Back to Home Page

Back to the building log


Bogged Down in Assumptions!
 Preparing a load of fairing bogg, judging the viscosity and spreading out on a table top to retard the exothermic reaction that causes excessive heat and premature curing.

 I had to get a beer and put on some old Arlo Guthrie to get in the mood to get through this one! I have spent hours going through the hundreds of photos taken this cycle to make some sense of the progress of the boat. I was feeling frustrated about the lack of progress until looking at the photos and then realising how much actually has been done. But which ones to select? (Twenty seven 8X10 colour glossy pictures with circles and arrows and a paragraph on the back of each one to be used as evidence…) There was a lot of 'wheel spinning' going on but with two hulls at least I could keep busy on one of them while I was pondering what to do with the other, and.. the weather was good.

So who out there has done bogging? There is no stage of build yet that I would call 'forgiving' but bogging really was intimidating. Some of the consequences of getting it wrong were apparent, excessive sanding for example, keeping in mind I consider any kind of sanding at all an abuse of basic human rights. Or the ugly thought of getting the mix wrong and having to scrape off part cured muck. A million possibilities but the little devil that got me wasn't one I thought of!

I rang up 'cat-man-do' Dave who knows a lot about it. I had heard bad news about using "Q-cell" bogg under the waterline but Dave said he had used it and knew many who did successfully. I split the odds and used a "cab-o-sil" and Q-cell mix. Dave reckoned the best way to bogg was to start with a thicker coat and get the right contour then when it is firming, apply a second coat of thinner mix, a 'skim coat' to smooth the surface and fill any blemishes. That had a very sensible ring to it!

Working on the chines provides an opportunity to take baby steps. Small areas with natural borders. I went over the keel panel with it's entombed layer of ply for grounding and both chines to the sheer panels. Geeez, I was impressed with myself. Why bother sanding! When doing the first coat I had seen some pitting as it seemed difficult to get the dry weave of the panels to accept the bogg. No worries, that's what the skim coat is for and indeed it seemed to work.

For sanding.. all I had to start was a Makita block sander. I went over the lot with it and thought that would do. Then a chance encounter with Super Cheap Auto's air tool section had me find a new love… an air powered 14" in-line job!! Couldn't wait to try it!

With a savage grit lashed onto to that thing and twice the rated air pressure I really had a good thing going and decided the first go with the little Makita wouldn't do after all! Amazingly I managed not to do too much damage playing with the new toy. Got a can of brake cleaner to clean off the oil the thing spit out occasionally though. For the finer grit I used the little Makita after the air tool. This worked well with the narrow and generally hidden under water parts. For the sheer panels I figure it would be better to have a "torture board" on hand with some 60 grit attached. Took a few minutes to build.

I sighted the first chine along the sheer panels and as far as I could tell it was pretty fair. I should have used a "fairing batten" but I hadn't read that far in the instructions yet! Anyway, the sanding routine worked pretty well. Air sander to take off the high spots, the torture board with # 60 and the Makita with # 80 to smooth. I think I did a good job on applying the bogg. The result was smooth and reasonably fair. The panels were pretty straight, so the result wasn't bad. Keeping in mind this was just for under the water line fairing. What was done higher on the panels was a light coat that will be done again when further along in assembly. The problem was these little pits…..

Hard to see them while sanding, till I blew off the surface with 100lbs of air. Then there were thousands of them, singly or in clusters. Recoating with resin didn't work. Minutes after coating it would be a hole again. I had Wattyl fairing compound and figured it's thick epoxy filler could be forced in to fill. But Wattyl specified the compound be applied over primer.. so.. a complete wash down for the shed to remove dust along with the hull itself getting a scrub.
The paint I used is one I know well. EP Universal by Wattyl is a really good and well priced epoxy primer.

So did the compound work? Most of the time. But often, after a quick sand, the pit would be revealed again. GGhrrrr! But it didn't matter anyway because every time I looked I found more. They were hard to spot so I was mixing small batches of the stuff several times a day and sanding a few hours later. I wasted days on that before I turned full attention to the other hull.

The plywood keel panel cover and taping of the outside chines has been covered in previous instalments. I'll only deal with the weird stuff that happened on this particular job. Taping on the outside of the port hull I noticed "outgassing", or the escape of expanding gasses, from some of the screw holes that were being covered by the joints. Such was the degree of it that I was considering if I should pull the thing off before it set or what? I sent an email to Michelle at ATL and the phone was ringing as I walked back into the shed! Her advise? Keep at it and fill air pockets later with a syringe if need be. I kept rolling the consolidator every few minutes until the stuff finally went stiff and stopped. What a hassle! But no trapped air. Gassing out of a screw hole that penetrated the core didn't surprise me except this particular job was the most extreme case I had seen.

