Implications of pitting repair and future prevention

General boating discussion
skypoke
Posts: 51
Joined: Sun Mar 23, 2008 8:34 am
Location: Port Aransas Tx

Implications of pitting repair and future prevention

#1

Post by skypoke »

Ok, so a 8.5 meter powercat I built with a partner was stored improperly by now ex partner, and I'm needing to do some repairs. It has some pitting on the 5MM bottom plates, that appear to be associated with some bilge pumps located in same area. It was left holding fresh water on the trailer, bilge pumps on auto. That, and a couple other mistakes....mill scale left on plate, no bonding from negative to hull added up. I'm now on to repairs.

The pits are small, but run varying depths into the plate. Chasing the corrosion with a 1/2" drill bit typically gets clean metal. I had a buddy come over and tig up some of the drilled pits, he has made the comment that he can "float out" any corrosion missed by clean up. Not sure exactly what to think about that.

But it appears that it will be possible to get "all" of these spots out and filled with tig. I started the cleanup process with scotchbrite abrasives to remove mill scale, followed by acid wash, hard scrubbing, neutralization, and floods of water. Approximately 50% of the pits have been addressed.

As an experiment, on a very small area with a few pits I carefully applied Boeshield T-9 (known from aviation days) and went back a few hours later. I noted, as I drilled out these pits, that what would normally be small areas of white corrosion were now black. Based on this, and observing how totally neglected alloy boats with oily bilges never seem to show corrosion, I have decided after repairs are complete, to keep bilge areas treated with T-9 or, alternatively and possibly in addition, LPS-3. Both these products form a waxy film. Both are self healing and creep into hidden spaces. What are the thoughts on this plan? I don't see a problem with "sheen on the water" after this stuff sets up.

But my bigger question is structural implications of all these tig spots. Has anyone ever heard of failures associated with this type of repair? I do not notice any warping or apparent stress in areas of the welds...but that's a fair amount of heat being applied.

I had considered replating but hard to see us pulling that off. I remember the force it took to fit up those bottom plates....and expect that removing good size sections of them will result in some severe distortion to deal with.

Would greatly appreciate you guys take on this plan of action. Thanks, Chuck
Texian, born and bred.

kmorin
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Location: Kenai, Alaska

Re: Implications of pitting repair and future prevention

#2

Post by kmorin »

skypoke, don't see any problems with TIG patches as long as they're coin sized and not palm of hand sized? If larger then some added structural may be needed to keep the hull fair- but no problems from floating out some pits.
Drilling out pits is easiest using a small pilot bit say 3/16" to 1/8" depth; and then a larger dia. bit -say 3/8" to a 1/16" dept or just a chamfer around the original hole. This allows the TIG arc to get deeper into the hull's parent metal with less amperage/wattage/heat/power and therefore a smaller overall weld volume than if the arc's puddle is the sole source of the molten crater? a conic router bit works well too- but getting a router base into some areas in order to control the depth isn't always possible? A counter sink bit on a the top of the original pit drilled site will do the same job or giving the initial TIG arc a better chance to reach down into the cleaned site with less amperage.

I typically start next to the fill/excavated site and get the arc & puddle stable then immediately 'walk over the edge' and reach down into the crater to try to get the bottom molten in the shortest period of time, watching for sag. Then i roll/circle the torch and try to begin closing upward as fast as the weld will fill & chill. Works.

If you have very deep pits - take a 4" x 4" square of 1/4" or heavier aluminum and hold it against the underside of the hull with a 'cripple stick' or crutch propped under the hull and on the ground/trailer. This plate will help keep a 3/4 dia pit site from sagging down from the amount of welding needed to fill that after excavating the corrosion site.

Etching the entire hull isn't bad practice- then making sure that there are NO copper alloy metals in the hardware (hose ends are notorious) and fitting out? Wiring is all covered/shrink-wrapped and not in the path of any drips of condensate?

BoSheild is sort of superseded ACF 15 as I understand the chemical issues but definitely won't hurt the boat's hull anyway that is known and published?

