How to Fix Cracks in Alum T-Top Frame?

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Hey, all,Just a hobbyist/weekend warrior here, though I am learning to TIG, and this repair may be beyond my abilities, but I wanted to get the experts' opinions on how it should be fixed.I just noticed today that the vertical stanchions of the frame of the T-top on my boat have cracks in them, right next to where the original fabricator put the welds. This boat goes offshore and gets pretty beat up from time to time, so I guess they're fatigue cracks.Some pics of Crack #1 on the port side:And then cracks #2 and #3 are on the starboard side as shown:These first two pics are of Crack #2 on the forward stanchion on the starboard side:And this last pic is of Crack #3 on the aft stanchion on the starboard side:My main questions are,Can they be fixed, possibly by drilling holes at the ends of the cracks, to stop the cracks from propagating further, then grooving out the cracks or making "saw kerfs" through the tubing to expose clean/fresh aluminum, then welding it back together?Or do I need to rip the whole mess out and re-fabricate the whole frame? (Considering that those stanchions have lots of power/antenna/GPS/ground/etc. wires inside that will all need to be pulled out for welding and then re-installed anyway, it probably wouldn't be THAT much more trouble to start from scratch!Anyway, thanks in advance for any suggestions or advice, and sorry for the bandwidth bloat.
Reply:Vee out the cracks and weld them, AFTER you pull out the wires from inside. Next you can put plate or pipe gussets in the areas that are prone to cracking or areas you know to take a lot of stress. you may find that plate gussets work best, use 6061 material of at least 3/16'' thickness. the gussets do not need to be huge, but should be at least 2'' long where they weld to the pipes. Cut the inside corners where they will clear the existing pipe welds and if you want you can drill a 1'' hole in the gussets to give them a more " Finished" look. Use 5356 Tig Rod to weld every up with. CAREFULL grinding of the areas where you put the gussets to remove the anodizeing and surface oxididation will make your welding job easy to do
Reply:Prep prep prep I'm tagging along this thread because I like your confidence and think this gonna be a learning xperianceAlso, X2 what Dixie said plus 1
Reply:Kevin, I noticed in picture #6 another crack in the weld a little farther up that runs horozantal. you can make your gussets bigger if you want and weld them to the outside of the t-top pipes also. It's your boat, fix it how YOU are comfortable.
Reply:Thanks fellas. I've tigged steel a fair amount, but I'm a noob on aluminum.Question: What do I grind it with? Can I use a disc sander? Isn't there something about embedding abrasive particles or aluminum oxide from sandpaper that you're supposed to avoid? Also, isn't there something about aluminum "gumming up" abrasive discs that you want to avoid?Question: Since aluminum conducts heat so well, and since I don't want to separate the frame from the plastic hard-top before welding, can I maybe wrap wet towels around the alum tubing maybe 6" or 8" away from where I'm welding (assuming I'm careful about catching them on fire)? What about having someone quench the freshly welded aluminum tubing with a garden hose as soon as I lay down the bead? Good/bad idea? I seem to recall hearing that quenching hot aluminum anneals/softens it, unlike steel...Any other things I should think/worry about?(Don't worry, I'm gonna try doing the same weld in the same position on some tubing OUT of the boat before trying it on the real thing...and I suspect I'll end up taking it to someone who actually knows how to weld, rather than screwing it up myself...the tuna bite will be ON any day now...I just want to know what the right way is to do this...)Thanks again
Reply:You're going to find that's anodized and you may want to search threads/posts by rojodiablo on the subject of welding without grinding thru the anodizing as he (along with others) has covered the subject here before.  Search "bump TIG" and "TIG welding anodized".Last edited by duaneb55; 06-09-2013 at 07:50 PM.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:I do a lot of marine repair and am comfortable welding anodized aluminum. I think that welding anodized aluminum is overrated as far as difficultly but with that said I think if you have minimal experience you should let someone else do this. One problem with fixing something like this verses replacing the fatigued tubing is that it will fail again just a matter of time. One tip for anodized material is it needs maximum heat instantly to establish a puddle quickly, get in get out quickly if that makes sense. Where are you located?
Reply:Showdog75 - I wondered if that's how anodized got "blasted off."  I have not seen any anodized yet, but if I set my start amperage to 110% of my weld amps, that could do it?Dave J.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:KelvinI'm with Showdog75  -  welding ANO is much ado about nothing.The fractures are a result of hinging [load bouncing].In addition to rewelding, you might consider diagonal struts akin to those in front of the windshield. Back-bottom to forward-top provides a compression load.Opus
Reply:Thanks for all the replies, everyone. I appreciate the help. Originally Posted by Showdog75One problem with fixing something like this verses replacing the fatigued tubing is that it will fail again just a matter of time.
