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Bore an 8" X 96" pipe?

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  • Bore an 8" X 96" pipe?

    Well I changed plans on the shop addittion, so I submitted a new set to the county and that is on hold for a bit. So then a local fisherman got a hold of me because he needs to change out his sonar unit. The old one gave up, so he bought a new one. The unit is installed in an 8", schedule 80 pipe that is welded to the lower deck and just in front of the keel. The problem is, the new one requires a 8.25" pipe. The boat is 86' long and he isn't schuled to have it hauled out for maintenance until next year. So he wanted to know if this pipe could be bored out with the boat in the water. It looks as though the lower 6' of the pipe are submerged at best. He thinks the tolerances on being true for the length of the bore would have to be within .050 of an inch. I have some pictures of what it looks like and of course want all the feedback I could get on if this looks feasible.
    This is looking down in the bilge at the transducer. You can see the flange on the pipe that it mounts to.


    Here is a better shot of the mount and pipe.


    This is a shot to show the clearance above the unit. There is about 3' from the flange to the steps.


    Here is a shot of the new unit with its flange.
    "Just build it and be done"

  • #2
    This one shows most of what the new unit looks like.


    Unfortunately, the flange is not very square with the pipe and I believe this is what caused the failure of the last one. It would need to be trued up so a guy could mount a boring set up to it.
    It would be an interesting project, my main concern is boring under water and not being able to see what is happening. Any help you can think of would be appreciated. Thanks, Jay
    "Just build it and be done"

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    • #3
      That doesn't look like 96" length of the probe, did you misprint that? Looks more like 36" fron the picts.

      I work on these some, the ones I am familiar with all have a "sea valve" at the hull, so you can pull it off the flange. Looks like this one doesn't? So the top of the flange is above water line?

      If I were to try to bore that, I would have an upper and lower bearing, cutting a hole in the steps to get the boring bare long enough to reach. As you said, it will be difficult to align the rig so you can keep on center of the pipe while boring, have to use the outside as a guide while setting up. Not easy.

      Steve

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      • #4
        If the emitter is smaller than the 8" ID,what about making up a new flange and 36" long top "can" and then cutting off and welding onto the old stem?

        If that were doable maybe make it a tight slip fit on the od of the old stem so it lines up straight before welding.
        I just need one more tool,just one!

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        • #5
          Instead of boring out an eight inch pipe, why not turn down a 9 inch pipe? It might be easier to have someone roll a piec of steel the right size.

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          • #6
            Fashion a cap with appropriate sealing material to fit the hull around the pipe opening. Have a diver take it down and hold it in place while you pump the water out of the pipe and the cap. Now it's dry inside the cap, and the water pressure holds the cap tightly in place. Use some long straps for insurance.

            Cut the hull around the 8" pipe with an O/A torch, and remove it. Fit the new larger pipe in place, and weld it to the hull from the inside. Remove the cap.

            It might be good to have a valve on the cap so you can fill the pipe with sea water to check for leaks before removing the cap entirely.

            Why in the world would they make the thing to require a non-standard pipe?

            Roger
            Last edited by winchman; 07-31-2008, 04:49 AM.
            Any products mentioned in my posts have been endorsed by their manufacturer.

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            • #7
              posting error please see entry below
              Last edited by derekm; 07-31-2008, 05:13 AM.

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              • #8
                easy but expensive

                I have a solution that works with the 3ft clearance , the 8ft pipe length, is self guiding, does not require a diver, but it does require 12ft of draft under the boat and the ability to make a 12ft shaft with keyway along its length. Its not cheap.

                It involves making a cutter head that travels along the driven keyway shaft. The shaft with a bottom bearing and spacer to fit the bottom of existing pipe size is "fished" into the pipe from underneath the boat (a rope work exercise).

                Derek

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                • #9
                  It's hard to imagine anything above it I wouldn't sacrifice to get working clearance. Good luck.

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                  • #10
                    Originally posted by derekm
                    I have a solution that works with the 3ft clearance , the 8ft pipe length, is self guiding, does not require a diver, but it does require 12ft of draft under the boat and the ability to make a 12ft shaft with keyway along its length. Its not cheap.

                    It involves making a cutter head that travels along the driven keyway shaft. The shaft with a bottom bearing and spacer to fit the bottom of existing pipe size is "fished" into the pipe from underneath the boat (a rope work exercise).

                    Derek
                    #1 My hope is that you have bilge pumps to take care of the water coming in if not.
                    #2 You have to be friend with the innsuranse company ( wery good friend)
                    #3 And all the guy's in the Coast Guard are your best friends ever
                    #4 Dry Docking not cheep but compared to #1-2, well....................

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                    • #11
                      well there is a way i can think of, but cant quite get my head around it right now too tired so ill check back tommorow, but it would depend on the current surface quality of the existing tube and also assumes that the opening of the tube is above water line.

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                      • #12
                        bore an 8" pipe

                        I would think if he can afford a sonar unit he could afford the haul out to install it correctly.

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                        • #13
                          Fab up a dummy tool, and measure the exact nominal ID clearances inside the existing drop pipe. Just might be a case where the brass looking thingy on the new sonde, presents the largest OD. Manufacturer would probably croak, if he found out 0.125 inches had been turned off his sonar tool OD?

                          Waterwell pump manufacturers are all the time skimming down the OD's of submerged vertical turbine pumps. Gotta make 'em fit. YMMV

                          G

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                          • #14
                            Originally posted by dsharp
                            I would think if he can afford a sonar unit he could afford the haul out to install it correctly.
                            Where does it say he doesn't want it installed correctly? I would think the results not the method would establish correctness.

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                            • #15
                              I went down to the dock to look at it again today. The owner was not there but one of his hands was. He said he thought the pipe was about 5' in length. That helps quite a bit, but the he said he thought all but about a foot of that was under water. They had a diver install a basketball type bulb to seal it off so they can take the old one out so when I get time I will get some shots of it out of the tube. The deck hand is from the east coast and he said what they do back there is along the line of what winchman said. Take a 55 gallon plastic barrel and cut it to the shape of the hull, seal it and run straps around the boat to help hold it. The boat is 82.5' long and is 25' wide on the deck. There really is a very good way to replace the pipe without dry docking it as it is in the engine room which is cramped at best and the deck you see in the hole where it is mounted is a sub deck. the deck is double there with about a foot between them and the front of the keel starts there also. I think if I can face off the flange, true to the pipe so I have a decent mount there ought to be a boring bar arangement that can be fabbed up. Bearings on each end sound very good. They have lots of heavy duty hydraulics on the boat already so it could be driven by that which would be nice to slow the cutter speed down without gearing and or belts. I guessed somewhere between 60 and 140 rpms depending on the type of tooling. I have a bunch of stellram that would work nice if the set up was ridged enough heavy cuts could be made. Sorry to be long winded, just some thoughts I had during the course of the day. As always suggestions are more than welcome here. Jay
                              "Just build it and be done"

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