Rebuild, with Corrosion Spots

[Katoh]

Hi welder
Yes I will vacuum and pressure test the tank, once I have that done as a bit of added security I plan to line the tank with some POR15 tank sealer, or equivalent.
Hi Kevin
The photos are a bit alluding, now I can see why. the discoloration is actually a waxy substance, a mixture of water and fuel oil, I believe. When the boat was on the trailer I corked the two holes under the hull and filled it with a mixture of OMO and warm water, let it sit for a while and then rinsed it out , it removed all that waxy slime and the alloy plate became all the same color. I have put my hand in there and the plates feel smooth from the inside, and there is no indication of pitting, but definitely I'm no expert on the matter. With A quick inspection of the hull now while on its side I have found another 2 points of corrosion both are not through, and extremely small approx 1/8" dia so all in all 5 spots to fix. When I cut the inspection holes the hull, it had free water in it , appeared to be mixed with oil and grime from the motor well. and it always stayed at the one level due to the one hole in the hull.
I definitely need to clean the inside of the hull there's so much dirt and grime in there and the acid wash sounds like just the trick.
A question for you Kevin , How far past the hole would you replace? I was going to drill the holes out to 3/4" and make a special plug out of 10mm stock on the cnc, like repairing a dry wall hole. Or would you cut a square hole for ease of welding it back in? Please remember I have only access to one hole through the inside floor.
While stripping the boat I found so many loose wires, shorts, and the lights were all neg to the hull, I assume this to be the cause of the problem.
Katoh

[kmorin]

Katoh, oil in the bilge, odd as it sounds is a corrosion preventative and is very helpful to keep pitting and internal corrosion at bay. The petroleum is a huge source of both oxygen allowing the metal to keep and oxide AND just as important as barrier to acidic contact.

Bilge water that stands become anaerobic and therefore acid but the water is kept from the metal by a film coating so the 'dirt' if its oil is a blessing.

I'd use a solvent first, to wash it out, Stoddard solvent is not very flammable but would work well, if you can drain the hull. Then I'd use an 'ketone' like MEK, Acetone, or some other highly volatile solvent to clean the Stoddard residue, then I'd rinse with acid and finally flush with half the ocean to rinse. Getting the acid in and sloshed around will be a challenge but as you and your mates are rolling boats around it may not be much challenge for you?

The outside pits are likely stray current points, where the paint lifted and a pit began in the 'protected' space below the film and with the added bonus of some electrons flowing into the water.

Now for a method of installing hull repair patches from the outside without pulling the deck. I've done this on lots of boats but it wasn't my first rodeo so I'm not saying it will be the answer for you. After picking an area outside the corroded patch of completely clean and fully intact hull, I'd say that was the minimum hull patch size.

however, lots of guys would rather weld a three or four inch weld over a 2" weld especially with MIG. So patches' sizes are a whole discussion that would have lots of different points of view, I've done them from 1/2 the bottom down to welding up dime sized pits (more than 1700 in one 30' hull) so here is a method exploring the idea using a 4" cut out.


first I cut out the area that is involved, these sketches show the idea of a patch from the outside only, The idea is to work from the outside but have a fully integrated repair.


by working in halves the backer or weld backing plate can be installed from outside without taking the deck off. BUT..... the effort to clean inside the area where the backer will lap the original hull plate is not a trivial job.


here both backer pieces are installed and tacked, but the 'handle' of the second piece is not shown. I tack a small bar onto the outside of the second half of the backer plate to use threading the plate into the opening and holding it to tack.

Also I usually bevel the two inner edges of the backer so I can weld that from the outside in one pass, but I use TIG for this and many welders do have some trouble doing TIG overhead under a boat.


Kind of a back view with the backer plate halves translucent to make my point about the internal overlapping sides which will be a full back up to the weld groove allowing a very hot, full depth pass in a 1/4" bottom.

thinner hulls don't need as much gap in the weld groove and the back up plate can just match the hull plate.



Some welders prefer a beveled gap, some different set ups but I'm just showing a full width and depth square groove that will work fine if the welder is experienced enough to handle this type of prep overhead. If not, then the joint I show should be modified to accommodate the welding method and the welder. That said, a full bevel would not allow a full depth root face exposure!

