L3 Project - 8" AGM-33 Pike

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mtnmanak

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I am finally progressing on my Level 3 project to build an AGM-33 Pike. Mostly it is a Madcow version with a number of custom CNC'd parts.

This rocket has some well-trod ground for build threads. The ones from Robertv2 (2015) and AllDigital (2016) have really helped me out. Their build threads can be found here:



My build is following those threads pretty closely, so not sure anyone wants to see another build thread on this rocket. If anyone is interested, I am happy to post the build here since I have to document it for my TAPs anyway. If not, when it is complete, I will post the documentation to the L3 thread and people can download that.
 

Adam3836

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Please post your build thread here.
Iam always up to see everyone’s build threads especially some cool L3 builds
Looking forward to seeing your work
Good luck
 

Adam3836

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Lol awesome let’s see what ya got going
 

Alby

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My build is following those threads pretty closely, so not sure anyone wants to see another build thread on this rocket. If anyone is interested, I am happy to post the build here since I have to document it for my TAPs anyway. If not, when it is complete, I will post the documentation to the L3 thread and people can download that.


Post it. I'm building a 4" AGM-33 Pike, but pretty much tossed all the parts in the kit except for the fins. I'm using BlueTube 2.0 and several plywood bulkheads to secure the motor tube and fins vs. the (2) that come in the kit. I've also used a couple of paint sticks and clamps to make sure the fins (since they are separated) are correctly aligned while the epoxy sets.


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mtnmanak

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Note at the start: This build is in progress and everything posted here has already been approved by my TAPs.

This project is an AGM-33 Pike Level 3 certification project consisting of an 8-inch diameter G10 fiberglass airframe and a 98mm motor mount. It is a combination 3-fin design, with 3 trapezoid 8 inch long straight fins in the rear and 3 swept trapezoid 27 inch long straight fins forward. It includes a payload section for main chute recovery gear and dual deploy recovery. Topped with a 5-1 ogive aluminum tipped nose cone, giving the rocket an overall length of 145 inches. Dry weight, including recovery gear and electronics, will be about 75 pounds.

This rocket will employ standard dual deploy, with a 24” Cert-3 drogue chute deployed at apogee and a 36” pilot chute at 1000 feet that will deploy the main parachute, a SkyAngle Cert 3 XXL, from a deployment bag. For the certification flight, there will be a Marco Polo tracking device in the nosecone.

Planned Certification motor: Aerotech M1780NT
Projected Max Altitude: ~2300 feet AGL
Drogue deployment: Apogee
Main deployment: 1000 ft. AGL

Parts List and components (epoxy and hardware weights to be updated throughout the build):

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Theory

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She’s gonna be a beast!

going to have all of that M1780 right in your face. Should be epic!!!!
 

mtnmanak

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Here is the current Rocksim file and the dry and loaded weight drawings from Rocksim. These will change throughout the build, so I guess I will edit this post, if I can, to update as I go along.

Overall Dimensional Drawing:

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Figure 1 – Dry weight diagram

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Figure 2 – Loaded weight (AT M1780)
 

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mtnmanak

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Some notes about the materials and parts listed above before I start the assembly photos / comments.

Although the airframe components (body tubes, nosecone and fins) are from Madcow, I replaced or added everything else. I used my Shapoko 3 CNC router to fabricate 56 parts for this rocket. This took me quite a few months since I was only able to dedicate some time on the weekends for most of the past year or so. I spent a lot of time designing and trying out parts in cheaper materials such as plywood before committing the designs to aluminum and fiberglass. While the kit Madcow sells is a great kit and has most of the parts you would need to complete a build like this, since I got this CNC router, I tend to buy the kits as a convenient way to get the bulk parts. A lot of discussion in these forums revolves around using a kit or "scratch" building. I have found that, even if you have a scratch built design or aspirations, you can find many of the parts you want much cheaper in a kit. In this case, the normal price Madcow sells this kit for is already a modest cost savings over buying the component parts individually, but I got the kit on their last Black Friday sale for 30% off, which also meant about 40% off buying the component parts separately. So, even though I had planned from the beginning to ditch many of the parts and make my own, it was worth it to plan ahead and buy the kit on sale just to get the bigger airframe parts. As a bonus, you don't have to slot your own airframe! Another thing to consider is that the individual components are often not available. As I write this, Madcow currently shows this kit as available for purchase, but the 8" airframes, the 8" nosecone, the 4" motor mount and the 8" couplers are all out of stock. So, if you wanted to build an 8" scratch rocket right now, buying this kit would probably be one of your only ways of getting the parts from Madcow at the moment.

