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Why do you need something custom? A set of drill bits in 1/64 and/or metric will give you a really good idea of your nozzle size.

I am not aware of any tools that can properly simulate a rocket like this, but my experience is that saucers with extended forward sections like this are not stable. Launch with care, and be sure to reply with a launch report!

There is quite a bit of misinformation in this thread: Pyrodex is the brand name of the first black powder substitute. Many people use it as a generic term to apply to all black power substitutes, but this is both incorrect and dangerous. Black Powder (and BP substitutes) are always...

My suggestion would be to use a larger, heavier rocket with the smallest motor recommended for it.

I fly MPR almost exclusively and there is not a great selection of tubes for MPR. There is no need for fiberglass, and just about all commercially-available paper tubes are either too flimsy or too heavy. Rolling my own gives me the exact diameter, thickness/strength, and length I want.

Paint is a really interesting cost. When you are building a kit, the finish work represents a substantial percentage of the overall time required to build a rocket -- assuming you are going for a good finish. And given the cost of the kit, plus the cost of a commercial reload, why wouldn't you...

Of course, if you are willing to roll your own paper tubes, cut your own centering rings, and turn your own nose cone, your parts cost really is just a few bucks. There is absolutely no need for fiberglass until you get to HPR, and people have launched I-class motors with Estes body tubes. The...

It is worth noting that pressure alone doesn't say too much. You need to know the volume of your storage tank and the volume of your launch tube for it to be at all meaningful. The diameter of the valve can also be a seriously limiting factor as well. I cannot recall the weight of my rockets...

What do you drive that gets 50 mpg?

Several of us have been doing compressed air rockets for a while now. Check the archives for more details. My interest in compressed air rockets was driven primarily as a means to quickly and easily test my homebrew flight computers. As such, all of mine were purely functional and had nothing...

I'm really surprised there have not been more suggestions of the sub-compact + roof rack solution. You can safely transport large HPR rockets this way by building a custom case for them with PVC pipe. Use the smallest size required for the body, and then use a transition to use a larger pipe...

I advise against the use of a 555 timer as well. It will get the job done, but it becomes very difficult to make it failsafe. I *strongly* suggest going the microcontroller route. These days microcontrollers are only slightly more expensive than 555 timers, and there are many cheap/free...

As others have said, a scale is essential for scratch-building. Weigh all of your raw materials and enter them into the OpenRocket/Rocksim parts database. As you build, weigh each assembly after gluing and enter the override value to account for the weight of glue. As you gain experience...

I also fly homemade electronics. The key is to have reliable backup deployment until you have thoroughly tested your electronics. If you are flying LPR, using motor ejection is generally sufficient as a back-up. You will probably find that when doing LPR electronics your biggest difficulty is...

Kevlar does burn, and it also abrades much more than metal. If I happened to have some scraps that were stout enough, I wouldn't hesitate to use them for lpr/mpr, though.

My favorite low-and-slow is a 4x upscale Gyroc flown on E-F motors.

I am pretty sure that the addition/substitution of any homemade parts will result in an uncertified motor, and you'd only be able to launch it as a research motor.

Piano wire is generally a higher grade of steel, usually a hardened+tempered spring steel. It will be much less ductile than coat hanger wire, though quite a bit stronger. If you are looking to shave every fraction of a gram of weight, piano wire is certainly the way to go. Indeed. I am a...

I've been doing the same thing with coat-hanger wire for years now. After inserting the "U" al the way through your bulkhead, bend the ends toward each other at sharp 90 degree angles with a pair of pliers. Basically you want to form a "D" shape where the upright of the D is doubled-up. Clip...

I regularly use 24 grit sandpaper to rough-shape styrofoam nose cone forms. I use it much less now that I have a hot wire cutter, though.