Cracked Weld in Arch (310)

[Ralph Johnstone]

A few ideas based on experience :

Hunter 340 Arch

Is anyone familiar with the procedure to remove the arch on a Hunter 340?

forums.sailboatowners.com

Search the archives for "Hunter arch removal".

 

[BigEasy]

Gee, all the guy asked was do you have to take the arch off the boat to have it welded or can it be welded while on the boat. Basic yes, no or maybe question.
He didn't asked for an engineering study to be done or is it a safety issue.

Thanks Ward; my thoughts exactly.
He is not going to ascertain the scope of the job or cost estimate until he has a welder(s) inspect the arch. Period

 

[colemj]

Disclaimer: I don't have a Hunter with a stainless arch, and I am not a welder.

If your boat is going to distort in that area simply by removing the arch, I'd be too afraid to sail on it. I know Hunter is often the butt of a joke about bendy, etc, but I don't for a minute believe that this will happen by removing the arch (I don't believe it at all for other aspects either).

I agree that the fiberglass could be burned a bit by welding that foot in place, but a welder would be a better judge. A compromise would be just removing the nuts and jacking the end up off the fiberglass leaving the bolts (or temporary longer bolts) in place for indexing.

Otherwise, removing that arch looks like a dead simple job. Even with 5200, that would only slow down the removal by a few minutes. 5200 on a flat piece of metal like that is very easily dealt with.

I would think that the choice of removing the arch and welding it remotely vs. welding it on the boat would be determined by how well the welder can access the geometry for the weld. This area doesn't look easy with closed up angles and deck in the way. Also, it looks like it has pulled away from the foot plate at the crack, so would need to be put back in place.

With the overhead traveller, that particular weld really takes a beating. Talk to the welder about adding a gusset to the foot plate or similar there to strengthen it. I'm not sure that original weld had a lot of penetration, so also talk to the welder about removing the foot plate altogether, cleaning out the old weld, and making a better weld.

Then why not do the other side? If it looks the same type of weld quality, or the welder thinks a gusset is a good idea, then make both sides the same.

Personally, I'd remove the arch and give the welder the best possible conditions and options for fixing it. If you and the welder are convinced that this weld just needs to have another bead laid over it, and doing so is easy enough, then I'd jack it up off the fiberglass a few inches and weld it in place.

Mark

 

[Ralph Johnstone]

He is not going to ascertain the scope of the job

He most certainly IS going to ascertain the scope of this job ! ! !

Who would you have do the calculations and other details ? The welder ? The OP fully understands the problems he is faced with. I'm presuming its part of his current profession.

Actually, I am an Engineer - had already determined that structurally it was a problem.

I've been looking at my boat today which is one year older than the OP's and with the excpetion of his SS arch (compared to my FG arch) is identical in every other way. I don't have an answer yet on how to remove the arch if it's solidly adhesed to the deck and an answer I can live with may be a long time in coming.

If the problem were in my lap, there here is no way in hell I am calling in a welder to determine HOW to handle the job other than the welding. He has the education and training to make those decisions. Of course I'll respectfully listen to his suggestions ( as I always did) to see if I can learn anything from him. However, I will determine how the job is to be done.

• He will know nothing about possible damage to the FG contact with the hot SS base.
• He will know nothing about the magnitude of the tensile stresses on the cracked SS weld.
• He will know nothing about any reinforcement or the size which may be required to build up the joint to an adequate strength.
• He will know little about how to flex the hull back into a shape that will again fit the arch if the hull deforms significantly. Fact: shaft alignments are always done in the water

All he will know is how to weld in positions 1, 2, or 3 and whether the weld will be TIG (most likely) or MIG (which won't be as pretty but may be stronger). That will be the limit of his determination. There is very little education in the above areas as a welder serves his apprenticeship and/or attends a technical school required in his particular jusisdiction. In BC and most surrounding areas, welders are damn good because of the apprenticeship and schools they attend where they learn how to weld along with the metallurgy of the metals they join . But all of this education is focused ONLY on welding. Want the pipes to fit together properly before welding .................. get the pipe fitter.

In other words, my only request of the welder would be "how much to weld the cracked joint and add possible reinforcement (of my design) on the arch which has been removed from the boat?"

The OP has a large advantage here over most people caught in this particular conundrum :

Actually, I am an Engineer.

For anyone else stuck in this position, I would suggest a shipbuilder who employs a good welder. Unfortunately this will formalize the work and likely remove much of the DIY content with an increase in the final price of the work.

 

[dlochner]

Some general thoughts.

The foot of the arch should be separated from the hull. The heat developed while welding will most likely damage the fiberglass, if not structurally certainly cosmetically.

5200 can be removed with a scraper blade in an oscillating tool. A product, Marine DeBond, will break the bond between 5200 and whatever it is attached too. It will take patience and some wedges to make it work.

If the arch is under any kind of tension, it will immediately known when the first foot of the arch is removed, stand back!

