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  1. #211
    Join Date
    18th December 2010
    Location
    Maryland, 20794
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    487
    TRF,

    Today we started booster construction. Beginning with a glued and screwed thrustplate we inserted fiberglass longerons. Then we dropped formers down securing their locations with squeeze clamps. Next we applied stringers. We have about half of the stringers fully seated. Will have to pick up the work again after Thanksgiving.

    Have a great holiday everyone and thanks again your interest.

    Feckless Counsel

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  2. #212
    Join Date
    22nd August 2015
    Location
    Rhode Island
    Posts
    1,143
    Wow. That’s about all I can say. This is incredible.


    Sent from my iPhone using Rocketry Forum

    NAR #100940, RIMRA & CMASS
    L1 - 4/17/16, Tyrannosaur (by Binder Design), Loki H144
    L2 - 8/19/17, Terrordactyl (by Binder Design), CTI J250

  3. #213
    Join Date
    18th December 2010
    Location
    Maryland, 20794
    Posts
    487
    TRF,

    We spent an entire session, about 6 hours, planning and fabricating a fixture to apply fiberglass skins. The fixture is pictured below. It's four spokes made from 3/4 plywood. Spokes are double stacked making them a rigid 1-1/2 inch thickness. Two additional plywood blocks form a center hub that, when joined to the spokes, is 3-inches through. The center hub slides tightly over 2-inch square steel tubing. Holes at each spoke-end receive fiberglass stubs left proud of frame’s end.

    This arrangement is remarkably rigid, straight and square.

    We have arranged a number of tables ahead of the fixture to outfeed our G10 fiberglass sheet. Recall those are 96 x 48 x 0.010 inch sheets. Four sheets encircle the frame with about 6 inches overlap and half inch overhang either end. We are not sure we should bond all four sheets before wrapping or apply them one at a time.

    Tomorrow should be an exciting day.

    Feckless Counsel
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  4. #214
    Join Date
    10th July 2007
    Location
    Melbourne, Australia
    Posts
    1,267
    Great progress!
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  5. #215
    Join Date
    20th February 2009
    Location
    Cayuga, Indiana
    Posts
    12,894
    I'll be honest, none of this wood framework is worth sh!#. It all depends on how you build the frame to framework barrier. Pls move this build along so I can give some real feedback. Right now you have nothing that will fly.

    From the Ether...
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  6. #216
    Join Date
    18th January 2009
    Location
    Virginia - Central
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    3,999
    Quote Originally Posted by dixontj93060 View Post
    I'll be honest, none of this wood framework is worth sh!#. It all depends on how you build the frame to framework barrier. Pls move this build along so I can give some real feedback. Right now you have nothing that will fly.

    From the Ether...
    "the frame to framework barrier"

    Could you expand a bit on that...?
    I've not build a hollow frame structured rocket , so I'm not familiar with all the terminology ...I think I saw a smaller balloon open frame structured scale project at an LDRS (Orangeburg SC IIRC)...it had exterior paneling the length of the airframe.
    We got two categories of pilots around here. We got your prime pilots that get all the hot planes, and we got your pud-knockers who DREAM about getting the hot planes.
    Now what are you two pud-knockers gonna have?... Huh?”
    Pancho Barnes-
    The Right Stuff
    http://www.mwavs.com/0053148414/M4RS...udknockers.m4r

    Tripoli #2747

  7. #217
    Join Date
    18th December 2010
    Location
    Maryland, 20794
    Posts
    487
    TRF,

    Today we applied fiberglass skins to a central airframe section. First order of business was to plane stringers fair to formers. Next methyl-methacrylate adhesive was applied to one quarter of formers and stringers. A sheet of 96 x 48 x 0.010 inch fiberglass is lowered onto the adhesive. Alignment marks help prevent sliding about that would otherwise disturb appropriate glue lines and fillets. Sheets are applied one at a time until all quarters are covered.

    Since fiberglass sheets are translucent bond lines can be inspected from both inside and outside. Pictured below are central lines externally viewed, edge lines externally viewed and central internal lines.

    Final picture is an airframe section complete except fine trim and decorations.

    Feckless Counsel
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  8. #218
    Join Date
    19th February 2017
    Location
    The world, probably
    Posts
    466
    Quote Originally Posted by Feckless Counsel View Post
    TRF,

    Today we applied fiberglass skins to a central airframe section. First order of business was to plane stringers fair to formers. Next methyl-methacrylate adhesive was applied to one quarter of formers and stringers. A sheet of 96 x 48 x 0.010 inch fiberglass is lowered onto the adhesive. Alignment marks help prevent sliding about that would otherwise disturb appropriate glue lines and fillets. Sheets are applied one at a time until all quarters are covered.

    Since fiberglass sheets are translucent bond lines can be inspected from both inside and outside. Pictured below are central lines externally viewed, edge lines externally viewed and central internal lines.

    Final picture is an airframe section complete except fine trim and decorations.

    Feckless Counsel
    I think the definition of a really impressive project is one you can stand inside... Can't wait to see this all put together!

