MAC Performance 4" Bolt Two Stage Build

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

ECayemberg

Well-Known Member
Joined
Jan 21, 2009
Messages
2,874
Reaction score
839
I'm in build mode right now (and I'm not burned out yet on posting build threads), so here's another! Mike Crupe from MAC were chatting around Thanksgiving time when he boldly exclaimed that I needed the new Black Friday release from MAC: the 4" Bolt! https://www.rocketryforum.com/threads/black-friday-release.156027/ I told him that I need another rocket like a need a hole in my head. Nevertheless, a week later I had a 4" Bolt on the doorstep.

But there's a problem. I just can't build the Bolt as a single stage vehicle...those upper fins make better sustainer fins than canards after all. Plus, I need practice with the new fandangled tilt detecting staging electronical doo-dads available today, so a 2 stager it becomes!

Contrary to popular belief, I do build things out of materials other than paper and plywood at times. This build obviously falls into that category. The parts are a wonderful marriage of Wildman glass and MAC canvas. I like the combo as it provides high strength without a ton of weight. A photo from Mike from his Black Friday Release thread captures the basic components of the kit better!

4-bolt-missile-parts-3-jpg.398811


Construction begins with deconstruction! Take that beautiful continuous length of filament wound glass airframe and chop in half (well, roughly).



I'm a fan of the hacksaw!


To be continued.....
 
I'm in build mode right now (and I'm not burned out yet on posting build threads), so here's another! Mike Crupe from MAC were chatting around Thanksgiving time when he boldly exclaimed that I needed the new Black Friday release from MAC: the 4" Bolt! https://www.rocketryforum.com/threads/black-friday-release.156027/ I told him that I need another rocket like a need a hole in my head. Nevertheless, a week later I had a 4" Bolt on the doorstep.

But there's a problem. I just can't build the Bolt as a single stage vehicle...those upper fins make better sustainer fins than canards after all. Plus, I need practice with the new fandangled tilt detecting staging electronical doo-dads available today, so a 2 stager it becomes!

Contrary to popular belief, I do build things out of materials other than paper and plywood at times. This build obviously falls into that category. The parts are a wonderful marriage of Wildman glass and MAC canvas. I like the combo as it provides high strength without a ton of weight. A photo from Mike from his Black Friday Release thread captures the basic components of the kit better!

4-bolt-missile-parts-3-jpg.398811


Construction begins with deconstruction! Take that beautiful continuous length of filament wound glass airframe and chop in half (well, roughly).



I'm a fan of the hacksaw!


To be continued.....
Eric, I am glad you are doing this! I too bought one with the same purpose in mind. Bill Good did the same thing to a 3" BOLT and it is a fun little screamer.
 
Sustainer Motor Mount

Now that the main airframe has been halved, it's time to build a sustainer!

The stock parts from the kit are used; however the motor mount tube has been shortened, and an Aeropack 54mm retainer added to the assembly.


One quick tip on gluing Aeropacks. After cleaning the surface to be bonded with alcohol, apply some JB Weld (high temp) to the inside of the retainer body. Use a stick to press the epoxy into the grooves; only apply enough to fill the grooves. Then apply plenty of JB to the outside of the roughed up end of the motor tube. Without the light application to the inside of the retainer, the "hills" from the ridges prevent epoxy getting into the "valleys".



The sustainer's motor mount is assembled from bottom up. Being a sustainer, a section of 3/8" aluminum tubing is installed to allow for passage of sustainer ignition and separation charge wires. Leftover JB Weld is laid atop the aft centering ring and around the bottom edge of the coupler that lands in the fin slot region.



Coupler mates to the aft centering ring and is prepped for the upper ring



Booster Motor Mount

I'll say it once here, so I don't have to say it again for the remainder of the thread.:) The included components of the kit, whether fiberglass or canvas, are rather non-porous materials and should be roughed up prior to bonding. In most cases, quick work is made of this step by using a Dremel with the drum sander attachment. The intent here is to scuff the surface, without removing significant thickness of the material.



The 75mm motor tube is cut down in size to afford more room for recovery gear in the booster. *Stuff* is scuffed.



I really like the look of the tail-cone retainer on the 3" Bolt, but...I really want the drag on the booster of this 4" dual stage Bolt. So, the stock stepped thrust plate gets used. Going for old school retention here, a trio of #8-32 PEM nuts are installed.

A bit of epoxy on the ribs couldn't hurt.



A screw with a flat washer on the opposing side is tightened, pulling the PEM nuts into place. Excess epoxy is used for fillets around the PEMs.



Everything is assembled and filleted. MAC kits and components fit together so well!!!:D



The motor mounts wait for epoxy to dry...o_O



...to be continued...
 
Apologies for the lack of an update; the last two weeks have been a bit ridiculous. We left off finishing up the motor mounts; 54mm for the sustainer, and 75mm for the booster.

The booster mount was epoxied in place using some West 105/205/Silica. A ring or three of epoxy on the previously scuffed inside of the airframe, as well as some on the lip of the thrust ring at the aft end of the airframe and mount.



I had some epoxy left over, so epoxied the bulkplate to the nose cone coupler after scuffing and removing the dust. The top end of the coupler will be secured into the filament wound glass cone via #6-32 screws. Having the ability to separate the coupler from the cone allows for undetermined future use of electronics, tracking, etc.



The sustainer's mount was epoxied into the sustainer's lower airframe, being careful to keep the lower ~4" free of epoxy. No glory shots of this step, but here is the completed assembly, with scuffed fin roots and fillet-areas on the airframe.



A foam fin alignment guide is used to ensure 90 degree spacing between the four fins. Two are installed in place to align the alignment guide. One batch of Rocketpoxy is mixed up for tacking of all four fins. One batch of 5 minute epoxy is mixed for each fin. Since the Bolt was designed as a single stage rocket, the upper fins (now sustainer fins) have tabs that run through the airframe wall and a coupler, but not thru the wall, to a motor tube. Thus, one has to be careful that they don't "fall into" the airframe too far. For this reason, I used a combo of Rocketpoxy and 5 minute for tacking.



Here's what that looked like. Rocketpoxy on the outside edges of the thru-the-wall portion of the fin root; 5 minute epoxy on the forward portion of the fin that contacts the OD of the airframe.



...And tack. The fin alignment guide holds things in alignment, the 5 minute epoxy sets the fin in place at the forward end of the fin root. Again, 1 batch of Rocketpoxy was used for all four fins, while one batch of 5 minute BSI was used for each fin. Tack, cure, rotate, repeat four times.


More to come...
 
Very interesting build, thanks for the thread. Are the phenolic canvas fins alot lighter than they would be if they were G10 or G12? (I've no experience of either material..)
 
I know the tubes are quite a bit lighter, but if I remember correctly the fin stock is close as far as weight is concerned.
 
Hi Guys,

I’m in the process of assembling Mike’s 4” Bolt in the standard one stage configuration. It’s a nice kit. Your idea of converting it into a two stage kit is very interesting. I’m curious how you are going to build the interstage.


Best of luck,
Bob
 
Back
Top