Bogging, Fairing

Less is more

Posted by Paul

OK, sorry about that. Its been a couple of months since my last update. I have not had a computer as my new tablet stopped taking charge so it had to go back for repair, and my laptop overheats very fast and locks up so I had no way to update. I am updating on Jo’s macbook.

Fairing the hulls is progressing quite slowly, a combination of not getting to the shed to work often enough, heat in the shed restricting output and just the slow going of hand sanding hulls. So not much new to see either. Its very hard to show the progress in pictorial form of the tiny incremental changes to the hull sides. In fact, it is very hard seeing the fair or unfair surface with the naked eye. One change not invisible is that any sign of the hips are gone.

port hull hips all gone starboard hull hips all gone

What happened fairly soon after the last blog post is I learned that I was still a long way from fair. (not so bad indeed! never goad Murphy). I got the layer of bog onto the hull sides screeding from the high point on the hull side from the join between the hulls and the curved deck side to the chine at WL300, screeding top down and gave it an initial sand down with a combination of orbital and long board. I still had many lows and holes to fill but then I noticed another near invisible to the naked eye issue (my naked eyes at least).

I correctly noted in my last post that the hull to curved deckside join is the high point on the hull sides. (or the widest point on the boat at any given length). What I did not realise at that time but it dawned on me instantly is that the chine at WL300 is a join of the waterline panel and the slab hull side panels and as such received 2 layers of tape, about 1.5mm in height above the panel height. And of course, the hull side panel to curved hull to deck curve panel is another 2 layer tape line (1oomm over 150mm tape full length of hull). The combination of the highs these 2 tape layers create is a 1.5mm hollow. Screeding top to bottom does not fill this hollow, the bog flows over the level regardless of what height and adds a layer of bog, not uniform in thickness. Sanding the bog, the first sign of the hollow appears. The long board sands the highs of these 2 tape lines off and barely touches the panel itself.

straight edge on hull straight edge on hull 1

A straight edge across the hull side top to bottom confirms the obvious. I ought to have known it would be there. And its uniform along the entire hull panel, on both sides. They are far enough apart that just fairing out the tapes like on other parts of the build is an option, and the slightly concave hull sides dont look out of place. But with the addition of the layer of bog its difficult to get a uniform finish without fairing out the hollow. And in checking the hollow with an aluminium straight edge the highs are marked by the aluminium edge. By moving the straight edge (it must be aluminium for this to work) up and down over the panel the highs are marked by the straight edge as if it were black chalk. Anywhere marked is the high point. In some cases the high is the bog layer applied, but in most places its the 2 tape lines, meaning not enough bog fills the hollow to take the highs out.

high spots marked high spots marked with edge straight edge screed

The black chalk marks show that the highs are uniform along line of the chine and the hull/deck join which is at the centre line of the port holes. These highs also provide an easy (ish) way to fill the hollow in a uniform way. Run a screed of bog using these highs as the rails to run the straight edge along. It means a slightly runnier bog so that it pulls smoother, but is pretty much in line with my prediction last post of another bog run. I just didnt realise at the time it would be required to fill a uniform defect that I couldnt see without running the straight edge.

hulls sides bogged again hull sides bogged again 1

The bog is yellow because the resin I am using is Kinetics which has a yellow hardener, I dont know why, it just does. I didnt bother to touch up holes or imperfections in the screed, nor did I fill them once the bog layer set. Next I started sanding the bog layer to see if I still had any hollows. I did. I filled them with more bog, in places trying some Technifill to see if it was nice to use (its more expensive than mixing your own bog). It pulls nicely and sands a little easier than powder/epoxy made bog, but for me, tight for money, its not worth the extra expense. Its blue in color, so easy to see where I have used it. I was given a sample pot by the manufacturer to try, its ok, but as I said, money is too tight now, and Terry had some samples too and didnt use them so he gave me his.

Sanding is 2 stage, first stage I use the Bohler (if you have been reading for 9 years you will know what it is, if you havent, its an interesting machine that seems to sand without digging holes) then hitting it with the long board. There is no alternative to the long board, it is the only way to finish fair. Or to know you are fair. Once the sanding marks hit the entire surface you know you are fair, any place they dont hit is a low, the bohler will hit the lows in between the highs, the board will not until the highs and lows are the same height, which means, a fair surface. Long boarding is very hard work, especially on hot days. Some days I can barely lift my arms at the end of only 4 hours of it. And that is at the rate of 10 minutes on, 5 minutes off. But it is addictive. Many times I say thats it I am done for the day, and and hour later I am still at it. But as I say, 4 hours sees me out now. I wish I could go longer, but I am too old and tired for much more. At least I feel back to new the next day.

