Cj's 5.5in. Nike-Tomahawk [3in.] build-2 Stager..... 75mm to 54mm motors

[blackjack2564]

Mad Cow Nike Tomahawk came today...much larger than I expected. Here is the built Nike-Apache hiding amongst the parts & it's 5ft tall assembled!
Nicely packed & shipped well.
This kit features 75mm motor in the 5.5 diameter booster.
54 mm motor in the 3in diameter sustainer.
I will add 3/16 brake line for conduit & 1/4 in. sized parts/hardware.

My guess is add about 4 to 4.5 lbs for glue, hardware & recovery to the part weight of 16 lbs for a total of around 20 to 20.5 lbs finished. We'll see how close I get...... lol

I'm hoping to match this with motors that can keep it in the 4-6,000 ft level for home field flying fun!! I think I have a sweet spot weight wise so we will seeeee.....






Basic parts ...


Weights shown on sustainer are in LBS 1.5lbs etc.[ not lbs. and oz. like 1.8 ] in pencil next to letters
Weight on Booster parts are in grams.
I bumped a setting with a heavy part on my tiny scale.

Total weight of parts [kit] no hardware/glue/etc is 16.10---- sixteen lbs. & 10 oz.




ALL fins came stuck together from 2 sided tape glue residue. Used butter knife to pry apart, and clean with Xylene, Made quick work of gunky residue. WD-40-Acetone-Laquer thinner all work well also.



Parts that come are shown above in full pic of Interstage/coupler [I/S]
Below I added 2 coupler BP's & 2 BP's to make av-bay lids.

This I/s in not like the one with Nike-Apache, & is going require re-thinking the entire build of I/S electronic bay The 2 CR's are very sloppy and were designed to fit inside the coupler...not on top of lid...like the Apache.
I must figure out to center one on the BP...not the same outer diameter.




Both sets of slots & fins for both Booster & sustainer do not fit.
All slots needed opening more, filed one side [same on all] of slot.


The parts are high quality, just some extra work compared to the N-Apache, where everything fill well.
Hope you guys don't get as bad a fit between the I/S transition & coupler like mine.I spent almost 2 hrs sanding there 2 items. Mine was not close to fitting I/S but perfect in the body tube.

So ya know exactly where the issue was...the I/S not coupler. But I figured split sanding between the 2.

Needed to sand both outside top 1.5in of coupler & inside of I/S transition substantially.
Spent 4-5 hours just opening slots-cleaning glue residue--fitting basic parts, so they will work.

Tip:
To evenly sand a tube/coupler mark around with pencil....then sand off marks & stop...check fit....mark... more sanding ...repeat till fits. This way, you sand equal amounts off object, as you only sand through the pencil marks.

First I measured depth of I/S that coupler would fill in shroud...drew line around coupler by inserting into airframe, up to my mark, and penciling circumference.
Did my scribble lines and sanded them off.
Inserted coupler into I/S went to line closest to edge.

Seen with second set of scribble lol ...ready for 2nd sanding.
It took a third before I had a smooth fit and 2 standings on the inside of I/S Yeah it was a cr-- ton of sanding.

 

[blackjack2564]

I/S coupler Part 1.

Started build after acquiring needed av-bay hardware.
Using #10 [3/16] all thread for tie rods in Interstage coupler [I/S]
Glued all av-bay lids together and drilled most of needed holes.
I decided to start with most difficult aspect of build & get it out of the way.



Next measured & installed tie rods , drilled needed holes for separation charge & apogee main deploy.
3/16 bit and 7/64 bit. I chamfered entrance to seperation hole to make feeding charge wire through coupler into bay easier.
Tie rods centered 3/8 from edge of CR...mine yours may be a bit different.
As you can see my CR doesn't go to edge of BP, so measurement from edge of CR!
Be careful! You only get one shot at many of these steps.
The top av-bay lid consists of coupler BP...BP & the CR glued together.
I wrapped tape around CR to build it out same as the BP, then removed tape after gluing together. Keeps it centered correctly.

