Riverjet takes vicious hit

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Riverjet takes vicious hit

#1

Post by dawgaholic »

Saw this on the meanchicken.net forum:

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That had to loosen a few fillings at the very least!
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Re: Riverjet takes vicious hit

#2

Post by S L Dave »

Ouch!! The amazing thing is that that massive accident is fixable in few days!
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Riverjet NEEDS a vicious hit

#3

Post by kmorin »

Boy that boat sure is built to a homely work standard! That 'thing' needs to take a vicious hit, it should be cut up for scrap!

Of course, it's good to hire the "physically challenged" as they need work too, but hiring them as welders many not be the best future for your boat building company!!

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Re: Riverjet takes vicious hit

#4

Post by dawgaholic »

By all means share what your experienced eyes are seeing. All I know is that you'd be swimming or at least wet after that impact.
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Re: Riverjet takes vicious hit

#5

Post by JETTYWOLF »

kmorin, can spot a rookie weld from a mile away....and because of him, I've learned a bunch.

I'm guessing those welds?

They look nothing like the welds on my boat, I know that!
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Re: Riverjet takes vicious hit

#6

Post by dawgaholic »

JETTYWOLF wrote:kmorin, can spot a rookie weld from a mile away....and because of him, I've learned a bunch.

I'm guessing those welds?

They look nothing like the welds on my boat, I know that!
Now that you mention it I've seen more precision-like welds. But the damage is punctured hull plate and from watching some of those crazy people white water jet boating, suck a jagged piece of rock puncturing plate like that sorta adds a new and more deadly possibility I hadn't really considered.

Gonna go get me some knowledge so I can be quicker on the pickup so to speak. :thumbsup:
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Tearing Alloy Plate Hulls

#7

Post by kmorin »

dawg, many fresh water inboard sleds are built of 5052 alloy which is softer, lower tensile (tears more easily) and is cheaper than 5086 or 5083 'saltwater' aluminum. 5052 will work fine in salt water but its not quite as corrosion resistant as 5086 or 5083 (the latter most common Down Under) but all aluminum will 'tear' when you reach the 'failure' yield point.

What isn't as obvious from the pictures (and might not be the case) is that aluminum welds that are uneven create as series of ragged edge notches or cold fusion points along the weld. This condition is very much present in the welds shown in the picture and they can contribute to tearing failure where better welds AND (or combined WITH) better alloys will 'bounce'.

What I'm discussing is the failure method of this collision impact tear. It appears the hull was moving in sliding turn ( I have no info on this- but that is what I'm inferring from the single photo) the sled was sliding at high speed to the port in a slipping turn and the rock was relatively sharp -not rounded very much.

[Quick note to everyone, salt water rocks are usually very rounded from all the time in waves, sand, surf but mountain river rocks may have been split by ice the previous year and be sharp]

Sharp isn't meant as in knife sharp its meant as in not rounded like a salt water rock where there is enough 'edge' for the entire wt or displacement of the hull PLUS the momentum of that moving hull to come to bear on a very small surface area. So if the tensile strength of the metal were say 35,000 psi (at failure) then the one ton boat moving at 40mph is a rough momentum of 50- 80 thousand pounds of potential force- if expressed on a 1 inch area. What makes this number higher or lower is the area of the immoveable object the boat hits- small area or sharp rock is higher where larger area or round rock is much lower impact force per unit area.

If the rock is rounded, say a foot round then the area of impact is 4 or 5 inches square or 15,-20,000 psi of impact at that point and the metal holds- it may well bend- but it holds. Next, if the rock had an area of impact of 3/8" x 3/8" or (0.365 x 0.365) or about 1/10th inch then the metal's failure strength could be reached and it would puncture or 'tear'.

OK lets complicate things a bit. What if the tensile strength of the weld lowered the metals' original tensile? Well welds to lower that figure in aluminum along a zone called the Heat Affected Zone or HAZ. Along this median boundary of the weld and the hull plates, the tensile is lowered say 20 -50% depending on the weld, speed, alloy of filler and size (cross section) of the welds.

Now.. lets really look closely, if the HAZ is not uniform along the welds' edges its because they are like a picket fence or notched because the welder didn't put the weld into the seam uniformly and that creates a ragged edge of HAZ and that ragged edge will not be uniformly degraded in tensile (tearing) strength, it will have weak spots and stronger spots all corresponding to the heat and cross section of the welds, and if the weld is not uniform in fusion line, that is the edges are not even- they imply the heat and weld cross section is not uniform.

