If you have made a ‘faux’ pack raft (as here and here) as I have you will have had the same problem with the paddle. The cheap (Intex) rafts come with a set of oars which need to be converted into a double bladed paddle (which will fit in a canoe drum!)
I tried several expedients. The problem I encountered was with the strange ‘Chinese’ threads which the paddles come with. My bolt shop could not match it so I could not buy a die or a piece of continuous thread to match so I could join them up. The first one I cut a thread with a triangular file so that I could use one of the joiners (1 spare) the paddles come with. This worked, but not very well. It was prone to locking up so that it was difficult to get it back apart for stowing in the drum. I leave these rafts up the bush in various locations (eg so that I can cross a river to a camping/hunting spot, or so I can get out quickly in an emergency (by boating downriver), or so I can carry out meat easily.
If you join three lengths together you get a double paddle which is 6’9″ or 2.09 metres long – just about right. Four is too long. My latest expedient involves two cheap plumbing fittings bought from Bunnings for a few dollars glued into the section ends with some epoxy. I believe this is the best solution.
If you are going to use the faux pack raft (with nappy!) for serious white water, I suggest you buy some serious paddles such as these, but for a cheap expedient this ‘hack’ works well.
PS: The two fittings are https://www.bunnings.com.au/holman-15mm-pvc-male-take-off-adaptor_p3142724 A$2.98 and https://www.bunnings.com.au/holman-15mm-pvc-male-take-off-adaptor_p3142724 A$2.84 Sept 2019. Total A$5.82 -plus glue!
The lengths slip together quite neatly.
The completed paddle:
6’9″ or 2.09 metres long
I decided to reinforce the join by using the spare barrel union which came with the paddle. Accordingly I ground off half its internal thread with the Dremmel
Then the barrel union fitted over the plastic joiner
And the whole assembly did up nice and tight, as shown:
Here is a trip you might enjoy: