Build Thread: Scratch Built Super Magnum - FWFG 5.5" with 54mm + 6x 29mm Cluster!

[patelldp]

This thread is the culmination of months of thought and a thread to break the tie in my mind on how to build this thing, found here:

5.5" FWFG Magnum Clone - 98mm or 54mm + 6x 29mm?

Well, 86.96% of the people that voted chose a cluster of a central 54mm with six 29mm outboards! With that decided, it was time to put pen to paper, end mill to flat stock, and epoxy to fins, rings, and tubes!

A bit of history first! My first LOC Magnum was purchased from Ken Allen of Performance Hobbies in 2002 in Cobleskill, NY. That Magnum wasn't really a Magnum, but an amalgam of components from the back of his truck...two full lengths of 5.5" tubing, two fins (I cut the third), a nose cone, and a 52" Skyangle. I then took this pile of parts and tossed in a Missile Works RRC2 Classic to make a dual deploy behemoth the perfect size for a 14 year old high school boy that was about to meet his future wife!

I even wrote an RMR Review, found here!

Its first flight was at the September 2002 CTRA Invitational in Cobleskill, NY and flew to 1,650' on an Aerotech J460T. It flew perfectly! I recall flying it the next year on the venerable AMW K670GG. What a flight, that brilliant GREEN flame etched in my memory forever! Some time later I flew it on a J415W in Pine Plains, NY only to have the rocket deploy early thanks to insufficient venting of the RRC2. I never once put a cluster of motors in that thing...so let's change that!

Fast forward 16 years and it's time to build another Magnum. 16 years?! I am over twice as old as I was when I built the first one?!?!? I ordered up a 60" stick of 5.5" tubing from Ken cut to Magnum lengths with a bit of a twist: 45" booster, 17" payload, and a 2" switch band (the twist). Add a sheet of 1/8" G10 for the fins, some various thickness plywood for the centering rings and various tubes and we'll have ourselves a rocket!

In 14 years I've been able to afford some WAY cool toys to help with this thing...namely a Shapeoko XXL CNC router, a Creality CR-10 3D printer, and an Atlas Clausing 12" x 36" lathe. The router is instrumental in cutting the flat pieces in this build, the printer will handle most of the electronics bay duty, and the lathe will be making all of the 29mm motor cases. Oh, I also have a Hobart 20qt mixer now...that'll get used too!

Here we go!

 

[patelldp]

Before I started cutting parts, I needed to figure out the dust situation that this router creates. It throws a TON of dust, and fiberglass dust is bad news. Enter the Suck It Dust Boot. I was virtually dust-free after the simple 30-45 minute installation! With that accomplished, it was time to cut some fins!



I attempted to take a GoPro video of the process of cutting the fins but my batteries appear to be on their last legs. I managed to capture 4 minutes of the cutting process before it died, I can post if there's a huge desire. After about 12 minutes I had 3 perfectly matched fins with almost zero dust!





Next step: Cut some centering rings!

 

[LOC]

There ya go!!! Fill up that ring. I never did understand only a 2x29mmt outboards... Anxiously following!

 

[patelldp]

There ya go!!! Fill up that ring. I never did understand only a 2x29mmt outboards... Anxiously following!

I hear that you guys reverted back to the old fin profile...awesome! Barry did some weird things to some of the fin profiles, happy you guys are going back.

 

[patelldp]

Last post for tonight! Here's the collection of tubing necessary to build such a rocket. As mentioned before, you have a 45" booster, a 17" payload, and a switch band to make up the original length. The switch band was advertised as 2" but is actually 3.8" so a decision will be made later about whether or not it's worth the struggle to shorten it.

I am currently planning a Flexible Phenolic coupler because it appears there aren't any FWFG ones in the wild. This specific coupler has a jagged end that will need to be cleaned up and then the inside will be reinforced with a couple layers of glass. I have a plan to fix the jaggedness...

The central motor tube is a 21" long FWFG 54mm tube (thanks Bat-Mite) and PML 29mm outboards. Ken said to me "I can't remember the last time someone ordered PML 29mm tubing" when I ordered it. I am using FWFG for the central tube due to its structural nature while the outboards are purely motor sleeves.

The nose cone is a classic LOC 5.38L. It's a bit of a loose fit in the tubing I have, so I'll be 3D printing some spacing ridges to epoxy to the shoulder to make up the difference.

