Bad bog, Bogging, Bogging Port hulls

Disaster Strikes!

Posted by Paul

They say trouble comes in 3’s. The week before last the timing belt on my car broke on the freeway instantly seizing the motor doing around $4000 damage to the engine on my car in Melbourne, and I was in the process of getting it ready for sale as I no longer needed to have a car for the few days a month I am in Melbourne. Then last week my laptop finally died, it had been struggling for a while, meaning I had to go and buy another one. I did get a good run out of the last one though, I had it 2 years and other than people connected to a heart/lung machine in hospital I doubt there would be too many people more connected to a machine than I am with my laptop. So this week came the 3rd in the trilogy of bad luck. This time on the boat! And this one is big. Not terminal but bloody annoying and a heap of hard work fixing it.

We had to go to Melbourne on business last week. We left (we drove down because I don’t have a car down there at the moment and wouldn’t you know it I needed one this trip!) very early on Tuesday feeling very good about the boat as we had managed to get the hull bogged on the weekend or so we thought….If you recall we glassed the hull with Brett’s help on the previous Friday and decided we would not put the peel ply on as the resin would still be green and we would bog directly onto it the next day achieving a chemical bond and saving the peel ply. We did apply the bog on the Saturday but we only had Jo and I doing it and we believed that we had to get it done that day before the resin on the glass finally went off. After about 15% of the bogging the plastic pump on the West hardener drum broke (it pushed down into the drum) and as I was busy applying the bog and because I felt under pressure to keep going I asked Jo to keep mixing the bog by using a measuring cup for the resin and hardener instead.

The bog is made with West but the resin we used all day Friday on the glassing was ADR, which has a much longer set time which in turn gives you more time to work with and also stays green much longer which is also handy for working with the next day in our climate. ADR uses a 4:1 mix by weight. West uses a 5:1 mix by volume and the pumps take care of this ratio for you. But as the pump broke we inadvertently started mixing the bog at 4:1 using the measuring cup. I am sure we achieved a perfect 4:1 mix but unfortunately that isn’t much good when it should be 5:1. We were of course oblivious to the error in our mix and worked away all the rest of the day and didn’t realize our mistake until we got back from Melbourne on the weekend just past.

The consequence of this is that the bog did not set. It was still tacky on the Monday before we left for Melbourne and I didn’t think too much of it thinking it would take a while to harden. We got back on the weekend to find it still rubbery not hard like at the stern which had the proper 5:1 mix. I rang Brett yesterday and the upshot is I have to strip all the bad bog off, re-sand the hull to remove as much of the stuff as I can, then re-resin the hull before re-bogging the hull again. The soft bog is just too soft to cover over and will be a weak point between the top gelcoat and the glass and will probably delaminate and is unlikely to be waterproof. Not to mention that it cant really be sanded anyway as it just balls up like it is rubber and kind of melts. It isn’t melting it just has no rigidity so seems like it is melting under the sand paper so even if you could cover it over I can’t get a smooth finish with it anyway.

I am using a 25mm chisel to remove the stuff, it is too hard to remove using a scraper, but then I have to be really careful with the chisel as I don’t want to cut into the glass under the bog. I even tried deliberately blunting the chisel (by dropping its blade onto the concrete floor) but that just made it harder to remove the bog so I had to re-sharpen it. In fact I am finding it easier to use just half the chisel along the removed edge so using a larger chisel wont get the job done any faster. And that is super difficult in the chamfer curve or wherever I hit a tape edge. And It is really hard work on your arms. I am sore after about 20 minutes and find I have to do something else for a while whilst my arms recover. I worked at removing it for about 2 hours on and off over 4 hours today and got about 10% of the bad bog off, so at this rate I figure it will take me 20 hours work to remove the bog, about another 3-4 hours to sand it, and then another 1-2 hours to prepare the hull again (final clean ready to re-resin and re-bog), then 3-4 hours to resin coat and 4-6 hours to re-bog the hull. That’s about 36 extra hours work, which at the rate I can put in, about 3 weeks. Maybe I will get better at it as I go and the hours wont be quite so bad but it is still a bunch of extra work I could have done without. And I guess we have wasted a couple of hundred $ of material to make the bog.

I was aiming for a turning party for my birthday in 3 weeks but doubt I will be ready now which is a bit of a shame. Anyway amid this gloomy news the good news is (there is always a positive to be found!) that it is all fixable to the point where once fixed will be as if it never happened. The moral of the story is DON’T RUSH!! And remember the different mix ratios. I will take some pictures of the process tomorrow.

Special thanks to Randall who is building an 1100 in Melbourne and invited us over. We visited him last week and took a look at his hull, he is just behind us but will soon be ahead now due to our mistake. His hull looked the same as ours (other than it being a different design) and re-assured both of us that we were on the right track. I had not seen another hull other than ours at the same stage. I also have to commend Randall on his neatness. His shed is immaculate and shames me into cleaning up and putting things away and setting up such things as resin dispensers and cloth dispensing rollers etc. Jo simply wont allow me to be as messy as I have been and is considering swapping teams to Randall’s crew if I don’t lift my game!! (Especially since it took us nearly an hour to find a missing hammer today!) I am a bit rattled at the moment. Nothing 20 or so hours of scraping bog wont fix.

I look forward to posting some good news again soon.

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