port hull part re bogged port hull second bog run

A run of the straight edge even before sanding shows the hollow gone. And reveals the points where I need another run of bog, some are a meter wide, others just 100mm across. I mark them using the straight edge, if there is no light or gap showing its pretty close to fair, if it rocks like a see saw its a high point which I mark with an x and if its a hollow (light showing) I mark it with a circle around the edges of where the hollows starts and ends. I fill the hollows and sand the highs. A lesson here I learned is that as tempting it is to fill lows because I am exhausted and sick of sanding, its actually easier to keep sanding the highs down (provided there is still bog to sand, if you see glass you cant keep sanding) because the filled areas will eventually still need to be sanded, so you may as well sand the highs down to meet the lows than fill to the highs. More bog means heavier boat, more expense (resin and power) and for no better finish. Less is more.

straigh edge shows low gone bog patch on lows 1 bpg patch the lows

looking down fair hull side port side before sanding starboard sanded and high line marked

So for now I am still sanding, filling smaller holes and blemishes. The sanding is a combination of 45 degrees up from the waterline chine in either direction and down from the hull side join. But I also have to sand horizontally from one section to the next to take highs and lows out. If I run my hand along the hull side as I walk along I can feel my hand move in and out as it hits highs and lows. These must come out. They are even more important to remove than the concave shape, because if left, the moment the gloss hits it, light is distorted off the highs and lows at different angles and they all become instantly visible. So its a balance of getting these rolling hills and valleys out whilst maintaining a fair surface vertically. You can see the valleys, they dont get scratched up until the highs are sanded off to the height of the valley. But once a coat of dust covers the hull side and you stand back a little it all disappears again, so using feel I find them all again, until I get rid of them all.

I have marked the line of the high point, the line also marks the middle of the port holes. Its a good point to fair to. I can run a pin stripe along that line after painting to hide any defect if the line does not fair out or blend out, the ports take up a good part of it so its a good point to fair to. I intend to try and get the sides faired all the way to high build fair then move on to the hull to deck curves and get them as fair as I can.

port hull partial sanded stern tow points fitted

I have fitted the rear tow points. I will fair the panel totally before glassing the step tops down. To punctuate the sanding (its hard boring work) I will be making the helm station over the next month or 2 before moving on to the highly curved side decks. I am also saving some money to buy another type of highbuild called International Micro Surfacer. Its a very high solids high build (much thicker than the Jotun I have used so far). Its about $600 for 20 litres. It is supposedly much softer and easier to sand and is a final step to getting the surface fair, it fills blemishes including pin holes and whilst its not as fine as the Jotun which I will use over the Micro surfacer as a final finish to be extra sure of the fairing. This next pick is of Terry’s boat before it left the shed. If I can get just my sides as good as this then I will be extremely happy. I doubt I can, its the difference between amateur and pro.

Terry's mirror finish

I also have some exciting news. I may be getting back into business. I have imported some samples and am evaluating the sales potential. If it works out I might be able to quit the day job, spend more time finishing this thing and finally launch it. More on that when I am confident I have something to tell. Thanks for sticking with the build. I have passed the 10 year anniversary. A decade by in the blink of an eye.

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4 thoughts on “Less is more

  1. Matt

    Hi Paul,
    I use a modified pneumatic air file as my main tool for long boarding.
    Modified means: removing the original pad and making a LIGHT, FLAT, STIFF pad that fits the Velcro sand paper sheets made by 3M. Changing paper is fast this way. I made a 2nd pad for glue on sandpaper to have a choice. Manual long boarding is still in the game, but at a reduced rate.
    To get an impression of a fished surface I wet out with a slow evaporating solvent.
    Darker colours with clear coat on top are too hard to fair well enough at least for me. White is one of my all time favourites and its cooler in the tropics.
    Keep the good work up

  2. webmaster

    Hi Matt, thanks for the advise. I have a loaned air file with a widened base to take 110mm sheet on velcro and about 500mm long. Unfortunately even with a really strong compressor the sander stalls with coarse paper. I have not tried it yet with less coarse paper, and perhaps reverting to the original width might work better. And yes I reject any sanding device powered or manual that does not have hookit for paper changing.

    I have not got far enough finished to use a wetting agent to see the quality of work yet. Actually I did on the roof when I got as far as high build on that, and did get to see it in a semi shiney state and am pretty happy with how that turned out, considering the mess I made of making and fitting it!

    I also agree, white is my color of choice, with perhaps a slightly darker tint for the non slip, light grey for me.

  3. Matt

    we have a non water based skid paint available in Canada called KIWIGRIP , made in NZ, go figure.
    I bought a 50% larger then needed compressor and should have gone for 100% larger then needed. I tried to link compressors in all ways I can think of, ceck valves etc. It does not work well.

    I spent the last few days washing the entire outside on my cat build here. It is just above freezing and the water stayed on quite a while.
    It really helped to check fairness even on the rougher patches. Less dust flying too.

  4. Glenn Harris

    Hi Paul,

    No matter how good the finish some other irresponsible boat owner can bring it undone in the blink of an eye. I have my Waterline 1320 on a swing mooring in the Burrum River, Q. Last Friday night, a 25 ton motor boat broke its mooring and smashed both my bows. So much work undone – heart breaking to say the least. Yes, swing mooring can be troublesome but so can expensive marinas.

    Happy sanding

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