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  #1  
Old 06-02-2018, 03:09 PM
DavidQ DavidQ is offline
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Default Two Falcon K-13's

The next build in the K-series is the K-13 Falcon. This is a boost glider - actually the second boost glider Estes released, if we count the K-3 Astron Space Plane.


I've never been good with planes, even if they have rocket engines attached. One might think that planes or gliders would be easier if they are rockets, but I'm not sure that is true. So, I built two of these.


The first is according to plans, with thin, frail, easily breakable balsa.


The second is with plywood and harder woods. Heavier, of course, but hopefully more rugged.


I cut them with a laser cutter. The nose cones are rotocast from resin. I tried to keep the mass of the cast cones comparable to balsa, give or take. The instructions call for adding lead weights to the nose for balance, so I wasn't really too concerned with making the cones a bit heavy. I hadn't cut the motor mounts when I took the photo yet.


The original design has 1/16" balsa for the body and stabilizers, and 3/32" balsa for the fins.


For the rugged version, I used 1/16" plywood for the body and stabilizers, and 3/32" basswood for the fins.


The nacelle to hold the motor mount was 3/16" (BFS-60), so I just made it by doubling-up a pair of 3/32" pieces.
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  #2  
Old 06-02-2018, 03:24 PM
DavidQ DavidQ is offline
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I started by building the balsa version. My concern was that I wanted it to look like the yellow and red version, without the added weight of all that primer and spray paint. (You can see the design I was going after in the Falcon plans at JimZ's site .)

So, I considered some kind of dye or stain solution which should be very light. I've stained fins with Rit Dye before, and it works pretty well. But, I didn't want to stain after the rocket was assembled, because I was also concerned about the glue showing through the stain because the stain wouldn't penetrate the glue.


So, I used acrylic paints and lightly applied the color as a stain before assembly. I spread it on with a paper towel, and wiped it back off before it dried. The yellow was applied first, with a section masked off for the red, and then the red was applied.

I even applied thermal-setting monokote that I had cut into stripes. There was one section where the monokote would go, i.e. next to the vertical stabilizers, that I didn't apply until after assembly, because I didn't want it to interfere with the glue joint.
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  #3  
Old 06-02-2018, 09:30 PM
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ghrocketman ghrocketman is offline
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If you use colored dope for paint it is much lighter than Enamel.
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  #4  
Old 06-03-2018, 02:24 PM
DavidQ DavidQ is offline
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When assembling the vertical stabilizers on the thin balsa Falcon, I noticed the direction of the wood grain. It's horizontal, or nearly so. So, just looking at it will make it snap into a jillion pieces. In fact, it mounts to a rather small area on the horizontal stabilizer, so there's not a way to rotate the grain to make the 1/16" balsa strong enough.

I decided to take the wimpy stabilizers back off, and redesign them. It makes it not exactly like the 1964 design, but it would have been a change made before the second flight of one of these birds back in 1964.


I made a small leading edge out of 1/16" balsa. Then, I rotated the grain of the rest of the part so that it was glued directly to the leading edge.

After sanding and staining, one has to look very closely to see the difference.
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  #5  
Old 06-03-2018, 02:31 PM
DavidQ DavidQ is offline
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The ruggedized rocket was next.

Since it was all wood, and the woods looked better than balsa, I decided to give it a proper woodworking treatment. The pieces were stained with wood stain instead of paint. In fact, I gave it a two-tone appearance, using a darker stain for the vertical pieces, and thus a lighter stain for the horizontal pieces. No two-tone for a single piece, as I've not yet gotten good at marquetry.

The photos show the pieces laid out pre-staining, and again post-staining.

As with the balsa version, I stained before I glued. I usually don't do that with oil-based stains. But, I was really worried about the glues blocking the stains, leaving white wood spots showing through. The wood was thin enough that I didn't want to risk sanding too much. Instead, I used epoxy, which I figured would stick even with the stain.

I even stained the lug and engine mount tube, as well as the resin nose cone. They were good enough for my experiment.
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  #6  
Old 06-03-2018, 02:53 PM
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Sprint60 Sprint60 is offline
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Quote:
Originally Posted by DavidQ
When assembling the vertical stabilizers on the thin balsa Falcon, I noticed the direction of the wood grain. It's horizontal, or nearly so. So, just looking at it will make it snap into a jillion pieces. In fact, it mounts to a rather small area on the horizontal stabilizer, so there's not a way to rotate the grain to make the 1/16" balsa strong enough.

I decided to take the wimpy stabilizers back off, and redesign them. It makes it not exactly like the 1964 design, but it would have been a change made before the second flight of one of these birds back in 1964.


I made a small leading edge out of 1/16" balsa. Then, I rotated the grain of the rest of the part so that it was glued directly to the leading edge.

After sanding and staining, one has to look very closely to see the difference.


Interesting approach - Another method is to make a leading edge out of a strip of basswood. I've done that on Orbital Transport gliders (and other things) for a tougher edge that's less easily chewed up. The added weight is negligible and properly done can't be seen. In this case it would help with the grain snapping problem. A trick learned from the stick-and-tissue gang I ran with when I lived in Wichita.
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  #7  
Old 06-03-2018, 05:43 PM
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Nice project.

My first Falcon, in 1970, flight 1 it boosted up, then death dived down. After repairs it later shredded into DOZENS of pieces at about 100 feet up. And I never built one again.

Until 2016. I threw together one from plans, mostly as a guide for the real project, a 2.5X scaled up R/C model. It worked out nicely. I lengthened the fuselage a bit , made the wing a bit larger in proportion, and some other minor tweaks (including that rudder leading edge trick Tim mentioned, with a strip of basswood parallel to the edge). Servos under the wing roots, built into the fuselage. The pod is BT-60, holding an 18mm engine mount plus receiver and battery pack.

More info in this thread, with assembly pics and flight video: http://www.rocketryforum.com/showth...Glider-kit-K-13

Photo below with normal sized Falcon. Wings covered with iron-on model plane type covering.

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  #8  
Old 06-04-2018, 11:32 PM
DavidQ DavidQ is offline
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Here are the completed Falcons.

I made the decals based on the old Estes D-6 decal sheet. For the hardwood Falcon, I put a piece of adhesive Monokote beneath the decals so they would show up better.

The epoxy I used for the hardwood Falcon showed up a bit glossier than the surrounding wood. So, I shot the entire rocket with clearcoat so it all had the same glossiness. I didn't clearcoat the balsa version, so it would stay light weight.
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  #9  
Old 06-05-2018, 06:46 PM
BARGeezer BARGeezer is online now
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Looks good. My boost gliders always used to get scorched in the aft section from the exhaust plume. Keep us posted with the flight reports.
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