For those thinking of bashing a SW-II into a “one-holer”.
So, the subject of “bashing” (converting) the 84” wingspan 1/4-scale Sig Spacewalker II “two-holer” (two-cockpits) to the “one-holer” (single-cockpit) Spacewalker keeps poping-up in my head. Sig does offer a single-place Spacewalker kit, but only in a 104” 1/3-scale kit. Tom Crump gives us a very pretty example of Sig’s 1/3-scale ship here in his build thread while Les Uyeda has shared photos of his 1/4-scale SW-II kit converted to a single-cockpit beauty. I, like Les and a few other modelers, prefer the lines of the one-holer Spacewalker over the two holer. Why not just tackle the 1/3-scale kit? Well, I have a 1/4-scale kit on-hand as well as an engine, scale landing gear (Robart Cub gear). Also, I like the idea of having an out-of-the-ordinary model...
The conversion issue has been bugging me for the last couple of weeks. A bout of jet-lag got me out of bed really early the other day, so I pulled out the plans for my SW-II and laid them out. What I really needed were 3-view drawings of the two planes. The Sig build manual files (http://www.sigmfg.com/BuildManuals/
) contains 3-view drawings for both the full-size SW and the SW-II. Comparing the specs of the two aircraft, it appears that the designer took the SW and added an additional two-feet of wingspan and fuselage length. The single cockpit of the SW was brought forward towards the firewall (obviously to compensate for the rear cockpit) and the additional cockpit installed behind it. The SW’s 610-pound empty weight was brought up 150-pounds to the SW-II’s 760-pound empty weight, and the SW’s 65HP was brought up to 100HP for the SW-II.
I suppose that a *pure* bash from the SW-II to the SW would include removing the additional two-feet from the wings (6”) and from the fuselage (6”) to bring the model into a true 1/4-scale replication. At an 84” wingspan and a 60-1/2” length, the Sig SW-II is in fact (except an additional 1/2” in length) a 1/4-scale model of the full-size SW-II. The same can be said for the 1/3-scale SW. So it really comes down to how “scale” the bash becomes. I mean, the SW-II model is going to fly like the SW-II model regardless of it having one cockpit or two. Shortening the wingspan and fuselage length will make it a bit more “peppy”, but it is not going to be the difference between Clark Griswald’s Family Truckster station wagon (of National Lampoon’s Vacation movie fame) and a Chevy Corvette. I’d bet dollars-to-donuts that the difference performance-wise would be more like driving a two-door compared to a four-door sedan of the same model automobile.
I’m not going for hard-core scale competition, nor do I want to “reinvent the wheel” here. True enough, shortening the wingspan would only take the elimination of a wing rib bay on each wing, but shortening the fuselage by 6”, although possible, is just not worth the pay-off. I’ve adapted a credo from one of the scale builders in our club: “pick your battles.” Redesigning and building the entire aft portion of an already flight-proven design just doesn’t make sense to me. So, this bash becomes one of eliminating the rear cockpit and relocating the forward one rearward.
Tom’s SW-II build thread has great reference pics:
As you can see in the pics in Tom’s build thread, the fuselage is a square, open-frame box-like structure with stringers on the sides and bottom providing contour lines once the covering is applied. Several half-round formers are placed across the top of the fuselage with stringers attached to them running fore and aft. The fuselage is built in two parts, front and rear. Looking down onto the top of the front of the fuselage, it is rectangular, but does slightly taper (1/2”-outward) from the firewall to the rear of the front cockpit. The rear of the fuselage tapers from where it joins the front section of the fuselage rearward to the empennage. On the full-size SW, the rear of the cockpit opening is just forward of the fuselage square-to-taper joint. On the model, the front and rear fuselage sections are joined at the F-5 former. This is the perfect spot to relocate the front cockpit.
The rear cockpit and former F-4 is eliminated and the front cockpit on the model is shifted rearward 2-1/8”. Also, all the formers between the firewall (F-1A and F-1) to former F-10 will have to be re-fabricated. This is not as difficult as it may seem. One of the pics below is of the F-5 formers. Note that the original inked outline of F-5 - it is flattened on top. New F-5 formers will be cut with a round contour. This will give the F-5 formers continuity with all the other formers, and it will also act as an anchor-point for the stringers from this former rearward. With the top stringer to act as a guide, new former templates and formers can be made. A new F-3 former will have to be fabricated, and the top stringer between it and F1A will allow a new (and relocated) F-2 former to be made.
So far, until I put some of down on the building table from the “Box-O-Lumber” that this kit is, that’s about all I can think of that needs to be done to bash the SW-II into a “one-holer”.