Conformal Coating Recommendations

[Thistle17]

We have a thread on MSW related to building a Mark I River Patrol boat in 1:6 scale. In spite of the fact that it is a waterline model it has large surface areas that needs to be coatedand faired prior to painting. The model will be placed in a museum display for the public so a convincing quality finish is desired. The substrate of the hull is basswood. It has been skim coated in the seam areas with Rage, Easy Sand and further patched with Nitrostan body filler. We have tried Golden Edge but it as well as the Rage have little open time to spread and work the 2 part compound. As a matter of fact Golden Edge is so hard to sand once cured it would be impossible on this very large model. It is nearly 5 feet long.

 

I/we are reluctant to use dry wall compound as we are not comfortable with its long term stability over the wood base. Using fiberglass cloth and resin is an obvious choice but the VOCs generated are not safe in the environment we are working. We are open to suggestions and even willing to experiemnt with suggested methods. So if anyone(s) out there have ideas please repl.

Joe

[kurtvd19]

Fiberglas used with epoxy resin will give a glass smooth surface.  Hardly any odor.  West System 105 epoxy resin and 206 hardener will work perfectly.  Check https://www.westsystem.com/

It's very versatile and their instructions are great - the website has a lot of tips.  Used for full size boats but works for models too.  They have some other combinations if you need extended work times.

 

I have used this and can recommend it.  A bit expensive but their pumps for the resin and hardener do the measuring - 1 pump of each = the correct mixture - not a 1:1 mix but the pumps are calibrated to deliver the right amount to the mix.  The containers are much different in size for the resin vs hardener.  Good shelf life too.

[Bob Cleek]

33 minutes ago, kurtvd19 said:

Fiberglas used with epoxy resin will give a glass smooth surface.  Hardly any odor.  West System 105 epoxy resin and 206 hardener will work perfectly.  Check https://www.westsystem.com/

WEST System has an extensive manual online. It contains all you need to know about their products. Be aware that epoxy is a material that demands close attention to the manufacturer's instructions for use, though. This is particularly so with measurements of resin and hardeners and application temperatures. Use in a well-ventilated area if indoors. Run fans to keep air circulating from inside to outside. Don't make yourself crazy about hazmat issues. Just follow the instructions. Wear nitrile gloves. Some folks are sensitive to contact with uncured resin and hardeners. Continued exposure can exacerbate sensitivity. 

 

WEST makes a selection of additives to control the properties of the resin mix. One you will find very useful is their sanding additive (essentially microballoons.) This will make a cured epoxy coat sand like butter for a perfectly smooth surface. (Don't let some dork talk you into using sawdust to save a few bucks!) 

 

If at all possible, I'd advise you find a professional boatbuilder or auto body and fender guy to do it for you. There is a learning curve and being in the middle of a glass layup isn't' the place to discover the curve is getting ahead of you! 

[Thistle17]

Thanks guys. I have helped lay up a cedar strip canoe with the fiberglass resin approach. Even with an experienced leader it was messy but indeed the finish was beautiful. I was afaird that would be the response/solution. I certainly will take it outside to follow this regime if we march down this avenue. Can you tell I am reluctant to go this route?

 

I do know they make a fine mesh fiberglass expressly for models and I will likely use that material. We do have a limited group budget for this project so the next step is to check out West System product costs.

 

Joe

[Bob Cleek]

If the model is going to remain indoors and is plywood, you don't have to use a strand matrix for strength at all. No need for fiberglass cloth. WEST System epoxy, thickened with sanding filler, can simply be trowelled on the surface and then sanded fair, much like auto body filler. In that instance, it is used like drywall "mud," but it cures to an epoxy, rather than a plaster.

[kurtvd19]

I agree that fiberglas cloth isn't needed for a museum model.  What you are looking for is a smooth surface not strength.

[Thistle17]

And thanks again for the update. Looking into this appraoch as I write this.

Joe

[Roger Pellett]

I’d like to weigh in on this topic.   I’ve used a lot of West Sysrem Epoxy with excellent results.  When mixed properly, it cures 100% of the time.

 

I would like to emphasize Bob and Kurt’s comments above.  It needs to be mixed in the specified proportions.   In the case if the resin/hardener combination that I am using it’s 5 parts of resin to 1 part of hardener.  If in a group project, some eager beaver decides to add more hardener to “speed things up” it won’t cure - personal experience with another participant restoring Sailing Association Lasers.

 

Use of the calibrated pumps mentioned above is the easiest way to dispense in the correct ratio.  These are sold in pairs specific to the resin hardener combination that you are using.  Just make sure that you dispense a squirt of hardener for each squirt of resin.

 

West system  also sells a small batch kit that includes a digital scale that allows you to compensate for the weight of the container.  Once that you have done that, you dispense hardener, miltiply the resulting weight by six and add resin until you reach the correct total weight.  There are probably digital scales on the market that would allow you to do the same thing.

 

West System also sells a range of thickeners to add to the mix as fairing compounds. You will probably want to add one of these.  The unthickened resin will  probably be too thin for your needs.

 

Roger

[wefalck]

I believe there are also filled acrylic resins for such purposes, but have no practical experience with them or know of any sources in the USA - just in case you are concerned about the epoxy fumes.

 

Both, acrylic and epoxy, resins can be filled with 'micro-balloons', which are microscopic hollow glass spheres. They can be bought in small bags.