LOC Precision 5.5" Phoenix Missile Build

Just for grins, I will be posting a few pics while this build progresses (like many of my build threads, it will be sporadic and slow). Rocket is the "bare bones" kit from LOC Precision, the BB-81, sport scale Phoenix missile with a 75mm motor mount.

After unboxing and inventorying components, I decided to add another centering ring (thicker fore ring for recovery harness connection) and will be adding a compartment to the nosecone. So picked out two appropriate pieces from my stash of parts that I will be modifying for use in this kit.



First order of business was a few simulations in Rocksim and FinSim. The larger M's will push this smallish rocket to Mach 1.5 so needed to supplement the 1/4" ply fins. Here you see the eight fins with a layer of carbon fiber and vacuum bagged.



Then onto the airframes. Two wraps of 6 oz fiberglass on the booster, payload and switch band.

Oh, and just to be complete, here is the .rkt file showing mods.

Very cool, I will be watching this thread closely. I've realized that I have the materials to make my own 5.5" Phoenix (tube, coupler, short LOC cone, and motor mounts.), but I will be going the scale route. Also planning a 54 + 4x 29mm cluster. Hoping to get the plywood and start making chips on Sunday.

What electronics are you planning for this rocket?

Dan, yeah, I was torn on trying to modify for scale. My problem was that with the supplied LOC av-bay and the need to have some length on the booster for the motors I have on hand, I opted to go with the added length--doing sims, it looks like it can take nearly everything I can throw at it without added nose weight. Regarding the scale look though, I made sure Barry shipped the short 5.5" nosecone, as I believe this makes a ton of difference in the final profile of the rocket. As of now, electronics planned are fairly straightforward with an RRC2mini and SL100 along with a BRB tracker (although will be making the nose cavity big enough to handle the BRB GPS unit which I haven't had time to play with as of yet).

Let me get this straight this rocket is not Scale? Did LOC make the rocket longer so that the builder would not have to add a ton of nose weight for stability issues? So would you say the rocket is semi-scale? How much longer is the rocket then scale?

Andrew

andrewlathrop87 said:

Let me get this straight this rocket is not Scale? Did LOC make the rocket longer so that the builder would not have to add a ton of nose weight for stability issues? So would you say the rocket is semi-scale? How much longer is the rocket then scale?

Andrew

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Semi-scale. This design is inherently unstable, and by unstable I mean "maneuverable." The fins are less than one body tube diameter in span, and there is a lot of weight in the tail. Lengthing the rocket, nose weight, and slightly increasing the fin size help with stability.

Dan is right. IIRC, if scale the length goes from 76" to 58" and worse, the fin semi-span is about 1" less. /Tim

patelldp said:

Semi-scale. This design is inherently unstable, and by unstable I mean "maneuverable." The fins are less than one body tube diameter in span, and there is a lot of weight in the tail. Lengthing the rocket, nose weight, and slightly increasing the fin size help with stability.

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Scale or not, one of my favorite looking rockets Tim, can't wait to see how it turns out.

Are you going to keep the fins edges fairly squared off like they have it in the photo? I ask because I know you've done a quite a bit of work/research regarding mach+ fin physics.

-S

Scott, I wouldn't really consider this a high performance rocket, so no special fin shaping. Will do a bevel on leading and trailing edges. Although I believe the fin spacing is too wide, I may just leave the inter-fin edges square to see if I can get a whistle out of them. /Tim

Scott Evil said:

Scale or not, one of my favorite looking rockets Tim, can't wait to see how it turns out.

Are you going to keep the fins edges fairly squared off like they have it in the photo? I ask because I know you've done a quite a bit of work/research regarding mach+ fin physics.

-S

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Finally found time to cut my extra parts and trim/shape fins. Just decided to go with a rounded leading/trailing edge on the fins.

Progress being made. Here are some pics from a couple days back...

All CRs, less the aft one epoxied in place. After hashing the edges of the CRs, I like to use some medium cure US Composites with milled FG applied at CR edges to get a good long soak. After that I will use T-88 with milled/chopped FG and a bit of chopped CF for the structural fillets. The picture below is only after the first step.



