One of the tricks to smoothing out imperfections in the hull shape is to apply filler with a notched blade. This creates triangular ridges that make sanding large surface areas fairly easy because you're just knocking off the tops of the ridges rather than having to sand a solid surface. In this instance, I'm using a mixture of a little more than two parts micro balloons to one part epoxy; mixing the heck out of it with a drill and paint stirrer. I decided to tint this layer so that I could distinguish between each application of fairing material.
Application of the filler seemed to work out best with a trowel that I made from an 8 inch sheet rock blade. I found that 1/8 in. notches every half inch worked well. I just cut them in with a file.
Once this fairing compound was applied and cured, I used a 4ft. sanding board to fair the hull by hand. With the ridges running fore and aft, I worked the sanding board at 45 degree angles from left to right and right to left. I made the sanding board from a lightweight cedar board and a carbon fiber tube. I also discovered that I could introduce a precise curvature in the sanding board by securing a small strap across the tube with sheet rock screws. By adjusting the tension of the strap I was able to create a slightly curved board that followed the overall shape of the hull.
With an ipod and a little shoulder work, I was able to smooth the hull down until the high points just began to show. At first, it seemed to be a daunting task to hand sand two 44ft hulls, but breaking the job into a few sessions over a couple of days made all the difference. After a few days of this, If asked, I would have to decline an offer to play a game of Twister.
After sanding the tops off the ridges, I used a straight blade to fill in the grooves with untinted epoxy micro mix.
This resulted in a good start to a fair hull. From here, I'll use finer and finer grit paper to eventually arrive at a surface that is suitable for a final top coat.
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3 comments:
Love the your blog!
On a previous post about fairing, you pictured a West system notched spreader that leaves 3/16" ridges to be sanded. Is there a reason why you made your own notched spreader?
Also, where do you get your 4' sandpaper?
After a good bit of experimenting, I discovered that a 8 to 10 inch sheet rock blade with 1/8th inch grooves every 1/2 inch, works great. I mixrd a batch of filler, smeared it on quick as I could with a 3 inch putty blad then started applying the ridges. Once cured, the hull sands like butter with a long board.
I made my long sanding board with a nice clear lightweight piece of western cedar fitted with a super light handle made from a carbon fiber tube. A trip to the local rental center had a stack of floor sanding supplies and paper for their rental machines and I found a stack of 20 grit that was able to cut to the right size and apply to my board with 3M 90 spray adhesive.
Nice work. Cool Design
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