1982 Valco with Anodized ribs/framing?

[solarkid1a]

Hi people I need some advice.
I recently aquired a 1982 21 ft all welded Valco Aluminum boat. I found a few cracked welds in the vertical square tubing deck supports. I have a really good welder that has done work for me for years.
I had him fix/replace the cracked welds and he mentioned to me that the aluminum tubing (i.e. the area to be welded) looked to be anodized. He said that he tried to Tig weld it at first and it just turned black so he grinded it down to get thru the surface.
To me, the rectangular aluminum tubing that he welded look like standard bare aluminum with its natural oxidation.
Anyways, he also suggested that I spray Zinc Chromate on the areas that he welded.
I'm asking people on this forum simply to get a second opinion. He has done great work for me and I feel pretty good with his suggestions but there are several posts on this site about keeping aluminum bare in its natural state. This seems to be the favored decision by many of you here on this site.
In summary:
1. Has anyone out there heard of a Valco boat having Anodized framing?
2. Should I spray Zinc Oxide on the areas that he grinded down and welded or just leave them be?

THIS BOAT HAS ZERO SIGNS OF CORROSION ANYWHERE ON IT.

[solarkid1a]

Just to add a bit more about this. If the framing was anodized it would have to be anodized prior to being installed on the boat right? But then they would have to weld anodized aluminum right? This makes no sense.
I also wanted to mention that my welder says "I think the quality of the aluminum used is of decent quality and in the 600's. It's definitely a higher quality than your typical 12 to 14 ft aluminum boat.

Any welders out there that could shed some light? I am a Mechanical Engineer so please do not hesitate to get technical.

Thanks

[gandrfab]

Yes it would have been anodized prior to being installed, It's an elctro-chemical prosses that gets dunked in a tank.
As a T-top and tower builder I TIG weld anodized without removing the anodized all the time.
I tried to MIG it one time and it's a bear to get the ark started.

[solarkid1a]

Yes it would have been anodized prior to being installed, It's an elctro-chemical prosses that gets dunked in a tank.
As a T-top and tower builder I TIG weld anodized without removing the anodized all the time.
I tried to MIG it one time and it's a bear to get the ark started.

Thanks "gandrfab" to clarify, he did TIG weld it but he first had to grind the old and cracked welds down to remove the anodizing "I guess". So now, as is I have annodized deck framing that "could" have un-annodized areas on or near the new welds. Would you suggest that I leave the welded areas alone and as is? Or, should I follow my welders advice and spray Zinc Oxide on the welds?

Any info would be greatly appreciated.

[gandrfab]

I would provably leave it alone, but would wait for kmorin and others advice.
Good luck with your project.

[kmorin]

solarkid1a,
first, without pictures and in some cases of certain questions we'd need lots of experimentation and surface testing to make informed suggestions as a Forum. So these remarks are suggested as a background to your question(s) not final answers.

First, anodizing is usually done to provide a protective surface for looks and clear anodizing on tubing or materials left out side, above deck and seen (T-tops, hand railing, deck fittings...) seems to be common in some boats, but the cost to anodize hollow structural tube in the bilge seems questionable? I mean that Valco is not a heavy plate 30mile offshore, pair of 300 hp, high end name brand as far as I know, so their interest in actual anodization of structural extrusions seems to me to raise more questions than provide answers.

I'm not in anyway questioning your welder found some weld problems- but just wondering if this coating were more of a paint/sharkhide/nyalac type of clear coat that would react to welding by burning and therefore make the area 'un-weldable' without cleaning off the coating (film of plastic) in the weld zone?

Or could there have been other factors in the weld's initial results?

The second case that could leave the weld with serious problems is the old welds' presence. This is a fillet (V between the two original metals) that is cracked at one side or down its centerline (?) So, this area has to be cleaned before any welding is done because this face has the black powder of vibration ground aluminum powder mixed with whatever bilge and atmospheric chemicals have been forming for however long.

So... the welder would find the exact same 'thing'/result or un-weldable conditions if the original weld was not removed due to the hot gas and molten puddle leading edge vaporizing all the water, powdered aluminum oxides, salt residues, paint coatings and other 'junk' that would have been present in the weld zone. When the uncleaned weld area was heated all the gases formed would expand (turn to steam) and escape upward and out lifting the argon cover gas, and rendering the weld useless- at least in my experience.

I still don't know if there were any coatings, anodization or paint/nyalac films in the bilge structure as I'm not familiar with the Valco in repair? But in general, I'd have removed the entire old weld- all of its parts, and cleaned the sides of the remaining parent metal to bare shiny aluminum back about 1/2" to 3/4" in all directs of the HAZ (heat affected zone) before I welded it, regardless if the area were coated or anodized.

