AMRAAM Aim 120

[biziedizie]

So I bought this today and plan to fly it today. It's another one with nose cone weight and I'm wondering if I should put all the clay in the cone?
Anyone here build one and if so what was your experience?


Steve

 

[rocketkid88]

just my 2cents, but try www.rocketreviews.com and see what other ppl have said about it.... EMRR is a great place!

 

[Missileman]

On the one hand I have an AMRAAM, it is high power 2.1" dia.
I didn't have to add any weight at all and it flys like a charm.
On the other hand, Kit manufacturers typically supply the proper amount of nose weight with the kit and all of it should be used.
A suggestion is wait until the end of construction to balance your rocket.
Use Rocsim to find center of gravity or give it the old swing test.
ie. tie a string about 5 or 6 feet long at the balance point of your rocket and swing it in a circle around you. It should stay pointing nose first, if it doesn't add nose weight until it does (note: this should be done with engine, or equivalent weight, installed and chute packed)
Oh and WELCOME to TRF

 

[slim_t]

Welcome to TRF.

So what type of kit is it? If it is an Estes, I'd use all of the clay. As for other kits I can't say for sure, but I would think they would include the right amount of clay, so I'd probably use it all.

Tim

 

[biziedizie]

Thanks for the welcome guys Yes it's an Estes. Hey click the link above, looks like he shut it down.
I'm going to try the swing thing as I've never done it before, sounds cool.
We had a Bull Pup where the clay shifted in flight and it went ballistic and came right back at us under power Scared me and my 6yr old pretty good.


Steve

 

[powderburner]

If this is your first swing test, I would like to offer a few more tips.
Use as much string as you can manage without dragging your model rocket on the ground when you start and stop your swing test. You will get more speed and a smoother path.
If your rocket is marginally stable a swing test may be inconclusive----the rocket may tumble around and not point forward very much. Kind of hard to tell the difference between slightly stable and totally unstable.
I would strongly recommend that you follow the insertion of clay (at the tip of the nose cone) with a layer of epoxy. Belt-and-suspenders, and all that.
An alternative check: have you ever heard of the cardboard cutout method of determining center of pressure? Find the center of gravity by balancing the model on something (make sure the rocket is loaded in flight condition, with wadding and motor). After noting the location of the C.G., find the center of pressure by making a cardboard cutout of the profile of your rocket and balancing that cardboard piece. The pivot point of the cardboard represents the lateral (or, 'from the side') centroid of the area, and is usually a conservative estimate of the C.P. If the C.P. is one to two body diameters behind the C.G. then you are probably OK.

 

[biziedizie]

Powderburner, Thank you, thank you, thank you! You just explained to me something that is very hands on that will make me think as I scratch build.
I'm going to try this in the morning.


Steve

 

[loopy]

So that's what the cardboard cutout method is. Thanks, man!

Loopy

 

[powderburner]

If you want to see an example of a cardboard cut-out used for C.P. estimation, jump over to another thread currently running on TRF:

https://www.rocketryforum.com/showthread.php?threadid=6948

On the second page Micromister has a post with a cardboard cutout for a model of an X-15:

https://www.rocketryforum.com/attachment.php?postid=75502