The CR's I made have slots for both upper fin guides and lower glue wells, (the spanners for which were also CNCed) and also have holes for all-thread which will be used primarily for adjusting the CRs precisely, but also add some structural value.

I CNCed all the bulkheads, mostly out of aluminum, but one BH in the noscone bay is fiberglass.

The ebay parts include a simple FG sled, a switch bracket CNCed from 3/4" basswood and a number of fiberglass parts and brakcets.

I will go over the recovery system in another post, but I spent considerable time talking with my TAPs about the various strengths and forces that each component would be subject to in a worst case scenario and bought or built the components with those discussions in mind. To that end, the u-bolts used are 3/8" thick from McMaster-Carr and are rated for thousands of pounds. Likewise, all the quick-links used that will be subject to the weight of the rocket are also 3/8" thick from McMaster-Carr and are rated for 3900 pounds each. The bridle and shock cords are all custom made by Teddy from Onebadhawk and are all rated for over 5000 pounds. The Cert 3 XXL parachute is more than adequate for this rocket, but only came with a 1500 pound rated swivel. While the cert flight is designed to be low and slow, so will unlikely generate velocities that will exceed the capability of that swivel, I would like this rocket to fly on bigger motors later, so I had Teddy also replace that swivel with a length of kevlar and a 5,000 pound rated swivel.

The all-thread in the ebay has to hold up the weight of the entire booster section as well as absorb the shock of the various events, so I used 4 lengths of high strength steel 5/16-18 all-thread from McMaster-Carr each rated for 150,000 PSI.

The thrust plate is 1/4" aluminum CNCed to attach the Aeropack 98mm retainer. The holes were all threaded for the screws so the retainer housing can be bolted directly to the thrust plate. Normally, I do this so I can remove the housing and use it on multiple rockets, but since this is my cert bird, I am going to be permanently affixing those screws and the housing to the thrust plate.

All the components were washed and sanded thoroughly inside and out with 220 grit sand paper and washed again numerous times. For anyone that has not built one of these bigger rockets, I would invest in some decent equipment for sanding and finishing. Basically, look for the same tools auto body workers use to work on cars. A good random orbital sander and a good size package of sanding discs seems like a must. There has been a lot of sanding. Also not sure how anyone builds anything without a Dremel tool handy, but I would have been lost 100 times on this build without my Dremel.

I am using a variety of epoxies in this build - West Systems 105/205 is the workhorse, sometimes mixed with their 405 Colloidal Silica when I need to thicken it up. Proline 4500, JB Weld and RocketPoxy will also make an appearance. For 5-minute epoxy needs, I am using both JB Weld Clear Weld and West Systems G5 - literally, whichever of the two is close at hand when I need it. I very sincerely do not want to make this a glue thread, so I am not advocating these epoxies at all - just listing them because people usually want to know, so may as well answer the question up front.

Here are some photos of the CNC process and some of the components. Note, in the photos here, the wood parts shown were all test pieces I used to make sure my designs were correct. After everything was fabricated, sanded, washed and tested, I dry fit everything countless times to make sure I had things right.

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The sled is 5" wide and 16" long. It is a gigantic platform for electronics. The RRC3 and SLCF will look tiny on here.

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Dry fit of the MMT assembly:

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Nytrunner

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Great choice! I fancied this as my L3 build before I came up with what will be my project (if I ever get around to it).
Still want to build one some day
 

mtnmanak

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The toughest part of this build seems to be getting the entire MMT assembly correct, so that is where I began.

The MMT assembly all stems from the placement of the forward centering ring. This CR is also the point that will take the brunt of the recovery shock, so I chose to fabricate it out of 1/4” thick FR4 Fiberglass. Incidentally, all the CNCed fiberglass parts on this rocker were made using FR4 sheets. FR4 is just the fire retardant version of G10 FG. The main reason I went with FR4 over G10 is that the place I source my FG sheets from (www.eplastics.com) only sells the FR4 version since it can be substituted for G10, but G10 can not be substituted for FR4. Also, I figure being fire proof can’t hurt!

