Monday, April 29, 2013

T2 Build-Series #12

Sealing the wood with epoxy resin!

KEP's T2 .21 Presentation
KEP's T2 .21 Freebie
KEP's T2 .21 Build Series #1
KEP's T2 .21 Build Series #2
KEP's T2 .21 Build Series #3
KEP's T2 .21 "Inspirational" Article
KEP's T2 .21 Build Series #4
KEP's T2 .21 Build Series #5
KEP's T2 .21 Build Series #6
KEP's T2 .21 Build Series #7
KEP's T2 .21 Build Series #8
KEP's T2 .21 Build Series #9
KEP's T2 .21 Build Series #10
KEP's T2 .21 Build Series #11

Now it's time to do the final preparations to start preparing for paint... What you should do first is sand everything the way you want it to be. Be careful and sand smooth and straight, pay attention to the corners etc. There are a few places where you should keep the edges on the "sharp" side. That is the ski and the separate running pads for the front sponsons. Sand the edges flat and sharp to begin with on these parts and then just slightly smooth out the edges... Just a tiny amount. In a perfect world you should/could keep them sharp but in reality its hard to get any paint to stick to a sharp corner so if you want to paint the parts that will be in contact with the water (ski & sponson running pads) make sure you put some radius on them but as little as possible...

Of that same reason - I personally don't paint these items. I only use epoxy on them - no paint - no clear coat. The epoxy I use is water tight though - so far we have had no issues with that and it's a bit easier to sand the edges sharp(er).

NOTE: the rear ski-ramp should NOT be glued to the tub permanently. It's meant to be mounted with thin double sided tape so you can change it or adjust the height etc. If you would glue it directly to the tub it will sit at the wrong depth and the boat will most likely run too light on the front sponsons in race waters.

Here are the batch of ski's and running pads that are sanded and ready for epoxy prep. These items will not be painted. Just epoxy. I have also made some extra running pads in different thicknesses: 2, 2.5 & 3mm thick. There are also a few different ski's in there that will be tested during the season. I'll get back when they are tested and if I have found anything that is an improvement. :)

This is the German chemical & water resistant laminating epoxy resin I use when prepping the wood parts. It's called Epoxy Resin C + Hardener C and its simply awesome. Protective gloves, house holf paper of a high quality that doesn't brake up when handled so to speak, a micro weight scale, mixing bowls and a bunch of good brushes that don't release any hairs.

Use masking tape on parts where you don't want any epoxy build-up.

Before "paint" you must seal all wood parts - we use the earlier C+C epoxy on all wood parts. The procedure I use is like this:
  • Brush on mixed epoxy (note that C+C is mixed 100:60 (resin:hardener) everywhere on for example the tub first. Use a brush to spread it and move fast - you don't want it to "kick" before you are ready. In the radio room and the "bate box"- use your glove protected fingers to reach areas where a brush won't do the job (like under the deck parts). Also use a small rod to spread the epoxy resin into the holes - but don't fill the holes. When all parts are covered with the epoxy use your hands (with one or two layers of protective gloves) and massage all areas of the parts you just now have brushed on epoxy on...
  • Then use the good household paper and start to remove as much as possible of the still not hardened epoxy...
  • The idea of this first layer of epoxy is to get it INTO the wood. You don't want it to create any gloss surface so to speak. Remove as much as possible. BUT there is an exception and that is the bate box (the small area in front of the transom) and the radio room. These are so tight that you will not reach them to use any sand paper afterwards so you can leave a little bit more epoxy here but not too much. 
  • When you're done with lets say the tub, move on and do the rest ot the parts in the same way and let it cure for at least 24 hours...
When the epoxy have cured it's time to sand everything again so it's a good idea to remove the masking tape etc before sanding starts. If you have left too much epoxy on the surfaces you will now notice that it's not easy to sand epoxy...
  • Sand everything smooth again and blow off any dust.
  • Re-do the masking tape.
  • Start over again with layer #2 of the epoxy resin. This time it's a little bit different as it's easier to brush on the epoxy as the wood surface now is smoother. If you use the R&G C+C epoxy it's perfectly safe to only use 2 layers of epoxy before paint/clear so when you are repeating the process and are removing the excess epoxy with paper rags you can leave a slight glossy surface. But just a tiny bit...
  • When all of your wood parts are done twice you should leave them for at least 48 hours before any final sanding. But the engine/tank compartment could use a third layer of epoxy and that you could do in between so to speak. If you are in doubt - leave all parts for a complete hardening for a week in room temperature before any final sanding will be done to start prepare for paint/clear. Remove the masking tape first though.
  • When all parts are fully cured it's time to do the final sanding! Be careful on all edges so you don't sand through the epoxy down to the wood.
  • I also re-drill all holes at this time to remove excessive epoxy build-up.
When the final sanding of the tub is done I glue the brass tube for the antenna tube in place.

In an earlier article I showed the magnet cowl hold downs - here I have mixed a batch of 10 minute epoxy with milled fiberglass and used that as putty over the protruding magnet. Then sanded it smooth to form a "bulb". Looks ok, I think.

If you have a cowl that has been molded without any gelcoat, it's a good chance that when sanding it will show up quite a lot of pores or pin-hoes in the epoxy surface... Up until these cowls I have actually not cared for a super finish on the cowls - I have seen the function of them only. But these where prepped (spray gun) with a 2K sanding primer that filled most of the pin-holes. After blocking it out most of the holes went away. If a perfect surface was needed then a second layer of the sanding primer would have been needed but it was good enough for these boats. :)

Next time it's paint and clear coat in: KEP's T2 .21 Build Series #13

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