LOC Viper III

I have a question for anybody that has flown this rocket with its (3) 24mm motor mounts. I am wondering how much thrust the surface-mount fins will take without separating from the rocket . . . so, what motors have you flown in this rocket?

I have three motors I would like to try (F101) but don't want to shred the fins if I don't have to. Yes, I know these motors are not certified and would have to be flown on a TRA experimental day.

The LOC Viper kits actually use "fin wedge" mounting which is not the same as surface mounting fins. On the Viper rockets, the fins are glued (epoxy is best) in the "wedge" created between two of the motor mount tubes. This makes for a very strong fin to rocket joint.
I have a LOC Viper 4 (same as Viper 3 but with 4 24mm motor tubes) That I have flown with 4 G55 motors, your Viper 3 will take the F101s you have without a problem as long as you use good glue. I would also remove or roughly sand the glassine layer of the motor tubes where they join so the epoxy will "grab" into the tubes strongly.
One more thing: This is one time where you actually want to sand the root edge of the fin. You want to sand the root edge to a point so it fits snuggly where the two motor tubes come together.

hball55 said:

I have a question for anybody that has flown this rocket with its (3) 24mm motor mounts. I am wondering how much thrust the surface-mount fins will take without separating from the rocket . . . so, what motors have you flown in this rocket?

I have three motors I would like to try (F101) but don't want to shred the fins if I don't have to. Yes, I know these motors are not certified and would have to be flown on a TRA experimental day.

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They don't have to be flown on a TRA Experimantal Day, just fly them by yourself at a Non-Sanctioned Personal Launch.
I have yet to launch my Viper III, but between the Wedge Fins with proper Mating Surface Prep and Epoxy, and the JB Weld Fillets, I'de be comfortable stuffing anything that would fit in there.

I am doing a build on one of these now and I just attached the fins last night. I have done many Loc rockets, surface mount and wedge mount. Provided the fins are attached well anything you can throw at them should work. I epoxied mine into the wedge and will do epoxy fillets in the next day or two. My plans are to eventually fly this on 3 F50 Skid's or 3 F240 Vmax's, if those flights go well I will try 3 G100 Skid's. I see no problem with this holding up. My only concern is going to be heat. I have used JBWeld in my build process though, so I should be ok.

TopRamen said:

They don't have to be flown on a TRA Experimantal Day, just fly them by yourself at a Non-Sanctioned Personal Launch.
I have yet to launch my Viper III, but between the Wedge Fins with proper Mating Surface Prep and Epoxy, and the JB Weld Fillets, I'de be comfortable stuffing anything that would fit in there.

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He's right, you don't have to fly them at a sanctioned launch. The only thing is, if the total propellant weight is over 125g and/or the total loaded rocket weight is over 1500g (3.3 lbs) you'll have to get a FAA waiver to be legal.

Handeman said:

He's right, you don't have to fly them at a sanctioned launch. The only thing is, if the total propellant weight is over 125g and/or the total loaded rocket weight is over 1500g (3.3 lbs) you'll have to get a FAA waiver to be legal.

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Good Point. I have no Idea what the F101 Motors Weigh.

Thanks for the replies. There was a time when I would have gone out and launched on my own, but this being California and in a drought, I won't take the chance.

I flown my LOC Viper III on 3x F101's and wow does she move ! Its like a transporter first your on the pad and in the next millisecond your way up ! Nothing seen in the middle !

hball55 said:

Thanks for the replies. There was a time when I would have gone out and launched on my own, but this being California and in a drought, I won't take the chance.

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Sorry about "Launch alone" comment. I always seem to forget that California is hard to fly in at Non-events.

TopRamen said:

Good Point. I have no Idea what the F101 Motors Weigh.

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As a rule of thumb, Aerotech 80Ns motors have around 42 grams of propellant each. F101s are Blue thunder, which means they have slightly less than 42 grams because its ISP is slightly greater, so more like 38-40 grams.

3 F101s would still be under the 125 gram limit.

If you're in SoCal, you can fly with ROC at Lucerne Lakebed, or

LUNAR club in the Bay Area.

Since the F101 has more than 80 average thrust, they are considered High Power motors, and California has some old funky law that only recognizes model rockets as rockets that weigh up to 500 grams, NOT 1500 grams. You can get around this if you launch with certain clubs, like ROC and I think possibly LUNAR.