Small welding job - what should I ask/specify

admin

I really know nothing about welding, and I need a small job done on a part of the steering mechanism of my 25' sailboat.  I am looking for help or suggestions on how to specify the job to be sure the completed project is strong enough for this application and appropriate to a marine environment.Are there specific materials I need to specify for strength and use in a marine environment?Are there questions I need to ask to be sure the welder understands the task and is qualified to do the job properly?The job is adding a small (approx 7" x 2" x 1/2") bar to the existing cast aluminum steering quadrant, with a threaded mounting point to accept a bolt that attaches a hydraulic linear drive to the steering quadrant of my sailboat.  The steering quadrant clamps around the rudder post and is used to swing the rudder left/right to steer the boat.  I've attached a photo that shows the desired completed project (photo is of the same project on another boat):Since this is part of the steering mechanism, and significant force can be applied, strength is a primary concern.  Failure of this part could have catastrophic consequences.Thanks for any help, and if you have referrals to someone experienced in marine welding in Seattle, that would be appreciated as well!!-Pat
Reply:Pat,If the quadrant is off the boat, then the modification you require is not that difficult a job.Most any good marine fabricator should be able to do that job.  It's really pretty straighforward.The only thing I'd do different from what you show, is for the vertical piece (where the bolt is installed), I'd start with a larger diameter aluminum rod (about 1 1/2" in dia) and turn the top down slightly to receive the connector from the steering ram.  I'd keep as much "shoulder" on that vertical piece as possible.  I'd also recommend running the SS bolt all the way thru the vertical member and the flat and putting a nyloc nut on the bottom side.  This would minimize the problems you may have in the future with SS galling to aluminum in screw threads.I can't recommend a shop by name, but there should be many qualified shops in the area that can do the work.  I used to be a dealer for Tollycraft Yachts which were built in Kelso, WA and I've seen some excellent "metal work" come out of that area.PS:  Are you converting to hydraulic steering from cable or simply adding a hydraulic autopilot?The reason I ask is because if you leave the cable steering mechanism in place, you're adding a lot of resistance in the system, much more than the rudder itself will exert.  That's why, with most cable steering systems, a helm mounted autopilot (turns the wheel) is recommended.Last edited by SundownIII; 04-05-2011 at 01:19 PM.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIIPat,PS:  Are you converting to hydraulic steering from cable or simply adding a hydraulic autopilot?The reason I ask is because if you leave the cable steering mechanism in place, you're adding a lot of resistance in the system, much more than the rudder itself will exert.  That's why, with most cable steering systems, a helm mounted autopilot (turns the wheel) is recommended.
Reply:I agree with Sundown's post.  This is a relatively straightforward project.  However, what you really need in the best of all possible worlds is1 - someone to do the engineering to design you a fabricated assembly that will function in the intended application2 - someone to fabricate the design according to the engineer's specifications.Insofar as what alloy to specify, I can't tell you that, no one can make a guaranteed recommendation, without an engineering analysis of the design.  Since this is hardly ever done outside of a manufacturing design environment, any recommendation you get is, at best, a guess.  That said, there's lots of stuff that's holding up just fine with guesswork.  If the design shown in your photo is a copy of something done by a boat builder, and tested  in the real world, then you're probablly OK with the design as shown.  If this is an unproven design, then let the buyer beware...What I can tell you is that 6061 is a commonly available aluminum alloy, that can be readily welded, and has average corrosion resistance in a marine environment.  There are alloys of aluminum that have better corrosion resistance properties, but they are not all readily available in round or rectangular bar stock form; which is what you need to make this modification.  A skilled fabricator will likely recommend using 6061; although alloys of aluminum from the 3XXX and 5XXX series are also weldable and used in the marine environment.  A recommendation for any grade besides a 3XXX, 5XXX, or 6XXX should be discussed in greater detail, as aluminum alloys from other than these grades are lower in strength and/or harder to weld.  Some are impossible to weld.  There are pros and cons to each of the grades of aluminum.  A big part of the choice of which grade to use will be based on what's available and affordable.If there is a possibility that these parts will see direct exposure to salt water, then you'd be better off talking with your fabricator of choice about anodizing the finished parts or coating them with a marine grade paint.  Anodizing will cost more and require removing the parts from the boat.  But anodizing the finished parts will give the best corrosion and wear resistance.You should discuss what filler metal will be used to make the TIG welds necessary to complete the fabrication.  The ultimate choice of filler metal will depend on the base metals being joined.  There are two common grades however; 5356 and 4043.  5356 grade filler metal will produce the higher strength welds with several grades of aluminum.  But 4043 is more compatible with a wider variety of aluminum alloys.  If your fabricator doesn't recognize these filler metal alloys and inspire your confidence when telling you why he'd chose one over the other, then let the buyer beware...The best way to ensure that you're talking to an experienced fabricator is your own common sense and judgement.  Did you contact someone with obvious past experience in marine fabrication?  How long have they been in business?  Do they have references?  Have you spoken to someone else who's had work performed by this individual?  Are they carrying liability insurance?  Do they warranty the work?  Will they give you a written, binding quotation for the work?Is the quotation comparable to the other quotations you solicited?How much of this investigation you do should be proportional to the risk involved in the project.  If this part fails, what will happen to you and anyone else on the boat? Originally Posted by patjaI really know nothing about welding, and I need a small job done on a part of the steering mechanism of my 25' sailboat.  I am looking for help or suggestions on how to specify the job to be sure the completed project is strong enough for this application and appropriate to a marine environment.Are there specific materials I need to specify for strength and use in a marine environment?Are there questions I need to ask to be sure the welder understands the task and is qualified to do the job properly?
