This Holland Hornet (HH) installation was the original power source. Note the rectangular firewall (above left) with provisions for attaching the four-bolt Cox TD tank. Cox TD installation (above center) with red fuel tank/motor mount.
The “coup de gras” of this design however, was the use of up thrust for a spectacular climb. In my readings, I noted that on a typ- ical flat bottom wing, the minimum drag was when the angle of attack was slightly negative, –3 to –6 degrees. NFFS Sympo- sium showed some models with a wing plat- form that tilted to a lower angle of attack under power and then to a higher angle on glide. The lower angle gave lower wing drag in the power phase and higher angle for more lift in the glide. Since Santa Cruz had a fixed wing platform, the only way to change the angle of attack under power and get lower drag and higher speed was to use up thrust and force the wing to fly at a slightly negative angle.
This went against conventional wisdom that promoted the use of down thrust to keep a model from looping. I reasoned the up thrust should give a near vertical climb and lots of altitude, but would it put it too close to the boundary margin of stability and go over the top?
Flight test showed this not to be a prob- lem, winning numerous local contests and, at the 1961 SWR, a third place and one OOS. Photos and text of Pulque and Santa Cruz were sent to Model Airplane News in No- vember 1960 for review. Then Editor, Art Schroder, published the pylon model in Sep- tember, 1961, but said he would be publish- ing Carl Goldberg’s Viking in May and it would not be good policy to publish Santa Cruz as they looked too much alike. Upon seeing this for the first time in MAN, I sent a set of plans to Carl expressing amazement how we could develop such designs inde- pendent of each other.
Radial engine mount with a Cox TD attached (above right). This configuration is for a pressure fuel bladder operation. The radial mount seen here uses the same mounting holes as the Holland Hornet.
He answered back stating that Santa
Cruz was sound enough and hoped FLYING MODELS would publish it. Of particular in- terest to him was the apparent use of up thrust. Quote” “... by having the wing at ap- proximately zero degrees to the engine thrust line, you probably can get an excep- tional rate of climb.”–CG. This feature was later added to the Viking kits with an ac- companying advertising campaign stating, “The New FAI Viking with UPTHRUST… the new principal which reduces wing drag in the climb to the minimum. No looping tendency.” American Modeler, page 51, July/ August 1964. Was Santa Cruz one of the first?
I left Ft. Huachuca in 1961 and Santa
Cruz went into 46-year storage where it re- mained until 2008 when I joined the Magnif- icent Mountain Men of Colorado.
Getting started again
If you are just getting back into freeflight, the following will be of particular interest to you as it shows a progression path that you could follow to get up to speed. The plane is competitive and will allow you to use your old Holland Hornets or Cox TDs to get back in the game with technology you are used to. This is how the evolution took place. After inspecting the contents of that stor- age box, it was evident that an upgrade de- velopment plan was needed to modernize Santa Cruz in progressive steps so I could learn fly again and readapt accordingly. The first step was to see if my 1961 old weight rules model, built by Lt. Ron Wigton, would still even fly. It did but struggled mightily at the 5,300+ feet altitude of Den-
ver. It was obvious that major issues had to be addressed involving powerplant up grades, weight reduction and aerodynamic improvements.
The weight was reduced by using lighter building materials and reducing the size of wing spars and leading and trailing edge stock. Thus was born Santa Cruz Mk. II. By 2012, some additional modifications were needed and that became the Santa Cruz Mk. III presented here. The engine na- celle was modified to take the transition from 1. Holland Hornet/ timer tank, 2. Cox TD with red fuel tank/motor mount and 3. Radial mount for engines with pressurized fuel systems. Elimination of the fuel tanks later saved much additional weight. The Mk. III at 7.5 ounces, weighs 1.75 ounces less than the original.
Powerplant transition, 1–3 above, caused
a big c.g. shift which was addressed by mov- ing the wing back along the extra length wing platform added for these tests to keep the c.g. at 75–78% of the wing chord, a loca- tion the model seems to like. The plane flies well with all three engine configurations. How much power can this model handle? Hank Sperzel has donated a more powerful NIB VA Mk II for flight testing to find out. An aerodynamic improvement was a thin- ner lower drag Neelymeyer airfoil going from 12% to a 9% thickness at Don De- Loach’s urging. Santa Cruz started life powered by Holland Hornets/timer tank. You may have several of them around, and if you use one of the repro versions of the Hornet, you’ll be able to com- pete in AMA events but not the SAM Nostal- gia event. Boosting Holland Hornet (HH) per-
Fuselage assembly showing one side, pylon and longerons (above left) in place. The second side, engine nacelle and rudder plus two extra longerons also
FLYING MODELS
are shown. The assembled fuselage, engine nacelle and wing (above right) build easily and quickly.
43
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68