RAE Larynx - 1927 Cruise Missile

[kittyfritters]

The Black Sheep Exhibition Squadron is having a contest in February, "The Drone Shootout". It is for rubber powered, scale models, with a 16" span of a fixed wing drone or missile, nothing that ever had a cockpit. I decided to model the RAE Larynx, a British cruise missile from about 1927. Once I found that the Lynx engine that powered it was 42" in diameter it was simple to scale it from photographs. (Old fashioned mechanical drafting.) I drew a working plan, laser cut the parts sheets and started on it today. The picture shows how far I got. I will post as I go along.

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Larynx Build 1.jpg

Larynx Build 2.jpg

KF

[kittyfritters]

Progress on the fuselage has started.

Larynx Build 3.jpg

KF

[jpsaxnc]

That's coming along great. The engine on the original looks outrageous.

[kittyfritters]

That's coming along great. The engine on the original looks outrageous.

Yes, That is not exactly an NACA cowl!

The pictures make sense if you follow along

The original aircraft is mid wing and torpedo shaped with the the thrust line right down the middle of the fuselage. Since the model is rubber powered there is no room for a one piece wing. Having experience with 1930s model design I know that it's not practical to simply glue the wings on the sides. I drew the formers in the middle of the fuselage with enough clearance for the motor but with enough "meat" to hold glued in tubular stub spars for the wings to slide onto giving strength at the root and holding the proper incidence and dihedral.

Larynx Build 4.jpg

Now, to put this together. I glued the stub spars in place to the formers before I glued the formers in place. With all the formers on this side of the model I made sure they were perpendicular to the keels by using right angle tools. (See previous post.). Since there is no space for a side keel, which would have to go right through the wing, the stringers above and below the wing position act a side keels. To ensure that the spacing between the two wing mount formers remains correct I slipped the wing over the stub spars before attaching the stringers.

Larynx Build 5.jpg

The stringers above and below the middle stringers were left off to allow space for the former halves on the other side of the fuselage to be glued in aligned to the ones on the first side using the craft stick / clothes pin method.

Larynx Build 6.jpg

To be continued...

KF

[kittyfritters]

This is the obligatory "Bones Shot". The cowl laminations haven't been turned and sanded yet and the cylinder blisters are just pinned on. I may do a redesign on the nose since I weighed the laminations and even after turning and sanding that section will weigh more than the rest of the airframe (built with 6 pound wood). I has been suggested that I vacuform the cylinder blisters and that I leave the laminated nose since I will need nose weight. However, I still have to hang a prop on the front of this thing so I won't need that much nose weight.

Larynx Build 8.jpg

KF

[jpsaxnc]

I would finish out the cowl and blisters as they are, so you could use them as a mold if needed.

[kittyfritters]

It's not obvious from the photo but I made a rookie mistake on a couple of the formers and some of the stringers are a bit wonky. However, I drew the plans on a computer and I have a laser cutter so it's not a problem to redraw a few formers, cut a new parts set and build a new fuselage. While I was at it I put a proper keel into it to make the build even quicker.

More later...

KF

[kittyfritters]

I had to make a little fixture to keep the cowl cone rings aligned while I was stacking them. The first one that I did by eye looked OK but was out of balance and bent the mandrel that I was using to turn it on my Dremel drill press. The mandrel was a cheap knockoff and now I'm using a genuine one of proper tool steel.

Larynx Build 9.jpg

I also printed skins for it. The drawing you see on the wing skins is under the tissue on the old plan segments that I used for carrier sheets. The one piece skins for each side of the fuselage will be applied 'wet'.

More to come...

[kittyfritters]

So, I had the new ring stack for the cowl cone chucked up in my Dremel drill press and using a sanding block was turning it up very nicely. Then, the screw in the mandrel sheared off and the cowl shot off across the garage. It ricochet off of several things and, although I searched for an hour, I haven't found it yet. I'm going to go with plan B, the built up cowl.

However, progress is still being made. The wings and tail surfaces are covered and I predict that it will be flyable by the weekend...weather permitting.

Larynx Build 10.jpg

KF

[jpsaxnc]

When I lose something in my shop like that, I listen for the last place it made a sound. The thing that gets me is when I drop a non bouncy small part straight down, I hear it hit the floor right where I'm standing and it's nowhere to be seen.

[kittyfritters]

When I lose something in my shop like that, I listen for the last place it made a sound. The thing that gets me is when I drop a non bouncy small part straight down, I hear it hit the floor right where I'm standing and it's nowhere to be seen.

That was my first response, to go to the last place I heard it make a sound. Not there!

KF

[kittyfritters]

With the fuselage half covered you have a better idea of the colors. I could find no reference to what colors they actually painted it so I made a guess considering that it was photographed on orthochromatic film.

Larynx Build 11.jpg

The frame for the built up cowl cone is made from interlocking parts over a small fixture, that I cut from the same sheet as the parts, to keep it straight. I cut two of them, one I will infill with sheet and the other I will tissue cover. The frame has a rib for each cowl bump position that interlocks into the front and rear formers. I assembled it with Scotch Tacky Glue so I would have some working time. When dry, the cowl frame is simply lifted off the fixture.

Larynx Build 12.jpg

Larynx Build 14.jpg

KF

[kittyfritters]

At this point, I'm predicting 19 grams, all up, less rubber, with a 5" Peck prop. I'm not happy with it, could be a gram lighter and I did a sloppy tissue job but, with two NoCals to build (contest 3 days after this one) and a club newsletter to get out I don't think that I will have time to build another one even with another set of parts cut out. At least it should fly.

Larynx Build 15 S.jpg

KF

[jpsaxnc]

I can't wait to see it finished. It will be a show stopper.

[IMFlyer]

What a neat project, KF! That cowl is reminiscent of the individually faired cylinders on the Alexander Bullet (designed by Al Mooney)

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