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My TAPs and I had a long discussion about whether this CR should be made out of aluminum. It was easy for me to go either way, I had both materials on hand and it is actually a lot easier to CNC aluminum than the thick FR4 – the FG eats router bits for breakfast. The arguments that led to going with FR4 were that it has almost the same tensile strength as the 1/4" Aluminum (40,000 PSI for the FR4 and 45,000 PSI for the Aluminum), but the flexural strength of the FR4 is much higher than the Aluminum (60,000 PSI for the FR4 and 35,000 PSI for the Aluminum). So, in this application, both materials will most likely not break in any amount of force this rocket can produce, but the Aluminum has almost twice the chance of deforming under a high impact load. If the CR deforms, it is far more likely to fail. Further, the FR4 bonds to epoxy much, much better than aluminum. Since this CR will be holding up the heaviest piece of the rocket, we decided FR4 was the way to go.

The entire motor mount tube is barely long enough to handle the motor mount assembly. There is about a ½” to spare, so I needed to make sure I didn’t squander it. Looking back on it now, I would recommend to anyone building this rocket to use a bit longer MMT to give yourself some more working room. I need to have some room on the motor mount tube on the fore end to put in an epoxy dam down the road, so I measured about ¾” back from the front of the MMT and marked off the position of the front CR. I then tacked the front CR in place with some CA. This will provide the anchor for the rest of the CR placements.

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Then I marked off the approximate positions of the fin tabs and extended the lines around the body tube. For tube marking, the traditional method is to wrap a piece of paper around the tube. That worked for me up until the tube circumferences started getting longer than the edge of legal sized piece of paper. That is when I invested in a pipe fitters marking guide. This one I got on Amazon (https://www.amazon.com/gp/product/B004XNZCEO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) was more than long enough that I was able to cut off a couple small sections for tubes 4” and below and still have plenty left over for tubes up to about 12” in diameter.

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I inserted the 8-32 all-thread in the front CR and locked them in with dual hex nuts on either side of the CR.

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For each successive CR, I tested the fit of the fin tabs and then locked in the CR with hex nuts. Using the hex nuts, I could adjust the spacing of each CR precisely as I moved down the MMT. I inserted the lower spanners (which form the glue wells later on) between each CR as I moved along.

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Next up, I need to get the fin slots on the booster cleaned up and the fins fitted to the slots.
 

mtnmanak

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Before I could dry fit the assembly in the booster tube, I had to ensure the fins fit into the slots in the booster. The slots were a little rough and needed some shaping up. The ends of the slots were uneven (it looks like the slot cutter they used may not have been aligned properly) and the fins were a hair wider than the slots. So I shaped up the ends of the slots and drew lines around the tube to ensure the slots were all the same length. I then used a Dremel to clean up / slightly widen each slot. Once I sanded down the fin tabs, they all fit nicely and were all aligned.

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I also took the opportunity now to use a long piece of angle aluminum to draw lines longitudinally down the body tube along the fin lines and exactly between each fin.

Once I had the fin slots fixed, I dry fit the MMT assembly in the booster tube and ensured all the fins fit perfectly.

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After that, I tacked in each CR with CA and locked in all of the nuts on the all-thread with some 5-min epoxy.

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I did one more dry fit of the entire booster assembly before I epoxied the CRs in. This is a big booster section!

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mtnmanak

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With everything appearing to fit well, I epoxied the CRs in with West Systems 105/205 mixed with West Systems 406 Colloidal Silica to make a thin paste.

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I proceeded to epoxy in each side of the CRs and let the whole assembly cure overnight.

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The next day, I tacked in the lower spanners with 5-minute epoxy. The main goal here was not structural, it was to seal the spanners in so they are water tight. These will be filled with liquid epoxy later on, so they can’t leak.