In the background on the PVC rack is the original Magnum booster. I had started glassing it at some point and stopped. The remnants of the "Fred" lettering on the white fin (not shown) that I placed there when my grandfather passed are still present. The spot where I cut a hatch for air-start electronics and then thought twice...man, there's some memories in that booster!

 

[LOC]

Last post for tonight! Here's the collection of tubing necessary to build such a rocket. As mentioned before, you have a 45" booster, a 17" payload, and a switch band to make up the original length. The switch band was advertised as 2" but is actually 3.8" so a decision will be made later about whether or not it's worth the struggle to shorten it.

I am currently planning a Flexible Phenolic coupler because it appears there aren't any FWFG ones in the wild. This specific coupler has a jagged end that will need to be cleaned up and then the inside will be reinforced with a couple layers of glass. I have a plan to fix the jaggedness...

The central motor tube is a 21" long FWFG 54mm tube (thanks Bat-Mite) and PML 29mm outboards. Ken said to me "I can't remember the last time someone ordered PML 29mm tubing" when I ordered it. I am using FWFG for the central tube due to its structural nature while the outboards are purely motor sleeves.

The nose cone is a classic LOC 5.38L. It's a bit of a loose fit in the tubing I have, so I'll be 3D printing some spacing ridges to epoxy to the shoulder to make up the difference.

In the background on the PVC rack is the original Magnum booster. I had started glassing it at some point and stopped. The remnants of the "Fred" lettering on the white fin (not shown) that I placed there when my grandfather passed are still present. The spot where I cut a hatch for air-start electronics and then thought twice...man, there's some memories in that booster!

View attachment 335907

Well, you beat us to the flexi couplers by about a month. But I do have some classic phenolic in stock if needed. And if that would fail somehow, we'll have flexi in by the summer... =) Just don't tell anyone you heard it here....

 

[DRAGON64]

Should be interesting, I love the 5.5" series of rockets from Loc, and the Magnum is right at the top... even the clones!

 

[patelldp]

The CNC is humming away...update soon!!!

 

[patelldp]

Soon turned into not so soon.

I cut the centering rings and then did a dry fit. Idk guys, this is a lot of rocket for a little motor mount...







More narrative on my plans tomorrow!

 

[dixontj93060]

Lookin' good!

From the Ether...

 

[patelldp]

Okay, some calm after the storm of the past few days. We installed shelving in our closet to GREATLY improve our storage situation, but that cut into rocket designing and building time!

As I stated yesterday, the centering rings have been cut from 3/8" plywood. In addition to that I managed to find a perfectly sized piece of garolite (XX Phenolic) tubing to use as a wire conduit. The electronics will all be housed in the coupler tube, so the wire routing is necessary. I also included three holes for 8-32 tee nuts in the aft centering ring and completely forgot to include holes for a u-bolt in the fore centering ring! Thankfully, I own a drill!

First course of action today was to cut the 29mm outboard motor tubes. They are 10.5" long PML phenolic tubes. I was surprised at the tubing's lack of chip-out when using an ordinary miter saw blade having never used PML phenolic tubing before. A little sand paper action and the tubes were good to go!

These rings are SNUG. Everything fits more snugly than any kit I have ever built. I'm finding that this may not be the best thing in world due to the difficulty I have had dry fitting the motor mount. The tubes must be aligned just so in order for all of them to engage the centering ring. I'll need to pre-build this assembly prior to installing it in the body tube, so injected internal fillets will be the way to go.



This assembly was then pushed into the booster tube to see how everything fits. Looks perfect to me!



Toss in a fin to re-check the tab length. Again, looks great!



I know I posted a similar picture yesterday...but here's the whole stack again with all three fins in their slots. This thing is a big rocket, I'm lucky to have 9' ceilings in my basement!



Next few steps include drilling holes for a u-bolt in the fore centering ring, designing and printing a fin alignment guide for the fins, and then epoxying this gigantic mess together! I also saw that Mad Cow has 5.5" couplers back in stock, so one of those is coming my way! Thanks for reading along!

 

[patelldp]

Just hit print on this guy...should take care of fin alignment. I just don't do it well by eye.

Should be ready in the morning!

 

[patelldp]

I swear it didn't take 3 days to print the fin alignment guide! Here's the guide off of the printer and onto the tube. Looks like it will do exactly what I want it to do!



Next step was to fix my omission in my CNC process...time to add a shock cord attachment point to the fore CR! I typically use the attachment point on the forward closure for the shock cord on rockets with larger motor mounts and therefore smaller webs. That method would have been employed had I built this rocket with a 98mm mount. Since you guys wanted to see a cluster I now have the room to place a u-bolt!