By using a full depth (square) groove the fusion at the bottom of the weld is enough to back weld the plate inside the hull and pick up 80-90% of the hull at the same time. This is not the only way to weld this, so I'd like you to be clear that I'm showing an example as opposed to telling you how exactly to do this work.



When a patch like this is done, if it was cleaned well before and the welds are done correctly the hull is fully intact as original. The blue plate behind the patch is shown expanded to the outside edges of the patch so that I could make that sketch without having to confuse us all with a translucent hull panel to see that back plate set.

Cheers,
Kevin Morin

[Katoh]

Kevin
Again you have placed the most detailed and comprehensive post, You are the man!
From what you have described and drawn was nearly exactly what I have been thinking of doing. The only difference instead of using 3 plates I would have one plate double as thick as the bottom plate just milled to that shape, sounds confusing but we would end up exactly at the same point. Magnificent I'm so bloody happy now!
I think your right too about the oil and sludge, maybe saved me a lot of heartache and work, its thick in there and its everywhere.
I am going to patch all those holes with the boat as is and rebuild the trailer. Then once back on the trailer give the bilge and the inner hull a really good clean out. Yep a bit of man power a case of beer and a BBQ, we rock and roll any boat.
One thing the boat does not have any drainage bungs in the motor well or bilge, there is not enough room to install them on the transom, I'm thinking of welding in two, through hull bungs at the front of the bilge that would put them approx a meter forward of the transom, at least I could clean out the bilge every now and then, and spay down the motor after every trip to rinse any salt away. I was looking at these http://cgi.ebay.com.au/ws/eBayISAPI.dll ... K:MEWAX:IT welded from in to out, so the plugs are installed from inside the boat and they would sit flush with the hull on the outside.
Thanks Muchly
Katoh

[Katoh]

Colleges
Its been a while since my last post , but its been a while since I have done anything. External and Internal works, always seem to get in the way of a good project.
Well since last time I have totally stripped the trailer and have had it re-hot dipped galvanised, its still in a hundred pieces, I need to make up some bushings for the rollers, so went and bought a metal lathe. But now just a manual lathe seems like a waste so I am converting that to CNC, WHEN WILL THIS MADNESS END!
I have milled what I call my boat band-aids out of 10mm plate they are to be fitted to a 50 x 50mm hole (2" x 2"), I had 6 holes or patches so I made 6 band-aids.
I made an overlay template out of perspex to cut the hull to exactly work with my band-aids, and all worked well. I found the the hull is foamed in from about 450mm 1.5' up from the keel line on either side.

[goatram]

they Look good
Get to town and finish it and stay the course

[Katoh]

G'Day All
Just got asked by another member were my location is, for everyone's information the A.C.T stands for Australian Capital Territory, Were about 150km due west of some of the best game fishing grounds on the Australian East coast, We are actually the closest point on the Australian mainland to reach the continental shelf, which is Narooma. it is around 2hours drive from my place. At little further north is one of the only places in the world were you can catch Marlin from the rocks, that's the headland at Jervis Bay, My parents have a house in the middle of the two at Batemans bay, were once I finish with the Tub will become its new home, from there its only a 2km tow to the ramp and 20Nm to the shelf.
Thanks for the Question!
Katoh

[Katoh]

For those who are following this rebuild.
School holidays here in Oz, and I have got my 3 children home with me, a little time off or you could say a tag team with mum, we each take turns week by week. While there home nothing like a bit of Slave Sorry that should read voluntary labour. Some wet and dry and a lot of sanding to prepare the hull bottom for a re-coat. While looking over the hull I noticed a bubble in the paint that didn't quite match the others, a quick pick with a scraper and "SHITE" another bloody hole! So I decided to change the pump on the pressure washer from 2200psi to 3500psi. Quickly went over the hull and it blew this hole straight through, but couldn't find any others.
I plan tomorrow to go over the whole hull with a sharp scraper first then high pressure blast again. Finding this 7th hole has started to create doubts in my mind regarding hull integrity, or maybe it was just a spot that I missed. The plan is to weld this Saturday, Once welded I will re-spray with epoxy paint, then concentrate on getting the trailer back together to right the boat again.
Katoh

[goatram]

Good Plan. Be aggressive with the pressure washer now rather than saying "I wish Idida that Earlier"
Your patches are works of art

[Katoh]