Electrical, both AC and DC bonding is pretty important if the hull is wetted, even rained on- regularly? Either system's bond gives a path for stray current to the 'zincs'/anodes and will reduce interior corrosion if its present from stray current?

All sounds like the accepted way to go about repairing this type of hull damage to me.

Cheers,
Kevin Morin
Kenai, AK
kmorin

skypoke
Posts: 51
Joined: Sun Mar 23, 2008 8:34 am
Location: Port Aransas Tx

Re: Implications of pitting repair and future prevention

#3

Post by skypoke »

Okay, I'm officially heaving a large sigh of relief. Yes, all repairs will be coin sized at most, no large areas of aggressive corrosion. I'm also going to revisit the wiring scheme and most likely relocate it, going to go into plastic conduit rigid and flex with sealtite terminations as much as possible. Negatives will be well bonded to hull. Basically, every trick in the book, this boat has served well for 15 years, our last outing we had a triple Wahoo hookup, landed all 3 on braid no less. This boat raises fish and makes unforgettable memories, I want it to last!

My everlasting thanks to Kevin Morin. Your willingness to share your hard won knowledge is without peer.
Texian, born and bred.

kmorin
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Re: Implications of pitting repair and future prevention

#4

Post by kmorin »

skypoke you're welcome to my list of errors! hard learned lessons indeed- some of them.

re: new wiring, I've become convinced that using Starboard- a plastic sheet in about 1/2" thickness as the base for electrical panels is the best practice- bench built distribution boards, with all the relays, terminal strips and panel point to point wiring on these plastic sheets eliminates any DC Neg to Dc Plus errors.

Also it makes 90% of the panel fab. work off boat- on the shop bench- so you 'just' drop in the panel- and then do the field run terminations- much less work than building the entire panel on a hull interior metal surface in place- as I've seen done so many times!!

ONLY ONE DC neg and ONE AC neg/neutral should be bonded and only in one place on the hull. So the entire DC Neg Bus; one lead: and the entire AC Neutral/ground buss; one lead to the DC location.

I like to use the battery NEG as a short sweet bond wire- I use a large flexible welding lead and w silver soldered end lugs and silver plated too. Then use the glue-lined, cable splice, shrink to cover all but the contact surface and that is bolted to a sacrificial piece of aluminum welded onto a large hull structural element.

In case it had escaped your notice Sky? we do support pictures here! They would be very welcome- not necessarily the pics of the damage or repairs- but surely a few shots of the boat on the hard, on the fish- we don't care- we just like to look at welded aluminum boats!

Cheers,
Kevin Morin
Kenai, AK
kmorin

skypoke
Posts: 51
Joined: Sun Mar 23, 2008 8:34 am
Location: Port Aransas Tx

Re: Implications of pitting repair and future prevention

#5

Post by skypoke »

But of course. Dredged from the garbage can that is my photo organization on computer, here's a few shots. That's my brother reacting to the first Wahoo he's ever seen. My son is on gaff, he's been fishing in Alaska, charter and trolling for 15 years now.

The young guy with a coffee cup is me on first run of boat....happy day. That was in 2004.

I'll see if I can find some more pertinent shots of the boat and put em up.

Boat shots 2008 045.jpg
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Cat running shots 017 (Medium).jpg (91.77 KiB) Viewed 1138 times
Texian, born and bred.

kmorin
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Re: Implications of pitting repair and future prevention

#6

Post by kmorin »

Chuck, I was certain the young, brawny, hoss with the gaff was you! (?) Nice build, you and a former partner built her? I think i vaguely recall something from you guys a few years past? but not very clear in my memory.

She looks nice- too many cats don't have enough rake in their bow stems and that gives them an unnaturally boxy look overall. You can always extend the cabin top brow and that little trim dodger forward (?) and get what I'd say was bit more 'line to the house'.

Looking forward to seeing more, and hearing more about her, and repairs too.

