A 29mm bird (littleK38) that will challenge you and costs $30 in basic parts.

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RecoRocket

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What I present here is 38mm AF bird, with a 29mm MMT, that can do dual deploy in a park, and fly on motors up to a L1 cert motor (H128), and only costs about $30 in basic parts. Anyone interested in his? I'm a long term L3 and this is the bird to be used in demos for schools and sout groups for a demon.. I'll add the rocksimefile for this now, but DO NOT start building based on his If you order the parts, the MMT, CR's, coupler-payload, NC, are all LOC stuff, while the bulkheads are PML (there is a reason for this!). I did also use PML for the SC.

Should I go on with building a L3 style bird that flies with a F40 (or an H)? Here is the rocksim:
View attachment my_LittleK38.rkt But do not build yet!

TTW fins made from 1/8" plywood, and the proper way to build (throw out the instruction you get with most kits.)
 
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I think cheap scratch builds are good for people getting started with there first scratch build . Think it good for the kids , tough and it will go high
 
Let's get started. Here's the parts list, source, and cost (in advance, I'll say I probably forgot something!) There are a few options based on what you have on hand)


**********LOC Parts:
------------------------------------------------------------------------------------------------
Qty | Item # | Description | Price Each | Total Price
------------------------------------------------------------------------------------------------
1 | BT-1.52 | 1.52" (38mm) Airframe/MMT Tubing | $6.88 | $6.88
(Tube is 34" and will be cut)

1 | MMT-1.14 | 29mm Motor Mount Tube | $4.68 | $4.68
(tube is 34" and will be cut)

1 | PNC-1.52 | 1.52" (38mm) Plastic Nose Cone | $13.81 | $13.81

1 | PL-1.52 | 1.52" Payload Section | $5.72 | $5.72
(10" BT, 4" coupler, bulkhead, and screw eye. There is an extra 9" of BT-1.52 when you cut it to size which
can be used for the payload section, but you will still need a coupler)

1 | FCR-1.52-1.14 | Package of 4 Fiber Rings 1.52-1.14 | $4.62 | $4.62
(Only two needed, but sold in a pack of 4)

1 | RA-29L | 29mm Quick Change Motor Retainer Assembly | $27.00 | $27.00
(This is for a full aeropack 29mm set. I've never used the Estes 29mm retainers, and you might
consider that to save money)

------------------------------------------------------------------------------------------------

**********PML Parts:
5 STRP-0.375 $1.31 Strap, nylon, 0.375 $6.55
(this is the price for 5 yards - more than you'll need!)

2 BP-1.5 $1.63 Bulkplate, 1.5 $3.26
(these are bulkheads that are the size of the outside of the coupler, not the ones to fit inside the coupler)

**********Missileworks Parts

RRC2+ 38mm Li-Ion Modular Sled System
SKU MS38-R2_Li
Weight 0.50lbs
Sled Essentials "Value Pack": Add (2) Elevator terminals, Switch, Save $1

Quantity: 1
Price (each): $15.45

(you'll also need the RRC2+ itself, and the Li-Ion battery and charger - there are links for these on the missileworks site)


**********Misc Stuff
rail buttons,
#6 t-nuts (I used the ones from Lowes with a flat flange -one reason is that they will fit inside a standard size railbutton),
misc screws, washers and nuts,
#8 all-thread,
1/8" birch plywood (fins)
Epoxy, CA, JB Weld
 
Ok step one. Time for cutting and sanding.

1) Cut the 29mm MMT to the correct length - One of the CRs can be used to define the actual cut, and then a sharp knife or a small tooth back saw can me used to make the cut. Now, some layout is needed on this tube. First, lightly sand it, as that will make the epoxy bind better. Also sand the inside and outside of the CRs for a good fit in the MMT, as well as inside the AF. If you are using a motor retainer dry fit it it on one end, and draw a line around the length needed to be exposed to secure the retainer much later on. Also draw lines around the CRs, with the rear one placed leaving room for the retainer, and the front one leaving about 1/8" for a fillet. Notch the front CR to allow the 3/8" TN SC to go against the 29mm MMT. You want it to be tight, but not so tight as anything gets pushed out of round. lastly, draw 2 lines 3/8" apartn along the entire length to mark the location where the SC will later be secured. You'll want to know this when the MM is later secured.

2) cut the fins. The fins in the rocksim file I posted are TTW, and you can export the template there. Cut the fins with the leading edge along a "factory edge" on all three fins running with the grain, as that will give you a consistent edge on one side. I used a sharp hobby knife for this, and a small tooth back saw at times. When all three fins are done, clamp them together using the "factory edge" and sand the other edges so the fins are all the same.

