Lightweight Topping Coat

This past weekend was spent back filling the foam joints with a lightweight micro-balloon mixture, working on a couple of test infusions and sanding the hull interior.

I also glued some 16" (406mm) extensions onto eight sheets of 3/4" (19mm) MDF.
This is curing now and maybe tonight I can get started with the beam molds.

The fabrics order should be in later this week or sometime next week.

As for epoxy mixing, I decided to try out a tool I had purchased a while back and found it to be really worth the money and worth mentioning here.

"StirWhip" 8" mixer attachment.

I ran it with my 12v drill at a very low speed and found it did a really good job creating a smooth mixture with less air entrainment than mixing by hand. I start by mixing neat epoxy (part A&B) and then scraping the sides and bottom before mixing again and then adding the filler materials and mixing again. I found it best to tip the bucket towards my chest and use the drill to slowly "roll" the mixture. This allows the epoxy to incorporate the filler material without causing it to float out all over the place too much. It doesn't take long and the results really are much better than hand mixed, not to mention much easier. Once the mixing is done, I'll put the drill on "High Speed" and fling the excess material to the sides. Afterwards, the "fingers" on the mixer are easy to wipe off and make ready for the next batch.

Moving on to the infusion tests, I have this idea of making my own "Pre-Preg" for doing the Beam Layup. The beams themselves consist of several layers of Fiberglass and Carbon Fiber.
I hear that Carbon Fiber can be tricky to infuse and the idea of doing an infusion with a layer of CF buried under some layers of Fiberglass doesn't appeal to me in the least (especially at my skill level and the critical nature of the beams themselves) The other option is to do a hand layup/vacuum bagging.

Hand layups work, but do tend to leave a lot of extra resin (and air bubbles) in the fabric, so if you have the means to use some sort of vacuum assisted method then I think you probably should.

Anyway, to test the plan I used some left over samples of 18oz/yd 0/90 Fiberglass to create a seven layer stack measuring 50" x 7" (1270mm x 178mm).

I wanted to check out a few things:

- Do I need Peel Ply between each layer

o No, the Peel Ply actually slowed the resin flow down too much.

- Do I need GreenFlow between each layer

o No, there was no real difference between the section that had one layer of GreenFlow in the stack vs. the section that had GreenFlow between each layer of glass.

- Will the epoxy flow well enough through the Enka-Fusion, or do I need to use the standard Spiral wrap?

o I couldn’t see a difference in the Resin and Vacuum flow between the sections with Enka-Fusion or Spiral wrap

- How difficult will it be to handle the wetted out “Pre-Preg”

o Very easy to separate the layers, roll up and manipulate.

- Will the top layer stick to the other layers and create a lot of weave distortion/tearing

o No, the layers separated easily and any weave distortion was easy to rectify.

- Does it matter if the GreenFlow is at the top or bottom of the stack.

o No difference in Resin distribution, except that if I leave the Greenflow at the bottom of the stack it serves to lift the fabric off the surface allowing any pooled resin to collect there.

§ Next time, I will install a “Reverse Pull” T fitting into the supply line. This will allow me to remove excess resin from the inlet side before turning off the vacuum. I did notice that the bottom layers were much wetter than the top layer. However, this was mostly my fault since I didn’t cut off the supply until the entire stack was nearly finished infusing.

So all in all, it was a good test that answered a lot of questions.

It does take more time on the setup side, but once the patterns are cut out and infused, I’m thinking I should be able to lay it into the molds in almost no time at all without having to play around with a squeegee and chip brush.

This is the left 1/3 of the Test Stack.
The bottom left is Resin Supply.
Resin goes directly into GreenFlow media via standard Spiral Wrap and then moves to the top of the picture towards the Enka-Fusion Vacuum channel. Seven layers of glass are fed with one layer of GreenFlow at the bottom of the stack.

This is the middle 1/3 of the Test Stack.
The Resin supply switches to from Spiral Wrap to Enka-Fusion and the Vacuum path switches from Enka Fusion to Spiral wrap. You can also see towards the right side of the picture where I start to add GreenFlow media between each layer of glass.