Equivalant size 98 MM motors will have a longer burn-time for the same propellant variations,

For example a classic Pro75-6G is an M1590, and a classic Pro98-3G is an M1060. Pro98 also has a slightly longer smoke grain, if thats worth anything.

Other than that, im pretty sure Pro75 and Pro98 are functionally the same

The insulation on 98mm will probably be thicker as the burn times are longer. Also the casting tubes/liner are more expensive. And the cases have more aluminum in them and have to be stronger to resist the larger hoop and axial stress that the same chamber pressures would generate.

Edward

The hardware costing more makes sense, I think. I was just trying to decide if I wanted to look at paying $80-$100 more just to fly a 98 for my L3. Looks like I'll be looking for a 98-75 adapter instead.

Go with the adapter. 😉 You can use mine.

Definitely go 98mm - you have more options. If you want to fly a 75mm, you can always use an adapter. My L3 was built with a 98 mount and I can fly anything from a 54mm L up through a 5 grain 98 motor.

I agree. Though I have a 98-75 mm adapter that was built for an AT casing. Don't know how well it would work with the thinner CTI 75mm casings. I've flown both. You can ALWAYS step down, never up. But, Brett, either of the 5" PR rockets can handle either a 75mm (with adapter) or 98 mm. Just look at cost and simplicty for your L3.

Oh yes, the rocket will have a 98mm mount. That is NOT in question. I was just debating actually using a 98mm load vs a 75 for the actual L3 flight. I learned very early on that the biggest mount you can fit is the way to go. Built one rocket that I love with a 29mm mount (could have had a 38 ) and have regretted it ever since.

You're very good to go! Just let me know how I can help. 😉

. Built one rocket that I love with a 29mm mount (could have had a 38 ) and have regretted it ever since.

Better that than too big. Then you don't shred your fins and live to fly another day 😳

OTOH, you can get 5G 29mm motors now 😀