3) cut the fin slots in the air frame, Lay out lines along the AF for the three fins. Use your favorite method to do this. The cut starts 3/4" from the rear, and are 6" long. I use a dremel with a cutting wheel, and the AF secured with something like a band clamp. If you mess up, turn the tube around, as there will be 9" of AF cut off when this is done! If the slots aren't quite perfect or wide enough, you can use a sharp knife to clean them up. You can dry fit the MMT and CRs at this time to insure the fins fit, and you may want to mark the fin and the slot, so that later, fin 1 goes in slot 1, etc. Remove the fins and the CRs/MMT. and the draw a line the full length of the AF right in the middle, between two of the fins. This will be used to position the rail buttons. Then, dryfit the MMT and CRs again, using the marks made earlier, and mark the position of the CRs on the outside of the AF, along the line drawn for the rail buttons.

Now a bit of a soapbox about rail buttons. Use a rail when ever possible! You'll get no "rod whip", and will never worry about getting a pad with the proper rod. I use 1010 size. Some vendors supply their rail buttons with a wood screw, and tell you to secure them to a CR with a bit of epoxy. Throw away the wood screw and use t-nuts! You don't want to have to retire a bird because a rail button broke. With the t-nut approach, you can just replace the rail button.

I'll talk more about attaching the t-nuts later on, but for now, we just need to drill a couple holes. Along the line for the rail buttons, mark a location in front of the position of both CR, leaving enough space for the flange on the t-nut. Then drill a hole there that allows the neck of the t-nut to pass through (tight is ok, as you'll see later!). And soon you'll see why I like the #6 t-nuts at Lowes. And you never want to build so a rail button can't be easily replaced.

Now you can cut the main AF to the proper length (I used 25") and if you were good on your fin slots, this will give you a 9" section for the payload bay....

In my next post, epoxy is involved!
 
OK, the first epoxy part if the build. It will be to attach the front CR and SC. The rear CR is NOT involved, and if you attach it now, you're screwed!. There are marks on the MMT for the front CR (notched), as well as lines for the SC itself. You want about 3" of the SC against the MMT. Use 15m epoxy for inside of the front CR, and the "inside" of the SC where it hits the MMT. (align the SC with the two lines drawn when prepping the MMT).

Now here's a tip. Put epoxy on top of the SC for that 3". Then take a piece of wax paper, and lay it over the top of the SC, and wrap the area tight with masking tape. (Epoxy doesn't stick to wax paper). after the proper time for setup, remove the tape and wax paper (you'll see the TN is bound all the way to the MMT and smooth). After all is set, apply a filet to the joint between the inside of the top CR and the MMT, and when that's set, the bottom of the front CR and the MMT. For the filets, the SC can be threaded thru the MMT to keep it out of the way....

The end result here, is the MMT, with the front CR and SC attached, and fillets where the MMT hits the front CR...
 
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I made something like this ..with almost the same build of materials...I call it the Black Ops .

It is designed just to present a similar shape as a true min diamer counterpart for testing fit and flight of electronics and recovery...but in an 'almost' minimum diameter - meaning it has a mmt to keep the shock cord mount and motor retention simple .

Used kevlar harness as a bridal, blue tube coupler, acme rail guides fiberglass fins and an Estes retainer as a psuedo tailcone with the LOC parts.

Kenny

1409207296199.jpg

1409207326381.jpg
 
I made something like this ..with almost the same build of materials...I call it the Black Ops .

It is designed just to present a similar shape as a true min diamer counterpart for testing fit and flight of electronics and recovery...but in an 'almost' minimum diameter - meaning it has a mmt to keep the shock cord mount and motor retention simple .

Used kevlar harness as a bridal, blue tube coupler, acme rail guides fiberglass fins and an Estes retainer as a psuedo tailcone with the LOC parts.

Kenny

The Acme guides are great on a min-dia bird, but they do drag a bit on the rail. I've only used then when there were no other options.

And using Blue tube, G10 fins and the estes retention gave me a a question. If you build the rest with the "good stuff", why not use the "good stuff" for motor retention, where, if the motor retention fails, you could lose an expensive case (and possible the whole bird). I don't know of any plastic that holds up well when it really close to a motor or blast deflector...

Ok, back to the build. I've mentioned the #6 tnuts from Lowes before, and here's why I'll get into the specific way to install them in this bird, but for now, you want to make sure you have t-nuts that will do this:
T-Button.jpg The t-nut fits inside the railbutton for all but 1/16" inch of the length....

