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  1. #1
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    vintage astron alpha fin pattern

    so before I make a working copy of my original pattern sheet(you didn't think I was going to slice up a 40 yr old pattern sheet did you? )...should I make an extra copy or two?
    have to wait a bit for the nose profile the ca needs time to cure.
    rex


  2. #2
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    Yes indeed. The actual fin pattern page (SP-25) is missing from the K-25 Alpha data on the JimZ site and the Old Rocket Plans site doesn't have the Alpha at all.

    Bernard Cawley
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  3. #3
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    well since I don't have a scanner handy...*as it happens my neighbor does have a scanner and was kind enough to scan the sheet. enjoy
    rex
    *edit; most of orginal post no longer applied
    Attached Files Attached Files
    Last edited by Rex R; 10th October 2010 at 08:08 PM. Reason: added content

  4. #4
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    ahem

    check my previous post for the pattern sheet pdf

  5. #5
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    thanks for sharing this Rex!

  6. #6
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    Quote Originally Posted by BEC View Post
    Yes indeed. The actual fin pattern page (SP-25) is missing from the K-25 Alpha data on the JimZ site and the Old Rocket Plans site doesn't have the Alpha at all.
    I checked www.spacemodeling.org/JimZ/estes/K-25.pdf and there is a fin template on page four of the instructions in pdf.

    I printed out a copy from Jim Z's and a copy from Rex R. The copys were layed one over the other, held up to a window and compared. While the templates are very close, they are not a spot on match. I would go with the fin template that comes from the instructions myself. Thanks Rex R.
    The process is continuous...

  7. #7
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    methinks those instructions are not from the same time frame as mine, one set is 'newer'/more recent than the other. which is which is anyones guess. I did verify that the pdf file I have prints a faithful copy to the pattern sheet I got from my (previously) unopened kit.
    curious as to changes,how did they differ?
    rex

  8. #8
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    Quote Originally Posted by Rex R View Post
    methinks those instructions are not from the same time frame as mine, one set is 'newer'/more recent than the other. which is which is anyones guess.

    If your kit cost more then $1.50, you can be sure it's the newer one (bradycros).



    I did verify that the pdf file I have prints a faithful copy to the pattern sheet I got from my (previously) unopened kit.



    curious as to changes,how did they differ?

    A picture is worth a thousand words. Print them and compare (bradycros).
    Bradycros
    The process is continuous...

  9. #9
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    You're right, they don't match. I've known there were at least two variations on the Alpha fin shape for awhile, but I didn't know where they diverged. Now, thanks to that SP-25, I think I do.

    That "your first rocket" instruction sheet on JimZ is not from a K-25 Alpha kit but a separate publication. It appears in "The Alpha Book of Model Rocketry", which has a 1972 copyright date in the form available on the Ninfinger site HERE. It's page 10 of the document.

    The rest of the instruction set there matches a set I still have from when I built my first Alpha in the late 1960s. Notice that the engine mount assemblies are quite a bit different between the first and second appearances of the exploded view on the JimZ site as well.

    I matched the SP-25 scan above with an Alpha III fin can and it is just about a perfect match. That surprised me, I have to say.

    Current-issue Estes Alpha kits have laser cut fins which are also that slightly higher span and aspect ratio fin that matches the Alpha III and therefore also what's in the SP-25 rather than the "your first rocket" fin pattern on JimZ different still, and slightly smaller in span and chord.

    Interestingly, the laser cut K-25 fins available from Semroc match the "your first rocket" pattern exactly (so my Alpha II clone has that fin shape).

    So it appears to me that the divergence came all the way back at the issuance of the K-25 Alpha kit rather than when the Alpha III came out (which is what I had assumed before). Interesting indeed.
    Last edited by BEC; 11th October 2010 at 12:04 AM. Reason: further confusion!
    Bernard Cawley
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  10. #10
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    Quote Originally Posted by BEC View Post
    You're right, they don't match. I've known there were at least two variations on the Alpha fin shape for awhile, but I didn't know where they diverged. Now, thanks to that SP-25, I think I do.

    That "your first rocket" instruction sheet on JimZ is not from a K-25 Alpha kit but a separate publication, though someone else will have to identify it.

    I matched the SP-25 scan above with an Alpha III fin can and it is just about a perfect match. That surprised me, I have to say.

    Current-issue Estes Alpha kits have laser cut fins which are also that slightly higher span and aspect ratio fin that matches the Alpha III and therefore also what's in the SP-25 rather than the "your first rocket" fin pattern on JimZ.

    Interestingly, the laser cut K-25 fins available from Semroc match the "your first rocket" pattern exactly (so my Alpha II clone has that fin shape).

    So it appears to me that the divergence came all the way back at the issuance of the K-25 Alpha kit rather than when the Alpha III came out (which is what I had assumed before). Interesting indeed.


    Huh? Er,...Ah, yeah, of course, what else would it be?
    The process is continuous...

  11. #11
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    Yeah that was a bit rambling. Let's try again in a more linear fashion and I edited it a couple of times after you posted.