Reply:Originally Posted by MinnesotaDaveShowdog75 - I wondered if that's how anodized got "blasted off."  I have not seen any anodized yet, but if I set my start amperage to 110% of my weld amps, that could do it?Dave J.
Reply:Originally Posted by KelvinAnyway, I'm wondering whether, if I stiffen up the area with the cracks by welding gussets in, etc., whether I'll just force the next set of cracks to start somewhere else on the frame. Thoughts?
Reply:Originally Posted by duaneb55I doubt 10% over will be sufficient to get "maximum heat instantly to establish a puddle quickly" as Showdog75 pointed out.  Set the machine for max and use the peddle as intended.
Reply:I agree with the folks who suggest adding a diagonal strut.  Alternately, you could add multiple smaller struts if you wish (building a triangulated lattice on each side), but triangulating the frame will help with the stress fracturing where pictured by a great deal.  I'd go ahead and repair weld the cracks while adding the triangulation.The idea of adding gussets is another potentially workable idea.  Either way, you need to beef up the design somehow given the failures occurring, and how its being used.Last edited by jakeru; 06-11-2013 at 01:25 AM.
Reply:I also agree with the strut. The way that thing was designed it was guarantied to crack where it did with the overhang plus rod holders and more forces and weight.
Reply:Something along this idea might control the hinging forces enough to prevent future re-cracking, without completely spoiling the aesthetics of the framework. Attached Images
Reply:Thanks again for all the replies. Question: I'm shopping for aluminum tubing for gussets. Would non-anodized 6061 with a wall thickness of 1/8" be appropriate for a saltwater boat?
Reply:Anyone heard from SundownIII lately? I'd like to hear his take on this.
Reply:Originally Posted by KelvinThanks again for all the replies. Question: I'm shopping for aluminum tubing for gussets. Would non-anodized 6061 with a wall thickness of 1/8" be appropriate for a saltwater boat?
Reply:Originally Posted by KelvinThanks again for all the replies. Question: I'm shopping for aluminum tubing for gussets. Would non-anodized 6061 with a wall thickness of 1/8" be appropriate for a saltwater boat?
Reply:Originally Posted by walkerweldSomething along this idea might control the hinging forces enough to prevent future re-cracking, without completely spoiling the aesthetics of the framework.
Reply:Originally Posted by dave powelsonthere are many other AL grades much more suitable for salt water than 6061.
Reply:Originally Posted by KelvinLike ... for example ... ?
Reply:Originally Posted by MinnesotaDaveThat would help greatly.It was such a subtle change I almost missed it.Dave J.
Reply:Walkerweld, I like the aesthetics of your Photoshop of the added gusset, but I need all the help I can get, and some of those long welds and acute angles are bound to get me into trouble.So I was thinking of doing something simpler (I also don't have a tubing bender) as shown in the pic below.Since two of the three cracks are where you'd get cracks if the roof of the t-top rotated clockwise when viewed from the starboard side, I'm thinking gussets like this would be good to tie things together better:And although they don't look as good as the gussets Walkerweld mocked up in his Photoshop, I think they would be easier for me to pull off.Comments, anyone?Oh - also - I'm talking to a guy at a marine fab supply place about tubing, so maybe I can find a good alloy.Thanks again for all the help, fellas. Keep it coming!Originally Posted by G-sonI would add another piece of pipe. From where the new pipe in the picture joins the rear stanchion diagonally down to the front stanchion. That would prevent the first new tube from bending the rear stanchion, and stiffen the whole thing up in general.Triangles, triangles, triangles!
Reply:Looking at the original weld, it almost looks like it was done with oxy/acetalyene and flux.  I suppose it could be anodized, but thats not what it looks like.  Put the best looking gusset you can in, reweld.  If there are any flex points that are bolted, cushion them with rubber.
Reply:Kelvin, adding the 2 braces (indicated by orange lines) would obviously stiffen the vertical members of the canopy tower, but alas, it would do nothing to stop the hinging upward of the long side of the canopy.The canopy hinges upward and stress cracks the welds because the long dimension of the canopy frame is bearing on too small a spread area on the vertical tubes.Your canopy frame as it comes from the OEM is practically a "see saw" (insofar as hinging tendency).The second tube I photo shopped in would spread the loading over a greater span on the vertical tubes, which in effect changes the effective shape of the canopy from a simple "Tee", to a virtual triangle.You may have to farm out the fabrication of tubes to a custom pipe shop if you want the kind of gentle bends depicted in my mock up.But if you could live with "cut & weld" tubing fabrication............that would bring it to a method you could probably do with your own means.
