Duratec line vs Automotive primers and topcoats

Hi All

I am building my first ever plug. We are finalizing the strip planking phase and will be shortly moving into the fairing, sanding, primer phase.

The male plug consists of a 15mm MDF jig, stationed every 500mm. The planking is made out of 6mm MDF.

We have done some test fairing with an Automotive type body filler by called Jetbond D2A146 by Sherwin Williams. Its is polyester based filler.

I am debating if I should use Duratec EZ Sand Primer 707-061 and Black Polyester Hi Gloss Topcoat 902-45 or if I should use automotive primer and 2 part monocoat polyurethane topcoat paint.

I am located in Panama and can get good automotive products like Sikkens (Akzo Nobel), PPG or Axalta. I cannot get any Duratec products here. I can import Duratec from USA but must pay HAz-Mat fees which is a problem.

Duratec seems to be highly regarded in the pattern/mold making industry. Is it really that much better than automotive finishes? Am i missing something? Can't seem to see how any topcoat could be any glossier than an automotive finish.




Thanks,

 

Duratec has two advantages in the marine industry.
First, it is KNOWN to NOT have any issues with other marine products.
Second, it is sold by the same suppliers as the resins, fabrics and other specialty products used in boat building.

Automotive products MAYBE fine or MAYBE have issues with marine resins.
Automotive suppliers MAYBE not want to sell to people not in their rolodex.

If you choose automotive; then do lots of testing to ensure compatibility before total commitment .

 

As mentioned, it's a bit of a gamble to use automotive products, some work some of the time, and others don't work at all.

 

Thank you for your reply. Sourcing automotive paints and primers is not a problem here.

Considering it is my first time, I may stick to the good stuff just to mitigate sources of potential problems.

 

Thanks, I don´t like to gamble!

 

You can't be the only man there building molds. Just ask the others what they use, I am sure they have identified a suitable product by now. Don't limit yourself to boatbuilders, car tuning guys also do it.
Your resin supplier is also likely to have advice and usually even the right products for sale.
Lastly there's no need to gamble, you can always do test panels and see for yourself how filler and topcoat react to the mold gelcoat and resin.

 

About 90% of the FRP boatbuilders are making panga boats that are all splashed molds. They use the cheapest products around.

The major fiberglass and resin dealer has been no help. No data sheets on any prodcut they sell. Most of it comes from China or Colombia. They have no idea what 1708 cloth is. They work everything in some metric "equivalents". No peel ply for sale. No quality fairing compound. There is no vinil esther resin. Limited gelcoat colors. Its rough man.

Trust me I have tried get local advise.

I am trying to raise the bar so I ask here and will import stuff if I have to.

Thank you for your reply.

 

Your situation is far from unique.Asking suppliers will inevitably get an answer related to the products they supply,they are hardly likely to recommend another company's products.If you can get hold of a small sample of the finish you are considering you can do some testing to determine the outcome.Whatever you do don't try such tests on something big and important but create a small part with some areas that have the features you are incorporating in your plug.In a few days you will have an answer.An alternative might be to use a coat of PVA as insurance,but again do a test and don't be shocked if the mould surface needs a bit of compounding.Record exactly what you do and store the information as you build up a library of answers to technical questions.

 

If the dealer doesn't have the data sheet, ask the manufacturers. The barrel must have some form of ID on it telling you what it is and who made it.

Fabrics are made in imperial and metric versions. 1708 is a so called "combination fabric" and it's metric equivalent would be 576+228 g/sqm, usually the metric version is available in 600+300g/sqm. If you can't find it already stiched together you just buy the individual fabrics and layer them. Actual 1708 is not common in metric countries.

Regarding the automotive products, the topcoat must be imprevious to styrene. The way to test this is simple, spray some topcoat on something and let it dry, put a styrene soaked rag on it for about half an hour. If it still looks good you can proceed to the next test, take a piece of mdf around 1/2sqm, apply the same combination of fillers and topcoat as you used on the plug, wax, continue with the material sequence you will use on the mold. Demold and look at the result.
Just to make topcoat selection easier, you need a polyurethane one, the 2k versions are usually appropriate.

 

Correct, they have bi-axials, pre-stitched together in 600/225 g/m2. Its just that its like pulling teeth to get the info. So they will call that cloth 825 biaxial. Anyways, I have my layup schedule sorted out and get it supplied here in metric version no problem.

This is really helpful. Yes, for topcoat I was considering a 2 part polyurethane paint. Thanks!

 

Keep in mind that 2 part automotive paint is normally baked in an oven.If you don't bake it,and it may cause shrinkage in wooden parts if you do,allow a bit more time for the curing process before beginning the mould.With a large plug this time would be taken up by the flattening and finishing part of the job as well as attaching flanges.In the past I have found PPG Deltron primer quite effective but there may be better or less expensive alternatives in your region.

 

Ok, so after quoting the K38 Deltron primer and Concept topcoat both by PPG the Duratec is looking more attractive cost wise.

I am thinking of using the following:

- Duratec EZ Sand Primer 707-061 @ 45 mils
- Duratec Black Polyester Hi Gloss Topcoat 902-45 @ 25 mils

What do you think about the thickness?

 

I have difficulty visualising "mils" because to my European sensibilities it is an abbreviation of millimetres.In reality all you need is an adequate and impermeable surface that can be sealed with release wax.

 

The actual thickness is almost irrelevant. You need to apply enough primer to fill all the surface defects and be able to sand the surface smooth and not sand through, that could he 5 mils or 50 mils. It all depends on the surface profile of the substrate.

It's the same with the top coat, as long as when you're done sanding and polishing you have about 10+ mils it will be fine.