Drill Hole in Stainless Steel Pipe

[john manning]

Because your drilled hole has not crossed the moulded corners of your upright the upright retains a lot of its strength for tension and compression. Bending loads are a potential problem.

If you want to reinforce this arrangement weld a short section (eg 1 inch) of 1,1/8 tube into the hole you drilled.

[Bloodhound]

Originally Posted by sy_gilana

I would weld a short piece of pipe into that hole, about 3/4" long, and push fit half way in, then weld all round.

Either a gusset between the vertical and horizontal, or a collar around the hole. Either should work well if, indeed, any reinforcing at all is needed. BTW, 16 ga is not pipe; it's tube with about a 1.3 mm wall, not as stout as you might think.

[Ken Fry]

Originally Posted by feudalkaos

I was mistaken, the cross member is 2in.

Attached are 2 more pictures showing how the dinghy sits.

Your drawing makes it look like the dinghy load is fully cantilevered, in which case the hole is in a very bad location. It looks like there are wires helping to support the solar panels (and putting them under a bending load -- trying to break them?). Perhaps these actually go directly to the davits instead? If those wires are of adequate size and go directly to the davits, then the cantilever is relieved, and the hole becomes less of an issue.

I like the suggestion of welding in a piece of tube to reinforce the hole. Unfortunately this requires a skilled welder. Another possibility is to fit a doubler around the hole, with the doubler welded all around. (And the hole in the doubler could be smaller than 1 1/8). (Be aware that a bad weld can make the whole thing weaker rather than stronger.)

But I'm afraid I'd really have to see this and apply a load and see the reaction. If you were to test load the system, you'd want to assume a flooded dinghy (1000# at least) multiplied by accelerations from wave action (maybe 2G for a sail boat and 4g for a power boat.)

Also be aware that I would not even consider trusting advice (such as mine) from the internet on a project like this. I'd want to do all the math myself, or hand it over to someone who I trust to do so.

You could calculate the force at the hole by using the leverages involved. You might find that the aft side of the tub is being crushed under a load of 20,000 lb. Stick a piece of 2" tube (with hole drilled) under a press with that load applied (whatever it actually works out to be) and see what happens.

[Ken Fry]

Originally Posted by feudalkaos

Attached is a more accurate picture. In the previous pictures I had forgotten about the supports between the vertical and horizontal bars for the davits. You can see in this picture that there are supports welded between the furthest back horizontal pipe and the uprights. These are 1".

The davit was the original purpose I assume.

Jeez -- the supports are a critical piece of this -- even though they are poorly shaped. Ignore most of what I wrote previously.

[Icarus]

Looks ok to me

[Splashman237]

The tube you are concerned about forms part of what is called a portal frame across the boat . The corner you are concerned with will be taking some bending moment from the distributed weight of the solars. But not much in the same direction from Davits. Locally the bending stress from the incoming tubular will be trying the “crush ” the tube with hole in . This member with the hole in will in turn be spreading the stress out around itself as a it moves away from the cross member. You can assume a spread of 45deg) Solutions include welding a pipe into or onto the tube with hole in (as others have suggested) or creating a flat doubler ring around the hole and welding it in place , this will reduce the likely hood of the tube trying to crush. Overall It’s unlikely you currently have a problem . But piece of mind ....

[NCWDave]

I suggest you go to a muffler shop. Get a couple feet of 2' pipe, any material, and try to bend it. Drill a hole in it that size and bend it. If you feel you need to fix it decide how.
You can not simply weld a patch in the whole. Stainless pulls, bends, bad as it cools. Also you can not weld this open root without an inert purge inside. Cut it out and do 2 horizontal TIG welds with a backing like a chill ring. If purge / back gas is not possible do a closed root doubler. A 3 or 4" long piece of like tube cut length wise. Fit it, tack it and do 2 horizontal and 2 V up welds, a buff and your done. I spent about 25 years welding mostly stainless pipe for a living.

[thruska]

Warning warning !!!!
You must own a teeshirt that’s printed with the words :
Trust me Im an engineer,.
That’s required to allow you to comment in this thread ...

[thruska]

Originally Posted by NCWDave

I suggest you go to a muffler shop. Get a couple feet of 2' pipe, any material, and try to bend it. Drill a hole in it that size and bend it. If you feel you need to fix it decide how.
You can not simply weld a patch in the whole. Stainless pulls, bends, bad as it cools. Also you can not weld this open root without an inert purge inside. Cut it out and do 2 horizontal TIG welds with a backing like a chill ring. If purge / back gas is not possible do a closed root doubler. A 3 or 4" long piece of like tube cut length wise. Fit it, tack it and do 2 horizontal and 2 V up welds, a buff and your done. I spent about 25 years welding mostly stainless pipe for a living.

Dave i dont question your skills at all .
I think this ss tubing is similar if not identical to the same tubing uesed in dairy applications .
The amperages need is minimal, no ?
A purrge to slap in a simple gusset ? Really ?

Im surprised someone hasn’t suggested that the OP sell the boat , return to college for a 4 year course in bridge building. Then , an associate degree in shipbuilding. Reconsider his life skills and buy an rv before purchasing another boat. . Get employment at Boeing for several years . Then start designing boats and davit brakets.

Keeping in mind of course, the age old adage, ..Yes somtimes farts have lumps ....

[NCWDave]

Originally Posted by thruska

Dave i dont question your skills at all .
I think this ss tubing is similar if not identical to the same tubing uesed in dairy applications .
The amperages need is minimal, no ?
A purrge to slap in a simple gusset ? Really ?

Im surprised someone hasn’t suggested that the OP sell the boat , return to college for a 4 year course in bridge building. Then , an associate degree in shipbuilding. Reconsider his life skills and buy an rv before purchasing another boat. . Get employment at Boeing for several years . Then start designing boats and davit brakets.

Keeping in mind of course, the age old adage, ..Yes somtimes farts have lumps ....

Hi Thruska, re Paragraph 1; Yes to all except the gusset. The gusset is a closed root weld so internal purge would not be necessary. If it did sugar up on the back of the gusset when tacking clean it up and back gas the joint using a purge T and a gas box as you weld. This is really a simple weld for anybody that does much stainless. I would expect it to be done in 3 hours. Personally, just fix it. If it was mine I could not stand not to. As to paragraph 2; wtfe. I offer anybody interested with a professionals opinion on how to fix the pipe. Your lumpy farts are not my problem.

The quickest easiest way to close the hole and return strength, Have a stainless shop fab up a saddle gusset from stainless sheet. https://www.speedwaymotors.com/Roll-...xoCoy4QAvD_BwE