LOC IV X2 Build

soupmanrmc · Sep 9, 2024

I wanted to gain experience in dual deployment, using an HPR kit with an avionics bay, this kit was a no-brainer. I wanted to document my build of the LOC IV X2 to get more confidence when the time comes for the future scratch build L3. What a great way to get input from the community, especially the seasoned veterans' ideas and things I may need to consider moving forward.

Both kits have a lot going for them and the LOC IV is no slouch on its own. An adapter can provide a lot of fun running F/G motors and have plenty of room for an L1 certification flight. However, I wanted to play in the L1/L2 with a 4" bird to exercise what I wanted to do with the platform, which is to experiment with DD, redundancy, head-end, etc. This is the primary reason for choosing the X2 (and my wife let me, which is probably the bigger factor).

LOC IV	LOC IV X2
Diameter: 4″ Height: 47″ Weight: 2lbs. Motor Mount: 38mm with MR-1 Retention Parachute Size: 36″ Ripstop Nylon Shock Cord Type: NW-15 15' 3/8″ Nylon with sewn loops (not elastic) Shock Cord Mount: SCM-3 Eyebolt Fin Thickness: 1/8″ Ring Thickness: 1/4″	Diameter: 4″ Height: 68″ Weight: 4.3 lbs. Motor Mount: 54mm with MR-1 Retention, includes LNRMMA38 38mm adapter Parachute Size: 42" nylon main, 15" nylon drogue Shock Cord Type: 2x NW-15 15' 3/8″ Nylon with sewn loops Shock Cord Mount: SCM-3 Eyebolt Electronics Bay: Included Fin Thickness: 1/4″ LOC-n-Fin Ring Thickness: 1/4″ LOC-n-Ring

Motor Mount
I love retainer rings, as I have adapters already to let me scale down to as little as 29mm. I thought about simply sanding the glassine (which I have done in the past) but opted to remove it this time. The initial dry fit of the centering rings and retainer ring was not successful. I pulled the very thin wrap off, but I still needed to do a bit of sanding. I started marking things up, as I have seen many do so to keep things organized during the build.

I have not measured where the rings go (except the retainer when I get ready to set it), as I am leaning hard toward building the fin can outside, as I did for the 4" Goblin since it allowed me to get the fillets on the MMT without a lot of extra effort later on. Besides, JB Weld is my friend with MMTs and I don't care about how ugly it looks when it is hidden.

I labeled the CRs and the fins to where each lined up during the dry fit. A LOT of sanding took place to get everything to fit nicely together. If you have a Dremel or other rotary tool, it can save hours!

Here is the dry fit for the can assembly. Tomorrow I will figure out where I want the forward CR (most likely 1/2" from the top of the mount) and then dropping some JB all over it!

soupmanrmc · Sep 10, 2024

Today I focused solely on the fin can itself. I tacked everything in place and finalized to position of the forward CR (I used the motor retainer to do the measurement

, which is a LOT easier than measuring taping, or marking. I opted for JB Weld (as I did in the Goblin). I did a nice clean fillet, then a few hours later broke out the popsicle stick (should be able to stand on it after a few days). The only long-cure epoxy I had was for glassing, so I opted to go with what I knew and worked in the past.

I also opted to use JB because of the temps in the application - it seems most epoxy gets soft at about 150F, and I have pulled my fair share of motor cases out and had to resort to more colorful parts of my Navy days. I am sure there are some epoxies with high operating temps out there (I always like to get good recommendations).

Yes, it is an overkill. However, an overkill is still a kill.

Pic #5a and #5b are the body tube tests of the fin can, which I do to make sure things line up, especially the airframe slots.

The next pics are the MMT meeting its destiny with the remains of the JB Weld tube; it had just enough to get it done. I did the little fillets to get things in the grooves using coffee stir sticks. The 54mm motor retainer (Aeropack via Chris' Rocket Supplies - I live in GA, so I shop locally as much as possible) is in place and will never go anywhere. I have made sure to wipe down all threads on the retaining ring with IPA, so what is seen in the pic does not affect the closure ring at all.

And the ugliness of JB Weld. Big fat popsicle stick applicator.

Tomorrow, I should be able to push it all into the tube. I need to decide on the rail buttons. Going with 1010 as the bird should be under 10lbs and is not too tall, but looking for placement.

Thinking mid and forward CRs. Thoughts?

soupmanrmc · Oct 2, 2024

The new tube came in, but the slots were cut for 1/8 versus 1/4. Did my best to expand them (straight line with a dremel was a challenge). Opened them up enough to get the fin can in - did a decent job on that part.

Fin can epoxied in. Will go back and add a deeper fillet on the forward centering ring, just for peace of mind.

First set of fin fillets epoxied (Total Boat w/ silica).

soupmanrmc · Oct 7, 2024

I did not like the initial fillets, since it appeared the epoxy was a wee bit runny and went into the body tube, which was awesome, but left very little externally which is not what I wanted. So I hit them with 80 grit and sanded them a bit to provide a better foothold for a second layer. So far, they look a lot better!

The 2nd photo is down the booster section. Can barely see the shock cord mount, but it is a 6" eye bolt versus what was provided. It allows me to easily reach in and change out the shock cord. To prevent zippers, I am using foam golf balls attached to the shock cord (props go out to cwbullet who posted about this once) and they work like a charm for 4" and under.

soupmanrmc · Oct 11, 2024

Fillets sanded, then hit with glazing putty. Not too happy with how it all turned out, so I did some sanding with dremel (very low speed) to do the majority, then hand with 80 grit. They are fairly smooth, but I should hit them with 220 to get the feathering right.

soupmanrmc · Oct 20, 2024

Primer coat applied and the glazing putty cracked. Entirely cosmetic. I need to sand the heck out of it....

soupmanrmc · Oct 22, 2024

Sanded the heck out of the fillets and got them respectable. 320 grit helped, but took a while. Wiped down with 91% IPA and let dry for several hours. Satin Black used as a base coat, drying overnight in prep for a final coat.