Then some work on the T-nuts both for motor retention and block inserts for the rail buttons. T-nuts shown inserted in place then a layer of 6 oz. glass on top to assure nothing ever moves as they will be inaccessible after assembly.



Also nosecone compartment being assembled in same manner as above using some scrap 54mm phenolic.



Finally the real pain! You can see these are some llooonnnggg fin slots (pic is looking down 42" booster frame). Since they were already cut quite a bit of epoxy puddled up into the slot edges, so that and the two layers of 6 oz. glass made it pretty tough to open up with my Dremel. As you can see by the pink marker lines, I still have to open the slots up some as the CF layer on the fins added a couple hundredths to the width of the fins.

Motor mount is now installed in the booster. But before I get to installing the fins, I wanted to dry fit and verify the motor retainer. Usually not a big deal, but I am expecting to fly this rocket on 54mm motors a third of the time, thus need a decent adapter. This one I picked up some time ago. IIRC, old Rocketman stock when he used to carry a full kit line. Not too much effort in putting it together. Extremely solid.



Aft CR in place with retainer for typical 75mm motor.



Then retainer in second configuration for 54mm motor and adapter.

And, just for good measure, cut out and verified rail button locations. A couple builds back, I forgot to do this until after finishing was complete -- UGH! So paranoid now.

dixontj93060 said:

Motor mount is now installed in the booster. But before I get to installing the fins, I wanted to dry fit and verify the motor retainer. Usually not a big deal, but I am expecting to fly this rocket on 54mm motors a third of the time, thus need a decent adapter. This one I picked up some time ago. IIRC, old Rocketman stock when he used to carry a full kit line. Not too much effort in putting it together. Extremely solid.

View attachment 91523

Aft CR in place with retainer for typical 75mm motor.

View attachment 91524

Then retainer in second configuration for 54mm motor and adapter.

View attachment 91525

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Old school retention. I like it. I have not seen too many people use clips to hold in and adapter like that. What
Type of clips are those?

cwbullet said:

Old school retention. I like it. I have not seen too many people use clips to hold in and adapter like that. What
Type of clips are those?

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Big honkin' ones -- no really, I bought a variety of three sizes from McMaster-Carr probably five years back. This is the largest size I bought and they are nice and thick (i.e., strong). I believe they are #9434T16 found here. But yes, it seems appropriate for a cardboard tube scale missile rocket. Might not be able to see it but there are indentations/grooves to hold the inverted clip in the bottom of the adapter.

Have the aft fins tacked in. Given a paper airframe, I use a combination of Titebond II at a couple spots of 5-minute epoxy. This allows me to get everything tacked in ~45 minutes, but still not completely set (or minimal hold with the 5-minute) so that if I have one out of alignment I can just pop it off, sand the root edge and re-install. In this case, as is normal for me (I'm horrible at eye alignment), I had one fin off a degree or two. After fixing, I went on to internal fillets. On this rocket, the aft fins (more exposed to recovery knocks) will have my typical beefy internal fillets shown below (dowel underneath the T-88 epoxy/strengthener mix). Because of the length and inaccessibility of the forward fins, their internal fillets will be injected.

Internal and external fillets on aft fins complete. Rear CR now epoxied in place and curing. Rear fillet on CR will be added later. Along with an 5.5" inner ring to support the 1.25" of airframe that extends to the rear (to reduce impact risk).

Halfway through tacking the fore fins.

The Phoenix was the last Estes rocket I flew 22 years ago. It took me 20 more years before I was born again. The Phoenix is on my "to do" list. Great upscale!

Looks great Tim, Looking forward to a MWPX maiden?

Jason, yes, MWPX. Beginning to take shape now with all fins tacked in. Still much work to do, but liking the direction here.

Up is always a good direction


Adrian

A couple more specifics and to hold off any inquiries as to why the fore fins will take a while... As mentioned earlier, due to their length and position in the airframe, I am injected internal fillets on these. Before doing so, I am doing some narrow fillets with a System Three Quick Cure-microballoon mix for the sole purpose of filling gaps between the fin surface and slots. I believe I sealed the fins well with the epoxy/Titebond II application on the root edge and edge of each CR, but you always get a bit of seepage when doing internal fillets, thus, to guard against any dripping, the gap filling fillets. You can see the contrast below between the smaller and uneven white fillets and the normal aerodynamic external fillets on the bottom done with a Bob Smith medium cure-milled FG mix (wider/yellow). This will be the second step for the fore fillets after injection. Then the whole thing will have one layer of tip-to-tip FG.