If the arch is removed or one foot is removed, do not move the boat until it is reinstalled, if the boat is in the water when the arch is removed, leave it in the water; on the hard, leave it on the hard.

Be certain to polish and passivate the weld after it is completed.

Good luck.

 

[Ward H]

@rjadelsohn
I don't believe there are many big sport fishers on our end of the bay or even on the BB but there sure are in Cape May.
Maybe call around that area, find a couple of SS fabrication and repair shops, take a day trip to CM, visit some shops with photos of the arch and broken weld. I'm sure an interested shop can guide you to a marina where they can do the work while you're in a transient slip. That will save on mobilization costs.
Then a nice sail to CM, get it repaired by professionals who know how to handle a job like that. It will be a piece of cake for the guys who build, install and modify the SS on those big sport fishers.
If they're too busy to take on a smaller job like that you may get some good references who will do it.

BTW, I'm almost next door, on Cedar Creek.

 

[sailme88]

Before you attempt the fix, you need to determine the why. Welds just don't spontaneously crack. Often times reciprocal cracks are in the mix. As a sailor, you're aware of forces, and how they work with you or against you.. .The force needed to crack a weld and possibility more can be significant. Do your homework and ascertain the cause.

 

[...3TacksontheWater]

My .02, that repair needs to be done off the boat, in a shop:

George

 

[shemandr]

I enjoyed that video because I don't know anything about welding. I learned a bit. The welder said he expected to use 80 amps during the weld. How would you get that much juice to the cockpit of a sailboat not to mention the Argon gas tanks.
When my sailboat spreader mounts needed a TIG weld repair I had to transport the mast to the welder's shop.

 

[rjadelsohn]

I enjoyed that video because I don't know anything about welding. I learned a bit. The welder said he expected to use 80 amps during the weld. How would you get that much juice to the cockpit of a sailboat not to mention the Argon gas tanks.
When my sailboat spreader mounts needed a TIG weld repair I had to transport the mast to the welder's shop.

Most of the time the welding equipment is powered off of the truck. For working on a boat they will need long leads. Boat likely needs to be in slip or wet well that is vehicle accessible. One other thing to note is that they clip to what they are welding as part of the ground loop, which can wreak havoc on the electonics. I was warned by one welder…

 

[rjadelsohn]

Before you attempt the fix, you need to determine the why. Welds just don't spontaneously crack. Often times reciprocal cracks are in the mix. As a sailor, you're aware of forces, and how they work with you or against you.. .The force needed to crack a weld and possibility more can be significant. Do your homework and ascertain the cause.

Our best guess is the damage relates back to other damage from Sandy… Weld likely developed a hairline crack at the time which allowed moisture in, leading to the problem now.

 

[Ralph Johnstone]

If the arch is removed or one foot is removed, do not move the boat until it is reinstalled, if the boat is in the water when the arch is removed, leave it in the water; on the hard, leave it on the hard.

Good point.

I can tell you that my boat arrived in Vancouver without the arch installed for shipping reasons. The arch was instaled on the hard by my dealer.

The OP may want to consider doing the repairs on the hard (extra costs) in order to return the hull to the same shape (as close as possible) as to when ther arch was installed by the dealer who originally sold the boat.

Once again, if I were saddled with this job, I would also think that installing it on the hard would be an easier way to do it.

 

[colemj]

If Hunter sterns are deforming just by removing that arch or moving the boat without it, then I will need to adjust my opinion of them.

This is not equivalent or similar in any way to performing an engine alignment in the water. The position, the structural support, the force lines involved, and the tolerances needed are chalk and cheese.

If removing that arch deforms the stern so that reinstalling it isn't possible or difficult, then there are serious structural issues with the boat.

It wouldn't surprise me if this weld failed without any storm or similar to blame. If Sandy caused another boat to fall on the arch, then that would certainly be a cause, but otherwise with the traveller on the arch, all of the load is on one of those two mounts - one will be in compression with the other in tension. And those loads can be significant and cyclically repetitive. The other two mounts are mostly just holding the arch up vertically and taking little side-side forces like the one that cracked.

Mark

 

[Rick Webb]

Removing the arch is not simply unscrewing the fasteners and pulling the arch off. At least half of those fasteners are not going to want to come off. Half of those are going to break in the attempt. Not sure of the 310 but the 29.5 which if I remember right was the 310s predecessor was available with or without the arch so not an issue with removing the arch I would not think. However, if the plate is removed from the arch and welded back without a jig or on the boat there is a very good chance part of it will end up cattywampus. A competent fabricator will know how to address this. A good welder and a good fabricator are not the same thing.

 

[colemj]

I don't think removing the fasteners will be a problem. They are stainless fasteners through stainless plate and the pics show everything clean. They won't get stuck in the fiberglass or sealant, as they can easily be unscrewed or punched out from that. They won't be seized, so nothing to break.