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[npomeroy]

I intend to use epoxy on all the inside hull surfaces as a water protectant, after all the parts are glued. But on the exterior and deck to be painted, I am tossing up between automotive primer (lacquer type) which I usually use on aircraft, and with multiple coats, sanded after each one, provides an excellent grain filler and seems pretty waterproof. Alternatively I could use epoxy (also with sanding between coats). But I feel the epoxy would not sand as well, and being clear makes it harder to assess the surface perfection.  On top of automotive primer I would probably colour with automotive type "acrylic lacquer" from spray cans. Over an an epoxy base I would expect to apply automotive primer and then either "acrylic" or enamel.  It is for this model https://www.modelboatmayhem.co.uk/forum/index.php/topic,69311.msg752069.html#msg752069


Cheers
Nelson

 

[JimG]

I always use epoxy for finishing ply and it gives a really good surface. You do need the proper finishing epoxy not the laminating type. I also add some microballons to the epoxy, just enough to thicken it slightly but nowhere near a paste. This helps to fill the grain of the ply and often one coat of epoxy is enough to get a good finish. The microballoons also makes it easier to sand without taking away the strength and hardness of the epoxy. You really need to use wet and dry sanpaper used wet for the epoxy to get a good finish as it tends to clog up normal paper. If you are concerned about the epoxy being clear and colourless than you can get colours you can add to the epoxy, I have never needed to use these so don't have any experience with them. When sanding it is best to allow plenty of time for the epoxy to harden. at least around 12 hours.
Jim

[npomeroy]

I always use epoxy for finishing ply and it gives a really good surface. You do need the proper finishing epoxy not the laminating type. I also add some microballons to the epoxy, just enough to thicken it slightly but nowhere near a paste. This helps to fill the grain of the ply and often one coat of epoxy is enough to get a good finish. The microballoons also makes it easier to sand without taking away the strength and hardness of the epoxy. You really need to use wet and dry sanpaper used wet for the epoxy to get a good finish as it tends to clog up normal paper. If you are concerned about the epoxy being clear and colourless than you can get colours you can add to the epoxy, I have never needed to use these so don't have any experience with them. When sanding it is best to allow plenty of time for the epoxy to harden. at least around 12 hours.
Jim

Hi Jim.  I already have epoxy - this type https://www.mitre10.co.nz/shop/norski-epoxy-resin-312ml-amber/p/370978 which probably is the laminating type. Is this less sandable?

[Stavros!]

i have always used automotive laquer to seal all types of wood and never had a problem i always use 400 grit paper or DA sanding discs to rub it down then primer over it i always if using aerosols put on what i call a sacrificial gloss coat 2 coats before a final rub down with 400 grit used dry then overcoat the final colour coats to finish.....if i use  a proper 2 pack paint i  give 3 full coats of primer followed by top coats to finish .




Stav

[JimG]

Hi Jim.  I already have epoxy - this type https://www.mitre10.co.nz/shop/norski-epoxy-resin-312ml-amber/p/370978 which probably is the laminating type. Is this less sandable?

My understanding is that laminating resin tends to remain sticky on the surface initially to help bond on the next layer. It may take a lot longer to fully harden on the surface ready for final sanding. Finishing resin is designed for finishing the surface and hardens to a hard surface. It is also used in aircraft when covering with light glass cloth on balsa or ply surfaces, generally two coat are needed here to fully cover the weave of the cloth.
Both types of resin when fully hardened will sand as well whwen sanded wet, the laminating resin may need to be left longer to fully harden.
Jim

[John W E]

hi there


Another topic which is open to many answers and basically the correct way is YOUR WAY OF DOING STUFF and YOUR materials.


As you can see you may have a variety of answers, however, in this case you have to take a couple of things into consideration.  First of all, the plywood which the model is made from (the framework and so forth) what type of plywood is it?   As good quality birch ply is pretty water resistant and may just take a couple of coats of paint to make it fully waterproof.     If you are using a soft aircraft type of ply (such as lite ply) which is like a balsa infill and absorbs water rapidly; you have to use something in the form of an epoxy resin, or, a coating which is really 100% water repellant.


On the market, there are several makes of epoxy resins.   I personally tend to stick to Zpoxy finishing resin without anything added such as a thickener etc.  and apply 2 - 3 coats of this on the hull and this resin remains clear when it has hardened.   There are also resins from Deluxe which are made for the modeller and are basically water based - these are quite easy to work with.


Here is a pic of the Bluebird which I built a couple of years ago which is made from liteply and this will give you some indication of the finish which is achievable.   Bluebird has 3 - 4 coatings internally of the Deluxe resin and 3 coats of Zpoxy on the exterior.


John