Fully armed and ready to go.

The three Estes rockets ride on rails that are mounted above the fuselage. We thought that there might be some problems with the nose pitching up too much on takeoff because of the off-center drag, but there was no noticeable problem. The rockets are mounted approximately at the CG, so there isn't any balance problem associated with the loss of weight in-flight due to launch.

All three rockets can be launched individually and are completely independent. The voltage on the rocket igniters is 9V, with three 9V batteries in parallel.

We decided that it would be much easier to use two radios instead of just one, so the second radio is Sam's Hitec with his micro-receiver. The addition of the second radio adds a bit of weight, but it vastly decreases pilot workload and radio complexity.

Side view

The rockets are elevated just enough to clear the prop, and are angled up slightly.

JATO engines ready to burn.

The six D-12-7s are held in a plywood mount that is attached to the bottom of the fuselage, just behind the main gear. All of the igniters are independent, but are controlled with a single switch.

The power supply is the same set of batteries that we used on the rockets, except that two of the batteries are in series, while the third is in parallel, giving 18V and high amps. 

We hope that the flames from these suckers won't burn the covering off of the tail, but we'll just have to see. 

We are slightly concerned about the off-center thrust provided by the JATO, but we will probably test it at a relatively high altitude (>50ft) or medium airspeed, so there shouldn't be much risk at all.

The two servos that control all four micro-switches are also mounted under the fuselage.

Here, the Weed Wacker is seen climbing-out with a full load of rockets (three rockets and the JATO's). It was about as heavy as it can get (40+ lbs) without actually needing the JATO's  for takeoff. By the way, it was about 100 degrees F with very high humidity, so it would have had a hard time flying even if it wasn't loaded up with rockets.

Our first attempt at shooting three Estes rockets from the top of the Weed Wacker was unsuccessful because we forgot to arm the rockets.  The conversation went like this: Sam -"Did you arm the rockets?", Ben -"No, did you?"

I made an attempted landing so we could arm them on the ground, but the airplane was too heavy for a safe landing because we weren't able to launch the rockets or burn up the JATO and it had a full tank of fuel.

The landing gear was bent and the prop broken, but at least the rockets are OK. Now we know that the Weed Wacker can actually fly with all of that stuff hanging out in the wind, so the mission wasn't a complete failure. The brown thing under the wing is our dog.

JATO Smoke.

On our latest attempt to shoot all of that crap from the Weed Wacker, we were for the most part successful.

  Sam and I hauled the plane up to the runway and got mom (to take pictures).  The engine started easily and I taxied for takeoff while Moe was trying to catch the dog.

  We expected that the plane would be really doggy on takeoff and climb-out, but the performance was OK.  The reason for the improved performance was probably the fact that it was about 15 degrees cooler than last time we flew it.

 I flew it around for the first firing and Sam launched while mom took the pictures. The first rocket had bent fins, so it was really squirrelly and was lost in the corn. The second rocket was a good one and flew straight, fast and far, but it was also lost. The third, and last rocket fired and flew OK, it was lost in the corn. Next we try the JATO, but only one ignited because our power supply wasn't powerful enough to fry all six igniters at once. 

Yes, we had better luck than last time, but we hope to have the best of luck next time, and get those JATO's roaring!

Before this flight, we had an interesting occurrence in the shop, while fixing the launch switches.  Sam was under the plane, I was standing behind it and various other people were standing all around it. I told Sam to hot-wire one of the switches, and he did, but he held it to long and...WHOOSH!  The biggest rocket was ignited and screamed towards the combine.  The high-speed projectile slammed into the side of the combine and made a 90 degree turn, out of the shed it goes. The rocket then proceeded to travel another 100 yards and left bits and pieces all over.  The only harm done was that the rocket was totally destroyed, the combine now has even more burn marks and I got some hot exhaust up my nose. It was sorta funny though.