Priming steel hulls.....WARNING!

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slug
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Priming steel hulls.....WARNING!

Postby slug » Fri Jul 01, 2016 9:13 am

Just read Dan Hennis's posting on sandblasting and priming his Goliath, and I'd like to tell my issue with this event.
When we built our steel sailboat in the 90s, we sandblasted the hull and painted it with Awl Grip primer. It was in a heated workshop all the time, and we thought priming it would keep everything nice and rust free while we finished the rest of the boat, a period of 5 years approx. Turns out primer is exactly that. It is NOT a sealer, and is designed to bond the finish coats to the steel.....not seal or protect it. Some even have acids in them to assist the bonding.
When we launched her, everything looked good, but the next haul out we noticed blisters in the paint. The steel under the blisters was rusted. Awl Grip was contacted and were assured that the process was done according to their very stringent guidelines. They could find no cause, and of course no warranty.
We blasted the hull and repainted using International's primer and topcoated with Imron, and the problem was solved.
SO, the conclusion was that the moisture in the shop ( very dry environment) bled through the PRIMER and rusted the hull BEFORE the topcoat was sprayed later.
Just a word of warning to any one contemplating leaving a steel hull in primer for a period of time.
Doug

Kevin Morin
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Re: Priming steel hulls.....WARNING!

Postby Kevin Morin » Fri Jul 01, 2016 12:26 pm

Doug, sounds like a pain in the stern to have to repaint in just 5 years?

I have not personally (fully) painted any steel hulls but I have painted industrial steel fabrications more than a few times from blasting to top coats as I was part of a crew that worked offshore doing just that work on oil and gas production platforms here in Alaska. The crew leader was an experienced hand that made sure we heated the metal prior to primer coating to make sure 'the dew' was off the metal. It was offshore, so even in the breezy but not rainy days I'd assume it was humid on those platform surfaces?

He'd insist we take propane torches to the metal to be painted- and leave the heat on 'until the dew ran off' or the metal was hot enough to dry off the water vapor present (propane burns and a byproduct is water) even on freshly blasted steel. (You could see the wetting from the flame and then see the wet area's edge dry off and 'run from the heat'.) I'm not sure if this was necessary but it seemed to work- we were applying the various DeVoe paint products- primers and topcoats- and they seemed to stand up for years of offshore weather?

I guess even in a shop; vapor could condense as a film that could be trapped by primer(s)? Sorry to hear of your extra work! Glad you found a solution in the other brand of paints. Do you have pictures posted somewhere here about?

cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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Bill Edmundson
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Re: Priming steel hulls.....WARNING!

Postby Bill Edmundson » Fri Jul 01, 2016 2:05 pm

Read carefully. Many primers have a maximum recoat life. Some most be coated within 30 days. Inorganic zinc can go years by itself, if properly applied. IZ also has a minimum cure time before recoating that depends on temperature and humidity.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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aero_dan
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Re: Priming steel hulls.....WARNING!

Postby aero_dan » Fri Jul 01, 2016 9:08 pm

Hey guys,
Dan Hennis here. I am sorry for not keeping up on the forums. I have been a bit busy with the boat and the blog. I am thankful there are a lot of other guys out in the "ether-world" that know about all the things that can go wrong in a build. I have to say, that my experience from body school, to the many shops I have built and sold, and the fabbing I have done since, has given me almost enough confidence to complete this project. As for the epoxy primer, I was only planning to have it uncovered for less than a month while I finished up the inner hull details like stiffener welding, and various attachments and fittings. I agree that 30-60 days is about all a metal surface can stand in just primer. I have built a couple show cars that seemed to take forever. And at about the 120 day mark, bodywork seemed to go bad even in a good shop, ... not to mention the "hanger rash" that inevitably occurs in long projects. I think the worst "project" I ever worked on was a year I worked at Bremerton Naval Shipyard, on the USS Ranger in 1984. I know, that is a floating oil slick... But I learned some vaiuable information from a few old blaster/painters there. One thing was, never feed Alkaseltzer to a seagull! :lol:

Anyway, I was planning to use the primer as a very short-term protector, and it would have to be spotted in where the welding was done, but here in Missouri, (Unlike SW Idaho), things rust fast. No worries though, It will get a fresh scratching, and primer-sealer after the primer-surfacer is all fixed up. I have been in discussions with both the "Chassis Saver" folks and the Por 15 folks. Both have outstanding products I have used before, for both automotive and marine.

So Guys, please keep on thinking of stuff that can go wrong. Nobody knows it all, and I will be the first to admit it.
Better, faster, cheaper. Only ever found 2 of the 3! (But still lookin.)
So many boats, ...so little time.

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Re: Priming steel hulls.....WARNING!

Postby slug » Sat Jul 02, 2016 9:30 am

Kevin; Here are some pics of the Brewer designed Kaiulani 34 we built. We meaning my wife (who did all the welding of plate to longitudinals while I applied pressure to the plating outside) and a very good friend who helped with the hull and deck build.
Attachments
ps_2016_01_19___16_37_08.jpg
hull skeleton
ps_2016_01_19___16_21_38.jpg
primered hull
ps_2016_01_19___16_15_58.jpg
finished boat

slug
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Re: Priming steel hulls.....WARNING!