Recoating the area welded?
I'm not sure of the bilge structural members being coated so... to test that I'll assume you don't' have heavy duty chemicals at hand but you do have house hold cooking supplies? clear the bilge area where you can work unobstructed in the area of the new welds. Heat a cup of house vinegar to hot, not boiling but say 100-120 F, and handle it carefully with elbow length gloves in a coffee cut much larger than the volume so the liquid is not sloshing over the top.

using a paint brush, then paint the area of the square tubes along side the welds, and the weld area too. Paint about 4" along the tubing away from the weld. The vinegar will act two different ways depending on whether the area is coated/anodized or not. The entire area will lightly foam, or clean to a dull, not shiny, but unpolished aluminum surface. let the vinegar run into the bilges and use the garden hose to dilute/rinse the whole show out the bilge drain at the stern.

When done rinsing, if the area is coated, there will remain a color boundary line between the coated and un-coated (cleaned during welding prep) areas where the latter will be somewhat lighter/whiter in color and the coated areas remain a closer match to the original bilge area structural tubes and not have a paint line of color 4" to 6" away from the weld.

this color test will help you answer your original question about Valco's bilge framing structural coatings? The mild, but warmed, acid will begin to etch bare aluminum brighter/whiter in color, but will rinse off both anodized and paint films leaving the color similar to that metal's original coloration.

I don't see any reason to coat the welded areas with with Zinc Chromate primer but then I'm not sure what the boat's bilges are like on a regular basis. My reason for coating with primer is usually reserved for inaccessible parts/tanks/structures that #1 will see water collection regularly- but will dry out- #2 As a preparation for a full paint job of that material where Zinc Chromate primer is a regular layer in painting aluminum to a full coating system. #3 where I thought the bilge was acidic or corrosive enough to wet the area with a corrosive solution, and I don't see that in the bilge of a light weight skiff?

I'm not sure if all this addressed your questions directly, but I'd try to reply with more clarification if you'd like to ask more detailed questions. What caused the original weld failure is what I'd be paying most of my attention.

Cheers,
Kevin Morin
Kenai, AK

[solarkid1a]

kmorin:
Thank you so much for your detailed response. I think I was able to follow about 90% of your details and instructions. I will definitely do the vinegar test. Your description of "impurities" makes sense. I was a skeptic about the anodizing originally and still am. It sounds like I should just keep the welds bare. Again, this is primarily a fresh water boat. I'll try to upload pics within the next week or two. The cracked welds were on vertical pieces of tubing that essentially were there to provide a flat mounting structure for cross beams for the floor to mount to. "The vertical pieces of tubing connected the ribs to the deck framing". So, at the risk of sounding hypocritical, the cracked welds were basically floor supports. On the other hand, when I note the location of the cracked welds and then step back away from the boat and look at it from its side, my suspicion is that they cracked from hitting chop. Supposing the boat was planing in a choppy lake or here in the Bay Area Delta, the location of the cracked welds looks to be right where the chop would be hitting the boat while it was in plane. So, Finite Element Analysis or in laymans terms, I think that was the area being constantly stressed. This stuff is tough to explain in words so, as requested I will try to upload some pics soon. The good news is that the new welds "look" great and according to my welder, performing the actual welding was fairly easy. In the past on another boat, I have had welders have a lot of trouble with old aluminum. I guess "time will tell". But, I guess, the ease of welding is a good sign.
Thanks again and I'll try to get you an update soon.
Justin

[kmorin]

solarkid1a,
if the legs that had failed welds were vertical (?) their lower ends welded to hull longitudinals and their upper ends (via plates OR native material) are welded to the deck transverse frames/beams; that seems like a truss? The inverted truss is the hull's bottom panels loaded in compression as the boat runs, depending on the pitch of the bow and speed the forward edge of the running waterline is somewhere in an approximate V from keel to chine. It appears that the compressive load would distribute along the hull longs in the bottom which were then locally supported upward to the deck (tension chord) beam?

The longs are welded to the hull somewhere, in some pattern, so the square tube verticals are the truss web elements and the chord is the deck beam. What it sounds like you're describing is the truss's failure at the web connections between the top and bottom chords (bottom panels w/longs and deck beams). The vertical legs relying on their wide cross section (of the extrusion) welded on two axis to perform the job of triangulation most often seen in common truss webbing.

I don't know what the factory welds looked like (?) but... I think the high speed load cycling ( slapping) of this boundary area (lead edge of planing waterline) in a super light wt hull at planing speeds may be a design flaw that shows up again? If so, then reducing the spacing of the 'web' vertical tie-in points for a few deck beams in this area say 3-4' fore and aft; should create enough stiffness to overcome the boat's original susceptibility weld vibration cycling failure on in this area under those conditions? I don't really see the weld failures as likely to have come from initial truss failure in vertical loading, I suspect the welds gave up as a result of some high frequency harmonic (tuning fork event, like when you thump the side of a metal boat) combined with a lower frequency impact loading from the fast slap of a low deadrise light hull in a little wind chop.

