Saturn V Massive Build

[Retired_for_now]

Strength of the glue joint is primarily determined by the glued contact area. Here's a thought to maximize the glued area:
build strong psi-tube (done);
glue a one-inch wide strip of paper inside the top of the tube (large glue surface to the tube); glue in many layers of that strip to provide ample bearing surface for the plug (ending up with a substantial shelf inside the top of the tube for the plug disk to seat against);
laminate many layers for the tube's top plug to make it stiff enough to hold without flexing (which would let it pop out the top).
It will add a little weight but I don't think that's an issue with the pressure you're using ...
Yogi

[cdavenport]

Building on Yogi's excellent idea I would like to offer the following information based on tests my students and I completed in the classroom several years ago.

A standard 2 litre soda bottle will withstand an internal pressure that exceeds 90 lbs before bursting.

Boeing was one of the first commercial enterprises to experiment with and develop the concept of a pressure dome.

Using Yogi's description and the aforementioned information, try this as an experiment:

The black section is the rocket's pressure tube. The red is YOgi's bearing surface and the red section is a carefully cut piece of 1 or 2 litre soda bottle glued in place with a suitable adhesive. I like "Goop;" it adheres anything to anything else! Marvelous stuff and it will take the pressure without leaking. You may even double the pressure dome with a thin layer of Goop to laminate the two together.

It will be very light and incredibly strong!

[mbauer]

Thanks for the input, what I did was go back to the old method of using the top former as a stop plug. The PSI Tube was glued to the top former, but I used a second bulkhead 2" underneath to center the PSI tube. Wrapped the top with a 3" wide outer skin after using cardstock straps to hold the plug in place!

Hopefully this will be the fix. The old way of doing it was working until I started having issues and then tearing everything apart to do repairs. The blow-outs didn't happen until I changed and or damaged the old way of doing things.

Both sound like great ideas, but yesterday afternoon was when I fixed it.

Next weekend is not going to be a chance for flight testing, maybe the following weekend as well. Going in for another hernia operation this Friday.

If weather permits, I'll try a launch before work sometime this week. The rocket is ready to go again....

Mike

[calinous]

This really turns into rocket science I can't wait to hear about the successful launch (but even those unsuccessful launches are great to hear about)

[mbauer]

Originally Posted by calinous

This really turns into rocket science I can't wait to hear about the successful launch (but even those unsuccessful launches are great to hear about)

Thanks for your comments! For sure agree with you about the unsuccessful ones:

Lots of great ideas have been volunteered, have a list of things to check out. For future projects / issues.

Plus, I've had a great learning experience finding out what won't work!

Just wish white glue dried faster....

Mike

[calinous]

Have you tried a hair dryer? I think heat makes it set faster (or at least on the bottle of one kind of premium carpentry glue it was suggested it sets faster at higher temperatures)

[mbauer]

Don't have a hair dryer, but might try to find one.

Great idea, should have thought of it, but no hair on the top of my head means there isn't one stashed in the closet...

Mike

[cdavenport]

You could also use two-part epoxy with little or no weight penalty compared to Elmer's.

[mbauer]

Does epoxy work with paper?

Used to use superglue only, but it cost to much with big models and my eyes sting while working with it.

Emailed Orlik about the types of glue he carries, still looking for the Wiccoll Karton glue-it was like PVA super glue!

Mike

[cdavenport]

Epoxy works like a champ and there are several different types that will work. You can use JB Weld, which is an epoxy putty and a bit heavier than you might want. But, it has a much higher burst limit than Elmer's could ever dream of.

Then, there is the pourable type, two-part of course, that is a high viscosity liquid available in a range of curing times from 5 minutes to 1 hour. At the hardware store, it will come as either two separate tubes or one 2-part tube. Either way, it's usually of the 5 minute variety.

It's quite strong and more than suitable to your need. In contrast to JB Weld, the pourable epoxy will saturate your paper making it very strong indeed.