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Posted for newlan2dl@aol.com:
Hi Folks
Awhile back I wrote about a technique for fairing areas with a minimum amount of sanding. I didn't have any good photo's until now but here you can see how it's done. Granted it's not my ES but this is my racing sailboat that is now about 99.9% complete and once it's no longer a lawn ornament, I can get going on the Lancair. To give some background on what is being done, the boat was in a collision awhile back and had the core in bow partially crushed. We were in a gale at the time of the collision and it was very dark. We never even saw what we hit. Anyway there wasn't any immediate flooding but that would come later. The collision occured at 0200 but it wasn't the following afternoon that the damage had progressed to the point that the inside skin was flexed to failure (carbon is VERY intolerant of folding and flexing and this being high modulus carbon exaserbating the problem). The boat started taking on water about the same time I noticed the bow moving each time it slammed into a wave. It never was a flood of water, just a trickle but the failure was progressing rapidly. With night falling and a rocky lee shore, we decided to abandon ship (It was gusting over 50 knots with 17' waves on top of large swells) in a minimal anchorage. There wasn't any protection from the wind since it was a low lying rocky outcropping that broke the waves. Anyway, we were picked up by the Coasties and the vesssel left abandoned until the wind died enough to be towed to Monterey two days later. I had no hope that it would actually survive in those conditions and not drag anchor but miraculously, it did. Water was apparently just below the salvers knees when they came by to tow it. So the bottom line is we did save the boat, it was totalled by the insurance company, I bought it back and had to build a new bow for it. And I had some other hull repairs where the Coast Guard smashed the port quarter but given 50 kt winds and kelp everywhere, they did a great job. Not ever having a histoory of knowing when to stop, I decided also to modify and repair the deck, design and build a new keel and rudder, install a larger engine, put in new electronics, add a new Gucci autopilot with gyros/fluxgate compass/wind point/GPS routing interfacing, repaint the interior, build a lifting keel trunk... Ironically, splicing in the new bow wasn't all that big of a deal. Maybe 500 hours or so. So the boat is virtually new. I'm at 2600 hours and only need another 30-40 to finish it. It took me 2650 hours to build it in the first place so I will be within hours of the exact amount of time it took me to build it originally.
Which brings me to the photo's.
To repair the bow, I cut off the front 13', splashed a mold then scarfed in a new bow. So that's about 1/3 of the boat's overall length of 37'. The photo's show fairing on the last of the splice below the waterline where I attached the new bow to the boat. The topsides have obviously been completed and were faired using the same technique. In fact when I first built the boat is when I developed this technique. It saved a LOT of time!
If you look at the hull below the waterline, you can see three aluminum battens 12' x 3/4" x 3/4" that have been screwed into the hull (only because the angle of the plane changes twisting the batten, otherwise the ropes would be adequate). The battens were first used to plot the the highs and lows and the highs taken down with a long board sanding block, in this case 33" long Velrco backed long boards. Then she was ready for battens since all that was left after long board sanding was low spots. The ropes which are often all you need, were slung around and tightened very snug around the fair part of the hull. The battens were then waxed and placed under the ropes, and once a good fair line was extablished, screwed at the ends. The lows were all that was left under the battens, and there only 4-6 feet needed fairing. Since by definition, these battens form fair curves, and the gaps underneath lows, all you have to do is pack a bunch of putty underneath it and once hard, remove the batten and what is left is a fair curve in putty. The top photo shows a detail of the putty bead left under the batten after the batten is removed. I also like to add some pigment to the putty so that I have a contrasting color when I'm sanding and know what my reference point is.
The beauty of this technique is there is NO plotting of highs and lows and going back and forth and no guessing about how much putty to trowel on which requires a lot of sanding later to remove excess. Since you know EXACTLY what the fair shape is, you waste little putty and little extra time in sanding and filling and sanding and filling.... The putty reference line you just cast is perfect and a hard line you can count on to be prefect. So once the battens are removed, a simple bit of light sanding knocks the flashing off and you are ready to trowel some putty between the reference lines.
In this set of photo's, the ropes are used to limit the flex a bit where it otherwise is lying againt the hull and might pull away once packed with putty. When you do mix the putty, I like to make it a bit thinner than normal sanding putty for three reasons:
1. It's easier to pack under the gaps in the battens
2. Since it is a perfectly fair line, you shouldn't have to sand that reference line much at all, 3. With the putty a bit thinner, it is less likely to push and hold out batten due to the viscosity being high.
If you use this technique, you will have to select the right stiffness batten. Here given the gentle curve and the long span, the 3/4" x 3/4" aluminum battens seemed a good choice. This would be way to stiff for say a trabsverse batten. For the fairing along the horizontal line, I used 18" x 1" x 1/8" G10 epoxy/glass spaced about every 12". Wood can be OK to use but you may have to rip several to find the right bend characteristics and NOTHING with a knot in it will work.
One final bit of technique. As you get to the ends of the lows, these gaps get VERY small and may go on for awhile. The small gap makes it hard to force in the putty so I will gently pull the batten back to open the gap while I pack it, then let it back down and gently wiggle the batten side to side a bit to remove any stress from the batten being forced out by pressure from the putty. I left a yellow lofting batten on the ground to illustrate how fair the rest of the hull is by the reflection. The top photo shows two of the black putty strips left after the batten is removed. The worst of the low is about 1/16" of so.
Anyway, I hope this helps anyone doing a significant amount of fairing.
I'm off to resume the misery...
Dan Newland
Super ES 0% complete but thinking VERY hard about it now.
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