Now on to injected fillets. Normally I would just skip over this step, but there was a thread a little while back where the poster complained about how onerous the process was. I'm not a real fan of this technique and always attempt to get access to internal fillets via either end, but when needed, I do use it, and after stubbing my toe a time or two, I have it down to a fairly painless process. The preamble to this post is: 1) make sure your fins fit fairly snuggly against the CR's and the root edge is flat, 2) whatever adhesive you use, make sure it is slathered on the root edge and each fin end, aft and fore, liberally with fillers so that few, if any gaps exist, 3) to guard against any small seepage do the preliminary gap-filling fillets shown in post the previous post.

Gather your materials... Besides a syringe, there are a couple of key items here. Use low viscosity epoxy like U.S. Composites or West. I have found that about 1 gram per inch is just about the right amount for internal fillets. Crazy Jim has shown doing this procedure with chopped carbon. I have never been able to get this to work (same for chopped FG) so I just use milled (1/32") FG and fill the epoxy until I get a runny slurry. The other key I have found is to have "crisp" holes. Whatever airframe material I use I put a drop of CA and a spritz of CA hardener in each hole and re-drill until there are no burrs/fibers in an FG airframe or scraps in a phenolic or paper (as in this build).



Make sure your airframe is exactly horizontal. Again critical.



Don't skimp on holes (I have four spaced across the 20" root edge). More importantly, make them big enough. I mostly messed up when I started using this method by making my holes too small and too close to the fins. This combo tends to make it easy to plug the holes when you inject the epoxy and then it backs up on you. I now always make them nice and big so I can get the syringe fully in the hole with ease. I also pull the holes away from the fin so the epoxy drops vertically into the valley of the fin and airframe (note how crisp the holes are after CA application and re-drilling).



After that inject the epoxy slurry freely (again with about 1 gram per linear inch of root edge). After injection then mix up some 5 minute epoxy with a very healthy amount of microspheres. This thick mixture is then used to plug the holes in the airframe. Push it in the hole with an applicator (popsicle stick). It will probably take two applications in succession as the 5-minute epoxy begins to set. Wipe all overage of 5-minute epoxy off with alcohol. You probably will still have some cupping/weeping as the epoxy sets in the holes. Don't worry about it as the next step takes care of it.

Final step is to mix some mid-cure epoxy with some filler for fillets or just some milled FG. I use either Bob Smith mid-cure or System Three T-88. Both tend to be high viscosity and will set fairly quickly and run only minimally. Use this to make your external/aesthetic/aerodynamic fillet shape. When making these fillets, simply use your applicator to "inch up" and fill in the cupped injection fillet "divots". This method is much better than having the holes close to the fin while you try to apply an external fillet as the holes inside the fillet area will result in uneven fillets.

OK, finally finished with internal and external fillets. I have done a little work on the av-bay in the mean time, but no pics to show yet. Next step for booster will be a veil layer.

I have been following your build, it looks like it is shaping up really nice. Loc makes some really nice platforms to build from, great work.

DRAGON64 said:

I have been following your build, it looks like it is shaping up really nice. Loc makes some really nice platforms to build from, great work.

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Yes, I have to agree. Last two direct HPR kit purchases have been the LOC Blue Tube special resulting in my Axe To Grind and this "bare bones" deal. Both super values for what you receive!

I sure wish I took advantage of the BlueTube special they had ,cause you all know I loves my B Tube !

Your rocket/missile is shaping up very nicely ,and as you know ,I also loves my missiles ,so this one strikes a chord with me.

Paul T

sodmeister said:

I sure wish I took advantage of the BlueTube special they had ,cause you all know I loves my B Tube !

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Paul, well you now have no excuse, because LOC still has the special on sale.

dixontj93060 said:

Paul, well you now have no excuse, because LOC still has the special on sale.

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Paul you NEED to get that special. I did and it's an awsome deal for the money. I may have to get me 1 or 2 more. Cant have too much BT! Sorry TJ:blush: Dont mean to clutter up your thread.