If the HAZ is not uniform the metal's tensile zone is not uniform and therefore if such a hull were to hit a rock when.. it was:
#1 made of 5052
#2 poorly welded or inconsistently welded
#3 HAZ being ragged and not uniform

The tensile strength of the alloy would be subject to tearing beginning at the points of the weld with the worst case of weakening due to the conditions mentioned.

Now bringing all these factors together on the port chine of a poorly welded sled, perhaps in an area where a 6061 extrusion is welded (angle shown in photograph was likely 6061 T6 alloy) to a 5052 plate the weld joint is even weaker yet! And what if the welder used 4043 wire! with its high silicone content to make welding 'easier' instead of the correct alloy 5356?

I know that my take may be harsh for the builder of the boat, but the workmanship is not even acceptable for a JrHi shop class.

All welds should look uniform, the edges of the welds should smoothly fuse into the metal they are joining and the surface of the weld and adjoining metal should be relatively even and uniform, the boat shown was built by someone that was not well practiced.

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cheers
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Re: Riverjet takes vicious hit

#8

Post by JETTYWOLF »

- all I can say after that tutorial is......"W-O-W-Z-A"

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Re: Riverjet takes vicious hit

#9

Post by S L Dave »

Thanks Kevin! I don't think I have that depth of knowledge about anything!!! Another great post. :thumbsup:
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Re: Riverjet takes vicious hit

#10

Post by JETTYWOLF »

S L Dave wrote:Thanks Kevin! I don't think I have that depth of knowledge about anything!!! Another great post. :thumbsup:

:rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl:
thats really funny Dave.
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Re: Riverjet takes vicious hit

#11

Post by BroadCove »

Agreed, absolutely an excellent post and I learned alot. Thanks, kmorin!
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Re: Riverjet takes vicious hit

#12

Post by dawgaholic »

:beer: kmorin! Thank you for your tutorial. Gotta ask the experts if you want to know the answers. :thumbsup:
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Re: Riverjet takes vicious hit

#13

Post by kmorin »

When I got back to the mail I found some comments here and that made me look at the original post again. I think I skipped something and would like to point it out. We're all speculating on this sled hull but my speculation about the alloy went up to almost assure everyone its 5052.

If you look along the underside/inboard side of the lower angle, you'll notice a bend in the hull plate?
what I'm pointing out is a bend in the bottom panel inside or inboard of the weld that holds the angle as a chine flat. That radius tells a critically important story about this hull.

That was formed by a press brake, and the radius tells/shows/illustrates that the alloy was not 5086. 5086 alloy needs a 4T/R or four times the thickness radius to bend without stress cracks, but 5052 only take one thickness radius to bend. If we look at the tear the hull is either 0.187" -3/16" or 0.25" -1/4" so the radius of the bend in the softer 5052 is about right for the that alloy. But... if the alloy were 5086 the radius would be very rounded- and it's not.

The short tight radius can only happen in 5052 but what isn't obvious in the image AND in my post(s) is the fact that 5052 "strain hardens" along a bend. In fact all alloys strain harden or get tougher along bends. But what happens to 5052 when it hardens is it (this alloy) becomes more brittle; the tensile strength gets (effectively) lowered over the native 35,000 psi; minus the weld HAZ and; minus any degradation over the notches in those welds.

We could consider the strain hardening as a 'pre HAZ' where the metal has become changed from its original milled composition, when you weld on this bent/press braked area (as the angle mounted as a chine extension is shown) the welds will deteriorate the strained zone in 5052. This is not as prevalent in the 5086 or 5083 alloys and especially as they are welded with 5356 alloy fillers.

This hull tore out, or was ruptured and torn, because is was strain hardened, (by the press brake) then welded to a 60 series alloy and that weld may have been done with 4043 (silicone laden) welding wire- wrong alloy, wrong design, and combined all the factors seemed to have made for a 'weak' hull.

All that added together to tear the hull material, a Pacific would have a nasty scratch and nothing more. Not that you'd run an outboard powered skiff, with some V, in a mountain river but the Pacific hull wouldn't have ended up like this; it would have bounced.

[Full Disclosure: this hull's tearing absorbed most of the impact and save the lives of the occupants, a Pacific or other well built hull would have transmitted the shock and impact to the 'bags of jello' inside the hull and they would have suffered tremendously. People are the weak links in welded aluminum boats]

We're all learning about welded aluminum hulls, they didn't exist until the 1950's, really, and didn't become wide spread 'till the 80's or '90's (that would be in the last century) and everyone is still figuring out how to make them better, so those of us who have made countless mistakes building welded hulls (like me for example) are the first to see those errors when they're made by someone else who is still learning 'that lesson'.