Thanks for posting
Cheers,
Kevin Morin
Kenai, AK
kmorin

skypoke
Posts: 51
Joined: Sun Mar 23, 2008 8:34 am
Location: Port Aransas Tx

Re: Implications of pitting repair and future prevention

#7

Post by skypoke »

I do believe we corresponded a time or 2, probably on THT? Had a lot of folks following the construction process, for better or worse. Looking back I would have done some things differently....I had been convinced that continuous weld beads needed to be a few inches long, max, which we did but too many starts and stops. But the proof of the pudding is in the eating, this cat has spent its life in the short period waves of the Gulf of Mexico, run hard, typical 50 mile headsea run out, my 20 year old son on the helm cranking the stereo, heavy on the throttles, old folks in bean bags at the transom enjoying coffee or a beer as appropriate. Had a total of one weld crack, and that was a long that really had more gap between it and the plate than it should have. Nobody will look at the boat and think Kvichiack built it, but it is very, very fair.

Roger Hill in NZ designed it, he was a real pleasure to work with. Our own Chris Tucker had a hand in it as well. When we picked up the parts in Lousiana and started assembling it, I was absolutely astounded with the accuracy...within 1 mm typically. I was less than pleased with the stress that plasma cutting put into the parts. I decided I wanted these capabilities so after the boat was "done" I built a flat bed CNC router carrying a 4KW spindle with cut capabilities of 6' X 20'. Still have it, just need to build a new shop to put it in. And when I say "built", I mean built from raw steel and components, assembled power supplies, set up software, figured out autozeroing, lots to it but just an amazing device.

Roger produced a very stylish design that avoids the slab sided box look of so many alloy cats. You pay for that stylishness, there were a lot of parts compared to many others, and no chine extrusion foolishness....all cut from plate. I believe I counted the total full length longitudinal welds going all the way around the boat, and IIRC, somewhere around 40. Most of those are seal welds, too. The boat itself is of conventional construction with two watertight bulks ea sponson, thwartship ring frames, longitudinals around 10" or so spacing. It's designed to one of the society standards for NZ offshore craft.

So, you look back on life, and for me it's the family I raised, things I built. Built every house we ever lived in, rebuilt an airplane, more project cars than you can count, but this boat really takes the cake. Our first trip out, after reeling in two monster cobia, a wahoo, couple amberjack, limits of snapper, sun shining and the afterglow of a great day fishing, I turned to my partner and said, "well, we just paid for the boat." He just grinned.
Texian, born and bred.

kmorin
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Re: Implications of pitting repair and future prevention

#8

Post by kmorin »

Chuck,
thanks for the post, and memories of 'how you got there' - I'm not sure I can think of many events, looking back, that approach standing on the deck of boat you designed and built, feeling her move under your legs and experiencing the enjoyment of your ideas come to life from your own hands? I wish more guys would just 'go for it' and take the risk of building for themselves, but it seems there aren't that many who're very interested in the build process?

All but of dozen, of the hundreds of hulls I've done from 2' (that is two feet) to 52', were my designs, but only very few were cut by NC as that had yet to become economic when I quit building full time in the 90's. When I wanted to build again, since, I've priced the cut fees and found a way to make very decent wages using hand layout and hand power tool cutting.

In fact the 34'er we're doing now, one-off, just didn't justify the hours to do the NC files, in the couple of days work it would have taken to generate tool paths, I just did the layout by hand and my building partner cut the shapes. We did take longer to tack them up! as we're both in the geezer boatbuilding league, but she's coming along nicely. [ the boat can be seen at uTube : "Jahrig Aluminum Boat" so I haven't done any thread on her yet. If you look at the videos you'll notice her hull is unique; so we'll see how this design idea pans out?]

Thanks again for the posts, looking forward to seeing more of your cat's pics inside and out. Fishing, running, and on the hard- if she spends anytime out of the water pictures are welcomed.