    It now appears to me there are at least three variations on the Alpha fin shape. The first is from the K-25 kit (and the SP-25 pattern posted above). It's also a very close (but not exact) match to the Alpha III/IV plastic fin can shape.

    The second is from Model Rocketry Technical Manual as it appeared inside the 1970 Estes catalog, as shown here and also appended at the end of the Alpha .pdf file as posted on JimZ here. This second shape is what you get when you order laser cut K-25 fins from Semroc.

    The third is the current shape as it comes in Estes Alpha kits today. This third shape has about 1/16 inch less chord and 3/32 less span than the SP-25 shape but otherwise matches well. An image comparison of the second and third shapes is the last image in this post on YORF.

    This makes me wonder if Rex could put a measured 1 inch line on the SP-25 and rescan it so we can be sure that we're printing it to the correct size, though after cutting out the fin marking pattern and trying it on a BT-50 I'm pretty sure it's right as it is.

    All this is getting pretty deep into the minutiae I have to admit.....
    Last edited by BEC; 11th October 2010 at 01:21 AM.
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  12. #12
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    [QUOTE=BEC;136361]

    That "your first rocket" instruction sheet on JimZ is not from a K-25 Alpha kit but a separate publication. It appears in "The Alpha Book of Model Rocketry", which has a 1972 copyright date in the form available on the Ninfinger site HERE. It's page 10 of the document.

    QUOTE]

    The ninfinger site has the page number as 10, the jim z site has the page number as 58. The text on each page is different also, but the text in both tells you the astron alpha is available in kit form. I belive the instructions on jim z are the ones that came with the original kit. Pages 10 and 58 are illustrations out of different publication. Since the kit with instructions and the illustrations would have been from the same era, I'd bet on that fin template being right.
    Last edited by bradycros; 11th October 2010 at 12:51 AM.
    The process is continuous...

  13. #13
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    Quote Originally Posted by bradycros View Post
    The ninfinger site has the page number as 10, the jim z site has the page number as 58.
    Good catch! Yes, continuous indeed.....

    FOUND IT! Page 58 of the 1970 Estes catalog - also on Ninfinger HERE.

    Updated the prior post with the right info.
    Last edited by BEC; 11th October 2010 at 01:21 AM.
    Bernard Cawley
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  14. #14
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    Quote Originally Posted by BEC View Post
    Good catch! Yes, continuous indeed.....

    FOUND IT! Page 58 of the 1970 Estes catalog - also on Ninfinger HERE.

    Nice find! Are we in agreement on the fin template now?
    The process is continuous...

  15. #15
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    I'll see what I can do. the price listed on te instructions is $1.50...but that doesn't narrow down the exact date much since $1.50 price ranged from '67-70. my mmt has the wide centering rings and no retaining band for the hook.

  16. #16
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    Quote Originally Posted by bradycros View Post
    Nice find! Are we in agreement on the fin template now?
    Agreement on what? There are now at least two different templates "out there" and at least three actual shapes since current laser-cut Alpha fins don't match either template.

    I'm about to take a comparative set of images for the thread on YORF. I'll post it here, too.
    Bernard Cawley
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  17. #17
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    Quote Originally Posted by BEC View Post
    Agreement on what? There are now at least two different templates "out there" and at least three actual shapes since current laser-cut Alpha fins don't match either template.

    I'm about to take a comparative set of images for the thread on YORF. I'll post it here, too.

    Only if you have a bionic eye like a T-3, would you detect such small differenes. Us ordinary humans will not see such small differences, or care.

    I'm going with the template on jim z's.
    The process is continuous...

  18. #18
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    oh my..., had I known this was going to happen...I probably wouldn't have offered.

  19. #19
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    Please....don't be concerned. Some of us just go kinda crazy with this sort of minutiae and you've actually been very helpful since I, for one, have been hoping someone would share the real SP-25 template for some time and I much appreciate it.
    Bernard Cawley
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  20. #20
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    comparitive views

    If you really don't care, there's no need to look at these pictures.

    For the rest, here are comparisons between the SP-25 scan that's the genesis of this thread and the "Handbook of Model Rocketry" template from the middle of the 1969 (and a few following years) Estes catalogs and which has been substituted for the SP-25 itself on the Alpha listing on JimZ.

    The first is a composite comparing both ways. The second shows the SP-25 pattern laid next to the JimZ/HMR pattern. All were downloaded today and printed with scaling turned off from the same printer.

    I have pics of the cut out SP-25 template laid on an Alpha IV fin (it's black, easier to see than the orange Alpha III) but the differences are much slighter than between these two variations.

    Rex, thanks again for filling in the missing piece of the puzzle from the source of the original information - a vintage Alpha kit's bag.


    Added: I just remembered. I have a 1970 catalog that I bought on eBay some months ago. I don't need to use the scan of that page 58 - I have the real deal in hand. Need to take another picture. BTW, a comparison of my cutout shown in the two images already posted and the catalog page shows a good match - so the JimZ/Ninfinger scan is correctly sized.