Many factory welds of production boats are welded with MIG wire of 0.030" or in some cases even 0.023" wire, not that I can speak about a Valco. So the welds are smaller in section by nature of that wire size. This leads to minimal weld sections even in areas where, like your boat, welds may fail due to area section being inadequate for the cycling nature of the loads. Also factory welds have more start and stop 'notches' and craters and are put in fast and furious. All these factors lead to perhaps less that the best welds; perhaps that was another factor in these particular welds' failures?

cheers,
Kevin Morin
Kenai, AK

[solarkid1a]

Kmorin: Thank you! I have no doubt that the original structural design of this boat could have been improved and it would not suprise me if the "new" welds crack if I push the boat too hard. Also, I will respond more later because, I am still processing your response. For now, here are some of the "before" pics of the boat from when I got it. As can be seen in the pics, it was being stored in an extremely dusty dirt semi truck yard. I have since washed the hell out of this boat.

Overview

Framing overview (looking toward transom)

Setback view of the area with the cracked welds on the vertical supports.

(3) cracked welds on the vertical supports

Close up

[gandrfab]

If I was approached to repair that I think I would add a gusset. And talk about adding gussets to the others broken or not.

[kmorin]

solar, as gandrfab says increasing the weld surface area may go along way to increasing the joints' tolerance for the loads that seem be expressed on those tiny 1" horizontal welds?

One other aspect the photos show clearly is that the joint need not be at the horizontal lower edge/corner of the transverse rectangular tube's profile. A gusset that was an inverted trapezoid of 4" length along the upper transverse tube's side wall, and sitting the full width of the 'top hat' longitudinal's top surface would distrbute the weld load to well over 4x its current area. IT also may be wise to consider the lower shape to be straddled or fit to the top hat extrusion so the entire load was not a 'notch' for the bottom long (top hat extrusion) which may fail at the newly (suggested) gussets' transverse welds?

A note as long as you posted images; top hat extrusions are for the birds! The shape is not full strength unless that shape is riveted on its two flat legs to another surface, the extrusion was originally intended (I think) for aluminum over the road trailers that were insulated and the two sides of the top hat provided riveting surfaces for siding. Notice that as welded, the top of the 'top hat' can flex somewhat at the main vertical to leg joint? its not the best for the job. both the top surface can deflect from its two side vertical elements AND the two verticals can raise up from the bottom as they're welded at a distance of 1/2" to 5/8" (guess?) from the lowest edges of the two side elements? Therefore, what was intended to be a rigid bottom frame does show two obvious locations of deflection in the material making the 'truss' flexible not rigid.

Next is alloy (?) and finally (?) the two flat surfaces of the hull to top hat flange leg face joint. This is a good place to get surface pitting corrosion due to the thin film of bilge water that would naturally stand in this interface.

If it were my skiff I'd rinse here with acid and rinse with the garden hose for a day or so. The welds that were re-done will likely suffer the same problems as the originals as the entire deck hull framing structure is light for the skiff size and speed potential.

Cheers,
Kevin Morin

[solarkid1a]

Thank you all so much for your intelligent feedback. Kmorin: It took me a while to process all of your information but after researching some other posts and figuring out all of the terminology, I am confident that I understand most of what you are pointing out and suggesting. Overall, you bring up some really good points especially the fact that the new welds may break/crack just like the old ones if I don't beef up the entire framing, gussets, weld area etc... In addition, I'm a bit of an adrenaline junky and have a tendency to beat my boats and toys pretty hard.

This isn't my only boat so at this point, I have decided to slow down this project and perform some trial runs and determine if this "Corvette" is one that I want to keep or move on to another. The San Francisco Delta is not too far from my home here in the Monterey Bay and I'm looking forward to exploring it with a boat that can handle 30 to 60 mile "each way" day trips (sheltered brackish and fresh water). However, inland or not, "The Delta" does get wind chop and if I'm 30 miles away from my launch site, I want a boat that can plane through light chop at 20 knots minimum. Though this example is nothing like the ocean, I am visualizing a lot of shock and stress on those welds which will lead to fatigue and ultimately, failure. It would not surprise me if this is what caused them to crack in the first place.

I am a very hands on Mechanical Engineer but I do not have the welding skills nor equipment to perform the structural modifications that this boat needs. My best "guestimate" is that it would cost a few thousand to pay someone to perform the structural upgrades that you are suggesting (which I agree would be the best way to improve/fix this boat).

Next steps:
Acquire and outboard for the boat
Perform some trial runs, gently testing it in different conditions.
Determine if I will keep it or sell it and move on.

Either way, I am learning a ton and really appreciate all of you!

As my trial run process advances, I'll post updates.

Justin