Heres the parts necessary...the u-bolt, 4 nuts, 2 washers, and the plate that typically comes with it. I used some blue Loctite on the nuts to keep it attached after cranking down on them. Probably not necessary, but doesn't hurt.



I located the steel backing plate on the CR so that it was mostly centered and not interfering with the motor or body tubes. Place the u-bolt in the holes and strike it with a normal hammer to transfer the hole location to drill!



Here's the result of the strike. All that's left to do is drill two 5/16" holes and it's ready for a u-bolt!



Passed the u-bolt through the ring, dropped the plate on, applied some loctite, and cranked down on the nuts.



Somewhere in there I attached the fore centering ring with 5 minute BSI epoxy. I did this by smearing the epoxy on the motor tube (after a thorough 100 grit scuffing), starting the ring on the tube, and then pushing down on the motor tube. The ring was sitting on a piece of 1/4" plywood with a hole in it, therefore permitting me to push the tube through. The result is a ring perfectly located 1/4" away from the fore end of the tube, ready for a RocketPoxy fillet (psst...when you do this please fillet the joint before installing the u-bolt...you'll get a completely clean fillet all the way around...)

 

[rfjustin]

Dan, do you need the fins beveled?

 

[patelldp]

Dan, do you need the fins beveled?

Nope! Thanks for the offer, but your help in previous years has led me to purchase this bit. Now I just need to make a fence for my router table on my CNC...I’ll get there!






Sent from my iPhone using Rocketry Forum

 

[jlabrasca]

Very cool build. Why didn't you bevel the fins on the CNC?

 

[patelldp]

Very cool build. Why didn't you bevel the fins on the CNC?

That would require a flip operation. That involves relocating an origin. I don’t have a touch plate yet, so it’s not really an option until I buy one. I’ve considered printing a jig to permit me to clamp a fin in the router field and manually draw an end mill across the leading edge, but haven’t gotten that far yet.

Manual is just easiest with the tools available to me.

 

[jlabrasca]

That would require a flip operation. That involves relocating an origin. I don’t have a touch plate yet, so it’s not really an option until I buy one. I’ve considered printing a jig to permit me to clamp a fin in the router field and manually draw an end mill across the leading edge, but haven’t gotten that far yet.

Manual is just easiest with the tools available to me.

Don't want to jack the thread, so PM me if you want details, but there is a way to do this without having to re-zero your origin after flipping the stock.

 

[patelldp]

Life has gotten out of the way for a little bit, so let's update this beaut.

Because of the tight tolerances that the CR has, I elected to dry fit the outboard motor tubes in the rings and then stick them with thin BSI CYA. This CYA flows really nicely in tight places via capillary action. It also sets nearly instantly which can be further promoted with the use of Accelerator. Once I had everything right where I wanted it, the CYA was applied and the assembly was solidified.



Next up was the 54mm motor tube with the fore CR already installed as above. Same gig, install and hit it with thin CYA.



You may be thinking "CYA isn't that strong, you can't possibly put a 54-2550 and six 29-360's in there and expect it to hold, could you?" Truth is that it would probably be fine as most of the strength comes from the attachment of the fins through the tube and to the motor tube. Just in case, let's pour an epoxy reservoir on the fore sides of the CR to assure that everything is an integrated system.

First is the tape dam:



Then dump some simple laminating epoxy in there. This specific epoxy is from a manufacturer down the street that primarily feeds the power generation space.

 

[patelldp]

Once the epoxy dam was cured the assembly was installed in the main body tube. The location of the rings was marked, sanding done to the associated section of the ID, epoxy applied via a piece of quarter round, then the mount pushed into place.



As you can see, a nice little fillet is formed on the fore side. I am planning to do an epoxy dam on this ring to seal and reinforce a bit.I used Loctite E-120HP for this installation because I had just about the right amount left in an old tube. Here's a shot of the applicator (Will be used for the fins to ensure proper mixing and easy application):



Preparing for the fin installation yields the same stuff you see in other threads. Notching the slots for injected fillets using Amazon dental bottles with spouts and 40 grit sand paper to sand the fin tabs.

 

[patelldp]

Here's what's taken so long...I've needed to get the "Strength" up to design and cut the parts for this router beveling jig. The purchase of a new table saw really helped. I've had the necessary bit hanging around for a few years now but never got around to making the jig...until today!





