Liquid Nail

Well, its a construction adhesive so its probably water resistant at best. It's not like it will instantly dissolve when water touches it, but its probably not the best solution as far as long term durability goes in wet environments. As for the strength of it, the adhesive itself is very strong, but it all depends how well it bonds to the relatively non porous surface of the PVC pipe. It will stick to the wood no problem, that's what it is made for after all, but  just from my personal experience working with plastics and adhesive I feel the best bonds for plastic come from a glue that provides some kind of exothermic chemical reaction such as an epoxy. So all in all, the glue may work for a while, it may work forever, it may not work at all. My guess is that the glue will hold the rail to the wood, but once you start using skis on it, and you dig in a little, that the sudden force will break it free.

So take it for what its worth, this is all just my opinion.

i think your glue (or liquid nail, whatever you call it) will hold up excellent, except i'm affraid you'll rip^off the first layer of wood, real nails or screws go deep into the wood and will spread the force evenly while here all the force comes down to let's say the first mm of wood...

if youre thinking of using liquid nail as opposed to screws, id go with screws, even drilling straight in through the pvc you dont feel the holes when youre sliding it. i wouldnt worry about catching or something like that

or drill them in on an angle

yeah that can be kinda hard though and if you arent comfortable doing that then drilling through the top is a perfectly good option. it's pretty much impossible to catch an edge, which is the reason many people go to the trouble to drill through the side. in addition, drilling straight down holds the rail in sooo much better

i tried it on some pvc pipe. got about 2mos out of the rail and the pipes came right off. also, when they come off, the glue is still stuck to the wood and is hard to get off. what i do now is bolt the pipes on and that works better cause you can remove them and put new or different pipes on so it gives you some variety of the rail. also, bolting is less strenuos, easier, more reliable, more durable. also if youre building a new rail and you want to use the same wood, then you can but if you use liquid nail then that wood is unreusable and unrecylable. liquid nail is unreliable, not durable, and a waste of time. it is easier to bolt the pipes down and it takes less work and time. bottom line: bolt the pipes down

^that was just my experience with it. i also forgot to mention that it is hard to bolt or screw down the pipes if the pipes have a small diameter. that is why i tried liquid nail in the first place

i actually found it best to screw the pvc from the bottom. apply pressure to the top of the rail and don't use screws that are long enough to go through the top. pretty straight forward

I actually did this for my summer setup and it worked really well what i did was put liquid nail all the way down the length of pvc then stuck the two strips of pvc to a board underneath. then to make sure the pvc was secure i put screws up through the bottom at the ends and 1 in the middle. this was just as a back up. However the liquid nail worked extremely well and made it so the pvc didn't move at all. plus its cheap and easy to use.

liquid nails is really strong shit. To improve the adhesion though you could take some really rough sandpaper and scuff the shit out of the underside of the pvc pipe.