Conversion to a 3 motor 18mm cluster isn't that difficult and flys like a bat outa you know where! I've worn out 4 or 5 of the Estes SR-71s over the years. It was important to devise a way to vent the outboards into the core as one of the earlier models failed to ignite the core motor while the two outborad booster -0 motors went. Great...Wonderful high flight.... very very bad ballistic landing
Since then All the SR's have been very nice flyers.

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