I really don't love the idea of it because it's trapping the work between a fence and a bit. That said, it's a clean and simple way of doing it and taking extreme care will be paramount. The size of the fins I plan to do with this allow me to keep my fingers back. I'll practice on some 1/8" stock and then I'll graduate to the Magnum fins (followed by Carbonated...but that will be another thread!!!)

Once the fins are beveled I'll be back with an update!

 

[user 434]

Okay, some calm after the storm of the past few days. We installed shelving in our closet to GREATLY improve our storage situation, but that cut into rocket designing and building time!

As I stated yesterday, the centering rings have been cut from 3/8" plywood. In addition to that I managed to find a perfectly sized piece of garolite (XX Phenolic) tubing to use as a wire conduit. The electronics will all be housed in the coupler tube, so the wire routing is necessary. I also included three holes for 8-32 tee nuts in the aft centering ring and completely forgot to include holes for a u-bolt in the fore centering ring! Thankfully, I own a drill!

First course of action today was to cut the 29mm outboard motor tubes. They are 10.5" long PML phenolic tubes. I was surprised at the tubing's lack of chip-out when using an ordinary miter saw blade having never used PML phenolic tubing before. A little sand paper action and the tubes were good to go!

These rings are SNUG. Everything fits more snugly than any kit I have ever built. I'm finding that this may not be the best thing in world due to the difficulty I have had dry fitting the motor mount. The tubes must be aligned just so in order for all of them to engage the centering ring. I'll need to pre-build this assembly prior to installing it in the body tube, so injected internal fillets will be the way to go.

View attachment 336219

This assembly was then pushed into the booster tube to see how everything fits. Looks perfect to me!

View attachment 336220

Toss in a fin to re-check the tab length. Again, looks great!

View attachment 336221

I know I posted a similar picture yesterday...but here's the whole stack again with all three fins in their slots. This thing is a big rocket, I'm lucky to have 9' ceilings in my basement!

View attachment 336218

Next few steps include drilling holes for a u-bolt in the fore centering ring, designing and printing a fin alignment guide for the fins, and then epoxying this gigantic mess together! I also saw that Mad Cow has 5.5" couplers back in stock, so one of those is coming my way! Thanks for reading along!

Looks terrific


Sent from my iPhone using Rocketry Forum

 

[patelldp]

Looks terrific

Thank you!

It was time to get over the anxiety that I had surrounding beveling the fins. I was quite happy with the way the fins turned out off of the CNC, I didn't want to mess them up.

First step was to rig up some dust control. I knew that this would throw some significant dust and that was another source of anxiety. Fiberglass is bad news bears, so I made sure to glove up, wear a hoodie to cover my arms, and wear a dual filter dusk mask and safety glasses. On top of that, I whipped out the duct tape and rigged my Shop Vac like so:



Here's the side angle to show how close it was to the bit and fence.



This seems to have done a really good job of keeping the airborne dust to an absolute minimum. There was a significant amount of dust accumulating on the table, but that was easy to vacuum after the job was over. It also acted as a sort of "hand guard" of sorts...its position forced me to keep my fingers up near the fence and away from the bit because my hand just physically didn't fit in there.

After some test runs on scrap G10 stock and some old 1/8" fins I had laying around I nailed the procedure. Lots of pressure down and toward the 90 degree corner in the fence. The first pass is a nice, easy pass taking off the bulk of the material, then a secondary pass to finish the edge and smooth out any spots where I hesitated. Do this on both sides and voila!

 

[patelldp]

With the fins beveled, I popped them in the slots to see how they looked. Much better!



After that picture was taken the fins were removed, the tabs re-sanded, and all glue surfaces wiped clean with acetone. I then broke out the E-20HP epoxy with mixing tip and applied epoxy to the root, fore and aft tab faces, and then the side faces of the tab and inserted the fins into the slots. The 3D printed fin guide was placed on the the rocket and the fins allowed to cure.



Final step tonight is my newest acquisition to help with this build...West Systems 105 Resin, 206 hardener, and 404 filler. In my 18 years in the hobby I have never owned or used West. I saw Manny using it in his Nike Smoke thread and used it as inspiration to finally check it off my list. I've seen and held rockets built with West and was always impressed with how well it cured versus the US Composites that I had had difficulty with. The issues could probably be chalked up to being a teenager at the time, but we'll see how this stuff works for internal and external fillets!

