Vaguely remember some details from when I read it some 30 years ago. Similar to the Three Investigators series, it involved some young friends solving mysteries and outwitting bad guys. It had multiple stories in one book. In one story, they built a “dragon” on a canoe and scared the townsfolk. In another, there was the big balloon race. In another there was a cannon that was filled with concrete but contained something important. Sorry that is as much detail as I remember.
Hardy Boys?? or Nancy drew? Those are the only ones I can think of-
Oh, man! I’ve read that book. Like you, it’s probably been a good 30 years. I want to say Encyclopedia Brown mysteries, but I don’t think that’s right. This is going to drive me batty now, until someone answers it.
Yeah!!! Brighon Nemo (a couple below me) has it!!! The Mad Scientists Club! Now I can sleep at night again!
I was going to say Encyclopia Brown
It’s not Encyclopedia Brown – I want to say the Alvin Fernarld series? They weren’t specifically “mysteries,” but they did catch a lot of bad guys – Alvin Fernarld and his friend (don’t remember the name, just that they called each other “Old Man” and “Old Bean”) were both child inventors, and they had all kinds of crazy adventures. One book they opened a “swap shop” where people could trade things for other things and ended up with a refugee boy who had a priceless stamp inside his treasured seashell and they caught some bad guys, another Alvin decided to be a superhero for the environment and climbed smokestacks to hang banners and nearly got caught (but caught the big bad factory that was polluting), I think in one they ended up running their own TV show/station and solved a 30-year-old bank robbery . . . any of those ring a bell? They were definitely from the right era, and I vaguely remember the “dragon” canoe scene you mentioned and the cannon-with-concrete (there was an Encyclopedia Brown mystery that found some priceless object inside a cannon, but that was a short story and I know he didn’t do any dragon canoes).
Those stories were from “The Mad Scientists’ Club” by Bertrand Brinley.