After about 35 yrs. of flights, I have finally grown tired of fixing the plastic fins on my original Maxi Alpha III. Over the years I have bought and built a few of these as deals have come along but as luck would have it, I held on to my original from when I was a kid. I don't have any idea how many flights it has flown but it is well used. At some point I did replace the body tube and decal as the tube had become soft over time with use.
Lately I've had a frustrating time flying this rocket as the plastic for the fin can has become brittle and the little tabs break off the fins on every landing regardless of how soft it comes down. After it's last flight at a club launch 6 weeks ago and yet another broken fin, I decided it was time to fix the problem.
When first built the rocket had it's correct Red / White paint job. When the tube was replaced about 20 years ago it got the Metallic Red and Gray that you see in the pic below. This was the last flight before the rebuilt.
To begin the build I tore down the original rocket and reviewed what was salvageable and what was junk. As expected the plastic fin can and all three plastic fins were trashed after years of field repairs so the only option was to ditch the plastic can / fins altogether and go with a traditional setup. I was able to save the original tube, nose cone and upper centering ring but everything else is new.
Parts list.
Original Nose Cone.
New Motor mount tube with Plywood upper ring.
BT80 body tube section cut to length to replace the rear plastic fin can.
Original fiber upper centering ring. This will now become the rear ring.
BT20/50 ring to use as a motor block.
Approx. 12 inches of 500# Kevlar.
BT80 body tubes. Can't call these original as they were replaced about 20 yrs ago.
BT80 Tube coupler.
Fins cut from 1/8" Basswood and papered using heavy notebook paper and epoxy.
First step in this build was to get the additional body tube attached. In this photo I have already inserted the BT80 coupler using TBII glue and let it sit for about 5 mins to tack up. I then applied glue to the inside of the lower body tube and the outside of the coupler and slid the two together. Excess glue was wiped away with a wet rag.
With the tubes drying I began work on the motor mount. The motor tube already had a plywood upper ring attached from a previous project that never happened. To start I tied a knot in one end of the Kevlar and threaded that through the hole in the upper ring. This was secured with some TBII and allowed to dry.
Next up was the motor block. My original kit was an early example that only allowed room for the D sized motors. This is probably why I was able to fly it for so many years and never lose it as it wouldn't go more than about 450ft. This time around I added the motor block at the 3.5" mark so I can fly the longer E motors if I choose.
Next came the motor retainer clip. This was added using T-88 epoxy. I added a small amount of epoxy under the upper 1/3 of the spring to attach it to the tube. A small strip was cut from the original motor mount tube and used as a sleeve to hole the clip in place. Note that the motor tube has been sanded where the spring and the fins will attach for better adhesion.
All of that cured over night so I will be cutting fins slots in the tube and beginning assembly today.
Lately I've had a frustrating time flying this rocket as the plastic for the fin can has become brittle and the little tabs break off the fins on every landing regardless of how soft it comes down. After it's last flight at a club launch 6 weeks ago and yet another broken fin, I decided it was time to fix the problem.
When first built the rocket had it's correct Red / White paint job. When the tube was replaced about 20 years ago it got the Metallic Red and Gray that you see in the pic below. This was the last flight before the rebuilt.
To begin the build I tore down the original rocket and reviewed what was salvageable and what was junk. As expected the plastic fin can and all three plastic fins were trashed after years of field repairs so the only option was to ditch the plastic can / fins altogether and go with a traditional setup. I was able to save the original tube, nose cone and upper centering ring but everything else is new.
Parts list.
Original Nose Cone.
New Motor mount tube with Plywood upper ring.
BT80 body tube section cut to length to replace the rear plastic fin can.
Original fiber upper centering ring. This will now become the rear ring.
BT20/50 ring to use as a motor block.
Approx. 12 inches of 500# Kevlar.
BT80 body tubes. Can't call these original as they were replaced about 20 yrs ago.
BT80 Tube coupler.
Fins cut from 1/8" Basswood and papered using heavy notebook paper and epoxy.
First step in this build was to get the additional body tube attached. In this photo I have already inserted the BT80 coupler using TBII glue and let it sit for about 5 mins to tack up. I then applied glue to the inside of the lower body tube and the outside of the coupler and slid the two together. Excess glue was wiped away with a wet rag.
With the tubes drying I began work on the motor mount. The motor tube already had a plywood upper ring attached from a previous project that never happened. To start I tied a knot in one end of the Kevlar and threaded that through the hole in the upper ring. This was secured with some TBII and allowed to dry.
Next up was the motor block. My original kit was an early example that only allowed room for the D sized motors. This is probably why I was able to fly it for so many years and never lose it as it wouldn't go more than about 450ft. This time around I added the motor block at the 3.5" mark so I can fly the longer E motors if I choose.
Next came the motor retainer clip. This was added using T-88 epoxy. I added a small amount of epoxy under the upper 1/3 of the spring to attach it to the tube. A small strip was cut from the original motor mount tube and used as a sleeve to hole the clip in place. Note that the motor tube has been sanded where the spring and the fins will attach for better adhesion.
All of that cured over night so I will be cutting fins slots in the tube and beginning assembly today.
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