Cheers,
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Re: Riverjet takes vicious hit

#14

Post by welder »

Kevins pictorial is AWESOME and that goes along with what I always told my welding students "If it looks good, it is good" If the proper filler rod is used along with Travel speed, Angle , Heat and skill you WILL have a BEAUTIFUL weld.
Those Stainless fittings look like a machine did them ,looks like someone has a turret and the corner T.I.G. on the SS is perty dang nice, the color tells the story.

Well done Kevin.
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Re: Riverjet takes vicious hit

#15

Post by JETTYWOLF »

What I saw, and BTW, I don't know squat, but either way, something seemed funny that the Rail/Chine whatever ya want to call it, was welded to the "bend" in the outboard side-bottom of the boat.

Being that it was bent as Kevin states, and then welded upon didn't look right to me. (which maybe means I'm learning?)
Which in the pic looks to have nothing to do with the tear (?) But that's what I spotted right away.

So your also saying that the wrong material, shouldn't have been bent in a brake (that degree), and then that same "weakened" area was then welded upon and not well, at that.

Good stuff, and Good pic.

(Better than that pic that was on THT years ago of a guy who drilled what looked like cement screws through the inside of the hull of his glass boat, and they went all the way thru the bottom.........like 20 of them. D-O-H :!: Now that was really funny)
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Re: Riverjet takes vicious hit

#16

Post by kmorin »

Welder, yes the fittings were done on a positioner and foot pedal to get the uniform feed welds, the SS is a water cooler box/tank for the TIG torch and the drill is 0.065" dia. tip drill for size reference the pulsed TIG weld was so small I had to put two pair of cheaters in the hood to even see the bead and the wire was 0.023" and was 'laid in the fillet' then welded over.

Jettywolf, what I was saying was that bending that particular alloy is OK, (by itself) but.... you have to take into account that it gets harder, the hardness means its a bit more brittle, not "tougher". So you're correct that the angle welded where it is - ain't the best building practice out there.

OK lets move to steel, the knife is hardened and takes a good edge but that hardening process makes the blade snap easier than a screw driver when you use it to pry something. The hardness is a trade-off, the metal is still strong but not in the same way. The screw driver won't hold and edge to save its life but it will pry for a long time and BEND nearly double before it snaps while the knife will take a great edge and hold it, but will snap sooner than the screw driver as a pry bar.

Back to the river sled with the torn bottom. By bending the 5052 alloy it becomes harder but that comes at the price of being more brittle- less malleable or less flexible without tearing. So in an impact the 5052 bend area will tear easier than the flat sheet out in the middle of the hull panel.

I'll agree that it can be a savings of welding to bend the chines when you have #1 softer metal, #2 a straight line at the chine and #3 the side-to-bottom angle is within the a few degrees of the bender/brake's capacity. So its not the worst deal afloat to bend, but when it is done the result is a harder but less malleable or flexible aluminum.

What I'd have done is to wrap the angle around the chine so the legs of the angle were 1-1/2" or so above and below the chine and the welds would have been in 'un-strained' sheet. Then I'd have welded the angle in short stitches to attach to the hull but not to create a continuous HAZ, and especially not a ragged edged HAZ!

Now this angle chine (above) was put on the outside, this is the angle that is welded just above the bend, and it makes some sense in a sled to put chines outward so they help create 'release' of the wake at the chine. I'm not complaining about that alone, but the location of the welds hurts rather than helps the whole show.

What was done here was the irregular weld, the alloy of the weld wire, the alloy of the angle, the bend area's hardening, AND all of that happening in the same 1/4" wide zone- that likely made this boat tear/peel open when it wouldn't have if the #1 the hull were 5086 alloy #2 the chine were welded with a 'cap' angle for rocks not an outside angle for rocks, #3 the welds were uniform and even, #4 the filler metal alloy were 5356 instead of 4043.

I'm speculating that all of these factors added together with a once in a million hit to a weakened spot just inside the angle and about 1/4" below the bend where the tear looks like it begins. This is exactly where the factors above would have contributed to a serious reduction in the original plate's tensile strength.

