Rich's 4" Loc V2 build

[rharshberger]

Just getting started with a V2 build, and as I am a huge fan of cardboard (and Loc products) it is of course the Loc Precision 4" version. Of course I am planning a few mods to the kit as I go, hello its me after all!. The first steps have been kind of skipped over as I was unsure whether to do a build thread on this rocket.

The motor mount rear CR and motor retainer are already installed. The motor retainer is a GLR 38mm Slimline Threaded, and the rear CR has been tapered to allow it to fit flush with the rear of the boattail. US Composites 150 was the epoxy used to mount the CR to the boattail, and Titebond II between the CR and the MMT, the retainer was affixed using JB Weld as normal for most retainers.

The rear fin tabs were shortened about 1/8" to maintain the proper fit of the fins to the curvature of the boattail.

On with the build,

The epoxied in place MMT, rear CR and Slimline



Another view of same unit.


Notice the out of round plastic of the boattail, the following steps were used to make sure the MMT stayed centered, and so that the forward CR could be removed for filleting purposes. All wood to paper bonds will be made with TBII, all plastic to wood or paper will be either US Composites 150 or 635 epoxy modified with milled fiberglass, the fins to Slimline will be affixed with JB Weld.


A short section of scrap 4" airframe is used to allow the forward CR to help bring the egged boattail back to round and to center the MMT while the epoxy cures.


Another view of above configuration, the assembly was stood on the MMT to allow gravity to keep the tapered rear CR snugged up flush with the rear of the boattail. In the words of Batty Koda "Gravity Works".



Once the rear CR epoxy cured it was time to add some brass pins to add additional mechanical locking of the rear CR to the boattail. The holes were pre-drilled and a piece of K&S Brass rod was used to make short pins into the rear CR similar to how I attach noseweight to the nose cone.



Slimline taped off for filing away the anodizing prior to bonding the rear fin tabs to the retainer with JB Weld, after filing and then sanding the patches to be bonded were immediately coated with a thin layer of epoxy to prevent oxidation of the aluminum. Filed patch is visible in next photo between the fins.


First two fins attached, a section of aluminum angle is used to align the fins, the 4 fin configuration of the V2 and its fin shapes make aligning them at perfect 90degree angles easy. Simply attach the two opposite fins and use something straight across the trailing edges, clamp the straight edge to the fins and wait for them to cure/dry.



Still trying to decide whether to make this one dual deploy or not, if I do the Av-Bay will be a donut style and the nose cone will be the forward parachute bay, the Av-Bay will be the separation point, and the standard airframe will be separated into a 4" long section attached to the nose cone and a 7" section attached to the boattail, a streamer will be used instead of a drogue chute for apogee deployment. Using OR I have simmed the rocket using motors from a RoadRunner F60 (I have a couple left) to a AT 38/1080 J825, electronic deployment is a must in the case of the F60 (due to short delay time).

 

[Red Phenix]

Lovely craftsmanship. Thank you for sharing and lending your expertise vicariously to others.

Well done

 

[Nytrunner]

More boattails, nice!

I will throw out one vote for donut AV-bay (with a good write up of course).

 

[rharshberger]

Did a bit more work on the V2 this evening and made a couple of tools too.

Internal Fillets all done at one time, the epoxy is US Composites 150 3:1, about 10 grams epoxy and 10 grams of milled FG and maybe 2 grams of fumed silica, the stuff will not run at all, hence the ugly fillets (they are internal and will never be seen again once the forward CR goes on. I kept the fillets to about 3/16" radius or so in an effort to keep the weight at the rear of the rocket down.



The next two pictures are my internal fillet tools, they are made from a section of 18mm Baltic Birch about 6mm thick (left over from another project then ripped sort of down the middle). The tips are popsical/craft sticks epoxied on a cut angle, the left stick is about a 45 degree angle and the right side closer to 30 degrees. These two tools took like 15 minutes to make, most of it waiting on the Bob Smith 5 minute epoxy to cure.





Fin can with all four fins attached, external fillets will not be done until the aft airframe section is attached, maybe tomorrow or so. I also poured about 4 grams of US Composites 150 3:1 on top the rear CR for additional bonding.