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dr wogz

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Post it. I'm building a 4" AGM-33 Pike, but pretty much tossed all the parts in the kit except for the fins. I'm using BlueTube 2.0 and several plywood bulkheads to secure the motor tube and fins vs. the (2) that come in the kit. I've also used a couple of paint sticks and clamps to make sure the fins (since they are separated) are correctly aligned while the epoxy sets.


View attachment 472539
View attachment 472541
Can I ask why you went with Blue tube over the supplied paper tubes? (Not being rude, just curious..)
 

mtnmanak

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Once the epoxy was cured, I checked the glue wells for leaks by filling them with water.

There were a few leaks and I patched them up with epoxy once they were dry.

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I also got the U-Bolts installed in the forward CR and secured them with epoxy.

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mtnmanak

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Next, I marked off the upper and lower sections of the glue wells on the fin tabs to give me an idea of where I can drill some holes. The intent of the holes is to let the epoxy in the glue wells flow through them and provide more of a mechanical “grab” on the fin tabs. The lower section of the glue well is about 3/8” wide, so I made the holes in the tabs 1/8” in diameter. I measured the holes out about 2 inches apart and drilled them out on my drill press.

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I then did another water test with the fins in place to test the seals again and to also judge how much liquid each well could hold with the fin displacement. I wrote the volume of each well on the side of the spanner so I could record it later.

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mtnmanak

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I then tacked in the upper spanners (which act as fin guides) into the CRs with CA. I decided to just use a bit of CA for this application in case something goes wrong later with the alignment and I need to knock out a spanner or adjust one. These spanners are just guides and are not structural.

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At this point the rear CR was not epoxied in place. I did tack in the ¼” pieces of all-thread in the rear CR for the thrust ring placement. The MMT assembly is ready to be installed in the booster tube.

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Before I installed the MMT assembly, I drilled the hole for the rear rail button.

The rear button needs to be about 6 inches from the end of the booster tube to clear the rear CR and ensure it does not interfere with the CR installation later.

I drilled a 1/2” hole for the Rotaloc epoxy nut and fitted it in place. The steel disc around the nut is large (about 1.5” in diameter) and flat, so it does not sit inside the tube very well. I gently curved the steel disc in a vise and then it conformed nicely to the inside of the body tube. I am not adhering the nut right now, just fitting it for after I install the MMT assembly.

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The last thing I did before installing the MMT assembly is mark out the locations of the CRs and the drill hole locations for the upper rail button, the #10 screws I am going to install to give the upper epoxy dam better "grip" to the airframe and the location of the booster shear pins.

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Theory

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really like the way you document everything right on the air frame or specific component.

best not to leverage guess work or relying on memory with a project like this
 

mtnmanak

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really like the way you document everything right on the air frame or specific component.

best not to leverage guess work or relying on memory with a project like this
Absolutely - It is a practice I try to conform to on all my builds, but on this one it is particularly important. There are just too many parts and pieces and trying to write it all down on paper would be frustrating. Mark the info on the piece, then go back and document it on paper later. It also helps keep me working in "the flow" since I don't have much/any time to work on rockets during the week, I have to aggregate all the building on the weekends, so when I can dedicate a couple/few hours, I want to build and not stop and document.

The spanners alone are all over the place. There are 3 different sizes and at least two variants (mainly because I messed the tab length up on the first batch) for the rear spanners, so keeping them labeled is really important because the variations in size are sometimes just a few millimeters and I can't tell the difference by eye.
 

mtnmanak

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Made some progress this weekend:

I inserted the MMT assembly into the booster and inserted the fins to ensure everything stayed aligned and then tacked the forward CR in place with some 5-minute epoxy. At this point, the intent of the epoxy is to hold the MMT in place and seal off any gaps in the upper CR. One of the final steps of the booster construction will be to pour an epoxy dam onto the top of the upper CR, which will provide the main structural holding power.

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With the MMT assembly tacked in place, it was time to start epoxying the forward fins. I ensured the body tube was level and plumb. To check for plumb, I used the lines I drew on the body tube earlier. I then clamped the body tube to the stand. It is important for the tube to be level since there will be a significant pool of epoxy in the glue wells and I want the epoxy to be evenly spread across the fins tabs. By making the tube slot plumb, I can later check the alignment of the fin by making sure it is also plumb. In theory, that alone should ensure the fin is exactly perpendicular to the tube. However, the fin guides on the MMT assembly will also hold the fins aligned and I also CNCed several fin guides to make triple sure the fins are aligned.

