Fairing, Port hull

Full Fair?

Posted by Paul

Another weekend of solid work on the boat. Well 2 six hour days. To me unless there is a task such as glassing that must be finished in one session so therefore the session lasts as long as it takes to finish, 6 hours is about the limit. I start around noon and finish at 6pm. I know I could get more done if I worked longer hours but it is a hobby not an obsession. Besides, sanding is hard work. I also managed 6 hours during the week.

So I have now sanded the whole boat. I then filled in low spots and tape edges with more bog and used the trowel edge to scrape the bulk of the bog off so there will not be too much more sanding to do. I have also built up the edge on the main chine (the only one visible above the waterline) so that I can be sure to have a straight chine turn.

chine edgehull reboggedfair hull

From now on all of the sanding is with the sanding board I made. I have attached the hookit and attached the paper and the board works great. I will sand up to and down to the main chine before rounding the chine off once I am satisfied that it is straight and fair. I will also sand along each panel with the long board to be sure it is completely flat and smooth. I am hoping that the Bohler has done the bulk of the work and that there wont be much hand sanding.

I have marked a line about 250mm below the main chine. The main purpose of the line is to mark another line along the chine so as to be sure the chine is exactly straight. The method is to mark a centre line along the chine then another line 10mm above and below. You then sand to these lines, then sand the chine flat from the centre to the 2 lines then round off the 2 new chine edges. As the chine lines are sanded off I will still have this lower line to sight (and or measure) against. It is also the lowest point to which I wanted to fill so I also had a straight line where the surface rises to the high point over the tapes. I also plan to mask the hull at progressively lower points with each coat of highbuild so that the coats also feather out.

I hope to have all of the rest of the sanding completed next Saturday. Unfortunately I wont get to do any work during the week as I am off to Melbourne again on Tuesday for the rest of the week. I am fairly certain the hull is already quite fair. I tried turning the lights off and shining a torch along the hull looking for dark spots caused by high spots casting a shadow but didn’t seen any. I may have some low spots. I am told that the moment the white high build goes on, any imperfection will become instantly visible. It is possible to fill again on top of the high build but the idea is to minimize this.

Another trick I have been told is to spray a fine mist of dark spray paint onto the hull and sand it off again, which will highlight the highs and lows, as the highs will sand the paint off first, but this is a last resort if I cant get the surface looking fair without it. I also haven’t sanded the chamfer chine turn. This turn is concave so I need a rounded sanding block, a tip Sean gave me is to get a swimming pool noodle as a long sanding block. It is about the right radius and is long to minimize the work. I have sanded down the high points down to fair on most of the hull, except on the keel. There I left as much bog on as I could and filled the valleys. I figure 2 things, firstly this will not only be under water and therefore not visible, but also under antifoul which is not going to be fair anyway as it is so thick, and secondly I figure that as the bottom will not doubt scrape many times I want as much between me and the bottom as I can get. I know it wont make any real difference but a small piece of mind is all.

chamfer sanded looking forwardsanded bow looking aftkeel sanded

As I have said the hull is quite smooth to the touch. At this stage that is all I can go on. I have placed straight edges on to check for fairness and the hull feels smooth and flat. Once the white high build is on I am hoping the hull will then also look fair. A reader has suggested that I need more bog because you can still see the tapes. But this is because the layer of bog is thin. It doesn’t need to be any thicker than enough to remove the edges of the tapes, so that you cant feel them if you run your hand up and down the panels. I do it with my eyes closed to see if I can detect the edges of the glass. I fill and sand until I can no longer find the edges this way. As I have said I hope to finish sanding next Saturday. Then on Sunday I will give the hull another coat of resin to seal it, then on the same day, once the resin has almost set I will give the hull a coat of white highbuild.

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