Build thread: 1 x 54mm + 2 x 38mm in a 5.54" airframe

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Dry fit after initial sanding of CF on booster. Also sealed back plate with a coat of JB Weld (slightly diluted with some isopropyl alcohol).

20181210_185459.jpg
Still a bit of 120 grit flatting to do before I start moving up through the grits, but it's getting there...
20181210_203227.jpg
 
Over the holidays I took a break from the airframe, which is more or less ready for painting, and finished the Av bay... conventional construction using M6 threaded rods. AV bay 1.jpg

...and a plywood sled:

AV bay 3.jpg

I make charge wells using 5/8" brass tubing, and the screw tops from some cheapo pill containers:
AV bay 2.jpg

The two parts bonded with JB weld. The little peg is then inserted into a corresponding hole drilled in the plywood bulkplate, which anchors it nicely...

AV bay 4.jpg

Charge wells and terminal blocks attached to the aft bulkplate, painted with Hammerite and labelled with decals. I seal the decals with a few brush strokes of epoxy:
AV bay 5.jpg

The forward facing bulkplate:

AV bay.jpg
Switch band sprayed with satin black and epoxied into place:

AV bay 6.jpg
4 x M5 static ports drilled, and 2 x Binder Design's excellent screw switches installed:
AV bay 7.jpg
 
That's a very neat bulkplate setup, I like it!

What is hammerite? Methinks something commonly used on the east side of the pond?
 
That's a very neat bulkplate setup, I like it!

What is hammerite? Methinks something commonly used on the east side of the pond?

Yes it's just a commonplace thick tough paint. In it's 'classic' form it comes in a variety of metallic colours and dries with a sort of ball pin hammered appearance. It's actually formulated for metal railings and that sort of thing, but I like it spread thickly on bulkplates. I didn't realise it's not known in the US - it's just one of those brands that over here everyone knows immediately.
 
An update on weight.. obviously I was always mindful that given its relatively short length and construction this was going to be heavy at the back end. I'd held off work on the nosecone until I knew the final weight, so I did some checking on the booster section now it's more or less completed. My original OR file predicted a dry weight of 2.035 kg...Screen Shot 2018-12-14 at 09.22.39.png

The actual completed weight wasn't too much over that, at 2.12 kg

20181219_141755.jpg
 
...and so to an update on some nose cone work I've been doing over the past 2 days....
Back in the summer when I was thinking about this project, I made an NC weight cartridge out of an off cut of FWFG 54mm tubing and lead shot/epoxy caviare (here it is standing on a 'pedestal' of a used Pro 54 nozzle):20180816_174656.jpg

The threaded bar runs through the centre, and projected out at one side (this is the other side, where it's flush with the nut):20180816_180707.jpg
The cartridge secured with epoxy at the end of a length of phenolic tube:

20190103_121148.jpg

The basic Loc NC (it's one of the 5.54" Long ones) was then adapted using the Coker method...
Coker CR in NC.jpg

A good chunk of Milliput (if this too is unknown to some TRF'ers,'tis a wondrous epoxy putty, water soluble when wet, that dries rock hard) was then dropped into the nose tip, and pressed into shape using a dowel. By pouring measured volumes of water into the NC and holding it up to the light I'd estimated the volume needed as 75ml..Clay in NC tip.jpg
Before the putty set, the phenolic tube with the cartridge was then pushed through the CR so that the projecting thread was firmly anchored in the NC putty.

The tracker will be fixed on a tray that rides on the legs of the NC U bolt. This is 3mm ply backed with FG. In this shot it still needs a bit of fettling, as you can see...


20190104_170106.jpg

Here's the NC bulkplate being secured with M4 slot heads:

NC bulkplate being fixed.jpg
I also pinned the CR from the outside using some smaller, M2.6 machine screws epoxied in. I imagine this is overkill, but it was part of the original plan when I was describing it to my club's RSO. The whole thing feels very solid.
20190104_165256.jpg

I'm hoping to ground test shortly. Calculations suggest I'll need 3 x M3 nylon screws as shear pins. Earlier today I drilled appropriate holes in the NC shoulder, and I'll cut and fix some brass shims over the weekend.
 
Just popping in to say that I'm enjoying your build thread! Love how your build is unique and you're doing it "your way".

Sweet looking cluster bird!
 
Just popping in to say that I'm enjoying your build thread! Love how your build is unique and you're doing it "your way".

Sweet looking cluster bird!
Thank you! Scratch building has its pros and cons and as you can probably see I'm feeling my way to some extent (eg if I started this build over again I'd probably use FG rather than CF). It's partly due to the scarcity of stock kits here (in terms of Loc or PML anything bigger than 4" is very rare). Basic components are easier to come by, and there is now a UK source of phenolic airframes, but it's still a small market. Big nose cones are always hard to come by - I was lucky to get this one.
 