Two pictures with slightly different angles of the Slimline and fin interface, when I do the external fillets everything will look much better.

 

[mcderek]

Looks great Rich! Will it fly at Sod Blaster?

 

[Steve Shannon]

That does look good!
I’ve built internal fillet tools very similar to yours using chopsticks with popsicle stick tips.

 

[rharshberger]

Looks great Rich! Will it fly at Sod Blaster?

Probably not, build time is going to be scarce, between now and Sod Blaster. I have to finish the clubs fire suppresion tank (250gal tank that fits in my pickup), plus a bunch of other stuff for Sod Blaster, we get the new puppy a week from Sunday so stuff to do puppy proofing the house, and I have to build shelves in the new shed and get stuff moved into it, and I am currently working 6 days a week.

 

[rharshberger]

Worked some more this evening on the V2, it was a long day of 11.5hrs of work, mowed the lawn when I got home and watched a little of The Dark Knight. I decided while watching the movie to do a little work then off to the garage for a bit for some quick and dirty fab work.

Some of the parts, the casing peeking out is a 38/760 (the longest I currently own in 38mm). The fin can is close to ready for final assembly, the lower airframe (longer piece) needs a narrow wrap of FG for the shear pins as does the upper airframe shorter white piece. Given some of the motors I plan to fly in this rocket shear pins are necessary especially with up to 8ozs of nose weight (4-5oz permanent, and then some removeable for smaller motors). The donut bay coupler is sitting on top the upper airframe section, the upper airframe will be permanently attached to the short nosecone shoulder. I am guessing the nose cone is polyproplene given the way it sanded after cutting off the shoulder and base.




Nose cone anchor and removable nose weight mount, the tip will be buried in the Loc noseweight along with two cross pins and epoxy. The non-grooved section will be where the lead washers (made from 2oz disc fishing weights most likely) will slide over the shaft and be secured by a steel washer below the eyebolt.


View of the nose recovery anchor in place with cross pins, if you haven't had a chance to watch the video John Coker has a great tutorial on installing nose weight into plastic nose cones. Due to the lack of good chemical bonding the nose cone has been scored heavily with 60 grit sandpaper and the cross pins will act as a mechanical lock to hold the anchor and weight in place. As I do not own or have access to a metal working lathe the anchor was made on my larger drill press, the groves cut with a hacksaw and file as the rod spun. One of these days I will acquire a metal lathe to go along with my woodworking lathe. The only issue with using the large drill press as a vertical lathe for center drilling is that I am limited to 5/8" stock by the drill chuck, I am keeping an eye out for a 1" chuck with and adapter for it from whatever the chuck uses to a MT2 on the drill quill.




view of the two cross pins from the outside, the pins will be cut off nearly flush with the nose cone surface then filed down to match, after priming and sanding they will not even be noticeable.




I am thinking of painting this V2 like White Sands V2 round #43.

If nobody was paying attention earlier I have decided to go ahead with the plan for the donut av-bay which will be fully documented in this thread. I am planning to cut the bulkheads for it tomorrow afternoon. One good thing about this design is that the ejection charges wont be very big, the drogue bay is only 2" tall and 4" in diameter, just large enough for a small drogue and nomex, and the forward main chute bay is the whole nose cone. Lots of stuff crammed into a dual deploy package less than 36" long.

 

[rharshberger]

Nose weight epoxied in, between the lead shot Loc included (4.3oz) and the 1.7oz recovery anchor thats almost 6ozs of non-removeable nose weight, should be good for almost any motor I want to fly in 38mm that will fit up to and including a 38/1080 motors. Blue tape is covering and securing a popsicle/craft stick that keeps the rubber band in tension and the recovery anchor pulled vertical in the nose cone. Due to the fact I used US Composites 635 3:1 epoxy for the nose weight the holes around the brass pins have to be taped over or the epoxy is thin enough that some wicks out.