I prepared another full length tape. After applying it to the hull, I turned my back on it to gather up more resin and a roller. When I came back I found the whole lot on the ground! It was blowing a gale that day and a gust got through the tarps, lifted an edge and stripped the thing off. With resin going off and Kay helping to hand pick off the debris, and amongst much creative swearing… the tape was replaced and consolidated in and covered with peel ply…. However, there are several local flora samples encased in our boat now.

"Wet on wet" is the term for re-coating over epoxy before the earlier coat cures. Going about it this way makes a better mechanical bond and saves work because when epoxy sets hard it leaves a surface contaminated with "Amine blush", an oily or waxy residue that has to be removed, and a surface that should be roughened for bond. As bogg will be sanded anyway, it's efficient to build the whole thing at once. So that is what I did… this time! I had two layers of glass to put on the keel panel and two layers of bogg. I started about 1400 and had to watch over the glass for gassing from the screw holes. By the time the glass was getting firm it was going to be late, Off to Super Cheap again.. this time for those 1000 watt work lights.. on sale for $29. The bogging started about 1900 and went till about 2100. Application of Peel Ply fabric mentioned elsewhere in these reports, leaves a hardened epoxy surface clear of blush and ready for bonding but it is a lot of work to apply correctly and for these four layers would have been inefficient of time and money.

Next day the blush was so thick it would clog sandpaper so a wash down and dry was in order but it sanded well and showed no pits!! I credited it to the particular bogg applying tool I had used. The "angle of attack" must have been off before…

And the sander I used this time was one picked up from Steve Halter who recently finished up his Schionning Wilderness 13.5, "Cheetah". Steve and PJ can lately be found making a nuisance of themselves with Cheetah around the whits. (see the Rendezvous article this edition). A "Rupes" brand 8" orbital…. Serious stuff! Wouldn't want to use it on a broad flat surface.. it would look like a mine field afterward but it sure has it's uses. With an 80 grit pad, it will put a finish sand on a hull quick smart.

So with a head full of confidence and a heart full of ambition… the next day…


see the remaing part of this article below the photo log below

Using a mortar trowel to spread the first layer of bogg. 
 The tile grout spreaders available at Super Cheap Auto or local hardware store are very useful for cleaning off excess without stripping off where you want it and they leave a clean edge.
 The open weave of the panels makes it hard to get anything to fill the little holes. This example was saved for the "skim coat" to fill.

 The second or skim coat of bogg is mixed up when the first layer has just firmed up. This is very runny, almost like paint rather than filler.


BTW.. I use these buckets a lot.. $.85 so use as a disposable.

 working in the skim coat with the tile grout spreader.
 Use the paint brush to glob on some skim coat bogg and then spread.
 This is being done as a learning exercise and as a first coat. The sheer panel can't be adequately faired until the sheer line to deck has been finalised. I'm using a wide metal plasterers tool to work the bogg.
 After the plaster tool is done I go over with a 1 metre long piece of scrap Gal sheet with a smooth edge to clean off the lines from the spreader.
 Next day start sanding before the stuff goes too hard. I start here with the air powered in line sander with savage grit. Working back and forth to keep an even surface. The bogg here is thin so the colour that comes through from the panels indicates the depth of cutting. You can see what you are doing that way.
 Then with the smaller block sander and 60 grit.
 With 60 grit again and with home made torture board.
 Installing the thin ply skin to act as protector for the duflex keel panel. I use anything heavy to keep the air out of the resin between the ply and keel panels. The bricks reduced the use of screws needed to do the job so less holes to fill with resin later.
 From the transom..
 While the previous step is going on, back to the shed to prepare the first hull for painting by washing down it and the whole shed to get rid of dust. I will give it a day to dry out.
Taping the outside joints on the bilge panels on the second hull.. 
 I got a length of heavy rubber strip from the local rubber store and cut off pieces to suit. Makes a good spreader for inside corners
 and then clean off the extra with a white plastic putty knife. These nylon things are reusable as epoxy doesn't stick to it. A quick bashing the next day and the stuff falls off and ready to reuse.
 Rolling on the tape over the keel panel and ply that was fastened down the day before.
 Click here for part 2 of this article. Important!