Reply:You need some types of tubular reinforcement there.  I'd personally add one on each side from the back and attach it lower to the rear tube of the main beam.  Then I'd add some tubular cross bracing to the main vertical tubing beam.The rear portion is just creating too long of a lever arm there.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:You don't have to bend the extra tubes if you can't. You need the support for the rear of the overhang to take the stress off the single upper joint.
Reply:Originally Posted by VPTYou don't have to bend the extra tubes if you can't. You need the support for the rear of the overhang to take the stress off the single upper joint.
Reply:Just a thought after looking at all the suggestions so far.  The triangular bracing suggested so far is a good idea.  But it also stiffens the structure.  This transfers stress and strain that was distributed by the flexing of the canopy and vertical members to the joints and mounts that attach the canopy to the hull of the vessel.My concern is that the changes will result in fatigue cracks in the lower connections; if they aren't there already.  But I've added a few more braces in red that I think will help transfer the load down to the hull and distribute the forces over more tube and hull connections.  They may not be practical to place, since I can't see the hull where the braces I've drawn would mount.  They may not work for other reasons related to moving around on the boat.  Without a real analysis there's no way to say for sure if you need these extra braces or how big to make them or where to locate them for maximum benefit.  It's just something to consider, and maybe something to watch for going forward.  I'd hate to see you spend a lot of time fixing the current problem, only to shift the problem to the next weakest link in the structure. Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:It is true that the "second tube" in my photo shop depiction would not have to be bent.  My decision to show it as a bent/formed member was based on simply using what was available (in the photo) to illustrate how a second tube could be added using some of the OEM appearance "lines".The OEM apparently shaped the tube to include a bend in an attempt to gain some "spread" regarding the attaching point to the vertical tube.............without encroaching on head and shoulder space to the sides of the helm.Now that it is clear the OEM's method of increasing the spread did not control hinging, the idea of duplicating the shape of the old design into any new braces/stiffeners becomes not important at all.I feel that what we are really seeing in this application is that the OEM has "missed the target" as to the chosen sizes (diameter and wall thickness) of tubing that was used in designing and building the structure.And the concerns of "passing the buck" regarding how the stresses will be transmitted to the "next in line" members of the tower...........all the way to the mounting points at the base......are very real.
Reply:Just simply for the humor of "the picture" I added some more colors of bars that could be added for even more bracing yet! We are going to have you tear that whole thing apart and rebuild it yet!
Reply:Originally Posted by VPTYou don't have to bend the extra tubes if you can't. You need the support for the rear of the overhang to take the stress off the single upper joint.
Reply:Originally Posted by ezduzitThis T-top was never designed for the loads you are imposing on it with your long poles. So any effort to effect a repair might only prolong the agony. Areas of high stress might have been ruggedized had the builder inserted sleeves within the main tubes (the ones that are cracking) at brace junctures.If you are determined to just make do, at least order some of the same anodized tubing these builders use, in order to make a workmanlike job of it. Using bare aluminum will soon look like a homespun repair. Fashioning "lugs" around the junctures might also be considered if you are serious about making this last.The orange tubes shown are entirely unnecessary. It is the blue tubes which will help with the cantilever. Still, the basic structure isn't up to the abuse to which you are subjecting it by running home with the poles deployed.
Reply:Originally Posted by VPT
Reply:Would it be more effective to move the orange line down to intersect with the blue and run it to the lower front corner of the side panel?
Reply:I had the same thought as I was writing my post.  I admit that my solution may be wrong for this exact situation.  But the idea that you need to transfer the load created by the canopy down to the hull, and spread it out over more area, is worth considering.Maybe a better, simpler solution is a couple vertical tubes from the rear corners of the canopy to the boat hull, instead of a spider's web of braces and gussets? Originally Posted by Kelvin
Reply:Another issue that just occurred to me is that when I'm pulling lures off the outriggers, the whole frame of the t-top is subjected to twisting forces when the boat makes a turn, or when the lure on one rigger plows through a wave while the lure on the other rigger is skipping across the surface.In other words, the t-top frame will want to rotate clockwise or counterclockwise when viewed from overhead. Although it wasn't the primary cause, I'm sure this strain contributed to the fatigue cracking.To stiffen it against twisting in that plane would require me to add triangular bracing in the horizontal plane... Maybe I should just sell the boat or switch from trolling to chunking for tuna!
Reply:Originally Posted by vwguy3Would it be more effective to move the orange line down to intersect with the blue and run it to the lower front corner of the side panel?
