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Tool time.

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  • #76
    Hello David and all.

    David I have a couple of questions for you regarding my tooling for the upcoming project 667. I am on the cusp of producing some silicon moulds for the 667. The rear appendages and some of the reactor coolant scoops. However I will soon also be creating the moulds for the stern horizontal planes. As you know the 667's stern planes featured fences, (plates at either end of the movable surface.) I am concerned about how to best arrange them on my moulding board arrangement and designing the mould to eliminate the possibility of trapped air bubbles in the outer edges of these really thin sections. I have never moulded parts with such thin plate sections before and I am concerned that because of their thin-ness they may be susceptible to bubbles if the air venting is not well designed and I think this could be greatly helped by their orientation.

    This first picture shows my typical mould board set up with the movable surface with the leading edge upwards. The sprue (dark shaded in section) attaching to the leading edge where the foil is thickest. The thinking being that the plates are pointed upwards therefore allowing one vent placed at the top tip of the plate to allow air to move out as the resin fills up. The downside is that the resin will be pouring into the mould immediately over the brass rod insert, thus hampering a clear open space to pour into. What do you think of this?

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    Second photo shows the movable surface in the more conventional position that I would usually have it with the plates in a horizontal position, My concern being that the air will not be able to escape out the sides of the mould as my vent lines only really run up the split surface. Should I be concerned about extra venting lines or is it really in your experience, not an issue? This is how I would prefer to mount the piece as it allows the brass insert to be away from the pouring sprue. It also means I can have the air vents on a easily sandable flat surface rather than on the curved thick end of the foil.


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    Or is this all not really an issue?


    Second point.


    This has to do with you Fin build on the November class that Scott is developing. I really wanted to see what happened with the rest of the Sail/ Fin fabrication. The reason why I am so interested in this is that I am considering a one piece mould for the 667's fin. However I am thinking of creating a moulded part but out of Glass rather than moulding it out of Polyurethane.. You got up to splitting the mould in two with a knife and then were about to lay up cloth and then that's where I was left hanging....


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    I am thinking of producing my 667 fin mould as a one piece exactly like above however instead of cutting it in two, just brushing in gel coat and then layers of cloth. I am going to have to make a added section on the rear of the sail to create void where the missile deck would be and to make sure that the piece could be pulled out. I hope this makes sense. Do you see any problems with this?



    Regards,

    David H

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    • #77
      I would cut down int the number of vents you are using. I try to position the parts as such that I only need one vent. For the hinge for example if you angle the part you will not need a vent at the hinge.

      Below the mould I made for the new diveplanes I did for the AKULA, only one vent/part.

      Grtz,
      Bart

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      Practical wisdom is only to be learned in the school of experience.
      "Samuel Smiles"
      http://scale-submarine.com/index.html

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      • #78
        Hello David,


        Iím gone back to looking at vac pumps and am confused by the stats needed. I realize 29 inches of mercury and also -1 bar with about 8 CFM. However when I look up pumps, they all say how many cfm but none tell the amount of vacuum pulled in any meaning ful reference I can get my head around.They certainly donít mention 29 inches or -1 Bar , they may mention microns. Iíve looked up conversion scales but Iím just getting more confused. Any further advice?

        regards

        David H

        Comment


        • #79
          Originally posted by Davidh View Post
          Hello David,


          Iím gone back to looking at vac pumps and am confused by the stats needed. I realize 29 inches of mercury and also -1 bar with about 8 CFM. However when I look up pumps, they all say how many cfm but none tell the amount of vacuum pulled in any meaning ful reference I can get my head around.They certainly donít mention 29 inches or -1 Bar , they may mention microns. Iíve looked up conversion scales but Iím just getting more confused. Any further advice?

          regards

          David H
          I've seen the same things on 'new' pumps I've been pricing (the one I've got and is still working is nearly 40 years old and I bought it new); nothing I've looked at denotes degree of vacuum expressed in inches of Mercury. WTF!? I blame you metric-tramps across the waters for this horrible situation. A pox on your houses!

          OK, that out of my system Ö...Ö.

          Kevin Rimrodt is a calibration technician. If there's a conversion scale that converts microns per whatever-to-inches, he's the guy. I'll get back to you, Dave.

          David
          "... well, that takes care of Jorgenson's theory!"

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          • #80
            Thankyou David.

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