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I am using West 105/205 for the epoxy pools for each fin. I am using 20ml syringes with 5” long 8 gauge dispensing needles to inject the epoxy through the fins slots and fill the glue wells.

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I injected the proper amount of epoxy for each tab into the wells, inserted the front fin and slid the fin guides in place. After allowing the epoxy to cure, I proceeded to do the same with the other two fins. I am going to let those Epoxy wells cure up over the next couple days.

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Theory

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very nicely done

dig how you clamped to the air frame to your PVC stand to ensure nothing moves. little things like that go a long way in keeping everything square
 

mtnmanak

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very nicely done

dig how you clamped to the air frame to your PVC stand to ensure nothing moves. little things like that go a long way in keeping everything square
The booster section is getting pretty unwieldy - it is already well over 30 lbs. My daughter has been helping me now every time I have to move it around - it is so big, it is difficult to get ahold of it and carry it.

You would think that something that heavy would just want to stay put in the stand, but each one of those forward fins is over 2 lbs and they make the whole thing want to roll one way or another. I realized quickly the whole thing had to be clamped if there was any hope of keeping it steady.

What I didn't show (and don't seem to have a picture of it, for some reason) is that I also clamp the PVC stand to the table. That is 2" Charlotte PVC, so it is a pretty hefty PVC stand, but this big booster makes it look small and feel flimsy.
 

Theory

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You would think that something that heavy would just want to stay put in the stand...
i hear ya there. while my last build was not even close to as large as yours, i did find that the large fins and extra weight proved to create challenges that didnt exist with previous builds.
 

mtnmanak

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Once the front fins were cured, I removed the thrust plate and rear CR and epoxied the rear Rotaloc nut in place. I tacked it in with some 5-minute epoxy, then placed a piece of tape over the center hole/threads and used West 105/205 with colloidal silica to securely bond the nut to the body tube.

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With the rail button nut in place, I used Proline 4500 to epoxy the rear CR back in place. Once it was in position, I used 8-32 wing nuts to secure the CR to all-thread and then used the left over Proline to coat all the hardware. Before I install the thrust plate, I will pour some epoxy over the rear CR, so right now the intent is to seal all the gaps in the rear CR.

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mtnmanak

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With the rear CR back in place, I could now install the rear fins. The only difference in the installation of the rear fins from the front fins is that I used a black dye in the epoxy to be able to see if there are any leaks. Also, I did not use the fin alignment guides, I just used the tried and true method of clamping angle aluminum to the front and rear fins to ensure alignment.

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Theory

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I just used the tried and true method of clamping angle aluminum to the front and rear fins to ensure alignment.
Yea buddy, KISS!!! when we get creative we engineer in potential failure points.

i square my fins with a plumb string, speed square and a level. "no muss, no fuss..."
 

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Don't mean to derail the thread, but what purpose dors the all-thread in the motor mount have? Seems like a lot of weight...
 

mtnmanak

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Don't mean to derail the thread, but what purpose dors the all-thread in the motor mount have? Seems like a lot of weight...
Mainly, it was used to align all 6 CRs and the thrust plate. It allowed me to adjust each CR by about .001" when I was lining everything up. I probably could have removed the 8-32 thread and it wouldn't have made much difference, but I do think it adds some structural support to the whole MMT and since the thrust plate is attached to all that all-thread, some of the force of the motor thrust should be dissipated through the all-thread. It should also assist in recovery by giving the upper CR some more "grip" to the rocket instead of just being held in by epoxy bonded to the airframe and motor mount tube. So, I chose to leave it in place. It is actually pretty lightweight. All that all-thread and the nuts aren't as heavy as one of the epoxy wells for the fins. And, on a rocket that is going to weigh over 75 pounds dry, I felt a few ounces wasn't going to hurt anything. Heck, the unistrut rail button assemblies are almost as heavy as the rear set of all-thread.

And, at the end of the day, this is a cert flight bird. Performance is not my goal. Overbuilt, rock solid, low and slow flight is my goal. More weight is not necessarily a bad thing in this case.
 
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