HI jd
Provided you seal the finished hull the glue used to hold the planking to the frames is a matter of choice. Cyano is quick but can become brittle, epoxy is a bit slower but more resiliant, white glue makes strong joints in wood but takes time to set. Aliphatic resin is waterproof, makes for a strong joint but takes time to harden. However unless you use marine grade ply the wood will not be waterproof and even then will need protecting with paint. 😀
A workable solution is to coat the inside with polyester layup resin, possibly strengthened with some glass cloth. The outside of the hull can be sealed with two part laminate epoxy resin. This can be brushed onto the hull and being clear will allow what's underneath to show through. The finish will be like glass 😎 but can be matted down with fine wire wool. if you require a stronger hull glass cloth can be laminated with the epoxy. You can add tints to the epoxy resin to save painting the hull.
Resin suppliers can usually be sourced locally as carriage costs can be high - the post office will not ship some of the hardeners so commercial carriers have to be used. 😑
Good luck with the build. Perhaps you will post details as a Blog! 😀
Dave

I made the mistake of using a non-waterproof PVA on a planked hull when I came back to modelling aftera long gap- disaster! I thought a good paint job would do the trick but was wrong. I still get seams opening on that model so I suggest you go for a guaranteed waterproof glue. Of course a couple of coats of epoxy in and out will pretty much seal everything. I sometimes want to leave plank lines showing so I don't use epoxy on the outside. My Silver Mist was like this and I have problems with wood moving about- still don't know the answer! Perhaps someone else will. Good luck.
Ian

Thanks Ianed57. I have built models before but never RC and put them in water. Going to give it a go this time with a scale model I operate at work. I am also looking for 2 outboard motors to push it. Thanks for your help. Jd

I have always found aliphatic resin good- it is waterproof and has a quick grab time. it also sands well.
I know some people speed up building time by using only cyano glues but this seems very expensive to me.
As for a sealant, I find ZPoxy to be brilliant- it goes on nicely with the help of a bit of heat from a heat gun and again sands well. This is just what has worked for me.