Plywood/epoxy wheelhouse project- advice needed

[FirstLady]

Hi all, I am in the process of constrcting a ply/epoxy coated wheelhouse for my 24' cruiser. The fabrication is nearing completion & I would like some advice on final finish. My prefered finsih would be gelcoat (flowcoat) to match the rest of the boat but am aware of issues with adhesion/curing issues with epoxy and polyester gelcoat. My prime concern is to achieve a long lasting finish similar to the rest of the boat that will not require regular stripping/re-finishing.

Has anyone got any good alternative suggestions? What type of paint performs well? The project is being built under cover in a heated space, so curing issues etc not a problem. The only facility I dont have is a spray booth.

Any useful tips/previous experience would be very welcome please.

 

[beneteau_305_553]

I made a sprayhood of plywood and coated inside and out with one layer of 1 1/2 oz grp . I then coated it with bodyfiller and sanded it down then painted it with 2 coats of 2 part polyurethane paint with a foam roller.

The end result is fine but it took hours.

You can probably apply the paint directly to the wood to save a lot of time but I needed the strength as I used 3 mm thick ply.

 

[gtuson]

Generally not recommended to use polyester glass fibre on ply. It does not bond well. better to use 2 pack epoxy and glass fibre. We did wheelhouse roof this way and absolutely no problems....10 years old now. Don't necessarily need glass as well as epoxy unless surface going to be walked on or abraided in some other way. Can get gelcoat like finish by using extra coats o epoxy perhaps with some thickening....see West System info...

 

[Quandary]

Addition to above. epoxy is much better than polyester for sheathing and it can be thickened to filler consistency using a variety of fillers, micro balloons are easiest to fair. Epoxy does require a reasonable ambient temp. to cure and you may have to deal with amine blush. Used neat it may run or curtain on vertical surfaces and will be very smooth (but not always flat) requiring abrading between coats unless applied early in the cure.
Note that you should use only powder bound mat for epoxy resin. Techniques are well described in West or Epiglass brochures etc.

 

[oldsaltoz]

G'day Brian and Jenny,

To improve epoxy resin penetration into ply, just add up to 33% Methylated Spirits to the mixed resin and hardener, The edges will take a lot of sealing due to the exposed end gain in the ply layers. Also important to treat any holes the same way.

It's ok to apply epoxy over poly resin, but not a good practice to apply poly over an epoxy. Also note that poly resin will not stick long term to timber like epoxy will.

Micro-Fibres mixed with epoxy resin to a peanut butter consistency makes a very strong epoxy glue for timber joints, also great for filling holes of thru' deck fittings, just drill oversize, fill and let cure, then re drill correct size hole, no chance of water getting into the ply or being able to crush the ply when tightening thru' bolts. Just make sure you remove any excess because this stuff is a pig to sand.

Using a poly based flow coat over an epoxy has the potential to fail down the track: It might be possible to apply a high build epoxy primer and then a poly flow coat. Also note there are epoxy flow coats available in a the full range of colours using pigment.

Getting Flow Coat to like like Gel Coat is almost possible, but you need to start with well prepared surface and apply several thin coats and lots of sanding between coats.

Given the choice I would consider a thin layer of closed cell micro balloons to get that perfectly smooth and flat surface, then apply a long chain polymer Polyurethane paint. it will last for years and look fantastic.

Hope this helps.

Avagoodweekend......

 

[Tranona]

Use peel ply on the final coat of epoxy which will give it a good final surface that can be filled if necessary with epoxy filler and rubbed down to a good finish - with effort at least as good as a GRP gel coat then paint with a 2 pack polyurethane if you are confident of a single pack such as Toplac. On small areas such as framing round wheelhouse windows that would be easier to get a good finish. Good information available from Wessex Resins on using epoxy.

 

[MidiMagic]

Having carried out a similar project on our boat in France, I found painting the timber didn't last any where near as long as I had hoped, even using the best primers and undercoats available and a 2 part expoxy finish.
You'll find that even though there is a lot of initial work involved, covering the wooden structure with fine gauge fibre glass matting and then using body filller will give a much longer lasting finish.