Reply:Thank you both, I really appreciate the time and expertise you shared, particularly the information on the materials to look out for.
Reply:pat,I'm often amazed about all the "you need an engineer"  EEK EEK I read on here.  In an ideal world, sure.  But the reality is to use common sense.  From what I can see with your quadrant steering, I think that 2" bar is way more than adequate.  If you look at the very top of your picture, that pulley, with it's little axle is carrying all the force of the quadrant steering.  What size is that cable?  3/16?  3/16 1x19 stainless is rated at 4000 lbs.  My point is, from a common sense perspective, that addition to your quadrant isn't going to break.Dumb question, if you have tiller steering now,  are you hooking up a different type of steering or adding an auto pilot?  Either way, it looks like you have quite a bit of room above your quadrant.  Have you looked into Edson autopilot tiller arm?  It will get your rod above the quadrant which is what that round boss is doing.  It will be manganese bronze which is much better in the marine environment.The only if on it is can Edson match your rudder post since it's square.  It looks like the radius hole can be drilled anywhere between 6 and 10 inches so if would work there.  You could probably buy one, have a machinist....  Just looked at their build sheet.  "When bore issquare, notewhether points orflats are fore and aft.SIze is measured bythe length of thesides."It looks like only a $99 machining charge to get that square hole put in one.  But best to call them.  Anyway, hope that helps.  Might get you where you're going and might cost less.  It'll also save you taking your quadrant out.  AND, it'll already be engineered  Best of luck
Reply:Thanks David.  I am adding a Raymarine X-30 autopilot with an Octopus Marine linear hydraulic drive.  I have looked into the Edson tiller arm.  I know several other boats of the same make and model as mine that have gone with the custom-machined Edson arm for a square rudder post like mine.  I will go that route depending on the cost of the welding job.  The base price of the Edson tiller arm is $420, plus the custom charge for making it adapt to a square rudder post rather than the more common round-with-keyway design.
Reply:Jesus Christ,We're making a mountain out of a molehill.What the OP is proposing is a "simple modification" to a simple system.The only things a fabricator/designer needs to know is how many degrees of arc (rotation degrees) the rudder swings from hard over port to starboard, and what the travel is in the hydraulic ram.  These two factors will determine where the "rotation point" needs to be located.Common 6061 stock is more than adequate for this mod.Guys, this is a 25' boat, not an America Cup contender.That mod shouldn't cost the OP more than $200.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by A_DAB_will_doI agree with Sundown's post.  This is a relatively straightforward project.  However, what you really need in the best of all possible worlds is1 - someone to do the engineering to design you a fabricated assembly that will function in the intended application2 - someone to fabricate the design according to the engineer's specifications.Insofar as what alloy to specify, I can't tell you that, no one can make a guaranteed recommendation, without an engineering analysis of the design.  Since this is hardly ever done outside of a manufacturing design environment, any recommendation you get is, at best, a guess.  That said, there's lots of stuff that's holding up just fine with guesswork.  If the design shown in your photo is a copy of something done by a boat builder, and tested  in the real world, then you're probablly OK with the design as shown.  If this is an unproven design, then let the buyer beware...What I can tell you is that 6061 is a commonly available aluminum alloy, that can be readily welded, and has average corrosion resistance in a marine environment.  There are alloys of aluminum that have better corrosion resistance properties, but they are not all readily available in round or rectangular bar stock form; which is what you need to make this modification.  A skilled fabricator will likely recommend using 6061; although alloys of aluminum from the 3XXX and 5XXX series are also weldable and used in the marine environment.  A recommendation for any grade besides a 3XXX, 5XXX, or 6XXX should be discussed in greater detail, as aluminum alloys from other than these grades are lower in strength and/or harder to weld.  Some are impossible to weld.  There are pros and cons to each of the grades of aluminum.  A big part of the choice of which grade to use will be based on what's available and affordable.If there is a possibility that these parts will see direct exposure to salt water, then you'd be better off talking with your fabricator of choice about anodizing the finished parts or coating them with a marine grade paint.  Anodizing will cost more and require removing the parts from the boat.  But anodizing the finished parts will give the best corrosion and wear resistance.You should discuss what filler metal will be used to make the TIG welds necessary to complete the fabrication.  The ultimate choice of filler metal will depend on the base metals being joined.  There are two common grades however; 5356 and 4043.  5356 grade filler metal will produce the higher strength welds with several grades of aluminum.  But 4043 is more compatible with a wider variety of aluminum alloys.  If your fabricator doesn't recognize these filler metal alloys and inspire your confidence when telling you why he'd chose one over the other, then let the buyer beware...The best way to ensure that you're talking to an experienced fabricator is your own common sense and judgement.  Did you contact someone with obvious past experience in marine fabrication?  How long have they been in business?  Do they have references?  Have you spoken to someone else who's had work performed by this individual?  Are they carrying liability insurance?  Do they warranty the work?  Will they give you a written, binding quotation for the work?Is the quotation comparable to the other quotations you solicited?How much of this investigation you do should be proportional to the risk involved in the project.  If this part fails, what will happen to you and anyone else on the boat?