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  1. #31
    Join Date
    13th November 2009
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    Greater Chicago Area
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    Thanks. The one I didn't have was the color scheme from the Soviets.

    Greg


  2. #32
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    13th November 2009
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    I made some tweaks to the mold, so I think this is what I am going to start working on.

    Click image for larger version. 

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    I added a spot to add the shank and some vent ports. It may not be perfect, but I hope that it is good enough to get half of a Patriot fin.

    Greg


  3. #33
    Join Date
    8th May 2012
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    Southern, CA
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    6,101
    Nice work so far
    NAR # 89516
    HPR Cert Level 1

  4. #34
    Join Date
    13th November 2009
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    Greater Chicago Area
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    Block ready to become a Patriot fin mold, I hope.

    Click image for larger version. 

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    Greg

  5. #35
    Join Date
    13th November 2009
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    Greater Chicago Area
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    Well, I think I have a Pat fin mold for the B Side. It took about 6 hours to do, but all in all I think it came out pretty well.

    Click image for larger version. 

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    It may be hard to see, but there is a diamond shape there.

    Click image for larger version. 

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    Now I need to figure out the A Side.

    Greg

  6. #36
    Join Date
    13th November 2009
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    Both halves have been finished. They need to be sealed, followed by waxing and buffing.

    Click image for larger version. 

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    Here is a test fit of the halves. Looks ok so far.

    Click image for larger version. 

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    Maybe if this works I can make a nice set of V-2 and Mercury Redstone fins.

    Greg

  7. #37
    Join Date
    13th November 2009
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    Greater Chicago Area
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    I coated the finished mold halves with Aeropoxy laminating epoxy, mixed liberally with microballoons.

    I mixed up a 10 gram batch of Aeropoxy into a small plastic and thoroughly stirred it with a craft stick chucked into a drill press. The process that I used was to coat the mold with a chip brush then wipe off the excess with a paper towel. I did that process about 5 times, maybe more or less. One thing I did not want to do is to glop on epoxy and leave it, since that would destroy all the work to prep the surface. I made sure that the nook and crannies were as cleaned up as possible. The idea was to let it soak in and not puddle on the surface. Then I dusted microballoons onto the mold surface and then rubbed them into the surface, followed by wiping off the residue with a cosmetic cotton pad. I repeated this activity for about 3 cycles or so. The idea was for the microballons to attach to any small wet areas and fill up these small voids, thus smoothing the surface. Hopefully the surface will be sufficiently sealed for the waxing process, but that will have to wait. That's because I have set the mold halves aside to cure for about 2 or 3 days.

    Personally, I don't like this phase. It's boring, monotonous, and not enjoyable. That said, good results are always predicated on good prep work. Hopefully at the end of this process I'll have some cool looking Pat fins and have gained the experience to port them over to other projects.

    If anyone has a better process than what I have outlined that has worked for you, please let me know!

    Greg

  8. #38
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    13th November 2009
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    I did some test for the CR design and placement. I plan to use 1/8" hobby plywood.

    The fore is solid, whereas the aft has holes for mass reduction and venting heat.

    Click image for larger version. 

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    Greg

  9. #39
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    13th November 2009
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    These are the mold halves after the epoxy, wax, and PVA has been applied.

    After the laminating epoxy had cured significantly, the blocks sound more like ceramic than wood when they are brought together. I then buffed out the surface with 0000 steel wool.

    For the wax I used Partall #2 Mold Release. I think I put on about 8 coats or so of wax. The process was simple: Apply, buff, repeat.

    Click image for larger version. 

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    The surface is a little bumpy, but at least it will have the shape I was going for. Perhaps a bit of primer and sanding will clean it up some. If this works out then I may try poplar rather than MDF for future molds. But this is all part of learning about what works for me. Still looks pretty good for something so small.

    Greg

  10. #40
    Join Date
    25th October 2016
    Location
    Texas, United States
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    Wow! It looks amazing so far.
    The bumpy effect could be used for the fins on a V2.

  11. #41
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    13th November 2009
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    Quote Originally Posted by Incongruent View Post
    Wow! It looks amazing so far.
    The bumpy effect could be used for the fins on a V2.
    Thanks. You know you may be on to something with the V-2 fins idea.