    BRB....
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    Last edited by BEC; 11th October 2010 at 03:38 AM.
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  21. #21
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    if it helps; the lines on the 'theme paper/notepaper' are 9/32" apart(average, note pads are not noted for precise lines).
    rex

  22. #22
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    More direct comparison

    Quote Originally Posted by Rex R View Post
    if it helps; the lines on the 'theme paper/notepaper' are 9/32" apart(average, note pads are not noted for precise lines).
    rex
    YES, that helps a great deal. And I've measured my printouts and I get that value as well. I'm convinced that the scan is printing out correctly.

    Here's one more comparison - a cutout from a printout of your SP-25 scan (now confirmed to be correctly scaled) laying on a genuine 1970 catalog page - the same one scanned and posted with the Alpha kit data on JimZ.

    If we could somehow get Jim's attention I would submit that your scan, Rex, should go in place of that catalog page he is now using. He even says on the kit list page that he needs a copy of the fin pattern sheet SP-25. Unfortunately, I've not had any luck with the email JimZ link on his site.

    Just to be clear about it: The fourth page of the .pdf that is posted on JimZ for the Alpha is almost certainly page 58 of the 1970 catalog, NOT the template sheet from the kit from whose instructions pages two and three were taken. The fact that it is "page 58" should make it obvious that it is not from the kit. I have the original instructions from my original Alpha. Pages two and three of the JimZ .pdf match them. Rex has now filled in the missing piece of information which should supersede what is in the JimZ .pdf. The page that links to the .pdf says "Need SP-25" over in the fin template column.
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    Last edited by BEC; 11th October 2010 at 07:26 AM.
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  23. #23
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    just to add to the confusion, each of those patterns was likely hand drawn...then 'photographed', I doubt that the original template was saved after the paste-up. later patterns were likely measured from an existing alpha so errors could easily creep into production with each new printing plate(with perhaps an attitude of, thats close enough, print it). but since each pattern came from estes as an alpha fin they are all 'correct'. it isn't until one has more than one generation in hand that the differences become apparent.
    on a side note; while I intend to build mine 'stock'...I do find that some things will be done a tad differently(engine block, not going to trust a 40 yr old 'rubber band(thats too short) or the adhesive on the same vintage tape strips, and then there is the kinda short shroud lines...).

  24. #24
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    Yeah...and then each of us cut out those patterns with whatever skills we did or didn't have, transferred them somehow to balsa, and again cut with whatever skills we had or didn't have.....so expecting the fins to all match within a laser-beam's width is pretty unrealistic.

    Even so, I thank you again for getting me (and others, I hope) back closer to the original starting point with the posting of your scan. At least we can then strive to cut down on the "generation loss" as we recreate things fondly remembered.

    Truth be told, there's a Kevlar line tied to the top of the engine hook for shock cord anchorage and an engine block in the mount tube inside my Alpha II clone. But on the outside it looks as close to original as I could make it at the time by using the Semroc laser cut fins (which we now know are the same shape as that catalog page) and the Semroc interpretation of the BNC-50K which looks more "right" to my eye than the BMS cone of the same number or any subsequent cone, notably the plastic one that comes in current-issue Estes Alpha kits. With your SP-25 scan I might get a little closer next time around.
    Last edited by BEC; 11th October 2010 at 07:25 AM.
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  25. #25
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    [QUOTE=BEC;136451]

    Yeah...and then each of us cut out those patterns with whatever skills we did or didn't have, transferred them somehow to balsa, and again cut with whatever skills we had or didn't have.....so expecting the fins to all match within a laser-beam's width is pretty unrealistic.


    QUOTE]

    People tend to cut on the outside edge of the drawn lines that make up a template. By tracing around the template onto choosen fin material with a pencil and again cutting to the outside of the drawn lines, you've increased the size of the fin anywhere from one to several millimeters.

    Then someone comes along and copies that fin, repeating the process. Now the measurments are just 'off' enough to be detected by just looking at the fin.

    Suggestion: cut on the inside of the line drawn on the fin material.
    Last edited by bradycros; 11th October 2010 at 12:05 PM.
    The process is continuous...

  26. #26
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    updated scan

    as requested an updated scan w/ 1" scale lines, note; I have not tried printing this one.
    rex
    Attached Files Attached Files

  27. #27
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    D motor

    Anyone ever build one of these and stuff a 'D' motor in and fly it?

  28. #28
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    Rex, thanks for the updated scan.

    dlazarus....why? Getting one back when flown on a C is quite a challenge as it is...... One would need to check for stability as well.
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  29. #29
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    Wow....and I thought that I was obsessive!
    Mark S. Kulka NAR 86134 L1, ASTRE 471, Adirondack Mtns., NY
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  30. #30
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    Quote Originally Posted by MarkII View Post

    Wow....and I thought that I was obsessive!
    I was just pushing buttons.

    Last edited by bradycros; 13th October 2010 at 04:01 AM.
    The process is continuous...

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