Here's a little lesson on rocket motors. There are two things to consider: how much thrust in Newtons (or, alternatively, pounds-force) do I need to actually overcome gravity and lift my rocket? And, how long do I want the motor to burn, which generally indicates how high it will go.

If you look at an A8 vs. a B6, you will see that the A8 has considerably less thrust than the B6. The A8 has 2.3 N of average thrust, and it burns for 0.7 seconds. When you multiply these together, you get the total impulse of the motor, which is 1.61 Ns (or Newton-seconds). This makes it fall into the A impulse class., which is 1.26 - 2.50 Ns.

The B6 has an average thrust of 5 N, and it burns for 0.9 seconds, giving 4.5 Ns of total impulse (Estes lists 4.3; I haven't figured that one out yet). That puts it in the B class, which is 2.51 - 5.00 Ns.

For the altitude, notice that the 4.3 Ns of impulse for the B6 is more than twice the 1.61 Ns of the A, meaning that it will go more than twice as high (for all general purposes, thought there are many other factors that affect altitude). In fact, it should go 2.67 times as high.

But we have ignored, so far, the other number, which is the average thrust. Notice that the A8 has an average thrust of 2.3 N. Estes recommends a thrust:weight ratio of 3:1 for a safe launch, but most clubs will require at least a 5:1 ratio.

There is a formula to calculate whether or not your motor has enough thrust to safely overcome gravity and lift your rocket off the pad. 1 ounce-force is equal to 0.28 N. So multiply your rocket's total, loaded, flight-ready weight times 0.28, then again by 5 to get the 5:1 ratio.

I looked at the estimate weight of the Riptide, which is 2.7 oz. That probably does not include wadding or the motor. If the weight of your rocket is, say, 3 oz., then: 3 * 0.28 * 5 = 4.2 N. Thus the A8 would not meet the required average thrust to safely lift this rocket. However, the 5 N of the B6 would.

I'm sure the Estes 1/2A motors have even less average thrust, which means they are, as Monty Python would say, right out!