It will never happen to a Pacific, in fact I doubt you could get enough power on the stern of a Pacific to push it to the limits of the hull. Maybe if you had a half dozen 300's you could get a hundred and some miles and hour and put dents in one but that's all, they would bounce like a stone skipped over the water before you could hole one. Don't get me wrong, like dawgaholic mentions- you'd die in a collision that would puncture a Pacific, but the boat would hardly know it was bumped.

I built a set net skiff that was picked up in 80 mph wind storm and tumbled end over end (the owner saw it hit bow to stern for a 1/4 mile along the beach as it went out of sight) for 8 or 9 miles. The boat was recovered, by dragging it back to the owner's fish camp on its own bottom with a tractor, and fished for the remainder of that season and was sold at a profit at the end of that season and is still fishing (near as I know) 30 some years later. There were scratches at the bow and the stern and an engine was toast, but the boat was intact.

Welded aluminum is the toughest boat (not ship- boat) building material anywhere, that's one of the reasons I call it the "Miracle Metal".

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Re: Riverjet takes vicious hit

#17

Post by dawgaholic »

kmorin, thanks for putting this in terms easily understood. One wonders how you could know if such corner cutting was practiced and when before it was found out or some QC finally instituted,

With respect to construction methods, what characteristics separate the builders of heirloom quality forts vs. the sketchy ones?
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Re: Riverjet takes vicious hit

#18

Post by kmorin »

dawgaholic, some of the best indications of the longer lasting boat are the welds- they work as 'indicators' of quality at one level. If you look at a Pacific, a hull from Response Marine, a Munson, or many of the other longer term builders you'll see they have welds of high quality. Some companies have welders who make such fine welds they're easily 'art' quality- Pacific does.

The reason to look at this aspect is the cost of a good welder is not a wage. The company has to find 'em', train 'em, and hold 'em for long enough to get those great looking welds. That says the company is not some 'body mill' where they hire lower skilled people that are expected to be gone and replaced in a few months or a year. The better builders are planning to be around and their welders are a visible 'tip of the iceberg'. If the welds are poor, the investment in the people making them is low, therefore the builder is not as high quality as one that has invested in better welds.

If they work to keep good welding, that same company is working to keep good skills in other departments and trades too.

Another aspect that can 'tell' on a company is to read their spec sheets. What alloy is being used (?) the least expensive or the best they can get? Going even further, are they concerned with the various alloys in different capacities within their hulls? Munson Boats is so thorough they avoid all 60 series alloys in their below decks framing! People don't even know it but they have such super high standards they press form and shear their framing below decks- that's the type of high quality that will end up lasting a century.

Also design is a good indicator or the longer lasting boat. I know that metal boats can be made strong, tough and long lasting but still be homely and have poor lines. What I'm discussing is the quality of the boat's lines for the water it will handle. There are many production boats that have a bow (curvature and taper) about 1/3 the length of the hull then they come to a Master Section (max beam) and stay that way all the way aft to the transom.

This hull form is a sled, (from the parallel chines, keel and sheer - ie. a box or sled shape) and they can be well built and last a long time, but they indicate the builder is more interested in machine pressing and forming their boats than to build longer sweet lines that a pleasing to the eye. The sled hull will last as long as any hull, there is nothing weak about the boats if framed adequately, but they show the company is more a 'fabrication business' than a boat builder as the design shows no lines (to speak of) aft the master section.

I'm not saying a landing craft or other work boat has to have sweet lines to be functional, just that when you see a skiff that has been formed to a set of lines that have movement in all views (regardless of curvature) then you're looking at a boat that has more effort and that usually means the other quality choices were also made on the 'high side'.

There are many more quality indicators, and plenty of production builders will argue with my points listed, but one last item is the treatment of the metal surface after building. If the builder leaves the mill scale on, it says they're not interested in long(est) term quality, or worse, they're ignorant of the potential damage that small short cut can bring to an otherwise fine hull. If the builder etches the hull, regardless if it's coated for esthetics after the mill scale is removed, then again, you're dealing with a builder that is concerned with quality.

Last year I was invited by a friend of a brand new (West Coast well known Name Brand) boat to come look in his bilges at what he thought was corrosion! the boat was not a year out of the shop and there was corrosion in the bilge. The boat had not been etched and the mill scale and the deck wash/bilge water was acidic and the hull had some minor pitting. Later this past summer I was asked to look at a hull I'd done in the 1980's and since it was etched, is was as smooth and fair as a baby's stern. The old boat had hauled around 350,000 thousand pounds of salmon in the years since it was built (and etched before it left the shop) the new boat had seen a few halibut and some few salmon. The production builder ( a big name Co. on the West Coast) didn't 'believe' in etching the boat inside?

