I vote for Semroc as well. In my experience, their minimum order is $10 and they don't charge for shipping.

Also, they absolutely have everything you could possibly need. Like the 24 mm motor tubes I bought from them, one of which I'll probably use in my Outlander when I build it.

Or if there's someplace local that sells inexpensive Estes rockets with BT-50 body tubes (inner diameter 0.950" or 24.1 mm), you could use a section of BT-50 as the 24 mm motor tube in your upgraded Outlander.

Or yes, you can absolutely roll your own 24 mm motor tube for your Outlander. Get a 24 mm motor, wrap it in waxed paper, then wrap it with cardstock. Once the cardstock begins to overlap, glue it to itself with a thin layer of yellow wood glue. Probably two or three layers of cardstock would be robust enough to use for a motor tube.

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John Thro, NAR #84553 SR
I was too old when I started! Now I'll *never* become a BAR!