to the forward spar is minor, I don't intend to update the plans at this time.