How Would You Turn This?

[John Simmons]

One big reason I bought my lathe was to make model rocketry parts. I want to turn a body for a rocket I designed that is similar to a 1950's era design (see attached drawing below).

Looking for some advice on the best way to pull this off. Material is pine or basswood.

Would you glue up several pieces or turn this from one solid piece? What glue would you use?

Would you bore the inside first then the outside?

Would you use some sort of steady rest to hold the part for internal boring?

Thanks in advance..

 

[Bill Boehme]

I've drilled peppermills, but they don't need to be ultra high precision.

Can you drill accurately enough to insure that the holes will be concentric? The thing about pine, especially southern yellow pine, is that there is a very great difference in hardness between the early wood and late wood in the growth rings which can be a problem when drilling long straight holes because of a tendency to be pulled off center by the grain. it's a pretty deep bore. I think that basswood would be a better choice.

I don't think that a steady rest is needed if you have a good drill ... The most accurate would be a single flute drill like a gun drill, but they are usually smaller diameter than what you need. In the nose cone are the diameters and length (other than the 1.89") especially critical or are you just wanting to remove mass?

I think that drilling and turning the interior first would work the best and then turn a jam chuck to fit the 1.89" diameter to turn the exterior. Use the tailstock while turning the exterior. For the final turning I think that I would turn a 1" diameter mandrel and assemble the two halves so that you can fair the two halves for smooth aerodynamic flow. Will the fins have an airfoil cross section (Flash Gordon wouldn't have it any other way ) ?

Are you planning to actually fly it? Before retiring I was a "rocket scientist" (actually guidance, navigation, and control engineer) so I can appreciate the precision necessary to have a successful launch.

 

[John Simmons]

Thanks for the reply Bill,

Can you drill accurately enough to insure that the holes will be concentric? .

I think so but if I run into problems I could make the rocket out of more pieces to shorten the boring depth.

In the nose cone are the diameters and length (other than the 1.89") especially critical or are you just wanting to remove mass?.

Just removing mass. I use a program called "Open Rocket" to run simulations and determine optimal nose cone weight.

Will the fins have an airfoil cross section (Flash Gordon wouldn't have it any other way ) ?.

That would be ideal. This rocket should be large enough that I can sand an airfoil, or semi-airfoil into them.

Are you planning to actually fly it?

Yes. Simulation uses an E15 motor which should take it to about 500 foot.

I considered gluing up and turning the rocket from balsa wood. But having never done that I am envisioning it will be a problem, the glue will be so much harder than the wood it seems problematic.

Before retiring I was a "rocket scientist" (actually guidance, navigation, and control engineer) so I can appreciate the precision necessary to have a successful launch.

Very cool. What was your favorite project? Since this is flying on mid-power motors, is pretty heavy and the apogee is pretty low, machining precision isn't all that critical.

 

[Bob Sheppard]

Interesting project. I was into model rocketry when I was in high school.
I understand wanting to use pine or basswood for the weight, but they're not the easiest woods to turn to a smooth finish.
Fortunately, you're basically doing a spindle turning project, which is much easier to get a good finish on those woods than if you were bowl turning with them.
I hope you show pictures of the finished project.

 

[John Simmons]

I hope you show pictures of the finished project.

I'll do a build thread. Might be a while though, seems like lots of other home and auto projects are infringing on my turning time. :mad:

We got 12" of heavy wet snow last Wednesday and it tore up our Pinion Pine trees here. Lots of trimming to do. But.. more turning stock too.

 

[Mike Johnson]

I have built a number of rockets over the years being involved with the Pyrotechnic Guild International mostly 1, 2 and 3 pound black powder, strobe and whistle powered rockets. Most of my rocketry has been with the one time build it, shoot it and watch it explode type devices. I have also turned a number of tool sets for manufacturing the rocket motors and other accessories for the pyro items. Drilling the centers and having a solid mandrel to mount the bodies onto to allow turning the outside profiles would provide am accurate means of keeping all of the rocket centered on the lathe. I have various sizes of aluminum and steel mandrels that I use for this purpose when the need presents itself. Drilling a long straight hole can be a challenge depending on the wood, grain and sharpness of the bit. You may need to sharpen the drill bit several times and advance the drill bit and clean the shavings out of the hole often. Take your time and don't get in a hurry.