Clingwrap could it make a waterproof boat?

[thewharfonline]

hey all Paddle Ducks!

I was just thinking (which is something I often do) if I made a newspaper hull such as the one made by mtj06 could I instead of using a waterproof glue could I use an outer layer of clingwrap glued to the hull to make a waterproof layer.

It's probably best that i try it myself but i was wondering if anyone tried it! It's just I have large amounts of PVA and its not the best waterproof material but if I could use the clingwrap it would be different!

So give me your ideas if you have any, help appreciated!

[mjt60a]

In theory that should work but I can forsee one or two problems....
1. Glueing it to the hull - I use the stuff during building to prevent removable items which I construct 'in situ' to assure a good fit, from adhering to the rest of the structure. I've used it with PVA, exterior wood adhesive, balsa cement and even araldite (or other two-part epoxy) and I've found it NEVER sticks to the glue!
2. Getting a smooth finish - it would have to be covered in one piece (as you can't glue the stuff together) and can only be stretched so far so you're sure to get creases on any convex areas such as at the stern and where more than two flat surfaces meet (at the bow)  
3. It's easily damaged - the slightest scratch will allow water to enter and quickly spread between the paper hull and the cling-film.

You could try it anyway, I tried a few things to see how they'd cope with water (contact adhesive might work, I haven't tried that) but I think you'd be better using something else instead. Resin (for fibreglass is probably best (a layer of fibreglass tissue stuck to the hull with resin first would be even better) but this project was all about using whatever is available and it will work with cellulose dope (for model aircraft - that's what I used on mine) thinned about 50% with cellulose thinners and give it about 3 coats. Or sanding sealer, I tried that and it only failed because I didn't seal part of the hull properly. I suspect that ordinary woodwork varnish would do it too if you use enough, or maybe even just primer with paint over it (primer itself isn't waterproof). Whatever you use, painting the hull several times over the top will help keep the water out. I just used for a finishing coat, some 'white exterior gloss' left over from painting the shed and it's perfectly OK

[steamboatmodel]

I have seen one model which uses the covering the airplane guys use heat sealed over a light balsa frame. this was very light and in a free running small gas powered boat. this ran great until it ran into something, at which time it self destructed.
Regards,
Gerald

[Walter Snowdon]

Let me tell you a story....... a few years ago I used to teach model boat building to the kids in our club as a winter project. So, I designed a simple hard chine balsa hull whch they all built and fitted out with materiels donated by club members to keep pocket money costs down. The idea was they would build a common hull and design and build their own superstructures. Now, the root of the story- the finish. I hit on the idea of mixing white waterproof PVA with acrylic paint (50-50) and a small amount of water  and painting the bare wood with it to act as a pre-coloured sealer. The results were amazing!. It dried with no colour fade and with a hard smooth skin which required no rubbing down and instead of being a filler, it became the final coat. Somehow theacylic had fully proofed the pva to a hard resistant surface. Six very different models were completed and sailed with no softening, but to be sure, THE HULL ONLY then got a thin spray of acrylic varnish. One of them, (a fast lifeboat) built by an eleven year old girl sailed for three seasons without any decay of the finish. Give it a try on a small model and let me know the results.   Walter.

[PJ]

Very interesting idea, Walter.  I have seen R/C model hulls sheathed in cut up bedsheets soaked in PVA and the "skin" is entirely waterproof and  rigid depending on the hull material used.  We tried this over blue foam but it wasn't rigid enough, although when used with fibreglass resin it was very strong.  Using the PVA/bedsheets over a stable wooden hull does provide a tough waterproof finish.

What was the mix ratio of your PVA/acrylic combo?  Was it sandable and able to be brought to a decent finish?

Regards

PJ
Victoria, BC Canada