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Moebius Skipjack

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  • Apply filler, sand, apply cloth/epoxy, sand, apply epoxy, sand, apply glazing putty, sand, apply glazing putty again, sand. That's what I've been doing the last few days.

    The filler and epoxy has eliminated the ridge between sections and now as expected have to deal with ridge between the epoxy and polystyrene. These differences are not noticeable in the pictures but they are there. Smoothing this out is accomplished with glazing putty and sanding and feathering. Once sanding is done I expect to see bands of glazing on either side of the hull seam.

    The gaps in the corners where the upper and lower sections meet were also eliminated. See previous pictures.

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    Arrows are about where most of the glazing putty will end up.

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    More sanding to do here. Two of those openings were covered up, will open those up again.

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    Anxious to get this over with and get on to other more interesting mechanical bits.

    Comment


    • Originally posted by Ken_NJ View Post
      First coat of cloth/epoxy is on and drying. Iām looking way ahead. What paint, manufacturer, should I use? I have a new airbrush I can use. Iād assume most of the paint should be flat? Not sure the zinc chromate is available?

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      invest in this system: Ultra 9K Waterborne Refinish System | Automotive Finishes (sherwin-williams.com)

      Accept no substitutes!

      David
      Resident Luddite

      Comment


      • David,
        Is this a newer paint that you are using? What made you move to this brand (other than it works)?
        If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

        Comment


        • Originally posted by trout View Post
          David,
          Is this a newer paint that you are using? What made you move to this brand (other than it works)?
          Those ****-head, liberal, tree-kissing, liberal weenies in California saw to it that the refinish industry dropped their lines of hydrocarbon based coating systems and went the water route. Sherwin-Williams developed a water-based, two-part chemistry (Ultra 9K) to replace the earlier enamel, lacquer, urethane, alkali, epoxy systems.

          I'm not using it yet, but will have to switch to this nature-loving, politically-correct, Greenpeace approved, wok crap when I run out of my current stock of Chromacolor and Chromaclear urethanes.
          Resident Luddite

          Comment


          • Made the z cuts on the lower forward section and aft upper section. Cuts came out clean and true. Just needed slight sanding to remove the cuts marks.

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            Finished sanding the irregularity between the lower hull sections. Applied about 5 layers of glazing to build up to get it as even and feathered as I can. I think it came out well. Cut open the two holes that were covered by the epoxy and cloth.

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            Have the strap hold down in place. Relocated the aft screw, see location in above picture. Screws were covered with CA and baking soda and sanded smooth.

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            Ribs were cut open on the top and bottom hull sections to facilitate water draining and allow air bubbles to flow out.

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            Attached Files

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            • Since I'll have a mechanism to open the torpedo doors, it may need service at some point. I added these ribs to the upper section and two to the lower section. They will be tapped for 1-72 screws.

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              The brass screws were ground flat and the round edges were squared up so they will sit so they are level with the hull surface.

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              Like so.

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              Once pilot holes were drilled thru the hull side and ribs, they were drilled again for the tap size. The ribs were tapped. The hull hole was opened up for a loose fit. Then the outside hole was countersunk so the screw sat flush with the hull exterior.

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              At this point the seam was sanded so the two hull sections were just about invisible.

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              Interior shot showing the torpedo doors and ribs holding the upper and lower hulls together.

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              Four screws will be hardly visible on the outside and 2-56 machine screws hold the aft section together from the inside.

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              Now I can finally start work on the fun part. The mechanism to open & close the torpedo doors!

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              • Problem. The instructions say use a 8-1/4 inch tube to make the shaft. That size tube causes the end of the SD to fall between the studs in the lower hull. So I need to extend the length of the tube by about 7/16" like Tom did. That moves the SD up before the studs.

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                Whatever the shaft length is to move the SD, the post from the shock absorber falls between the drain holes in the ballast tank. What to do here? Drill a hole in the SD to accommodate the shock absorber post? There is no mention in the instructions about this. What have others done?

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                Comment


                • Originally posted by Ken_NJ View Post
                  Problem. The instructions say use a 8-1/4 inch tube to make the shaft. That size tube causes the end of the SD to fall between the studs in the lower hull. So I need to extend the length of the tube by about 7/16" like Tom did. That moves the SD up before the studs.

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                  Whatever the shaft length is to move the SD, the post from the shock absorber falls between the drain holes in the ballast tank. What to do here? Drill a hole in the SD to accommodate the shock absorber post? There is no mention in the instructions about this. What have others done?

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                  Move the shock absorber as required and drill a new hole for the indexing pin.

                  David
                  Resident Luddite

                  Comment


                  • I have the shock absorber permanently mounted in place. Would required much ripping things apart to get it out. Guess a small hole for the pin is the only option.

                    Comment


                    • Yes, put hole for pin.
                      That is what I did.
                      If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                      Comment


                      • Been working on the torpedo door opening mechanism the last 2 weeks! Lots of plastic and brass shaping and soldering. I'll eventually have a more in depth process on my web site when I can get to it. To spare you those details here's the 'finished product'. Well almost, will get to the almost later. This is a multi-part post. You can see as the main rail is pulled back the doors open. There are holes at the back of the main rail which attached to another mechanism that pulls and pushes that main rail. The rods coming off the Du-Bro connectors allow adjustments to be made to each individual door.

                        Top hull is the upper one.

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                        This is the upper hull.
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                        This is the upper hull.
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                        This is the lower hull.
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                        This is the lower hull.
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                        • This is the makeup of the main rail. It has a 1-72 rod between them with a lock nut. Rotating the rail to the right allows alignment between the holes for the next mechanism.


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                          The pins on this mechanism join into the holes on the main rail. The larger rod is for the bell crank from the servo. The square tubes allow the one to slide in and out of the other.
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                          The idea is as the servo pushes or pulls the nylon arm, it moves the pins which control the position on the main rail opening the doors. The arrow points to a hole which can be used if I need to fine tune the alignment between the upper and lower rails. Doors are in the closed position here.
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                          Doors in the opening position.
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                          Closed position from looking aft. This is the upper hull which is upside down. The nylon arm will connection from a servo.
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                          Hull halves together right side up. You can see how the pins slip into the top and bottom rails. This allows me to have the upper and lower parts of the hull separate to service all this stuff. Doors closed.
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                          Doors open
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                          • Here's the problem. And I thought I would have a problem at this point. Everything moves smoothly by themselves. I added Teflon grease on all moving parts. When the pin is at either end of travel, there is enough friction that prevents the rail from moving easily. It's all a combination of the pin moving the rail. I tried adding a spring, it helps a little but not enough. Any ideas to overcome this issue?

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                            One spring helps a tiny bit. Maybe add another spring at the arrow?
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                            Need some mechanically minded minds on this. Where Manfred? I know he has done many things like this.
                            Last edited by Ken_NJ; Today, 03:48 PM.

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