I chose the 38 casings for my investment into HP reloadable motors. You
can fly from G's (38/120) to J's (38/720 and 38/1080). The 29mm casings
don't really cover the L1 range well at the top end. The 54's are all J and
up, as far as I know.
The H123W is a very nice choice for that rocket with the 38/240, though
not on the recommended motor list.
The post by Larry described the four different loads each one will take
nicely. I like the Redlines and the BlackJacks myself. In general, the
BlackJack will have the lowest thrust (slowest burn) and impulse for a given
casing. The Redline and White Lightning are moderate thrust and impulse,
and the Blue Thunder is a very fast burn with high thrust and total impulse.
If you multiply the weight of the rocket in ounces (loaded, ready to
launch) by 1.4, you get the minimum average thrust in Newtons recommended
for the rocket to maintain the 5:1 thrust to weight ratio for safe liftoff.
Rocket Weight (in ounces) x 1.4 = Minimum average thrust (in Newtons)
My Tomahawk was about 100 ounces (with the motor - you have to estimate
first then confirm when you choose a motor) so I would pick a motor with at
least 140 N of average thrust to launch it. An H148R would be rock bottom
minimum thrust for 5:1. A J90 would not be enough thrust to safely launch
The ezi-65 has a published weight of 35 ounces. Using 42 ounces as a
reference with a motor (G61W is about 7 ounces), the minimum recommended
average thrust for the motor would be 42*1.4=59N. Any 38mm motor will
launch it with enough authority for stable flight, even the G61W (check the
weight) or G67R. Some of the big Blue Thunders will have it close to Mach
1. The I435T will launch it at 54 g's in the simulation. The EZI-65 is a
light HP Rocket. Look for the lower thrust motors (my opinion).
The number after the slash is the approximate maximum impulse that the
particular case will accomodate. Each increase in impulse of 120 Ns is
38/120 = 1 grain (G motor)
38/240 = 2 grain
38/360 = 3 grain
38/480 = 4 grain
38/600 = 5 grain
38/720 = 6 grain (full I and low J)
38/1080 = 9 grain (upper J)
All of the enclosures for a particular size have the same fore and aft
fittings, even between AeroTech and Dr. Rocket. You only have to by one
full motor (tube and closures) and then just the case (tube) for every other
motor you would like.
I launched a 3" PML AMRAAM on an H148R for my L1 with a borrowed 38/240. An
I161W in my 38/480 case was also a nice AMRAAM launch. My first dual
deployment a couple flights later with the PML Tomahawk on an I195J, also in
my own case - 38/600.
Al's Hobby http://www.alshobbyshop.com/store/index.asp had a 25% off thing
going on this summer, maybe until September. I picked up the 240, 360, 480,
600, and 720 casings for about $200. All except the 600 - which is a
Dr.Rocket - are Aerotech. The special is not listed on their website now,
but you may want to give a call.
> I have purchased the ezi-65 with intent to certify level 1. Which
> motor choice is best? It can accommodate a 29mm, 38 mm or 54mm motor.
> I am looking for versatile, cheap, and reliable. I know-pick two, but
> now all three. I am looking at the RMS 38/240 case with an H-123W
> reload. Is this a good choice? Also, what does the second number
> after the forward slash mean in the case size? For instance 240?
> Is there a choice of case that will accommodate an H or and/or I motor?
> I appreciate the help.