I will use the other [no longer needed CR] on the 75mm motor mount so I will have 3 rather than the supplied 2.




Using one hole for 2 charge wires. Began doing this recently, [on all builds] to keep from having to seal another hole from charge gases.


Tie rods are 8 1/4 inch long. Line is for my glue stage to make sure shroud is on level, not cocked.



The kit design calls for mounting the I/S coupler [3in] into the 5.5 coupler with the 2 CR's.
We will be mounting the 3in coupler on top of bay, not inside so coupler is 3 1/8 too long...
I place MM tube, fin - motor mount CR in position & dry fitted the 2 stages. as you can see where I XXX out is what needs to be cut off. Shined flashlight through tube, why it looks strange..lol



Done for tonight, must cut tube tomorrow out in shed, not heated and cold out there....49 outside!
Will glue it up after trimming to proper size.
....................................................................................................

Needed to cut 3-1/8in off 3in coupler. Be sure to square up both ends ESPECIALLY the one getting glued to av-bay lid!



I use JB Weld because I have industrial size tubes [cheap] and ease of mixing small amounts.
Tape over back of hole and fill.
Sand where glue will be including edge of CR that gets external fillet on coupler.
Apply glue to interior of ring.



Carefully apply bead around interior of coupler. Glue will settle and form interior fillet.



Insert coupler push tight, seating it to CR.
Add fillet around exterior, set aside to cure after checking fit of shroud,this will make sure all is straight and aligned.



Do NOT continue to next step till glue is fully cured!

 

[blackjack2564]

I/S coupler part 2.

Dry fit shroud over assembly and draw ring where 3in coupler sticks out.
This is where a bead of epoxy get put during next step.

Note where line is at bottom of shroud. I drew that back in post 1 when fitting shroud to coupler, so I have a reference line when I glue the shroud on. I had issue with this step during Nike-Apache build and alignment.
[Reason it is not close to shroud....I marked it without having a BP on. Either way it acts as a good reference mark]
This should solve that, by showing that when gluing shroud to coupler I have it on straight



Place bead of epoxy around shroud on flat area where it meets taper. Don't go nutz here, more is not always better, just a nice smooth bead. Too much and it will be difficult to seat the CR's.




Add a nice full bead around line on 3in coupler. Later when turned upside down to cure it will settle & form an interior fillet. Keep bead on line or barely below, so you don't have a mess when inserted into shroud!



Insert CR's with tie rods attached and push firmly to seat in shroud.
This is where you may have issues!

Be sure it goes in all the way, and seat square, or it will be cocked & the upper stage will be crooked when place on top. Too much glue will load the joint and make it difficult to seat all the way!



Place very thin amount of glue around inside of shroud. Too much here and coupler will be very difficult to seat into CR! Butter it. [pic from Nike-Apache build, I was working fast to keep bead from settling & forgot, for those that notice different color BP...lol]



Insert coupler and seat into CR...this is where that line comes into play around the 5.5 coupler. Shows if you have coupler seated and straight...it was not.... as seen by difference in distance between right side and left. It's leaning a tad to right.
Coupler of taps on left side with 2x4 fixed that!





The end where 3in coupler sticks out was a bit loose and glue began to seep, after wiping clean, a few wraps of tape stops further leaking.




Finally after fitting I/S to Booster and sustainer, used a level to be sure everything was perfectly straight vertically, and not cocked.

Removed I/S and check fit of shroud by measuring distance from edge of shroud to edge of coupler, all the way around
Absolutely Perfect!

Left upside down so that internal fillet on 3in. end would settle and all would cure.



Hardest assembly finished, on to some easier stuff!

 

[blackjack2564]

4 equal marks for shear pins are done by sliding I/S coupler into rear of fincan and drawing lines through fin slots onto coupler.



Then install coupler into front end of airframe to transfer 4 lines to exterior of tube.
Mark 1.5 inches from edge and drill for shear pins.