    Greg

  12. #42
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    13th November 2009
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    I made a template for the fiberglass. I'm making it 1/16th inch offset from the edge.

    I included a scale to verify length.

    Greg
    Attached Files Attached Files

  13. #43
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    13th November 2009
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    I applied some 3M Super 77 (lightly, if that is even possible with that stuff) and set some light fiberglass on it.

    Click image for larger version. 

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    Then it was cutting out a couple of fin sides for the molds.

    Greg

  14. #44
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    13th November 2009
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    I then mixed up 8 grams of Aeropoxy laminating epoxy. I then thoroughly mixed it.

    I took the mix and poured 1.5 grams into a cup and mixed in a bit of fumed silica (for body) and milled fiber (for strength).

    I then took the mix and added it to one side of the mold. I just used a craft stick to move it around, with the idea that this would serve as a "skin" for the fin. I tried getting the excess off by using a craft stick and was successful for the most part.

    I repeated the process for the other side.

    I then let them to enjoy some sun.

    Click image for larger version. 

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    Greg

  15. #45
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    After sitting for about 1.5 hours, I added the fiberglass.

    I had to shoot about 3 shots of acetone onto the backing paper for it to release the fiberglass, so it was kind of like a sticky decal of sorts.

    I then placed the fiberglass on the mold halves. BTW, I'm thinking that this is all the fin needs for it to be sturdy enough. I don't plan to fly it any where near transonic, but I do want them to be a little robust where they can survive at least two flights without having to be replaced.

    Click image for larger version. 

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    After placing the fiberglass, I mixed up a similar epoxy batch for the "skin" but added a bit of microballoons as a lofting agent. I gooped it on to both sides with a craft stick and then joined the halves together. The idea was that it was going to be a little higher than the mold plane so the excess would be squeezed out. I expect there to be some flash, but it should be so thin that it can be easily snapped off or sanded off.

    I then added the 1/8" square tubing and placed it a fixture to orient it perpendicular to the X and Y planes.

    I then put a couple of small clamps on the mold halves and set it aside to cure.

    Click image for larger version. 

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    Hopefully, at the end of this process I will have a fin that is solid with no surface voids.

    Greg

  16. #46
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    13th November 2009
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    It was time to take out the fin from the mold.

    The first problem was that the square tube was up too into the fin.

    The second problem is that the halves didn't want to separate. That was a bit of a concern in that with all of the wax and mold release it should have been much easier than what I was experiencing.

    After getting a little radical, the halves separated. That left one side out but one side still in the mold.

    I finally got the fin out by putting a small allen wrench in the square tubing. There must have been a deficiency in how the wax and release was applied to one side of the mold because it took so much force to break it loose.

    So the results were mixed, with one side ok and another side damaged.

    Here are the results.

    Bad side.

    Click image for larger version. 

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    OK side.

    Click image for larger version. 

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    Because of the translucent material, the diamond wedge shape does not show up that well. The good news from the test is that it is there.

    So, I need to reevaluate to see if this is a material problem or a process problem, or perhaps both.

    Greg

  17. #47
    Join Date
    8th May 2012
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    Southern, CA
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    Greg - You are doing an outstanding job. Some hiccups along the way, but still very nice work. I wish ESTES would release their pro series patriot that had the air foiled fins.
    NAR # 89516
    HPR Cert Level 1

  18. #48
    Join Date
    18th January 2009
    Location
    Pittsburgh, PA or Cleveland, OH
    Posts
    809
    Definitely looks like a good first try! A lot of the aircraft guys use acrylic for their molds (or aluminum if you're made of money.) If you find you continue to have a hard time releasing, you may want to look into a mold material that can hold a better finish.
    Brian J. Guzek
    NAR#86418, L1
    Clubs: Pittsburgh Space Command, Mantua Township Missile Association, Wright State Rocketeers

    Competition Rocketry: Because three fins and a nosecone just doesn't cut it sometimes.

  19. #49
    Join Date
    29th March 2017
    Location
    I E So. Cal
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    27
    Great looking work so far Greg. I just built the current Estes kit with a 24mm motor mount and it flys great on the D12-5.


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