Cheers,
Kevin Morin
Kenai, AK
kmorin

skypoke
Posts: 51
Joined: Sun Mar 23, 2008 8:34 am
Location: Port Aransas Tx

Re: Implications of pitting repair and future prevention

#9

Post by skypoke »

Kevin that's a pretty dang significant geezer project alright! Looking forward to seeing it splashed and running. What is its intended use? Hope you open up a thread here on it.

Yeah, lots of time it's easier to just grab the saw and cut rather than going through the cad design process. Where it really shines, though is production work of course, or a job like mine where a skilled designer has developed the cut files. No way I'd have attempted to hand cut that project. I do think one good thing about the cad/cam process is that it opens up a skill for younger folks who haven't come up through the trades. Its getting pretty rare for kids to have as much adeptness with hand tools but some of em can take a cad program and run with it. Now if someone would just integrate AI with a welding robot. Interestingly enough, I noticed SpaceX is advertising for skilled welders trying to get their stainless steel spaceship to hold together. Wonder what process they are using?
Texian, born and bred.

kmorin
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Re: Implications of pitting repair and future prevention

#10

Post by kmorin »

Chuck,
two old guys can get some work done if they keep at it! We're thinking (not very seriously) about opening a new boat building company- we have a name but our Slogan Says it ALL! "We'll build your boat: If you have TIME!" Geezer Boat Builders.

The boat is a type that is used in SCentral AK primarily for recreational fishing. The boat type is an expanded version of the week-ender type of live aboard commonly seen in other markets- most often and likely more affordably made of some or another plastic resin composite goop hardened in a mold.

The plastique boats have a problem - not severe but present- in the waters of SC AK. Uncharted rocks, deadheads (logs floating end up in the water but submerged) and the insurance market plus financing facts of life.

In the Sound or Prince William the various charting software isn't (even today) 100% accurate regarding pinnacles or towering rocks, that are just a jagged point of granite just below the surface. Also - there is no real world means (perhaps forward looking, active running, sonar?) to spot 100% of the logs floating end up in these waters.

So, over time, many boats have experienced some impact at speed types of collisions that left a quarter million dollar boat, and some million dollar boats to limp to a port- there are all of three in the entire area- some a weeks run away at displacement speeds! to find repairs. Then.... that port doesn't have any really yacht level plastique layering repair facilities- so the insurance companies and therefore the banks.... are a bit shy of having layered plastic hulls on their books.

The welded metal boats have faired differently and are considered to be much more durable in an impact at speed with these underwater hazards of the primary, sheltered from the N.Pacific to some degree, and fish laden waters.

So a 30 some foot, welded aluminum planing hull, most of which are outboard powered, has become a 'type' in this market for recreational fishing and enjoying the Sound of Prince William.

This 34'er will be the Skipper/Builder's live aboard for his time in Prince William's Sound. Like most of these boats his will hold a pair of 350's and sleep 2 very comfortably, 4 if they're close acquaintances a 6 or a few more if they're family. Her tankage and size (34' x 10' x 8 deep at her bow) allow the boat to handle anything that PWS has to offer and still remain not only comfortable but safely so.

Hope this helps explain why she's being built? The market here usually asks for 750k or 3/4 mill for these big ladies' to float. I think the Skipper will save significantly over this cost- but that is only by building himself- using geezer calendar over a bank financed timing that most full time commercial builders would have to apply?

The premier builder in the State of Alaska is Bayweld, in Homer Alaska. Their designs, workmanship and longevity of use and sustained value in the marketplace are completely without peer. They build this class of boat, and my comparisons are to their market positions in regard my references above for cost, use, and typical power.

Cheers,
Kevin Morin
Kenai, AK
Last edited by kmorin on Mon Mar 16, 2020 12:15 pm, edited 1 time in total.
Reason: typo's
kmorin

skypoke
Posts: 51
Joined: Sun Mar 23, 2008 8:34 am
Location: Port Aransas Tx

Re: Implications of pitting repair and future prevention

#11

Post by skypoke »

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Texian, born and bred.

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