I made "key-mark" on joint between tube/I/S with same bit, to aid in alignment when prepping for flight.
I/S is finished for now.
Will drill needed holes for venting and power switch, when those parts come and are mounted on sled.



Building out motor mount & staging conduit for sustainer:

I will forgo details/pics, as by now you should know how to:

notch CR's for Y-harness
i used 6ft of strap Kevlar for harness.
Cut 2 ft of 3/16 brake line {Pep Boys] for conduit. Don't want more than a foot in front of MM or risk conduit fouling recovery cords and possibly getting bent.
Happened on my first 2-stage where I ran conduit up to av-bay coupler.

drill 3/16 holes for conduit in both CR's
Measure and fit CR's so they are tight to fins. { I'm injecting internal fillets]
Install motor retention [Aero-Pac for me]
Fit fins and mark each one to slot and number fins & slots

I leave the knob on end of conduit and place on MM tube 1/4 from edge of motor retainer to make fishing igniter wire easier.
Do this BEFORE gluing retainer on....knob will not clear retainer.



Glue Y-harness to MM tube & encapsulate with glue.

TIP:
I wrap with electrical tape to keep glue from running into area where fins fit. Not much room for error on this 4 fin version. Tape comes off very easy after cure.



After removing tape, ready to install.



Sand 3/4 wide area on each side of slot for external fillets & drill/file hole for internal fillet injection [holes not shown]



Wrap sandpaper around dowel/pvc to reach inside/sand where CR's located for glue adhesion.
Sanded area lighter color at each end of fin slots.



I just slide MM assembly into place dry, there will be plenty of glue contacting CR's when I inject internal fillets
My "double dip method" for fin installation. [butter fin root with glue, install,remove repeat] 2 coats glue on interior MM/fin joint.
Lay my angle iron across tube and clamp fins to it, keeping them straight till cure.

Once everything in place, I let drop of CA run down fin/tube joint to lock in place, so nothing can shift out of alignment.



Will do same for second set of fins. Won't bother with pics for that.

 

[blackjack2564]

More build progress as of Jan 1st 2019.

Having finished tacking the other 2 fins into position, time to move on to injections internal fillets
First using my tried & true method of coating my tool for smoothing fillets with sharpie, I rub it back & forth in groove between fin/tube and mark for tape.

Gives you a perfect line to tape and get fillet with no muss...no fuss.



Next I tape joint on bottom 2 fins [4 fin rocket] , then rotate back to bottom position.
If there is any seepage of glue from injecting top fins,this will prevent glue from running out the joint and all over bottom fin.



I mix only 15ml of glue the internal fillet is rather short since fin tab only runs !/2 way due to staging coupler.
There is a gap on all 4 fins behind the tab so I filled it with JB weld when tacking fins with same.
Why you see dark line under fin behind where injection is happening.
Then inject 1/2 into each fin fillet through hole previous drilled/filed on edge of slot.
Hole will be filled/covered by external fillet.
For me this is the easiest/fastest method of doing fillets.



You can see fillets have leveled out just fine.
I like natural color tubes for ease of seeing how internal fillets come out.
Glue is reddish brown, due to hardener age and turning red.
You also see the lower fins glue, I used to tack in place.



Finish all internal fillets and on to exterior.
Tape to previously drawn lines with tool.
Note the rear of Tomahawk fin root on airframe tapers away at rear edge, making the fillets a bit difficult.


I taped gap on rear side of fin so glue will not run on back side when install the fillets.
Ran tape across the fillet, when pulled makes it a squared edge. [under it of course]


Only way I could see that worked, with the fin notch.



While glue dries and I do all 4 sets of sustainer fillets, moved on to Booster fincan.

First must mention the slots are 3.5 inches from rear of fincan. If I mount retainer on MM tube and insert into airframe up to slot, it's far enough up in there to cook interior of tube and rear CR from base drag sucking heat and flame inside especially during smoke delay burn where there is no thrust just drag during coast.