 

[Red Phenix]

Nose weight epoxied in, between the lead shot Loc included (4.3oz) and the 1.7oz recovery anchor thats almost 6ozs of non-removeable nose weight, should be good for almost any motor I want to fly in 38mm that will fit up to and including a 38/1080 motors. Blue tape is covering and securing a popsicle/craft stick that keeps the rubber band in tension and the recovery anchor pulled vertical in the nose cone. Due to the fact I used US Composites 635 3:1 epoxy for the nose weight the holes around the brass pins have to be taped over or the epoxy is thin enough that some wicks out.View attachment 358884 View attachment 358885

This build continues to impress. Thanks. I was wondering if you could drill a hole through the the nosecone, through the nosecone anchor and glue an additional copper (?) rod into place. This would add an extra level of support for the attachment point that relies on more than the mechanical bond between n/c and epoxy.

Looking forward to the doughnut eBay build documentation.

 

[rharshberger]

This build continues to impress. Thanks. I was wondering if you could drill a hole through the the nosecone, through the nosecone anchor and glue an additional copper (?) rod into place. This would add an extra level of support for the attachment point that relies on more than the mechanical bond between n/c and epoxy.

Looking forward to the doughnut eBay build documentation.

I could drill some holes in the nose cone and put additional securement into the nose weight, but additional pins or screws really won't add much more security. I use brass as its tougher than copper as well as easy to file/sand. Brass wood screws work well for additional mechanical securement as well, they can be screwed through the side of the NC until flush then cut and filed to contour. The only thing the pins are really supporting is the plastic of the nose cone during the ejection event, under acceleration the forces are not nearly as violent. I have yet to have this system fail me (so far).

 

[rharshberger]

Well its Sunday afternoon and I was kinda bored so.....donut bay construction time!


First things first, mock it up, then mock it up again and check for fit...I knew with this design the drogue bay was going to be small so but the drogue chute will be small anyways so no issues there yet. One of the better parts is that due to the bays small size the ejection charge will also be small as will the charge well for it (.3cc's of BP aught to do the job, of course ground testing will confirm that).



Top down view of the mock up, in the final version the upper end of the motor tube will be plugged so that the upper bay can be pressurized by its ejection charge, if not for the bulkhead shown later the upper bays ejection charge would just vent out the motor tube.


donut bay dry fit, prior to cutting off all threads. Edges hardened with CA. The bay will have to be indexed to allow parts like the U-bolts to have proper clearance. I will most likely only use one quick link per bay if at all to attach the harness.



Top view of bay, showing the installed hardware (all threads have since been trimmed off), the well-nut (aka Rawl Nut) on the left forward side is the wire pass through for the altimeters, and the small hole on the left side in the shadowed area is the screw hole for the charge well mounting screw ( I will make the charge wells later).



Top and bottom bulkheads are identical.



Top view of the real estate (still no tube bulkhead installed in motor tube).


Idea of what interior space is available, on this bay quite a bit of space to work with. Still need to make saddles for the MMT to mount the altimeter and battery sleds to (a sled for each will go on opposite sides of the MMT). The stepped bulkheads are important for sealing purposes and the lower CR/Bulkhead (left side in picture below) will be glued to the MMT. I could do the same to the upper bulkhead and coupler but I like being able to totally remove the coupler and a bit of poster tack around the MMT will ensure that everything is sealed on the upper side.


Upper end MMT bulkhead installed, due to the fact that any motor as long or longer than a AT 38/720 will protrude into the bays motor tube it will act as a piston so the motor back up charge if used will need to be sized accordingly (its a 38mm tube less than 8" long basically). A good fillet will be built up around the forward end to make sure the bulkhead is good and strong, the bulkhead is 6mm baltic birch ply.


As I have time I will document the internal sleds and electronics mounting over the next week or so.

 

[rharshberger]

Did a bit more work tonight.

First off was cutting off the shoulder of the tailcone to 1" long and drilling a few "epoxy rivet holes" for attachement of the lower airframe. For those not familiar with epoxy rivets they are simply holes drilled through the plastic of the tailcone shoulder and thickened epoxy is pushed into them as the airframe is epoxied in place, it acts a mechanical lock on the plastic. The epoxy used was once again US Composites 150 3:1 with some milled FG added as a thickener. The upper centering ring was installed with epoxy around the outer edge and TBII between the CR ID and the MMT since its a paper to wood joint. The advantage to cutting down the shoulder to 1" long was weight savings and space, by doing so it took 22g off the rear of the rocket of which I used 8g of epoxy to attach the airframe and upper centering ring. The external fin fillets will offset most of the weight loss, but its still 22g less at the rear than would have been there.