Images from ground testing in a not-too-muddy field at the EARS range earlier today. 4g of FFFFG BP blew the NC well clear and got the chute out (NC secured with 3 x M3 nylon screws as shear pins):
20190106_134933.jpg
2.5g was plenty sufficient for the booster section / drogue charge:
20190106_131325.jpg

Now it's got the whiff of sulphur about it, it feels like a working machine...
 
...a pic I should have added earlier this weekend, showing the completed brass shims attached to the NC shoulder with JB Weld. There are three in all, evenly spaced (of course) around the circumference. The piece of tape was for alignment purposes during the testing today.
 

Attachments

  • 20190106_212915.jpg
    20190106_212915.jpg
    100.2 KB · Views: 110
Read the build & pretty darn impressive Tim.
With the 3 gr blue and my guess for full up flight weight[6-7lbs], you will have 15-20 to 1 thrust ratio...perfect!
When you get mellow load take care of starter the head for them are very tiny and impossible to replace. Nozzle is so small.
Mellow lights very easy being a bates grain, rather than moon burner, like most long burns. Due to BP pellet in top grain they light fast...great for airstarts. I could not find what electronics you will be using for your project, but generally most have a .5sec. lag from time you want, to time you get. keep that in mind when figuring delay for airstart. Time you mention sounds on the money for a 1 second coast.
 
Last edited:
Read the build & pretty darn impressive Tim.
With the 3 gr blue and my guess for full up flight weight[6-7lbs], you will have 15-20 to 1 thrust ratio...perfect!
When you get mellow load take care of starter the head for them are very tiny and impossible to replace. Nozzle is so small.
Mellow lights very easy being a bates grain, rather than moon burner, like most long burns. Due to BP pellet in top grain they light fast...great for airstarts. I could not find what electronics you will be using for your project, but generally most have a .5sec. lag from time you want, to time you get. keep that in mind when figuring delay for airstart. Time you mention sounds on the money for a 1 second coast.

Thanks for looking over this Jim - I very much appreciate your input and the kind words that I'm on the right track. The electronics will be an RRC3 as prime with either a SLCF or an RRC2+ as back up. I had something of an 'of course - hadn't thought of that!!' moment regarding the I55 igniter/nozzle issue - thanks for raising it. I was planning to solder JST connectors to the starter leads at some point, unless twist and tape would be a better option... again, I'm open to advice on that one.
 
A little bit of work on the Av bay sled, and the NC sled (all 3mm ply). NC bay will hold a Eggtimer Mini Tx. As mentioned in my earlier response to Jim Hendricksen, the Av bay will be fitted with an RRC3 Sport and an RRC2+. Holes drilled:AV & NC sled 1.jpg
(quite like the golden afternoon light in this pic...reminds me of Scotch whisky ads for some reason. 'These sleds have been aged for 12 years, for an extra mellow taste..') The larger holes are for the battery leads to feed through, as I tend to strap the batteries on the opposite side of the board to the electronics. Holes for zip ties then filed to an appropriate shape using a square needle file:AF & NC sled 2.jpg
 
I cut a bit of the female [receiver] side of JST with razor blade/box cutter, to make it a bit easier to disconnect in smaller/lighter rockets. [apogee event]
DSCN1299.jpg DSCN1300.jpg

Just an overhand knot in JST wire on inside of BP for strain relief.
Black line to mark which side is same for alignment of connector. Ejection charge in glove tip pulled aside for pic.
Sticky tack, to seal holes in BP, from gases.

DSCN1303.jpg
I use twist/t also . Haven't decided which I like best, [even after all these years] Suppose they each have their place depending on use.

Which ever style you get the best connection & nice slippery separation. Most of the time, wire on supplied starter is long enough to reach connection point for small-medium projects. If not [and nozzle diam. permits] I will just swap out for a longer match/igniter and use that.
I try to keep connections at absolute minimum when possible.

When packing chute and cord I lay fincan horizontal pull pyro wire snug to bottom of tube, & slide my burrito/chute/shockcord on top of wire. Keeps things from tangling during deploy.
Only leave enough excess wire to place av-bay/payload on top of fincan comfortably, usually about 12-15 inches.
That's my little ole technique.
 
Last edited:
I cut a bit of the female [receiver] side of JST with razor blade/box cutter, to make it a bit easier to disconnect in smaller/lighter rockets. [apogee event]
View attachment 373642 View attachment 373643

Just an overhand knot in JST wire on inside of BP for strain relief.
Black line to mark which side is same for alignment of connector. Ejection charge in glove tip pulled aside for pic.
Sticky tack, to seal holes in BP, from gases.

View attachment 373644
I use twist/t also . Haven't decided which I like best, [even after all these years] Suppose they each have their place depending on use.

Which ever style you get the best connection & nice slippery separation. Most of the time, wire on supplied starter is long enough to reach connection point for small-medium projects. If not [and nozzle diam. permits] I will just swap out for a longer match/igniter and use that.
I try to keep connections at absolute minimum when possible.