    Sent from my LGL44VL using Rocketry Forum mobile app
    NAR #104043

    crmrc.org

  9. #219
    Join Date
    30th January 2016
    Location
    US > OK > NE
    Posts
    3,479
    That's a big ol' lantern!

  10. #220
    Join Date
    20th February 2009
    Location
    Cayuga, Indiana
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    12,894
    Quote Originally Posted by MaxQ View Post
    "the frame to framework barrier"

    Could you expand a bit on that...?
    I've not build a hollow frame structured rocket , so I'm not familiar with all the terminology ...I think I saw a smaller balloon open frame structured scale project at an LDRS (Orangeburg SC IIRC)...it had exterior paneling the length of the airframe.
    Any square frame structure by itself can easily be distorted. A semi-monocoque design implies a stressed skin in tension to make the structure rigid. Only until that skin is attached properly, do you have anything useful that can actually be tested. In the above post I misspoke, I meant to say skin to framework barrier.

    From the Ether...
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  11. #221
    Join Date
    18th December 2010
    Location
    Maryland, 20794
    Posts
    487
    TRF,

    For those interested we have a brief update on progress the last ten days.

    Pictured below are three complete airframe sections. Those are center of the rocket. Each measure 53 x 96 inches. We’ve not weighed them but estimate is 60 pounds each. Overhung edges are trimmed flush using a laminate router. We are quite happy with those pieces. They are clean, square, plumb and quite rigid.

    Capsule is frame rebuilt. Fiberglass tubing is added to better tie the parachute canister. Stringers were recut with slots angled one degree both sides. That gave the assembly some “lead-in” which kept the stringers loose until seated. Was not an easy assembly but, given improvements and the previous experience, was achieved in about four hours.

    Tower knuckles are complete. Those are manufactured from Nylon powder using selective laser sintering (SLS). We have cut all fiberglass tubing and assembled the tower. It is dry fit as pictured below.

    Feckless Counsel
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  12. #222
    Join Date
    27th January 2009
    Location
    Oregon
    Posts
    2,168
    Love the tower knuckles, looks great. How's the weight compared with the estimate/plan for the fuse sections?

  13. #223
    Join Date
    20th February 2009
    Location
    Cayuga, Indiana
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    12,894
    Quote Originally Posted by Feckless Counsel View Post
    Pictured below are three complete airframe sections. Those are center of the rocket. Each measure 53 x 96 inches. We’ve not weighed them but estimate is 60 pounds each. Overhung edges are trimmed flush using a laminate router. We are quite happy with those pieces. They are clean, square, plumb and quite rigid.
    Fleckless, those look great! Any validation testing planned on the completed articles?
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  14. #224
    Join Date
    16th March 2009
    Posts
    496
    Awesome work! This is the coolest build thread on TRF in years. Looking forward to seeing the flight in person.

    Todd

  15. #225
    Join Date
    18th December 2010
    Location
    Maryland, 20794
    Posts
    487
    Frank,

    Yes! The knuckles came out great. We are really lucky to have access to that equipment along with its world class operator. Weight relative to the CAD model is a good question. If memory serves 60 pounds is about predicted. We will report out the details as we get into the CG measurements.

    Todd,

    Is great to hear from you. Thanks for your kind regards. Know you are a propulsion guy. We have a full scale motor test upcoming. Let’s make sure you are part of that?

    Tim,

    Glad to know you see promise in those pieces. They are a bit expensive for destructive testing so we are sticking with the usual but unscientific “man handling.”

    We appreciate your comment on semi-monocoque construction. No triangles. No structure. Properly bonded skin is the crucial element that “triangles” the fame together. To that end we believe we have a well bonded skin of high tensile strength and low elongation at break.

    More interesting is your statement, “A semi-monocoque design implies a stressed skin in tension to make the structure rigid.” That generated a set of inquiries because our skin is not pre-stressed. That is to say our skin is not shrink tightened as in UltraCote or Ceconite.

    This link to “How It’s Made” shows an aircraft wing made from square frame and skin that is NOT pre-stressed. I hope that informs an understanding of our construction.

    Feckless Counsel


  16. #226
    Join Date
    20th February 2009
    Location
    Cayuga, Indiana
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    12,894
    But Fleckless, is it not stressed with the force vector lateral and outward due to the "pull" of the bent G10 skin? And likely fairly balanced/distributed around the frame structure. I am not a mechanical engineer but not seeing why the skin would need to exert an inward force.

    From the Ether...
    Last edited by dixontj93060; 10th December 2017 at 02:23 AM.
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  17. #227
    Join Date
    31st December 2009
    Location
    Las Cruces, NM
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    1,421
    A stretched skin made of non-rigid material will only provide tension, not compression. The skin tension is only good in one direction, too. For example, you can twist and compress a thin aluminum can or a water bottle. If something has a "space frame" with stringers in both tension and compression, it will hold up to twisting forces and unequal compression forces.
    -John

    NAR/TRA L3
    My LinkedIn Profile

  18. #228
    Join Date
    10th July 2007
    Location
    Melbourne, Australia
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    1,267
    A very stiff skin when not stressed will very quickly provide opposing force when the frame is distorted slightly. The stiffer the skin, the less distortion required for the same reactive force.

