Estes 7240 Honest John Build

Discussion in 'Scale' started by Bruiser, Aug 3, 2018.

  1. Aug 3, 2018 #1

    Bruiser

    Bruiser

    Bruiser

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    Well I have officially started my Honest John build. I had posted a thread about some potential mods suggested some time ago by another modeler here: https://www.rocketryforum.com/threads/7240-honest-john-mods.147178/ but I didn't get any replies about the suggestions so I am undecided about how to proceed in that area. I'll tell you this though--I hardly ever leave anything alone :)

    I started on the fins yesterday and they are all sanded. I had thought about building it into the small fin version for something different but I like the big fins :) Now I have to decide on where to go with them from here. I though about papering them but when I wrapped paper around them they lost all the definition of the facets... I am thinking about using Miniwax water based polyurethane on them. It is pretty popular in the R/C world to hold on fiberglass or even tissue. They say it's much easier to use than resins. I haven't tried it yet so it may be about time. It should both seal and strengthen them.

    HoJo Sanded Fins.jpg

    Thanks for reading my post,
    -Bob
     
  2. Aug 6, 2018 #2

    Lugnut56

    Lugnut56

    Lugnut56

    What, me worry?

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    I'm also currently working on this kit. After doing some more research on other builds of this rocket, I realized I had put more of a rounded profile instead of a sharp profile on the wings. I saw on Chris Michielssen's site "http://modelrocketbuilding.blogspot.com/2015/11/estes-honest-john-7240-build-part-8-fin.html" how he used CWF to build up along the seam to make the wedge shape more pronounced . I wasn't going to try and correct this, but the wedge shape does look really good.
     
  3. Aug 7, 2018 #3

    Rainmaker

    Rainmaker

    Rainmaker

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    I use the minwax on fins and balsa nose cones all the time and it works very well.
     
  4. Aug 7, 2018 #4

    Bruiser

    Bruiser

    Bruiser

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    Lugnut, I had read Chris's build back a month or so ago and had forgotten how he used the CWF to build up the fin a little for a more pronounced seam. I was thinking over the weekend that if I am just going to coat the fins with WBP, it might be best to first coat them with CWF to get them nice and smooth before sealing them with the WBP.

    Rainmaker, thanks for the endorsement on WBP. I bought some over the weekend. Now I am deciding on going with CWF, sanding, then WBP or if I am going to skip CWF and just glass them with 3/4 ounce cloth and WBP. Right now I'm thinking glassing is over kill for this rocket...

    I started on the fin can and it was much herder to cut out than I thought it would be. The plastic on mine was pretty thick and I used up two razor blades cut out the slots. Not something to be in a rush doing... I need to get out my Dremel tool and sanding drum to room the "flashing" from the front and rear of the can, then it will be ready for the engine mount. Well it doesn't want to upload the file. Not much to see anyway, but pictures are good :)

    I also started on the engine mount but I am out of Titebond so I need to make a run to the store. I swung in WalMart Friday after work to pick up some Elmer's CWF and Titebond but they don't carry them. I did get the Miniwax Water Based Poly though. Guess I'll try Lowes today for the glue and filler.

    -Bob
     
  5. Aug 8, 2018 #5

    Bruiser

    Bruiser

    Bruiser

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    I worked on the engine mount and fin can since the last post. I ground off the lip from the ends of the can with my dremel tool until they were flush with the inside wall. I sanded the inside a little so the glue would grab on when I attached the engine mount.
    Fin Can.jpg


    I glued the rings on the engine mount tube and added the engine block in. After everything set up I tried to install the engine mount in the can but it wouldn't go in. I tried sanding the inside of the can with my dremel but I was afraid to go too deep so I started sanding the rings on the engine mount. I finally got the lower ring to go in the can, but then it was getting hung up on the top ring, so I sanded the top ring until it would go in. It still wouldn't go in all the way as there was a large "bump" on the inner wall of the can right at the location the lower ring would glue at. I went after it with my dremel until I was able to slide the engine mount to the required position. I glued the can in with epoxy because using wood glue to attach cardboard to plastic didn't seem like a great idea to me...
    Cone with Engine Mount.jpg


