Stainless boat trim tab project

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The customer brought his trim tabs in and asked that they be lengthened by 9 inches.   Tabs are made of 12 ga 304 sheet.  I had another shop shear and brake some 12ga 304 for me to nest inside the tabs' channel shape.  They did a great job on the bending, the new pieces fit perfectly inside the tabs.Tig welded with 3/32 308L filler on the TA185, red 1/8 tungsten.  I'm not the greatest tig welder but these came out alright.  Here's the original trim tabs and the new metal, all cleaned up to be welded.  I drilled a series of 3/8" holes in the overlap area to put in plug welds.  Overlap was about 1-1/2".  Got the idea from the hinges, which are attatched with spot welds.Plug welds and inside seams.Seam accross the bottom.Could have used a little more filler on this seam.  Weld came out a little flat/concave.Despite the long seam welds, they didn't warp.  I had them clamped down in every direction and the plug welds helped there too.Last edited by DesertRider33; 12-06-2009 at 01:03 AM.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Those are l-o-n-g tabs now!! They are going to get some serious pressure testing,  what sort of boat are they for?City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Yeah I don't know why he wanted them so long.   They're about 22" long now, if I remember the measurement right.  Have no idea what kind of boat they're for, never saw it.   Whatever it is,  I'm pretty sure it goes in the ocean so it's probly a descent size boat.  Looking back on it, it would have been better to just make new tabs using thicker sheet, maybe 10 ga, but that's not what the customer wanted.  I make suggestions, but don't argue with them, just do what they tell me to, unless I feel they're asking me to do something unsafe.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Originally Posted by DesertRider33Looking back on it, it would have been better to just make new tabs using thicker sheet, maybe 10 ga, but that's not what the customer wanted.  I make suggestions, but don't argue with them, just do what they tell me to, unless I feel they're asking me to do something unsafe.
Reply:Well, if you have to opportunity to redo it your way, 304 stainless really has no place in salt water.  316L is marine grade.
Reply:Originally Posted by 76GMC1500Well, if you have to opportunity to redo it your way, 304 stainless really has no place in salt water.  316L is marine grade.
Reply:the boat owner will probably be back to have you make a single trim tab.  Thicker stock and ribbing (for bracing) may be what's needed.  I have a feeling that those things are gonna be subject to a fair amount of pressure due to all that length.But, you said you made suggestions to the owner, and if he'd didn't listen....oh well....also, on 316 SS.......Is it more resistant to salt water and salt air?  I thought it was used in the marine industry due to its superior "shinability."   316 SS really polishes up well and that is a desirable quality in the marine industry.
Reply:Iv'e thought about doing that myself for my boat.  My boat runs high 70's (Donzi 22zx).   Problem is that if it is a fast boat, you wind up with more loads than the acuator can handle.  When you look at the bigger tabs like K-planes, they always have two actuators.  Now some of those are good for boats going well over 100.  If the boat that they are going on goes over 50 or so, he may want to consider beefing up the attach points to the hull as well.  Let us now how they work out. Rene
Reply:After I built them, I thought about a pair of rib braces made from the same 12 ga material, 2" wide, bent into 1x1x20" long  angles, welded in along the length of each tab.  So far, no complaints about flexing from the customer though.316 is used in the food prep and medical industries for cleanliness because it is more resistant to oxidation than other stainless alloys.   I assume it would also resist salt corrosion better than 304 or other common alloys.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Originally Posted by zerepenerIv'e thought about doing that myself for my boat.  My boat runs high 70's (Donzi 22zx).   Problem is that if it is a fast boat, you wind up with more loads than the acuator can handle.  When you look at the bigger tabs like K-planes, they always have two actuators.  Now some of those are good for boats going well over 100.  If the boat that they are going on goes over 50 or so, he may want to consider beefing up the attach points to the hull as well.  Let us now how they work out. Rene
Reply:316 is has better corrosion resistance to seawater than 304 but it's not immune and can corrode quickly if the circumstances are just right (wrong)http://www.bssa.org.uk/topics.php?article=100http://www.azom.com/Details.asp?ArticleID=863I don't know the exact alloy of this engine coolant filter basket, only that it's austenitic stainless. 18 months of use in brackish water and it was leaking like a seive due to poor welding (incomplete pen and crater pinholes) leaving lots of crevicesview of the inside after a quick clean up...