The other advantage was that by cutting off the shoulder, I also gained an about 1.5" additional space in the rear payload bay.



Donut Av-Bay with lower bulkhead permanently attached to the central motor tube, the upper bulkhead/CR will be permanently attached to the coupler, so that the bay will come apart in two pieces ( I may just leave the upper bulkhead and coupler as separate pieces too).

 

[Tim51]

Great build - I'm not a big fan of the V2 external shape but love the elegant compactness of the innards you're building

 

[rharshberger]

Thanks Tim51, some additional payload bay space could be gained by moving the donut bay bulkheads/CR's inside the coupler and using a Eggtimer Quark, almost creating a pancake bay. The length of the coupler was a compromise to give sufficient support to the airframes and to save internal space. Doing this build again I could gain additional space by moving the upper airframe CR from the top of the tailcone to on top of the fin tabs, it might gain another inch or so.

Eventually I plan to add the 5.38" and 7" V2's to my fleet from Loc.

 

[rharshberger]

Did a little more work on the V2 tonight.

Added 2 wraps of 5oz Fiberglass cloth to the top inch of each part of the airframe. The FG is because this rocket will be using shear pins on upper and lower airframe bay to coupler joints. The two sections of airframe were mounted in my wood working lathe and the first inch of each airframe was turned down (a process that's kind of a pain). The light colored spots in the airframe (or white in some cases) are not dry/resin starved areas, the airframe is an older (I think) Loc airframe and the glassine is over a thick white section of paper, after the glassine was removed and the diameter turned down the epoxy was allowed to soak into the airframe tube prior to application of the cloth, two wraps was just about perfect to match the section shoulder of the full diameter section. Once the wraps have fully cured, the fuzzies will be sanded of, the excess FG was trimmed when the epoxy cloth matrix reached the "leather stage", it makes trimming the excess easy and no mess. Wait too long to trim and it requires a lot more work, too early and things are still messy.

Next step will be the addition of the brass shear pin plates on the donut av-bay, a sled, electronics, external fin fillets and primer, as well as Acme Conformal Rail Guides (buttons wont work very well in this rocket due to the donut bay.

 

[Tim51]

Did a little more work on the V2 tonight.

Added 2 wraps of 5oz Fiberglass cloth to the top inch of each part of the airframe. The FG is because this rocket will be using shear pins on upper and lower airframe bay to coupler joints. The two sections of airframe were mounted in my wood working lathe and the first inch of each airframe was turned down (a process that's kind of a pain). The light colored spots in the airframe (or white in some cases) are not dry/resin starved areas, the airframe is an older (I think) Loc airframe and the glassine is over a thick white section of paper, after the glassine was removed and the diameter turned down the epoxy was allowed to soak into the airframe tube prior to application of the cloth, two wraps was just about perfect to match the section shoulder of the full diameter section. Once the wraps have fully cured, the fuzzies will be sanded of, the excess FG was trimmed when the epoxy cloth matrix reached the "leather stage", it makes trimming the excess easy and no mess. Wait too long to trim and it requires a lot more work, too early and things are still messy.

Next step will be the addition of the brass shear pin plates on the donut av-bay, a sled, electronics, external fin fillets and primer, as well as Acme Conformal Rail Guides (buttons wont work very well in this rocket due to the donut bay.



View attachment 359600 View attachment 359601 View attachment 359602

Do you put brass shear plates on both mating surfaces (ie on the bay and the airframe)?

 

[rharshberger]

Do you put brass shear plates on both mating surfaces (ie on the bay and the airframe)?

I do not, since the cardboard is fiberglass wrapped it acts as the reinforcement for the shear pins. I drill the holes in the airframe harden with CA then tap the airframe, the coupler gets the shear plates and the holes in them are slip fit.

 

[rharshberger]

Finally back to work on the V2 a bit more.

Added a chunk of leftover phenolic airframe material (or maybe motor mount tube, it was pretty thick) to the inside of the donut bay coupler to help stiffen the coupler and to allow easier attachment of shear plates and the upper rail button.