Reply:Any way you can do both? Have a ridged structure that is mounted with flexible fittings. It's got to flex somewhere.
Reply:I don't know. The more I look at it, the more I feel it just wasn't intended to do what I've asked it to do, and I'm not sure there's a simple way to make it do what I want it to do without cracking all to pieces.Very discouraging, considering the time, effort and expense I put into rigging it, and the assurances I got from the original fabricator (he added the aluminum plates to the top for me to attach the rigger holders to)...
Reply:You could  run the outriggers off the gunnel like the pangas in Baja. Might not look as goodbut it works.
Reply:Looks like you have gotten a lot of good advice here so all I'm going to say is yes need a few more tubes for bracing and yes it may crack again in other places in rough seas, it's inevitable. I haven't tigged aluminum in a while myself and want to dabble in some marine fab work of my own, so keep us posted and post pics of your repair.
Reply:Originally Posted by J-WYou could  run the outriggers off the gunnel like the pangas in Baja. Might not look as goodbut it works.
Reply:I wouldn't give up just yet.  Maybe it's time to look around at what some of the other boats have in the way of canopies and support structure.  Maybe talk to some of the other captains fishing in the area and find out what worked for them.  Take a look at what the big companies making canopies are doing for structure, and modify yours in a similar fashion.  Big companies can afford engineers and computer simulations to fix these problems, without massively over-engineering the solutions and adding unnecessary cost to their products.This company actually posts photos of their products by application and boat.  They mention engineering staff on their website, so this is the kind of company I was describing.http://www.atlantictowers.com/photofinder.phpMaybe a search of their designs will guide you to a workable solution for your boat. Originally Posted by KelvinI don't know. The more I look at it, the more I feel it just wasn't intended to do what I've asked it to do, and I'm not sure there's a simple way to make it do what I want it to do without cracking all to pieces.Very discouraging, considering the time, effort and expense I put into rigging it, and the assurances I got from the original fabricator (he added the aluminum plates to the top for me to attach the rigger holders to)...
Reply:OK, so I finally got some material for gussets. (Been busy with other things.) The pipe I bought is anodized 6005A-T61.Question: What filler should I use for this? MrDixieTwister, you earlier said to use 5356. Will 5356 be appropriate for 6005A-T61 pipe/tube?Also, I bought some 1/4" plate from a local welding shop in case I want to make the gussets out of plate instead of pipe/tube. (This would definitely be easier for me to fit, and probably be easier to weld.) I'm not sure what alloy the plate is ... probably 6061. Question: Would 5356 filler be appropriate for that 6061 as well? (I have 4043 on hand, but want to use the best or proper filler.) Remember, this will be in saltwater, so corrosion is probably my biggest concern.I'm gonna try to do the welds in the positions I'll face on the bench first. If I can handle them on the bench, I'll wail on them in the boat.Thanks again, everyone. Wish me luck!
Reply:Update for future reference for the benefit of the forum:I just spoke to SundownIII whose opinions I respect very much on this sort of thing, and to summarize his comments:1. When you get cracks in the HAZ like I have, generally you want to cut out the old material and use new because 2nd-pass welding in the HAZ weakens the HAZ even more, and the cracks will reappear.2. For that reason, I should add gussets and/or reconfigure the joint to: a) move the stresses to somewhere else than where the original cracks developed, andb) rely for strength on "first time" welds in virgin material, rather than 2nd-pass welds in the existing HAZ.3. Use 195-205A with 1/8" tungsten and 1/8" filler (5356) to "bump weld." SundownIII said it will not be obvious when I have developed a puddle, because there will be a layer of oxide over top of it, but I need to "poke through" that oxide layer with the filler rod. He said "timing is critical with bump welding."4. Since the anodizing will be gone after bump welding, I should protect the non-anodized weldment after welding with something. He recommended Rust-Oleum Aluminum paint.5. If, instead of "bump welding," I choose to grind off the anodized layer before welding, I should use a carbide burr and/or a special flap disk made for aluminum. (Avoid abrasives containing aluminum oxide because it will contaminate the weld puddle.)I hope I haven't mis-reported what SundownII said, but wanted to post it up because I respect his opinion on these things – I believe he really knows what he's talking about, and when he doesn't, will say so – and wanted to save it to the thread for future reference by others.It's too bad he doesn't post here anymore. He was an asset to the forum.
Reply:Here is an aluminum weldability chart - should get you the info you need:http://www.alcotec.com/us/en/support...tion-Chart.pdfDave J.Edit:  looks like we were posting at the same time and you already have the info you need - good luck Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.