Goatram
I am absolutely flattered , I have never had my work describe as works of art! If there is something I can do for you please ask, I'm sure I can help.
I have to make another boat band-aid, I will take a photo and post it being cut, its very interesting.
Well tomorrow Ill get my children out there sanding away , I'm determined if there is another hole we we find it. Tonight I have them helping me make Beer, boy its a hard life!
Cheers
Katoh

[Katoh]

G'Day Colleagues
Today should have been the day when I finely ended up with a watertight hull, but as things go and with the help of Murphy's Law, things did not go quite right. With the help of my children we sanded the bottom the hull with wet and dry paper scraped any loose paint and dug into anything that looked suspicious. Two complete run overs with high pressure water 3500psi through turbo head showed quite a lot. I have still only ended up with the 7 holes but found some through hull poultice corrosion right at the weld joint on the transom. No big deal, a quick scrape and a full weld will fix them up and some minor like pinholes can be easily drilled and filled. With everything ready a quick test on some scrap alloy to make sure the welders working and what would you now, my wire feed controller decided to play hard-ball, so nothing got done and wont get done till I fix the bloody welder. I have two welders but the other could not quite handle the 5mm plate, not enough grunt.
Have a look at the photo, its the making one of my boat band-aids being machined. This is a home-made CNC router, draw it on computer hit the button and off it go's. The plumbing pipes on either side of the motor are connected into one were they go to a dust extractor. saves all the dust and particals flying around the room. I am building a cnc lathe at the moment need to make some trailer and engine parts.

[goatram]

Dang! No wonder they look like pieces of art. A Home Made CNC Router. Cheater
I Have to get out the old Craftsman 7 1/4" Circular Saw "1967 Vintage" to cut mine out then use the die grinders to smooth the edges down.

[welder]

Katoh, Great post, keep them coming .
How far are you from the town of 1770 ? Pete Boyd is headed there soon for a get together .

[Katoh]

Hi Goatram
I dont consider using a CNC as cheating, only because I have one!
I actually have all the plans drawn for a 24' inboard, ready to be machined. It will come out like a big Meccano set. That's frames stringers, bottom and top plates the lot. I might even go ahead and build after this one is finished.
I have made a 1:7 ply model to see how it looks and goes together, Ill post a pic.
Hi Welder
I haven't heard of the the town 1770? On a Map I am about 20min south of Canberra in the Fadden Hills. By all means If a Member is coming down my way there welcome to drop in, Ill even shout them a Beer or two even 3 ect.. I just looked it up and I am around 1000miles due south. But I must say lovely part of the world up there, and some magnificent fishing as well.
Cheers
Katoh

[welder]

Katoh, member peterbo3 is in Brisbane QL and said it's about a 700 mile drive for him to get there towing his boat. It looks like a VERY nice place to fish IF the weather is right.

And it's the 1st time I have ever heard of a town that has a number for a name.

[Katoh]

Welder
I did a quick google, it is approx 800miles from Canberra to Brisbane and 200miles from Brisbane to 1770 or closest town Gladstone. If he is going there now through our winter, he is at the best time to be there. It is warm not overly hot and dry.
you dont want to be there in the summer, its hot, muggy and wet. If I had my way I would live up there in the winter and down here in the summer. I think the Humpback whales are just calving up there now, or about too. lots of around Hervey Bay were he will be but lots of big "whites" as well.
Is Pete going anywhere else?
Half his luck, hope he has a good trip.
Katoh

[welder]

Pete is here in the States right now , I guess that is a 700 mile round trip [ Then there is those Kilometers things] any way he is heading there in about 2 months .

I will be down your way one of these days with another forum member or 3.

[Katoh]

My Wife is actually hassling me to go to the states, her sister lives in San Diego. I would love to come over, but my children are still young, and the thought of lugging them half way across the world does not thrill me at all. Actually it will probably push me to the point of insanity.
My offer stands for a beer, and you never now if its the right time of year a fishing trip after some YFT or a marlin would also be on the cards, if I ever manage to finish this boat.
Katoh

[Katoh]

Gentlemen
I thought I would side track from the rebuild to show a couple of photos of what was meant to be before I rescued the old girl girl Im rebuilding now.

model1.JPG (32.63 KiB) Viewed 9221 times

model2.JPG (33.85 KiB) Viewed 9221 times

That is a 7.2m hull with 2.5m beam inboard, with delta keel. It is an exact 1:7 model of what I was about to start building, before restoring. Maybe one day when I have a little less to do I might have a go again.