 

[ECayemberg]

With the fins beveled, I popped them in the slots to see how they looked. Much better!

View attachment 337468

After that picture was taken the fins were removed, the tabs re-sanded, and all glue surfaces wiped clean with acetone. I then broke out the E-20HP epoxy with mixing tip and applied epoxy to the root, fore and aft tab faces, and then the side faces of the tab and inserted the fins into the slots. The 3D printed fin guide was placed on the the rocket and the fins allowed to cure.

View attachment 337469

Final step tonight is my newest acquisition to help with this build...West Systems 105 Resin, 206 hardener, and 404 filler. In my 18 years in the hobby I have never owned or used West. I saw Manny using it in his Nike Smoke thread and used it as inspiration to finally check it off my list. I've seen and held rockets built with West and was always impressed with how well it cured versus the US Composites that I had had difficulty with. The issues could probably be chalked up to being a teenager at the time, but we'll see how this stuff works for internal and external fillets!

View attachment 337470

Looking good, Dan!

....and I thought I was the only one that wasn't bedazzled by USComposites epoxy. Have used it several times, have a lot of peers that use it, but I've never been satisfied with their epoxy. Love their glass, prices, etc. though!!!

Keep up the good work, and watch those fingers!:wink:

 

[patelldp]

Looking good, Dan!

....and I thought I was the only one that wasn't bedazzled by USComposites epoxy. Have used it several times, have a lot of peers that use it, but I've never been satisfied with their epoxy. Love their glass, prices, etc. though!!!

Keep up the good work, and watch those fingers!:wink:

Between US Composites and Aeropoxy I always suffered a slightly “soft” cure or extremely bad blushing. Humidity isn’t an issue up here in NY and care was always taken to measure properly. Who knows.

Woke up this morning to check out the “Super Blue Blood Moon.” It was very visible here, seemed like you could almost reach out and grab it, too cool!



Made some coffee, cranked up some Nathaniel Rateliff and the Night Sweats and mixed some epoxy. 5 parts resin, 1 part curative, plus two craft stick shovels of lamp black from my EX supply box yielded a nice dark epoxy that will clearly show where it rests following the injection.



I read about some curved dental syringes in the thread about your favorite tool, these things worked great! I had to cut the tip down 1/4” or so to make the hole large enough to pull the viscous epoxy. Once that was done I was cooking with kerosene and getting the epoxy into the half-holes I had previously dremeled in the fin slot.



36g of epoxy later and it looks like we had a successful injection! The black epoxy acts like an indicator. I got two nice fillets on the roots to the motor tube with minimal leakage around the fore and aft tab ends. It’s pretty tight around the motor tubes and the wire routing tube, so some epoxy got caught at the top of the root near the main tube on fin #1. We’ll call that “Super Fin” because it’s going to be SOLID.







I’ll do this a couple more times as the day goes on.

 

[rfjustin]

Watching with interest...

 

[patelldp]

Watching with interest...

Did I just about peg your method for doing bevels? I'd be terrified of doing someone else's fins without some stock to practice on first...don't think I'll ever achieve your level of mastery.

 

[patelldp]

Second set of internal fillets completed last night, 3rd set injected this morning and currently curing. I did the scientific "wiggle test" on the one fin that has both fillets cured and it is perfectly solid. Once the last set has cured I will fill the half circles for injection with BSI 5 minute + 404 to prevent leakage of the external fillets.

External fillets will be West + 404 fillet to the "catsup" thickness described on the 404 container. I'll use a PML 29mm phenolic tube end cut as the form which should yield a nice sized fillet to further lock the fins in place. Last step for the booster construction will be to pool West + lamp black on the top CR to seal and further fillet.

The motor retainer has been designed in Fusion 360 and the CAM file has been finalized, just need to mount the G10 in the router and hit start. It's primary purpose is to retain the 29mm motors. The XPS 54-2550 will likely be retained via tape at the fore end not unlike Jim has described and we've been doing for over a decade. A separate retainer will be machined for 54mm motors utilizing a spiral thrust ring.

Got notification this morning that my 5.5" FG coupler is enroute from Madcow. I was hoping that it would include my Nike Apache, but alas it appears I will need to wait even longer for that...

 

[rfjustin]

Did I just about peg your method for doing bevels? I'd be terrified of doing someone else's fins without some stock to practice on first...don't think I'll ever achieve your level of mastery.

Pretty damn close! I do a better job beveling someone else's find than my own... :lol: