Build Thread - Loc Caliber ISP-38

My next build has officially been ordered, and as I really enjoyed documenting my WAC Corporal a few months back I figured why not do the same for this one. The rocket is a Loc Caliber ISP that will be built with a handful of modifications, namely the addition of an electronics bay to support altimeter based deployment, 1500# Kevlar recovery harness, a 38mm motor mount, and possibly fiberglass over the factory plywood fins. Decals are by StickerShock23, motor retention and rail buttons will be supplied by Aeropack, and adhesives will be mostly SystemThree T88 with some BSI 30min.

The motor mount will use the stock 54mm tube and will be adapted to the 38mm final dimension. The "adapter" will literally be an extended LOC adapter with a forward 3" - 38mm centering ring. Envision replacing the 38mm tube in the Loc adapter with an 18 - 20" 38mm tube and then securing a centering ring to the end. That whole assembly gets epoxied into the stock 54mm tube and then all of it, the two centering rings on the 54mm tube and one on the 38mm tube at the forward end gets epoxied into the airframe.

Why do all this when there is nothing wrong with the stock 54mm mount you ask? Several reasons:
-First a 38mm motor (up to an Aerotech 38-720 or Loki 38-740) will provide PLENTY of motivation for a rocket of this size (estimating 36oz finished)
-Second, I don't own any 54mm hardware
-Third, I am not a fan of using an adapter for 99% of the flights that a rocket will see
-Fourth, cuz I want to!!!!

The only thing I have yet to nail down is the altimeter and wiring. I am leaning to an off the shelf doghouse wiring kit, though I would like to use an internal "pull pin" style switch and not large external rotary switch they sell. I do like their charge canister set-up and will likely use them. This will use a single altimeter so no redundancy will be employed. I originally wanted to go with a Strata-Logger CF, however I may end up with an RRC3 if the CFs remain unavailable. No worries there as the RRC3 is a proven piece and will easily handle the limited g-loads that I anticipate.

Finally I am leaning toward a gloss white paint scheme with a pair of light purple fins and a pair of gloss black fins with either a purple or black nose cone. I will be using the stock purple/green/yellow wrap for the payload bay and stock lettering for the name with some creative "stock like" decals around the fins / fin can. the rocket will receive 3-4 coats of clear prior to the application of the deals.

So yea, that's it for now. Everything save for the electronics were ordered yesterday, and in speaking with Mark at StickerShock, I understand that the decals shipped out yesterday as well. Talking about a 6 hour turn around time. He is truly amazing! I don't have a launch scheduled for a few months so I really have some time for this one.

The parts are here. I forgot to put the Aeropack pieces on the table for the picture:-/



Huge kudos to Mark at StickerShock. Can’t wait to finalize the decal layout

Made some progress on the motor mount assembly. Coming together as planned. The forward and aft rings on the 54mm tube are doubled to provide more area for the rail button screw to bite into

How are you attaching the recovery harness to the top ring? Are you going to put a screw eye in there or using a ring attached to the motor case?

There is a notch cut in the forward most ring. The Kevlar will pass through this notch and will be knotted and adhered to the 38mm tube

I'm a little confused as to why you have a 38mm MMT glued inside a 54mm mount.. Why not just add 3 CRs for the 38mm MMT and forgo the 54mm tube & rings. Doesn't that just add extra weight?

I usually just add a chunk of wood the CRs for button attachment, then align them and mark their position in the tube. No need for a full ring (again, added weight) Or, a full ring, cut into quarters will suffice..

good question. using the 54mm tube allows me to use the factory fins (the tabs will not reach a 38mm tube). didn't really want to get out the table saw and cut new fins to fit a 38mm tube, and given the motors I intend on using, I definitely want the fins anchored to the mmt.

it does add some weight, but I'm not building a record setter. I do like the "small piece of wood" idea, however, I was concerned that I would not have enough room as the gap between the 54mm tube and the inside wall of the airframe is quite close. yes I could have cut one ring into smaller pieces, but, well, I didn't.

Epoxied in place

Making progress on the fins

None of the 54mm motors are hazmat free. That’s your new cool excuse for going 38mm! Yeah you’ll love hazmat free Loki and Aerotech 38mm H, I, and even J class reloads. Anyways I hope this flight turns out way better than your WAC did.

I hope so too my friend!

That was a real heartbreaker to be sure

Using T88 for the fillets. Can’t say that I am happy with it. Don’t get me wrong, it is strong stuff and great for the mmt and fin roots, but the very long cure time requires a good deal of “baby sitting”

Yes I could add something to thicken it, but I am really not a fan of adding elements to the proven system

Progress...

Some pictures of the next round of fillets as well as the “micro bevel” that I put on each fin

I’ve got one more set of fillets then I’m going to work the electrics bay.

Moving forward. With the fin can complete I am now working the electrics bay and payload/ coupler assemblies.

