Water Rocket Forum

In order to create larger Water Rockets with larger volume pressure chambers than afforded by typical soft drink bottles, many enthusiasts have resorted to joining multiple bottles together using various methods which all are commonly referred to as "splicing". U.S. Water Rockets has developed a radical new splicing method which you can use to create perfect splices that are easier to build and outperform traditional splices in strength, weight, and appearance. The new technique is known as the U.S. Water Rockets Slip Joint Bottle Splice.

The tutorial can be found at:

http://www.uswaterrockets.com/construct ... torial.htm

I must have done it wrong. My minimal glue joint failed. I used a Dr. Pepper bottle from the neck to the end of the straight sided segment, inside a standard straight side bottle. The Dr Pepper bottle is a bit narrower so it fits without shrinking.

Trying again this weekend.

By the way...

WD-40 does a GREAT job of removing uncured PLP from your hands.

Bugwubber

Great Tutorial for the new splice. But where I live the glue tends to get a little porous when curing. Would this be a problem?

bugwubber wrote:I must have done it wrong. My minimal glue joint failed. I used a Dr. Pepper bottle from the neck to the end of the straight sided segment, inside a standard straight side bottle. The Dr Pepper bottle is a bit narrower so it fits without shrinking.

Trying again this weekend.

By the way...

WD-40 does a GREAT job of removing uncured PLP from your hands.

Bugwubber

At what pressure did it fail at? How long did you let it cure before pressure testing?

Reptiglorandrockets wrote:Great Tutorial for the new splice. But where I live the glue tends to get a little porous when curing. Would this be a problem?

It sounds like you could have a few issues:

1) The joint is not snug enough, leaving too much gap between the bottle overlap area and causing a lot of glue to accumulate in the space, which weakens the joint and can lead to glue foaming.

2) The bottles were not dried enough prior to glue. If you rinse off the sanded area after roughing up the overlap then water will accumulate in the grooves and if you do not allow enough drying time it will be in the joint when you glue it.

For the most part, the bubbles in the glue will not be too big of a problem because each bubble has a wall of glue surrounding it, so the joint will be air tight. Over time or at high pressures the bubble walls may fracture and lead to leaks as a path for the air forms through consecutive bubbles.

You can enhance the strength of the joints if you find these problems are affecting your joint strength by simply making the overlap area a bit longer. There is nothing wrong with a bit more overlap if you need it. the less overlap you use, the more precise you have to make your joints, so if you are not concerned with the absolute lightest rocket, you can make a larger overlap and not have to work as meticulously to make them perfect.

Hi guys,
About a week ago I made 6 splices and pressure tested them to 165PSI before the bottle failed. So I quickly assembled a small rocket and flight tested them. They worked great dispite a small leak in the upper splice. Great idea for the improved splices USWR. Visit Reptiglorandrockets on youtube to see the flights.

Reptiglorandrockets wrote:Hi guys,
About a week ago I made 6 splices and pressure tested them to 165PSI before the bottle failed. So I quickly assembled a small rocket and flight tested them. They worked great dispite a small leak in the upper splice. Great idea for the improved splices USWR. Visit Reptiglorandrockets on youtube to see the flights.

Glad you were able to get such good results from your first go at it. Remember, if you want to add some insurance to your slip joint splices, all you have to do is make the overlapping part a little longer. We use 1/2" or 3/4" to keep the weight lower, but there is nothing preventing you from shrinking a longer overlap of 1" or 1.5". It will be slightly less space efficient, but the larger contact area will mean that you do not have to be as precise to get the same strength.

The slip joint video includes a wrap of duct tape around the splice. Does the tape help resist the expansion of the bottle diameter or the shear force trying to lengthen the splice axially? Just wondering if I use fiber-reinforced tape (which is quite narrow compared to duct tape) if it should overlap the seam or just be on the outer bottle. My second attempt at a splice is curing for a couple more days. The first attempt failed the pressure test after a couple minutes at 110 psi, but I had forgot to use any tape over the splice. There were a couple of very small drops of water leaking through the joint before it went boom. For the second attempt I have made the overlap a little tighter and longer.

The tape resists the expansion of the bottles, which makes for a peeling force on the joint. If you play with PL Premium and strips of bottle plastic, you can see that it's very easy to peel a lap joint apart, but very hard to pull it apart laterally. So the fiber tape would be fine over the area of overlap.

There may be some benefit to the tape overlapping both bottles, but we believe the man advantage is in resisting the peeling. as the bottles swell up at different rates.

I appreciated the idea of using the rod thru the bottle openings to keep the splice straight. Simple, effective, and I wish I had thought of it myself.