Now to take advantage of this. How I mount these t-nuts:

Take a #6 screw, and slide on a rail button, and dip the screw thread in Vaseline (this is important!). Then poke the screw through the hole you drilled for the button. Using tape on a stick or some other method, get the t-nut to line up and connect with the screw. Start to tighten the screw. Wht happens, is the collar (theaded) part of the T-nut will come through the bt, and the rail button will be flush. Do NOT over tighten!

Now why the Vaseline is needed.. You be applying epoxy on the inside of the BT to secure the t-nut: top, between the t-nut and BT, etc.. - the Vaseline keeps the epoxy from attaching to the threads on the screw, so the screw can be easily removed.

My next thread will be specifics about how to mount the t-nuts on this design. The forward T-nut is installed using the method I describe here, but the rear t-nut is different. Do NOT install the rear t-nut!
 
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Does the T-nut go through the wall or is it surface mount? I usually use well nuts which seem similar to what you're describing, in that they can be unthreaded and replaced if the buttons break.

BTW, the motor retainers hold up fine unless they are within an inch or two of the blast deflector, I see a lot of people (including me) use clothespins or clips the hold the rocket a few inches up away from the deflector. The aeropack is great though for durability, especially on rockets that land on the engine mount (like the madcow DX3).
 
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Does the T-nut go through the wall or is it surface mount? I usually use well nuts which seem similar to what you're describing, in that they can be unthreaded and replaced if the buttons break.

BTW, the motor retainers hold up fine unless they are within an inch or two of the blast deflector, I see a lot of people (including me) use clothespins or clips the hold the rocket a few inches up away from the deflector. The aeropack is great though for durability, especially on rockets that land on the engine mount (like the madcow DX3).

With the Lowes #6, the column of the t-nut passes through the BT, and about 1/2 of it will be inside the rail button It provides a great deal of strength to the button, and allow you to replace the button in seconds if it gets damaged...
 
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I've been known to use a c-clamp as a rail stop for my high power birds. I don't need/want to blacken the paint on my rockets...again.
Rex
 
Here's a picture that shows the completed bird. For the picture, I separated the playload section a bit and you see where the coupler is. In front is altimer, sled, and endcaps for the altbay (which is in the coupler)
full-1.jpg
 
I've been known to use a c-clamp as a rail stop for my high power birds. I don't need/want to blacken the paint on my rockets...again.
Rex

Nice flight - sparky motors can be fun! I use various methods to support rocket, including a clamp or just a screw and wingnut in the rail itself. As you fly larger motors, it's next to impossible not to get some blowback from the delector. I have a picture of one of my M flights leaving the rail, where a there's a 4-5' flame clearly visible, for example.
 
Ok, after the top CR has cured, it's time for a dry fit for the aft rail button t-nut. Slide in the MMT, at an angle, and see if you can get the aft t-nut to it's hole in the BT. If not, you may need to cut a bit off the end. Keep trimming the t-nut until you can it to the hole, and also make sure you can still put a screw in it!

Take out the t-nut as well as the MMT.

Epoxy time! Spread epoxy inside the BT, above the fin slots, where the forward CR will be. Then side the MMT into the BT, but only far enough so that the aft t-nut can get to it's hole, with the MMT angled. Use a screw to pull the t-nut thru the BT (you want to use a 3/8" screw for this, and a railbutton ot allow it to fit.

Then,slide the MMT all the way to the epoxy, and with the lines from the SC mount, align it so that the SC is between two fins . Make sure that the read of the motor tube is at the proper length for motor retention, etc, and use the (dry) rear CR to center the MMT. But only insert it about 1/8" of an inch so it can be removed.

When the front CR has cured, remove the rear CR, take the screw from the aft t-nut, dip it in Vasoline, re-install the screw, and epoxy the t-nut on the inside of the BR. After that epoxy has cured (the screw must still work!), put the aft CR back in 1/8" of an inch or so. Next post will be installing the fins.

Side note. When you use a AT 29 40/120 reload, understand that you may get a larger ejection charge (BP) than you need for your flight. This is not always a good thing. If you use too large a charge, you could blow apart your SC or bird, with what could be a "good flight" otherwise. In a real case, for this bird, the amount of BP that comes with a 29 40/120, is almost twice what's needed. (it's based on the diameter and length of what you need to pressurize, so a 1.5" diameter need less BP than a 2.26 diameter at the same length). That's one of the reasons that I don't fly SU - you can't adjust the size of the charge with a SU!
 
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Now the fins. for the first attachment, this is one place I'll go with 30min epoxy, as it's stronger than 15m, and also gives you a bit more time to align the fins. On this build, I used a piece of foam board, with slots for the proper fin locations and a center hole to go over the BT. Cover the roots with enough to secure the fins, insert them in the slots, and use your preferred method to align the fins, and keep it that way until the fins are fully set. Then, remove the rear CR and apply inside fillets (it is a bit tight!). When all has set, epoxy in the rear CR, making sure there is enough of the motor tube exposed to attach the retainer after it's painted.