I thought long and had about this, and with the “double coupler” method that LOC uses for their e-bay kit I chose to take out a little “zipper insurance.”

I started by epoxying a standard coupler in the top of the airframe and another in the bottom of the provided payload bay. I then took the “stiffy coupler” (very rough from LOC (that is by design but wouldn’t work well here)) and sprayed it with three good coats of clear enamel. After letting this dry for three full days a sanded it with 320 then gave it two mor light coats. This was allowed to fully dry again before being sanded with 400 grit. What I now have is a glass smooth electrics bay that will easily slide in the “thicker” airframe.

This treatment of the coupler is exactly what I did for the shoulder of the nose cone on my WAC Corporal build (it was a standard coupler that went over the shoulder of the balsa nose cone) and it worked great!





The “doubled” switch band using the provided piece of airframe and a piece of coupler



To ensure that the end plates are easily centered I cut two circles out of .125 bass wood that match the inside diameter of the stiffy coupler. These were adhered with tite bond II and then everything got a few coats of flat white.



This is as far as I can go until funds allow me to order the RRC3 and associated pieces

I am thinking of permanently adhering the electrics bay into the payload bay as there is very little space between the top of the e-bay and the bottom of the nose cone. Even if I modify the nose cone it will be a decent effect to fit the chute, shock cord, nomex blanket etc. in there.

The new plan will be to use the altimeter for apogee deployment and a JLCR to deploy the main.

Whatcha all think?

Next up is priming and finishing the booster and nose cone.

Sanding and filling

Priming

Filling and sanding

Priming

And sanding...

--- update ---

priming and filling of the booster section is complete and if all goes well should get shot with several coats of high gloss white this weekend

I also pulled the trigger on the RRC3 and all ancillary items to include the missleworks screw switches. once the AV bay is complete I will be epoxying it into the payload bay as discussed in post 14, and then I will finish the payload bay, switch band and nose cone.

after that it will be time for decals, clear coat and then the H148 that's hanging out patiently in the range box.

Good-looking rocket!

All that filling and sanding has paid off.

Chuck C

From primer white to



High gloss white. This is after three good coats. I’m going to let it fully dry for three days and evaluate. Might wet sand it and hit it again

Nice

My Caliber weighed 50 oz prepped less motor, got the following altitudes
Alt Motor date
2508 I218 9-4-10
2785 H999 1-9-11 Main shook out at apogee, tree recovery
2760 I245G 7-4-11
2630 I250 (38/480) 11-13-11
2756 I204 12-10-11
3428 I73 (38/600) 4-15-12
3930 I85SS 9-3-12
5797 J220 (54/852) 11-11-12
7487 J330 (54/1280) 12-9-12
4227 I284 3-9-13
4655 I85 6-1-13
3066 I1299 6-8-13
3366 I211 7-13-13
4113 I366R 9-2-13
4747 I100 CTI 10-12-13 New Missileworks RRC3
3232 I85 4-13-14 Pad shifted, a mile downrange
2345 I218 6-8-14
? 3g38 ex propellant 7-4-14 No data on RRC3, correct deploy
682 I85 7-6-14 Burnthrough, booster destroyed

I85 fits 38/720 7 sec burn, 580 N-s
J220 800 N-s, J330 1200 N-s

Cool deal. Thank you for sharing your flight data

I am estimating 55oz but will have the final numbers soon. The e-bay with the stiffy was heavier than anticipated, and I have the added weight of my modified motor mount. No worries though, a few extra ounces won’t kill this one

What were your impressions of the H999 and I1299? Looking forward to flying both

Thinking buying a CTI 29mm 6xl. I’m a fan of high length to diameter motors and that guy fits the bill for sure!

Theory said:

The parts are here. I forgot to put the Aeropack pieces on the table for the picture:-/

View attachment 380666

Huge kudos to Mark at StickerShock. Can’t wait to finalize the decal layout

Click to expand...

Looks like you have more stickers than rocket...

Yea, when I ordered the decals I was “between designs.” The extra decals gave me more options

...I like options

Breaking up the white:



The opposite fin will be gloss black.

Once that is complete it will be time for decals then several coats of high gloss clear

The booster’s paint is complete and the retainer is installed

Unless you’re going wicked high, just do single deploy with a chute release. Save money, annoyance, and space. Doing the same with my 5.5 LOC Phoenix since any motor over a 54mm J sends the stability too far in the opposite direction to balance it (not sure why it comes with a 75mm mount either, waste of space).

Yup, that’s the plan! RRC3 for apogee deployment then the main on a JLCR

Time to move this build along!

Sled complete. Need to execute some final soldering and it will be ready.

The screw switch is easily accessible via a static port and I left room as to not negatively impact air flow




Next up is the bulk plate with the copper charge well.

The e-match will be hard wired directly to the altimeter using a pass-thru in the bulk plate

That's looking really nice, I like your choice of colors and paint scheme. Painting the Av bay was a nice touch as well, such a clean looking rocket!