When packing chute and cord I lay fincan horizontal pull pyro wire snug to bottom of tube, & slide my burrito/chute/shockcord on top of wire. Keeps things from tangling during deploy.
Only leave enough excess wire to place av-bay/payload on top of fincan comfortably, usually about 12-15 inches.
That's my little ole technique.
Brilliant - thanks very much!
 
Familiarising myself with programming my new RRC3 with the USB-IO and the mDACS software in preparation for the first flight. Screen shot of (what I think is..) an advanced timed airstart event at 3 seconds where the rocket's altitude has to be at least 500'. Drogue at apogee, main at 700', which I prefer over the default 500' setting.RRC3 Airstart J449 2xI55.png
 
I've finally decided on a name for this rocket and a colour scheme: Clear Air Turbulence. The paint job will be a (much) simplified version of the starship's yellow and black banding - probably just two broad ones and two narrow ones towards the aft. Here's the forward assembly of NC and payload:NC + payload assembly finished.jpg

At some point I'll get a decal made of the name in the same script as on the album cover. The yellow tag on the camera shroud is just masking tape and is not part of the scheme.
 
I don't know how I missed this thread! Fantastic building skills and a really good thread. Very informative!

Thanks for sharing it!
 
Absolutely cool and novel approach to clustering/airstarts. You've inspired me to get back to finishing up the odd bits on my LOC Ultimate (mostly drilling necessary holes, wiring up e-bay and learning how to program my new timer). Even though they're not very cost effective there's just something about clustering that draws me in....Thanks for the build thread and inspiration. Keep up the good work and don't forget the all important flight report..
 
Some painting: payload bay primed with deep fill primer, then satin black with chequerboard pattern. Chequerboards are scientifically proven to make rockets go faster. Mobius camera shroud from Additive Aerospace sprayed and epoxied on.

View attachment 375361

So THAT's how they do it! If only my masking skills were up to making checkerboard patterns.
 
Chequerboards are scientifically proven to make rockets go faster

Wrong!
It's actually flames that make rockets go faster (like cars)

Pinstripes: Straighter flight (only if applied lengthwise)
Spirals: Impart spin (may lead to coning)
The checkerboard effect is highly debated. May imbue the rocket/car with better strategy
 
Absolutely cool and novel approach to clustering/airstarts. You've inspired me to get back to finishing up the odd bits on my LOC Ultimate (mostly drilling necessary holes, wiring up e-bay and learning how to program my new timer). Even though they're not very cost effective there's just something about clustering that draws me in....Thanks for the build thread and inspiration. Keep up the good work and don't forget the all important flight report..
Thanks! Given the recent rash of catos at our club I'm half expecting the flight report to be a cato report... especially given that clustering inevitably raises the odds. But either way I'll report back. I'm looking at a launch in early May. Good luck with your Ultimate build.
 
Wrong!
It's actually flames that make rockets go faster (like cars)

Pinstripes: Straighter flight (only if applied lengthwise)
Spirals: Impart spin (may lead to coning)
The checkerboard effect is highly debated. May imbue the rocket/car with better strategy

All good points. I see a co-author credit for Modern High Power 3 in your future. However painting flames on the side of a rocket can also cause unnecessary fire panic and stampedes amongst spectators and shortsighted RSOs.
 
So THAT's how they do it! If only my masking skills were up to making checkerboard patterns.

Well I have to be honest and say these took me more than one attempt. There always seems to be bleed through, especially when using car paint rattle cans. What I generally do is mask twice. Draw a line with an angle iron to align the masking tape squares in, say white, spray, leave to dry, peel off. Then when the paint's fully cured, rub over with 2000 grit, mask off the white squares squares and spray with black, to paint over the bleed through. With that kind of carry-on, a 4 square deep band goes to the full limit of my patience...
 
Masked up the booster for stripes, and primed ready for the yellow. The black on this section will largely be the CF weave, with a coat of clear lacquer.

Booster primed.jpg
 
Painting going a bit slow at the moment due to the changeable weather.. so it's still a work in progress. In the meantime I've been checking things over and trouble shooting. I noticed that loaded up with the drogue, shock cord and three motor casings the booster section is prone to slipping slightly, so that a gap appears between the switch band and the booster lip. Drilled three evenly spaced shear pin holes around the edge of the aft AV bay bulkplate, and inserted brass tubing, secured with JB Weld and filed flush with the rim.

20190405_205930.jpg

3 x M2 nylon screws, serving as shear pins, inserted. If the weather picks up I'll do another ground test over the weekend to re-check the required separation charges.

20190405_205344.jpg

The forward rail button nut was also protruding into the airframe, being situated in front of the MMT CR - it looked a little vulnerable so I made and shaped a backing kerf out of ply:

20190405_211150.jpg
 
Back
Top