Also there are one-off builders and there are yards that build full time. The yards that have been around, and are still selling boats are almost always going to deliver good or better quality, the real question (like the homemade river boat in the lead of this thread) is what kind of boat do you get from a one off or small shop builder? In that question just go look at the boats, and decide if the quality 'feel' is what you want to accept?

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Re: Riverjet takes vicious hit

#19

Post by goatram »

Keven
What do you mean by the term "Etched"? Alodine? or Primer"

I have one of those pretty surface Welded boats. It has the laid down stack of dimes that look cool but penetration at times was minimal. My boat was returned to the Factory for cracking of the Transom and Swim Step Back in 2005. My front cutout was another area that looked pretty but was cracking at the 90* joins.

Aluminum Welding does take time to learn, the pay is not always great, Conditions are at times hot and hazardous to ones heath, the economy's ups and downs push some of on to greener pastures. Here in the PNW the lure of Boeing's pay scales attracts many to the warm comfort of a Union Job with retirement.

Keven As always your post are a pleasure and informative. Thank-you for the time you take to explain yourself and teaching us in your essays.
To you Sir!
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Re: Riverjet takes vicious hit

#20

Post by kmorin »

goatram,
when aluminum is 'milled' into sheet that is the 50 series alloy plates and sheet material (generally the industry calls 3/16" or 0.187" thick material the break between plate 1/4" and thinner 0.160" a sheet some folks make that call at 0.125" 1/8") they are surface treated by the rolls with a coating that is shiny in the form of an oxide film

Now all aluminum will form an oxide in a few second by combining with oxygen to form a 0.002 thick layer or film we can't see well, and that is not the 'mill scale' or shiny sheet coating I'm discussing although chemically they are similar. The chrome looking coating on the mill sheet goods is heavier and helps the surface release from the rolling mills and stay clean and smooth.

But - this stuff holds water, is porous, is galvanically different from the underlying parent alloys and will foster corrosion of two types, one type is electrical/galvanic and the other type is to promote poultice corrosion cells.

To etch is to wash this surface film off with acid. Most common products for this use are Zep-a-Lume or Alum-a-Brite both are solutions of phosphoric and hydrofluoric acids; not casual dish washing compounds. Both of these products and many more including the main acids in more concentrated forms are used to spray on and wash off the mill scale film, and any other oxides that have formed.

This process is known as etching.

To paint aluminum effectively, you'd need to etch the oxide films off using an acid then while the acid is still coating the metal flood or heavily rinse the surface with water and keep the water flowing. While the water is flowing then begin to flood the surface with Allodyne (Zinc Chromium Solution) which is a commercial name for a zinc and chromium solution that will bond with the aluminum at a molecular level while the water keeps the oxygen away from the aluminum. This material will form a Chromium Oxide film instead of the weaker and less adhesive Aluminum Oxide film if air were allowed to the metal.

Now, a primer paint or base coat paint can adhere to the aluminum. Primers also can be purchased that are alleged to 'etch' the metal without an acid wash, but the really serious large scale boat and airplane painting operations seem to use the acid then the allodyne then the primer.

Primer's job is not to look good but to be a bonding agent to the Chromium oxide layer and the paint to come as a top or finish film. I'm not discussing the Nyalec coatings in this.

If the finished boat is just etched and left 'raw' it will form an oxide film that will protect the boat from any atmospheric corrosion. That is not a protection against, acidic bilge water or poultice corrosion or galvanic corrosion, or stray current corrosion. All of these types or corrosion can be defended by correct installations on the welded aluminum boat but at the very minimum a finished boat should be etched or mechanically 'buffed' or surface treated to get rid of the 'mill scale' layer so it doesn't bring about premature corrosion sites.

Welding can be done 'too cold' and end up with a surface weld that looks OK, but has inadequate penetration. But, in most cases a weldor who has taken time to 'get his hand in' (phrase to describe a weldor with a consistent bead) has also gained the knowledge of what it takes to make a good weld and the most often want to do good welds AND have them look good too.

I do understand the lure of a higher paying job, with benefits, for the tradesman who is planning to work within the trades for his entire career. I have friends that got out of high school with me, went to union work, not welding mind you, and are already retired and I'm still building skiffs and doing odd jobs while they spend time driving their welded aluminum boats!

Hope this helps to clear up any use of terms not made clear?

Cheers,
Kevin Morin
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