Back to the Rebuild, well its being raining every time I have a chance to do anything with the hull, that bloody Murphy and his law are calling all the shots at the moment. An interesting thing is to go looking for galvanised U-Bolts to replace the ones on the trailer, was a near impossible task. Then when I found them at a price of nearly $5.00 each! well they can keep them. I ended up purchasing flat bar thickness of the bolt and 2.5x as wide, drilled two bolts in them and welded on the heads, Ill take the lot to get hot dipped, and more than likely save a few dollars as well. Still a long way to go, and until I get to the turning point, were I start assembling rather than dismantling its hard to see anything being done.

Katoh

[goatram]

Big Projects take time. Your prize will be your boat floating two days after you splash her.

[gilmarlin]

Thank you for your detailed description of how to patch and weld a boat hull from the outside, I will be using this information to repair my 19' Gregor. I discovered similar problems this season after taking the boat out for the first time in a long while. I replaced the trailer bunks with pressure treated wood about 3 years ago and since then have developed about 3 1/4 in. size holes at the front and back of each 2x4 where the boat seems to rest with the most pressure. I have also had issues with pin holes appearing in the transom since I bought the boat new, thanks to the dealer who wired some of the accessories to the hull, but I have eliminated them and have installed both a battery selector and a switch to the negative side of the battery which eliminates all current flow to the boat while it sits on the trailer. I think 2 switches is the best thing you can do for a boat that is on a trailer 90% of the time. Unfortunately, it took a couple of years to realize all this corrosion was going on and correct the problem. I have cleaned and patched the leaks temporarily with some marine sealant and plan on doing a proper repair after fishing season. As far as the transom goes, I will be pulling the motor this winter and doing a major inspection, possibly replacing the outer skin or fabricating a motor extension bracket. I have to decide first if it is worth the time and trouble or if I should just retire the hull to Baja and keep gooping the holes...

[Katoh]

gilmarlin
Good to see my experience's helping someone else, If I were you I wouldn't goop the holes as you put it, depending on the size of the hole most of them can be be just welded up. Use a piece of stainless on a handle so you can hold it from the rear end and just fill in the hole from the front, works a treat, and anything up to a 1/2 hole. Once you get bigger than that use boat bandiads, or Kevin's description nearly the same thing. Just make sure you use 5356 filler wire and you wont have a drama, plus it pays of in confidence to do a good job.
If you can post a pic of your holes I would be interested in having a look and comparing them to mine.
Just going back to the pinholes, I think you should drill them through with 1/8 - 1/4" bit and then fill them in, again using a piece of stainless as a backing to weld up the hole.

If weather and that Murphy fella are kind, I may have a sealed hull by Monday, fingers crossed on this one.

Katoh

[Katoh]

G'Day Gentlemen
Just a quick update, on where I am at. I have decided to sell the boat as scrap and buy a glass boat, (only joking).
What I really have decided is to fully strip the bottom plates of all the paint, bring the hull back to bare aluminium.
I am seriously looking into purchasing an ultrasonic thickness meter, refer http://www.ebay.com.au/itm/330610542027 ... 1438.l2649 to scan the entire bottom of the hull. I have come to the conclusion that its off the trailer and on its side, must be the perfect opportunity to do this, I really don't want to go back to were I am now with it say in years time after finding I missed a hole.
So the next couple of weeks look like spare time being spent with a roller, a scraper and a tin of paint stripper.
If any of you have experience or have used one of those thickness meters I would like to here your experience or thoughts on them.

[goatram]

We have done it on Aircraft Skin. to do it right you need to make a grid so you ensure you cover the whole bottom. We used 1" squares for the grid. Lots of Markers and a long Stick to make the lines. find a thin spot make it in red. That would be the only way you could ensure 100% coverage of the Hull. One end to the other.

[Katoh]

goatram
When you did the aircraft, was it a painted surface or bare metal?
How well do those ultrasonic meters work, I have never used one but just came up with the idea, thought about using my stud finder but that works in reverse. But for $140 odd dollars might be good insurance and peace of mind if it works.

[goatram]

We had to be trained to do it. I never was . I would Prep the area to bare metal, If it was a big area I would make the grid and sign it up for inspection then document the numbers for the Engineers to sign off good or bad then do a cut out repair if bad.