Figure 1
The first mock-up in the Sprint 90 showed exactly how difficult the build process was going to be. The motor was HUGE compared to a Zenoah or QD25. The cowl would need massive reconstruction to clear the head and CR80 sized tuned pipe. Motor mounts would also prove challenging with stringer extensions needed to pick the forward mounting points. It was clear that the Sprint 90 hull was not going to work.
I tried a cyclone 45 and a cut-down Avenger before stopping and asking advice from others on what to do. Three cat hulls and nothing but disappointment. My challenges were finding a long and wide enough hull to handle the power, a tall cowl to enclose as much of the motor as possible and a long cowl opening to allow the motor to mount forward. Part of the challenge is the motor attitude as it’s mounted in the hull. Unlike 99% of other gas motors, the magneto assembly is mounted on the output side of the engine making it difficult to tuck in low in the hull. This also greatly affected where the stuffing tube was positioned. It forced a high angle (15 degree) and forward position (36% CG) to make a nice transition to the strut.
I searched some more and talked with Jeff at Insane, Ron at RC Boatworks and several friends who knew a lot more then I did. I eventually decided on a Stryker F-41 with the Armadillo cowl from Rigo and Ron RC Boatworks. On the first mock-up I knew this was my best chance without waiting for a longer cat from Europe which I knew little about.
So here is what I used to rig the Stryker cat:
Engine: CMB 35Rs Ringed
Mounts: CMB 5” rubber mounted
Strut: Ballantine CD1 cat strut with integrated water pick-up, anodized green with laser etched flames
Rudder: Ballantine 5” wedge rudder with matching graphics
Fuel: 500mL IV bag with quick-fill system
Radio: Futaba 3PKS
Servos: Futaba S9152 for steering, S9451 for throttle
Here is a photo journal of the build-up and fabrication:
I first mounted the Ballantine Strut and rudder per RC Boatworks instructions.
