This blog covers the day to day progress of water rocket development by the Air Command Water Rockets team. It is also a facility for people to provide feedback and ask questions.

Thursday, October 29, 2009

Splice test #3 - Sikaflex - Success

We did a successful burst test on the Sikaflex asymmetric splice with a PL attached sleeve. (splice #5) The bottle ends were also reinforced with a jacket made from another PET bottle and held down with glass strapping tape. We learned a couple of things from this test:

The Sikaflex works great as a sealant and the width of the sleeve was more than sufficient to hold the splice together.

The final burst pressure was 190 psi! This is a better result than was expected. The actual failure was due to the strapping tape breaking, weakening the bottle reinforcing and then ultimately bursting the bottle. The sleeve still held though. The normal burst pressure of these bottles is about 165 psi.

This is a photo of the splice under test. The needle on top of the bottle was added to see how much bottle distorts close to the sleeve.

I'll make up three of these splices next and see how reproduceable the results are. I won't be testing them to destruction but pushing them to 140 psi, for an operational pressure of 130psi in actual rockets. If the results can be replicated, it would give us a nice safety margin.

I do have good slow motion video of the bottle's distortion and ultimate burst. I'll post the video with the next main website update, as I am busy the next couple of nights getting ready for this weekend's launch event.


Tom Stanton said...

Hi George
That seems to be a simpler idea for splicing and can still hold a lot of pressure!
Good luck this weekend!

George Katz said...

Hi Tom,

The splice is actually a little more work because it is now a 2-stage glue process, but not too complicated. I am happy with how well it sealed though, something that has been an on-going issue with our splices. Having it hold at higher pressures is also encouraging.

Daniel Veira said...

Hi George,

Could this joint work using only identical bottles?

George Katz said...

Hi Daniel,

Yes this spliced-pair is all made from identical bottles. Even the sleeve is made from the same bottle type.

If further tests are good, I'll put together a step by step procedure for this kind of splice.