I want to inject so CR's must be tight on fins. We are back to everything being flush with rear slot & that won't work for me...Sooooo.... I used the extra CR intended for the I/S coupler.....no longer needed since the I/S has been converted into an av-bay.

I opened up hole in the CR ,to fit over MM tube as originally it is intended to fit over a coupler. Yes I know it won't touch the inside edge of airframe tube, since it was for inside a coupler.
Matters not as I only need it to hold injection glue in place.

Mark CR for retainer screws [bolt on retainer Aero-Pac] and glue flush with tube end, I will fit it only 1/2 inch from rear of Booster tube, Just enough room for a fillet once installed.


Measure distance between slots and transfer on to MM tube, along with slot positions, mark fins and slots to fit.
Notch top CR for recovery Y-harnes. 6 ft of tubular Kevlar 5/8.
Be sure to position harness BETWEEN fin position!





Slather epoxy onto both sides [encapsulate] of Y-harness ends & wrap with electrical tape keeping glue from running everywhere. Epoxy will not stick to electrical tape and is easy to remove, keeping things neat.

 

[blackjack2564]

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[blackjack2564]

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[blackjack2564]

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[blackjack2564]

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[blackjack2564]

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[Viperfixr]

Subscribed...got mine on the way and interested to see how you build this, CJ!

 

[Cameron Anderson]

How are you positioning the 3x10.5" coupler in the transition? Where are you putting your centering rings?
I got the same kit and I'm toying with a few variations but haven't decided.

 

[blackjack2564]

You should read my Nike-Apache build , the I/S will build almost identically the same.
https://www.rocketryforum.com/threads/cjs-builds-madcow-nike-apache-2-stage.143897/#post-1751302


Here's what the layout is with parts supplied. 2 CR's get put on lower part of 3in coupler tube, then inserted into the 5.5 in coupler& glued.
Lastly the I/S shroud goes over all & glued. But that's for a single stage build, where both stages are permanently glued together. I don't think anyone does that, so extra parts needed to make I/S an altimeter bay.



I'm going to add av-bay lids to both ends of 5.5coupler & threaded rods.
On the top of av-bay lid, I'll glue the CR, & center the 3in. coupler into CR and glue.
Details on all this are in above mentioned thread.
The 3in. will need to be cut shorter to fit into upper stage, since we are moving it's location from inside to outside/on top of the 5.5 coupler




Done all sanding & fitting parts on mine, just waiting for some extra's so I can start....needed stuff like motor retainers, Y-harness etc.
Used the down time to re-think several options . Be starting soon.

 

[Wallace]

Mad Cow Nike Tomahawk came today...much larger than I expected. Here is the built Nike-Apache hiding amongst the parts & it's 5ft tall assembled!
Nicely packed & shipped well.
This kit features 75mm motor in the 5.5 diameter booster.
54 mm motor in the 3in diameter sustainer.
I will add 3/16 brake line for conduit & 1/4 in. sized parts/hardware.

My guess is add about 4 to 4.5 lbs for glue, hardware & recovery to the part weight of 16 lbs for a total of around 20 to 20.5 lbs finished. We'll see how close I get...... lol

I'm hoping to match this with motors that can keep it in the 4-6,000 ft level for home field flying fun!! I think I have a sweet spot weight wise so we will seeeee.....

View attachment 367679




Basic parts ...

View attachment 367670
Weights shown on sustainer are in LBS 1.5lbs etc.[ not lbs. and oz. like 1.8 ] in pencil next to letters
Weight on Booster parts are in grams.
I bumped a setting with a heavy part on my tiny scale.

Total weight of parts [kit] no hardware/glue/etc is 16.10---- sixteen lbs. & 10 oz.