Just as a teaser, here is the bird on the pad, with a F40w-10, using motor eject. It simmed to about 1700' .The "10" was a bit long of a delay, I used an X form 24" chute, and the walk to recovery was maybe 100'. There was a scratch on the tip of the NC, as you can see, it didn't land on soft grass!
Lk38.jpg

Extra points if anyone can ID the pad I'm using! Hint, you can attach all three legs together and it becomes a carrying tube for launch rods!

At this point, you can build the payload bay in the standard way, and only fly motor eject - or you can wait and read how to add an altimeter and set this up for dual deploy!
 
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Here are a cople views of the alt bay. First, and outside view: (Please note, the black twistie in the picture is only in the pics so nothing rolls off the desk!)
DSCN0563.jpg

It's a 4" coupler, with #8 all thread to hold the sled. The screw in the picture is to attach the altbay to the payload section (I just put in the screw so I could ID the hole - the screw will actually be thru the payload section BT and into the coupler) (there is another 180' away), and the other hole is for access to the switch and to vent the alt bay. On each end, there is a small hole to pass the ematch directly to the altimeter in the bulkhead. The nuts/washers on the aft end are epoxied in place. Access to the altbay will be from the nuts on the fore end.

Now here are the guts:
DSCN0564.jpg

I'm using a Missileworks RRC2+ altimiter, with MissileWorks 38mm Li-Ion sled (and switch!). You can also see why it uses bulkhears that are the diameter of the outside of the coupler. Using a dremel in a dremel router/shaper table, on 1/2 of each bulkhead,I created a lip so that it acted as a cap and would center the bulkheads in the coupler. To do this, only trim a bit at a time, until it fits, and then cut the second with the same setup. Drill the holes in the bulkheads for the allthread (1" apart). Like I said, I epoxied the nuts/washers/locknuts on the aft end, but the fore end is secured with a nut/washer/locknut, and when cutting the all thread, make it long enough!

You'll notice the altimeter is pushed towards the aft end, and secured with a nut on the all thread. This does two things - it insures it's aligned with the hole for the switch, and it also provives room in the front for the t-nuts used to hold the altbay to the payload section.

Get the bay built, but do not drill holes for the switch and t-nuts yet When attaching the eye bolts (I used machine thread and not wood screw eye bolts. with a flatnut to hold it).

Size up things and mark on the coupler where the switch hole needs to be, and the space where the t-nuts/screws can be(make sure that the hole for the tnut isn't too hight, as you need it to fit (maybe trimming the flange) so that the fore bulkhead will still fit. Mark the center of the coupler, and then use that as a reference make to mark the BT of the payload section for these localtions (the coupler/alt bay, will be 1/2 in the payload bay, and 1/2 in the main BT). Extend the marks for the screws and switch abound the BT, and draw lines at 0' and 180' along the entire length of the payload BT (you want these marks at the nose cone - more to come later!)

Without the sled and the electronics, put together the alt bay, and slide it to the 1/2 way mark. Tape it, and the drill holes at the location for the tnuts (#6 screws) That way, the payload BT and coupler are alaight. Make one side of the BT and coupler so that you can align it later in the same way.

Now, #6 tnuts will be epoxied inside the coupler. Take the alt bay apart and clean the 2 holes. Then using the tnut figure out of part of the flange needs to be trimmed to allow the bulkhead to fit, as well as what space might be needed to allow enough thread in the t-nut (I used a small washer for this), and epoxy the tnuts on the inside of the coupler, using the Vaseline/screw method described above, When all is setup, grind/cut the column on the t-nuts until it can fit inside the payload BT, and using the mark make earlier, align the tnuts to their proper hole,a and use two #6 screws to make sure everything aligns...

Now, drill the hole for the switch/vent at the location marked before, through the BT and coupler.
 
BTW, on the first altimeter flight (single deploy), the MW altimeter only reported about 1100', so it seems that the Sim calculation was off. The weight in the program was off by an ounce based on real weight (paint, etc came into play), and I needed to add over 6 ozs to the sim weight to make the number right (which is wrong!). Anyway, it was a good flight, and I could see ejection as soon as it "tipped over" and this with about 1/3 of the BP that comes with a 40/120 reload stored away in a container for a flight that needs more BP than comes with a reload....

I flew in a grassy park, so I ended up with mud on the tip of the nosecone (it's covered the scratches at the tip from landing in a desert using motor eject!) :) No other damage.
 
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