Original Design / Scratch Built
Contributed by Larry Brand
I have built a 1/20 model of the Yeager Bell X-1, "Glamorous Glennis" as a prototype for scale competition. Although it needs more work in the details department, it is dimensionally spot-on exact 1/20 scale. It flies very well on Aerotech E30 motors. It was simply constructed by using the parts from the Estes "Canadian Arrow" kit (a modified V-2), and the basic concept could be used to make a larger one from any size V-2 kit (as you need the cone and boat tail). That said for this model to work, a number of restrictions need to be followed:
- Nose cone ballast is 250g minimum.
- Maximum empty weight is 475g.
- The Aerotech E30-4 or E30-7 are the only approved motors.
- Do not airfoil the wings! No lift is needed. Only rounding edges is required.
- All surfaces and thrust line are 0-0-0-0 to each other. CG must be at leading edge wing root. The model is only marginally stable as one would expect, thus a short burn is critical.
Deviate from these instructions and earthworms will die.
Construction and Finishing:
The Estes "Canadian Arrow" kit was a donor for the fuselage components: wings and tail surfaces are of balsa and light plywood. Dimensions are 1/20 scale:
- Tip-to-tip wingspan is 16.5" for the model vs. 336" for full-scale.
- Nose-to-tail length is 18.5" for model vs. 371 for full-scale.
- Fuselage diameter is 2.56" for the model vs. 51" for full-scale.
- Tip-tip span of stabilator is 6 7/8" for model vs. 136.6" for full-scale.
Documentation came from Wikipedia. With some effort, this 1/20 scale X-1 could compete in NAR Super-Scale, since air-dropped rocket planes are exempt from the launcher requirement and Yeager actually launched "Glamorous Glennis" off the gear in 1949 (to Mach 1.03) without the B-29.
All construction utilized 5-minute epoxy. I hope the photos are helpful, however, the construction is quite straightforward. Body tube from the Estes "Canadian Arrow" was cut into 3 sections of 5", 3.5" and 3.5". The latter two sections were to use as doubler and tripler to reinforce the 5" main body tube and to accommodate the hips of the nose cone and boat tail. All but 3/8" of the hip of the boat tail was cut off with a razor saw. The nose cone was ballasted to a total weight of 250gm with lead split shot epoxied into the tip. The kit centering rings were used with 2 layers of 1/64" ply epoxied on as doublers. The kit motor tube was replaced with 6 5/8" of LOC 24mm tubing. Each wing was cut from 1/4" balsa to dimensions of 7" x 2"(tip) x 3"(root) with a 1" x 1/4" tab centered at the root for through-the-wall attachment at slots cut into the reinforced body tube. The entire wing was laminated on the upper surface only (including the tab) with 1/64" ply veneer. Scale speed on the E30 is 2470 mph (far faster than any X-1 ever flew) so it needs to be strong or the wings will come off.
- Motor tube with Estes motor hook added in the usual way was attached to doubled centering rings and epoxied into boat tail (measuring first for fit). A 1/8" hole was drilled into the upper centering ring and 8' of para cord passed through and anchored with a knot for recovery system.
- 5" piece of body tube epoxied to boat tail, followed by the two 3.5" doublers inserted into the body tube to rest against the boat tail centering ring. [Note: a 1/2" strip is cut from each 3.5" piece, so they fit inside the 5" piece.] Use ample epoxy when attaching doublers.
- Using an X-Acto knife or similar, 1/4" x 1" slots are cut through the body tube to place the wing leading edge 1.25" from the front of the body tube and equidistant from one another. The slots must be located precisely to assure zero incidence.
- Wing leading edges were rounded but not airfoiled. It was calculated that lift generation by the wings at the 125mph flight speed would make the model unstable in climb.
- Wings were epoxied into the slots with care to assure zero incidence and zero dihedral.
- Vertical and horizontal stabilizers were cut from 1/8" light plywood to the following dimensions:
Using these scale dimensions, I then "fiddled" with the Wikipedia 3-view drawing using the controls of an enlarging Xerox machine until I obtained the stab and tail outline I wanted to the proper scale. These templates were used to cut out the parts.
- Stab dimensions: 6 7/8" span and 15/16" tip chord.
- Tail dimensions: 4 ¾" aft span, 4 7/8" front span, 1 15/16" tip chord, and 3 ¼" root chord.
- Slots 1 ¼" deep were then cut in the stab leading edge and tail trailing edge at mid span with a sabre saw and the two parts were pushed together with epoxy for bonding.
- Tail surface assembly was then epoxied flush with the aft boat tail aligned at zero incidence to the wings and parallel to them using the TLAR method ("That Looks About Right"). Resist the urge to throw in a little positive stabilator incidence to offset the pitch-up moment under power--you'll just screw it up. Zero-zero works fine. Balsa triangle stock was used to fair the tail to the body and to reinforce the glue joint.
- ¼" x 3/8" balsa strips were used to construct the scale dorsal and ventral hydraulic conduits.
- Launch lug consists of a 4" piece of brass tubing epoxied to the ventral surface alongside the balsa "conduit" with its forward end even with the wing root leading edge. [NOTE: Use this forward end point for CG balance.]
- Model was painted with Testor's orange spray with the canopy represented using black trim Monokote and period decals borrowed from a 1:48 scale Revell F-106. Panel markings, gear door outlines, and control surface outlines were represented with a Sharpie black marker pen. All markings (including Yeager's hand-painted black "Glamorous Glennis" on the nose) are those of the period immediately following the famous supersonic flight and are not those of the original now on display in the Air and Space Museum at the Smithsonian, which was "gussied up" for publicity photos with more elaborate red/white lettering and USAF decor.
- The recovery system consists of a 24" Top Flight "Lite" chute attached to 8' of para cord with a medium Nomex® heat shield attached.
- The balance point for flight on the E30 was set at the wing root leading edge, based on recommendations from the rocketry literature and from numerous arm-chair Bell X-1 pilots operating at our field.
Flight and Recovery:
The only recommended motor is the Aerotech E30 with either 4 or 7 second delays being OK. Possibly the similar Aerotech E28 reload would work, but I haven't tried it and it is somewhat heavier.
First flight was on an AT E30-4 at the PlasterBlaster 2005 event. It was flawless with only a slight pitch-up moment developing under power that damped out on burnout. Recovery on the 24" chute was perfect if slightly early. Estimated speed was about 125 mph to 450', based on simulations. A second flight using an F21-4 ended with an auger-in under full power with total loss of vehicle. I never realized a thin Estes nose cone could punch through 6" of hard desert playa. The pitch-up moment that doesn't develop in only one second under power develops fully in two seconds. Only the stab survived and I have since rebuild my X-1 with nicer detail and it flies just as well too. So stick with the E30, please.
PRO: For a scratch scale model, the Bell X-1 is not difficult to build at all. It is the only Bell X-1 rocket model design available that I am aware of, although I think there are R/C X-1 plans available. It flies very well if the restrictions are adhered to, namely using the E30 only and weight/balance followed. It qualifies for max scale points for NAR Super-Scale since the launcher requirement is waived. It is one of the easiest Super-Scale competition models you can build.
CON: Only one motor choice. The "Canadian Arrow" kits from Estes seem easy to find but that could always change. Any V-2 rocket model could be used similarly to create an X-1, although with different scale factors (and of course you would be the test pilot). The contours of the forward fuselage are not quite those of the X-1 but dimensionally they are 1/20 scale.
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