    I also worked on the fins a little. First I applied some CWF but it is different now. This one changes color when it dries. I don't know if they still make the old one but I couldn't find it. This new filler did work just like the old one for me. Added a little water, brushed it on, waited for it to dry and sanded. I did one side at a time and did not have any warpage issues. I have put on the first coat of water based polycrylic and that went fine. I will let it dry overnight before I sand and apply the second coat. This is my first time using it so hopefully it will seal and strengthen the fins like I hope.
    New Cwf.jpg


    So these steps were probably about the last steps where I stick to the instructions. I have to decide about the nose cone mod within the next few days...

    -Bob
     

    Attached Files:

  6. Aug 10, 2018 at 4:43 PM #6

    Bruiser

    Bruiser

    Bruiser

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    Past the point of no return...
    Nose Cone Cut.jpg


    I decided to go ahead with the nose cone mod from my other thread. So now the main body tube will continue thru the spin motor section of the rocket. The warhead will also have a section of body tube just over 3 inches in it and I will glue the end of the original nose cone inside it so the warhead will become the new nose cone.

    I am working on making centering ring now to keep the body tubes centered where I cut apart the spin motor from the warhead. I am making them from some 1/8" basswood I have left over from my IQSY bash build. It really surprises me how much this basswood bends. I've worked with harder balsa...
    Centering Rings Pattern.jpg


    Here I have the outside cut down and sanded.
    Centering Outside Sanded and Stacked.jpg


    -Bob
     
  7. Aug 10, 2018 at 9:09 PM #7

    Bruiser

    Bruiser

    Bruiser

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    Been getting some more done.

    I got the outside of the centering ring sanded down with my Dremel and I have glued them together with just a few drops of CA to hold them while I cut out the middle with a hole saw on the drill press.
    Centering Outside Sanded and Stacked.jpg


    Here they are after the drill press and some work with the Dremel tool.
    RIngs Ready.jpg


    Next was to get them on the tubes.
    Rings on Tubes.jpg


    Then it was time to glue on the spin rockets
    Spin Rockets Glued.jpg


    And the warhead
    Warhead Glued.jpg


    I am waiting for the epoxy to dry so I can do some sanding. Once I am satisfied with the fit, I'll glue the nub(?) into the warhead.
    Nub.jpg


    Time to go work on primering some fins...

    -Bob
     
  8. Aug 11, 2018 at 3:38 PM #8

    Mugs914

    Mugs914

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    Looking good!
     
  9. Aug 13, 2018 at 8:51 PM #9

    Bruiser

    Bruiser

    Bruiser

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    I have the nub glued on. It's a little loose in the body tube right now but I still need to coat the inside of the tube with some thinned epoxy. I think it'll be just right.
    Nub Glued.jpg


    I've also been working on the fins. They are really giving me a hard time. I used the CWF, sanded then followed by two coats of the water based poly. Sanded that and primed. I needed a little more CWF so I put that on, sanded and re-primed. Wet sanded the primer to be ready for paint. I think I sanded a little too much and must have exposed the balsa because things got hairy. Ended up priming again, doing some filling with CWF, sanding and priming, repeating until I had to say that's enough. Then I taped off the lower part of the fin and primered the top again. When I peeled off the tape, I now have a nice, crisp line there. I was tempted to lightly sand it, but decided not to as I didn't want to wipe it out. One pass of primer isn't too thick...
    Primered Fin.jpg


    I broke one inner lower tip off while pulling off the tape so it's in the repair shop. While that dries, I decided it was time to glue a fin on the can so I got out my high-tech alignment device.
    Alignment Tool.jpg


    I hope to get one other fin on today. I'm using epoxy but it does seem to take longer than usual to set. It's a new tube so I think it's just the humidity we are having. New Mexico isn't use to that :)

    -Bob
     
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