View attachment 367677


ALL fins came stuck together from 2 sided tape glue residue. Used butter knife to pry apart, and clean with Xylene, Made quick work of gunky residue. WD-40-Acetone-Laquer thinner all work well also.
View attachment 367669


Parts that come are shown above in full pic of Interstage/coupler [I/S]
Below I added 2 coupler BP's & 2 BP's to make av-bay lids.

This I/s in not like the one with Nike-Apache, & is going require re-thinking the entire build of I/S electronic bay The 2 CR's are very sloppy and were designed to fit inside the coupler...not on top of lid...like the Apache.
I must figure out to center one on the BP...not the same outer diameter.

View attachment 367673


Both sets of slots & fins for both Booster & sustainer do not fit.
All slots needed opening more, filed one side [same on all] of slot.
View attachment 367674

The parts are high quality, just some extra work compared to the N-Apache, where everything fill well.
Hope you guys don't get as bad a fit between the I/S transition & coupler like mine.I spent almost 2 hrs sanding there 2 items. Mine was not close to fitting I/S but perfect in the body tube.

So ya know exactly where the issue was...the I/S not coupler. But I figured split sanding between the 2.

Needed to sand both outside top 1.5in of coupler & inside of I/S transition substantially.
Spent 4-5 hours just opening slots-cleaning glue residue--fitting basic parts, so they will work.

Tip:
To evenly sand a tube/coupler mark around with pencil....then sand off marks & stop...check fit....mark more sand ...repeat till fits. This ways you sand equal amounts off object as you only sand through the pencil marks.

First I measured depth of I/S that coupler would fill...drew line around coupler by inserting into airframe up to my mark and penciling circumference.
Did my scribble lines and sanded them off.
Inserted coupler into I/S went to line closest to edge.

Seen with second set of scribble lol ...ready for 2nd sanding.
It took a third before I had a smooth fit and 2 sanding on the inside of I/S Yeah it was a cr-- ton of sanding.

View attachment 367675

I feel for Ya. My Nike/Tomohawk was the same way, not even close. Fortunately I have a lathe and it only took a few minutes. Think I removed a bit over .030" from the transition I.D., it was that far off. Couldn't imagine having to sand that much. Keep up the good work...

 

[blackjack2564]

Build has started link to first post; https://www.rocketryforum.com/threa...ager-75mm-to-54mm-motors.149523/#post-1835719

Decided to do I/S first.

 

[Wallace]

Started build after acquiring needed av-bay hardware.
Using #10 [3/16] all thread for tie rods in Interstage coupler [I/S]
Glued all av-bay lids together and drilled most of needed holes.
I decided to start with most difficult aspect of build & get it out of the way.

View attachment 368759

Next measured & installed tie rods , drilled needed holes for separation charge & apogee main deploy.
3/6 bit and 7/64 bit. I chamfered entrance to seperation hole to make feeding charge wire through coupler into bay easier.
Tie rods centered 3/8 from edge of CR...mine yours may be a bit different.
As you can see my CR doesn't go to edge of BP, so measurement from edge of CR!
Be careful! You only get one shot at many of these steps.
The top av-bay lid consists of coupler BP...BP & the CR glued together.
I wrapped tape around CR to build it out same as the BP, then removed tape after gluing together. Keeps it centered correctly.


View attachment 368760

Using one hole for 2 charges. Began doing this recently, [on all builds] to keep from having to seal another hole from charge gases.
View attachment 368761

Tie rods are 8 1/4 inch long. Line is for my glue stage to make sure shroud is on level, not cocked.

View attachment 368764

The kit design calls for mounting the I/S coupler [3in] into the 5.5 coupler with the 2 CR's.
We will be mounting the 3in coupler on top of bay, not inside so coupler is 3 1/8 too long...
I place MM tube, fin - motor mount CR in position & dry fitted the 2 stages. as you can see where I XXX out is what needs to be cut off. Shined flashlight through tube, why it looks strange..lol

View attachment 368762 View attachment 368763

Done for tonight, must cut tube tomorrow out in shed, not heated and cold out there....49 outside!
Will glue it up after trimming to proper size.