    Prestressing (tension) works well for things that are not good in compression, like glass and concrete.

    The designers need to make sure it is supported in the required directions appropriately.
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  19. #229
    Join Date
    18th December 2010
    Location
    Maryland, 20794
    Posts
    487
    TRF,

    Forward and aft recovery sections are ready to skin. Those cap ends of three airframe sections. Total length of the assembled airframe is about 34-feet.

    As pictured below 1/2-13 recovery attachments are installed using LocTite backed by 1/16 stainless cotter pins. Threaded rod and nuts are grade 8. Washers are 2-inch diameter unrated zinc steel. Brass electrical contacts are installed through the bulkhead. Plywood dividers assure no electrical shorts from quick links, swivels or other metallic components. Parachute canisters are 17-inch inside diameter and 36-inch depth.

    Feckless Counsel
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  20. #230
    Join Date
    20th February 2009
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    Cayuga, Indiana
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    12,894
    I'm having a hard time picturing where that last hard point attachment is... Does the picture show the mid plywood piece before the chute tube was installed? i.e., is it sitting in the bottom of central tube?

    From the Ether...
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  21. #231
    Join Date
    31st December 2009
    Location
    Las Cruces, NM
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    1,421
    The recovery attachment point is a single point of failure. No good reason not to have at least two harness anchor points for something that heavy.
    -John

    NAR/TRA L3
    My LinkedIn Profile

  22. #232
    Join Date
    20th February 2009
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    Cayuga, Indiana
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    Quote Originally Posted by jsdemar View Post
    The recovery attachment point is a single point of failure. No good reason not to have at least two harness anchor points for something that heavy.
    I was going there, but trying to understand the reinforcement mechanism for what looks like a wide span across of a couple layers of plywood.

    From the Ether...
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  23. #233
    Join Date
    30th January 2016
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    US > OK > NE
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    That eye nut caps the threaded rod, unless I miss my guess. The washers and nuts then support the midspan of each "level".

  24. #234
    Join Date
    18th December 2010
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    Maryland, 20794
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    487
    Tim,

    Correct. That is mid-plywood before the parachute canister is placed. Note mid an upper plywood are 12mm thick while lower plywood are 6mm. There is a 6mm pedestal at parachute canister base making the local thickness 18mm.

    Dhbarr,

    That is the correct stack-up. Since three members are linked in bending the system is minimally identical to a single piece of 12 + 6 + 6 = 24mm piece of plywood and a 1/2-13 eyebolt. You accept that that or no?

    Gents,

    Understand your concern for the parachute attachment. That design cannot fail.

    There we did a lot of work both hand calculation and CAE. We calculate 4G load on the attachment equals 30MPa stress at the 18mm thick middle diaphragm right round the eye nut’s washer. According to Handbook of Finnish Plywood 25MPa is the “characteristic” compressive strength of 18mm plywood meaning 95% of all plywood samples test higher.

    We also debated the issue of single and multiple attachments. Our conclusion is single or multiple attachments are equivalent given correct physics of design.

    Nevertheless caution is warranted. We will rework our numbers. More on that next post.

    Feckless Counsel
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  25. #235
    Join Date
    31st December 2009
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    Las Cruces, NM
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    Quote Originally Posted by Feckless Counsel View Post
    We calculate 4G load on the attachment ...
    Why do you think there will only be a 4-g load?
    -John

    NAR/TRA L3
    My LinkedIn Profile

  26. #236
    Join Date
    15th March 2016
    Posts
    339
    I don't buy that you can add the strength like that. One will see stress before the rest. In addition, the thin plates will flex further before failing. You need to look at the preload of the tie rods to make the most of the strength of all three.

  27. #237
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    18th December 2010
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    Maryland, 20794
    Posts
    487

  28. #238
    Join Date
    20th February 2009
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    Cayuga, Indiana
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    Quote Originally Posted by Feckless Counsel View Post
    There are a few people "down under" that would dispute the "largest model rocket" claim:


    http://www.youtube.com/watch?v=xzcxEXHdHx0

    From the Ether...
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  29. #239
    Join Date
    27th August 2011
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    West Tennessee
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    2,707
    Quote Originally Posted by Feckless Counsel View Post
    Something tells me they will not use this is their resume folders.
    It is amazing what you can do when you don't have a choice.

    Smart people learn from their mistakes.
    REALLY SMART PEOPLE learn from OTHERS' mistakes.

  30. #240
    Join Date
    31st December 2009
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    Las Cruces, NM
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    1,421
    Quote Originally Posted by Feckless Counsel View Post
    In what context are you including that flight? I am familiar with that project (the motor was stored at my place).

    -John

    NAR/TRA L3
    My LinkedIn Profile

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