Looking for methods to square the ends of fiberglass tubes 4" and 5.5"

[KevinT]

I would like to the get a better fit and close up some small gaps that existed where the body tubes come together. The end of the fiberglass tubes I have are not quite flush/perpendicular. What methods do you guys use to flush the ends?

I was thinking of machining a ring about 1" rim and about 2" thick with a hole that matches the diameter of the tube. Slide it down until just the tube end sticks out, secure in place and use a block sander to level it out. This would be a lot of work.

What would you suggest?

 

[Steve Shannon]

I just wrap it with a piece of thick paper and use the edge to mark a square line around the tube. Then I use a block sander or file to sand or file to the line. It’s really not much time at all. If it’s taking too much time use coarser sandpaper. Finish with fine.
Once it’s close you can put the body tube together with another piece of body tube on a coupler and then you can see high points and touch them up.

 

[David Schwantz]

Belt sander with fence. I also have a piece of sandpaper glued to glass that is mounted on a table. I just rotate the tube, paper or fiberglass, with pressure on the side that I need to.

 

[OzHybrid]

I just wrap it with a piece of thick paper and use the edge to mark a square line around the tube. Then I use a block sander or file to sand or file to the line. It’s really not much time at all. If it’s taking too much time use coarser sandpaper. Finish with fine.
Once it’s close you can put the body tube together with another piece of body tube on a coupler and then you can see high points and touch them up.

Thick paper is your friend. Also useful to wrap around a tube to measure the circumfrence to find out what the actual diameter is. When you measure tube with verniers it tends to squeeze the tube. Which when you print a part the wrong size is unfortunate.
Norm

 

[KevinT]

All good ideas. I think I will start simple with marking the circumference and hand sanding. I try it this weekend.

Unfortunately I don't have a belt sander. But I like that approach too.

 

[tsmmiller]

I use a drywall sanding screen. I place it on a granite block and then rotate the tube on the screen. It makes short work, requiring just a couple of laps. I then use sand paper to fine tune the edges. The granite block is smooth enough that I also use it to check for squareness with .001 shim stock.

 

[David_Stack]

I knew I'd seen a post previously where a modeler had fabricated a 'tool' to accomplish this task, just took a while to find it...

Take a look at this (only viable if you have an excess tube with a factory cut end on it): https://www.rocketryforum.com/threads/cut-tube-ends.160609/#post-2023540

Admittedly, it may not be viable for tubes the size you are dealing with.

 

[ep29030]

I remember Jim Jarvis had a method he used to get very straight ends on his carbon tubes. Go to the middle of this long document to see how he did it: http://www.rocketryplanet.com/index2.php?option=com_content&tas (raketenmodellbau.org)

 

[MidOH]

Dewalt Miter saw.

 

[Steve Shannon]

I remember Jim Jarvis had a method he used to get very straight ends on his carbon tubes. Go to the middle of this long document to see how he did it: http://www.rocketryplanet.com/index2.php?option=com_content&tas (raketenmodellbau.org)

I think the best I’ve seen is the one John Coker designed nearly 20 years ago that turns the tube against a tile saw. The tube is held from inside rather than the other end butting up against something.

 

[KC3KNM]

If you've got a 3D printer, something like this is easy to whip up and works pretty well with little to no investment. Same idea in your original post basically (though you spin this one to sand the end down), but without having to machine it.

https://www.rocketryforum.com/threa...s-made-with-a-3d-printer.166879/#post-2153205

 

[JimJarvis50]

I remember Jim Jarvis had a method he used to get very straight ends on his carbon tubes. Go to the middle of this long document to see how he did it: http://www.rocketryplanet.com/index2.php?option=com_content&tas (raketenmodellbau.org)

Actually, there was a second article with an improvement on the original method. It's early in the article.

https://www.raketenmodellbau.org/repository/archive/167793?view=true
This method is applicable if you want very precise square tubes. Most rockets don't need that, but I have rockets where it's necessary. The method is not hard once it's set up.

Jim

 

[3stoogesrocketry]

If your rocket is already built , slide the two sections together till they touch. Then as your force the two sections together , rotate / twist the tube to form a friction sander . It will literally take less then a minute to have a perfect joint.

 

[OzHybrid]

Actually, there was a second article with an improvement on the original method. It's early in the article.

https://www.raketenmodellbau.org/repository/archive/167793?view=true
This method is applicable if you want very precise square tubes. Most rockets don't need that, but I have rockets where it's necessary. The method is not hard once it's set up.

Jim

Brilliant article Jim. Lots of good practical detail on how to achieve accuracy with some basic methods. What's the timeline from start to finish? A month full time at it is what my gut says.... What was the reality?

 

[JimJarvis50]

Brilliant article Jim. Lots of good practical detail on how to achieve accuracy with some basic methods. What's the timeline from start to finish? A month full time at it is what my gut says.... What was the reality?

Thanks. I have no idea how long those rockets took, but maybe a month full time would be close (but I just did evenings and weekends, so clock time would have been longer). There are things in the articles that I would no longer recommend, but I still use the laser method for squaring tubes. I had to check back, but the rocket from the article was my first flight to just barely 100K. It would have gone to 120K or so, but an altimeter bug that was not previously known caused all of the charges to fire at around 95K. The nose cone was recovered, but the remainder of the sustainer was lost. Sigh...

Jim