C'mon Jim! You getting old or something? 49 degrees should be considered a blessing this time of year. We're supposed to see mid to upper 30's later this week so I'm planning outdoor tasks accordingly. Thanks once again for documenting and sharing all your work. It does not go unappreciated.

 

[blackjack2564]

I/S coupler Part 2 finished.

https://www.rocketryforum.com/threa...ager-75mm-to-54mm-motors.149523/#post-1835720

Yeah I am getting old, cut this geezer some slack...will ya..lol If you are nutz enough to enjoy working in the cold, more power to ya.I moved South to get away from it!
Your welcome, I enjoy doing it.Hope it saves others with this kit some headaches, and figuring out how to do stuff.

 

[Cameron Anderson]

Is your design incorperating a charge to separate the sustainer from the booster or are you relying on drag alone?

 

[blackjack2564]

Yes, there will be a separation charge to guarantee separation.
However, so far in all my 2-stagers careful fitting and squaring up of all components, has assured separation at motor burn out, with slip fit/drag.
But you never know if something may bind or hang up.
I use the Pet-2 timer as default setting fires charge at motor burn out.
Timer is in I/S along with altimeter that fires main at apogee.
No dual deploy for booster, I use K.I.S.S methodology....keep it stupid simple!

I have finished the I/S hole drilling and moved on to next hardest assembly...the motor mount/conduit in sustainer.
Will post all those after installed.

 

[Cameron Anderson]

Okay, you're design is very similar to what I plan on doing - alt in the IS for an apogee deploy, except I'm using a JLCR too. As for the timer, I'm also using a PET2 but it's going in the sustainer. I'm popping the sep charge MECO +1.0 and at MECO +1.5 I'm starting to light the sustainer so I to be up to pressure by +3.0.

 

[blackjack2564]

Curious...why putting the timer in sustainer & dragging booster with it for 1 sec ?
Are you using 2nd timer in Pet-2, to light motor?

 

[Cameron Anderson]

The 1 second (hopefully) who allow for drag separation to occur (the times charge being a back up). Also, I don't want to risk early forced sep under boost and affect flight stability. First flight timing of events is very cautious and then I tighten up on subsequent flights to really push efficiency and altitude.

I'm only using one timer - output 1 is sep charge and output 2 is sustainer motor ignition. I use a dipped e-match with a half second of current flow to lite it so I put my timer in my sustainer in the event drag separation occurs before I have a change to try to light the sustainer and the booster falling away (with the timer) falls away and yanks the ignitor out on the way. I pay a weight penalty in the sustainer putting the timer there, but it's worth it for the security in knowing that there is zero chance of messing up sustsiner motor ignition with early sep.

 

[blackjack2564]

Umm Cameron, I was afraid of that, you may wish to re-think using a timer for starting a sustainer motor.
It can be very dangerous if things go wonky, once the timer starts there is NO stopping it.

You should always incorporate a safety check of some type such as: motor won't light unless 1500ft altitude reached...... or velocity of 500feet per second .................or tilt less than 20 degrees.
Timer cannot do these things.

A RRC3 is only 70 bucks and can. There are others out there..I just use the RRC3 and Tele products which can do what I described.
You may find many launch sites that will NOT allow HIGH POWER staging, with timer only & Tripoli may have put that in the rules...I'll check with Steve Shannon on that.

I know if I were the RSO I would not allow it to fly.
When flying 2-stage projects we as the fliers, must adhere to safety standards much higher than a single stage rocket & police ourselves.
We must be sure the pads are clear of ALL personnel, except that one arming the rocket

2 stagers are not twice as hard/complex...they are 10x more difficult to fly and as such, we must approach them with caution.

 

[Cameron Anderson]

Lots of people advocate the altitude and tilt inhibits, which I get. Marsa has a great new accelerometer add on that has several logic gates.
All my two-stages to date have been timer only, but theyve been J to I or H to G so there wasn't much of a chance to go wrong. The plan for my N-T is M to L so it might be time to get some tilt inhibit.