Postby slug » Sat Jul 02, 2016 9:40 am

A couple more. The shop built roller used a Toyota transmission for forward and reverse. Verna was the "driver" while Dave and I rolled....both plating and longitudinals. The temp. angle frames were welded together in port and starboard pairs and bent on the shop built press. I bought plans from a fellow in the US and actually sold the roller to a metal boat building outfit in Kingston ON. who are still using it 15 years later!
Doug

Incidently, one of my best purchases was a Milwaukee HD nibbler (10 ga. capacity.) We were able to shear sheets right on the boat in place.....minimum grinding. A great tool. For the rub rails I sheared 2 x 2 square tube in half, welded SS nuts to the inside and topped with wood after.
Attachments
ps_2016_01_19___16_34_02.jpg
forming temporary angle iron frames on press.
ps_2016_01_19___16_32_16.jpg
shop built roller.

Kevin Morin
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Re: Priming steel hulls.....WARNING!

Postby Kevin Morin » Sat Jul 02, 2016 11:59 am

Doug, neat looking hull! Is that rounded or radius chine? The shop built roller looks like both English Wheel & Pyramid Roller? Nice tool.

If I understood some of your references (??) you formed some hull panels with green edges then nibbled them to outline shapes while actually laying on the framing? Were those panels fully cupped or were they cylindrical with a main axis still in the plate?

Roller/wheeling machine has an electric motor, gear reducer, then an auto transmission to reverse the drive? I'm not sure what's happening on the three bottom shafts in the work area? The center is driven and the two side shafts are idlers? So the material fed moves the two lower side rolls? Usually see one larger diameter 'anvil' wheel and a smaller hammer wheel in English wheeling machines? Very nice design - was the capacity 10ga? (asking because of nibbler capacity)

Thanks for the photos- when did you paint the frames/longs? Was the entire boat welded then blasted, primed and painted? OR.... did you clean and primer the frames during the build? I've only built one steel boat with this method, done it a few times in aluminum so I was curious about cleaning under/inside/among all the framing niches, nooks and corners as I found that a major pain in the stern!

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

slug
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Re: Priming steel hulls.....WARNING!

Postby slug » Sun Jul 03, 2016 4:04 am

Kevin; Hull was radius chine, and recommended process was to use multi diagonal strips to accomplish this. Of course, I had to try for an upgrade.
Incidentally, there was less than gallon of filler in the finished hull, with most of it in the cockpit area, which "oil_canned" quite a bit.

Panels were fully formed and trimmed in position. The flat(unformed) bottom and side panels were placed first.

The two side rollers on the machine were adjustable up and down, and were raised to add pressure and form to the panels and the bar stock. This simple tool (once built) was great for forming the longitudinals and the interior frames that were added after the temporary heavy angle frames were removed.
The concept of frameless construction, was actually developed by the fellow who commissioned Brewer to design the Murray 33 (whom I met to advise me on construction procedures and lived and built near by). Brewer of course took full credit for this "modern concept". I found Brewer to be very egotistical and not very useful for practical advise. (his advise for rubrails was to weld angle iron to the hull and bolt wood to it, with no consideration how to grind welds smooth, sandblast, and finish! And 8 years after I bought my plans and advised him of a 1 1/4" mistake in one of the offsets, the error was still there for an other builder!)
All panels were cold rolled, the interior framing was blasted after hull was plated, epoxy primed and spray foamed. A hell of a mess to clean up but worth it.
Boat has been sailed over to Ireland and has been sailing over in Europe for the past 12 years and still doesn't look like a steel boat! My goal when building it.

Doug

Kevin Morin
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Re: Priming steel hulls.....WARNING!

Postby Kevin Morin » Sun Jul 03, 2016 4:17 pm

Doug, sure is a nicely done hull. If I got the drift (?) the main frames were like station molds - to shape the longs and get the hull plating on fair to the form of the hull? Then they were removed and smaller section framing was put in so the final depth of the hull's ring frames is much less than it took to pull her plating tight and true?

That evidently goes by 'frame-less' construction and the designer claims the idea even if he didn't evolve the concept and originate the method of construction? Some folks do get proud of accomplishments they've mainly inherited (!) One local builder in our area worked for me for a couple years- went out on his own with my drawings and take-off dim.'s then advertised he had a 'new' design of skiff! It was time anyway so I did re-design a few new hulls; but not before people told me that I'd copied this employee's work!!

Neat forming machine, if you have any record of more photos? it would be worth the time and space to talk about it- IMO? Show maybe some plate forming- even if only cylindrical and not curved both ways? All depends on your archive of photos and time to post- thanks,

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

slug
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Re: Priming steel hulls.....WARNING!

Postby slug » Sun Jul 03, 2016 4:48 pm

Kevin; Yes, the angle frames were temporary, and as they were removed interior frames were added at locations to fasten cabinetry and bulkheads. The idea of this type of construction (monocoque?) is that the shape of the hull gives it its strength and it certainly gives a nice clean interior to work with.
The roller is quite simple really (Dan Hennis could have used one for his longitudinals) and was built mostly from found materials. The only expense was getting the rollers machined. The rollers for forming the flat bar were my addition to the original plans, and worked well on the 1/4 x 2" steel frame sections we rolled for the radius chine. We were bending a fairly tight radius.

Incidentally, I recently bought my second "suitcase" welder, a Thermal arc 95S, for tig welding the stainless pieces on the Gentry. It is an inverter style 120 volt and I'm really impressed with it. At $500 it was in my budget area, although I would have liked a heavier machine, but it will do the smaller jobs I need. It will also stick up to 1/4" apparently, but I have a 180 MIG.

Doug


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