Shear plates made from .032 x .25" K&S Metals brass strip, attached with JB Weld.

Slots for shear plates, notch just below arrow goes all the way through coupler wall for hook end of shear plate.


Inside view of notch and coupler stiffener.


Shear plates epoxied in position and awaiting curing so the excess epoxy can be sanded flush.


Shear pin holes (currently 4 holes each side of bay for 2-56 nylon screw) and the larger 3/16" static port (other two static ports are 1/8"). Hopefully the lower payload bay will only need one shear pin and the upper will need most likely two, however I have the option of four each and can redrill and thread the holes for #4 nylon screws if need be (ground testing will of course verify whats really needed, but its easier to drill for the "just in case scenarios" now). Outer holes for shear pins are hardened with CA and threaded, the inner holes in the shear plates are clearance drilled ( a slip fit for the pin and maybe a bit more).

Internal view of shear pins in place.


External view of shear pins and indexing dowel drilled for rail button screw prior to dowel being sanded flush.

Indexing dowel and rail button mount sanded almost flush with airframe, the dowel was left just proud enough to allow the airframes to butt up without the rail button binding on them.

 

[SteveThatcher]

Finally back to work on the V2 a bit more.

I am looking forward to seeing it fly!

 

[Nytrunner]

Do both pins get installed per strip for flught?

 

[Glasspack]

Very cool build. My son built the same kit from LOC to attempt his Level 1 cert (Still in work).
Please pardon my ignorance but, Can you guys tell me what is meant by "Donut" Avionics bay.
is it because it uses a center tube in the Avionics Bay ? Thus a Donut for Bay bulkheads?

 

[rharshberger]

The donut part is the fact that the motor actually goes through the center of the bay, kinda like the hole in a donut. This rocket will handle a 38/1080 case if I want too.

 

[Tim51]

The donut part is the fact that the motor actually goes through the center of the bay, kinda like the hole in a donut. This rocket will handle a 38/1080 case if I want too.

Again, thanks for posting more on this fascinating build. I'm curious how you're planning to secure the Quantum in the doughnut bay, given the curvature..?

 

[Wallace]

https://lewiston.craigslist.org/bar/d/old-metal-lathe/6679291774.html

 

[Wallace]

Pretty sure that lathe is in your area. Price sounds very negotiable and it does have some tooling. One you have one you'll never understand how you got by without it.

 

[Wallace]

The fact that the tooling always ends up costing WAY more than the machine makes buying good old made in USA used stuff very attractive. Plus service parts are almost always available because they just never die.

 

[rharshberger]

Again, thanks for posting more on this fascinating build. I'm curious how you're planning to secure the Quantum in the doughnut bay, given the curvature..?

Securing the altimeter and battery will be just like any other bay except I will cut a saddle for the sled to be attached to, and the saddle will be permanently attached to the center tube. I should be doing that this week. The bay will also include a few parts from SMT Designs. There is quite a lot of room in this partivular bay.

 

[rharshberger]

Do both pins get installed per strip for flught?

Are you asking if all shear pins get installed for every flight? If so then, I will only be using as many as needed based on ground testing and later flight testing. Currently based on experienced guessing I plan on one pin on Drogue side and two pins on main side, the mass of the nose cone though does concern me and it may be necessary to use 4 on the main side or even upsize to #4 size shear pins.

 

[rharshberger]

I haven't forgotten about this build, but with Sodblaster and the recovery thereafter, plus working 63hrs per week, build time has been far and few between except for little quick projects (Estes Swift...).

Today is the first real work I have been able to do on the V2 in the last few weeks.


First up the sleds were cut and attached to the sled mounting "rings"/hexagons, using #4 threaded inserts and #4-40 screws. The grey sled with the RRC2 mounted to it is one of Steve Thatchers (SMT Designs) compact sleds. If I had the more space between the outer coupler and the sled I would have used some of this sled mounts for traditional bays. The blank sled next to the RRC2 is where the switch will go, and the battery will mount on the opposite side of the bay.



View of sled and CRs out of donut bay.




View of assembled bay from top, with charge wells (made earlier this evening).


View of donut bay from bottom.



View of donut bay from top.