I keep hearing about these Harbor Freight lathes. That might be something I look into if and when we move.

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II Semroc Cyber III

Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2

The one I have is from the same casting as the Jet JWL-1236. IIRC, the only difference is that the Jet casting is finished a little nicer and is slapped with a brand name that people are willing to pay double for.

A true woodworking hobbiest would have something better, but if you only plan to turn nosecones and transitions, they would likely tell you that the HF version of the Jet is plenty good for that purpose plus it ain't bad to do some other stuff too.

Here's a link to my lathe...if you decide to buy one, be patient and wait until it goes on sale!
Harbor Freight Lathe

Here's a link to the Jet lathe.
Jet JWL-1236

Thanks for the links tbzep!!! Back to the heavy one I have now, I will be buying some F series motors that use copperhead igniters. What sort of electrical system do these require? I understand from reading some other threads they are hard to get to work right everytime. Any advice on these? Should I buy some extra ignitors too as there are only two igniters included with the two F motors. Also, my 1x Goblin is finished except sealing, priming and painting. I put in a D engine to check the balance point as measured from the rear of the rocket. Estes plans say dont launch with the balance point less than 3 &5/8" from the rear, I assumed that meant with engine in the rocket and wadding, chute, etc, ready to launch. I checked mine at it was at the 3" distance with the engine and about 5" without the engine. Should I be worried enough to add some nose weight? Thanks again for all your help guys.

Copperheads...

I've never had any trouble with copperheads. They need 12v for good ignition. I don't use the Aerotech clip. I take the ignitor and split the copper leads so that they can be hooked up the normal way with clips. Make sure you get the head of the ignitor all the way to the top of the motor and you should be good to go.

You can split the copper leads by taking a lighter and heating the tip (not the end that goes in the rocket!) so that the plastic barrier between the two copper leads melts. I don't smoke, so I seldom have a lighter around. I usually just take an X-Acto knife and peel them apart. It's not hard, especially if you grew up pulling the aluminum foil off the wax paper of Wrigley's chewing gum wrappers.

1X Goblin...

You might try a swing test with the rocket fully prepped. It will probably fly as is, but it shouldn't take much weight to move the balance point up to 3 5/8". I would go ahead and add something just to be on the safe side if you plan to launch around other people. If you launch on smaller motors with a light weight adaptor, you probably won't need any weight at all.

I just checked my clone with a D12-5 and no wadding. It balances around 3 3/8". I've always flown it without adding weight.

Since the 2X is really too heavy to get the 4 second delay to work well on a E9-4, I am considering putting a light lower stage on it and running a D12-0 or an E9-0 in the lower stage with an e9-4 upper. The only things that might not make this work well is the amount of space from the back of the main rocket body tube to the first centering ring. It looks to be around 5/8". The other thing is the rocket is the center of gravity is sure to move back some and I wonder if it will be unstable. I would rather run it as a two stage than buy F motors for it. Any comments are appreciated.

If you make the fins larger than the ones on the sustainer, and still build it light, it will help a lot with the CP/CG situation.

The D12-0 will have a much faster velocity by the time it leaves the launch rod, making it more stable, less likely to tip over, etc. than the E9-0. You might want to run your design through a simulation program to see if it is moving fast enough when it leaves the rod. It will also give you a good idea how big to make your booster fins to know where your CP/CG should be.

Thanks tbzep! I noticed the D12 has a peak thrust of around 30 N and the E9 only 20 N, or there abouts. I dont have a sim program or have any idea how to run one. I suppose the bigger booster fins will push the CP back some by causing more drag? I dont have a two stager so this is a good reason to try one. These would be 25% bigger, would that work?
Thanks! I found this one on another forum.

I don't use sims to check stability myself. I use the "That looks about right" formula. It's never failed me! I always fly alone when trying out a new design that might be marginal, so I don't have to worry about my stability testing method failing me. I have used sims to predict altitude, just for fun.

As long as you don't use heavy materials and over do it with the glue, those fins "look about right". According to your construction method and materials used, it might or might not need a little nose weight.

Yes, the bigger fins will change the CP to your advantage compared to fins the same size as the sustainer. You can also use thicker fins such as 1/4" balsa, but you are probably more interested in altitude than I am. 1/4" thick fins will add considerable drag, but you get to see the D12 burn up close and personal!

I went ahead and bought two F21-4W motors to try this heavy dude out. I still may stage it later. I am hoping to get at least 850' on the Fs.

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I just found this thread.

I made the BIG GIANT Goblin nose cone shown earlier in this thread.

It was made for a " Rocketry Forum" member to fly on an EX motor...an L something I think.

The 8.2" diameter cone was made of 2" thick pink insulating foam stacked and glued then turned on a lathe to the correct profile.

It was then covered with two layers of 6 oz. fiberglass and West System epoxy while still on the lathe. (the lathe was covered with garbage bags to keep the drips off)

After the epoxy cured I turned the lathe back on and "trued" it up.

Notice the body seam below the nose cone. His body tube was too short (a Sona tube) and I had to make a straight section on the cone 6" longer to compensate. I left him a "seam line" at the top to seperate the yellow from the black.

And how much??? No where near enough! I think I made about $1 an hour on that job.

As for custom nose cones. The Goblin nose cone (BNC-55AO) in various sizes from Micro Maxx to 8" monster upscales are probably THE most popular nose cones I am asked to make.