 

[blackjack2564]

Finished I/S coupler & started Motor mount conduit assembly and fin install:

https://www.rocketryforum.com/threa...ager-75mm-to-54mm-motors.149523/#post-1835721

I did check with Steve Shannon on Tripoli's ruling regarding timers;
As of now they recommend against it, especially high power 2-stagers, but officially there is no rule against it.
They feel same as I do, it's a must to use some type of safety check before upper stage ignition.

Remember [can't emphasize this enough] safety is high level concern when it comes to staging.

 

[cwbullet]

I moved a bunch of the staging - timer stuff to https://www.rocketryforum.com/threads/timer-staging-discussion.150035/

 

[blackjack2564]

Thank you Chuck.

Update on build progress here post 5:

https://www.rocketryforum.com/threa...in-build-2-stager-75mm-to-54mm-motors.149523/

Laying out booster fincan/motor mount turned out to be a bit tricky, and I use the extra CR from interstage to make 3 on motor mount.
I moved position of rear CR back to almost flush with rear of airframe. As ir comes shows mounting it next to rear fin slot3.5 inches inside tube & that's a no-go for me.

 

[markg]

More build progress as of Jan 1st 2019.

While glue dries and I do all 4 sets of sustainer fillets, moved on to Booster fincan.

First must mention the slots are 3.5 inches from rear of fincan. If I mount retainer on MM tube and insert into airframe up to slot, it's far enough up in there to cook interior of tube and rear CR from base drag sucking heat and flame inside especially during smoke delay burn where there is no thrust just drag during coast.

I want to inject so CR's must be tight on fins. We are back to everything being flush with rear slot & that won't work for me...Sooooo.... I used the extra CR intended for the I/S coupler.....no longer needed since the I/S has been converted into an av-bay.

Hey CJ,

Have you had any progress on this build? I've really got to get started on mine if I'm going to fly it at the end of April. So far all I've done is a dry fit and started building the electronics (Eggtimer stuff). I've also put together a McMaster-Carr order of all the hardware I think I need.

For this step, I can skip the extra CR if I just use a non-bolt on retainer right? I've never used a bolt-on retainer, this is my first 75mm MMT.

Thanks for your great instructions, I plan to follow just about all of them as I put mine together!

cheers - mark

 

[JDcluster]

Hey CJ,

Have you had any progress on this build? I've really got to get started on mine if I'm going to fly it at the end of April. So far all I've done is a dry fit and started building the electronics (Eggtimer stuff). I've also put together a McMaster-Carr order of all the hardware I think I need.

For this step, I can skip the extra CR if I just use a non-bolt on retainer right? I've never used a bolt-on retainer, this is my first 75mm MMT.

Thanks for your great instructions, I plan to follow just about all of them as I put mine together!

cheers - mark

I finished my booster about a week ago. I went with the standard Aero pack glue on retainer.
Scrapped all the kit Cr's in favor of custom cut 3/8" plywood that I made. The CR's were just too sloppy loose to use. The motor tube extends closer to the aft end 1.5" short to accommodate the added length with the retainer...

 

[blackjack2564]

Hey CJ, Have you had any progress on this build?
cheers - mark

Well, been busy fix'n screw ups lately. As long as I have been building these things, Murphy finally caught up with me.
Last set of fillets [external] on sustainer refused to cure for 2 weeks, same batch of glue was used to tack fins in Booster.
Then cat knocks over booster [fins at top, over heater vent, top heavy] at 3 am. that was fun, thought my other half fell down the steps.
Since glue had not cured, 2 fins knocked out of alignment. They had to be removed and re-tacked into position.
I started back yesterday after dealing with above issues.

3sets of internal fillets injected & rear CR filled.
As mentioned previously, I added a CR and moved the rear one back to help with base drag & scorching inside of airframe.





Getting back on track next few days.